Object measurement for light detection and ranging system
阅读说明:本技术 光检测和测距系统的物体测量 (Object measurement for light detection and ranging system ) 是由 刘祥 王珂 洪小平 于 2017-06-30 设计创作,主要内容包括:公开了一种信号处理方法。所述方法包括由光检测和测距(LIDAR)装置(162)发射出射光脉冲(s1202);接收指示所述LIDAR装置的内部部件对所述出射光脉冲的反射的第一光脉冲(s1204);接收指示周围物体对所述出射光脉冲的反射的第二光脉冲(s1206);检测表示所述第一光脉冲的电子信号与表示所述第二光脉冲的电子信号之间的重叠(s1208);基于所述第二光脉冲的后沿部分中的第一定时信息来导出与所述第二光脉冲相关联的估计时间值(s1210);以及基于所述估计时间值来确定所述周围物体距所述LIDAR装置的距离(s1212)。(A signal processing method is disclosed. The method comprises emitting an outgoing light pulse (s1202) by a light detection and ranging (LIDAR) device (162); receiving a first light pulse indicative of a reflection of the outgoing light pulse by internal components of the LIDAR device (s 1204); receiving a second light pulse indicative of a reflection of the outgoing light pulse by a surrounding object (s 1206); detecting an overlap between an electronic signal representing the first light pulse and an electronic signal representing the second light pulse (s 1208); deriving an estimated time value associated with the second light pulse based on first timing information in a trailing portion of the second light pulse (s 1210); and determining a distance of the surrounding object from the LIDAR device based on the estimated time value (s 1212).)
1. A method, comprising:
emitting, by a light detection and ranging LIDAR device, an outgoing light pulse;
receiving, at the LIDAR device, a first light pulse indicative of a reflection of the outgoing light pulse by internal components of the LIDAR device;
receiving, at the LIDAR device, a second light pulse indicative of a reflection of the outgoing light pulse by a surrounding object;
deriving an estimated time value associated with the second light pulse based on first timing information in a trailing portion of the second light pulse in response to an overlap between an electronic signal representative of the first light pulse and an electronic signal representative of the second light pulse, wherein the overlap causes a loss of timing information in a leading portion of the second light pulse; and
determining a distance of the surrounding object from the LIDAR device based on the estimated time value associated with the second light pulse.
2. The method of claim 1, wherein the estimated time value is derived without missing timing information in the leading portion of the second light pulse.
3. The method of claim 1, wherein the first timing information in the trailing portion of the second light pulse corresponds to a first trigger threshold.
4. The method of claim 1, wherein the estimated time value associated with the second light pulse is derived further based on second timing information in the trailing portion of the second light pulse.
5. The method of claim 4, wherein the second timing information in the trailing portion of the second light pulse corresponds to a second trigger threshold different from the first trigger threshold.
6. The method of claim 1, wherein the estimated time value associated with the second light pulse is derived further based on peak information of the second light pulse.
7. The method of claim 1, wherein the estimated time value associated with the second light pulse is derived further based on available timing information in the leading portion of the second light pulse unaffected by the overlap.
8. The method of claim 1, wherein the estimated time value associated with the second light pulse is derived based on (1) second timing information in the trailing portion of the second light pulse and (2) peak information of the second light pulse.
9. The method of claim 8, wherein the estimated time value associated with the second light pulse is derived further based on available timing information in the leading portion of the second light pulse unaffected by the overlap.
10. The method of claim 1, further comprising:
timing information in a trailing portion of the first light pulse is determined.
11. The method of claim 10, further comprising: detecting the overlap based on the timing information in the trailing portion of the first light pulse.
12. The method of claim 1, wherein the estimated time value associated with the second light pulse is derived by fitting data including the first timing information in the trailing portion of the second light pulse to an analytical model.
13. The method of claim 12, wherein the estimated time value associated with the second light pulse is derived based on a shape of the analytical model.
14. The method of claim 1, wherein the estimated time value associated with the second light pulse corresponds to a predetermined signal amplitude.
15. The method of claim 14, wherein the predetermined signal amplitude is stored in a database or a look-up table.
16. A method, comprising:
emitting, by a light detection and ranging LIDAR device, an outgoing light pulse;
receiving, at the LIDAR device, a first light pulse indicative of a reflection of the outgoing light pulse by a first object;
receiving, at the LIDAR device, a second light pulse indicative of a reflection of the outgoing light pulse by a second object;
in response to an overlap between an electronic signal representing the first light pulse and an electronic signal representing the second light pulse, modeling the second light pulse based on first timing information in a given portion of the second light pulse, wherein the given portion of the second light pulse is outside of the overlap.
17. The method of claim 16 wherein the given portion of the second light pulse is a second half of the second light pulse.
18. The method of claim 16, wherein the first timing information in the given portion of the second light pulse corresponds to a first trigger threshold.
19. The method of claim 18, wherein the second light pulse is modeled further based on second timing information in the given portion of the second light pulse, the second timing information corresponding to a second trigger threshold that is different from the first trigger threshold.
20. The method of claim 16, further comprising:
in response to the overlap, modeling the first light pulse based on first timing information in a given portion of the first light pulse, wherein the given portion of the first light pulse is outside of the overlap.
21. The method of claim 20, wherein the given portion of the first light pulse is a first half portion of the first light pulse.
22. The method of claim 20, wherein the first timing information in the given portion of the first light pulse corresponds to a first trigger threshold.
23. The method of claim 20, wherein the first light pulse is modeled further based on second timing information in the given portion of the first light pulse, the second timing information corresponding to a second trigger threshold different from the first trigger threshold.
24. The method of claim 20, wherein the first light pulse is modeled using a first model and the second light pulse is modeled using a second model different from the first model.
25. A light detection and ranging system comprising:
a light emitter configured to emit an emitted light pulse;
a light sensor configured to:
detecting a first optical signal indicative of a reflection of the outgoing light pulse by an internal component of the system and generating a corresponding first electronic signal, an
Detecting a second optical signal indicative of a reflection of the outgoing light pulse by a surrounding object and generating a corresponding second electronic signal, the second electronic signal comprising a leading portion and a trailing portion; and
a controller coupled to the light sensor, the controller configured to: (1) deriving an estimated time value associated with a second light pulse based on first timing information in a trailing portion of the second light pulse in response to an overlap between an electronic signal representative of a first light pulse and an electronic signal representative of a second light pulse, wherein the overlap results in a loss of timing information in a leading portion of the second light pulse; and (2) determine a distance of the surrounding object from the LIDAR device based on the estimated time value associated with the second light pulse.
26. The system of claim 25, wherein the controller is configured to derive the estimated time value associated with the second light pulse without missing timing information in the leading portion of the second light pulse.
27. The system of claim 25, wherein the first timing information in the trailing portion of the second light pulse corresponds to a first trigger threshold.
28. The system of claim 25, wherein the controller is configured to derive the estimated time value associated with the second light pulse further based on second timing information in the trailing portion of the second light pulse.
29. The system of claim 28, wherein the second timing information in the trailing portion of the second light pulse corresponds to a second trigger threshold different from the first trigger threshold.
30. The method of claim 25, wherein the controller is configured to derive the estimated time value associated with the second light pulse further based on peak information of the second light pulse.
31. The system of claim 25, wherein the controller is configured to derive the estimated time value associated with the second light pulse further based on available timing information in the leading portion of the second light pulse unaffected by the overlap.
32. The system of claim 25, wherein the controller is configured to derive the estimated time value associated with the second light pulse based on (1) second timing information in the trailing portion of the second light pulse and (2) peak information of the second light pulse.
33. The system of claim 32, wherein the controller is configured to derive the estimated time value associated with the second light pulse further based on available timing information in the leading portion of the second light pulse unaffected by the overlap.
34. The system of claim 25, wherein the controller is configured to:
timing information in a trailing portion of the first light pulse is determined.
35. The system of claim 34, wherein the controller is configured to detect the overlap based on the timing information in the trailing portion of the first light pulse.
36. The system of claim 25, wherein the controller is configured to derive the estimated time value associated with the second light pulse by fitting data including the first timing information in the trailing portion of the second light pulse to an analytical model.
37. The system of claim 36, wherein the controller is configured to derive the estimated time value associated with the second light pulse based on a shape of the analytical model.
38. The method of claim 25, wherein the estimated time value associated with the second light pulse corresponds to a predetermined signal amplitude.
39. The method of claim 38, wherein the predetermined signal amplitude is stored in a database or a look-up table.
40. A light detection and ranging system comprising:
a light emitter configured to emit an emitted light pulse;
a light sensor configured to:
detecting a first optical signal indicative of a reflection of said outgoing light pulse by a first object and generating a corresponding first electronic signal, an
Detecting a second optical signal indicative of a reflection of the outgoing optical pulse by a second object and generating a corresponding second electronic signal; and
a controller coupled to the light sensor, the controller configured to: in response to an overlap between an electronic signal representing a first light pulse and an electronic signal representing a second light pulse, modeling a second light pulse based on first timing information in a given portion of the second light pulse, wherein the given portion of the second light pulse is outside of the overlap.
41. The system of claim 40 wherein the given portion of the second light pulse is a second half of the second light pulse.
42. The system of claim 40, wherein the first timing information in the given portion of the second light pulse corresponds to a first trigger threshold.
43. The system of claim 42, wherein the second light pulse is modeled based on second timing information in the given portion of the second light pulse, the second timing information corresponding to a second trigger threshold that is different from the first trigger threshold.
44. The system of claim 40, wherein the controller is configured to:
in response to the overlap, modeling the first light pulse based on first timing information in a given portion of the first light pulse, wherein the given portion of the first light pulse is outside of the overlap.
45. The system of claim 44 wherein the given portion of the first light pulse is a first half portion of the first light pulse.
46. The system of claim 44, wherein the first timing information in the given portion of the first light pulse corresponds to a first trigger threshold.
47. The system of claim 46, wherein the first light pulse is modeled based on second timing information in the given portion of the first light pulse, the second timing information corresponding to a second trigger threshold different from the first trigger threshold.
48. The system of claim 44, wherein the first light pulse is modeled using a first model and the second light pulse is modeled using a second model different from the first model.
Technical Field
The present disclosure relates generally to electronic signal processing, and more particularly, to components, systems, and techniques associated with signal processing in light detection and ranging (LIDAR) applications.
Background
With the ever-increasing performance and decreasing cost, unmanned vehicles are now widely used in many areas. Representative tasks include crop monitoring, real estate photography, inspection of buildings and other structures, fire and security tasks, border patrols, and product delivery, among others. For obstacle detection and other functions, it is beneficial for the unmanned vehicle to be equipped with obstacle detection and ambient scanning means. Light detection and ranging (LIDAR, also known as "light radar") provides reliable and accurate detection. However, current LIDAR systems cannot measure surrounding objects that are physically too close to the system due to limitations in the internal structure of the LIDAR. Accordingly, there remains a need for improved techniques for implementing LIDAR systems carried by unmanned vehicles and other objects.
Disclosure of Invention
The present disclosure relates to components, systems, and techniques associated with signal processing in light detection and ranging (LIDAR) applications.
In one exemplary aspect, a method of signal processing is disclosed. The method comprises the following steps: emitting, by a light detection and ranging (LIDAR) device, an outgoing light pulse; receiving, at the LIDAR device, a first light pulse indicative of a reflection of the outgoing light pulse by internal components of the LIDAR device; receiving, at the LIDAR device, a second light pulse indicative of a reflection of the outgoing light pulse by a surrounding object; detecting or observing an overlap between an electronic signal representing the first light pulse and an electronic signal representing the second light pulse, wherein the overlap results in a loss of timing information in a leading portion of the second light pulse; deriving, in response to the overlapping, an estimated time value associated with the second light pulse based on first timing information in a trailing portion of the second light pulse; and determining a distance of the surrounding object from the LIDAR device based on the estimated time value associated with the second light pulse.
In another exemplary aspect, a method of signal processing is disclosed. The method comprises the following steps: emitting, by a light detection and ranging (LIDAR) device, an outgoing light pulse; receiving, at the LIDAR device, a first light pulse indicative of a reflection of the outgoing light pulse by a first object; receiving, at the LIDAR device, a second light pulse indicative of a reflection of the outgoing light pulse by a second object; detecting an overlap between an electronic signal representing the first light pulse and an electronic signal representing the second light pulse; and in response to detecting the overlap, modeling the second light pulse based on first timing information in a given portion of the second light pulse, wherein the given portion of the second light pulse is outside of the overlap.
In another exemplary aspect, a light detection and ranging system is disclosed. The system comprises: a light emitter configured to emit an emitted light pulse; and a light sensor configured to: detecting a first optical signal indicative of a reflection of the outgoing light pulse by internal components of the system and generating a corresponding first electronic signal, and detecting a second optical signal indicative of a reflection of the outgoing light pulse by a surrounding object and generating a corresponding second electronic signal. The second electronic signal includes a leading portion and a trailing portion. The system also includes a controller coupled to the light sensor, the controller configured to: (1) detecting an overlap between an electronic signal representing a first light pulse and an electronic signal representing a second light pulse, wherein the overlap results in a loss of timing information in a leading portion of the second light pulse, (2) in response to detecting the overlap, deriving an estimated time value associated with the second light pulse based on first timing information in a trailing portion of the second light pulse, and (3) determining a distance of the surrounding object from the LIDAR device based on the estimated time value associated with the second light pulse.
In yet another exemplary aspect, a light detection and ranging system is disclosed. The system comprises: a light emitter configured to emit an emitted light pulse; and a light sensor configured to: detecting a first optical signal indicative of a reflection of the outgoing light pulse by a first object and generating a corresponding first electronic signal, and detecting a second optical signal indicative of a reflection of the outgoing light pulse by a second object and generating a corresponding second electronic signal. The system also includes a controller coupled to the light sensor, the controller configured to: (1) detecting an overlap between an electronic signal representing a first light pulse and an electronic signal representing a second light pulse, and (2) in response to detecting the overlap, modeling the second light pulse based on first timing information in a given portion of the second light pulse, wherein the given portion of the second light pulse is outside of the overlap.
The above and other aspects and embodiments thereof are described in more detail in the accompanying drawings, the detailed description and the claims.
Drawings
FIG. 1A is a schematic diagram of a representative system having a movable object (e.g., an unmanned aerial vehicle) with a plurality of elements configured in accordance with one or more embodiments of the present technique.
Fig. 1B illustrates a schematic diagram of an exemplary LIDAR sensor system, according to various embodiments of the invention.
Fig. 2A is a simplified diagram illustrating the basic operating principle of a comparator-based sampling method.
Fig. 2B is a diagram of the input and output waveforms of the pulse signal before and after the comparator.
Fig. 3 shows a schematic diagram of a zero signal, an overlap signal reflected by an object located in a region close to the LIDAR system, and a conventional signal reflected by an object located outside the blind spot region.
Fig. 4 shows a schematic diagram of a zero signal, two overlapping signals reflected by objects located in the blind spot region of the LIDAR system, and two conventional signals reflected by objects located outside the blind spot region.
Fig. 5 shows an example of a timing error caused by the broadening of the pulse signal.
FIG. 6 is a schematic diagram of a comparator module having a multiple comparator structure in accordance with embodiments of the present technique.
Fig. 7 is a graphical representation of obtaining multiple sample points of a pulse signal using a multiple comparator structure.
Fig. 8 is a schematic diagram of a peak hold circuit in accordance with embodiments of the present technique.
Fig. 9 is a graphical representation of obtaining multiple sample points of a pulse signal using a multiple comparator structure and a peak hold circuit.
Fig. 10 illustrates an example of a partially overlapping signal where the overlap region is below at least one of a plurality of threshold voltage levels.
Fig. 11A shows an example of an overlap signal.
Fig. 11B shows another example of an overlap signal.
Fig. 11C shows still another example of an overlap signal.
Fig. 12 is a flowchart representation of a method of signal processing for a LIDAR sensor system.
Fig. 13 is a flow chart representation of another method of signal processing for a LIDAR sensor system.
Detailed Description
As introduced above, it is important for an unmanned vehicle to be able to independently detect obstacles and/or automatically maneuver into maneuver avoidance. Light detection and ranging (LIDAR) is a reliable and accurate detection technique. Furthermore, unlike conventional image sensors (e.g., cameras) that are only capable of sensing the surrounding environment in two dimensions, LIDAR may obtain three-dimensional information by detecting depth. However, current LIDAR systems have their limitations. For example, as discussed in more detail below, many LIDAR systems include internal optical components that can reflect the emitted light signals. Reflected signals from internal components may interfere with optical signals reflected by surrounding objects located near the system. It should be noted that many LIDAR systems are not able to accurately measure surrounding objects that are physically too close to the system due to such reflected signals from internal components. Accordingly, there remains a need for improved techniques for implementing LIDAR systems that enable LIDAR systems to accurately measure objects at shorter distances. The techniques disclosed herein allow a LIDAR system to recognize that a light signal is disturbed, and based on that recognition, more accurately measure surrounding objects at close distances by using additional data samples from the light signal.
In the following description, for illustrative purposes only, the example of a UAV is used to explain various techniques that may be implemented using a LIDAR scanning module that is less expensive and more lightweight than conventional LIDAR. In other embodiments, the techniques described herein are applicable to other suitable scan modules, vehicles, or both. For example, although one or more of the figures described in connection with these techniques illustrate a UAV, in other embodiments, these techniques are applicable in a similar manner to other types of movable objects, including but not limited to unmanned vehicles, hand-held devices, or robots. In another example, although the techniques are particularly applicable to laser beams generated by laser diodes in LIDAR systems, in other embodiments they may be applicable to other types of light sources (e.g., other types of lasers or Light Emitting Diodes (LEDs)).
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the presently disclosed technology. In other embodiments, the techniques described herein may be practiced without these specific details. In other instances, well-known features, such as specific manufacturing techniques, are not described in detail in order to avoid unnecessarily obscuring the present disclosure. Reference in the specification to "an embodiment," "one embodiment," or the like means that a particular feature, structure, material, or characteristic described is included in at least one embodiment of the disclosure. Thus, appearances of such phrases in various places throughout this specification are not necessarily all referring to the same embodiment. On the other hand, such references are not necessarily mutually exclusive. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments. Furthermore, it should be understood that the various embodiments shown in the figures are merely illustrative representations and are not necessarily drawn to scale.
In this disclosure, the word "exemplary" is used to mean serving as an example, instance, or illustration. Any embodiment or design described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments or designs. Rather, use of the word exemplary is intended to present concepts in a concrete fashion.
FIG. 1A is a schematic diagram of a
The
The one or
The
Fig. 1B illustrates a schematic diagram of an exemplary LIDAR sensor system, in accordance with various embodiments of the disclosed technology. For example, the LIDAR sensor system 100 may detect the distance of the
The
The
To successfully capture very short pulse signals (e.g., pulse durations of only tens of nanoseconds to a few nanoseconds), many LIDAR systems rely on high-speed analog-to-digital converters (ADCs) (e.g., sampling rates in excess of one gigasample per second (GSPS)) to perform digitization of the optical pulse signals. High speed ADCs typically have high cost and high power consumption. Furthermore, high-speed ADC sampling is based on sampling analog signals having different voltages at the same time interval (i.e., sampling with respect to a time axis). Thus, the timing of the sampling is independent of the pulse signal and does not have any time dependency. An extraction algorithm is required to extract the timing information of the analog signal.
Another alternative solution is to collect timing information of the reflected pulse signal in the LIDAR system using comparator-based sampling. Fig. 2A is a simplified diagram illustrating the basic operating principle of a comparator-based sampling method. The method is based on the timing when the analog signal crosses a particular threshold (also referred to herein as a "reference threshold" or "trigger threshold"). As shown in the example of fig. 2A, the
Whether the LIDAR system employs an ADC-based sampling mechanism or a comparator-based sampling mechanism, there are limitations in the LIDAR that prevent the LIDAR from accurately measuring surrounding objects that are in physical proximity to the LIDAR system. In particular, due to the internal structure of the LIDAR sensor system (e.g., the
Fig. 3 shows a schematic diagram of signals detected by the LIDAR system, namely a
In this example shown in fig. 3, the
Fig. 3 also shows an
Further, it should be noted that the actual shape of the pulse signal in the reflected light will be affected by a variety of environmental factors, such as noise (e.g., ambient light noise and/or electronic noise as described below), the distance of the target object, the surface and color of the target object, and so forth. It has been observed that surface properties of objects can have a large effect on the amplitude of the pulse signal and affect the accuracy of the timing information.
Fig. 4 shows a schematic diagram of a zero
Fig. 4 also shows two
Other types of timing errors may be caused by internal circuitry of the LIDAR sensor system. For example, a pulse signal having a large amplitude may be expanded and/or widened after the pulse signal is processed by some internal amplification circuitry of the LIDAR system. Fig. 5 shows an example of a timing error caused by the broadening of the pulse signal. In this example, the
To account for inaccuracies in object measurements caused by information loss in the leading portion of the reflected signal, embodiments of the LIDAR sensor systems disclosed herein may increase the effective sampling rate of the signal to obtain more data. In particular, the LIDAR sensor system may obtain multiple samples in portions outside of the overlap region of the pulse signals (e.g., in the trailing portion) in order to determine the shape of the pulse signals and/or the relevant timing information of the signals.
For example, in a comparator-based LIDAR sensor system, multiple comparators may be used to obtain more samples from the trailing portion of the signal. FIG. 6 is a schematic diagram of a comparator module having a multiple comparator structure in accordance with embodiments of the present technique. The multi-comparator architecture includes two or more comparators, each coupled to the same input to perform timing measurements on the same light pulse, but each having a different trigger threshold. In this example, the
Fig. 7 is a graphical representation of obtaining multiple sample points of a pulse signal using a multiple comparator structure. In this particular example, for a
In some embodiments, the controller may fit the data samples to an analytical model, such as a polynomial model or a trigonometric model. The controller may then derive an estimated time value (e.g., time value T as shown in fig. 7) based on the shape of the analytical model. For example, the controller may select the time value T by checking when the signal amplitude reaches its maximum value. In some embodiments, the controller may use other criteria (e.g., the width of the signal in the rectangular signal model) to derive an estimated time value associated with the pulse signal for which TOF calculations are made in order to determine the distance of the corresponding object from the LIDAR system.
In some embodiments, the controller may search a database or look-up table to find the set of values that most closely match the data sample. The set of values may have (t)i,Vfi) Of the form (b), wherein VfiCorresponding to the threshold level. The set of values may be mapped to an output time value or output tuple of the form (T, V) stored in a database or look-up table. V may correspond to one of the threshold levels. In some embodiments, V may be a predetermined signal amplitude that is different from the threshold level. The controller may then select the mapped output time value or select a T corresponding to V from the mapped output tuple to calculate TOF to determine the distance of the corresponding object from the LIDAR system.
Similarly, the controller may perform the same task for the four data samples (t13, vf04), (t14, vf03), (t15, vf02), and (t16, vf01) to obtain a more accurate model or statistic of the pulse signal, thereby minimizing the effect of signal amplitude and/or broadening of the signal on object measurement accuracy.
In some embodiments, the controller may infer the pulse signal amplitude from multiple data samples of timing information. For example, after fitting the samples (t13, vf04), (t14, vf03), (t15, vf02), and (t16, vf01) to a signal model (e.g., a parabolic model), the controller may estimate the magnitude of the signal. However, in some embodiments, because the samples are limited to the trailing portion of the pulse signal, the estimate of the signal amplitude may be less accurate (for the reasons described above). Therefore, it is desirable to measure the amplitude of the signal separately to provide more information.
Fig. 8 is a schematic diagram of a peak hold circuit in which the peak hold circuit can detect the amplitude of a pulse signal in accordance with an embodiment of the present technique. The peak hold circuit 800 includes a peak hold core 810, the peak hold core 810 including a diode D2, a resistor R2, and a capacitor C1. The peak hold circuit 800 also includes a first operational amplifier 802 and a second operational amplifier 804. In some embodiments, the first operational amplifier 802 receives the signal and passes the signal to the peak-hold core 810, which in turn passes the signal to the second operational amplifier 804 by the peak-hold core 810.
Such a peak-hold circuit 800 is superior to a conventional peak-hold circuit in its ability to capture peak information of a very short pulse signal (e.g., tens of nanoseconds to a few nanoseconds) and in its ability to continuously capture peak information without requiring a relatively long recovery time (e.g., 20 to 30 nanoseconds). In some variations, the first operational amplifier 802 may be omitted depending on the design of the entire circuit of the LIDAR system. In some embodiments where the peak value of the negative amplitude signal is to be maintained, the reference signal may be slightly larger than the steady state voltage of the system to reduce the measurement dead band caused by the voltage drop from diode D2. Similarly, in some embodiments where the peak value of the positive amplitude signal is to be maintained, the reference signal may be slightly less than the steady state voltage of the system to reduce the measurement dead band caused by the voltage drop from diode D2.
Fig. 9 is a graphical representation of the use of a multiple comparator structure and a peak hold circuit to obtain multiple sample points of a pulse signal. In this particular example, similar to the example shown in fig. 7, for a conventional pulse signal 901, eight samples (e.g., t1 through t8) of timing information may be obtained for four different threshold levels (e.g., Vf01 through Vf 04). For signals that partially overlap with the zero signal 903, four samples in the trailing portion can be obtained using a multi-comparator structure. In addition, a peak hold circuit may be used to obtain the amplitude of the pulse signal. For example, after obtaining five data samples (t9, vf04), (t10, vf03), (t11, vf02), (t12, vf01), and p1 of the signal 907, the controller may fit multiple samples to the pulse signal model, or compare samples of the pulse signal to pre-existing statistical data stored on a database or lookup table, to determine the distance of the corresponding object from the LIDAR system.
In some embodiments, the controller may fit the data samples to an analytical model, such as a polynomial model or a trigonometric model. The controller may derive the estimated time value T based on a shape of the analytical model. For example, the controller may select the time value T by checking when the signal amplitude reaches a value obtained by a peak hold circuit. In some embodiments, the controller may use other criteria (e.g., the width of the signal in the rectangular signal model) to derive an estimated time value associated with the pulse signal for which TOF calculations are made in order to determine the distance of the corresponding object from the LIDAR system.
In some embodiments, the controller may search a database or look-up table to find the set of values that most closely match the data sample. The set of values may have (t)i,Vfi) Of the form (b), wherein VfiCorresponding to the threshold level. The set of values may be mapped to an output time value or output tuple of the form (T, V) stored in a database or look-up table. V may correspond to one of the threshold levels. In some embodiments, V may be a predetermined signal amplitude that is different from the threshold level. The controller may then select the mapped output time value or select a T corresponding to V from the mapped output tuple to calculate TOF to determine the distance of the corresponding object from the LIDAR system.
The controller may perform the same task for five data samples (t13, vf04), (t14, vf03), (t15, vf02), (t16, vf01), and p2 to obtain a more accurate model or statistic of the pulse signal 905 to minimize the effect of signal amplitude and/or broadening of the signal on object measurement accuracy.
In some cases, the leading portion of the reflected pulse signal may still contain valid timing information even if the object is located within the blind spot region of the LIDAR sensor system. For example, fig. 10 shows an example of a partially overlapping signal where the overlap region does not affect the comparator at one or more of the multiple threshold voltage levels. In this example, the zero signal 1001 has a relatively small amplitude. Thus, although it is difficult for the comparator to discern when the signal magnitudes of the signals 1003 and 1005 exceed the threshold levels Vf01 and Vf02, resulting in the loss of the timing information t0 through t1 and t2 through t3, the comparator is still able to obtain the timing information carried in the remaining portions of the leading edge portions of the signals 1003 and 1005, e.g., t3, t4, t5, and t6, for the threshold voltage levels Vf03 and Vf 04.
Thus, for signal 1003, the controller may add additional timing information (e.g., t5, t6) from the leading portion to the data samples (e.g., t7, t8, t9, and t10) and magnitude (e.g., p1) in the trailing portion. It may fit multiple samples to the pulse signal model or compare this information to pre-existing statistical data stored on a database or look-up table to determine the distance of the corresponding object from the LIDAR system. Similarly, for signal 1005, the controller may add additional timing information (e.g., t3 and t4) from the leading portion to the data samples (e.g., t11, t12, t13, and t14) and amplitudes (e.g., p2) in the trailing portion to obtain a more accurate model or statistic of the pulse signal to minimize the effect of signal amplitude and broadening of the signal on object detection accuracy.
The above specific configuration is made to explain an example of processing a signal overlapping with a zero signal. However, it should be understood that the same techniques may be broadly applied to other types of signal overlap scenarios. For example, the first signal is not limited to a zero signal, and may be a pulse signal reflected from another surrounding object.
Based on the timing information obtained using the techniques disclosed herein, the controller may model the pulse signal using an analytical model (e.g., a triangular model or a parabolic model). In some embodiments, the controller may also model the pulse signal using one or more different models, for different pulse signals or for the same pulse signal. Fig. 11A to 11C show various examples of the superimposed signal. In these examples, the obtained timing information is from both the interfering signal (e.g., the null signal) and the target signal. Because the timing information is not directly related to the target signal, it is desirable to establish multiple submodels in different time intervals to more accurately describe the target signal as well as the interfering signal.
For example, in fig. 11A, the controller obtains four timing samples (e.g., t 1-t 4) of the
Fig. 11B shows another example of an overlap signal. Because the amplitude of the
Fig. 11C shows still another example of an overlap signal. In this example, the controller obtains five timing samples (e.g., t 1-t 5) of the first pulse signal 1121 in both the leading portion and the trailing portion. Also, because the signals interfere with each other, the controller cannot obtain accurate timing information in the overlap region, making it difficult for the comparator to tell when the amplitude of the pulse signal exceeds the threshold level. The controller then obtains three timing samples (e.g., t 6-t 8) of the second pulse signal 1123 (i.e., the target signal). Since the timed samples come from two separate pulse signals and form complex shapes, it is also desirable to model them separately using two simple sub-models in different time intervals.
The eight samples obtained in the above scenario may fit the function as one input set x ═ {
the controller then determines a of the functionij、biAnd ciTo describe the pulse signal. In some cases (e.g., the examples shown in fig. 11A-11C), the input x is collected from different multiple signals and does not correlate well with a simple model. Thus, it is desirable to divide the input into two or more sets. For example, in the case shown in fig. 11A, two separate models may be built using the two sets x1 ═ { t 1., t4} and x2 ═ t 5., t8 }. In the case shown in fig. 11B, two different models may be obtained using the two sets X1 ═ { t1, t2, t3} and X2 ═ t4, …, t8 }. Similarly, in the case depicted in fig. 11C, the input may be divided into X1 ═ {
Fig. 12 is a flowchart representation of a method of signal processing for a LIDAR sensor system. The method 1200 includes: at 1202, emitting, by a light detection and ranging (LIDAR) device, an outgoing light pulse; at 1204, receiving, at the LIDAR device, a first light pulse indicative of a reflection of the outgoing light pulse by an internal component of the LIDAR device; at 1206, receiving, at the LIDAR device, a second light pulse indicative of a reflection of the outgoing light pulse by a surrounding object; at 1208, detecting an overlap between the electronic signal representing the first light pulse and the electronic signal representing the second light pulse, wherein the overlap results in a loss of timing information in a leading portion of the second light pulse; at 1210, in response to detecting the overlap, deriving an estimated time value associated with the second light pulse based on the first timing information in the trailing portion of the second light pulse; and at 1212, determining a distance of a surrounding object from the LIDAR device based on the estimated time value associated with the second light pulse.
In some embodiments, the estimated time value is derived without missing timing information in the leading portion of the second light pulse. The first timing information in the trailing portion of the second light pulse corresponds to a first trigger threshold. In some embodiments, the estimated time value associated with the second light pulse is also derived based on second timing information in a trailing portion of the second light pulse. The second timing information in the trailing portion of the second light pulse corresponds to a second trigger threshold that is different from the first trigger threshold.
In some embodiments, an estimated time value associated with the second light pulse is also derived based on peak information of the second light pulse. An estimated time value associated with the second light pulse may also be derived based on the available timing information unaffected by the overlap in the leading portion of the second light pulse.
In some embodiments, an estimated time value associated with the second light pulse is derived based on (1) second timing information in a trailing portion of the second light pulse and (2) peak information of the second light pulse. An estimated time value associated with the second light pulse may also be derived based on the available timing information unaffected by the overlap in the leading portion of the second light pulse.
In some embodiments, the method further comprises determining timing information in a trailing portion of the first light pulse. The overlap is detected based on timing information in a trailing portion of the first light pulse.
In some embodiments, the estimated time value associated with the second light pulse is derived by fitting data including the first timing information in the trailing portion of the second light pulse to an analytical model. An estimated time value associated with the second light pulse is derived based on the shape of the analytical model.
In some embodiments, the estimated time value associated with the second light pulse corresponds to a predetermined signal amplitude. The predetermined signal amplitudes are stored in a database or look-up table.
Fig. 13 is a flow chart representation of another method of signal processing for a LIDAR sensor system. The
In some embodiments, the given portion of the second light pulse is the second half of the second light pulse. The first timing information in the given portion of the second light pulse corresponds to a first trigger threshold.
In some embodiments, the second light pulse is also modeled based on second timing information in the given portion of the second light pulse. The second timing information corresponds to a second trigger threshold that is different from the first trigger threshold.
In some embodiments, the method further comprises: in response to detecting the overlap, the first light pulse is modeled based on first timing information in a given portion of the first light pulse, wherein the given portion of the first light pulse is outside of the overlap. The given portion of the first light pulse may be a first half of the first light pulse. The first timing information in the given portion of the first light pulse corresponds to a first trigger threshold.
In some embodiments, the first light pulse is also modeled based on second timing information in a given portion of the first light pulse, the second timing information corresponding to a second trigger threshold that is different from the first trigger threshold. The first light pulse may be modeled using a first model and the second light pulse may be modeled using a second model different from the first model.
It is therefore apparent that in one exemplary aspect there is provided a light detection and ranging system comprising: a light emitter configured to emit an emitted light pulse; and a light sensor configured to detect a first light signal indicative of a reflection of the outgoing light pulse by internal components of the system and generate a corresponding first electronic signal, and to detect a second light signal indicative of a reflection of the outgoing light pulse by a surrounding object and generate a corresponding second electronic signal. The second electronic signal includes a leading portion and a trailing portion. The system also includes a controller coupled to the light sensor configured to: (1) detecting an overlap between an electronic signal representing a first light pulse and an electronic signal representing a second light pulse, wherein the overlap results in a loss of timing information in a leading portion of the second light pulse, (2) in response to detecting the overlap, deriving an estimated time value associated with the second light pulse based on the first timing information in a trailing portion of the second light pulse, and (3) determining a distance of a surrounding object from the LIDAR device based on the estimated time value associated with the second light pulse.
In some embodiments, the controller is configured to derive the estimated time value associated with the second light pulse without missing timing information in the leading portion of the second light pulse. The first timing information in the trailing portion of the second light pulse corresponds to a first trigger threshold.
In some embodiments, the controller is configured to derive the estimated time value associated with the second light pulse further based on second timing information in a trailing portion of the second light pulse. The second timing information in the trailing portion of the second light pulse corresponds to a second trigger threshold that is different from the first trigger threshold.
In some embodiments, the controller is configured to derive the estimated time value associated with the second light pulse further based on peak information of the second light pulse. The controller may be configured to derive the estimated time value associated with the second light pulse further based on available timing information unaffected by the overlap in the leading portion of the second light pulse.
In some embodiments, the controller is configured to derive an estimated time value associated with the second light pulse based on (1) the second timing information in the trailing portion of the second light pulse and (2) the peak information of the second light pulse. The controller is configured to derive an estimated time value associated with the second light pulse further based on the available timing information unaffected by the overlap in the leading portion of the second light pulse.
In some embodiments, the controller is configured to determine timing information in a trailing portion of the first light pulse. The overlap may be detected based on timing information in a trailing portion of the first light pulse.
In some embodiments, the controller is configured to derive the estimated time value associated with the second light pulse by fitting data comprising the first timing information in the trailing portion of the second light pulse to the analytical model. The controller is configured to derive an estimated time value associated with the second light pulse based on a shape of the analytical model.
In some embodiments, the estimated time value associated with the second light pulse corresponds to a predetermined signal amplitude. The predetermined signal amplitudes are stored in a database or look-up table.
It will also be apparent that in another exemplary aspect, there is provided a light detection and ranging system comprising: a light emitter configured to emit an emitted light pulse; a light sensor configured to detect a first light signal indicative of a reflection of the outgoing light pulse by a first object and generate a corresponding first electronic signal, and to detect a second light signal indicative of a reflection of the outgoing light pulse by a second object and generate a corresponding second electronic signal; and a controller coupled to the light sensor, configured to: (1) detecting an overlap between an electronic signal representing a first light pulse and an electronic signal representing a second light pulse, and (2) in response to detecting the overlap, modeling the second light pulse based on first timing information in a given portion of the second light pulse, wherein the given portion of the second light pulse is outside of the overlap.
In some embodiments, the given portion of the second light pulse is the second half of the second light pulse. The first timing information in the given portion of the second light pulse corresponds to a first trigger threshold.
In some embodiments, the second light pulse is modeled based on second timing information in a given portion of the second light pulse, the second timing information corresponding to a second trigger threshold that is different from the first trigger threshold.
In some embodiments, the controller is configured to model the first light pulse based on first timing information in a given portion of the first light pulse in response to detecting the overlap, wherein the given portion of the first light pulse is outside the overlap. The given portion of the first light pulse is a first half of the first light pulse. The first timing information in the given portion of the first light pulse corresponds to a first trigger threshold.
In some embodiments, the first light pulse is also modeled based on second timing information in a given portion of the first light pulse, the second timing information corresponding to a second trigger threshold that is different from the first trigger threshold. The first light pulse may be modeled using a first model and the second light pulse may be modeled using a second model different from the first model.
Some embodiments described herein are described in the general context of methods or processes, which may be implemented in one embodiment by a computer program product, embodied in a computer-readable medium, containing computer-executable instructions, such as program code, executed by computers in networked environments. The computer-readable medium may include removable and non-removable storage devices including, but not limited to, Read Only Memory (ROM), Random Access Memory (RAM), Compact Discs (CDs), Digital Versatile Discs (DVDs), and the like. Thus, a computer-readable medium may include a non-transitory storage medium. Generally, program modules may include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types. Computer-or processor-executable instructions, associated data structures, and program modules represent examples of program code for executing steps of the methods disclosed herein. The particular sequence of such executable instructions or associated data structures represents examples of corresponding acts for implementing the functions described in such steps or processes.
Some disclosed embodiments may be implemented as a device or module using hardware circuitry, software, or a combination thereof. For example, a hardware circuit implementation may include discrete analog and/or digital components integrated, for example, as part of a printed circuit board. Alternatively or additionally, the disclosed components or modules may be implemented as Application Specific Integrated Circuit (ASIC) and/or Field Programmable Gate Array (FPGA) devices. Some embodiments may additionally or alternatively include a Digital Signal Processor (DSP) as a special-purpose microprocessor having an architecture optimized for the operational requirements of digital signal processing associated with the disclosed functionality of the present application. Similarly, various components or sub-components within each module may be implemented in software, hardware, or firmware. Connections between modules and/or between components within modules may be provided using any of a variety of connection methods and media known in the art, including, but not limited to, communications over the internet, wired, or wireless networks using an appropriate protocol.
While this patent document contains many specifics, these should not be construed as limitations on the scope of any invention or of what may be claimed, but rather as descriptions of features that may be specific to particular embodiments of particular inventions. Certain features that are described in this patent document in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments 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.
Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. Moreover, the separation of various system components in the embodiments described in this patent document should not be understood as requiring such separation in all embodiments.
Only a number of embodiments and examples are described and other embodiments, enhancements and variations can be made based on what is described and illustrated in this patent document.
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