Lidar transceiver optical system and lidar applying the same and method of operating the same

Abstract

This invention belongs to the field of lidar technology and discloses a lidar transceiver optical system, a lidar using the same, and a method for operating the same. The lidar transceiver optical system includes at least one transceiver module for transmitting laser signals to or receiving reflected laser signals from an optical fiber coupling module; an optical fiber coupling module for transmitting received transmitted laser signals to a conjugate system module or transmitting reflected laser signals received from the conjugate system module to the transceiver module for processing; a scanning module; a conjugate system module for focusing transmitted laser signals from the optical fiber coupling module onto the scanning module or coupling reflected laser signals received from the scanning module into the optical fiber coupling module, wherein the distance between the focal point of the focusing system and the scanning module is adjustable; and a beam expanding module for expanding and collimating the transmitted light signal from the scanning module and then directing it towards the area to be measured or for converging the reflected light signal from the area to be measured onto the scanning module.

Description

Technical Field

[0001] This invention relates to FMCW (Frequency Modulated Continuous Wave) lidar technology, specifically to a lidar transceiver optical system, a lidar using the same, and a method for operating the same. Background Technology

[0002] In high-tech fields such as intelligent robots, drones, autonomous driving, and smart cities, the accuracy of environmental perception and the rapid response to corresponding environmental changes are particularly important.

[0003] In long-range sensor lidar, lidar with micro-electro-mechanical system (MEMS) galvanometers as its core completes scanning by reflecting laser light through the rotation of integrated micro-mirrors. The technology is currently mature and can be mass-produced, thus achieving lightweight and fast scanning, and has great development prospects.

[0004] However, due to the problems caused by the rapid oscillation of the MEMS galvanometer itself, a balance needs to be struck between rotation angle, frame rate, ranging capability, and reliability. Therefore, how to expand the scanning field of view and reduce the optical signal loss of the system without sacrificing performance such as frame rate and ranging capability is a key research focus in this field. Summary of the Invention

[0005] In order to expand the scanning field of view and reduce the optical signal loss of the system without sacrificing performance such as frame rate and ranging capability, this invention proposes a lidar transceiver optical system, a lidar using the same, and a method for operating the same.

[0006] The laser radar transceiver optical system according to the present invention includes: at least one transceiver module, an optical fiber coupling module, a conjugate system module, a scanning module, and a beam expander module. The transceiver module is used to transmit laser signals to the optical fiber coupling module or receive reflected laser signals from the optical fiber coupling module. The optical fiber coupling module is used to transmit the received transmitted laser signals to the conjugate system module or to transmit reflected laser signals received from the conjugate system module to the transceiver module for processing. The conjugate system module is used to focus the transmitted laser signals from the optical fiber coupling module onto the scanning module or to couple the reflected laser signals received by the scanning module into the optical fiber coupling module. The distance between the focal point of the focusing system of the conjugate system module and the scanning module is adjustable to adjust the offset of the light spot formed on the conjugate system module. The beam expander module is used to expand and collimate the transmitted light signals after passing through the scanning module and direct them towards the area to be measured, or to converge the reflected light signals from the area to be measured onto the scanning module.

[0007] Furthermore, the conjugate system module includes a collimation system and a focusing system.

[0008] Furthermore, the ratio of the focal length of the collimation system to the focal length of the focusing system is adjustable.

[0009] Furthermore, the ratio of the focal length of the collimation system to the focal length of the focusing system ranges from 2 to 80.

[0010] Furthermore, the distance between the focal point of the focusing system of the conjugate system module and the scanning module is greater than or equal to the focal length of the beam expander module.

[0011] Furthermore, the scanning module includes a first galvanometer, through which the emitted laser signal from the conjugate system module is scanned and enters the beam expander module.

[0012] Furthermore, the scanning module includes a second galvanometer and a rotating mirror. The emitted laser signal from the conjugate system module is deflected by the second galvanometer and then scanned by the rotating mirror into the beam expansion module, or the emitted laser signal from the conjugate system module is scanned by the rotating mirror and then deflected by the second galvanometer into the beam expansion module.

[0013] Furthermore, the transceiver module includes a transmitting module, a beam splitter module, and a receiving module. The transmitting module is used to transmit laser signals; the beam splitter module is used to pass the transmitted laser signals through and direct them toward the fiber optic coupling module, and also to deflect the received reflected laser signals to the receiving module; the receiving module is used to receive and process the reflected laser signals deflected by the beam splitter module.

[0014] Furthermore, the optical splitting module is formed by connecting at least one beam splitter and at least one circulator in sequence. The emitted laser signal emitted by the transmitting module enters the optical fiber coupling module after passing through the beam splitter and circulator. The reflected laser signal from the optical fiber coupling module is deflected by the circulator and then received and processed by the receiving module.

[0015] Furthermore, the fiber coupling module includes single-mode fiber.

[0016] The lidar according to the present invention includes the above-described lidar transceiver optical system.

[0017] The method for operating a lidar system according to the present invention includes the following steps: during the transmission of a laser signal, adjusting the distance between the focal point of the focusing system of the conjugate system module of the lidar transceiver optical system and the scanning module to adjust the scanning field of view angle of the beam expander module; during the reception of a laser signal, reducing the distance between the focal point of the focusing system of the conjugate system module of the lidar transceiver optical system and the scanning module to reduce the offset of the light spot formed on the conjugate system module, thereby reducing the offset of the light spot on the fiber coupling module.

[0018] The laser radar transceiver optical system of this invention, by setting up a conjugate system module, can determine the angle that the beam expander module can expand by controlling and adjusting the distance between the focal point of the focusing system of the conjugate system module and the scanning module during the laser signal transmission process. This setting overcomes the problem of small mechanical scanning angle and small coverage of a single sensor in the prior art of scanning modules (such as MEMS galvanometers), and thus can meet the requirements of a large field of view. For example, increasing the distance between the focal point of the focusing system of the conjugate system module and the scanning module allows for a larger scanning distance swept by the focal point at the same rotation angle of the scanning module, resulting in a larger scanning field of view after passing through the beam expander module. During laser signal reception, the excessively fast vibration frequency and long detection distance of existing scanning modules lead to asynchronous transmission and reception, causing a positional shift in the optical signal energy during reception. This makes it difficult to couple effectively into the fiber optic coupling module, resulting in optical signal loss. This invention reduces the distance between the focal point of the focusing system of the conjugate system module and the scanning module, thereby reducing the offset of the light spot formed on the conjugate system module. This further reduces the offset of the light spot on the fiber optic coupling module, effectively improving the problem of decreased fiber optic receiving coupling efficiency due to the walk-off effect, and thus effectively reducing energy loss caused by walk-off. Simultaneously, the beam expander module can effectively expand the scanning field of view of the entire system while maintaining higher fiber optic receiving coupling efficiency. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of a lidar transceiver optical system according to an embodiment of the present invention;

[0020] Figure 2 This is a schematic diagram of the structure of a lidar transceiver optical system according to a first embodiment of the present invention;

[0021] Figure 3 This is a schematic diagram of the structure of a lidar transceiver optical system according to a second embodiment of the present invention;

[0022] Figure 4 This is a flowchart of a method for operating a lidar system according to an embodiment of the present invention. Detailed Implementation

[0023] To better understand the purpose, structure, and function of this invention, the invention will be described in further detail below with reference to the accompanying drawings.

[0024] Figure 1 A schematic diagram of a lidar transceiver optical system 100 according to an embodiment of the present invention is shown. Figure 1As shown, the lidar transceiver optical system 100 includes: at least one transceiver module 1, an optical fiber coupling module 2, a conjugate system module 3, a scanning module 4, and a beam expander module 5. The transceiver module 1 transmits a laser signal to the optical fiber coupling module 2 or receives a reflected laser signal from the optical fiber coupling module 2. The optical fiber coupling module 2 transmits the received transmitted laser signal to the conjugate system module 3 or transmits the reflected laser signal received from the conjugate system module 3 to the transceiver module 1 for processing. The conjugate system module 3 focuses the transmitted laser signal from the optical fiber coupling module 2 onto the scanning module 4 or couples the reflected laser signal received by the scanning module 4 into the optical fiber coupling module 2. The distance between the focal point of the focusing system of the conjugate system module 3 and the scanning module 4 is adjustable to adjust the offset of the light spot formed on the conjugate system module 3. The beam expander module 5 expands and collimates the transmitted light signal after passing through the scanning module 4 and directs it towards the area to be measured, or converges the reflected light signal from the area to be measured onto the scanning module 4.

[0025] The lidar transceiver optical system 100 of this invention, by setting up a conjugate system module 3, can determine the angle that the beam expander module 5 can expand by controlling and adjusting the distance between the focal point of the focusing system of the conjugate system module 3 and the scanning module 4 during the laser signal emission process. This setting overcomes the problem that the mechanical scanning angle of the scanning module (such as MEMS galvanometer) is small and the coverage of a single sensor is small in the prior art, thus meeting the requirements of a large field of view. For example, by increasing the distance between the focal point of the focusing system of the conjugate system module 3 and the scanning module 4, the distance swept by the focal point under the same rotation angle of the scanning module 4 is greater, resulting in a larger scanning field of view after passing through the beam expander module 5. During laser signal reception, the existing scanning module 4 has an excessively fast vibration frequency and a long detection distance, leading to asynchronous transmission and reception. This causes a positional shift in the optical signal energy during reception, making it difficult to couple well into the fiber coupling module 2, resulting in optical signal loss. This invention reduces the distance between the focal point of the focusing system of the conjugate system module 3 and the scanning module 4, thereby reducing the offset of the light spot formed on the conjugate system module 3, further reducing the offset of the light spot on the fiber coupling module 2. This effectively improves the problem of decreased fiber coupling efficiency due to the walk-off effect, and thus effectively reduces the energy loss caused by walk-off. Simultaneously, the beam expander module 5 can effectively expand the scanning field of view of the entire system while achieving higher fiber receiving coupling efficiency.

[0026] It should be noted that the distance between the focal point of the focusing system of the conjugate system module 3 and the scanning module 4 should not be too small. This would make it difficult for the beam expander module 5 to expand the scanning field of view during the laser signal emission process. Therefore, the value of the distance between the focal point of the conjugate system module 3 and the scanning module 4 needs to balance the emission requirements. This value can vary depending on the product requirements and needs to be set specifically for the specific product. No specific limitation is made here.

[0027] In some embodiments, the conjugate system module 3 may include a collimation system and a focusing system. The collimation system is used to collimate the emitted laser signal from the fiber coupling module 2, and the focusing system is used to focus the collimated light from the collimation system onto the scanning module 4. Due to the reversibility of the optical path, the laser signal reflected back from the scanning module 4 can also pass through the focusing system back to the collimation system, and then back to the fiber coupling module 2. The collimation system may be a conventional lens, a conventional lens group, or a self-focusing lens, etc. The focusing system may be a focusing lens, which may be a single lens or a lens group composed of multiple lenses.

[0028] Preferably, the ratio of the focal length of the collimation system to the focal length of the focusing system is adjustable. The principle behind this setting is to reduce the offset of the position of the light spot behind the scanning module on the focusing system caused by the walk-off effect, thereby reducing the offset of the focal point of the fiber coupling module 2, thus improving the fiber receiving coupling efficiency of the fiber coupling module 2.

[0029] Furthermore, in order to ensure better fiber coupling efficiency of the fiber coupling module 2, the ratio of the focal length of the collimation system to the focal length of the focusing system can be set to a range of 2 to 80.

[0030] According to the present invention, the distance between the focal point of the conjugate system module 3 and the scanning module 4 is greater than or equal to the focal length of the beam expander module 5, so as to achieve the purpose of expanding the scanning field of view by the beam expander module 5.

[0031] According to the present invention, the scanning module 4 may have various structures.

[0032] In such Figure 2 In the preferred embodiment shown, the scanning module 4 may include a first galvanometer. The emitted laser signal emitted via the conjugate system module 3 is scanned by the first galvanometer into the beam expander module 5. The first galvanometer completes the scanning of the emitted laser signal and the reception of the reflected laser signal within the overall field of view by rotating in the horizontal and vertical directions. The first galvanometer may be a MEMS galvanometer, a mechanical galvanometer, or other functional units with the same or similar functions.

[0033] In such Figure 3In the preferred embodiment shown, the scanning module 4 may include a second galvanometer 41 and a rotating mirror 42. The emitted laser signal from the conjugate system module 3 is deflected by the second galvanometer 41 and then scanned by the rotating mirror 42 into the beam expander module 5, or the emitted laser signal from the conjugate system module 3 is scanned by the rotating mirror 42 and then deflected by the second galvanometer 41 into the beam expander module 5. The second galvanometer 41 is mainly used to deflect the laser signal; it may be a MEMS galvanometer, a mechanical galvanometer, or other functional units with the same or similar functions.

[0034] According to the present invention, in such Figure 2 He Ru Figure 3 In the illustrated embodiment, the transceiver module 1 may include a transmitting module 11, a beam splitter module 12, and a receiving module 13. The transmitting module 11 transmits a laser signal; the beam splitter module 12 passes the transmitted laser signal through to the fiber optic coupling module 2 and deflects the received reflected laser signal to the receiving module 13; the receiving module 13 receives and processes the reflected laser signal deflected by the beam splitter module 12. The transmitting module 11 can be various types of lasers, such as carbon dioxide lasers, neodymium-doped yttrium aluminum garnet lasers, semiconductor lasers, wavelength-tunable solid-state lasers, and fiber optic frequency-modulated lasers; the receiving module 13 can employ various types of photodetectors, such as photomultiplier tubes, semiconductor photodiodes, avalanche photodiodes, and combinations of infrared and visible light multi-element detectors.

[0035] Furthermore, in such Figure 2 He Ru Figure 3 In the embodiment shown, the light separation module 12 can be formed by sequentially connecting at least one beam splitter 121 and at least one circulator 122. When the emitted laser signal emitted by the transmitting module 11 passes through the beam splitter 121, part of it is used as the local oscillator signal, and the rest is used as the emitted laser signal and directed to the circulator 122. The emitted laser signal after passing through the circulator 122 is emitted outward for detection of the area to be measured. The reflected laser signal reflected back by the object in the area to be measured is deflected by the circulator 122 and received by the receiving module 13. The reflected laser signal and the local oscillator signal have certain differences in frequency, phase, amplitude, etc. By cohering the reflected laser signal and the local oscillator signal, information such as the distance, speed and orientation between the measured object and the lidar can be obtained.

[0036] Preferably, the beam splitter 121 and the circulator 122 can be 1*2 beam splitters.

[0037] Furthermore, the fiber coupling module 2 may include a single-mode fiber to be suitable for transmitting laser signals over long distances.

[0038] Furthermore, this invention also proposes a lidar including the aforementioned lidar transceiver optical system 100, particularly an FMCW lidar. Since the aforementioned lidar transceiver optical system 100 can effectively improve the problem of reduced fiber receiving coupling efficiency of the fiber coupling module caused by the walk-off effect, it improves the ranging capability of lidars (especially FMCW lidars) using it.

[0039] Furthermore, this invention also proposes a method for operating a lidar system, such as... Figure 4 As shown, the process includes the following steps: Step 1 S1: During the laser signal transmission process, the distance between the focal point of the focusing system of the conjugate system module 3 in the laser radar transceiver optical system 100 and the scanning module 4 is adjusted to adjust the scanning field of view angle of the beam expander module 5, thereby expanding the scanning field of view. Step 2 S2: During the laser signal reception process, the distance between the focal point of the focusing system of the conjugate system module 3 in the laser radar transceiver optical system 100 and the scanning module 4 is reduced to reduce the offset of the light spot formed on the conjugate system module 3, thereby reducing the offset of the light spot on the fiber optic coupling module 2, thereby improving the coupling efficiency of the fiber optic coupling module 2 and reducing the optical signal loss of the laser radar system.

[0040] It should be noted that, unless otherwise stated, the technical or scientific terms used in this application should have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0041] In the description of this application, it should be understood that the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated.

[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention 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 or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. The present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A lidar transceiver optical system, characterized in that, include: The system includes at least one transceiver module, an optical fiber coupling module, a conjugate system module, a scanning module, and a beam expander module, wherein the transceiver module is used to transmit a laser signal to the optical fiber coupling module or receive a reflected laser signal from the optical fiber coupling module; the optical fiber coupling module is used to transmit the received transmitted laser signal to the conjugate system module or to transmit a reflected laser signal received from the conjugate system module to the transceiver module for processing; The conjugate system module is used to focus the emitted laser signal from the fiber coupling module onto the scanning module, or to couple the reflected laser signal received by the scanning module into the fiber coupling module. The distance between the focal point of the focusing system of the conjugate system module and the scanning module is adjustable to adjust the offset of the light spot formed on the conjugate system module. The beam expander module is used to expand and collimate the emitted light signal after passing through the scanning module and then direct it toward the area to be measured, or to converge the reflected light signal from the area to be measured onto the scanning module.

2. The lidar transceiver optical system according to claim 1, characterized in that, The conjugate system module includes a collimation system and a focusing system.

3. The lidar transceiver optical system according to claim 2, characterized in that, The ratio of the focal length of the collimation system to the focal length of the focusing system is adjustable.

4. The lidar transceiver optical system according to claim 3, characterized in that, The ratio of the focal length of the collimation system to the focal length of the focusing system ranges from 2 to 80.

5. The lidar transceiver optical system according to any one of claims 1 to 4, characterized in that, The distance between the focal point of the focusing system of the conjugate system module and the scanning module is greater than or equal to the focal length of the beam expander module.

6. The lidar transceiver optical system according to any one of claims 1 to 4, characterized in that, The scanning module includes a first galvanometer, and the emitted laser signal emitted by the conjugate system module is scanned by the first galvanometer and enters the beam expander module.

7. The lidar transceiver optical system according to any one of claims 1 to 4, characterized in that, The scanning module includes a second galvanometer and a rotating mirror. The emitted laser signal emitted by the conjugate system module is deflected by the second galvanometer and then scanned by the rotating mirror into the beam expansion module, or the emitted laser signal emitted by the conjugate system module is scanned by the rotating mirror and then deflected by the second galvanometer into the beam expansion module.

8. The lidar transceiver optical system according to any one of claims 1 to 4, characterized in that, The transceiver module includes a transmitting module, a beam splitter module, and a receiving module. The transmitting module is used to transmit the transmitted laser signal. The beam splitter module is used to pass the transmitted laser signal through and direct it toward the fiber optic coupling module, and is also used to deflect the received reflected laser signal to the receiving module. The receiving module is used to receive and process the reflected laser signal deflected by the beam splitter module.

9. The lidar transceiver optical system according to claim 8, characterized in that, The optical splitting module is formed by connecting at least one beam splitter and at least one circulator in sequence. The emitted laser signal emitted by the transmitting module enters the optical fiber coupling module after passing through the beam splitter and the circulator. The reflected laser signal from the optical fiber coupling module is deflected by the circulator and then received and processed by the receiving module.

10. The lidar transceiver optical system according to any one of claims 1 to 4, characterized in that, The fiber coupling module includes a single-mode fiber.

11. A lidar, characterized in that, Includes the lidar transceiver optical system according to any one of claims 1-10.

12. A method for operating a lidar transceiver optical system, characterized in that, The method is based on the lidar transceiver optical system as described in any one of claims 1-10, and the method includes the following steps: During the transmission of laser signals, the distance between the focal point of the focusing system of the conjugate system module of the lidar transceiver optical system and the scanning module is adjusted to adjust the scanning field of view angle of the beam expander module. During the laser signal reception process, the distance between the focal point of the focusing system of the conjugate system module and the scanning module in the laser radar transceiver optical system is reduced to reduce the offset of the light spot formed on the conjugate system module, thereby reducing the offset of the light spot on the fiber coupling module.

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