Laser radar transmitting and receiving system based on multi-surface common-body optical element

Abstract

The invention discloses a laser radar transmit-receive system based on a multi-surface common-body optical element, the system comprises the multi-surface common-body optical element, the multi-surface common-body optical element comprises a base body and a transmitting mirror and a reflecting mirror which are arranged on the base body, the transmitting mirror comprises a first optical surface and a second optical surface which are coaxially arranged, the first optical surface is provided with a first entrance pupil, and the second optical surface is provided with a second entrance pupil; a first exit pupil is arranged between the second optical surface and the base body, the reflector comprises a third optical surface and a fourth optical surface which are coaxially arranged, a second entrance pupil is arranged between the fourth optical surface and the base body, and a second exit pupil is arranged on the third optical surface. The transmitting mirror and the reflecting mirror are parallel and share one body, the structure is simple and compact, the mass and the size of the laser radar transmitting and receiving system can be effectively reduced, and integration, integration and miniaturization are achieved; off-axis caused by influence of external factors such as stress and thermal deformation is avoided, and a high-stability working environment can be met; the reflector and the reflector are naturally coaxial, optical axis adjustment is not needed, and installation and adjustment are simple and convenient.

Description

Technical Field

[0001] This invention relates to the field of lidar technology, and in particular to a lidar transceiver system based on a multi-faceted coaxial optical element. Background Technology

[0002] LiDAR, as a commonly used ranging sensor, has advantages such as long detection range, high resolution, strong resistance to active interference, small size and light weight. Its principle is based on the time-of-flight method. Specifically, the laser emitted by the laser emission system encounters the target and returns to be received by the detection and receiving system. By measuring the round-trip time of the laser, the distance between the target and the radar can be measured. By combining it with scanning structures such as galvanometers, the entire target area can be scanned and detected, thereby obtaining a three-dimensional image of the target detection area. It is currently widely used in fields such as autonomous driving, drones and intelligent robots.

[0003] With the development of target detection and ranging technologies, lidar systems have been extensively studied. The transceiver system is a crucial component of lidar, specifically comprising two parts: transmission and reception. Optically, lidar systems are classified into two types: transmissive and reflective. Transmissive structures are further divided into two main types: paraxial and coaxial. Paraxial optical structures typically use a separate lens for the transmitting optics, while the receiving optics serves as the main structural component, with the transmitting lens fixed to it. Paraxial structures are relatively large and require careful monitoring of stress and thermal deformation at the lens and main structure to prevent optical axis drift (i.e., non-parallelism), which alters the lidar's measurement range. Coaxial structures share a set of optical elements at the front end of the transmitting and receiving systems, while the rear end uses a beam-splitting structure. This results in higher system stability, but the drawback is a protrusion in the vertical direction, particularly noticeable in long-focal-length, large-aperture applications.

[0004] like Figure 1 As shown, in a typical lidar transceiver system based on paraxial optics, the detection laser is emitted by a laser emitting unit, passes through a collimating lens a, and is then emitted outwards. After detecting a target, the laser signal returns to the receiving system. The returned laser signal is focused by a receiving lens b and then received by a detection signal receiving unit. The digital processing unit processes the returned laser signal, converting the optical signal into an electrical signal to ultimately achieve target detection.

[0005] However, the transmitting and receiving mirrors of typical lidar transceiver systems based on paraxial optics are discrete, usually consisting of two or more lenses. This discrete structure results in a large system size and weight, and makes it difficult to ensure the relative positions of the lenses, hindering miniaturization, lightweight design, and high stability requirements, especially for large-aperture systems. Furthermore, the lenses are susceptible to optical axis deflection due to their own stress, thermal deformation, and various external factors, leading to increased measurement errors. Additionally, during installation and debugging, the laser transmitting and receiving mirrors need to be collimated separately, making the alignment of the light paths cumbersome and the overall structure complex. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a lidar transceiver system based on multi-faceted common optical elements that is simple and compact in structure, highly stable, and easy to assemble and adjust.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A lidar transceiver system based on a multi-faceted optical element includes a multi-faceted optical element. The multi-faceted optical element includes a substrate and a transmitting mirror and a reflecting mirror disposed on the substrate. The transmitting mirror includes a first optical surface and a second optical surface arranged coaxially. A first entrance pupil is provided on the first optical surface, and a first exit pupil is provided between the second optical surface and the substrate. The reflecting mirror includes a third optical surface and a fourth optical surface arranged coaxially. A second entrance pupil is provided between the fourth optical surface and the substrate, and a second exit pupil is provided on the third optical surface.

[0008] As a further improvement to the above technical solution: the first optical surface and the third optical surface are disposed on the same surface of the substrate, and the distance between the second optical surface and the first optical surface is smaller than the distance between the fourth optical surface and the third optical surface.

[0009] As a further improvement to the above technical solution: a plurality of first connecting portions are provided between the second optical surface and the substrate in the circumferential direction, and a first exit pupil is formed between two adjacent first connecting portions; a plurality of second connecting portions are provided between the fourth optical surface and the substrate in the circumferential direction, and a second entrance pupil is formed between two adjacent second connecting portions.

[0010] As a further improvement to the above technical solution: the first optical surface, the second optical surface, the third optical surface and the fourth optical surface are all high-order aspherical reflective surfaces.

[0011] As a further improvement to the above technical solution: the first optical surface, the second optical surface, the third optical surface and the fourth optical surface are all provided with a high reflectivity film layer, and the reflectivity of the high reflectivity film layer is greater than 98%.

[0012] As a further improvement to the above technical solution: both the side surfaces of the second optical surface and the fourth optical surface are provided with a matte varnish layer.

[0013] As a further improvement to the above technical solution: both the first entrance pupil and the second exit pupil are circular through-hole structures, the first entrance pupil is located at the center of the first optical surface, and the second exit pupil is located at the center of the third optical surface.

[0014] As a further improvement to the above technical solution: the material of the multifaceted optical element is aerospace aluminum alloy.

[0015] As a further improvement to the above technical solution: the material of the multifaceted optical element is microcrystalline aluminum.

[0016] As a further improvement to the above technical solution: the lidar transceiver system based on multi-faceted common optical elements further includes a laser emitting unit, a detection signal receiving unit, and a digital processing unit. The laser emitting unit is configured corresponding to the first entrance pupil, the detection signal receiving unit is configured corresponding to the second exit pupil, and the digital processing unit is connected to the detection signal receiving unit.

[0017] Compared with the prior art, the advantages of the present invention are: The lidar transceiver system disclosed in this invention is based on a multi-faceted coaxial optical element. The transmitting mirror and the reflecting mirror are integrated in parallel, resulting in a simple and compact structure that effectively reduces the mass and volume of the lidar transceiver system. It has the advantages of integration, miniaturization, and miniaturization. Since multiple optical surfaces are processed onto the same optical substrate material, off-axis deviation caused by external factors such as stress and thermal deformation is avoided, thus meeting the requirements of a highly stable working environment. The transmitting mirror and the reflecting mirror are naturally coaxial, eliminating the need for optical axis adjustment and making assembly and adjustment simple and convenient.

[0018] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of an existing lidar transceiver system based on paraxial optics.

[0020] Figure 2 This is a schematic diagram of the principle of the lidar transceiver system based on multi-faceted common optical elements of the present invention. Figure 3 This is a three-dimensional structural schematic diagram of the multifaceted optical element in this invention.

[0021] Figure 4 This is a schematic diagram of the front view structure of the multifaceted optical element in this invention.

[0022] Figure 5 This is a cross-sectional structural diagram of the multifaceted optical element in this invention.

[0023] Figure 6 This is a schematic diagram of the receiving part in a specific embodiment of the present invention.

[0024] Figure 7 This is a schematic diagram of the structure of the transmitting part in a specific embodiment of the present invention.

[0025] Figure 8 This is a modulation function curve diagram of a specific embodiment of the present invention.

[0026] Figure 9 This is a wavefront difference diagram of a specific embodiment of the present invention.

[0027] The labels in the diagram represent: 1. Multifaceted optical element; 11. Substrate; 111. First connecting part; 112. Second connecting part; 12. First optical surface; 13. Second optical surface; 14. First entrance pupil; 15. First exit pupil; 16. Third optical surface; 17. Fourth optical surface; 18. Second entrance pupil; 19. Second exit pupil; 2. Laser emitting unit; 3. Detection signal receiving unit; 4. Digital processing unit. Detailed Implementation

[0028] In the description of this invention, it should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0029] Furthermore, 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 technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0030] In this invention, unless otherwise explicitly specified and limited, the terms "assembly," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0031] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] Figures 2 to 5 This invention illustrates an embodiment of a lidar transceiver system based on a multifaceted optical element. The system includes a multifaceted optical element 1, a laser emitting unit 2, a detection signal receiving unit 3, and a digital processing unit 4. The digital processing unit 4 is connected to the detection signal receiving unit 3. The multifaceted optical element 1 includes a substrate 11 and a emitting mirror and a reflecting mirror disposed on the substrate 11. The emitting mirror includes a first optical surface 12 and a second optical surface 13 coaxially arranged. The first optical surface 12 has a first entrance pupil 14, and the second optical surface 13 has a first exit pupil 15 between it and the substrate 11. The reflecting mirror includes a third optical surface 16 and a fourth optical surface 17 coaxially arranged. The fourth optical surface 17 has a second entrance pupil 18 between it and the substrate 11, and the third optical surface 16 has a second exit pupil 19. The laser emitting unit 2 is correspondingly disposed with the first entrance pupil 14, and the detection signal receiving unit 3 is correspondingly disposed with the second exit pupil 19.

[0033] The laser emitting unit 2 includes a laser and a beam coupling component. The laser emits laser light, which is coupled through the coupling component and then emitted. The laser includes, but is not limited to, solid-state, gas, liquid, semiconductor, and fiber lasers, and the emission wavelengths include, but are not limited to, 532 nm, 1064 nm, and 1550 nm.

[0034] The emitting mirror portion of the multifaceted optical element 1 is used to collimate the laser signal coupled by the beam coupling component to form an emitted laser signal and detect targets outward. The receiving mirror portion of the multifaceted optical element 1 is used to receive the returned laser signal reflected from the detected target and focus it. Unlike conventional optical elements, the multifaceted optical element 1 of this embodiment has multiple optical surfaces processed onto the same optical substrate material. Through ultra-precision machining, the surface shape accuracy of each optical surface and the positional accuracy between the surfaces are ensured, effectively guaranteeing the integration, miniaturization, and modularity of the system. This reduces the installation difficulty of each optical element, saves a significant amount of assembly and adjustment time, improves assembly and adjustment efficiency, avoids the offset of the coaxial relationship between optical surfaces, and, due to the consistent reflectivity and thermal properties, minimizes the off-axis caused by external factors such as stress and thermal deformation, thus improving the stability of the system.

[0035] See details Figure 4 The laser emitted by the laser emitting unit 2 illuminates the second optical surface 13 through the first entrance pupil 14, and is reflected by the second optical surface 14 back to the first optical surface 12. Finally, it exits from the first exit pupil 15 between the second optical surface 2 and the substrate 11, illuminating the target and generating an echo signal. The echo signal from the target enters the laser receiving part through the second entrance pupil 18, and is reflected sequentially by the third optical surface 16 and the fourth optical surface 17, exiting from the second exit pupil 19 and entering the detection signal receiving unit 3. It should be noted that the optical surfaces of the laser emitting part mainly serve the functions of laser collimation and beam expansion, belonging to an afocal optical system, while the optical surfaces of the laser receiving part focus the light and have a focal length. Furthermore, the multifaceted optical element 1 in this embodiment is a total internal reflection system, and there is no chromatic aberration.

[0036] The detection signal receiving unit 3 is used to process the returned laser signal that has been focused by the multifaceted optical element 1. Common photodetectors include, but are not limited to, combinations of photomultiplier tubes (PMTs), avalanche diodes (APDs), superconducting nanowire single-photon detectors (SNSPDs), and visible and infrared multi-element detectors.

[0037] The digital processing unit 4 is used to convert the returned laser signal, processed by the detection signal receiving unit 3, into a digital signal and ultimately achieve imaging. Commonly used digital processing units 4 include, but are not limited to, those employing a time-to-digital converter (TDC).

[0038] During operation, a laser emits a laser beam, generating a laser signal source. This signal is then coupled through a beam coupling assembly. The coupled laser signal is collimated by the emitting mirror of the multifaceted optical element 1, and the collimated signal is emitted to detect the target. Upon hitting the target, the emitted laser signal returns as a laser signal, which is received by the receiving mirror of the multifaceted optical element 1. The receiving mirror focuses the returned laser signal before it enters the detection signal receiving unit 3. Finally, the digital processing unit 4 converts the optical signal into an electrical signal, ultimately achieving target imaging.

[0039] The lidar transceiver system based on multi-faceted coaxial optical elements in this embodiment features a parallel coaxial transmitter and reflector, resulting in a simple and compact structure that effectively reduces the mass and volume of the lidar transceiver system. It also offers advantages such as integration, miniaturization, and modularity. Since multiple optical surfaces are fabricated onto the same optical substrate material, off-axis deviations caused by external factors such as stress and thermal deformation are avoided, ensuring a highly stable operating environment. The transmitter and reflector are naturally coaxial, eliminating the need for optical axis adjustment and simplifying assembly and adjustment.

[0040] See details Figure 5 In a preferred embodiment, the first optical surface 12 and the third optical surface 16 are disposed on the same surface of the substrate 11, and the distance between the second optical surface 13 and the first optical surface 12 is smaller than the distance between the fourth optical surface 17 and the third optical surface 16. Accordingly, the substrate portion connecting the second optical surface 13 and the fourth optical surface 17 is connected by an inclined plane, resulting in consistent reflectivity and thermal properties, which can maximize the optical performance of the system.

[0041] Furthermore, in this embodiment, a plurality of first connecting portions 111 are provided between the second optical surface 13 and the substrate 11 in the circumferential direction, and a first exit pupil 15 is formed between two adjacent first connecting portions 111. A plurality of second connecting portions 112 are provided between the fourth optical surface 17 and the substrate 11 in the circumferential direction, and a second entrance pupil 18 is formed between two adjacent second connecting portions 112. See details. Figure 4 There are three first connecting parts 111 and three second connecting parts 112, forming a three-point support connection, which has a simple structure and good reliability. Of course, in other embodiments, the number of first connecting parts 111 and second connecting parts 112 can also be adjusted.

[0042] In a preferred embodiment, the first optical surface 12, the second optical surface 13, the third optical surface 16, and the fourth optical surface 17 are all high-order aspherical reflecting surfaces. By setting each optical surface as a high-order aspherical reflecting surface, the multiple degrees of freedom inherent in high-order aspherical surfaces can be further utilized, enabling each reflecting element to have the advantages of strong aberration correction capability and light weight.

[0043] Furthermore, in this embodiment, the first optical surface 12, the second optical surface 13, the third optical surface 16, and the fourth optical surface 17 are all provided with high reflectivity films, and the reflectivity of the high reflectivity films is greater than 98%. By depositing high reflectivity films, the reflectivity can be improved more effectively, thereby further enhancing the light transmission capability. Preferably, a high reflectivity film that is not selective for wavelength can be deposited.

[0044] Furthermore, in this embodiment, the side surfaces (or circumferential surfaces) of both the second optical surface 13 and the fourth optical surface 17 are provided with a matte varnish layer, which can suppress stray light. Preferably, the surface of the substrate 11 can also be coated with a matte varnish to suppress stray light.

[0045] In a preferred embodiment, both the first entrance pupil 14 and the second exit pupil 19 are circular through-hole structures, with the first entrance pupil 14 located at the center of the first optical surface 12 and the second exit pupil 19 located at the center of the third optical surface 16.

[0046] The material of the multifaceted optical element 1 can be aerospace-grade aluminum alloy (e.g., AL6061) or microcrystalline aluminum, possessing excellent mechanical, machinability, and optical properties. By using the same material to fabricate each optical surface and substrate 11, it is possible to effectively ensure that each reflective element has the same physical properties under the same environment, thereby more effectively guaranteeing the efficiency and capability of light transmission, especially providing a reliable and effective guarantee for ensuring that the laser emitting unit 2 ultimately outputs parallel light. In addition, using the same material to fabricate each reflective element also facilitates rapid manufacturing.

[0047] The field of view of the lidar transceiver system based on multifaceted optical elements of the present invention is less than 150 μ rad, and the compact system of the present invention is not selective for wavelength.

[0048] The above-described configuration makes the compact system of the present invention widely applicable and scalable to suit the needs of different optical systems.

[0049] The present invention will be illustrated below with examples. Table 1 below shows the system specifications.

[0050]

[0051] Table 1 The first optical surface 12 is denoted as S01, the second optical surface 13 as S02, the third optical surface 16 as S03, and the fourth optical surface 17 as S04. The reference plane is the center point of the right surface of the first optical surface 17. Based on the above system technical specifications, the surface shape of each reflective element in this invention is designed, and the optimized parameters of each reflective surface in Table 2 are obtained.

[0052]

[0053] Table 2 See details Figure 6 In this embodiment, the detection signal receiving unit 3 is not located at the focal point of the optical system composed of the third optical surface 13 and the fourth optical surface 17. The detection signal receiving unit 3 has a built-in lens group to collimate and focus the laser emitted from the fourth optical surface 17, thereby further reducing aberrations, improving imaging quality, and enhancing detection capabilities.

[0054] See details Figure 7 In this embodiment example, the laser emitting unit 2 can use a commercially available laser emitting device that meets the performance requirements, and no specific limitation is made. In the laser emitting section, the first optical surface 12 and the second optical surface 13 form a Cassegrain beam expander system.

[0055] See details Figure 8 and Figure 9 Finally, through computer optical simulation software, the optical modulation function curve and wavefront difference diagram of the example system of this invention were obtained. It can be seen that the system modulation function value is close to the diffraction limit within the specified field of view. The imaging quality is good and meets the requirements of single-photon laser ranging.

[0056] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments, without departing from the scope of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the scope of the present invention, should fall within the protection scope of the present invention.

Claims

1. A lidar transceiver system based on a multi-faceted coaxial optical element, characterized in that: The device includes a multi-faceted optical element (1), which includes a substrate (11) and a emitting mirror and a reflecting mirror disposed on the substrate (11). The emitting mirror includes a first optical surface (12) and a second optical surface (13) arranged coaxially. The first optical surface (12) is provided with a first entrance pupil (14), and the second optical surface (13) is provided with a first exit pupil (15) between the substrate (11). The reflecting mirror includes a third optical surface (16) and a fourth optical surface (17) arranged coaxially. The fourth optical surface (17) is provided with a second entrance pupil (18) between the substrate (11), and the third optical surface (16) is provided with a second exit pupil (19).

2. The lidar transceiver system based on multifaceted coaxial optical elements according to claim 1, characterized in that: The first optical surface (12) and the third optical surface (16) are located on the same surface of the substrate (11), and the distance between the second optical surface (13) and the first optical surface (12) is smaller than the distance between the fourth optical surface (17) and the third optical surface (16).

3. The lidar transceiver system based on multifaceted coaxial optical elements according to claim 1, characterized in that: The second optical surface (13) is provided with a plurality of first connecting parts (111) between the circumference of the second optical surface (13) and the substrate (11), and a first exit pupil (15) is formed between two adjacent first connecting parts (111). The fourth optical surface (17) is provided with a plurality of second connecting parts (112) between the circumference of the fourth optical surface (17) and the substrate (11), and a second entrance pupil (18) is formed between two adjacent second connecting parts (112).

4. The lidar transceiver system based on a multifaceted coaxial optical element according to any one of claims 1 to 3, characterized in that: The first optical surface (12), the second optical surface (13), the third optical surface (16) and the fourth optical surface (17) are all high-order aspherical reflective surfaces.

5. The lidar transceiver system based on multifaceted coaxial optical elements according to claim 4, characterized in that: The first optical surface (12), the second optical surface (13), the third optical surface (16) and the fourth optical surface (17) are all provided with a high reflectivity film layer, and the reflectivity of the high reflectivity film layer is greater than 98%.

6. The lidar transceiver system based on a multifaceted coaxial optical element according to claim 4, characterized in that: The side surfaces of the second optical surface (13) and the fourth optical surface (17) are both provided with a matte varnish layer.

7. The lidar transceiver system based on a multi-faceted coaxial optical element according to any one of claims 1 to 3, characterized in that: The first entrance pupil (14) and the second exit pupil (19) are both circular through-hole structures. The first entrance pupil (14) is located at the center of the first optical surface (12), and the second exit pupil (19) is located at the center of the third optical surface (16).

8. The lidar transceiver system based on a multifaceted coaxial optical element according to any one of claims 1 to 3, characterized in that: The material of the multifaceted optical element (1) is aerospace aluminum alloy.

9. The lidar transceiver system based on a multifaceted coaxial optical element according to any one of claims 1 to 3, characterized in that: The material of the multifaceted optical element (1) is microcrystalline aluminum.

10. The lidar transceiver system based on a multifaceted coaxial optical element according to any one of claims 1 to 3, characterized in that: It also includes a laser emitting unit (2), a detection signal receiving unit (3) and a digital processing unit (4). The laser emitting unit (2) is configured to correspond to the first entrance pupil (14), the detection signal receiving unit (3) is configured to correspond to the second exit pupil (19), and the digital processing unit (4) is connected to the detection signal receiving unit (3).

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