阅读说明：本技术 激光雷达测量方法及激光雷达系统 (Laser radar measuring method and laser radar system ) 是由 张鑫 屈志巍 徐洋 于 2019-10-21 设计创作，主要内容包括：本发明提供一种激光雷达测量方法及激光雷达系统,通过可调谐激光产生单元产生波长可调谐的输出光信号；对输出光信号进行线性调频得到调频连续波信号；对调频连续波信号分束获得出射光信号和本振光信号；将出射光信号经功率放大后由光学相控阵发射单元发射,对目标物体的二维扫描；接收被目标物体反射的回波光信号,根据回波光信号与本振光信号获取目标物体的距离和/或速度信息。将可调谐激光和光学相控阵体系结合,在一维光学相控阵器件的基础上实现二维扫描,避免一维光学相控阵器件采用堆叠形式实现二维扫描；通过采用外调制方式,实现将光学相控阵和宽带可调谐激光器与调频连续波体制合理结合,克服宽带可调谐激光器难以窄带线性调频的不足。(The invention provides a laser radar measuring method and a laser radar system, wherein a tunable laser generating unit is used for generating an output optical signal with tunable wavelength; carrying out linear frequency modulation on the output optical signal to obtain a frequency modulation continuous wave signal; splitting the frequency modulated continuous wave signal to obtain an emergent light signal and a local oscillation light signal; emitting the emergent light signals after power amplification by an optical phased array emitting unit, and carrying out two-dimensional scanning on a target object; and receiving the echo optical signal reflected by the target object, and acquiring the distance and/or speed information of the target object according to the echo optical signal and the local oscillator optical signal. The tunable laser and the optical phased array system are combined, two-dimensional scanning is realized on the basis of a one-dimensional optical phased array device, and the one-dimensional optical phased array device is prevented from realizing two-dimensional scanning in a stacking mode; by adopting an external modulation mode, the optical phased array, the broadband tunable laser and the frequency modulation continuous wave system are reasonably combined, and the defect that the broadband tunable laser is difficult to realize narrow-band linear frequency modulation is overcome.)

1. A lidar measurement method comprising:

generating an output optical signal with tunable wavelength by a tunable laser generation unit;

carrying out linear frequency modulation on the output optical signal to obtain a frequency modulated continuous wave signal;

splitting the frequency modulated continuous wave signal to obtain an emergent light signal and a local oscillation light signal;

after the emergent light signals are amplified in power, the emergent light signals are transmitted through an optical phased array transmitting unit, and the two-dimensional scanning of the optical phased array on a target object is achieved;

and after receiving the echo optical signal reflected by the target object, acquiring the distance and/or speed information of the target object according to the echo optical signal and the local oscillator optical signal.

2. The method of claim 1, wherein the optical phased array transmission unit comprises a waveguide grating structure;

the emission through optical phased array emission unit realizes the two-dimensional scanning to the target object, includes:

controlling the wavelength of an output optical signal through the tunable laser generation unit to control the wavelength of the outgoing optical signal so that the optical phased array emission unit scans in a first dimension;

the emergent light signals are divided by the optical phased array and emitted from the waveguide grating structure, and the main large angle after the interference of the emergent light signals is controlled by controlling the phase of the emergent light signals, so that the optical phased array emission unit scans in the second dimension.

3. The method of claim 2, wherein said emitting by an optical phased array emitting unit, effecting a two-dimensional scan of the target object, comprises:

sequentially generating output optical signals with different wavelengths through the tunable laser generating unit, and continuously outputting the output optical signals with each wavelength for a preset time length so as to sequentially change the emergent angle of the emergent optical signals on the first dimension;

at least one scan in a second dimension is performed by the optical phased array transmission unit for each of the preset durations.

4. The method of claim 3, wherein said chirping the output optical signal to obtain a frequency modulated continuous wave signal comprises:

and performing narrow-band chirp on the output optical signal, wherein the wavelength fluctuation range caused by narrow-band chirp modulation is smaller than the wavelength difference between adjacent wavelengths when the tunable laser performs wavelength switching.

5. The method of claim 4, wherein the tunable laser generation unit is a broadband tunable laser with a center wavelength of 850nm, 980nm, 1064nm, 1310nm, 1550nm or 2000nm, a maximum wavelength tuning range of 40-100 nm, a line width of less than 100MHz, a wavelength resolution of less than 1nm, and a 10nm wavelength switching speed of less than 1 μ sec;

the maximum modulation bandwidth range of the narrow-band linear frequency modulation is 10GHz-40 GHz.

6. The method of claim 4, wherein the predetermined duration is not less than a modulation period of the frequency modulated continuous wave signal.

7. The method according to any one of claims 1 to 6, wherein the obtaining distance and/or speed information of the target object according to the echo optical signal and the local oscillator optical signal comprises:

coupling the echo optical signal and the local oscillator optical signal to obtain a beat frequency signal;

and acquiring the distance and/or speed information of the target object from the beat frequency signal.

8. The method of claim 7, wherein the step of power amplifying the outgoing optical signal before transmitting the outgoing optical signal through an optical phased array further comprises:

carrying out frequency shift processing on the emergent light signal;

the obtaining of the distance and/or speed information of the target object from the beat signal includes:

and acquiring the distance and/or speed information of the target object from the beat frequency signal in combination with the frequency shift amount of the frequency shift processing.

9. A lidar system, comprising:

the tunable laser generating unit is used for generating output optical signals with tunable wavelengths;

the linear frequency modulation unit is used for carrying out linear frequency modulation on the output optical signal to obtain a frequency modulated continuous wave signal;

the first optical coupling unit is used for splitting the frequency modulated continuous wave signal to obtain an emergent light signal and a local oscillation light signal;

the optical amplification unit is used for carrying out power amplification on the emergent light signal;

the optical phased array transmitting unit is used for transmitting the emergent light signal to realize two-dimensional scanning of a target object;

a receiving unit for receiving an echo optical signal reflected by a target object;

and the processing unit is used for acquiring the distance and/or speed information of the target object according to the echo optical signal and the local oscillator optical signal.

10. The lidar system of claim 9,

the optical phased array transmitting unit comprises a waveguide grating structure;

the tunable laser generation unit can control the wavelength of the emergent light signal by controlling the wavelength of the output light signal, so that the optical phased array emission unit scans in a first dimension;

the optical phased array can divide the emergent light signals to be emitted from the waveguide grating structure, and the main large angle after the interference of the emergent light signals of each path is controlled by controlling the phase of the emergent light signals of each path, so that the optical phased array emission unit scans in the second dimension.

11. The lidar system of claim 10,

the tunable laser generation unit is used for sequentially generating output optical signals with different wavelengths, and continuously outputting the output optical signals with each wavelength for a preset time length so as to sequentially change the emergent angle of the emergent optical signals on the first dimension;

the optical phased array transmitting unit is used for scanning at least once in the second dimension within each preset time length.

12. The lidar system of claim 11,

the linear frequency modulation unit is used for carrying out narrow-band linear frequency modulation on the output optical signal, wherein the wavelength fluctuation range caused by the narrow-band linear frequency modulation is smaller than the wavelength difference between adjacent wavelengths when the tunable laser carries out wavelength switching.

13. The lidar system of claim 12, wherein the tunable laser generation unit is a broadband tunable laser having a center wavelength of 850nm, 980nm, 1064nm, 1310nm, 1550nm, or 2000nm, a maximum wavelength tuning range of 40-100 nm, a line width of less than 100MHz, a wavelength resolution of less than 1nm, and a 10nm wavelength switching speed of less than 1 microsecond;

the maximum modulation bandwidth range of the narrow-band linear frequency modulation is 10GHz-40 GHz.

14. The lidar system of claim 12, wherein the predetermined duration is not less than a modulation period of the frequency modulated continuous wave signal.

15. The lidar system according to any of claims 9 to 14, wherein the processing unit comprises:

the second optical coupling unit is used for coupling the echo optical signal and the local oscillator optical signal;

the photoelectric conversion unit is used for converting the coupled optical signals into electric signals to obtain beat frequency signals;

and the signal processing unit is used for acquiring the distance and/or speed information of the target object from the beat frequency signal.

16. The lidar system of claim 15, further comprising:

the optical frequency shift unit is used for performing frequency shift processing on the emergent light signal before the optical amplification unit performs power amplification on the emergent light signal;

and the signal processing unit is used for acquiring the distance and/or speed information of the target object from the beat frequency signal by combining the frequency shift amount of the frequency shift processing.

17. The lidar system of claim 15,

the receiving unit is used for receiving the echo optical signal reflected by the target object, and outputting the echo optical signal to the second optical coupling unit after coupling.

18. The lidar system of claim 15,

the center wavelengths of the chirp unit, the first optical coupling unit, the optical frequency shift unit, the optical amplification unit, the optical phased array emission unit, the second optical coupling unit and the photoelectric conversion unit are consistent with the center wavelength of the tunable laser generation unit.

Technical Field

The invention relates to the technical field of laser radars, in particular to a laser radar measuring method and a laser radar system.

Background

An Optical Phased Array (OPA) can realize scanning at any emission angle, does not have any mechanical rotating component, and is considered to be one of the most competitive core devices in the solid-state lidar.

At present, research heat for OPA devices is high, but the difficulty of supporting a two-dimensional scanning OPA device based on pure phase control is still high in design and process, and the wide application is difficult to develop at the present stage. On the other hand, the one-dimensional scanning OPA device can completely accept wavelength modulation and realize two-dimensional scanning according to the working principle. The Frequency Modulated Continuous Wave (FMCW) technique is very suitable for being applied to a laser radar system by virtue of an inherent ranging and speed measuring mechanism, and the detection sensitivity of the technique is theoretically at least three orders of magnitude higher than that of the conventional pulse detection. In view of the fact that the transmission power of the OPA device is lower than that of the traditional pulse laser radar signal, and the requirement on the working laser line width is high, the Frequency Modulated Continuous Wave (FMCW) technology is very suitable for being combined with the OPA.

In the prior art, an FMCW mechanism is realized on a one-dimensional OPA, the two-dimensional scanning of the one-dimensional OPA cannot be realized through wavelength modulation generally, and the two-dimensional scanning can be realized only through stacking of the one-dimensional OPA; furthermore, implementing the FMCW mechanism on a one-dimensional OPA places high demands on the dynamic range and accuracy of the laser.

Disclosure of Invention

The invention provides a laser radar measuring method and a laser radar system, which are used for realizing the combination of an optical phased array and a frequency modulation continuous wave system and avoiding the realization of two-dimensional scanning of a one-dimensional optical phased array device in a stacking mode.

The first aspect of the present invention provides a laser radar measurement method, including:

generating an output optical signal with tunable wavelength by a tunable laser generation unit;

carrying out linear frequency modulation on the output optical signal to obtain a frequency modulated continuous wave signal;

splitting the frequency modulated continuous wave signal to obtain an emergent light signal and a local oscillation light signal;

after the emergent light signals are amplified in power, the emergent light signals are transmitted through an optical phased array transmitting unit, and two-dimensional scanning of a target object is achieved;

and after receiving the echo optical signal reflected by the target object, acquiring the distance and/or speed information of the target object according to the echo optical signal and the local oscillator optical signal.

Further, the optical phased array transmitting unit includes a waveguide grating structure;

the emission through optical phased array emission unit realizes the two-dimensional scanning to the target object, includes:

controlling the wavelength of an output optical signal through the tunable laser generation unit to control the wavelength of the outgoing optical signal so that the optical phased array emission unit scans in a first dimension;

the emergent light signals are divided by the optical phased array and emitted from the waveguide grating structure, and the main large angle after the interference of the emergent light signals is controlled by controlling the phase of the emergent light signals, so that the optical phased array emission unit scans in the second dimension.

Further, the emitting by the optical phased array emitting unit realizes two-dimensional scanning of the target object, and includes:

sequentially generating output optical signals with different wavelengths through the tunable laser generating unit, and continuously outputting the output optical signals with each wavelength for a preset time length so as to sequentially change the emergent angle of the emergent optical signals on the first dimension;

at least one scan in a second dimension is performed by the optical phased array transmission unit for each of the preset durations.

Further, the performing linear frequency modulation on the output optical signal to obtain a frequency modulated continuous wave signal includes:

and performing narrow-band chirp on the output optical signal, wherein the wavelength fluctuation range caused by narrow-band chirp modulation is smaller than the wavelength difference between adjacent wavelengths when the tunable laser performs wavelength switching.

Further, the tunable laser generation unit is a broadband tunable laser, the center wavelength of the tunable laser generation unit is 850nm, 980nm, 1064nm, 1310nm, 1550nm or 2000nm, the maximum wavelength tuning range is 40-100 nm, the line width is less than 100MHz, the wavelength resolution is less than 1nm, and the 10nm wavelength switching speed is less than 1 microsecond;

the maximum modulation bandwidth range of the narrow-band linear frequency modulation is 10GHz-40 GHz.

Further, the preset duration is not less than the modulation period of the frequency modulated continuous wave signal.

Further, the obtaining of the distance and/or the speed information of the target object according to the echo optical signal and the local oscillator optical signal includes:

coupling the echo optical signal and the local oscillator optical signal to obtain a beat frequency signal;

and acquiring the distance and/or speed information of the target object from the beat frequency signal.

Further, before the emergent light signal is transmitted through the optical phased array after power amplification, the method further includes:

carrying out frequency shift processing on the emergent light signal;

the obtaining of the distance and/or speed information of the target object from the beat signal includes:

and acquiring the distance and/or speed information of the target object from the beat frequency signal in combination with the frequency shift amount of the frequency shift processing.

A second aspect of the present invention provides a lidar system comprising:

the tunable laser generating unit is used for generating output optical signals with tunable wavelengths;

the linear frequency modulation unit is used for carrying out linear frequency modulation on the output optical signal to obtain a frequency modulated continuous wave signal;

the first optical coupling unit is used for splitting the frequency modulated continuous wave signal to obtain an emergent light signal and a local oscillation light signal;

the optical amplification unit is used for carrying out power amplification on the emergent light signal;

the optical phased array transmitting unit is used for transmitting the emergent light signal to realize two-dimensional scanning of a target object;

a receiving unit for receiving an echo optical signal reflected by a target object;

and the processing unit is used for acquiring the distance and/or speed information of the target object according to the echo optical signal and the local oscillator optical signal.

Further, the optical phased array transmitting unit includes a waveguide grating structure;

the tunable laser generation unit can control the wavelength of the emergent light signal by controlling the wavelength of the output light signal, so that the optical phased array emission unit scans in a first dimension;

the optical phased array can divide the emergent light signals to be emitted from the waveguide grating structure, and the main large angle after the interference of the emergent light signals of each path is controlled by controlling the phase of the emergent light signals of each path, so that the optical phased array emission unit scans in the second dimension.

Further, the tunable laser generation unit is configured to sequentially generate output optical signals with different wavelengths, and continuously output the output optical signals with each wavelength for a preset time duration, so as to sequentially change the emergent angle of the emergent optical signals in the first dimension;

the optical phased array transmitting unit is used for scanning at least once in the second dimension within each preset time length.

Further, the chirp unit is configured to perform narrow-band chirp on the output optical signal, where a wavelength fluctuation range caused by the narrow-band chirp modulation is smaller than a wavelength difference between adjacent wavelengths when the tunable laser performs wavelength switching.

Further, the tunable laser generation unit is a broadband tunable laser, the center wavelength of the tunable laser generation unit is 850nm, 980nm, 1064nm, 1310nm, 1550nm or 2000nm, the maximum wavelength tuning range is 40-100 nm, the line width is less than 100MHz, the wavelength resolution is less than 1nm, and the 10nm wavelength switching speed is less than 1 microsecond;

the maximum modulation bandwidth range of the narrow-band linear frequency modulation is 10GHz-40 GHz.

Further, the preset duration is not less than the modulation period of the frequency modulated continuous wave signal.

Further, the processing unit includes:

the second optical coupling unit is used for coupling the echo optical signal and the local oscillator optical signal;

the photoelectric conversion unit is used for converting the coupled optical signals into electric signals to obtain beat frequency signals;

and the signal processing unit is used for acquiring the distance and/or speed information of the target object from the beat frequency signal.

Further, the lidar system further includes:

the optical frequency shift unit is used for performing frequency shift processing on the emergent light signal before the optical amplification unit performs power amplification on the emergent light signal;

and the signal processing unit is used for acquiring the distance and/or speed information of the target object from the beat frequency signal by combining the frequency shift amount of the frequency shift processing.

Optionally, the optical phased array transmitting unit is a transmitting unit of an optical phased array device based on a silica-based waveguide grating coupler;

the receiving unit is the waveguide grating coupler of the optical phased array device based on the silicon-based waveguide grating coupler, and is used for receiving the echo optical signal and outputting the echo optical signal to the processing unit through the waveguide circulator.

Optionally, the receiving unit is an optical fiber coupling unit, and is configured to receive the echo optical signal and output the echo optical signal to the processing unit through an optical fiber.

Further, the center wavelengths of the chirp unit, the first optical coupling unit, the optical frequency shift unit, the optical amplification unit, the optical phased array emission unit, the second optical coupling unit, and the photoelectric conversion unit are consistent with the center wavelength of the tunable laser generation unit.

According to the laser radar measuring method and the laser radar system, the tunable laser generating unit is used for generating the output optical signal with tunable wavelength; carrying out linear frequency modulation on the output optical signal to obtain a frequency modulated continuous wave signal; splitting the frequency modulated continuous wave signal to obtain an emergent light signal and a local oscillation light signal; after the emergent light signals are amplified in power, the emergent light signals are transmitted through an optical phased array transmitting unit, and two-dimensional scanning of a target object is achieved; and after receiving the echo optical signal reflected by the target object, acquiring the distance and/or speed information of the target object according to the echo optical signal and the local oscillator optical signal. By combining the tunable laser and the optical phased array system, two-dimensional scanning can be realized on the basis of a one-dimensional optical phased array device, and the one-dimensional optical phased array device is prevented from realizing two-dimensional scanning in a stacking mode; by adopting an external modulation mode, the output light signal of the broadband tunable light source is subjected to linear frequency modulation, so that the optical phased array, the broadband tunable laser and a frequency modulation continuous wave system can be reasonably combined, a complete laser radar system is constructed, and the defect that the broadband tunable laser is difficult to perform narrow-band linear frequency modulation is overcome.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

Fig. 1 is a flowchart of a lidar measurement method according to an embodiment of the present invention;

FIG. 2 is a block diagram of a lidar system provided by an embodiment of the present invention;

FIG. 3 is a schematic diagram of signal processing of a lidar system provided by an embodiment of the invention;

FIG. 4 is a schematic diagram of signal processing of a lidar system according to another embodiment of the present invention;

FIG. 5 is a schematic diagram of signal processing of a lidar system according to another embodiment of the present invention;

fig. 6 is a schematic diagram illustrating a control method for performing two-dimensional scanning in a laser radar system according to an embodiment of the present invention;

FIG. 7 is a schematic diagram of a scanning track of the two-dimensional scan in the embodiment of FIG. 6;

FIG. 8 is a block diagram of a lidar system provided in accordance with another embodiment of the present invention;

fig. 9 is a block diagram of a lidar system according to another embodiment of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Fig. 1 is a flowchart of a lidar measurement method according to an embodiment of the present invention. The lidar measurement method provided by the embodiment can be applied to a lidar system shown in fig. 2, and comprises the following specific steps:

s11, generating an output optical signal with tunable wavelength by a tunable laser generation unit;

s12, performing linear frequency modulation on the output optical signal to obtain a frequency modulated continuous wave signal;

s13, splitting the frequency modulated continuous wave signal to obtain an emergent light signal and a local oscillation light signal;

s14, after the emergent light signals are amplified in power, the emergent light signals are emitted through an optical phased array emitting unit, and two-dimensional scanning of a target object is achieved;

and S15, after receiving the echo optical signal reflected by the target object, acquiring the distance and/or speed information of the target object according to the echo optical signal and the local oscillator optical signal.

The above-mentioned lidar measurement method will be described in detail with reference to the lidar system shown in fig. 2.

The lidar system in the present embodiment includes a tunable laser generation unit 101, a chirp unit 102, a first optical coupling unit 103, an optical amplification unit 105, an optical phased array transmission unit 106, a reception unit, and a processing unit.

The tunable laser generating unit 101 is configured to generate an output optical signal with a tunable wavelength; the input end of the chirp unit 102 is optically connected to the output end of the tunable laser generation unit 101, and is configured to perform chirp on the output optical signal to obtain a frequency modulated continuous wave signal; the first optical coupling unit 103 comprises an input end and two output ends, wherein the input end of the first optical coupling unit is optically connected with the output end of the linear frequency modulation unit 102, and is used for splitting the frequency modulated continuous wave signal to obtain an emergent light signal 111 and a local oscillation light signal 112; the optical amplification unit 105 is optically connected to one output end of the first optical coupling unit 103 (an output end for outputting the outgoing optical signal 111), and is configured to perform power amplification on the outgoing optical signal 111; the optical phased array transmitting unit 106 is used for transmitting the emergent light signal 113 subjected to power amplification to realize two-dimensional scanning of a target object; a receiving unit for receiving the echo optical signal 114 reflected by the target object; the processing unit is optically connected to the output end of the receiving unit and the other output end of the first optical coupling unit 103 (outputting the own optical signal), respectively, and is configured to obtain the distance and/or speed information of the target object according to the echo optical signal 114 and the local oscillator optical signal 112.

The tunable laser generation unit 101 is a continuous laser with a tunable output wavelength having a broadband characteristic, and the specific types of the tunable laser include, but are not limited to, a solid laser, a fiber laser, a semiconductor laser, and the like, and the wavelength tuning mechanism of the tunable laser generation unit includes, but is not limited to, a mechanical type, an external cavity type, a distributed feedback, a fiber bragg grating, and the like; the center wavelength of the tunable optical fiber includes, but is not limited to 850nm, 980nm, 1064nm, 1310nm, 1550nm or 2000nm, the maximum wavelength tuning range is 40-100 nm, the line width is less than 100MHz, the wavelength resolution is less than 1nm, and the wavelength switching speed of 10nm is less than 1 microsecond.

The chirp unit 102 is used to perform narrowband chirp on the output optical signal of the tunable laser generation unit 101, and the chirp unit 102 may include, but is not limited to, an electro-optical modulator, an acousto-optical modulator, a silicon photonic modulator, etc., and its modulation type includes, but is not limited to, Double Sideband (DSB), Single Sideband (SSB), carrier-suppressed double sideband (CS-DSB), carrier-suppressed single sideband (CS-SSB), etc., and the maximum modulation bandwidth is 10GHz-40 GHz.

The first optical coupling unit 103 is configured to split a frequency-modulated continuous wave signal and output an outgoing optical signal 111 and a local oscillator optical signal 112, the actual physical device type corresponding to the unit may include, but is not limited to, a polarization beam splitter, a non-polarization beam splitter, an optical fiber coupler, and the like based on the light splitting principle, and the number of output optical beams is not less than 2.

The optical amplification unit 105 amplifies the power of the outgoing optical signal 111 to provide sufficient system emitted optical power to ensure the required detection distance. The actual physical device type corresponding to the unit includes but is not limited to a doped fiber amplifier, a semiconductor optical amplifier, an integrated silicon photonic optical amplifier and the like based on the optical amplification principle.

The optical phased array transmitting unit 106 transmits the power-amplified outgoing optical signal 113, and two-dimensional scanning of the target object is achieved. The optical phased array transmitting unit 106 is characterized in that:

1) working in a one-dimensional scanning mode, that is, the optical phased array transmitting unit 106 splits the outgoing light signals to obtain multiple paths of outgoing light signals, and transmits the multiple paths of outgoing light signals from the waveguide grating structure, different phase differences are added to each path of outgoing light signals, and the phase of each path of outgoing light signals is controlled to control the main maximum angle of each path of outgoing light signals after interference to generate certain deflection, so that one-dimensional scanning can be realized;

2) corresponding to the actual physical device including but not limited to the transmitting unit of the optical phased array in the form of integrated silicon-based optical waveguide, the transmitting unit 106 of the optical phased array includes a waveguide grating structure or other light transmitting structure similar to the waveguide grating; the wavelength of the output optical signal is controlled by the tunable laser generation unit 101, so that the deflection angle (diffraction angle) of the output optical signal can be changed, and the scanning of the optical phased array transmission unit 106 in the other dimension can be realized;

3) the number of waveguide phase control arrays is 16-128;

4) according to the type of the optical phased array and the difference of corresponding manufacturing processes, the 0-order diffraction principal of the waveguide grating needs to be ensured to be within the wavelength range of incident light, and the change of the diffraction angle is not less than 20 degrees.

The receiving unit is used for receiving the echo optical signal 114 reflected by the target object and outputting the echo optical signal to the processing unit; the receiving unit may be integrated into the optical phased array or the processing unit, or a receiving unit may be separately provided, and thus is not separately shown in fig. 2.

The processing unit obtains the local oscillation optical signal 112 of the first optical coupling unit 103 and the echo optical signal 114 reflected by the target object, and obtains the distance and/or speed information of the target object according to the echo optical signal 114 and the local oscillation optical signal 112. More specifically, the processing unit includes: a second optical coupling unit 108, a photoelectric conversion unit 109, and a signal processing unit 110.

A second optical coupling unit 108, configured to couple the echo optical signal 114 and the local oscillator optical signal 112. The second optical coupling unit 108 has the capability of combining at least 2 paths of light beams, and the unit corresponds to actual physical device types including but not limited to a polarization beam splitter, a non-polarization beam splitter, a fiber coupler and the like.

And the photoelectric conversion unit 109 is configured to convert the coupled optical signal into an electrical signal to obtain a beat signal. The photoelectric conversion unit 109 includes a photoelectric detection device, an amplifying circuit, a filtering circuit, and the like, wherein the photoelectric detection device includes but is not limited to a PIN photodiode, an APD photodiode, a balanced detector, and the like according to its operation principle, and is configured to generate a mixing frequency on a detector surface of the local oscillation optical signal 112 and the echo optical signal 114 mixed in the second optical coupling unit 108, and obtain a beat frequency signal.

And a signal processing unit 110, configured to obtain distance and/or velocity information of the target object from the beat signal. The signal processing unit 110 includes an integrated circuit main control chip with certain computing power and a peripheral circuit for ensuring the operation thereof, the type of the main control chip includes but is not limited to FPGA, DSP, MCU, etc., the peripheral circuit includes at least an analog-to-digital converter (ADC), and the unit is used for collecting and processing the beat frequency signal obtained by the photoelectric conversion unit 109, and extracting information such as distance, speed, etc. of the target object.

On the basis of the above embodiment, the lidar system may further include an optical frequency shift unit 104, configured to perform frequency shift processing on the outgoing optical signal 111 before the optical amplification unit 105 performs power amplification on the outgoing optical signal 111; the optical frequency shift unit 104 is specifically configured to perform unidirectional optical frequency shift on the outgoing optical signal 111 from the front-end first optical coupling unit 103, so as to generate an intermediate frequency in the beat signal of the FMCW system, where the unit corresponds to actual physical device types including, but not limited to, an acousto-optic modulator, an electro-optic modulator, a silicon photonic modulator, and the like. The central wavelength of the selected device is required to be consistent with the central wavelength of the tunable laser generation unit 101, the working bandwidth is appropriate, and the maximum frequency shift amount is 200 MHz.

Further, the signal processing unit 110 is configured to obtain distance and/or velocity information of the target object from the beat signal in combination with the frequency shift amount of the frequency shift processing.

It should be noted that, based on the above embodiments, the operating center frequency of the actual physical device selected by the chirp unit 102, the first optical coupling unit 103, the optical frequency shift unit 104, the optical amplification unit 105, the optical phased array transmission unit 106, and the second optical coupling unit 108 should be consistent with the center frequency of the device selected by the tunable laser generation unit 101, and the operating bandwidth is reasonable.

The principle of the scanning and ranging process of the laser radar system will be described in detail below.

FIG. 3 is a diagram illustrating an instantaneous frequency relationship between a local oscillator optical signal and an echo optical signal according to an embodiment of the present invention, in which the chirp unit 102 may be an electro-optical modulator, and the modulation type is set to be an electro-optical modulatorThe carrier single sideband modulation is suppressed while the lidar system is not provided with the optical frequency shift unit 104. At the photodetector surface in the photoelectric conversion unit 109, the echo light signal 201 instantaneous frequency f_rLocal oscillator optical signal 202 instantaneous frequency f_s(since there is no optical frequency shift unit 104, the instantaneous frequency of the outgoing optical signal is the same as the instantaneous frequency of the local oscillator optical signal 202, not shown in the figure), in this embodiment, the chirp unit 102 employs triangular wave modulation with 50% duty cycle, and the modulation period is T_mThe modulation bandwidth of the triangular wave band is B_m(ii) a Echo optical signal 201 (without superimposed Doppler shift f)_B) The delay time with the local oscillator optical signal 202 is Δ τ, and the frequency difference Δ f between the rising edges of the echo optical signal 201 and the local oscillator optical signal 202 can reflect the distance information of the target object, if there is relative motion between the target object and the laser radar, there is a doppler shift f caused by the relative motion between the echo optical signal 201 and the laser radar_BDoppler shift f_BCan reflect the speed information of the target object and superpose f_BHas an instantaneous frequency f of the echo optical signal 203_r-|f_BL. At | f_BIn the case of | < Δ f, the instantaneous frequency of the beat signal is shown as 204, and two frequency values Δ f, | f, associated with distance and speed information can be obtained according to the instantaneous frequencies of different periods of the beat signal 204_BL, |; at | f_BIn | ≧ Δ f, the instantaneous frequency of the beat signal is shown as 205, and two frequency values Δ f, | f, associated with distance and speed information can be obtained according to the instantaneous frequency of different periods of the beat signal 205_B|。

In practical applications, Δ f and | f cannot be determined in advance_BI, fig. 4 discloses another modulation method of the chirp unit 102, and the echo light signal is 301 (without superposition of the doppler shift f)_B) The local oscillator optical signal is 302, superimposed with the Doppler shift f_BThe echo optical signal of (1) is 203, which simultaneously maintains a fixed frequency after the triangular wave period for extracting the Doppler shift | f alone_BAccording to | f_BAnd the instantaneous frequency of different periods of the beat signal 304 may determine Δ f.

In another embodiment, the linear toneThe frequency unit 102 is modulated by suppressing carrier double-sideband modulation, and the laser radar system is provided with an optical frequency shift unit 104 with a forward frequency shift amount f_shiftFIG. 5 shows the instantaneous frequency relationship in this embodiment, and the center frequency of the output optical signal of the tunable laser generating unit 101 at a certain fixed wavelength is f₀Modulated carrier frequency of f_cModulation bandwidth of B_m(ii) a In this embodiment, the system has two optical frequency components, which are an upper-band outgoing optical signal 401, a lower-band outgoing optical signal 402, an upper-band local oscillator optical signal 403, and a lower-band local oscillator optical signal 404; after a delay generated by a certain target object distance, an upper sideband echo optical signal 405 and a lower sideband echo optical signal 406 are formed (without superposition of Doppler frequency shift f)_B) Corresponding range beat amount is Δ f, and Doppler shift f is superimposed_BThen an upper sideband echo optical signal 407 and a lower sideband echo optical signal 408 are obtained; the double-sideband modulation mode can simultaneously obtain two peak frequency points, respectively f, in a beat frequency signal spectrum_up＝f_shift+Δf+f_B、f_down＝f_shift–Δf+f_BWherein f is_upRepresenting the beat frequency, f, of the upper sideband echo optical signal 407 and the upper sideband local oscillator optical signal 403_downRepresenting the beat frequency of the lower sideband echo optical signal 408 and the lower sideband local oscillator optical signal 404. Compared with the single-sideband modulation in the embodiment, the decoupling of the distance and speed information can be realized only according to the frequency spectrum information of the beat frequency signal corresponding to different time periods in the full cycle of the modulation signal, and the double-sideband modulation mode in the embodiment can simultaneously obtain two peak frequency points f in the beat frequency signal_upAnd f_downIt is easy to calculate two frequency values Δ f, f_B。

On the basis of the above embodiment, the optical phased array transmitting unit 106 transmits to implement two-dimensional scanning of the target object, which can be implemented specifically by the following means:

controlling the wavelength of an output optical signal by the tunable laser generation unit 101 to control the wavelength of the outgoing optical signal, so that the optical phased array transmission unit 106 scans in a first dimension;

the emergent light signals are divided by the optical phased array and emitted from the waveguide grating structure, and the main large angle after the interference of the emergent light signals is controlled by controlling the phase of the emergent light signals, so that the optical phased array emission unit scans in the second dimension.

In this embodiment, based on the transmission waveguide grating characteristics of the optical phased array, the 1 st order principal maximum diffraction angle α of the optical phased array transmission unit 106 and the wavelength λ of the outgoing light signal satisfy:

d(sinα+1)＝λ

therefore, for a one-bit optical phased array device, its emission angle in the direction perpendicular to the array waveguide will be modulated by the center wavelength of the signal light. It should be noted that the relationship between the angle α and the wavelength λ of the outgoing light signal is generally non-linear, but those skilled in the art can easily find out and apply the relationship by calibrating the relationship by a certain calibration means.

As an optional embodiment, the tunable laser generation unit 101 may sequentially generate output optical signals with different wavelengths, and continuously output the output optical signals with each wavelength for a preset time period, so as to sequentially change the emitting angle of the emitted optical signal in the first dimension; at least one scan in the second dimension is performed by the optical phased array transmit unit 106 for each of the preset durations.

For example, fig. 6 shows a timing relationship between the output wavelength 501 of the tunable laser generation unit 101 and the frequency 502 of the modulation signal of the chirp unit 102, where the left side of a biaxial coordinate system represents the wavelength and the right side represents the frequency; in the present embodiment, the tunable laser generation unit 101 outputs the wavelength 501 by a step change, i.e. at a specific output wavelength λ₁Next, a preset time (at least one modulation period time length) is maintained, the optical phased array transmitting unit 106 performs at least one scan in the second dimension within the preset time, and then the tunable laser generating unit 101 switches to the next wavelength λ₂Output, and at least one of the first and second dimensions by the optical phased array transmitting unit 106And (3) secondary scanning, repeating the steps to realize two-dimensional scanning, wherein the scanning track can be as shown in fig. 7, the horizontal emission angle of the optical phased array emission unit 601 is controlled by the phased array, the vertical emission angle is controlled by the central wavelength of the emergent light signal, and the matrix type two-dimensional scanning track 602 is presented under the control of the step wavelength. Because the wavelength switching speed of a general broadband tunable laser is different according to the working principle of the laser and the switching wavelength difference, the switching speed is usually in the order of tens of nanoseconds to microseconds at the fastest speed, and the scanning mode described in the embodiment has higher time utilization rate.

When the tunable laser generation unit 101 outputs an output optical signal with a certain wavelength, the output optical signal is chirped by the chirp unit 102, and a wavelength change, that is, a chirp bandwidth B, is theoretically caused_mTheoretically, the wavelength of the emergent light signal can be influenced, and further, the diffraction angle is changed, so that the pointing direction of the scanning angle is unstable, therefore, in the embodiment of the invention, the chirp unit 102 is required to perform narrow-band chirp, and the fluctuation range of the wavelength caused by narrow-band chirp is smaller than the wavelength difference between adjacent wavelengths when the tunable laser performs wavelength switching, that is, the chirp bandwidth B_mAnd the wavelength difference is far smaller than the switching wavelength difference delta lambda, so that the fluctuation of the diffraction angle caused by narrow-band linear frequency modulation can be ignored.

In the above embodiment, the tunable laser generation unit 101 may perform step switching at equal intervals on the wavelength, and may also design suitable wavelength switching driving according to an actual scanning scene, so as to implement different scanning fields and scanning tracks.

On the basis of any of the above embodiments, the receiving unit of the lidar system may be constructed as follows:

in an alternative embodiment, as shown in fig. 8, the optical phased array transmitting unit of this embodiment is a transmitting unit of an optical phased array device based on a silica-based waveguide grating coupler, and has a reversible waveguide optical path, and the receiving unit adopts a waveguide grating coupler of an optical phased array device based on a silica-based waveguide grating coupler. The following describes the working process of the lidar system according to the optical signal transmission direction: the broadband tunable laser 701 outputs an output optical signal with a specific wavelength, and the output optical signal is subjected to linear frequency modulation through an electro-optical modulator 702 and further split into an output optical signal light 711 and a local oscillator optical signal 712 through a 1 × 2 optical fiber coupler; the emergent light signal light 711 generates fixed frequency shift through the acousto-optic frequency shifter 704 to be used as system intermediate frequency, then power amplification is carried out through the optical fiber amplifier 705, and the optical phased array 706 transmits the emergent light signal 707 after frequency shift and power amplification to a certain specific angle in space under the control of a certain two-dimensional angle; after being irradiated by the emergent light signal 707, the target 709 generates a diffuse reflection echo light signal 708, and a part of the backward echo light signal 708 enters the waveguide grating coupler of the optical phased array and is output as an optically coupled echo light signal 710 through the waveguide circulator; the echo optical signal 710 and the local oscillator optical signal 712 are mixed by the 2 × 2 optical fiber coupler 713, and then a beat signal is generated on the surface of the detector in the photoelectric conversion unit 714, and finally the signal processing unit 715 resolves the beat signal to obtain the distance and/or speed information of the target object 709. In the system, the unit examples are connected by optical fibers. The modulation method, the scanning method, and the signal processing method in this embodiment may adopt the methods in the above embodiments, and are not described herein again.

In another optional embodiment, as shown in fig. 9, this embodiment provides a laser radar system based on transceiving and splitting of an optical phased array device, where a receiving unit of the system uses an optical fiber coupling unit to receive an echo optical signal, and the optical fiber coupling unit may specifically use an optical lens group, including a single chip or multiple chips of spherical surfaces, aspheric lenses, and graded index lenses, and the like, for coupling the echo optical signal into an optical fiber, and those skilled in the art may reasonably design a specific form of the coupling unit according to indexes such as a coupling field angle and coupling efficiency. The following describes the working process of the lidar system according to the optical signal transmission direction: the broadband tunable laser 801 outputs an output optical signal with a specific wavelength, the output optical signal is subjected to linear frequency modulation through an electro-optical modulator 802, and the output optical signal is further split into an output optical signal light 812 and a local oscillator optical signal 812 through a 1 × 2 optical fiber coupler; the emergent light signal light 812 generates fixed frequency shift through the acousto-optic frequency shifter 804 and is used as system intermediate frequency, then power amplification is carried out through the optical fiber amplifier 805, and the optical phased array 806 transmits an emergent light signal 807 which is subjected to frequency shift and power amplification to a certain specific angle in space under the control of a certain two-dimensional angle; a target 809 generates a diffuse reflection echo optical signal 808 after being irradiated by the emergent optical signal 807, and a part of the echo optical signal 808 is received by an independent optical fiber coupling unit 810 and coupled into an optical fiber 811 to be transmitted as an optical coupling echo optical signal 817; the echo optical signal 817 and the local oscillator optical signal 812 are mixed by the 2 × 2 optical fiber coupler 813, then beat frequency is generated on the surface of the detector in the photoelectric conversion unit 815, beat frequency signals are output, and finally the signal processing unit 816 calculates the distance and/or speed information of the target object 809 from the beat frequency signals. The modulation method, the scanning method, and the signal processing method in this embodiment may adopt the methods in the above embodiments, and are not described herein again.

In the laser radar measuring method and the laser radar system provided by the embodiments, the tunable laser generating unit generates the output optical signal with tunable wavelength; carrying out linear frequency modulation on the output optical signal to obtain a frequency modulated continuous wave signal; splitting the frequency modulated continuous wave signal to obtain an emergent light signal and a local oscillation light signal; after the emergent light signals are amplified in power, the emergent light signals are transmitted through an optical phased array transmitting unit, and two-dimensional scanning of a target object is achieved; and after receiving the echo optical signal reflected by the target object, acquiring the distance and/or speed information of the target object according to the echo optical signal and the local oscillator optical signal. By combining the tunable laser and the optical phased array system, two-dimensional scanning can be realized on the basis of a one-dimensional optical phased array device, and the one-dimensional optical phased array device is prevented from realizing two-dimensional scanning in a stacking mode; by adopting an external modulation mode, the output light signal of the broadband tunable light source is subjected to linear frequency modulation, so that the optical phased array, the broadband tunable laser and a frequency modulation continuous wave system can be reasonably combined, a complete laser radar system is constructed, and the defect that the broadband tunable laser is difficult to perform narrow-band linear frequency modulation is overcome.

In the embodiments provided in the present invention, it should be understood that the disclosed apparatus and method may be implemented in other ways. For example, the above-described apparatus embodiments are merely illustrative, and for example, the division of the units is only one logical division, and other divisions may be realized in practice, for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or units, and may be in an electrical, mechanical or other form.

The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.

In addition, functional units in the embodiments of the present invention may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, or in a form of hardware plus a software functional unit.

The integrated unit implemented in the form of a software functional unit may be stored in a computer readable storage medium. The software functional unit is stored in a storage medium and includes several instructions to enable a computer device (which may be a personal computer, a server, or a network device) or a processor (processor) to execute some steps of the methods according to the embodiments of the present invention. And the aforementioned storage medium includes: various media capable of storing program codes, such as a usb disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk, or an optical disk.

It is obvious to those skilled in the art that, for convenience and simplicity of description, the foregoing division of the functional modules is merely used as an example, and in practical applications, the above function distribution may be performed by different functional modules according to needs, that is, the internal structure of the device is divided into different functional modules to perform all or part of the above described functions. For the specific working process of the device described above, reference may be made to the corresponding process in the foregoing method embodiment, which is not described herein again.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.