Coaxial transceiving laser radar and optical chip

Abstract

This application provides a coaxial transceiver lidar and an optical chip. The lidar includes: a laser source, a first optical coupler, a second optical coupler, a coaxial optical transceiver unit, a coherent cancellation unit, a detection unit, and a signal processing unit. The laser source splits the generated laser signal into signal light and local oscillator light via the first optical coupler; the local oscillator light enters the coherent cancellation unit. The signal light is emitted from the coaxial optical transceiver unit via the second optical coupler and is received by the coaxial optical transceiver unit as reflected light. The reflected light and interference light generated by the coaxial optical transceiver unit enter the coherent cancellation unit via the second optical coupler. After the coherent cancellation unit uses the local oscillator light to eliminate the interference light, it sends the local oscillator light and the reflected light to the signal processing unit via the detection unit to calculate relevant obstacle information. The technical solution provided by this application can eliminate the influence of interference light on reflected light in the lidar optical path system, improve the ranging accuracy of the lidar, and ensure the normal operation of the lidar.

Description

Technical Field

[0001] This application relates to the field of lidar technology, and more specifically to a coaxial transceiver lidar and an optical chip. Background Technology

[0002] Frequency Modulated Continuous Wave (FMCW) lidar can emit laser signals with linear frequencies (referred to as emitted light or signal light) and, after receiving the laser signals reflected back from obstacles (referred to as received light or reflected light), determine the distance and other relevant information of the obstacles based on the frequency difference between the signal light and the reflected light at the moment of reception, thus having high ranging accuracy.

[0003] FMCW lidar includes parallel-axis FMCW lidar and coaxial FMCW lidar. In coaxial FMCW lidar, the emitted signal light and the received reflected light follow identical optical paths in the optical transceiver unit. Because FMCW has extremely high detection sensitivity, if the emitted light generates interference light in the optical path system, this interference light will severely interfere with the reflected light, causing inaccurate lidar ranging or even malfunctioning. Summary of the Invention

[0004] This application provides a coaxial transceiver lidar and an optical chip, which can eliminate interference light generated in the optical path system to a certain extent, improve the accuracy of lidar ranging, and ensure the normal operation of the lidar.

[0005] To address the aforementioned technical problems, this application provides the following technical solutions:

[0006] In a first aspect, embodiments of this application provide a coaxial transceiver lidar, which includes: a laser source, a first optical coupler, a second optical coupler, a coaxial optical transceiver unit, a coherent cancellation unit, a detection unit, and a signal processing unit.

[0007] A laser light source is used to generate laser signals.

[0008] The first optical coupler is used to split the laser signal into signal light and local oscillator light, and send the signal light to the second optical coupler and the local oscillator light to the coherent cancellation unit.

[0009] The second optical coupler is used to send signal light to the coaxial optical transceiver unit, receive reflected light and interference light returned by the coaxial optical transceiver unit, and send the reflected light and interference light to the coherent cancellation unit.

[0010] The coaxial optical transceiver unit is used to send signal light to obstacles and receive reflected light returned by obstacles; the coaxial optical transceiver unit generates interference light during the process of sending signal light to obstacles.

[0011] The coherent cancellation unit is used to coherently cancel the interference light with the local oscillator light to eliminate the interference light, and then sends the mixed light of the coherent local oscillator light and the reflected light to the detection unit; wherein the difference in optical path between the local oscillator light and the interference light from the laser source to the coherent cancellation unit is within a preset range.

[0012] The detection unit is used to convert the mixed light into an electrical signal.

[0013] The signal processing unit is used to determine relevant information about obstacles based on electrical signals.

[0014] The lidar provided in this application embodiment can eliminate the influence of interference light on reflected light in the radar optical path system by phase shifting the local oscillator light and using the phase-shifted local oscillator light to coherently process with the interference light, thereby improving the ranging accuracy of the lidar and ensuring the normal operation of the lidar.

[0015] In some embodiments, the coherent cancellation unit includes a phase shifter and a third optical coupler. The phase shifter is used to shift the phase of the local oscillator light, and the phase of the shifted local oscillator light differs from the phase of the interfering light by N. 180 degrees; where N is an integer. The third optical coupler is used to mix the phase-shifted local oscillator light, reflected light, and interference light to eliminate interference light, and then send the mixed light to the detection unit.

[0016] In this embodiment, when the phase of the local oscillator light after shifting differs from the phase of the interfering light by an odd multiple of 180 degrees, the interfering light and the local oscillator light are mixed, and the interfering light is eliminated through coherent cancellation. When the phase of the local oscillator light after shifting differs from the phase of the interfering light by an even multiple of 180 degrees, the interfering light and the local oscillator light are mixed, and the interfering light is eliminated through coherent enhancement synthesis, transforming the interfering light into the local oscillator light, thus increasing the amplitude of the local oscillator light. It can be understood that after the reflected light, the phase-shifted local oscillator light, and the interfering light are mixed together in the third optical coupler, only the reflected light and the local oscillator light remain.

[0017] In some embodiments, when the detection unit is a balanced detection unit, the third optical coupler splits the mixing light into two inputs to the balanced detection unit; or, when the detection unit is a single-ended detection unit, the third optical coupler inputs the mixing light as a single input to the single-ended detection unit. Compared to a single-ended detection unit, the balanced detection unit has a higher signal-to-noise ratio.

[0018] In some embodiments, the laser source is a narrow linewidth laser source, and the linewidth of the laser signal emitted by the narrow linewidth laser source is less than 10MHz.

[0019] In some embodiments, the second optical coupler includes a first port, a second port, and a third port. Signal light enters from the first port and exits from the second port; reflected light and interference light enter from the second port and exit from the third port.

[0020] In some embodiments, the relevant information about the obstacle includes at least one of distance information, speed information, orientation information, height information, attitude information, and shape information.

[0021] In some embodiments, the coaxial optical transceiver unit includes: at least one optical antenna, or at least one optical phased array system.

[0022] In some embodiments, the coaxial optical transceiver unit further includes an optical lens group for transmitting and enhancing signal light and reflected light.

[0023] In some embodiments, the first optical coupler, the second optical coupler, the coaxial optical transceiver unit, the coherent cancellation unit, and the detection unit are integrated on a silicon photonic chip to form an optical chip.

[0024] Secondly, embodiments of this application provide an optical chip, which includes a first optical coupler, a second optical coupler, a coaxial optical transceiver unit, a coherent cancellation unit, and a detection unit.

[0025] The first optical coupler is used to split the laser signal emitted by the laser source into signal light and local oscillator light, and send the signal light to the second optical coupler and the local oscillator light to the coherent cancellation unit.

[0026] The second optical coupler is used to send signal light generated by the laser source to the coaxial optical transceiver unit, receive reflected light and interference light returned by the coaxial optical transceiver unit, and send reflected light and interference light to the coherent cancellation unit.

[0027] The coaxial optical transceiver unit is used to send signal light to the obstacle and receive the reflected light returned by the obstacle; the coaxial optical transceiver unit generates this interference light in the process of sending signal light to the obstacle.

[0028] The coherent cancellation unit is used to coherently cancel the interference light with the local oscillator light generated by the laser source to eliminate the interference light, and sends the mixed light of the coherent local oscillator light and the reflected light to the detection unit; wherein, the difference in optical path between the local oscillator light and the interference light from the laser source to the coherent cancellation unit is within a preset range.

[0029] The detection unit is used to convert the mixed light into an electrical signal, which is then used to determine relevant information about the obstacle.

[0030] In some embodiments, the coherent cancellation unit includes a phase shifter and a third optical coupler. The phase shifter is used to shift the phase of the local oscillator light, and the phase of the shifted local oscillator light differs from the phase of the interfering light by N. 180 degrees, N is an integer. The third optical coupler is used to mix the phase-shifted local oscillator light, reflected light, and interference light to eliminate interference light, and then send the mixed light to the detection unit.

[0031] It is understandable that the beneficial effects of the second aspect mentioned above can be found in the relevant descriptions in the first aspect mentioned above, and will not be repeated here. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 This is a schematic diagram of the structure of the coaxial transceiver lidar provided in the embodiments of this application.

[0034] Figure 2 This is a schematic diagram of the first optical coupler processing optical signals provided in the embodiments of this application.

[0035] Figure 3 This is a schematic diagram of the second optical coupler processing optical signals provided in the embodiments of this application.

[0036] Figure 4A This is a schematic diagram of the processing of optical signals by a third optical coupler provided in one embodiment of this application.

[0037] Figure 4B This is a schematic diagram of the processing of optical signals by a third optical coupler provided in another embodiment of this application. Detailed Implementation

[0038] The technical solutions provided in the embodiments of this application will be described below with reference to the accompanying drawings.

[0039] It should be understood that in the description of the embodiments of this application, unless otherwise stated, " / " means "or". For example, A / B can mean A or B. The "and / or" in this document is merely a description of the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist simultaneously, and B exists alone.

[0040] In this embodiment, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this embodiment, unless otherwise stated, "a plurality of" means two or more.

[0041] LiDAR (Light Detection and Ranging) can scan and detect target areas using laser signals, determining parameters such as distance, orientation, height, speed, attitude, and even shape of objects within the scanned area. This allows for monitoring of the target scanned area, and it has wide applications in military, security, and surveying fields. In recent years, with the surge in intelligent devices such as autonomous driving, drones, and robots, the demand for LiDAR has become increasingly urgent, and the performance requirements have become increasingly stringent.

[0042] LiDAR includes Time-of-Flight (TOF) lidar for ranging and Frequency-Modulated Continuous Wave (FMCW) lidar for ranging. TOF ranging measures the distance to an obstacle based on the time of flight of the laser. FMCW ranging, on the other hand, modulates the laser frequency linearly using frequency modulation techniques such as triangular wave frequency modulation or sawtooth wave frequency modulation, and determines the obstacle distance based on the frequency difference between the emitted and received light at the same moment. In some embodiments, taking the reflected light incident at time T as an example, since the laser frequency changes linearly under FMCW ranging, the frequencies of the signal light and the reflected light at time T are different. By measuring the beat frequency generated by the coherence of the signal and received light, the distance to be measured can be calculated.

[0043] Compared to Time-of-Flight (TOF) ranging technology, Fiber-Mechanical Control Wave (FMCW) ranging technology has a wider range of applications, such as non-contact surface analysis, fiber optic sensing, positioning, and tomography. People have shown great interest in FMCW ranging technology because of its advantages, including a large dynamic range, strong anti-interference capability, extremely high detection sensitivity, and extremely high accuracy.

[0044] FMCW lidar includes parallel-axis and coaxial types. In parallel-axis FMCW lidar, the optical transceiver unit completely isolates the emitted signal light from the received reflected light, making the reflected light less susceptible to interference. However, the optical paths of parallel-axis FMCW lidar require precise alignment, which is very difficult to adjust and makes it relatively impractical. In coaxial FMCW lidar, the emitted signal light and the received reflected light follow identical optical paths in the optical transceiver unit. Due to the extremely high detection sensitivity of FMCW, if interference light is generated in the optical path system, this interference light will severely interfere with the reflected light, leading to inaccurate lidar ranging or even malfunction.

[0045] Therefore, this application provides a coaxial transceiver lidar that can eliminate interference light generated within the optical path system, improve the accuracy of coaxial FMCW laser ranging, and ensure the normal operation of the lidar.

[0046] Figure 1 This is a schematic diagram of the structure of a coaxial transceiver lidar provided in another embodiment of this application. See also... Figure 1 As shown, the FMCW lidar includes a laser source, a first optical coupler, a second optical coupler, a coaxial optical transceiver unit, a coherent cancellation unit, a detection unit, and a signal processing unit. The structure and function of each component are described in detail below.

[0047] The laser source is a frequency-modulated narrow-linewidth laser source, used to emit laser signals with a linewidth smaller than a preset linewidth (e.g., 10MHz). This laser signal is frequency-modulated, and the frequency modulation is linear.

[0048] The first optical coupler is used to split the laser signal into signal light and local oscillator light according to a preset ratio (e.g., 9:1, 99:1, etc.). Since both the signal light and the local oscillator light are obtained by splitting the same laser signal, the frequency variation patterns of the signal light and the local oscillator light are the same, and the frequency modulation is linear.

[0049] In some embodiments, see Figure 2 As shown, the first optical coupler is 1. The optical coupler 2, also known as the first optical coupler, includes one input terminal and two output terminals (such as output terminal 1 and output terminal 2). The input terminal is connected to the output terminal of the laser source to receive the laser signal. One of the output terminals is connected to the second optical coupler to transmit the signal light to the second optical coupler; the other output terminal is connected to the coherent cancellation unit to transmit the local oscillator light to the coherent cancellation unit.

[0050] The second optical coupler is used to send signal light to the coaxial optical transceiver unit, receive reflected light and interference light returned by the coaxial optical transceiver unit, and send the reflected light and interference light to the coherent cancellation unit for processing. For example, see [link to example]. Figure 3As shown, the second optical coupler can be an optical circulator, including a first port, a second port, and a third port. The first port is connected to the port from which the laser source emits signal light, the second port is connected to the optical input / output of the coaxial optical transceiver unit, and the third port is connected to the coherent cancellation unit. The second optical coupler receives the signal light through the first port and transmits the signal light from the second port to the optical input / output of the coaxial optical transceiver unit. Additionally, the second optical coupler receives reflected light and interference light through the second port and transmits them to the coherent cancellation unit through the third port.

[0051] The coaxial optical transceiver unit is used to transmit signal light towards an obstacle and receive the reflected light returned after encountering the obstacle. It should be noted that in the coaxial optical transceiver unit, the outgoing optical path of the signal light and the incoming optical path of the reflected light are the same. Furthermore, during the process of the signal light emanating from the coaxial optical transceiver unit, it is also reflected by the internal structure of the unit, generating interference light. This interference light, along with the reflected light, is transmitted to the coherent cancellation unit through the second optical coupler. Specifically, the reflected light and interference light enter from the second port of the second optical coupler, exit from the third port, and enter the coherent cancellation unit.

[0052] In some embodiments, the coaxial optical transceiver unit includes: at least one optical antenna, or at least one optical phased array system or other device or system that can be used for light transmission and reception. The optical antenna may be an optical transceiver in the form of an optical fiber, an optical transceiver in the form of an optical chip, or an optical transceiver in the form of a free-space lens group, etc., and this embodiment does not limit its specific form.

[0053] In other embodiments, the coaxial optical transceiver unit may also include an optical mirror group, which comprises one or more optical lenses. This optical mirror group can improve the efficiency of the coaxial optical transceiver unit in transmitting and receiving optical signals. However, it should be noted that, according to the principle of optical reversibility, while transmitting signal light, the optical mirror group will also reflect a portion of the signal light. Some of the stronger reflected light signals will form interference light and be reflected back to the second optical coupler along the original optical path. In other words, when the coaxial optical transceiver unit includes an optical mirror group, the interference signal generated by the coaxial optical transceiver unit includes not only the interference light generated in the receiving and transmitting optical paths but also the interference light generated by the reflection from the optical mirror group.

[0054] The coherent cancellation unit is used to coherently cancel the interference light with the local oscillator light to eliminate the interference light, and then mixes the coherent local oscillator light and the reflected light into a mixed light before sending it to the detection unit.

[0055] In some embodiments, the coherent cancellation unit includes a phase shifter and a third optical coupler. The phase shifter is used to shift the phase of the local oscillator light, and the shifted phase of the local oscillator light differs from the phase of the interfering light by N. 180 degrees, where N is an integer. The third optical coupler is used to mix the phase-shifted local oscillator light, reflected light, and interference light to eliminate interference light, and then sends the mixed light to the detection unit.

[0056] It should be noted that the optical path difference between the local oscillator light and the interfering light must be kept within a preset range, such as equal optical paths or an optical path difference of less than 10 cm. In this embodiment, the optical path refers to the distance traveled by the optical signal (e.g., local oscillator light, interfering light) from the laser source to the output and then to the third optical coupler of the coherent cancellation unit.

[0057] Taking local oscillator light as an example, combined with Figure 1 The structure shown includes the following optical path lengths for the local oscillator: the length of the optical fiber between the laser source and the first optical coupler, the path traveled by the local oscillator within the first optical coupler, the length of the optical fiber between the first optical coupler and the phase shifter, the path traveled by the local oscillator within the phase shifter, and the length of the optical fiber between the phase shifter and the third optical coupler.

[0058] Taking interference light as an example, since interference light is generated by the reflection of signal light, the optical path of interference light includes not only the optical path of the signal light from the laser source to the coaxial optical transceiver unit, but also the path traveled by the interference light after the signal light is reflected by the coaxial optical transceiver unit to form interference light. In other words, combining... Figure 1 The structure shown includes the following optical path lengths for the interference light: the length of the optical fiber between the laser source and the first optical coupler, the path length of the local oscillator light within the first optical coupler, the length of the optical fiber between the first and second optical couplers, the path length of the signal light within the second optical coupler, twice the length of the optical fiber between the second optical coupler and the coaxial optical transceiver unit, the path length of the reflected light within the second optical coupler, and the length of the optical fiber between the second and third optical couplers.

[0059] Since both the signal light and the local oscillator light are modulated optical signals, their frequencies change linearly. Because the speed of light is constant, when the optical path lengths of the interfering light generated by the local oscillator light and the signal light are within a preset range, it can be assumed that the local oscillator light and the interfering light reach the third optical coupler in the same or similar time. In other words, the local oscillator light and the interfering light are laser signals emitted by the laser source at the same or similar time, with the same or similar frequencies, and can coherently cancel each other out.

[0060] When the phase difference between the shifted local oscillator light and the interfering light is an odd multiple of 180 degrees, the interfering light and the local oscillator light coherently cancel each other out after mixing, the interfering light essentially disappears, and the amplitude of the local oscillator light decreases. When the phase difference between the shifted local oscillator light and the interfering light is an even multiple of 180 degrees, the interfering light and the local oscillator light coherently enhance and combine after mixing, the interfering light becomes the local oscillator light, and the amplitude of the local oscillator light increases. It can be understood that after the reflected light, the phase-shifted local oscillator light, and the interfering light are mixed together in the third optical coupler, only the reflected light and the local oscillator light remain.

[0061] In some embodiments, see Figure 4A As shown, the third optical coupler is 2. 1 and 1 The optical coupler configuration 2 consists of a third optical coupler with two input terminals and one output terminal. These two input terminals are connected to the third port of the phase shifter and the second optical coupler, respectively. One input terminal is used to input the phase-shifted local oscillator light, and the other input terminal is used to input the reflected light and interference light. The output terminal is connected to the detection unit. After mixing the phase-shifted local oscillator light, reflected light, and interference light, the third optical coupler outputs the mixture to the detection unit through this output terminal.

[0062] In other embodiments, the third optical coupler is 2. The optical coupler 2, or the third optical coupler, has two input terminals and two output terminals. The first input terminal is connected to the output terminal of the phase shifter to receive the phase-shifted local oscillator light, and the second input terminal is connected to the third port of the second optical coupler to receive reflected and interfering light. The second output terminal is connected to different input terminals of the detection unit. This third optical coupler mixes the phase-shifted local oscillator light, reflected light, and interfering light, and then outputs them through the two output terminals to the different input terminals of the detection unit.

[0063] The detection unit is used to convert the mixed light into an electrical signal. The mixed light includes local oscillator light and reflected light, and the local oscillator light and reflected light have different frequencies.

[0064] In some embodiments, the detection unit is a single-ended detection unit, meaning the detection unit has only one input end for the mixing light. This single-ended detection unit is equipped with 2... The third optical coupler of 1 is used to receive the single-channel mixed light output from the third optical coupler.

[0065] In some embodiments, the detection unit is a balanced detection unit, meaning the detection unit has two input terminals for the mixing light. This balanced detection unit is equipped with 2... The third optical coupler of 2 is used to receive the dual-channel mixed light output from the third optical coupler.

[0066] The signal processing unit can be a microcontroller, digital signal processor (DSP), or field-programmable gate array (FPGA) or other circuit module with logic operation capabilities. The signal processing unit is used to determine relevant obstacle information based on the electrical signals sent by the detection unit. This obstacle information includes at least one of the following: distance information, speed information, orientation information, height information, attitude information, and shape information.

[0067] The following is combined Figure 1 The structure shown illustrates the working process of the coaxial lidar provided in the embodiments of this application.

[0068] After the lidar is powered on, the laser source emits a laser signal to the first optical coupler, which splits the signal into a signal beam and a local oscillator beam. The local oscillator beam is phase-shifted by a phase shifter and then enters the third optical coupler in the coherent cancellation unit. The signal beam passes through the second optical coupler and exits through the coaxial optical transceiver unit, generating interference light during the exit process. Upon encountering an obstacle, the signal beam returns to the coaxial optical transceiver unit as reflected light. The returned reflected light and interference light pass through the second optical coupler and enter the third optical coupler in the coherent cancellation unit. The third optical coupler mixes the phase-shifted local oscillator beam, the reflected light, and the interference light to form a mixed light. During the mixing process, the phase-shifted local oscillator beam eliminates the interference light, leaving only the local oscillator beam and the reflected light in the mixed light. The detection unit converts this mixed light into an electrical signal and sends it to the signal processing unit for calculation to determine relevant obstacle information, such as the obstacle's distance and speed.

[0069] In summary, the lidar provided in this application embodiment can eliminate the influence of interference light on reflected light in the lidar optical path system by phase shifting the local oscillator light and using the phase-shifted local oscillator light to coherently process with the interference light, thereby improving the ranging accuracy of the lidar and ensuring the normal operation of the lidar.

[0070] This application also provides an optical chip, which includes a first optical coupler, a second optical coupler, a coaxial optical transceiver unit, a coherent cancellation unit, and a detection unit. These components can be integrated onto a silicon photonics chip. For the specific structure and function of the first optical coupler, the second optical coupler, the coaxial optical transceiver unit, the coherent cancellation unit, and the detection unit, please refer to the preceding description; these details will not be repeated here.

[0071] It should be noted that the optical chip provided in this embodiment can be applied not only to FMCW lidar, but also to other devices that use FMCW ranging technology. This embodiment does not limit its application scenarios.

[0072] As described above, when the optical chip provided in this application embodiment is used for FMCW laser ranging, the optical chip can improve ranging accuracy by performing phase shifting on the local oscillator light and coherent processing with the phase-shifted local oscillator light and interference light.

[0073] It should be understood that, when used in this application specification and the appended claims, the term "comprising" indicates the presence of the described features, integrals, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or a collection thereof.

[0074] References to "one embodiment" or "some embodiments" in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, phrases such as "in one embodiment," "in some embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0075] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A coaxial transceiver lidar, characterized in that, include: The system includes a laser source, a first optical coupler, a second optical coupler, a coaxial optical transceiver unit, a coherent cancellation unit, a detection unit, and a signal processing unit. The laser source is used to generate laser signals; The first optical coupler is used to split the laser signal into signal light and local oscillator light, and send the signal light to the second optical coupler and send the local oscillator light to the coherent cancellation unit; The second optical coupler is used to send the signal light to the coaxial optical transceiver unit, receive the reflected light and interference light returned by the coaxial optical transceiver unit, and send the reflected light and interference light to the coherent cancellation unit. The coaxial optical transceiver unit is used to send the signal light to the obstacle and receive the reflected light returned by the obstacle; the coaxial optical transceiver unit generates the interference light during the process of sending the signal light to the obstacle. The coherent cancellation unit is used to perform coherent cancellation processing on the interference light using the local oscillator light to eliminate the interference light, and then send the mixed light of the coherent local oscillator light and the reflected light to the detection unit; wherein the difference in optical path length between the local oscillator light and the interference light from the laser source to the coherent cancellation unit is within a preset range; The detection unit is used to convert the mixed light into an electrical signal; The signal processing unit is used to determine relevant information about the obstacle based on the electrical signal.

2. The lidar according to claim 1, characterized in that, The coherent cancellation unit includes a phase shifter and a third optical coupler. The phase shifter is used to shift the phase of the local oscillator light, and the phase of the shifted local oscillator light differs from the phase of the interfering light by N. 180 degrees; where N is an integer; The third optical coupler is used to mix the phase-shifted local oscillator light, the reflected light, and the interference light to eliminate the interference light, and then send the mixed light to the detection unit.

3. The lidar according to claim 2, characterized in that, When the detection unit is a balanced detection unit, the third optical coupler splits the mixing light into two paths and inputs them to the balanced detection unit; or... When the detection unit is a single-ended detection unit, the third optical coupler will input the mixed light as one path to the detection unit.

4. The lidar according to any one of claims 1 to 3, characterized in that, The laser source is a narrow linewidth laser source, and the linewidth of the laser signal emitted by the narrow linewidth laser source is less than 10MHz.

5. The lidar according to any one of claims 1 to 3, characterized in that, The second optical coupler includes a first port, a second port, and a third port. The signal light enters from the first port and exits from the second port; The reflected light and the interfering light enter from the second port and exit from the third port.

6. The lidar according to any one of claims 1 to 3, characterized in that, The relevant information about the obstacle includes at least one of the following: distance information, speed information, orientation information, height information, attitude information, and shape information.

7. The lidar according to any one of claims 1 to 3, characterized in that, The coaxial optical transceiver unit includes: at least one optical antenna, or at least one optical phased array system.

8. The lidar according to claim 7, characterized in that, The coaxial optical transceiver unit also includes an optical lens group for transmitting and enhancing the signal light and the reflected light.

9. The lidar according to claim 1, characterized in that, The first optical coupler, the second optical coupler, the coaxial optical transceiver unit, the coherent cancellation unit, and the detection unit are integrated on a silicon photonic chip to form an optical chip.

10. An optical chip, characterized in that, The optical chip includes a first optical coupler, a second optical coupler, a coaxial optical transceiver unit, a coherent cancellation unit, and a detection unit. The first optical coupler is used to split the laser signal emitted by the laser source into signal light and local oscillator light, and send the signal light to the second optical coupler and the local oscillator light to the coherent cancellation unit; The second optical coupler is used to send the signal light to the coaxial optical transceiver unit, receive the reflected light and interference light returned by the coaxial optical transceiver unit, and send the reflected light and interference light to the coherent cancellation unit. The coaxial optical transceiver unit is used to send the signal light to the obstacle and receive the reflected light returned by the obstacle; the coaxial optical transceiver unit generates the interference light during the process of sending the signal light to the obstacle. The coherent cancellation unit is used to perform coherent cancellation processing on the interference light using the local oscillator light to eliminate the interference light, and to send the mixed light of the coherent local oscillator light and the reflected light to the detection unit; wherein the difference in optical path length between the local oscillator light and the interference light from the laser source to the coherent cancellation unit is within a preset range; The detection unit is used to convert the mixed light into an electrical signal, and the electrical signal is used to determine relevant information about the obstacle.

11. The optical chip according to claim 10, characterized in that, The coherent cancellation unit includes a phase shifter and a third optical coupler. The phase shifter is used to shift the phase of the local oscillator light, and the phase of the shifted local oscillator light differs from the phase of the interfering light by N. 180 degrees; where N is an integer; The third optical coupler is used to mix the phase-shifted local oscillator light, the reflected light, and the interference light to eliminate the interference light, and then send the mixed light to the detection unit.

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