Uniform light sheet, light emitting unit for lidar, and lidar

Abstract

The present application provides a kind of light uniformity sheet, comprising: curved substrate, the substrate has first side surface and second side surface, at least one of the first side surface and second side surface is Fresnel surface, the substrate is made of light-transmitting material;And light uniformity structure, the light uniformity structure is periodically arranged on the first side surface and / or the second side surface, wherein the light uniformity structure is integrally formed on the curved substrate.The present application also provides a light emitting unit for lidar and lidar.

Description

Technical Field

[0001] This disclosure generally relates to the field of optical technology, and more particularly to a light homogenizer, a light emitting unit that can be used in lidar, and lidar. Background Technology

[0002] A light homogenizer is a common optical device used to generate a uniform light field within a one-dimensional or two-dimensional scale. Light homogenizers typically have a flat substrate with optical microstructures to homogenize the incident light beam, thereby projecting a relatively uniform light field.

[0003] However, when this type of beam homogenizer is used in specific applications, such as lidar, it can produce some undesirable optical modulation phenomena. For example, in directions where no beam change or deflection is expected, a certain degree of deflection may actually occur.

[0004] The content in the background section is merely technology known to the public and does not necessarily represent existing technology in this field. Summary of the Invention

[0005] The purpose of this invention is to provide an improved light homogenizer that can be used in some special applications, such as lidar.

[0006] In view of at least one deficiency of the prior art, the present invention provides a light homogenizer, comprising:

[0007] A curved substrate having a first side surface and a second side surface, at least one of the first side surface and the second side surface being a Fresnel surface, the substrate being made of a light-transmitting material; and

[0008] A light-uniforming structure, wherein the light-uniforming structure is periodically arranged on the first side surface and / or the second side surface.

[0009] The uniform light structure is integrally formed on the curved substrate.

[0010] According to one aspect of the invention, the first and second side surfaces of the substrate are both Fresnel surfaces, and the homogenizing structure is located on the first side surface.

[0011] According to one aspect of the invention, the Fresnel surface comprises a plurality of segments, and the angle of the transition surface between two adjacent segments is determined according to a preset incident angle at that location.

[0012] According to one aspect of the invention, the light-uniforming structure includes a cylindrical mirror, preferably an irregularly shaped cylindrical mirror.

[0013] According to one aspect of the invention, a plurality of cylindrical mirrors are arranged in parallel on the first side surface and / or the second side surface, and adjacent cylindrical mirrors have recesses with shapes corresponding to the cylindrical mirrors.

[0014] According to one aspect of the invention, the angle of incidence is greater at locations on the Fresnel surface that are farther from its center.

[0015] According to one aspect of the invention, at least a portion of the Fresnel surface has an optical film layer with absorption properties.

[0016] According to one aspect of the invention, the curvature of the curved substrate and the homogenizing structure are configured such that: after a parallel beam of light passes through the homogenizing sheet, it remains parallel in a first plane and is diverged in a second plane, wherein the first plane is perpendicular to the second plane.

[0017] The present invention also provides an optical emitting unit that can be used in lidar, comprising:

[0018] A laser array, comprising multiple lasers, configured to emit a probe beam;

[0019] An optical shaping unit, disposed downstream of the optical path of the laser array, is configured to receive and shape the probe beam emitted by the laser; and

[0020] The homogenizer described above is disposed downstream of the optical path of the optical shaping unit and configured to receive the shaped probe beam from the collimating unit and emit it after homogenization.

[0021] According to one aspect of the invention, the optical shaping unit includes a collimating lens or a collimating lens group, the laser includes a VCSE1 laser, and the laser array includes multiple rows of lasers, with one row of lasers being driven to emit light at a time.

[0022] The present invention also provides a lidar, comprising:

[0023] The light emitting unit as described above;

[0024] The receiving unit is configured to receive the echo of the detection beam emitted by the optical emitting unit after it is reflected on the obstacle;

[0025] The processing unit, coupled to the light emitting unit and the receiving unit, is configured to obtain the distance to the obstacle based on the flight time or phase of the echo.

[0026] According to one aspect of the present invention, the lidar is a solid-state lidar.

[0027] The present invention also provides a solid-state lidar, comprising:

[0028] The light emitting unit includes:

[0029] A laser array, comprising multiple lasers, configured to emit a probe beam;

[0030] An optical shaping unit, disposed downstream of the optical path of the laser array, is configured to receive and shape the probe beam emitted by the laser; and

[0031] A homogenizer is disposed downstream of the optical path of the optical shaping unit and configured to receive the shaped probe beam from the collimating unit and then emit it after homogenization.

[0032] The receiving unit is configured to receive the echo of the detection beam emitted by the optical emitting unit after it is reflected on the obstacle;

[0033] The processing unit, coupled to the light emitting unit and the receiving unit, is configured to obtain the distance to the obstacle based on the flight time of the echo. Attached Figure Description

[0034] The accompanying drawings, which form part of this disclosure, are used to provide a further understanding of this disclosure. The illustrative embodiments of this disclosure and their descriptions are used to explain this disclosure and do not constitute an undue limitation of this disclosure. In the drawings:

[0035] Figure 1 A light-diffusing sheet structure is shown;

[0036] Figure 2 A perspective view of a light-diffusing sheet according to an embodiment of the present invention is shown;

[0037] Figure 3 A top view of the light-diffusing plate is shown;

[0038] Figure 4 It shows the use of Figure 2 and Figure 3 A schematic diagram of the light field projected by the homogenizer;

[0039] Figure 5 A schematic diagram of a light-uniforming structure according to a preferred embodiment of the present invention is shown;

[0040] Figure 6 A schematic diagram of a Fresnel surface according to a preferred embodiment of the present invention is shown;

[0041] Figure 7 A schematic diagram of a Fresnel surface according to a preferred embodiment of the present invention is shown;

[0042] Figure 8 An optical emitting unit for use in lidar is shown according to a preferred embodiment of the present invention;

[0043] Figure 9 Patterns showing specific distortion effects produced by multiple laser arrays on a receiving plane at a certain distance from the homogenizer are illustrated.

[0044] Figure 10 A lidar according to a preferred embodiment of the present invention is shown. Detailed Implementation

[0045] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0046] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are only for the convenience of describing the 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, and therefore should not be construed as a limitation of the invention. 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 indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0047] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, an electrical connection, or a connection that allows for communication; 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.

[0048] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0049] The following disclosure provides many different embodiments or examples for implementing various structures of the invention. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the invention. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, examples of various specific processes and materials are provided in this invention, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0050] Figure 1 A light homogenizer structure is shown in the figure. The bottom right side of the structure is roughly flat, and multiple cylindrical mirrors are arranged periodically and close to each other on the upper left side. For a parallel light beam incident on it, the light homogenizer will diffuse the parallel light beam, forming an outgoing light beam with a certain degree of divergence, thereby producing a uniform light field.

[0051] Figure 2 A perspective view of a light-diffusing sheet 10 according to an embodiment of the present invention is shown. Figure 3 A top view of the light-diffusing plate 10 is shown. See below for reference. Figure 2 and Figure 3 Detailed description. For example... Figure 2 and Figure 3 As shown, the homogenizer 10 has a curved substrate 11. (The last sentence appears to be incomplete and possibly contains errors.) Figure 1 The structures of the light-diffusing plates shown are different. Figure 2 and Figure 3 The substrate 11 of the light homogenizer 10 shown is curved. The substrate 11 has a first side surface 111 and a second side surface 112, at least one of which is a Fresnel surface. By making at least one of the first side surface 111 and the second side surface 112 a Fresnel surface, the thickness of the light homogenizer 10 can be reduced. Additionally, the substrate 11 is made of a light-transmitting material to allow light to pass through. Figure 2 and Figure 3 In the embodiment shown, the first side surface 111 and the second side surface 112 of the substrate 11 are both Fresnel surfaces. However, the present invention is not limited to this. It is also possible to make only one of the first side surface 111 or the second side surface 112 a Fresnel surface. These are all within the protection scope of the present invention.

[0052] exist Figure 2 In this context, the x-direction is approximately parallel to the longitudinal direction of the curved base 11. For example, when the base is approximately a symmetrical arc or curve, the x-direction is parallel to the tangent of the middle portion of the base. The y-direction is perpendicular to the x-direction in the horizontal plane, and the z-direction is a vertical direction, perpendicular to both the x and y directions.

[0053] like Figure 2 As shown, the homogenizer 10 further includes a homogenizing structure 12, which is periodically arranged on the first side surface 111 and / or the second side surface 112. The homogenizing structure 12 is configured such that the light beam incident on the homogenizer 10 is homogenized in at least one dimension (e.g., having a certain divergence), or it can be homogenized in two dimensions. For example, for a parallel light beam incident on the homogenizer 10 and located in the xy plane, the homogenizing structure 12 can cause the parallel light beam to diffuse only in the z direction after transmission, producing a certain divergence angle (in the yz plane), while remaining undivered in the xy plane (or still remaining parallel, but the cross-sectional size of the optical path has changed); or it can cause the parallel light beam to diffuse in both the xy plane and the z direction after transmission, i.e., having a certain divergence angle in the xy plane and also having a certain divergence angle in the yz plane. These are all within the scope of protection of this invention. The homogenizing structure can be formed on the Fresnelized side surface or on the non-Fresnelized surface.

[0054] exist Figure 2 In one embodiment, the light-diffusing structure 12 includes a cylindrical mirror on the first side surface 111 of the light-diffusing sheet 10, the cylindrical mirror being along... Figure 2 Extending in the x-direction, it is distributed on the first Fresnelized side surface 111. This cylindrical mirror is basically similar to Figure 1 The cylindrical mirror on the homogenizer shown is different in that... Figure 2 In this structure, cylindrical mirrors are distributed on a curved substrate 11, and at least one side surface of the substrate is Fresnelized. Besides cylindrical mirrors, other forms of homogenizing structures 12 can also be used, such as irregularly shaped cylindrical mirrors.

[0055] According to an embodiment of the present invention, the uniform light structure 12 is integrally formed on the curved substrate 11. For example, the substrate is made of glass, and the corresponding uniform light structure can be etched on its surface. Alternatively, photoresist can be applied to the glass substrate, and then imprinted using a corresponding mold to form the photoresist into the predetermined shape of the uniform light structure 12. Then, a curing process is performed to solidify the photoresist, thereby making the uniform light structure integral with the substrate.

[0056] exist Figure 2 and Figure 3 In this embodiment, the first side surface 111 and the second side surface 112 of the substrate 11 are both Fresnel surfaces, and the light-uniforming structure 12 is located on the first side surface 111. Of course, the light-uniforming structure 12 can also be formed on the second side surface 112, or the light-uniforming structure 12 can be formed on both the first side surface 111 and the second side surface 112 simultaneously, depending on the specific optical design, which will not be elaborated here.

[0057] According to a preferred embodiment of the invention, the curvature of the curved substrate 11 and the homogenizing structure 12 are configured such that: after a parallel beam of light passes through the homogenizing sheet, it remains parallel in a first plane and diverges in a second plane, wherein the first plane is perpendicular to the second plane. Figure 4 As shown, the incident light beam L1 on the first side surface 111 of the homogenizer 10 is a parallel beam in the yz plane (it can also have a certain scale in the x direction). The curvature of the substrate 11 and the homogenizing structure are designed such that after the incident light beam L1 passes through the homogenizer 10, the outgoing light beam L2 diverges significantly in the yz plane (i.e., the second plane), but does not diverge significantly in the xy plane (the first plane). Furthermore, when the incident light beam L1 has a certain scale in the x direction, the outgoing light beam L2 remains parallel in the xy plane, or its scale in the x direction remains unchanged. Therefore, the angular expansion of YZ is achieved through a one-dimensional stretched aspherical lens array.

[0058] According to one embodiment of the invention, adjacent homogenizing structures (e.g., cylindrical mirrors) 12 are spaced apart from each other. Figure 5 As shown, adjacent cylindrical mirrors 12 are spaced apart by a certain distance, and preferably, a recess 13 is provided between adjacent cylindrical mirrors 12, the shape of which corresponds to the cylindrical mirror 12. By separating adjacent light-diffusing structures 12, the difficulty of processing can be reduced. Figure 1 The area where the two cylindrical mirrors meet is prone to producing a transition arc during processing, resulting in stray light. Figure 5 In one embodiment, to reduce processing difficulty and stray light caused by processing deviations, the cylindrical mirror array is changed to a wave-shaped arrangement.

[0059] According to a preferred embodiment of the present invention, when performing Fresnel design on the first side surface 111 and / or the second side surface 112 of the light homogenizer 10, a preset incident angle is provided for each position on the surface, and the angle of the Fresnel surface at each position is determined according to the preset incident angle at that position. For example... Figure 6 As shown, taking the first side surface 111 as an example, its Fresnelized surface has multiple segments, such as... Figure 6 As shown in a1, a2, and a3, there are transition surfaces between the segments. In existing Fresnel surfaces, this transition surface is typically a 90-degree transition surface, meaning the transition surface is substantially perpendicular to the two adjacent segments. According to a preferred embodiment of the invention, the transition surface is designed based on the incident angle of the incident light at that location. The farther the location on the Fresnel surface is from its center, the larger the incident angle. Figure 6 As shown, the straight line OO is the central axis of the homogenizer 10 in the x-direction, and the incident angle of the incident light is characterized by the angle θ between the light ray incident on this part and the straight line OO. According to another preferred embodiment of the present invention, the transition surface coincides with the path of the incident light at this part.

[0060] According to a preferred embodiment of the invention, at least a portion of the Fresnel surface has an optical film layer with absorption properties. For example... Figure 7 As shown, the first side surface 111 and the second side surface 112 of the homogenizer 10 are both Fresnel surfaces, and an optical film layer 14 with absorption properties is provided on the transition surface between each segment of each Fresnel surface. By providing the optical film layer 14 with absorption properties, stray light can be effectively absorbed or reduced.

[0061] The light homogenizer described above can be very advantageously applied in lidar. Figure 8 An optical emitting unit 20 for use in lidar according to the present invention is shown, which is described in detail below with reference to the accompanying drawings.

[0062] like Figure 8 As shown, the light emitting unit 20 includes a laser array 21, an optical shaping unit 22, and a light homogenizer 10 as described above. The laser array 21 includes multiple lasers, constituting a light source, such as... Figure 8 Multiple lasers, including lasers 21-1, 21-2, and 21-3, are shown in the diagram and configured to emit a probe beam LL. According to a preferred embodiment of the invention, the lasers include a VCSE1 laser, and the emitted probe beam LL has a certain divergence angle.

[0063] An optical shaping unit 22 is disposed downstream of the optical path of the laser array 21 and configured to receive and shape the probe beam LL emitted by the laser 21. A homogenizer 10 is disposed downstream of the optical shaping unit 22 and configured to receive the shaped probe beam from the optical shaping unit 22, homogenize it, and then emit it. According to one embodiment of the present invention, the optical shaping unit 22 includes a collimating lens or a collimating lens group, and the laser array 21 is disposed on the focal plane of the collimating lens or collimating lens group, so that the beam emitted from the laser array 21 is shaped into a parallel beam or a substantially parallel beam after passing through the collimating lens or collimating lens group. According to a preferred embodiment of the present invention, after the parallel beam is incident on the homogenizer 10 and transmitted through it, it does not undergo deflection or diffusion when observed in the xy plane and remains parallel in the xy plane, but when observed in the yz plane, diffusion occurs, such as... Figure 4 As shown, after passing through the homogenizer, the light beam continues to propagate, incident on the external obstacle OB, and undergoes diffuse reflection.

[0064] According to a preferred embodiment of the invention, the laser array 21 includes multiple columns of lasers, each column including one or more lasers. The light emitting unit 20 may further include a controller coupled to each or each column of lasers, configured to drive one column of lasers to emit light at a time, wherein the probe beam emitted by each column of lasers is collimated, for example, in… Figure 4 The parallel beam L1 shown is represented by multiple laser arrays distributed in... Figure 4 At different coordinates along the x-axis, multiple beams L1 illuminate the homogenizer 10 at different positions along the x-axis. After passing through the homogenizer, a certain degree of diffusion occurs in the yz plane. Figure 9 The diagram illustrates a pattern of specific distortion effects produced by multiple laser arrays on a receiving plane at a certain distance from a homogenizer. In this pattern, the central straight line represents the homogenizing effect produced by a parallel beam L1 incident at position OO, the central axis of the homogenizer in the x-direction. Figure 4 As shown in the diagram, the parabolas on both sides represent the homogenizing effect produced by the parallel beam L1 incident on both sides of the central axis OO in the x-direction of the homogenizer.

[0065] In the above embodiments, the beam homogenizer 10 enables the direct projection of a linear array covering the entire required field of view (FOV), which can be used to realize a solid-state lidar system, thereby improving product reliability. Furthermore, the optical devices involved in this invention are used in conjunction with a VCSEL light source. VCSEL arrays possess excellent power density, conversion efficiency, and spacing. VCSELs offer great flexibility in layout design, including pixel size, dimensions, and spacing, as well as specific addressable functions. High-power VCSELs are less susceptible to single emitter failures, are more stable over their operating temperature range, and are easy to integrate. Enhanced functionality and eye protection are provided through the integration of functional safety standards, achieving high reliability.

[0066] The light emitted by the VCSEL, with a certain divergence angle, is shaped into parallel light by a collimating lens group and then incident on the optical structure of this invention. This invention's structure superimposes a one-dimensional stretched cylindrical / aspherical mirror array onto a curved surface, which can shape a circular light spot at each angle into an elongated light spot covering the entire vertical field of view, while maintaining the XY plane light rays in their original direction. To achieve thinner components, Fresnel shaping is performed.

[0067] The light source emits light with a certain divergence angle, which is collimated by a collimating lens group and then incident on a homogenizer. The homogenizer modulates the incident light, causing it to continue propagating in the original direction in the XY plane and expand one-dimensionally in the YZ plane, forming a linear light spot with a field of view (FOV) of 50–160 degrees. Only one line can be projected at a time. The collimated light, after passing through the optical structure designed in this invention, can form a pattern with a specific distortion effect on a planar receiver, which spatially appears as a linear array spaced at certain angles. Each time, one column of the VCSEL array is driven to light up, and after collimation by the collimating lens group, a parallel light at a specific angle is obtained. This light is then shaped by the homogenizer into a linear light spot with the same angle as the incident light, thereby enabling a linear scanning lidar without moving parts, improving the reliability of the lidar and reducing costs.

[0068] Furthermore, in the context of this invention, "uniform light" refers to the effect of diffusion along one or two directions, and is not limited to forming a two-dimensional uniform light field, for example... Figure 4 The situation shown is also within the meaning of "uniform light" in this invention.

[0069] like Figure 10As shown, the present invention also provides a lidar 30 for detecting the surrounding three-dimensional environment. The lidar 30 includes a light emitting unit 20, a receiving unit 32, and a processing unit 33 as described above. The light emitting unit 20 is configured to emit a detection beam L around the lidar. The detection beam L undergoes diffuse reflection on an obstacle OBJ, and a portion of the echo L' returns to the lidar 30 and is received by the receiving unit 32. The receiving unit 32 includes a photoelectric sensor, such as an avalanche diode (APD), a single-photon avalanche diode (SPAD), or a SiPm, which can convert the echo L' into an electrical signal. The converted electrical signal undergoes appropriate signal processing, such as filtering, amplification, and analog-to-digital conversion, before being received by the processing unit 33. The processing unit 33 is coupled to the light emitting unit 20 and the receiving unit 32, thereby acquiring information about the detection beam L and the echo L', including emission time, reception time, wavelength, pulse width, and phase. Therefore, information about obstacles, such as the presence of obstacles, the distance to the obstacle, its orientation, and reflectivity, can be calculated based on the information about the detection beam L and the echo L'. Preferably, the processing unit 33 is configured to obtain the distance to the obstacle based on the flight time of the echo L'.

[0070] According to a preferred embodiment of the present invention, the lidar 30 is a solid-state lidar, i.e., it does not have a rotating optomechanical rotor. The processing unit 33 of the lidar can also be configured to determine the distance to the obstacle based on the phase of the echo L'.

[0071] The present invention also provides a solid-state lidar, comprising:

[0072] The light emitting unit includes:

[0073] A laser array, comprising multiple lasers, configured to emit a probe beam;

[0074] An optical shaping unit, disposed downstream of the optical path of the laser array, is configured to receive and shape the probe beam emitted by the laser; and

[0075] A beam homogenizer is disposed downstream of the optical path of the optical shaping unit, configured to receive the shaped probe beam from the collimating unit, homogenize it, and then emit it. The beam homogenizer is not limited to the beam homogenizer 10 described above.

[0076] The receiving unit is configured to receive the echo of the detection beam emitted by the optical emitting unit after it is reflected on the obstacle;

[0077] The processing unit, coupled to the light emitting unit and the receiving unit, is configured to obtain the distance to the obstacle based on the flight time of the echo.

[0078] One of the improvements of this solid-state lidar is the application of a beam homogenizer in the lidar, which allows a smaller beam to cover a larger field of view.

[0079] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A light homogenizer, comprising: A curved substrate having a first side surface and a second side surface, at least one of the first side surface and the second side surface being a Fresnel surface, the substrate being made of a light-transmitting material; and A light-uniforming structure, wherein the light-uniforming structure is periodically arranged on the first side surface and / or the second side surface. The uniform light structure is integrally formed on the curved substrate; The Fresnel surface comprises multiple segments, and the angle of the transition surface between two adjacent segments is determined according to a preset incident angle at that position. The curvature of the curved substrate and the homogenizing structure are configured such that: after a parallel beam of light passes through the homogenizer, it remains parallel in a first plane and is diverged in a second plane, wherein the first plane is perpendicular to the second plane.

2. The light-diffusing sheet as claimed in claim 1, wherein the first side surface and the second side surface of the substrate are both Fresnel surfaces, and the light-diffusing structure is located on the first side surface.

3. The light-diffusing sheet as described in claim 1 or 2, wherein the light-diffusing structure includes a cylindrical mirror.

4. The light-diffusing plate as described in claim 3, wherein the cylindrical mirror is an irregularly shaped cylindrical mirror.

5. The light-diffusing sheet as claimed in claim 3, wherein a plurality of cylindrical mirrors are arranged in parallel on the first side surface and / or the second side surface, and adjacent cylindrical mirrors have recesses with shapes corresponding to the cylindrical mirrors.

6. The light homogenizer as claimed in claim 1, wherein the incident angle is greater at locations on the Fresnel surface farther from its center.

7. The light homogenizer as claimed in claim 1 or 2, wherein at least a portion of the Fresnel surface has an optical film layer with absorption properties.

8. A light emitting unit that can be used in lidar, comprising: A laser array, comprising multiple lasers, configured to emit a probe beam; An optical shaping unit is located downstream of the optical path of the laser array and is configured to receive and shape the probe beam emitted by the laser. and The homogenizer as described in any one of claims 1-7 is disposed downstream of the optical path of the optical shaping unit and configured to receive the shaped probe beam from the optical shaping unit and emit it after homogenization.

9. The light emitting unit of claim 8, wherein the optical shaping unit includes a collimating lens or a collimating lens group, the laser includes a VCSE1 laser, and the laser array includes multiple rows of lasers, wherein one row of lasers is driven to emit light at a time.

10. A lidar, comprising: The light emitting unit as described in claim 8 or 9; The receiving unit is configured to receive the echo of the detection beam emitted by the optical emitting unit after it is reflected on the obstacle; The processing unit, coupled to the light emitting unit and the receiving unit, is configured to obtain the distance to the obstacle based on the flight time or phase of the echo.

11. The lidar as claimed in claim 10, wherein the lidar is a solid-state lidar.

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