阅读说明：本技术 在激光雷达系统中操作的光学探测器的时变增益 (Time-varying gain of optical detector operating in laser radar system ) 是由 A·K·拉塞尔 J·G·拉沙佩勒 S·R·坎贝尔 J·M·艾兴霍尔兹 S·D·伽勒玛 T· 于 2018-03-27 设计创作，主要内容包括：为了在激光雷达系统中探测来自远程目标散射的光脉冲的光时降低误检的可能性,激光雷达系统中的接收器包括光探测器和脉冲探测电路,脉冲探测电路具有增益电路,该增益电路的增益量随时间变化。增益电路在低增益模式下操作时间段T1,以防止接收器在阈值时间段T1期间探测返回的光脉冲,其中时间段T1从光脉冲被发射时的时间t<Sub>0</Sub>开始。在阈值时间段T1结束时,增益电路在高增益模式下操作,以开始探测返回的光脉冲,直到后续光脉冲被发射。(To reduce the likelihood of false detections in a lidar system when detecting light from a light pulse scattered by a remote target, a receiver in the lidar system includes a light detector and a pulse detection circuit having a gain circuit whose gain amount varies with time. The gain circuit operates in the low gain mode for a time period T1 to prevent the receiver from detecting a returning light pulse during a threshold time period T1, where the time period T1 is from when the light pulse was transmittedTime t 0 And starting. At the end of the threshold time period T1, the gain circuit operates in a high gain mode to begin detecting a returning light pulse until a subsequent light pulse is emitted.)

1. A lidar system comprising:

a light source configured to emit a pulse of light; and

a receiver configured to detect light from the light pulses scattered by a remote target, the receiver comprising:

a light detector that detects an optical signal corresponding to the light; and

a light pulse detection circuit configured to convert the optical signal to an electrical signal and detect whether the converted electrical signal is indicative of the light pulse scattered by the remote target, the light pulse detection circuit comprising:

a gain circuit configured to amplify the converted electrical signal by a predetermined amount of amplification, the predetermined amount of amplification varying according to an amount of time elapsed since the optical pulse was emitted, an

A comparison circuit configured to compare the amplified electrical signal to a threshold amount to determine whether the amplified electrical signal is indicative of the light pulse scattered by the remote target.

2. The lidar system according to claim 1, wherein the gain circuit operates in a low gain mode with the predetermined amount of amplification below a threshold value for a threshold time period T1 since the light pulse was transmitted, and switches to a high gain mode with the predetermined amount of amplification equal to or above the threshold value for a threshold time period T2 after the threshold time period T1 has elapsed.

3. The lidar system of claim 2, wherein:

the light pulse is a first light pulse;

after a second threshold period of time has elapsed, the gain circuit switches back to the low gain mode; and is

The light source emits a second pulse of light.

4. The lidar system of claim 2, further comprising a controller configured to:

initializing a timer to identify a first threshold time period and a second threshold time period based on one of: determining that the light pulse has been emitted or that light from the light pulse has been detected; and

providing a control signal indicative of the predetermined amount of amplification to the gain circuit.

5. The lidar system according to claim 4, wherein the controller determines that the light pulse has been emitted in response to the controller providing a control signal to the light source to emit the light pulse.

6. The lidar system of claim 4, wherein, as the light pulse is transmitted, the controller determines that the light pulse has been transmitted and initializes the timer in response to receiving an indication from the light detector that light from the light pulse has been detected.

7. The lidar system according to claim 6, wherein the first threshold time period is dynamically adjusted based on one or more characteristics of the detected light.

8. The lidar system of claim 1, wherein the predetermined amount of amplification in the gain circuit increases relative to an amount of time that has elapsed since the optical pulse has been transmitted until a second threshold period of time has elapsed or a maximum predetermined gain is reached.

9. The lidar system of claim 1, further comprising:

a scanner configured to scan an observation field of the lidar system, including directing light pulses to different points within the observation field.

10. A method of dynamically changing gain in a lidar system, the method comprising:

emitting, by a light source in the lidar system, a light pulse;

detecting, by a receiver in the lidar system, light from the light pulse scattered by a remote target to identify a returned light pulse, including detecting an optical signal corresponding to the light;

converting, by a light pulse detection circuit in the lidar system, the optical signal to an electrical signal;

amplifying, by the optical pulse detection circuit, the electrical signal by a predetermined amount of amplification that varies as a function of an amount of time that has elapsed since the optical pulse was emitted, an

Comparing, by the light pulse detection circuit, the amplified electrical signal to a threshold amount to determine whether the amplified electrical signal is indicative of the light pulse scattered by the remote target.

11. The method of claim 10 wherein the optical pulse detection circuit operates in a low gain mode with the predetermined amount of amplification below a threshold for a threshold period of time T1 since the optical pulse was emitted, and switches to a high gain mode with the predetermined amount of amplification equal to or above the threshold for a threshold period of time T2 after the threshold period of time T1 has elapsed.

12. The method of claim 11, wherein:

the light pulse is a first light pulse;

after the second threshold period of time has elapsed, the optical pulse detection circuit switches back to the low gain mode; and is

The light source emits a second pulse of light.

13. The method of claim 11, further comprising:

initializing a timer to identify a first threshold time period and a second threshold time period based on one of: determining that the light pulse has been emitted or that light from the light pulse has been detected; and

providing a control signal indicative of the predetermined amount of amplification to the light pulse detection circuit.

14. The method of claim 13, further comprising: providing a control signal to the light source to emit the light pulse, wherein determining that the light pulse has been emitted comprises: determining that the light pulse has been emitted in response to providing the control signal to the light source to emit the light pulse.

15. The method of claim 13, wherein determining that the light pulse has been emitted and initializing the timer comprises: as the light pulse is transmitted, an indication is received from the receiver that light from the light pulse has been detected.

16. The method of claim 10, wherein the predetermined amplification amount is increased relative to an amount of time elapsed since the light pulse has been emitted until the second threshold period of time elapses or a maximum predetermined gain is reached.

17. The method of claim 10, further comprising:

scanning, by a scanner in the lidar system, an observation field of the lidar system, including directing light pulses to different points within the observation field to illuminate a field of view of the light source.

18. A controller in a lidar system, comprising:

one or more processors; and

a non-transitory computer-readable memory coupled to the one or more processors and storing instructions in the memory that, when executed by the one or more processors, cause the controller to:

providing a control signal to the light source to emit a pulse of light;

initializing a timer based on at least one of: determining that the light pulse has been emitted or that light from the light pulse has been detected; and

providing a control signal indicative of a predetermined amount of amplification to a light pulse detection circuit, the predetermined amount of amplification to be amplified by an electrical signal converted from an optical signal corresponding to light from the light pulse scattered by a remote target, wherein the predetermined amount of amplification is based on an amount of time that has elapsed since the light pulse was emitted.

19. The controller of claim 18, wherein:

for a threshold time period T1 since the light pulse was emitted, the instructions cause the controller to provide control signals to the light pulse detection circuit to operate in a low gain mode with the predetermined amount of amplification below a threshold; and

for a threshold time period T2 after the threshold time period T1 has elapsed, the instructions cause the controller to provide a control signal to the light pulse detection circuit to switch to a high gain mode with the predetermined amount of amplification equal to or above the threshold.

20. The controller of claim 19, wherein:

the light pulse is a first light pulse;

after a second threshold period of time has elapsed, the instructions cause the controller to provide a control signal to the light pulse detection circuit to switch back to the low gain mode and to provide a control signal to the light source to emit a second light pulse.

21. The controller of claim 18, wherein the instructions cause the controller to initialize a timer as the light pulse is emitted to determine an amount of time that has elapsed since the light pulse was emitted in response to receiving an indication from a light detector that light from the light pulse has been detected.

Technical Field

The present disclosure relates generally to lidar systems, and more particularly to varying the gain of light detectors in lidar systems to detect light pulses scattered by remote targets.

Background

The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.

Light detection and ranging (lidar) is a technique that can be used to measure distance to a remote target. Typically, a lidar system includes a light source and an optical receiver. The light source may be, for example, a laser that emits light having a particular operating wavelength. The operating wavelength of a lidar system may be in, for example, the infrared, visible, or ultraviolet portions of the electromagnetic spectrum. The light source emits light toward the target, which then scatters the light. Some of the scattered light is received back by the receiver. The system determines a distance to the target based on one or more characteristics associated with the returned light. For example, the system may determine the distance to the target based on the time of flight of the returned light pulse.

Disclosure of Invention

One example embodiment of the disclosed technology is a lidar system comprising: a light source configured to emit a pulse of light; and a receiver configured to detect light from the light pulses scattered by the remote target. The receiver includes: a photodetector that detects an optical signal corresponding to the light; and a light pulse detection circuit configured to convert the optical signal into an electrical signal and detect whether the converted electrical signal is indicative of a light pulse scattered by the remote target. The optical pulse detection circuit includes: a gain circuit configured to amplify the converted electric signal by a predetermined amplification amount that varies according to an amount of time that has elapsed since the optical pulse was emitted; and a comparison circuit configured to compare the amplified electrical signal to a threshold amount to determine whether the amplified electrical signal is indicative of a light pulse scattered by the remote target.

Another example embodiment of the presently disclosed technology is a method for dynamically changing gain in a laser radar system. The method comprises the following steps: emitting, by a light source in a lidar system, a light pulse; detecting, by a receiver in the lidar system, light from a light pulse scattered by a remote target to identify a returned light pulse, including detecting an optical signal corresponding to the light; and converting the optical signal into an electrical signal by an optical pulse detection circuit in the lidar system. The method further comprises the following steps: amplifying, by the optical pulse detection circuit, the electrical signal by a predetermined amplification amount that varies according to an amount of time that has elapsed since the optical pulse was emitted; and comparing, by the light pulse detection circuit, the amplified electrical signal to a threshold amount to determine whether the amplified electrical signal is indicative of a light pulse scattered by the remote target.

Yet another example embodiment of the disclosed technology is a controller in a lidar system. The controller includes: one or more processors; and a non-transitory computer readable memory coupled to the one or more processors and storing instructions thereon. The instructions, when executed by the one or more processors, cause the controller to: providing a control signal to the light source to emit a pulse of light; and initializing a timer to determine an amount of time that has elapsed since the light pulse was transmitted. The instructions also cause the controller to provide a control signal to the light pulse detection circuit indicative of a predetermined amount of amplification, amplify an electrical signal by the predetermined amount of amplification, the electrical signal converted from an optical signal corresponding to light from the light pulse scattered by the remote object, wherein the predetermined amount of amplification is based on an amount of time that has elapsed since the light pulse was emitted.

Drawings

FIG. 1 is a block diagram of an example light detection and ranging (lidar) system in which the techniques of the present disclosure may be implemented;

FIG. 2 illustrates in more detail several components that may operate in the system of FIG. 1;

FIG. 3 illustrates an example configuration of the assembly of FIG. 1 scanning a 360 degree field of view by rotating a window in an enclosure;

FIG. 4 illustrates another configuration of the assembly of FIG. 1 scanning a 360 degree field of view through a substantially transparent stationary housing;

FIG. 5 illustrates an example scan pattern that may be produced by the lidar system of FIG. 1 when identifying a target within an observation field;

FIG. 6 illustrates an example scan pattern that may be produced by the lidar system of FIG. 1 when multiple beams are used to identify a target within an observation field;

FIG. 7 schematically illustrates a field of view (FOV) of a light source and detector that may be operated in the lidar system of FIG. 1;

FIG. 8 illustrates an example configuration of the lidar system of FIG. 1, or another suitable lidar system, in which a laser is disposed at a location remote from a sensor assembly;

FIG. 9 illustrates an example vehicle in which the lidar system of FIG. 1 may operate;

FIG. 10 shows an example InGaAs avalanche photodiode that may be operated in the lidar system of FIG. 1;

FIG. 11 illustrates an example photodiode coupled to a pulse detection circuit, which may operate in the lidar system of FIG. 1;

FIG. 12 illustrates an example receiver configured to vary gain over time, which may operate in the lidar system of FIG. 1;

FIG. 13 shows an example pulse timing diagram from which the receiver of FIG. 12 can process return pulses; and

FIG. 14 shows a flow diagram of an example method for dynamically adjusting gain in a laser radar system.

Detailed Description

SUMMARY

In general, a receiver in a lidar system varies an amount of gain used to amplify a received optical signal based on an amount of time that has elapsed since a light source emitted a light pulse. In one example embodiment, the receiver includes a photodetector (e.g., an Avalanche Photo Diode (APD)) and a pulse detection circuit. The light detector converts the optical signal to an electrical signal, and the pulse detection circuit amplifies the electrical signal and compares the amplified electrical signal to a threshold voltage to determine whether the optical signal is indicative of a return light pulse scattered by the remote target.

One technique includes operating the pulse detection circuit in a low gain mode (e.g., having a gain below a threshold level) for a time period T1 after the light source emits the light pulse. After the end of the time period T1, the gain circuit in the pulse detection circuit switches to a high gain mode (e.g., having a gain at or above a threshold level) to amplify the received signal for a time period T2, which time period T2 begins after the end of T1 and ends when the second light pulse is transmitted. When the light source emits the second light pulse, the gain circuit switches back to the low gain mode for a time period T1 after the light source emits the second light pulse. By operating in the low gain mode during the time period T1 after the light pulse is transmitted, the receiver reduces the likelihood of detecting noise during the time period T1 immediately after the light pulse is transmitted. For example, the time period T1 may occur when a returned pulse is received too early from a distance exceeding a minimum distance (e.g., 1 meter). In addition, a low gain may be applied to return pulses scattered by the remote target at close range to prevent saturation of the light detector. Furthermore, switching from a low gain mode to a high gain mode and then back again minimizes recovery time and reduces the minimum distance detectable.

In other embodiments, the gain circuit may gradually increase the gain over time from when the optical pulses are transmitted. For example, the gain may increase linearly from when the first light pulse is transmitted until the second light pulse is transmitted. In other embodiments, the gain circuit may vary the gain over time in any other suitable manner.

In some embodiments, the pulse detection circuit receives a signal from the controller when the controller provides a control signal or trigger signal to the light source to emit a pulse of light. In this way, the pulse detection circuit receives the time t when the optical pulse is transmitted₀Is indicated. In other embodiments, the controller receives trigger pulses or edges from the light source, wherein each pulse or edge corresponds to a light pulse emitted by the light source. The controller then provides the received trigger pulse or edge to the pulse detection circuit. In other embodiments, the light detector detects light from the light pulse as the light pulse is emitted. As one example, the light detector may detect a portion of the transmitted light pulse scattered from within the lidar system housing. The detected light pulses, when emitted, may be referred to as "optical" t₀. The timer for measuring the first and second time periods T1 and T2 may be at the power T₀Optical t₀Or at electric t₀Or optical t₀A specific time interval thereafter is initialized.

Referring next to fig. 1-4, consider an example lidar system that can implement these techniques, followed by a discussion of techniques that the lidar system can implement to scan an observation field and generate individual pixels (fig. 5-7). Next, an example embodiment in a vehicle is discussed with reference to fig. 8 and 9. Then, an example photodetector and an example pulse detection circuit are discussed with reference to fig. 10 and 11.

Overview of the System

Fig. 1 shows an example laser detection and ranging (lidar) system 100. Laser radar system 100 may be referred to as a laser ranging system, a laser radio detection system (laser radar system), a LIDAR system, a laser radar sensor, or a laser detection and ranging (LADAR or LADAR) system. Lidar system 100 may include a light source 110, a mirror 115, a scanner 120, a receiver 140, and a controller 150. The light source 110 may be, for example, a laser that emits light having a particular operating wavelength in the infrared, visible, or ultraviolet portions of the electromagnetic spectrum. As a more specific example, the light source 110 may include a laser operating at a wavelength between about 1.2 μm and 1.7 μm.

In operation, the light source 110 emits an output beam 125, which may be continuous wave, pulsed, or modulated in any suitable manner for a given application. Output beam 125 is directed in a forward direction toward remote target 130, and remote target 130 is located a distance D from laser radar system 100 and is at least partially contained within the field of view of system 100. For example, D may be between 1m and 1km, depending on the scenario and/or implementation of lidar system 100.

Once output beam 125 reaches forward-facing target 130, target 130 may scatter or reflect (in some cases) at least a portion of the light from output beam 125, and some of the scattered or reflected light may return to laser radar system 100. In the example of fig. 1, the scattered or reflected light is represented by an input beam 135, the input beam 135 passing through the scanner 120, and the scanner 120 may be referred to as a beam scanner, an optical scanner, or a laser scanner. The input beam 135 passes through the scanner 120 to the mirror 115, and the mirror 115 may be referred to as a fold mirror, a stack mirror, or a beam combiner. The mirror 115 in turn directs the input beam 135 towards a receiver 140. The input light beam 135 may contain only a relatively small portion of the light from the output light beam 125. For example, the average power, peak power, or pulse energy of the input beam 135 and the average power, peak power, or pulse of the output beam 125The energy ratio may be about 10^-1、10^-2、10^-3、10^-4、10^-5、10^-6、10^-7、10^-8、10^-9、10^-10、10^-11Or 10^-12. As another example, if the pulses of the output beam 125 have a pulse energy of 1 micro joule (μ J), the pulse energy of the corresponding pulses of the input beam 135 may be approximately 10 nanojoules (nJ), 1nJ, 100 picojoules (pJ), 10pJ, 1pJ, 100 femtojoules (fJ), 10fJ, 1fJ, 100 atrojoules (aJ), 10aJ, or 1 aJ.

Output beam 125 may be referred to as a laser beam, a light beam, an optical beam, an emitted beam, or a beam; and the input beam 135 may be referred to as a return beam, a received beam, a return light, a received light, an input light, a scattered light, or a reflected light. Scattered light, as used herein, may refer to light scattered or reflected by the target 130. The input light beam 135 may include: light from the output beam 125, which is scattered by the target 130; light from the output beam 125, which is reflected by the target 130; or a combination of scattered and reflected light from the target 130.

For example, the operating wavelength of lidar system 100 may be in the infrared, visible, or ultraviolet portions of the electromagnetic spectrum. The sun also produces light in these wavelength ranges, and thus sunlight may act as background noise that obscures signal light detected by lidar system 100. Such solar background noise may cause false positive detections or may otherwise corrupt measurements of lidar system 100, particularly when receiver 140 includes a Single Photon Avalanche Diode (SPAD) detector (which may be highly sensitive).

In general, sunlight that passes through the earth's atmosphere and reaches a ground-based lidar system (e.g., system 100) may establish an optical background noise floor for the system. Therefore, in order to be able to detect the signal from lidar system 100, the signal must be above the background noise floor. The signal-to-noise ratio (SNR) of lidar system 100 may generally be increased by increasing the power level of output beam 125, but in some cases it may be desirable to keep the power level of output beam 125 at a relatively low level. For example, increasing the transmission power level of output beam 125 may result in laser radar system 100 being unsafe to the human eye.

In some embodiments, lidar system 100 operates at one or more wavelengths between about 1400nm and about 1600 nm. For example, the light source 110 may generate light at about 1550 nm.

In some embodiments, lidar system 100 operates at frequencies where atmospheric absorption is relatively low. For example, laser radar system 100 may operate in a wavelength range of approximately 980nm to 1110nm or 1165nm to 1400 nm.

In other embodiments, lidar system 100 operates at frequencies where the atmosphere absorbs high. For example, lidar system 100 may operate in a wavelength range of approximately 930nm to 980nm, 1100nm to 1165nm, or 1400nm to 1460 nm.

According to some embodiments, lidar system 100 may include an eye-safe laser, or lidar system 100 may be classified as an eye-safe laser system or an eye-safe laser product. An eye-safe laser, eye-safe laser system, or eye-safe laser product may refer to a system that emits a wavelength, average power, peak intensity, pulse energy, beam size, beam divergence, exposure time, or scanned output beam such that the light emitted from the laser is less likely or less likely to cause damage to the human eye. For example, light source 110 or lidar system 100 may be classified as a class 1 laser product (according to the regulations of the International Electrotechnical Commission (IEC)60825-1 standard) or a class I laser product (according to the regulations of section 21 of federal regulations (CFR) 1040.10) that is safe under all normal conditions of use. In some embodiments, the light source 110 may be classified as a human eye safe laser product (e.g., having a class 1 or class I classification) configured to operate at any suitable wavelength between about 1400nm and about 2100 nm. In some embodiments, light source 110 may include a laser having an operating wavelength between about 1400nm and about 1600nm, and lidar system 100 may operate in an eye-safe manner. In some embodiments, light source 110 or lidar system 100 may be an eye-safe laser product that includes a scanning laser operating at a wavelength between about 1530nm and about 1560 nm. In some embodiments, lidar system 100 may be a class 1 or class I laser product that includes a fiber laser or solid state laser operating at a wavelength between about 1400nm and about 1600 nm.

The receiver 140 may receive or detect photons from the input beam 135 and generate one or more representative signals. For example, the receiver 140 may generate an output electrical signal 145 representative of the input optical beam 135. The receiver may send the electrical signal 145 to the controller 150. According to this embodiment, controller 150 may include one or more processors, Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), and/or other suitable circuitry configured to analyze one or more characteristics of electrical signal 145 to determine one or more characteristics of target 130, such as its distance from lidar system 100 in the transmit direction. More particularly, the controller 150 may analyze the time of flight of the light beam 125 emitted by the light source 110 or phase modulate the light beam 125 emitted by the light source 110. If lidar system 100 measures a time of flight of T (e.g., T represents a round-trip time of flight for a transmitted light pulse to travel from lidar system 100 to target 130 and back to lidar system 100), a distance D from target 130 to lidar system 100 may be represented as D ═ c · T/2, where c is the speed of light (about 3.0 × 10)⁸m/s)。

As a more specific example, if laser radar system 100 measures a time of flight of T300 ns, laser radar system 100 may determine that the distance from target 130 to laser radar system 100 is approximately D45.0 m. As another example, laser radar system 100 measures a time of flight T of 1.33 μ s, and determines that the distance from target 130 to laser radar system 100 is approximately D of 199.5 m. The distance D from lidar system 100 to target 130 may be referred to as the distance, depth, or (perceived) distance of target 130. The speed of light c as used herein refers to the speed of light in any suitable medium, such as air, water or vacuum. The speed of light is about 2.9979X 10 in vacuum⁸m/s, and a light velocity of about 2.9970X 10 in air (having a refractive index of about 1.0003)⁸m/s。

Target 130 may be located at a distance D from lidar system 100 that is less than or equal to a maximum range R of lidar system 100_MAX. Maximum range R of the laser radar system 100_MAXWhich may also be referred to as a maximum range, may correspond to a maximum range at which lidar system 100 is configured to sense or identify a target present in an observation field of lidar system 100. The maximum range of lidar system 100 may be any suitable distance, for example 25m, 50m, 100m, 200m, 500m, or 1 km. As a specific example, a lidar system with a maximum range of 200m may be configured to sense or identify various targets 130 located at a distance of up to 200m from the lidar system. For a maximum range of 200m (R)_MAX200m) with a time of flight corresponding to the maximum range of about

In some embodiments, light source 110, scanner 120, and receiver 140 may be packaged together in a single enclosure 155, and enclosure 155 may be a box, case, or housing that houses or contains all or part of lidar system 100. Housing 155 includes a window 157 through which beams 125 and 135 pass. In an example embodiment, lidar system enclosure 155 contains light source 110, overlap mirror 115, scanner 120, and receiver 140 of lidar system 100. Controller 150 may be located within the same enclosure 155 as components 110, 120, and 140, or controller 150 may be located remotely from the enclosure.

Further, in some embodiments, enclosure 155 includes a plurality of lidar sensors, each sensor including a respective scanner and receiver. According to a particular embodiment, each of the plurality of sensors may comprise a separate light source or a common light source. According to this embodiment, the plurality of sensors may be configured to cover non-overlapping adjacent observation fields or partially overlapping observation fields.

Enclosure 155 may be an air-tight or water-tight structure that prevents water vapor, liquid water, dirt, dust, or other contaminants from entering enclosure 155. The enclosure 155 may be filled with a dry or inert gas, such as dry air, nitrogen, or argon. The enclosure 155 may include one or more electrical connections for communicating electrical power or signals to and from the enclosure.

The window 157 may be made of any suitable substrate material, such as glass or plastic (e.g., polycarbonate, acrylic, cyclic olefin polymer, or cyclic olefin copolymer). The window 157 may include an inner surface (surface a) and an outer surface (surface B), and either surface a or surface B may include a dielectric coating having a particular reflectivity value at a particular wavelength. The dielectric coating (which may be referred to as a thin film coating, interference coating, or coating) may include a dielectric material (e.g., SiO) having a particular thickness (e.g., a thickness of less than 1 μm) and a particular refractive index₂、TiO₂、Al₂O₃、Ta₂O₅、MgF₂、LaF₃Or AlF₃) One or more thin film layers of (a). The dielectric coating can be deposited onto surface a or surface B of window 157 using any suitable deposition technique (e.g., sputter deposition or electron beam deposition).

The dielectric coating may have a high reflectivity at a particular wavelength or may have a low reflectivity at a particular wavelength. The High Reflectivity (HR) dielectric coating can have any suitable reflectivity value (e.g., reflectivity greater than or equal to 80%, 90%, 95%, or 99%) at any suitable wavelength or combination of wavelengths. The low-reflectivity dielectric coating, which may be referred to as an anti-reflection (AR) coating, may have any suitable reflectivity value (e.g., a reflectivity of less than or equal to 5%, 2%, 1%, 0.5%, or 0.2%) at any suitable wavelength or combination of wavelengths. In particular embodiments, the dielectric coating may be a dichroic coating having a particular combination of high or low reflectivity values at particular wavelengths. For example, the reflectance of the dichroic coating at approximately 1550-.

In some embodiments, surface a or surface B may have a dielectric coating that is anti-reflective at the operating wavelength of the one or more light sources 110 contained within the housing 155. The AR coatings on surfaces a and B may increase the amount of light transmitted through window 157 at the operating wavelength of light source 110. Additionally, at the operating wavelength of light source 110, the AR coating may reduce the amount of incident light from output beam 125 that is reflected back to enclosure 155 by window 157. In an example embodiment, surface a and surface B may each have an AR coating with a reflectivity of less than 0.5% at the operating wavelength of light source 110. As one example, if the operating wavelength of light source 110 is about 1550nm, surface a and surface B may each have an AR coating with a reflectivity of less than 0.5% at wavelengths of about 1547nm to about 1553 nm. In another embodiment, surface a and surface B may each have an AR coating with a reflectivity of less than 1% at the operating wavelength of light source 110. For example, if housing 155 encloses two sensor heads with respective light sources, the first light source emitting pulses at a wavelength of about 1535nm and the second light source emitting pulses at a wavelength of about 1540nm, surface a and surface B may each have an AR coating with a reflectivity of less than 1% at a wavelength of about 1530nm to about 1545 nm.

Window 157 can have an optical transparency that is greater than any suitable value of one or more wavelengths of one or more light sources 110 (contained within enclosure 155). As one example, the window 157 may have an optical transmittance of greater than or equal to 70%, 80%, 90%, 95%, or 99% at the wavelength of the light source 110. In one example embodiment, the window 157 may transmit greater than or equal to 95% of light at the operating wavelength of the light source 110. In another embodiment, the window 157 transmits greater than or equal to 90% of light at the operating wavelength of the light source enclosed within the enclosure 155.

Surface a or surface B may have a dichroic coating that is anti-reflective at one or more operating wavelengths of one or more light sources 110 and highly reflective at wavelengths away from the one or more operating wavelengths. For example, for an operating wavelength of light source 110, surface a may have an AR coating and surface B may have a dichroic coating that is AR at the light source operating wavelength and HR for wavelengths away from the operating wavelength. For wavelengths away from the operating wavelength of the light source, the HR coating may prevent most of the incident light of unwanted wavelengths from being transmitted through the window 117. In one embodiment, if light source 110 emits an optical pulse having a wavelength of about 1550nm, surface a may have an AR coating with a reflectivity of less than or equal to 0.5% at a wavelength of about 1546nm to about 1554 nm. In addition, surface B may have a dichroic coating that is AR at about 1546-1554nm and HR (e.g., greater than or equal to 90% reflectance) at about 800-1500nm and about 1580-1700 nm.

Surface B of window 157 may include an oleophobic, hydrophobic, or hydrophilic coating. The oleophobic coating (or lipophobic coating) can drain oil (e.g., fingerprint oil or other non-polar material) from the outer surface (surface B) of the window 157. The hydrophobic coating may drain water from the outer surface. For example, surface B may be coated with a material that is both oleophobic and hydrophobic. The hydrophilic coating attracts water, tending to wet it, and forming a film on the hydrophilic surface (rather than forming water droplets like those that occur on hydrophobic surfaces). If the surface B has a hydrophilic coating, water (e.g. rain) falling on the surface B may form a film on the surface. A surface film of water may cause less distortion, deflection, or obstruction of the output beam 125 than a surface with a non-hydrophilic or hydrophobic coating.

With continued reference to fig. 1, the optical source 110 may include a pulsed laser configured to generate or emit optical pulses having a pulse duration. In an exemplary embodiment, the pulse duration or pulse width of the pulsed laser is about 10 picoseconds (ps) to 100 nanoseconds (ns). In another embodiment, light source 110 is a pulsed laser that produces pulses having a pulse duration of about 1-4 ns. In yet another embodiment, the light source 110 is a pulsed laser that generates pulses at a pulse repetition rate of about 100kHz to 5MHz or a pulse period (e.g., time between successive pulses) of about 200ns to 10 μ s. According to this embodiment, the light source 110 may have a substantially constant or variable pulse repetition frequency. As one example, the light source 110 may be a pulsed laser that generates pulses at a substantially constant pulse repetition frequency (corresponding to a pulse period of about 1.56 μ β) of about 640kHz (e.g., 640,000 pulses per second). As another example, the pulse repetition frequency of the light source 110 may vary between about 500kHz to 3 MHz. As used herein, light pulses may be referred to as optical pulses, pulsed light or pulses, and the pulse repetition frequency may be referred to as the pulse rate.

In general, the output beam 125 may have any suitable average optical power, and the output beam 125 may include optical pulses having any suitable pulse energy or peak optical power. Some examples of average power of output beam 125 include approximations of 1mW, 10mW, 100mW, 1W, and 10W. Example values of the pulse energy of output beam 125 include approximate values of 0.1 μ J, 1 μ J, 10 μ J, 100 μ J, and 1 mJ. Examples of peak power values of the pulses contained in the output beam 125 are approximations of 10W, 100W, 1kW, 5kW, 10 kW. The peak power of an exemplary optical pulse having a duration of 1ns and a pulse energy of 1 muj is about 1 kW. If the pulse repetition frequency is 500kHz, the average power of the output beam 125 with 1 uJ pulses is about 0.5W in this example.

The light source 110 may include a laser diode, such as a fabry-perot laser diode, a quantum well laser, a Distributed Bragg Reflector (DBR) laser, a Distributed Feedback (DFB) laser, or a Vertical Cavity Surface Emitting Laser (VCSEL). The laser diodes operating in the light source 110 may be aluminum gallium arsenide (AlGaAs) laser diodes, indium gallium arsenide (InGaAs) laser diodes, or indium gallium arsenide phosphide (InGaAsP) laser diodes, or any other suitable diodes. In some embodiments, the light source 110 comprises a pulsed laser diode with a peak emission wavelength of about 1400-1600 nm. In addition, the light source 110 may include a laser diode that is current modulated to generate optical pulses.

In some embodiments, the light source 110 comprises a pulsed laser diode followed by one or more optical amplification stages. For example, the light source 110 may be a fiber laser module comprising a current modulated laser diode with a peak wavelength of about 1550nm followed by a single or multi-stage Erbium Doped Fiber Amplifier (EDFA) or erbium ytterbium co-doped fiber amplifier (EYDFA). As another example, the optical source 110 may comprise a Continuous Wave (CW) or quasi-CW laser diode followed by an external optical modulator (e.g., an electro-optic modulator), and the output of the modulator may be fed to an optical amplifier. In other embodiments, the light source 110 may include a laser diode that produces optical pulses that are not amplified by an optical amplifier. As one example, a laser diode (which may be referred to as a direct emitter or direct emitter laser diode) may emit an optical pulse that forms an output beam 125 directed from the laser radar system 100 in the direction of emission. In other embodiments, the light source 110 may include a pulsed solid-state laser or a pulsed fiber laser.

In some embodiments, the output beam 125 emitted by the light source 110 can be a collimated optical beam having any suitable beam divergence, for example, a divergence of about 0.1 to 3.0 milliradians (mrads). Divergence of output beam 125 may refer to an angular measure of the increase in beam size (e.g., beam radius or beam diameter) as output beam 125 is moved away from light source 110 or laser radar system 100. Output beam 125 may have a substantially circular cross-section with a beam divergence characterized by a single divergence value. For example, at a distance of 100100 m from the lidar system, the beam diameter or spot size of the output beam 125, which has a circular cross-section and a divergence of 1mrad, is about 10 cm. In some embodiments, the output beam 125 may be an astigmatic beam, or may have a substantially elliptical cross-section and may be characterized by two divergence values. As one example, output beam 125 may have a fast axis and a slow axis, where the fast axis divergence is greater than the slow axis divergence. As another example, the output beam 125 can be an astigmatic beam having a fast axis divergence of 2mrad and a slow axis divergence of 0.5 mrad.

The output beam 125 emitted by the light source 110 may be unpolarized or randomly polarized, may have no explicit or fixed polarization (e.g., the polarization may vary over time), or may have a particular polarization (e.g., the output beam 125 may be linearly, elliptically, or circularly polarized). As one example, light source 110 may generate linearly polarized light, and lidar system 100 may include a quarter wave plate that converts the linearly polarized light to circularly polarized light. Lidar system 100 may emit circularly polarized light as output beam 125 and receive input beam 135, where input beam 135 may be substantially or at least partially circularly polarized in the same manner as output beam 125 (e.g., if output beam 125 is right-handed circularly polarized, input beam 135 may also be right-handed circularly polarized). The input beam 135 may pass through the same quarter wave plate (or a different quarter wave plate) such that the input beam 135 is converted to linearly polarized light that is orthogonally polarized (e.g., polarized at a right angle) relative to the linearly polarized light generated by the light source 110. As another example, lidar system 100 may employ polarization diversity detection, where two polarization components are detected separately. Output beam 125 may be linearly polarized and laser radar system 100 may split input beam 135 into two polarization components (e.g., s-polarized and p-polarized) that are detected by two photodiodes (e.g., a balanced photoreceiver including two photodiodes), respectively.

With continued reference to fig. 1, output beam 125 and input beam 135 may be substantially coaxial. In other words, output beam 125 and input beam 135 may at least partially overlap or share a common axis of propagation such that input beam 135 and output beam 125 travel along substantially the same optical path (although in opposite directions). As laser radar system 100 scans output beam 125 through the field of view, input beam 135 may follow output beam 125, thereby maintaining a coaxial relationship between the two beams.

Lidar system 100 may also include one or more optical components configured to condition, shape, filter, modify, direct, or direct output beam 125 and/or input beam 135. For example, laser radar system 100 may include one or more lenses, mirrors, filters (e.g., bandpass or interference filters), beam splitters, polarizers, polarizing beam splitters, waveplates (e.g., half-wave plates or quarter-wave plates), diffractive elements, or holographic elements. In some embodiments, lidar system 100 may include a telescope, one or more lenses, or one or more mirrors to expand, focus, or collimate output beam 125 to a desired beam diameter or divergence. As one example, lidar system 100 may include one or more lenses to focus input beam 135 onto an active region of receiver 140. As another example, laser radar system 100 may include one or more flat or curved mirrors (e.g., concave, convex, or parabolic) to direct or focus output beam 125 or input beam 135. For example, lidar system 100 may include an off-axis parabolic mirror to focus input beam 135 onto the active area of receiver 140. As shown in fig. 1, lidar system 100 may include a mirror 115, which may be a metal mirror or a dielectric mirror. The mirror 115 may be configured to pass the light beam 125 through the mirror 115. As one example, the mirror 115 may include a hole, slit, or aperture through which the output beam 125 passes. As another example, the mirror 115 may be configured such that at least 80% of the output beam 125 passes through the mirror 115 and at least 80% of the input beam 135 is reflected by the mirror 115. In some embodiments, mirror 115 may substantially co-axially align output beam 125 and input beam 135 such that the two beams travel along substantially the same optical path (in opposite directions).

In general, the scanner 120 directs the output beam 125 in one or more directions along the emission direction. For example, the scanner 120 can include one or more scanning mirrors and one or more actuators that drive the mirrors to rotate, tilt, pivot, or move the mirrors in an angular fashion about one or more axes. For example, a first mirror of the scanner may scan the output beam 125 in a first direction, and a second mirror may scan the output beam 125 in a second direction substantially orthogonal to the first direction. An example implementation of the scanner 120 is discussed in more detail below with reference to fig. 2.

The scanner 120 may be configured to scan the output beam 125 over a5 degree angular range, a 20 degree angular range, a 30 degree angular range, a 60 degree angular range, or any other suitable angular range. For example, the scanning mirror can be configured to periodically rotate over a 15 degree range, which causes the output beam 125 to scan over a 30 degree range (e.g., a scanning mirror rotation of Θ degrees causes the output beam 125 to perform an angular scan of 2 Θ degrees). The field of view (FOR) of lidar system 100 may refer to a region, area, or angular range over which lidar system 100 may be configured to scan or capture range information. Laser radar system 100 may be referred to as having a field of view with a 30 degree angle when laser radar system 100 scans output beam 125 over a 30 degree scan range. As another example, lidar system 100 with a scanning mirror that rotates over a 30 degree range may produce output beam 125 that scans over a 60 degree range (e.g., 60 degree FOR). In various embodiments, lidar system 100 may have a FOR of about 10 °, 20 °, 40 °, 60 °, 120 °, or any other suitable FOR. FOR may also be referred to as a scan area.

Scanner 120 may be configured to scan output beam 125 horizontally and vertically, and laser radar system 100 may have a particular FOR in the horizontal direction and another particular FOR in the vertical direction. FOR example, laser radar system 100 has a horizontal FOR of 10 ° to 120 °, and a vertical FOR of 2 ° to 45 °.

One or more of the scan mirrors of scanner 120 can be communicatively coupled to controller 150, and controller 150 can control the scan mirrors to direct output beam 125 in a desired direction, along a desired scan pattern, or in a desired firing direction. In general, the scan pattern may refer to a pattern or path along which the output beam 125 is directed, and may also be referred to as an optical scan pattern, an optical scan path, or a scan path. As one example, the scanner 120 may include two scanning mirrors configured to scan the output beam 125 within a 60 ° horizontal FOR and a 20 ° vertical FOR. The two scan mirrors can be controlled to follow a scan path that substantially covers 60 ° x 20 ° FOR. Lidar system 100 may utilize a scan path to generate a point cloud having pixels substantially covering 60 ° × 20 ° FOR. The pixels may be approximately uniformly distributed within 60 ° x 20 ° FOR. Alternatively, the pixels may have a certain non-uniform distribution (FOR example, the pixels may be distributed within all or part of 60 ° × 20 ° FOR, and the pixels may have a higher density in one or more certain regions of 60 ° × 20 ° FOR).

In operation, light source 110 may emit light pulses that are scanned by scanner 120 within the FOR of lidar system 100. Target 130 may scatter one or more of the transmitted pulses, and receiver 140 may detect at least a portion of the pulses of light scattered by target 130.

The receiver 140 may be referred to as (or may include) an optical receiver, an optical sensor, a detector, a photodetector, or an optical detector. In some embodiments, the receiver 140 receives or detects at least a portion of the input light beam 135 and generates an electrical signal corresponding to the input light beam 135. For example, if the input light beam 135 comprises optical pulses, the receiver 140 may generate current or voltage pulses corresponding to the optical pulses detected by the receiver 140. In an example embodiment, the receiver 140 includes one or more Avalanche Photodiodes (APDs) or one or more Single Photon Avalanche Diodes (SPADs). In another embodiment, the receiver 140 may include one or more PN photodiodes (e.g., a photodiode structure formed of a p-type semiconductor and an n-type semiconductor) or one or more PIN photodiodes (e.g., a photodiode structure formed of an undoped intrinsic semiconductor region located between a p-type region and an n-type region).

The receiver 140 may have an active region or avalanche multiplication region comprising silicon, germanium, or InGaAs. The active region of the receiver 140 may have any suitable dimensions, for example, a diameter or width of about 50-500 μm. Receiver 140 may include circuitry that performs signal amplification, sampling, filtering, signal conditioning, analog-to-digital conversion, time-to-digital conversion, pulse detection, threshold detection, rising edge detection, or falling edge detection. For example, receiver 140 may include a transimpedance amplifier that converts a received photocurrent (e.g., a current generated by an APD in response to a received optical signal) into a voltage signal. The receiver 140 may direct the voltage signal to a pulse detection circuit that generates an analog or digital output signal 145 that corresponds to one or more characteristics (e.g., rising edge, falling edge, amplitude, or duration) of the received optical pulse. For example, the pulse detection circuit may perform a time-to-digital conversion to produce the digital output signal 145. The receiver 140 may send the electrical output signal 145 to the controller 150 for processing or analysis, for example, to determine a time-of-flight value corresponding to the received optical pulse.

The controller 150 may be electrically coupled or communicatively coupled with one or more of the light source 110, the scanner 120, or the receiver 140. The controller 150 may receive electrical trigger pulses or edges from the light source 110, where each pulse or edge corresponds to an optical pulse emitted by the light source 110. The controller 150 may provide instructions, control signals, or trigger signals to the light source 110 indicating when the light source 110 should generate an optical pulse. For example, the controller 150 may send an electrical trigger signal comprising electrical pulses, wherein the light source 110 emits an optical pulse in response to each electrical pulse. Further, the controller 150 may cause the optical source 110 to adjust one or more of the frequency, period, duration, pulse energy, peak power, average power, or wavelength of the optical pulses generated by the optical source 110.

Controller 150 may determine a time-of-flight value for the optical pulse based on timing information associated with when the pulse was emitted by optical source 110 and when a portion of the pulse (e.g., input light beam 135) was detected or received by receiver 140. Controller 150 may include circuitry that performs signal amplification, sampling, filtering, signal conditioning, analog-to-digital conversion, time-to-digital conversion, pulse detection, threshold detection, rising edge detection, or falling edge detection.

As described above, lidar system 100 may be used to determine a range to one or more streamwise-emitting targets 130. By scanning lidar system 100 within an observation field, the system may be used to map ranges to multiple points within the observation field. Each of these depth mapped points may be referred to as a pixel or a voxel. A set of successively captured pixels (which may be referred to as a depth map, point cloud, or frame) may be presented as an image or may be analyzed to identify or detect objects or to determine the shape or distance of objects within a FOR. For example, the depth map may cover an observation field extending horizontally by 60 ° and vertically by 15 °, and the depth map may include a frame of 100 pixels horizontally by 2000 pixels vertically by 4-400 pixels vertically.

Lidar system 100 may be configured to repeatedly capture or generate a point cloud of an observation field at any suitable frame rate between about 0.1 Frames Per Second (FPS) and about 1,000 FPS. For example, laser radar system 100 may generate point clouds at a frame rate of approximately 0.1FPS, 0.5FPS, 1FPS, 2FPS, 5FPS, 10FPS, 20FPS, 100FPS, 500FPS, or 1,000 FPS. In an example embodiment, lidar system 100 is configured at 5 x 10⁵The rate of pulses/second generates optical pulses (e.g., the system can determine a 500,000 pixel distance per second) and scans a frame of 1000 x 50 pixels (e.g., 50,000 pixels/frame), which corresponds to a point cloud frame rate of 10 frames per second (e.g., 10 point clouds per second). According to this embodiment, the point cloud frame rate may be substantially fixed or may be dynamically adjusted. For example, laser radar system 100 may capture one or more point clouds at a particular frame rate (e.g., 1Hz) and then switch to capturing the one or more point clouds at a different frame rate (e.g., 10 Hz). In general, a lidar system may use a slower frame rate (e.g., 1Hz) to capture one or more high resolution point clouds and a faster frame rate (e.g., 10Hz) to rapidly capture a plurality of low resolution point clouds.

The field of view of lidar system 100 may overlap, include, or encompass at least a portion of target 130, and target 130 may include all or a portion of an object that is moving or stationary relative to lidar system 100. For example, the target 130 may include all or part of a person, a vehicle, a motorcycle, a truck, a train, a bicycle, a wheelchair, a pedestrian, an animal, a road sign, a traffic light, a lane sign, a pavement sign, a parking space, a tower, a guardrail, a traffic fence, a pot hole, a railroad crossing, an obstacle on or near a road, a curb, a vehicle parked on or at a curb, a utility pole, a house, a building, a trash can, a mailbox, a tree, any other suitable object, or any suitable combination of all or part of two or more objects.

Referring now to fig. 2, scanner 162 and receiver 164 may operate in the lidar system of fig. 1 as scanner 120 and receiver 140, respectively. More generally, the scanner 162 and receiver 164 may operate in any suitable lidar system.

Scanner 162 may include any suitable number of mirrors driven by any suitable number of mechanical actuators. For example, the scanner 162 may include a galvanometer scanner, a resonant scanner, a piezoelectric actuator, a polygon scanner, a rotating prism scanner, a voice coil motor, a Direct Current (DC) motor, a brushless Direct Current (DC) motor, a stepper motor, or a micro-electro-mechanical system (MEMS) device, or any other suitable actuator or mechanism.

A galvanometer scanner (which may also be referred to as a galvanometer actuator) may include a galvanometer based scan motor with magnets and coils. When current is supplied to the coil, a rotational force is applied to the magnet, which causes the mirror attached to the galvanometer scanner to rotate. The current applied to the coil can be controlled to dynamically change the position of the galvanometer mirror. A resonant scanner (which may be referred to as a resonant actuator) may include a spring-like mechanism driven by the actuator to produce periodic oscillations at a substantially fixed frequency (e.g., 1 kHz). MEMS-based scanning devices may include a mirror having a diameter of about 1 to 10mm, where the mirror is rotated using electromagnetic actuation or electrostatic actuation. A voice coil motor (which may be referred to as a voice coil actuator) may include a magnet and a coil. When current is supplied to the coil, a translational force is placed on the magnet, which causes the mirror attached to the magnet to move or rotate.

In one example embodiment, the scanner 162 includes a single mirror configured to scan the output beam 170 in a single direction (e.g., the scanner 162 may be a one-dimensional scanner that scans in a horizontal or vertical direction). The mirror may be a planar scanning mirror attached to a scanner actuator or mechanism that scans the mirror over a particular angular range. The mirror may be driven by one actuator (e.g., a galvanometer) or two actuators configured to drive the mirror in a push-pull configuration. When two actuators drive the mirror in one direction in a push-pull configuration, the two actuators may be located on opposite or opposite sides of the mirror. The two actuators may work in a cooperative manner such that when one actuator pushes the mirror, the other actuator pulls the mirror, and vice versa. In another example embodiment, two voice coil actuators arranged in a push-pull configuration drive the mirror in either a horizontal or vertical direction.

In some implementations, the scanner 162 can include one mirror configured to be scanned along two axes, with two actuators arranged in a push-pull configuration providing motion along each axis. For example, two resonant actuators arranged in a horizontal push-pull configuration may drive the mirror in a horizontal direction, and another pair of resonant actuators arranged in a vertical push-pull configuration may drive the mirror in a vertical direction. In another example embodiment, two actuators scan the output beam 170 in two directions (e.g., horizontal and vertical), where each actuator provides rotational motion in a particular direction or about a particular axis.

The scanner 162 may also include a mirror driven by two actuators configured to scan the mirror in two substantially orthogonal directions. For example, a resonant actuator or a galvanometer actuator may drive one mirror in a substantially horizontal direction, and a galvanometer actuator may drive the mirror in a substantially vertical direction. As another example, two resonant actuators may drive the mirror in two substantially orthogonal directions.

In some embodiments, the scanner 162 includes two mirrors, one of which scans the output beam 170 in a substantially horizontal direction and the other of which scans the output beam 170 in a substantially vertical direction. In the example of FIG. 2, scanner 162 includes two mirrors, mirror 180-1 and mirror 180-2. Mirror 180-1 may scan output beam 170 in a substantially horizontal direction and mirror 180-2 may scan output beam 170 in a substantially vertical direction (or vice versa). Mirror 180-1 or mirror 180-2 may be a flat mirror, a curved mirror, or a polygonal mirror having two or more reflective surfaces.

In other embodiments, scanner 162 includes two galvanometer scanners that drive respective mirrors. For example, scanner 162 can include one galvanometer actuator that scans mirror 180-1 in a first direction (e.g., a vertical direction), and scanner 162 can include another galvanometer actuator that scans mirror 180-2 in a second direction (e.g., a horizontal direction). In yet another embodiment, the scanner 162 includes two mirrors, with a galvanometer actuator driving one mirror and a resonant actuator driving the other mirror. For example, a galvanometer actuator can scan mirror 180-1 in a first direction and a resonant actuator can scan mirror 180-2 in a second direction. The first and second scanning directions may be substantially orthogonal to each other, e.g. the first direction may be substantially vertical and the second direction may be substantially horizontal. In yet another embodiment, the scanner 162 includes two mirrors, one of which is a polygonal mirror that is rotated in one direction (e.g., clockwise or counterclockwise) by a motor (e.g., a brushless dc motor). For example, mirror 180-1 may be a polygonal mirror that scans output beam 170 in a substantially horizontal direction, and mirror 180-2 may scan output beam 170 in a substantially vertical direction. The polygon mirror may have two or more reflective surfaces, and the polygon mirror may be continuously rotated in one direction such that the output beam 170 is reflected from each reflective surface in turn. The polygonal mirror may have a cross-sectional shape corresponding to a polygon, wherein each side of the polygon has a reflective surface. For example, a polygonal mirror having a square sectional shape may have four reflecting surfaces, and a polygonal mirror having a pentagonal sectional shape may have five reflecting surfaces.

To direct the output beam 170 along a particular scan pattern, the scanner 162 can include two or more actuators that synchronously drive a single mirror. For example, the two or more actuators can synchronously drive the mirror in two substantially orthogonal directions such that the output beam 170 follows a scan pattern having a substantially straight line. In some embodiments, the scanner 162 may include two mirrors and two actuators that drive the two mirrors in synchronization to generate a scan pattern that includes substantially straight lines. For example, one galvanometer actuator may drive mirror 180-2 in a substantially linear reciprocating motion (e.g., the galvanometer may be driven in a substantially sinusoidal or triangular waveform), which causes output beam 170 to describe a substantially horizontal reciprocating pattern, while the other galvanometer actuator may scan mirror 180-1 in a substantially vertical direction. The two galvanometers may be synchronized such that for every 64 horizontal tracks, the output beam 170 forms one track in the vertical direction. Whether one or two mirrors are used, the substantially straight line may be directed substantially horizontally, vertically, or in any other suitable direction.

As the output beam 170 is scanned in a substantially horizontal direction (e.g., using galvanometer actuators or resonant actuators), the scanner 162 may also apply dynamically adjusted deflections in a vertical direction (e.g., using galvanometer actuators) to achieve a straight line. If no vertical deflection is applied, the output beam 170 may trace a curved path as it scans from side to side. In some embodiments, the scanner 162 uses a vertical actuator to apply dynamically adjusted vertical deflection as the output beam 170 is scanned horizontally, and to apply a discrete vertical offset between each horizontal scan (e.g., to step the output beam 170 to a subsequent line of the scan pattern).

With continued reference to fig. 2, in the present exemplary embodiment, overlap mirror 190 is configured to overlap input beam 172 and output beam 170 such that beams 170 and 172 are substantially coaxial. In fig. 2, the overlap mirror 190 includes a hole, slit, or aperture 192 through which the output beam 170 passes, and a reflective surface 194 that reflects at least a portion of the input beam 172 toward the receiver 164. The overlap mirror 190 may be oriented such that the input beam 172 and the output beam 170 at least partially overlap.

In some embodiments, the overlapping mirror 190 may not include the aperture 192. For example, output beam 170 may be directed to pass alongside mirror 190 rather than through aperture 192. Output beam 170 may pass along the sides of mirror 190 and may be oriented at a small angle relative to the direction of input beam 172. As another example, overlapping mirror 190 may include a small reflective portion configured to reflect output beam 170, and the remainder of overlapping mirror 190 may have an AR coating configured to transmit input beam 172.

The input beam 172 may pass through a lens 196, the lens 196 focusing the beam onto the active region 166 of the receiver 164. Active region 166 may refer to an area where receiver 164 may receive or detect input light. The active region may have any suitable size or diameter d, for example a diameter of about 25 μm, 50 μm, 80 μm, 100 μm, 200 μm, 500 μm, 1mm, 2mm or 5 mm. The reflective surface 194 of the overlapping mirror 190 may be substantially flat, or the reflective surface 194 may be curved (e.g., the mirror 190 may be an off-axis parabolic mirror configured to focus the input light beam 172 onto the active area of the receiver 140).

The apertures 192 may have any suitable size or diameter Φ₁The input beam 172 may have any suitable size or diameter Φ₂Wherein phi₂Greater than phi₁. For example, the diameter Φ of the aperture 192₁Which may be about 0.2mm, 0.5mm, 1mm, 2mm, 3mm, 5mm, or 10mm, the diameter Φ of the input beam 172₂May be about 2mm, 5mm, 10mm, 15mm, 20mm, 30mm, 40mm or 50 mm. In some embodiments, the reflective surface 194 of the overlapping mirror 190 may reflect 70% or more of the input light beam 172 toward the receiver 164. For example, if the reflective surface 194 has a reflectivity R at the operating wavelength of the light source 160, the fraction (fraction) of the input light beam 172 directed to the receiver 164 may be expressed as R1- (Φ)₁/Φ₂)²]. As a more specific example, if R is 95%, Φ₁Is 2mm, phi₂At 10mm, approximately 91% of the input light beam 172 may be directed toward the receiver 164 by the reflective surface 194.

FIG. 3 illustrates an example configuration in which several components of laser radar system 100 may operate to scan a 360 degree observation field. Generally, in such a configuration, the field of view of the light source follows a circular trajectory and thus defines a circular scanning pattern on a two-dimensional plane. According to one embodiment, all points on the trajectory remain at the same height with respect to the ground plane. In this case, the individual beams may follow circular trajectories with a certain vertical offset from each other. In another embodiment, the points of the trajectory may define a helical scan pattern in three-dimensional space. A single beam is sufficient to trace out the helical scan pattern, but multiple beams may be used if desired.

In the example of fig. 3, the rotational scanning module 200 rotates about a central axis in one or both of the directions indicated. For example, a motor may drive the rotary scanning module 200 to rotate at a constant speed about a central axis. The rotary scanning module 200 includes a scanner, a receiver, an overlapping mirror, and the like. The components of the rotation module 200 may be similar to the scanner 120, the receiver 140, and the overlap mirror 115. In some embodiments, subsystem 200 also includes a light source and a controller. In other embodiments, the light source and/or controller is provided separate from the rotary scanning module 200 and/or exchanges optical and electrical signals with components of the rotary scanning module 200 via respective links.

The rotary scan module 200 may include a housing 210 with a window 212. Similar to window 157 of fig. 1, window 212 may be made of glass, plastic, or any other suitable material. The window 212 allows the inbound beam and return signal to pass through the enclosure 210. The arc length defined by the window 212 may correspond to any suitable percentage of the circumference of the enclosure 210. For example, the arc length may correspond to 5%, 20%, 30%, 60%, or possibly even 100% of the circumference.

Referring now to FIG. 4, the rotational scanning module 220 is generally similar to the rotational scanning module 200. However, in this embodiment, the components of the rotating scanning module 220 are disposed on a platform 222, which platform 222 rotates within a stationary circular housing 230. In this embodiment, circular enclosure 230 is substantially transparent to the operating wavelength of the lidar system for the passage of inbound and outbound optical signals. Circular housing 230 defines a circular window similar to window 212 in a sense and may be made of similar materials.

Generating pixels within an observation field

Fig. 5 illustrates an example scan pattern 240 that may be generated by laser radar system 100 of fig. 1. Lidar system 100 may be configured to scan output optical beam 125 along one or more scan patterns 240. In some embodiments, the scan pattern 240 corresponds to a scan within any suitable field of view (FOR) having any combinationSuitable horizontal FOR (FOR)_H) And any suitable vertical for (forv). FOR example, a scan pattern may have a dimension defined by an angle (e.g., FOR)_HX forrv) an observation field expressed by 40 ° × 30 °, 90 ° × 40 °, or 60 ° × 15 °. As another example, FOR of a certain scanning pattern_HMay be greater than or equal to 10 °, 25 °, 30 °, 40 °, 60 °, 90 °, or 120 °. As yet another example, the FORv of a certain scan pattern may be greater than or equal to 2 °, 5 °, 10 °, 15 °, 20 °, 30 °, or 45 °. In the example of FIG. 5, reference line 246 represents the center of the field of view of scan pattern 240. Reference line 246 may have any suitable orientation, such as, for example, a horizontal angle of 0 ° (e.g., reference line 246 may be oriented straight ahead) and a vertical angle of 0 ° (e.g., reference line 246 may have an inclination of 0 °), or reference line 246 may have a non-zero horizontal angle or a non-zero inclination (e.g., +10 ° or-10 ° vertical). In FIG. 5, if scan pattern 240 has a field of view of 60 ° × 15 °, scan pattern 240 covers a horizontal range of ± 30 ° with respect to reference line 246 and a vertical range of ± 7.5 ° with respect to reference line 246. In addition, optical beam 125 in FIG. 5 has an orientation of approximately-15 horizontal and +3 vertical with respect to reference line 246. Beam 125 may be said to have an azimuth angle of-15 ° and an elevation of +3 ° relative to reference line 246. Azimuth (which may be referred to as azimuth) may represent a horizontal angle relative to reference line 246, and elevation (which may be referred to as elevation angle, elevation or elevation angle) may represent a vertical angle relative to reference line 246.

The scan pattern 240 may include a plurality of pixels 242, and each pixel 242 may be associated with one or more laser pulses and one or more corresponding distance measurements. The cycle of the scan pattern 240 may include a total of P_x×P_yA pixel 242 (e.g., P)_xMultiplying by P_yA two-dimensional distribution of individual pixels). For example, the scan pattern 240 may include a distribution having a size of about 100-2,000 pixels 242 along the horizontal direction and about 4-400 pixels 242 along the vertical direction. As another example, for a total of 64,000 pixels per cycle of the scan pattern 240, the distribution of the scan pattern 240 may be 1,000 pixels 242 in the horizontal direction by 64 pixels 242 in the vertical direction (e.g.,the frame size is 1000 × 64 pixels). The number of pixels 242 in the horizontal direction may be referred to as the horizontal resolution of the scan pattern 240, and the number of pixels 242 in the vertical direction may be referred to as the vertical resolution of the scan pattern 240. As one example, the scan pattern 240 may have a horizontal resolution greater than or equal to 100 pixels 242 and a vertical resolution greater than or equal to 4 pixels 242. As another example, the scan pattern 240 may have a horizontal resolution of 100-2,000 pixels 242 and a vertical resolution of 4-400 pixels 242.

Each pixel 242 may be associated with a distance (e.g., a distance to a portion of target 130 from which the associated laser pulse was scattered) or one or more angular values. For example, pixel 242 may be associated with a distance value and two angular values (e.g., azimuth and elevation) that represent the angular position of pixel 242 relative to laser radar system 100. The distance to a portion of the target 130 may be determined based at least in part on a time-of-flight measurement of the corresponding pulse. The angle value (e.g., azimuth or elevation) may correspond to an angle of output beam 125 (e.g., relative to reference line 246) (e.g., when a corresponding pulse is transmitted from lidar system 100) or an angle of input beam 135 (e.g., when lidar system 100 receives an input signal). In some embodiments, lidar system 100 determines the angle value based at least in part on the position of components of scanner 120. For example, an azimuth or elevation value associated with pixel 242 may be determined from the angular position of one or more respective scan mirrors of scanner 120.

In some embodiments, lidar system 100 directs multiple beams simultaneously in the observation field. In the example embodiment of FIG. 6, the lidar system generates output beams 250A, 250B, 250C … 250N, etc., each of which follows a linear scanning pattern 254A, 254B, 254C … 254N. The number of parallel lines may be 2, 4, 12, 20 or any other suitable number. Lidar system 100 may angularly separate beams 250A, 250B, 250C … 250N such that, for example, at some distance the separation between beams 250A and 250B may be 30cm, and at longer distances the separation between the same beams 250A and 250B may be 50 cm.

Similar to scan pattern 240, each linear scan pattern 254A-N includes pixels associated with one or more laser pulses and distance measurements. Fig. 6 shows example pixels 252A, 252B, and 252C along scan patterns 254A, 254B, and 254C, respectively. Lidar system 100 in this example may generate values for pixels 252A-252N simultaneously, thereby increasing the rate at which pixel values are determined.

According to this embodiment, laser radar system 100 may output light beams 250A-N of the same wavelength or different wavelengths. For example, light beam 250A may have a wavelength of 1540nm, light beam 250B may have a wavelength of 1550nm, light beam 250C may have a wavelength of 1560nm, and so forth. The number of different wavelengths used by laser radar system 100 need not match the number of beams. Thus, lidar system 100 in the example embodiment of FIG. 6 may use M wavelengths with N beams, where 1 ≦ M ≦ N.

Next, FIG. 7 illustrates an exemplary light source field of view (FOV) for lidar system 100_L) And receiver field of view (FOV)_R). When the scanner 120 scans the FOV in the field of view (FOR)_LAnd FOV_RThe light source 110 may emit light pulses. The source field of view may refer to the angular cone (angular cone) illuminated by the light source 110 at a particular time. Likewise, the receiver field of view may also refer to a pyramid by which the receiver 140 may receive or detect light at a particular time, while any light outside the receiver field of view may not be received or detected. For example, as scanner 120 scans the field of view of the light source in the field of view, lidar system 100 may follow the FOV as light source 110 emits pulses_LThe directed direction emits a light pulse. The light pulses may be scattered off the target 130, and the receiver 140 may receive and detect along the FOV_RGuided or contained in the FOV_RIs a portion of the scattered light in (1).

In some embodiments, scanner 120 may be configured to scan the light source field of view and the receiver field of view in the field of view of lidar system 100. When the scanner 120 scans the FOV in the observation field_LAnd FOV_RIn time, laser radar system 100 may emit and detect multiple lightsA pulse while scan pattern 240 is depicted. In some embodiments, the light source field of view and the receiver field of view are scanned synchronously with respect to each other by the scanner 120. In this case, when the scanner 120 is in the scan mode 240, the FOV is scanned_LTime of day, FOV_RSubstantially the same path is followed at the same scan speed. In addition, when the scanner 120 scans the FOV in the observation field_LAnd FOV_RTime of day, FOV_LAnd FOV_RThe same relative position can be maintained. For example, the FOV_LCan be aligned with the FOV_RSubstantially overlapping or centered in the FOV_RInside (as shown in fig. 7), and the scanner 120 can maintain the FOV throughout the scan_LAnd FOV_RRelative position therebetween. As another example, throughout the scan, the FOV_RMay lag behind the FOV_LA certain fixed quantity (e.g. FOV)_RThe FOV may be offset in a direction opposite to the scanning direction_L)。

FOV_LMay have an angular dimension or range Θ_L，Θ_LSubstantially the same as or corresponding to the divergence of the output beam 125, and a FOV_RMay have an angular dimension or range Θ_R，Θ_RThe receiver 140 may receive and detect light within an angle corresponding to the angle. The receiver field of view may be any suitable size relative to the source field of view. For example, the receiver field of view may be less than, substantially equal to, or greater than the angular extent of the source field of view. In some embodiments, the angular range of the field of view of the light source is less than or equal to 50mrad and the angular range of the field of view of the receiver is less than or equal to 50 mrad. FOV (field of View)_LCan have any suitable angular range Θ_LFor example, about 0.1mrad, 0.2mrad, 0.5mrad, 1mrad, 1.5mrad, 2mrad, 3mrad, 5mrad, 10mrad, 20mrad, 40mrad, or 50 mrad. Likewise, the FOV_RCan have any suitable angular range Θ_RFor example, about 0.1mrad, 0.2mrad, 0.5mrad, 1mrad, 1.5mrad, 2mrad, 3mrad, 5mrad, 10mrad, 20mrad, 40mrad, or 50 mrad. The light source field of view and the receiver field of view may have approximately equal angular ranges. As an example, Θ_LAnd Θ_RCan all approximateEqual to 1mrad, 2mrad or 3 mrad. In some embodiments, the receiver field of view may be larger than the light source field of view, or the light source field of view may be larger than the receiver field of view. For example, Θ_LCan be approximately equal to 1.5mrad, and theta_RMay be approximately equal to 3 mrad.

The pixels 242 may represent or correspond to a light source field of view. The diameter of the output light beam 125 (and the size of the corresponding pixel 242) may be in accordance with the beam divergence Θ as the output light beam 125 propagates from the light source 110_LAnd is increased. As an example, if Θ of the output beam 125 is_LAt 2mrad, the output beam 125 may be approximately 20cm in size or diameter and the corresponding pixel 242 may be approximately 20cm in size or diameter at a distance of 100m from the lidar system 100. At a distance of 200m from laser radar system 100, output beam 125 and corresponding pixel 242 may each be approximately 40cm in diameter.

Lidar system for operation in a vehicle

As described above, one or more lidar systems 100 may be integrated into a vehicle. In an example embodiment, multiple lidar systems 100 may be integrated into an automobile to provide a full 360 degree horizontal FOR around the automobile. As another example, 4-10 lidar systems 100 (each having a horizontal FOR of 45 degrees to 90 degrees) may be combined together to form a sensing system that provides a point cloud covering 360 degrees of horizontal FOR. Lidar system 100 may be oriented such that adjacent FOR's have some amount of spatial or angular overlap, allowing data from multiple lidar systems 100 to be combined or stitched together to form a single or continuous 360 degree point cloud. As an example, the FOR of each lidar system 100 may have approximately 1-15 degrees of overlap with adjacent FORs. In particular embodiments, a vehicle may refer to a mobile machine configured to transport people or cargo. For example, the vehicle may comprise, may take the form of, or may be referred to as an automobile, car, motor vehicle, truck, bus, van, trailer, off-road vehicle, farm vehicle, lawn mower, construction implement, forklift, robot, golf cart, recreational vehicle, taxi, motorcycle, scooter, bicycle, skateboard, train, snowmobile, watercraft (such as a boat or boat), aircraft (such as a fixed wing aircraft, helicopter, or airship), or spacecraft. In particular embodiments, the vehicle may include an internal combustion engine or an electric motor that provides propulsion for the vehicle.

In some embodiments, one or more lidar systems 100 may be included in a vehicle as part of an Advanced Driver Assistance System (ADAS) to assist a vehicle driver during driving. For example, lidar system 100 may be part of an ADAS that provides information or feedback to a driver (e.g., to alert the driver of a potential problem or hazard), or that automatically controls a part of a vehicle (e.g., a braking system or steering system) to avoid a collision or accident. Lidar system 100 may be part of a vehicle ADAS that provides adaptive cruise control, automatic braking, automatic parking, collision avoidance, alerts the driver of a hazard or other vehicle, holds the vehicle in the correct lane, or provides a warning if an object or other vehicle is in a blind spot.

In some cases, one or more lidar systems 100 may be integrated into a vehicle as part of an autonomous vehicle driving system. In an example embodiment, lidar system 100 may provide information about the surrounding environment to the autonomous vehicle's driving system. The autonomous vehicle driving system may include one or more computing systems that receive information about the surrounding environment from lidar system 100, analyze the received information, and provide control signals to the vehicle's driving system (e.g., steering wheel, throttle, brake, or turn signals). As one example, lidar system 100 integrated into an autonomous vehicle may provide a point cloud for the autonomous vehicle driving system every 0.1 seconds (e.g., the update rate of the point cloud is 10Hz, representing 10 frames per second). The autonomous vehicle driving system may analyze the received point clouds to sense or identify the targets 130 and their respective locations, distances, or velocities, and the autonomous vehicle driving system may update the control signals based on this information. As one example, if laser radar system 100 detects that a vehicle in front is decelerating or stopping, the autonomous vehicle driving system may send instructions to release the throttle and apply the brakes.

An autonomous vehicle may be referred to as an autonomous automobile, an unmanned automobile, an autonomous automobile, a robotic automobile, or an unmanned vehicle. An autonomous vehicle may refer to a vehicle configured to sense its environment and navigate or drive with little or no human intervention. For example, an autonomous vehicle may be configured to travel to any suitable location and control or perform all safety critical functions (e.g., driving, steering, braking, parking) throughout a trip, without the driver expecting to control the vehicle at any time. As another example, an autonomous vehicle may divert a driver's attention away safely from driving tasks in a particular environment (e.g., a highway), or an autonomous vehicle may provide control of the vehicle in all but a few environments, requiring little or no intervention or attention by the driver.

The autonomous vehicle may be configured to drive with a driver present in the vehicle, or the autonomous vehicle may be configured to operate the vehicle without a driver present. As one example, an autonomous vehicle may include a driver's seat with associated controls (e.g., a steering wheel, an accelerator pedal, and a brake pedal), and the vehicle may be configured to drive with little or no intervention by a person sitting in or on the driver's seat. As another example, an autonomous vehicle may not include any driver's seat or associated driver controls, and the vehicle may perform most of the driving functions (e.g., driving, steering, braking, parking, and navigation) without human intervention. As another example, an autonomous vehicle may be configured to operate without a driver (e.g., the vehicle may be configured to transport passengers or cargo without the presence of a driver within the vehicle). As another example, an autonomous vehicle may be configured to operate without any passengers (e.g., the vehicle may be configured to transport cargo without any passengers being on the vehicle).

In some embodiments, the light source of the lidar system is located remotely from certain other components of the lidar system (e.g., the scanner and the receiver). Further, lidar systems implemented in vehicles may include fewer light sources than scanners and receivers.

Fig. 8 shows an example configuration in which a laser-sensor link 320 includes an optical link 330 and an electrical link 350 coupled between the laser 300 and the sensor 310. The laser 300 may be configured to emit light pulses and may be referred to as a laser system, a laser head, or a light source. The laser 300 may include or may be similar to the light source 110 shown in fig. 1 and discussed above, or may be part of the light source 110 shown in fig. 1 and discussed above, or may be substantially the same as the light source 110 shown in fig. 1 and discussed above. Further, scanner 302, receiver 304, controller 306, and mirror 308 may be similar to scanner 120, receiver 140, controller 150, and mirror 115 discussed above. In the example of fig. 8, laser 300 is coupled to remotely located sensor 310 by laser-sensor link 320 (which may be referred to as a link). The sensor 310 may be referred to as a sensing head and may include a mirror 308, a scanner 302, a receiver 304, and a controller 306. In one example embodiment, the laser 300 comprises a pulsed laser diode (e.g., a pulsed Distributed Feedback (DFB) laser), followed by an optical amplifier, and the light from the laser 300 is transmitted through an optical fiber of suitable length of laser-sensor link 320 to the scanner 120 in a remotely located sensor 310.

The laser-sensor link 320 may include any suitable number of optical links 330 (e.g., 0, 1, 2, 3, 5, or 10) and any suitable number of electrical links 350 (e.g., 0, 1, 2, 3, 5, or 10). In the example configuration shown in fig. 8, laser-sensor link 320 includes one optical link 330 from laser 300 to output collimator 340 and one electrical link 350 connecting laser 300 to controller 150. Optical link 330 may include an optical fiber (which may be referred to as a fiber optic cable or optical fiber) that carries, communicates, transports, or transmits light between laser 300 and sensor 310. The optical fiber may be, for example, a Single Mode (SM) fiber, a multimode (MM) fiber, a Large Mode Area (LMA) fiber, a Polarization Maintaining (PM) fiber, a photonic crystal or photonic bandgap fiber, a gain fiber (e.g., a rare earth doped fiber for an optical amplifier), or any suitable combination thereof. Output collimator 340 receives the optical pulses transmitted from laser 300 by optical link 330 and produces free-space optical beam 312 that includes the optical pulses. Output collimator 340 directs free-space optical beam 312 through mirror 308 and to scanner 302.

Electrical link 350 may include a wire or cable (e.g., a coaxial cable or twisted pair cable) that carries or transmits electrical power and/or one or more electrical signals between laser 300 and sensor 310. For example, the laser 300 may include a power supply or power regulator that provides electrical power to the laser 300, and additionally, may provide power to one or more components of the sensor 310 (e.g., the scanner 304, receiver 304, and/or controller 306) via one or more electrical links 350. In some embodiments, electrical link 350 may carry electrical signals that include data or information in analog or digital form. In addition, electrical link 350 may provide an interlock signal from sensor 310 to laser 300. If controller 306 detects a fault condition indicating that sensor 310 or the entire lidar system is experiencing a problem, controller 306 may change the voltage on the interlock line (e.g., from 5V to 0V) indicating that laser 300 should shut down, stop emitting light, or reduce the power or energy of the emitted light. The fault condition may be triggered by a failure of the scanner 302, a failure of the receiver 304, or by a person or object entering within a threshold distance (e.g., within 0.1m, 0.5m, 1m, 5m, or any other suitable distance) of the sensor 310.

As described above, the lidar system may include one or more processors to determine the distance D to the target. In the embodiment shown in fig. 8, controller 306 may be located in laser 300 or sensor 310, or portions of controller 306 may be distributed between laser 300 and sensor 310. In an example embodiment, each sensing head 310 of the lidar system includes electronics (e.g., electronic filters, transimpedance amplifiers, threshold detectors, or time-to-digital (TDC) converters) configured to receive or process signals from receiver 304 or from APDs or SPADs of receiver 304. Additionally, laser 300 may include processing electronics configured to determine a time-of-flight value or distance to a target based on signals received from sense head 310 via electrical link 350.

Next, fig. 9 illustrates an example vehicle 354 having a lidar system 351, the lidar system 351 including a laser 352 having a plurality of sensor heads 360, the plurality of sensor heads 360 coupled to the laser 352 via a plurality of laser-sensor links 370. In some embodiments, laser 352 and sense head 360 may be similar to laser 300 and sensor 310 discussed above. For example, each laser-sensor link 370 may include one or more optical links and/or one or more electrical links. The sensor head 360 in fig. 9 is positioned or oriented to provide a view of the vehicle surroundings of greater than 30 degrees. More generally, lidar systems having multiple sensor heads may provide a horizontal field of view around the vehicle of approximately 30 °, 45 °, 60 °, 90 °, 120 °, 180 °, 270 °, or 360 °. Each sensor head may be attached to or incorporated into a bumper, fender, grid guard, side panel, airflow deflector, roof, headlamp assembly, tail lamp assembly, rear view mirror assembly, hood, trunk, window opening, or any other suitable component of a vehicle.

In the example of fig. 9, four sensor heads 360 are located at or near the four corners of the vehicle (e.g., the sensor heads may be incorporated into a light assembly, a side panel, a bumper, or a fender), and the lasers 352 may be located within the vehicle (e.g., in or near a trunk). The four sensor heads 360 may each provide a 90-120 horizontal field of view (FOR), and the four sensor heads 360 may be oriented such that together they provide a complete 360 view of the vehicle surroundings. As another example, lidar system 351 may include six sensor heads 360 located on or around the vehicle, where each sensor head 360 provides a horizontal FOR of 60 ° -90 °. As another example, lidar system 351 may include eight sensor heads 360, and each sensor head 360 may provide a horizontal FOR of 45-60. As yet another example, lidar system 351 may include six sensor heads 360, where each sensor head 360 provides a 70 ° horizontal FOR, with an overlap between adjacent FOR of approximately 10 °. As another example, lidar system 351 may include two sensor heads 360 that together provide a forward horizontal FOR that is greater than or equal to 30 °.

The data from each of the sensor heads 360 may be combined or stitched together to generate a point cloud covering a horizontal view of greater than or equal to 30 degrees around the vehicle. For example, the laser 352 may include a controller or processor that receives data from each of the sensor heads 360 (e.g., via the respective electrical links 370) and processes the received data to construct a point cloud covering a horizontal view of 360 degrees of the vehicle surroundings or to determine a distance to one or more targets. The point cloud or information from the point cloud may be provided to the vehicle controller 372 via a corresponding electrical, optical, or radio link 370. In some embodiments, a point cloud is generated by combining data from each of the plurality of sensor heads 360 at a controller contained within the laser 352 and provided to the vehicle controller 372. In other embodiments, each sensor head 360 includes a controller or processor that constructs a point cloud for a portion of the 360 degree horizontal view of the vehicle surroundings and provides the respective point cloud to the vehicle controller 372. The vehicle controller 372 then combines or stitches the point clouds from the respective sensor heads 360 to construct a combined point cloud covering a 360 degree horizontal view. Further, in some embodiments, the vehicle controller 372 communicates with a remote server to process the point cloud data.

In any case, the vehicle 354 may be an autonomous vehicle, with the vehicle controller 372 providing control signals to various components 390 within the vehicle 354 to maneuver and control operation of the vehicle 354. The assembly 390 is depicted in the expanded view of fig. 9 for ease of illustration only. The components 390 may include a throttle 374, brakes 376, a vehicle engine 378, a steering mechanism 380, lights 382 (e.g., brake lights, headlamps, backup lights, emergency lights, etc.), a gear selector 384, and/or other suitable components to effect and control movement of the vehicle 354. The gear selector 384 may include park, reverse, neutral, drive, and the like. Each assembly 390 may include an interface via which the assembly receives commands from the vehicle controller 372, such as "accelerate," "decelerate," "turn left 5 degrees," "turn left turn light," etc., and in some cases, provides feedback to the vehicle controller 372.

In some embodiments, the vehicle controller 372 receives point cloud data from the laser 352 or the sense head 360 via the link 370 and analyzes the received point cloud data to sense or identify the targets 130 and their respective locations, distances, speeds, shapes, sizes, target types (e.g., vehicle, human, tree, animal), and the like. The vehicle controller 372 then provides control signals to the assembly 390 via the link 370 to control operation of the vehicle based on the analyzed information. For example, the vehicle controller 372 may identify an intersection based on the point cloud data and determine that the intersection is a suitable location for making a left turn. Thus, the vehicle controller 372 may provide control signals to the steering mechanism 380, throttle 374, and brake 376 to make the appropriate left turn. In another example, the vehicle controller 372 may identify a traffic light based on the point cloud data and determine that the vehicle 354 needs to stop. Thus, the vehicle controller 372 may provide control signals to release the throttle 374 and depress the brake 376.

Example receiver implementation

Fig. 10 shows an example InGaAs Avalanche Photodiode (APD) 400. Referring back to fig. 1, receiver 140 may include one or more APDs 400 configured to receive and detect light from an input light (e.g., optical beam 135). More generally, APD400 may operate in any suitable input optical receiver. APD400 may be configured to detect a portion of an optical pulse scattered by a target located in a forward-to-transmit position of a lidar system in which APD400 operates. For example, APD400 may receive a portion of an optical pulse scattered by target 130 shown in fig. 1 and generate a current signal corresponding to the received optical pulse.

APD400 may include doped or undoped layers of any suitable semiconductor material, such as silicon, germanium, InGaAs, InGaAsP, or indium phosphide (InP). In addition, APD400 can include an upper electrode 402 and a lower electrode 406 for coupling APD400 to circuitry. For example, APD400 can be electrically coupled to a voltage source that provides a reverse bias voltage V to APD 400. In addition, APD400 may be electrically coupled to a transimpedance amplifier that receives the current generated by APD400 and produces an output voltage signal corresponding to the received current. The upper electrode 402 or the lower electrode 406 may comprise any suitable conductive material, such as a metal (e.g., gold, copper, silver, or aluminum), a transparent conductive oxide (e.g., indium tin oxide), a carbon nanotube material, or polysilicon. In some embodiments, upper electrode 402 is partially transparent or has an opening to allow input light 410 to pass through to the active region of APD 400. In fig. 10, upper electrode 402 may have a ring-like structure that at least partially surrounds an active area of APD400, where active area refers to the area where APD400 may receive and detect input light 410. The active region may have any suitable size or diameter d, for example, a diameter of about 25 μm, 50 μm, 80 μm, 100 μm, 200 μm, 500 μm, 1mm, 2mm, or 5 mm.

APD400 can include any suitable combination of any suitable semiconductor layers having any suitable doping (e.g., n-doped, p-doped, or intrinsic undoped material). In the example of fig. 10, the InGaAs APD400 includes a p-doped InP layer 420, an InP avalanche layer 422, an absorption layer 424 with n-doped InGaAs or InGaAsP, and an n-doped InP substrate layer 426. Depending on the implementation, APD400 may include separate absorption and avalanche layers, or a single layer may serve as both an absorption region and an avalanche region. APD400 can be electrically operated as a PN diode or PIN diode, and during operation, APD400 can be reverse biased by a positive voltage V applied to lower electrode 406 relative to upper electrode 402. The applied reverse bias voltage V may have any suitable value, for example, about 5V, 10V, 20V, 30V, 50V, 75V, 100V, or 200V.

In fig. 10, photons of input light 410 may be absorbed primarily in absorption layer 424, thereby generating electron-hole pairs (which may be referred to as photogenerated carriers). For example, absorption layer 424 may be configured to absorb photons corresponding to an operating wavelength of laser radar system 100 (e.g., any suitable wavelength between approximately 1400nm and approximately 1600 nm). In the avalanche layer 422, an avalanche multiplication process occurs in a case where carriers (for example, electrons or holes) generated in the absorption layer 424 collide with the semiconductor lattice of the absorption layer 424 and additional carriers are generated by impact ionization. This avalanche process can be repeated many times, so that one photogenerated carrier can result in the generation of multiple carriers. As one example, a single photon absorbed in the absorption layer 424 may generate approximately 10, 50, 100, 200, 500, 1000, 10,000, or any other suitable number of carriers through an avalanche multiplication process. Carriers generated in APD400 can generate a current that couples to circuitry that can perform signal amplification, sampling, filtering, signal conditioning, analog-to-digital conversion, time-to-digital conversion, pulse detection, threshold detection, rising edge detection, or falling edge detection.

The number of carriers generated by a single photogenerated carrier may increase with increasing applied reverse bias V. If the applied reverse bias V increases above a certain value (referred to as the APD breakdown voltage), a single carrier can trigger a self-sustaining avalanche process (e.g., the output of APD400 is saturated regardless of the input optical level). APD400 operating at or above a breakdown voltage may be referred to as a Single Photon Avalanche Diode (SPAD) and may be referred to as operating in a geiger mode or a photon counting mode. APD400 operating below the breakdown voltage may be referred to as a linear APD, and the output current produced by APD400 may be sent to an amplifier circuit (e.g., a transimpedance amplifier). The receiver 140 (see fig. 1) may include: an APD configured to operate as a SPAD, and a quenching circuit configured to reduce a reverse bias voltage applied to the SPAD when an avalanche event occurs in the SPAD. APD400, configured to operate as a SPAD, can be coupled to an electron quenching circuit that reduces the applied voltage V below the breakdown voltage when an avalanche detection event occurs. Reducing the applied voltage can stop the avalanche process and then the applied reverse bias voltage can be reset to await a subsequent avalanche event. In addition, APD400 can be coupled to circuitry that generates an electrical output pulse or edge when an avalanche event occurs.

In some embodiments, APD400, or APD400 with a transimpedance amplifier, has a Noise Equivalent Power (NEP) of less than or equal to 100 photons, 50 photons, 30 photons, 20 photons, or 10 photons. For example, APD400 may operate as a SPAD and may have a NEP of less than or equal to 20 photons. As another example, APD400 may be coupled to a transimpedance amplifier that produces an output voltage signal having a NEP of less than or equal to 50 photons. The NEP of APD400 is a metric that quantifies the sensitivity of APD400 in terms of the minimum signal (or minimum number of photons) that APD400 is able to detect. NEP may correspond to an optical power (or photon count) that results in a signal-to-noise ratio of 1, or NEP may represent a threshold photon count above which an optical signal may be detected. For example, if APD400 has a NEP of 20 photons, then input optical beam 410, having 20 photons, may be detected with a signal-to-noise ratio of about 1 (e.g., APD400 may receive 20 photons from input optical beam 410 and generate an electrical signal that indicates that input optical beam 410 has a signal-to-noise ratio of about 1). Likewise, an input beam 410 having 100 photons can be detected with a signal-to-noise ratio of about 5. In some embodiments, lidar system 100 (with APD400 or a combination of APD400 and a transimpedance amplifier) having an NEP of less than or equal to 100 photons, 50 photons, 30 photons, 20 photons, or 10 photons improves detection sensitivity relative to conventional lidar systems using PN or PIN photodiodes. For example, the NEP of an InGaAs PIN photodiode used in a conventional lidar system is about 10⁴To 10⁵Per photon, and noise levels in a lidar system having an InGaAs PIN photodiode may be greater than those with an InGaAs APD detector 400Noise level in lidar system 100 is 10 degrees greater³To 10⁴And (4) doubling.

Referring back to fig. 1, the front of the receiver 140 may be provided with an optical filter configured to transmit light of one or more operating wavelengths of the light source 110 and attenuate light of surrounding wavelengths. For example, the optical filter may be a free-space spectral filter located in front of APD400 of fig. 10. The spectral filter may transmit light at the operating wavelength of light source 110 (e.g., between about 1530nm and 1560 nm) and attenuate light outside of this wavelength range. As a more specific example, light having a wavelength of approximately 400-1530nm or 1560-2000nm may be attenuated by any suitable amount, such as at least 5dB, 10dB, 20dB, 30dB, or 40 dB.

Next, fig. 11 shows an APD502 coupled to an example pulse detection circuit 504. APD502 may be similar to APD400 discussed above with reference to fig. 10, or may be any other suitable detector. Pulse detection circuitry 504 may operate in the lidar system of fig. 1 as part of receiver 140. Further, the pulse detection circuit 504 may operate in the receiver 164 of fig. 2, the receiver 304 of fig. 8, or any other suitable receiver. The pulse detection circuit 504 may optionally be implemented in the controller 150, the controller 306, or another suitable controller. In some implementations, some portions of the pulse detection circuitry 504 may operate in a receiver and other portions of the pulse detection circuitry 504 may operate in a controller. For example, components 510 and 512 may be part of receiver 140, and components 514 and 516 may be part of controller 150.

Pulse detection circuitry 504 may include circuitry that receives a signal from a detector (e.g., a current from APD 502) and performs current-to-voltage conversion, signal amplification, sampling, filtering, signal conditioning, analog-to-digital conversion, time-to-digital conversion, pulse detection, threshold detection, rising edge detection, or falling edge detection. Pulse detection circuitry 504 may determine whether APD502 received an optical pulse or may determine a time associated with APD502 receiving an optical pulse. In addition, the pulse detection circuit 504 may determine the duration of the received optical pulse. In an example embodiment, the pulse detection circuit 504 includes a transimpedance amplifier (TIA)510, a gain circuit 512, a comparator 514, and a time-to-digital converter (TDC) 516.

The TIA510 may be configured to receive a current signal from the APD502 and generate a voltage signal corresponding to the received current signal. For example, in response to a received optical pulse, APD502 may generate a current pulse corresponding to the optical pulse. The TIA510 may receive current pulses from the APD502 and generate voltage pulses corresponding to the received current pulses. The TIA510 may also function as an electronic filter. For example, the TIA510 may be configured as a low pass filter to remove or attenuate high frequency electrical noise by attenuating signals above a particular frequency (e.g., above 1MHz, 10MHz, 20MHz, 50MHz, 100MHz, 200MHz, or any other suitable frequency).

The gain circuit 512 may be configured to amplify the voltage signal. As one example, the gain circuit 512 may include one or more voltage amplification stages that amplify voltage signals received from the TIA 510. For example, the gain circuit 512 may receive a voltage pulse from the TIA510, and the gain circuit 512 may amplify the voltage pulse by any suitable amount, e.g., a gain of approximately 3dB, 10dB, 20dB, 30dB, 40dB, or 50 dB. In addition, the gain circuit 512 may also function as an electronic filter configured to remove or attenuate electrical noise.

The comparator 514 may be configured to receive a voltage signal from the TIA510 or the gain circuit 512 and to determine whether the received voltage signal is above or below a particular threshold voltage V_TAn electrical-edge signal (e.g., a rising edge or a falling edge) is generated. As an example, when the received voltage is higher than V_TThe comparator 514 may generate a rising edge digital-to-voltage signal (e.g., a signal that steps from about 0V to about 2.5V, 3.3V, 5V, or any other suitable digital-to-high level). As another example, when the received voltage is below V_TThe comparator 514 may generate a falling edge digital-to-voltage signal (e.g., a signal that steps down from about 2.5V, 3.3V, 5V, or any other suitable digital-to-high level to about 0V). Comparator 514 receivesMay be received from the TIA510 or the gain circuit 512, and may correspond to the current signal generated by the APD 502. For example, the voltage signal received by comparator 514 may include a voltage pulse corresponding to a current pulse generated by APD502 in response to the received optical pulse. The voltage signal received by the comparator 514 may be an analog signal and the electrical-edge signal generated by the comparator 514 may be a digital signal.

A time-to-digital converter (TDC)516 may be configured to receive the electrical-edge signal from the comparator 514 and determine a time interval between the light source emitting a light pulse and receiving the electrical-edge signal. The output of the TDC 516 may be a value corresponding to a time interval determined by the TDC 516. In some embodiments, the TDC 516 has an internal counter or timer with any suitable period, e.g., 5ps, 10ps, 15ps, 20ps, 30ps, 50ps, 100ps, 0.5ns, 1ns, 2ns, 5ns, or 10 ns. For example, the TDC 516 may have an internal counter or timer with a period of 20ps, and the TDC 516 may determine that the time interval between transmission and reception of the pulses is equal to 25,000 periods, corresponding to a time interval of approximately 0.5 microseconds. Returning to fig. 1, TDC 516 may send a value of "25000" to a processor or controller 150 of lidar system 100, which may include a processor configured to determine a distance from lidar system 100 to target 130 based at least in part on a time interval determined by TDC 516. The processor may receive a value (e.g., "25000") from TDC 516, and based on the received value, the processor may determine a distance from laser radar system 100 to target 130.

In some embodiments, the gain produced by the gain circuit 512 may vary over time. In general, the gain circuit 512 may use a variable gain to prevent false detection of a return light pulse scattered by a remote target (i.e., false positives). To prevent saturation and reduce noise at APD502 (or at pulse detection circuit 504), in an example embodiment, gain circuit 512 is configured to emit a pulse of light from light source 110 at time t₀Initially, the threshold period of time T1 is operated in the low gain mode. May be determined in any suitable mannerAt a given time t₀. For example, to initialize the TDC 516 or another TDC, the pulse detection circuit 504 receives a signal from the controller 150 or the light source 110 indicating that a pulse of light has been emitted. Thus, the TDC 516 initializes the timer and the gain circuit 512 operates in the low gain mode for the threshold time period T1. In another example, as a light pulse is emitted, APD502 and/or pulse detection circuit 504 detect light from the light pulse, initialize a timer at TDC 516, and operate gain circuit 512 in a low gain mode for a threshold time period T1. More specifically, when an optical signal (having a value above a threshold amount) is received at APD502, APD502 and/or pulse detection circuit 504 detects light from the optical pulse. The detected light pulses, when emitted, may be referred to as "optical t₀”。

In some implementations, changing or adjusting the gain of the gain circuit 512 (which may be referred to as changing or adjusting the gain of the pulse detection circuit 504) may include changing or adjusting the gain of one or more electrical components in the pulse detection circuit 504. For example, changing the gain of the gain circuit 512 may include one or more of: varying the gain of one or more voltage amplification stages in gain circuit 512; changing the transimpedance gain of the TIA 510; or both the gain of the gain circuit 512 and the transimpedance gain of the TIA 510. As another example, changing the gain of the gain circuit 512 may include: the gain of the voltage amplifier in the gain circuit 512 is changed and the gain of the TIA510 is kept substantially constant. As another example, changing the gain of the gain circuit 512 may include: the gain of the gain circuit 512 is maintained substantially constant and the gain of the TIA510 is changed.

The threshold time period T1 may be configured such that the optical signal detected within the threshold time period T1 is indicative of an emitted light pulse rather than a light pulse scattered and returned to the receiver, or a return light pulse scattered by a target within a minimum distance (e.g., 1 m). More specifically, the threshold time period T1 may be greater than or equal to the time of flight corresponding to the minimum distance (e.g., 6.66ns for a minimum distance of 1 m).

At the end of the threshold time period T1, the gain circuit 512 is configured to be at high gainThe mode operates for a threshold period of time T2. The threshold time period T2 may be configured to last from when the threshold time period T1 ends until when a subsequent pulse is transmitted. For example, when the light source 110 generates pulses at a pulse repetition frequency of about 750kHz, the threshold time period T2 may be from T1 (e.g., from T) corresponding to a pulse period of 1.33 μ s and a maximum distance of 200m₀First 6.66ns) to from t₀First 1.33. mu.s. Then, when the light source emits a subsequent light pulse, the gain circuit 512 is configured to return to the low gain mode for another threshold time period T1. In an example embodiment, the low gain mode may have a gain of 3dB, while the high gain mode has a gain of 50 dB.

In other embodiments, the gain is configured to gradually increase over time from when the optical pulse is transmitted until a subsequent optical pulse is transmitted, at which time the gain circuit 512 returns to the original gain from when the initial optical pulse was transmitted. In still other embodiments, the gain may remain at a fixed gain value during the threshold time period T1, and then the gain may gradually increase over time during the threshold time period T2.

In any case, as described above, the amplified signal from the gain circuit 512 is then provided to the comparator 514, the comparator 514 configured to compare the amplified signal to the threshold voltage V_TA comparison is made. When the amplified signal is higher than V_TIn time, pulse detection circuit 504 determines that the optical signal received from APD502 is indicative of a return optical pulse scattered by the remote target.

Fig. 12 illustrates an example receiver 140 configured to vary the gain at the gain circuit 512 over time. As discussed above with reference to fig. 11, the receiver 140 may include an APD502 coupled to a pulse detection circuit 504, the pulse detection circuit 504 having a TIA510, a gain circuit 512, a comparator 514, and a TDC 516. For ease of illustration only, the receiver 140 in fig. 12 is illustrated with a gain circuit 512 and a comparator 514. In other embodiments, receiver 140 may include APD502, TIA510, TDC 516, or any other suitable detector and/or pulse detection circuitry. In any case, to vary the gain over time, the controller 150 communicates with the receiver 140 via an electrical link 145. Controller 150And may also communicate directly with gain circuit 512 via electrical link 602. By communicating with receiver 140, controller 150 recognizes optical t₀And initializes the timer 604, the timer 604 may be a TDC, such as TDC 516. In other embodiments, controller 150 recognizes t when controller 150 provides a control signal or other trigger signal to light source 110 that causes it to emit a pulse of light, when light source 110 provides a signal to controller 150 that indicates that light source 110 has emitted a pulse of light, or in any other suitable manner₀. In these embodiments, t₀An event may be referred to as "electricity t₀”。

Then, as shown in the pulse timing diagram 610 of fig. 13, the controller 150 sends a "low" signal to the gain circuit 512 via the electrical link 602 for a threshold time period T1612. Referring to fig. 13, and with continued reference to fig. 12, in response to receiving a "low" signal, gain circuit 512 selects low gain G1 (e.g., 3dB) and applies low gain G1 to input voltage signal V_I. Input voltage signal V_IThe TIA510 may provide from the TIA510 to convert the current signal from the APD502 to a voltage signal, as shown in fig. 11. The output signal V is then amplified_OIs provided to a comparator circuit 514 to provide an amplified output signal V_OAnd a threshold voltage V_TA comparison is made to determine whether the received optical signal from APD502 is indicative of a return optical pulse scattered by a remote target.

When the threshold time period T1 ends (e.g., after 6.66ns), the controller 150 sends a "high" signal to the gain circuit 512 via the electrical link 602 for the threshold time period T2614, as shown in the pulse timing diagram 610. In response to receiving a "high" signal, gain circuit 512 selects high gain G2 (e.g., 30dB) and applies high gain G2 to input voltage signal V_I. Then when T2 ends, another light pulse is emitted to mark another T₀. Accordingly, the timer 604 is reset to 0 and the controller 150 again sends a "low" signal for the threshold time period T1612.

While the gain circuit 512 is shown as selecting between a low gain G1 and a high gain G2, this is merely one exemplary embodiment. In other embodiments, the gain of the gain circuit may gradually increase (e.g., linearly increase) from when a light pulse is transmitted until a subsequent light pulse is transmitted, or the gain may gradually increase during the threshold time period T2. Thus, controller 150 provides a gradually increasing control signal via electrical link 602 that causes gain circuit 512 to increase the gain. For example, the gain circuit 512 may be an operational amplifier with a variable resistor that increases in gain as the resistance of the variable resistor increases. Controller 150 provides a control signal to gain circuit 512 via electrical link 602, and gain circuit 512 controls the resistance of the variable resistor.

Example method to dynamically adjust gain in a laser radar system

Fig. 14 depicts a flow diagram of an example method 700 for dynamically adjusting gain in a laser radar system based on an amount of time that has elapsed since a light pulse was transmitted. The method may be implemented by various components of lidar system 100 shown in fig. 1, including light source 110, scanner 120, receiver 140, and controller 150. For ease of illustration only, some of the steps of method 700 may be described below with reference to particular components of laser radar system 100. However, each method step may be performed by any suitable component in any suitable manner. In some embodiments, the method or portions thereof may be implemented in a set of instructions stored on a computer-readable memory and executable on one or more processors or controllers 150.

At block 702, the light source 110 emits a pulse of light. In some embodiments, controller 150 directs optical source 110 to emit light pulses by providing instructions, control signals, or trigger signals to optical source 110 that indicate when optical source 110 should generate light pulses. Then, a light pulse having specific characteristics, such as a specific pulse rate or pulse repetition frequency, peak power, average power, pulse energy, pulse duration, wavelength, etc., is emitted.

At block 704, a timer is initialized to determine an amount of time that has elapsed since the light pulse was transmitted. The timer may be a time-to-digital converter (TDC), such as TDC 516 in the pulse detection circuit 504 shown in FIG. 11And when the controller 150 determines that a light pulse has been emitted, the controller 150 may reset or initialize the timer. When the controller 150 provides a control signal to the light source 110 to generate a light pulse (t)₀) At this time, the controller 150 may determine that a light pulse has been emitted. In other embodiments, the light pulses are emitted as they are (optical t)₀) Controller 150 determines that a light pulse has been emitted when a portion of light from the light pulse is scattered from within the lidar system housing and detected by receiver 140 (and more specifically APD 502).

At block 706, the emitted light pulses are directed via the scanner 120 toward a particular scan angle or direction relative to the forward direction of the vehicle. In this manner, the emitted light pulses are scanned in a horizontal FOR (e.g., from-60 degrees to +60 degrees relative to the forward direction of the vehicle). In some embodiments, the controller 150 provides drive signals to the scanner 120 to rotate the scanner mirror in the horizontal FOR to direct the light pulses to different points within the horizontal FOR. The emitted light pulses may also be directed in a vertical FOR (e.g., from-15 degrees vertical up to +15 degrees vertical) via the scanner 120. In some embodiments, the controller 150 provides drive signals to the scanner 120 to rotate the same scan mirror or another scan mirror in the vertical FOR to direct the light pulses to different points within the vertical FOR. FOR example, the scanner 120 may direct the optical pulses in a first vertical orientation (e.g., +15 degrees vertical) in a horizontal FOR to generate scan lines. The scanner 120 may then direct the optical pulse in a horizontal FOR in another vertical orientation (e.g., +14 degrees vertical) to generate another scan line.

At block 708, light from the light pulse is scattered by a remote target (such as target 130), as shown in FIG. 1, and detected by receiver 140, for example, to identify a return light pulse corresponding to the transmitted light pulse. The received optical signal is then processed, for example, by pulse detection circuitry 504 as shown in fig. 11, to identify characteristics of the received optical signal. The characteristics of the returned light pulses are then used to generate a point cloud having respective pixels.

More specifically, at block 710, an optical signal detected at APD502 is converted to an electrical signal. In some implementations, APD502 converts the optical signal to a current signal and transimpedance amplifier (TIA)510 in pulse detection circuit 504 converts the current signal to a voltage signal.

Then, based on the self-light pulse having been emitted (t)₀) The amount of time that has elapsed to determine the amount of amplification applied to the electrical signal (block 712). When coming from t₀When the later amount of elapsed time is within the threshold time period T1, the electrical signal is amplified by a first predetermined threshold amount (e.g., 3dB), which is below the threshold (block 714). In some embodiments, controller 150 provides a control signal to gain circuit 512 to operate in a low gain mode. When coming from t₀The electrical signal is amplified by a second predetermined threshold amount (e.g., 50dB) equal to or above the threshold when the later amount of time is within a threshold time period T2 after the threshold time period T1 ends (block 716). In some embodiments, controller 150 provides control signals to gain circuit 512 to operate in a high gain mode. Also in some embodiments, the optical t is identified based on the data used to identify the optical t₀The threshold time period T1 is dynamically adjustable. For example, when the duration of the detected light pulse exceeds a threshold duration, the controller 150 may increase the threshold time period T1. These characteristics may include a peak power of the detected light signal, an average power of the detected light signal, a pulse energy of the detected light signal, a pulse duration of the detected light signal, any other suitable characteristic of the detected light signal, or any suitable combination thereof.

In other embodiments, the amount of amplification may be set to a first predetermined threshold amount. When the optics t is recognized₀A timer is initialized and, after the timer is initialized, the amount of amplification is maintained at the first predetermined threshold amount for a threshold time period T1. The threshold time period T1 may be set to any suitable value, for example, 1ns, 2ns, 5ns, 10ns, 20ns, 50ns, or 100 ns.

Then, when the threshold time period T2 has elapsed, the light source 110 emits a subsequent light pulse. In some embodiments, controller 150 directs light source 110 to emit subsequent light pulses by providing instructions, control signals, or trigger signals to light source 110. The timer then resets to 0, the process repeats, and the gain circuit switches back to the low gain mode. However, this is only one example of how the gain varies over time. In other embodiments, the gain of the gain circuit may be gradually increased (e.g., linearly increased) from the time the light pulse is transmitted until a subsequent light pulse is transmitted until the threshold time period T2 has elapsed, or until a maximum predetermined gain is reached. For example, the gain may increase linearly until the gain reaches 50dB, and then the gain may remain constant for the remainder of the threshold time period T2. Thus, controller 150 provides a gradually increasing control signal via electrical link 602 that causes gain circuit 512 to increase the gain. For example, the gain circuit 512 may be an operational amplifier with a variable resistor that increases in gain as the resistance of the variable resistor increases. Controller 150 provides a control signal via electrical link 602 to gain circuit 512 which controls the resistance of the variable resistor. In other embodiments, the gain may increase over time, in a polynomial, exponential, logarithmic, quadratic, monotonic, etc. manner, or any suitable combination thereof, since the light pulse was emitted. In some embodiments, in the low gain mode, the gain may remain at a fixed gain value, while in the high gain mode, the gain may vary over time until a subsequent light pulse is transmitted until a threshold time period T2 has elapsed, or until a maximum predetermined gain is reached.

In other embodiments, the set of gain values in the low-gain and high-gain modes or the minimum and/or maximum gain values in the adjustable gain function may be determined based on a calibration technique. For example, during a calibration period in which laser radar system 100 ceases to emit light pulses, laser radar system 100 may generate a noise floor metric based on measurements performed by receiver 140 during the calibration period. Calibration may be performed periodically according to a fixed schedule or in response to a particular triggering event. In an example embodiment, lidar system 100 performs calibration in response to determining that the vehicle is stopped, and thus, data collection is less critical at this time. The noise floor metric may take into account both electrical noise from vehicle electronics and optical noise from ambient light. The set of gain values in the low-gain and high-gain modes or the minimum and/or maximum gain values in the adjustable gain function may be adjusted downward when the noise floor measure exceeds a certain threshold. The set of gain values in the low-gain and high-gain modes or the minimum and/or maximum gain values in the adjustable gain function may be adjusted upwards when the noise floor measure is below a certain threshold. Adjustments may be applied before laser radar system 100 is recalibrated.

In any case, the amplified signal may be related to the threshold voltage V_TAnd (6) comparing. When the amplified signal is higher than V_TIn time, pulse detection circuit 504 determines that the received optical signal from APD502 is indicative of a return optical pulse scattered by a remote target.

General theory of the invention

In some cases, a computing device may be used to implement the various modules, circuits, systems, methods, or algorithm steps disclosed herein. As one example, all or a portion of the modules, circuits, systems, methods, or algorithms disclosed herein may be implemented or performed with a general purpose single-or multi-chip processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA), any other suitable programmable logic device, discrete gate or transistor logic, discrete hardware components, or any suitable combination thereof. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

In particular embodiments, one or more implementations of the subject matter described herein may be implemented as one or more computer programs (e.g., one or more modules of computer program instructions encoded or stored on a computer-readable non-transitory storage medium). As one example, the steps of a method or algorithm disclosed herein may be embodied in a processor-executable software module, which may reside on a computer-readable non-transitory storage medium. In particular embodiments, a computer-readable non-transitory storage medium may include any suitable storage medium that can be used to store or transfer computer software and that can be accessed by a computer system. Herein, a computer-readable non-transitory storage medium or medium may include one or more semiconductor-based or other Integrated Circuits (ICs) (e.g., Field Programmable Gate Arrays (FPGAs) or Application Specific Integrated Circuits (ASICs)), Hard Disk Drives (HDDs), hybrid hard disk drives (HHDs), optical disks (e.g., Compact Disks (CDs), CD-ROMs, Digital Versatile Disks (DVDs), blu-ray disks, or laser disks), Optical Disk Drives (ODDs), magneto-optical disks, magneto-optical drives, floppy disks, Floppy Disk Drives (FDDs), magnetic tape, flash memory, Solid State Drives (SSDs), RAM drives, ROM, secure digital cards or drives, any other suitable computer-readable non-transitory storage medium, or a suitable combination of two or more of these, where appropriate. Computer-readable non-transitory storage media may be volatile, nonvolatile, or a combination of volatile and nonvolatile, where appropriate.

In some cases, certain features described herein in the context of separate implementations can also be combined and implemented in a single implementation. Conversely, various features that are described in the context of a single implementation can also be implemented in multiple implementations separately or in any suitable subcombination. Furthermore, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination.

Although operations may be described in the drawings as occurring in a particular order, it should not be understood that such operations are required to be performed in the particular order shown or in sequential order, or that all operations be performed. Further, the figures may schematically depict one or more example processes or methods in the form of a flow chart or sequence diagram. However, other operations not described may be incorporated into the example processes or methods illustrated schematically. For example, one or more other operations may be performed before, after, between, or concurrently with any of the illustrated operations. Further, one or more operations depicted in the figures may be repeated, where appropriate. In addition, the operations depicted in the figures may be performed in any suitable order. Further, although particular components, devices, or systems are described herein as performing particular operations, any suitable operations or combination of operations may be performed using any suitable combination of any suitable components, devices, or systems. In some cases, multitasking or parallel processing operations may be performed. Moreover, the separation of various system components in the implementations described herein should not be understood as requiring such separation in all implementations, and it should be understood that the described program components and systems can be integrated within a single software product or packaged into multiple software products.

Various embodiments have been described in connection with the accompanying drawings. It should be understood, however, that the drawings are not necessarily drawn to scale. As one example, the distances or angles shown in the figures are illustrative and do not necessarily have an exact relationship to the actual size or layout of the devices shown.

The scope of the present disclosure includes all changes, substitutions, variations, alterations, and modifications to the example embodiments described or illustrated herein that a person having ordinary skill in the art would comprehend. The scope of the present disclosure is not limited to the embodiments described or illustrated herein. Moreover, although the present disclosure describes or illustrates various embodiments herein as including particular components, elements, functions, operations, or steps, any of these embodiments may include any combination or permutation of any of the components, elements, functions, operations, or steps described or illustrated anywhere herein that a person having ordinary skill in the art would understand.

The term "or" as used herein is to be interpreted as including or meaning any one or any combination unless explicitly stated otherwise or the context clearly dictates otherwise. Thus, herein, the expression "a or B" means "A, B or both a and B". As another example, herein, "A, B or C" refers to at least one of: a; b; c; a and B; a and C; b and C; A. b and C. An exception to this definition will occur if a combination of elements, means, steps or operations are in some way mutually exclusive in nature.

Approximating language, such as, but not limited to, "approximate," "substantially," or "about," as used herein, refers to a condition that, when so modified, is not necessarily absolute or perfect, but would be considered sufficiently close to one of ordinary skill in the art to ensure that the specified condition exists. The extent to which the description may vary will depend on how much variation can be made and will enable one of ordinary skill in the art to recognize the modified feature as having the desired characteristics or capabilities of the unmodified feature. In general, but subject to the above discussion, numerical values modified herein by approximating words (e.g., "about") may vary by 0.5%, 1%, 2%, 3%, 4%, 5%, 10%, 12%, or 15% of the stated values.

As used herein, the terms "first," "second," "third," and the like may be used as labels before the terms, and these terms do not necessarily imply a particular order (e.g., a particular spatial, temporal, or logical order). As one example, the system may be described as determining a "first result" and a "second result," and the terms "first" and "second" may not necessarily mean that the first result is determined before the second result.

As used herein, the terms "based on" and "based, at least in part, on" may be used to describe or suggest one or more factors that affect a determination, and these terms do not exclude other factors that may affect a determination. The determination may be based entirely on those factors that were proposed, or at least in part on those factors. The phrase "determine a based on B" means that B is a factor that affects determination a. In some cases, other factors may also contribute to the determination of a. In other cases, a may be determined based on B only.