Light-transmitting housing of lidar and lidar

Abstract

The application provides a light-transmitting shell of a laser radar and the laser radar, the light-transmitting shell is rotationally symmetrical about a rotation shaft of the laser radar, an inner surface of the light-transmitting shell is parabolic, and the inner surface is a parabola on a section plane through the rotation shaft; the light-transmitting shell further comprises a light-eliminating structure, the light-eliminating structure is arranged at a preset region at the top of the light-transmitting shell, and the preset region can enable light beams reflected by the inner surface and converging at a focal point of the parabolic shape to enter the light-eliminating structure. The application can eliminate stray light generated by reflection of the inner surface of the light-transmitting shell and improve the overall performance of the laser radar.

Description

Technical Field

[0001] This invention relates to the field of lidar technology, and more particularly to a light-transmitting housing for a lidar and the lidar itself. Background Technology

[0002] A lidar is a radar system that detects targets by emitting laser beams. The transparent housing is a crucial component of a lidar system, serving not only to support and protect it but also significantly impacting the overall performance and reliability of the device.

[0003] Currently, the light-transmitting shell of lidar typically has a certain thickness. Since the refractive index of the light-transmitting shell material is different from that of air, when the emitted light beam passes through the inner wall of the light-transmitting shell, the inner wall of the light-transmitting shell will reflect the light beam and generate stray light. This stray light will affect the beam transmission characteristics, thereby reducing the overall performance of the lidar. Summary of the Invention

[0004] This invention provides a light-transmitting housing for a lidar and a lidar itself, in order to solve the problem of stray light generated by reflection from the inner wall of the light-transmitting housing affecting the beam transmission characteristics of the lidar.

[0005] In a first aspect, embodiments of the present invention provide a light-transmitting housing for a lidar, the light-transmitting housing having a rotationally symmetric structure about the rotation axis of the lidar, the inner surface of the light-transmitting housing being parabolic, and the inner surface being parabolic on the cross-sectional plane passing through the rotation axis;

[0006] The light-transmitting shell also includes an extinction structure, which is set in a preset area on the top of the light-transmitting shell. The preset area allows light beams reflected from the inner surface and converging at the focal point of the parabolic shape to enter the extinction structure.

[0007] In one possible implementation, the equation of the parabolic shape is:

[0008]

[0009] In the equation, the z-axis of the coordinate system is parallel to the rotation axis, and the plane containing the x-axis and y-axis of the coordinate system is parallel to the radar scanning plane; f is the focal length of the parabolic shape, R is the top rotation radius of the inner surface, and R0 is the bottom rotation radius of the inner surface.

[0010] In one possible implementation, the parabolic shape is a conic surface with a vertex radius of curvature of 2f and a conic coefficient of -1.

[0011] In one possible implementation, the origin of the coordinate system is the focus of a parabola, the z-axis of the coordinate system coincides with the rotation axis, the x-axis of the coordinate system corresponds to 0° of the radar scanning plane, and the y-axis of the coordinate system corresponds to 90° of the radar scanning plane.

[0012] In one possible implementation, the extinction structure is a groove structure.

[0013] In one possible implementation, the groove structure is either an annular groove or a polygonal groove.

[0014] In one possible implementation, the surface of the matting structure is covered with a matting material.

[0015] In one possible implementation, the material of the light-transmitting outer shell is polycarbonate.

[0016] In a second aspect, embodiments of the present invention provide a lidar, including a light-transmitting housing as described in the first aspect or any possible implementation thereof.

[0017] In one possible implementation, the lidar is a single-line lidar.

[0018] This invention provides a light-transmitting housing for a lidar and the lidar itself. By employing a light-transmitting housing with a parabolic inner surface, stray light reflected from the inner surface of the housing is focused at the focal point of the parabolic shape. Furthermore, an extinction structure located in a predetermined area on the top of the housing eliminates the stray light reflected from the inner surface that is focused at the focal point of the parabolic shape. This eliminates stray light interference, solves the problem of stray light affecting beam transmission characteristics, and improves the overall performance of the lidar. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of stray light generated by reflection from the spherical inner surface when a light beam passes through a light-transmitting shell, according to an embodiment of the present invention.

[0021] Figure 2 This is a schematic diagram showing how stray light generated by reflection from the parabolic inner surface when a light beam passes through a light-transmitting shell is eliminated by an extinction structure, according to an embodiment of the present invention.

[0022] Figure 3a This is a schematic diagram of the groove structure and the convergence point of reflected light provided in an embodiment of the present invention;

[0023] Figure 3b This is a schematic diagram of the matting structure using an annular groove provided in an embodiment of the present invention;

[0024] Figure 4 This is a schematic diagram illustrating the determination of the outer surface shape of the light-transmitting shell based on the principle of equal optical path length provided in an embodiment of the present invention;

[0025] Figure 5 This is a schematic diagram of the surface parameters of the light-transmitting shell provided in the embodiment of the present invention for the optimized design of optical sequence modes;

[0026] Figure 6 This is a schematic diagram illustrating the change in the center trajectory of the rotating scanning beam of the rotating mirror provided in an embodiment of the present invention;

[0027] Figure 7 This is a schematic diagram of the vertical and horizontal projection sections of the center beam at the scanning angle θ provided in an embodiment of the present invention;

[0028] Figure 8 This is a schematic diagram illustrating the beam divergence effect of the transparent shell on different scanning angles under focusing and defocusing conditions, provided by an embodiment of the present invention.

[0029] Figure 9a This is a schematic diagram of the optimized point array of the 0° field of view emission lens provided in an embodiment of the present invention;

[0030] Figure 9b This is a schematic diagram of the point array of light rays from a vertical cross-section of a 0° field of view provided in an embodiment of the present invention after passing through the emitting lens and the light-transmitting shell;

[0031] Figure 9c This is a schematic diagram illustrating the relationship between optical path difference and relative aperture provided in an embodiment of the present invention;

[0032] Figure 10a This is a schematic diagram of the emitted light spot shape under different scanning angles in the focusing situation provided by the embodiments of the present invention;

[0033] Figure 10b This is a schematic diagram of the emitted light spot shape under different scanning angles in the case of defocusing, provided by an embodiment of the present invention. Detailed Implementation

[0034] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of the invention. However, those skilled in the art will understand that the invention can be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods are omitted so as not to obscure the description of the invention with unnecessary detail.

[0035] To make the objectives, technical solutions, and advantages of the present invention clearer, specific embodiments will be described below in conjunction with the accompanying drawings.

[0036] As described in related technologies, the transparent housings of existing lidar systems, such as those for single-line lidar, typically employ cylindrical, conical, or spherical structures. However, because the refractive index of the lidar housing material differs from that of air, when the emitted light beam passes through the inner surface of the housing, the inner surface reflects the beam, generating stray light. This stray light affects the beam transmission characteristics, thereby reducing the overall performance of the lidar, such as its detection angular resolution and detection accuracy.

[0037] Taking a lidar with a light-transmitting shell featuring a spherical structure as an example, such as Figure 1 As shown, it illustrates a schematic diagram of stray light generated by reflection from the spherical inner surface when a light beam passes through the transparent housing. Figure 1 In the process, after the laser diode of the lidar emits a beam of light from A, the beam will be reflected by the rotating mirror of the lidar onto the inner surface of the light-transmitting shell. Since the refractive index of the light-transmitting shell material is different from that of air, the beam of light reflected by the rotating mirror will be reflected on the inner surface of the light-transmitting shell, generating stray light. This stray light will enter the detector A′ of the lidar through the receiving lens, thereby generating stray light interference.

[0038] In addition, the inner surface of a cylindrical, conical or spherical surface often has aberrations. For example, the spherical aberration of the inner surface of a sphere causes the stray light generated by the reflected beam to converge at different points on the focal plane, forming a large stray light region. After passing through this stray light region, the stray light undergoes further diffuse reflection or specular reflection, which further aggravates the stray light interference.

[0039] To address the problems of the prior art, embodiments of the present invention provide a light-transmitting housing for a lidar and a lidar. The light-transmitting housing for the lidar provided in the embodiments of the present invention will be described first.

[0040] This invention provides a light-transmitting housing for a lidar, which is rotationally symmetrical about the lidar's axis of rotation. The inner surface of the housing is parabolic, and its cross-section along the axis of rotation forms a parabola. The housing also includes an extinction structure disposed in a predetermined area at the top of the housing. This predetermined area allows light beams reflected from the inner surface and converging at the focal point of the parabola to enter the extinction structure.

[0041] In this embodiment of the invention, since a parabolic shape can focus reflected light beams to its focal point, a light-transmitting shell with a parabolic inner surface can be used to focus stray light reflected from the inner surface of the shell to the focal point. Furthermore, an extinction structure located in a predetermined area on the top of the shell eliminates the stray light reflected from the inner surface that converges to the focal point, thereby eliminating stray light interference, solving the problem of stray light affecting beam transmission characteristics, and improving the overall performance of the lidar. Figure 2 As shown, it illustrates a schematic diagram in which stray light generated by reflection from the inner surface of a parabolic shape when a light beam passes through a light-transmitting shell is eliminated by an extinction structure.

[0042] Furthermore, compared to using cylindrical, conical, or spherical inner surfaces, using parabolic inner surfaces can focus stray light reflected from the inner surface at the focal point of the parabolic surface, rather than at the focal plane of cylindrical, conical, or spherical surfaces. Since stray light focused at the focal point of the parabolic surface is easier to eliminate, it can not only reduce the difficulty of stray light elimination but also improve the stray light elimination effect, thereby greatly improving the overall performance of the lidar system.

[0043] In some embodiments, the equation of the parabolic shape can be expressed as follows:

[0044]

[0045] In the equation, the z-axis of the coordinate system is parallel to the rotation axis, and the plane containing the x-axis and y-axis of the coordinate system is parallel to the radar scanning plane; f is the focal length of the parabolic shape, R is the top rotation radius of the inner surface, and R0 is the bottom rotation radius of the inner surface.

[0046] The following provides a specific parabolic shape, which can be a conic surface. The vertex radius of curvature of the conic surface can be 2f, and the conic coefficient can be -1.

[0047] In some embodiments, the extinction structure can be a groove structure, such as an annular groove or a polygonal groove, or it can be a planar structure covered with an extinction material, which can be a material capable of absorbing laser beams.

[0048] Regarding the relative positions of the groove structure and the reflected light, such as Figure 3aAs shown, this diagram illustrates various groove structures and reflected light convergence points. The convergence point F of the reflected light can be positioned above, within, or below the entrance plane of the groove structure, as long as the reflected light beams with a solid angle Ω are all transmitted into the extinction structure. Furthermore, the inner wall of the groove structure can be a straight wall to facilitate fabrication and assembly. To better eliminate the signal from secondary reflections of stray light, the groove structure can employ an inner wall with an inwardly inclined trapezoidal or curved cross-section.

[0049] like Figure 3b As shown, a schematic diagram of an extinction structure employing an annular groove is provided. Figure 3b As can be seen, the preset area of ​​the annular groove 31 is the top center area of ​​the light-transmitting shell, which allows stray light 32 generated by reflection from the inner surface of the light-transmitting shell to enter the annular groove 31 and be eliminated.

[0050] In some embodiments, an matting material may be applied to the surface of the groove structure to better eliminate stray light.

[0051] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0052] This invention also provides a lidar that uses the aforementioned light-transmitting housing.

[0053] In some embodiments, the lidar may be a single-line lidar.

[0054] In some possible implementations, the outer surface of the light-transmitting shell can be designed to address the problem of light beam deflection and divergence caused by the refraction of the light beam by the light-transmitting shell. The relevant details are as follows:

[0055] Existing lidar housings, such as those for single-line lidar, typically have a certain thickness. Because the refractive index of the housing material differs from that of air, when the emitted light beam passes through the housing, the housing refracts the beam, causing it to deflect and diverge. This deflection and divergence affect the beam transmission characteristics, thereby reducing the overall performance of the lidar, such as its detection angle resolution and pointing accuracy.

[0056] This invention also provides a light-transmitting housing for a lidar, which is rotationally symmetric about the lidar's axis of rotation. The inner surface of the housing is parabolic, and its cross-section along the axis of rotation forms a parabola. The outer surface of the housing, on the cross-section along the axis of rotation, is an even-order aspherical shape corresponding to the parabola. The coordinate system used in the equation of the even-order aspherical shape has its z-axis parallel to the axis of rotation, and the planes containing the x-axis and y-axis of the coordinate system are parallel to the radar scanning plane. The even-order aspherical shape enables a light beam emitted from any height parallel to the x-axis within the xz cross-section along the axis of rotation to be emitted parallel to the x-axis.

[0057] In this embodiment of the invention, by using a light-transmitting shell with an even-order aspherical outer surface, the vertical deflection effect caused by the refraction of the light beam by the light-transmitting shell can be eliminated, thereby solving the problem of the beam deflection affecting the beam transmission characteristics, greatly improving the pointing accuracy of the lidar beam detection, and thus improving the overall performance of the lidar.

[0058] In some embodiments, the equation of the parabolic shape can be expressed as follows:

[0059]

[0060] Where f is the focal length of the parabolic shape, R is the top rotation radius of the inner surface, and R0 is the bottom rotation radius of the inner surface.

[0061] Correspondingly, the equation for the even-order aspherical shape corresponding to this parabolic shape can be expressed by the following formula:

[0062]

[0063] Where i is a positive integer greater than 2, z s Let h be the axial coordinate of an even-order aspherical shape. s Let r be the radial coordinate of an even-order aspherical shape. s Let k be the vertex radius of curvature of an even-order aspherical shape. s The conic coefficients of even-order aspherical shapes are a4, ..., a4. 2i Let a be the aspherical coefficients of each order. For example, when i is 5, the aspherical coefficients will be a4, a6, a8, a... 10 .

[0064] The following provides a specific parabolic shape, which can be a conic surface. The vertex radius of curvature of the conic surface can be 2f, and the conic coefficient can be -1.

[0065] In some embodiments, the specific parameters of the equation for an even-order aspherical shape can be determined according to the following conditions:

[0066]

[0067]

[0068] N P ×I P =n(N) P ×O P );

[0069] I P =(1,0,0),

[0070] Where P is the intersection point of a beam emitted from any height parallel to the x-axis and the inner surface, and the coordinates of point P are (x... P ,0,z P Q is the point where a beam of light emitted from any height parallel to the x-axis intersects the outer surface after refraction and propagation through the inner surface. The coordinates of point Q are (x...). Q ,0,z Q ); n is the refractive index of the transparent shell, and d is the thickness of the transparent shell along the x-axis. Let N be the distance from point P to point Q. P Let I be the normal vector corresponding to point P. P Let O be the incident vector corresponding to point P. P Let P be the outgoing vector corresponding to point P.

[0071] To facilitate understanding of the inner surface structure of the parabolic shape and the outer surface structure of the even-order aspherical shape of the aforementioned light-transmitting shell, their implementation principles are introduced below.

[0072] Based on the principle of equal optical path length and combined with the inner surface of a parabolic shape, the outer surface shape that can eliminate the vertical deflection effect caused by the refraction of light beams by the transparent shell can be derived. For example... Figure 4 As shown, Figure 4 This is a schematic diagram illustrating the determination of the outer surface shape of the light-transmitting shell based on the principle of equal optical path length. In this diagram, the rotation axis of the lidar coincides with the z-axis of the coordinate system, the xy-plane is parallel to the radar scanning plane, the x-axis corresponds to the 0° angle of the radar scan (directly forward), and the y-axis corresponds to the 90° angle of the radar scan. The origin of the coordinate system is located at the same position as the focus of the parabolic shape. As mentioned earlier, the equation of the parabolic shape is:

[0073]

[0074] See you again Figure 4 A beam of light emitted from any height parallel to the x-axis within the xz-section plane of the rotation axis intersects the inner surface at point P, and after refraction and propagation through the inner surface, intersects the outer surface at point Q, before exiting parallel to the x-axis, thus maintaining its original emission direction. Assume the coordinates of point P are (x... P ,0,zP To achieve the aforementioned transmission characteristics of the light beam, the coordinates of point Q (x...) Q ,0,z Q The equal optical path condition must be met:

[0075]

[0076] in, The distance from point P to point Q can be expressed as:

[0077]

[0078] According to the law of refraction, the normal vector, incident vector, and outgoing vector at point P satisfy the following relationship:

[0079] N P ×I P =n(N) P ×O P (3)

[0080] By combining formulas (2) and (3), we can solve for x. P The coordinates of point Q (x) are parameters Q ,0,z Q This allows us to determine the surface profile of the outer shell. It should be noted that the above limiting relationship is not limited to transparent shell materials with a constant refractive index; it also applies to transparent shell materials with a gradient refractive index. When using a transparent shell material with a gradient refractive index, the corresponding refractive index can be selected at the corresponding coordinates.

[0081] To further understand the inner surface structure of the parabolic shape and the outer surface structure of the even-order aspherical shape of the above-mentioned light-transmitting shell, a method for manufacturing the above-mentioned light-transmitting shell is provided below.

[0082] 1) Based on the top and bottom radii of rotation R and R0 of the inner surface of the transparent shell with refractive index n, and the relative positions of the rotating mirror, the emitting lens, and the light source, establish an optical sequence mode simulation model with the optical axis of the emitting lens as the principal optical axis, such as... Figure 5 As shown.

[0083] 2) Remove the light-transmitting outer shell or set the refractive index of the light-transmitting outer shell to 1, and determine the aperture A corresponding to 0° and the light-transmitting area of ​​the light-transmitting outer shell. p By using conventional lens optimization methods, the spherical aberration of the emitting lens is optimized to the minimum, that is, the spot diameter of the image plane is minimized.

[0084] 3) Represent the inner surface of the parabolic shape with focal length f using a conic surface, and set the radius of curvature at its vertex as r. p =2f, conic coefficient k = -1;

[0085] 4) Introduce a transparent outer shell with refractive index n. Based on the thickness d at the top of the outer shell, determine the vertex position of the outer surface. Express the outer surface as a parametric even-order aspherical surface equation, i.e.:

[0086]

[0087] Set the above coefficients as variables, and then use the lens optimization method to converge the beam of the longitudinal section to the focal plane as much as possible, optimize the spherical aberration of the system combination of the emitting lens and the light-transmitting shell to the minimum, that is, minimize the spot diameter of the image plane, and then determine the above even-order aspherical equation by corresponding to the above equal optical path condition.

[0088] 5) In non-sequential optical mode, the outer shell cross section determined above is rotated around the LiDAR axis according to the top rotation radius R and bottom rotation radius R0 of the inner surface of the light-transmitting outer shell, thereby forming a light-transmitting outer shell.

[0089] It should be noted that sequential mode refers to ideal geometric imaging, and the laser system uses sequential design mode to optimize the system. Non-sequential mode is more complex, and it can reflect imaging effects such as stray light and light splitting, which is closer to the actual situation.

[0090] In some embodiments, the defocus position of the LiDAR light source can make the absolute value of the difference between the first divergence angle and the second divergence angle less than a preset threshold; wherein, the first divergence angle is the divergence angle of the light beam emitted by the light source from the defocus position when the radar scanning angle is 0°, and the second divergence angle is the divergence angle of the light beam emitted by the light source from the defocus position when the radar scanning angle is 90°.

[0091] It should be noted that when the light source defocus position of the lidar is set in the aforementioned manner, the problem of beam divergence affecting beam transmission characteristics can be solved. The principle behind this solution will be explained below.

[0092] Because the optical axis of the emitting lens of a lidar is difficult to perfectly coincide with the rotating axis of the lidar, when the rotating mirror rotates to scan the collimated beam at different horizontal angles, the height of the center of the emitted beam will change with the scanning angle. The change is as follows: when the distance between the optical axis of the emitting lens and the rotating axis is x0 and it is in the xz plane, the height of the reflected beam center is the highest at a horizontal scanning angle of 0°. As the rotating mirror rotates and the scanning angle increases, the scanning angle gradually decreases. When the horizontal scanning angle is 180°, the beam center height is the lowest. After that, the beam center height increases with the increase of the scanning angle until it reaches the highest value at the starting position.

[0093] like Figure 6 and Figure 7 As shown, Figure 6 A schematic diagram showing the change in the center trajectory of the rotating scanning beam from the rotating mirror is shown. Figure 7 The diagram shows the vertical and horizontal projection cross-sections of the center beam at the scanning angle θ. Based on the spatial relationship between the reflected beam and the outer casing, its variation can be qualitatively analyzed in both the vertical and horizontal directions. Specifically, assuming the z-axis coordinate of the intersection of the rotating mirror and the rotation axis is z0, θ is the horizontal scanning angle, and the height of the reflected beam center is the z-axis coordinate of the intersection of the outgoing beam center and the mirror surface... M Then z M The relationship between z and the scanning angle θ is: M = z0 + x0cosθ. When the mirror rotates, the vertical position of the central beam changes with different scanning angles. When the beam is coplanar with the rotation axis, i.e., at 0° and 180° horizontal scanning angles, the central beam will not diverge when passing through the outer shell. It can be considered that when the angle δ between the beam and the horizontal projection plane of the inner surface normal is 0, the divergence of the central beam through the outer shell is minimal. The divergence angle σ of the central beam through the outer shell increases with increasing δ, with the maximum value of δ near the 90° horizontal scanning angle, where R... θ Let z be the vertical position of the beam passing through the center. M The radius of the circle where the horizontal cross section intersects the inner surface.

[0094] The divergence effect of the transparent outer shell on the emitted light beam can be considered as the transmission characteristic of the beam passing through a meniscus negative lens. The collimated beam can be considered as a beam parallel to the optical axis of the meniscus lens. The divergence angle after passing through the lens is related to the distance x0sinθ of the beam from the optical axis; the greater the distance, the larger the divergence angle. When θ is 0° and 180°, the divergence angle is 0. When the laser diode light source is at the focal plane of the emitting lens, i.e., when focused, as the horizontal scanning angle increases from 0°, the divergence angle also increases to its maximum value, and then gradually decreases until the horizontal scanning angle reaches 180°, at which point the divergence angle is zero again. When the scanning angle continues to increase from 180°, the divergence angle also increases to its maximum value, and then gradually decreases until the horizontal scanning angle reaches 360°, at which point the divergence angle is zero. This results in different beam divergence effects of the housing at different scanning angles. The housing has the least influence near 0° and 180°, resulting in better output beam characteristics, while the housing has the greatest influence near 90° and 270°, resulting in poorer output beam characteristics. This leads to significant differences in the output beam at different scanning angles, which is not suitable for practical applications.

[0095] To reduce the aforementioned differences, based on the diverging effect of a meniscus lens on the beam, the light source position can be moved forward towards the lens, causing the light source to defocus and produce a small-angle converging effect. This minimizes the influence of the casing near 0° and 180°, resulting in a small-angle convergence of the output beam. While the output beam characteristics are slightly worse than before, it improves the output beam characteristics near 90° and 270° because the converging effect of the output beam cancels out the diverging effect of the casing. For example... Figure 8 As shown, Figure 8A schematic diagram illustrating the effect of the light-transmitting shell on beam divergence at different scanning angles under focused and defocused conditions is shown. Figure 8 As can be seen, actual defocusing will also cause a small change in the relationship between the originally focused beam and the scanning angle, and the curve shape will change somewhat. Through qualitative analysis, it can be found that the defocus adjustment amount and the convergence angle of the emission angle are monotonic. Therefore, a defocus position can be found such that the emission convergence angle (-σ1) of the shell near 0° and 180° is equal to the emission divergence angle (σ1) of the shell near 90° and 270°.

[0096] Therefore, based on steps 1)-5) of the aforementioned method for manufacturing the light-transmitting housing, the defocus position of the light source can be determined through the following step 6), specifically as follows:

[0097] 6) Based on the relative positions of the radar system, a rotating reflector, the aforementioned transmitting lens, and a laser diode as the light source are introduced. A non-sequential optical simulation model is established. By changing the rotation direction of the reflector around the axis of rotation, the divergence angle σ at 0° and 90° scanning angles is simulated and calculated. x and σ y That is, the first divergence angle and the second divergence angle. Specifically, this divergence angle σ x and σ y The following calculations can be performed: Place the detector at distances L1 and L2 respectively, then simulate to obtain the corresponding spot sizes x1, y1 and x2, y2, and finally calculate... and σ can then be obtained x and σ y .

[0098] In some embodiments, the defocus position of the light source that makes the absolute value of the difference between the first divergence angle and the second divergence angle less than a preset threshold can be determined by the following method: first, a defocus initial position of the light source is given, then the light source is moved forward by Δz, and σ is calculated by simulation. x and σ y And compare σ x and σ y The size of σ, at this time, if σ x <σ y Then move the light source forward by Δz / 2, if σ x >σ y If so, the light source is moved back by Δz / 2. Then, the comparison of σ continues. x and σ y The size, if σ x <σ y Then move the light source forward by Δz / 4, if σ x >σ yIf the distance is halved after each comparison, the light source is moved back by Δz / 4. This process is repeated iteratively until σ is reached. x and σ y When the difference is less than the preset value ε, the final defocus position of the light source is set. Thus, by using the above-described defocusing method, the divergence effect of the light-transmitting shell on beams emitted from different angles can be balanced, thereby solving the problem of beam divergence affecting beam transmission characteristics and improving the overall performance of the lidar. Furthermore, this defocusing method does not alter the optical components, offering the advantages of simplicity and ease of implementation.

[0099] The following provides a specific implementation scheme.

[0100] The transparent shell is made of PC polycarbonate plastic. A 905nm laser is selected for operation, with a corresponding refractive index n of 1.569. The top rotation radius R of the inner surface of the transparent shell is 37mm, and the bottom rotation radius R0 is 25mm. The aperture A corresponding to 0° and the light-transmitting area of ​​the transparent shell is... p =23mm. Using conventional lens optimization methods, the spherical aberration of the emitting lens is minimized. The dot plot shows that the RMS radius of the image spot is 0.275μm and the geometric radius is 0.387μm, which is smaller than the Airy radius of 0.852μm. Figure 9a As shown.

[0101] The optimized lens is a plano-convex aspherical lens with a center thickness of 5mm. The rear surface is flat, and the front surface is an even-order aspherical surface with the following parameters:

[0102] r = 16.988 mm;

[0103] k = -1;

[0104] a4 = 1.071 × 10 -5 mm -3 ;

[0105] a6 = 4.609 × 10 -9 mm -5 ;

[0106] a8 = 1.116 × 10 -12 mm -7 ;

[0107] a 10 = -5.408 × 10 -15 mm -9 .

[0108] Set the focal length f to 16mm, and the inner surface of the parabola as the vertex with the radius of curvature r. pA conical surface with a diameter of 32mm and a conicity coefficient k = -1 is used. A light-transmitting shell with a refractive index n = 1.569 is introduced at a distance of 33.56mm from the vertex of the front surface of the emitting lens. The distance from the top vertex of the inner surface of the shell to the front surface of the emitting lens is 33.56mm, and the thickness d of the top of the shell is 2.5mm. A 23mm × 0.4mm rectangular aperture is used to obtain the longitudinal cross-section of the light rays for spherical aberration optimization. After optimization, the RMS radius of the image plane spot is 0.080μm, and the geometric radius is 0.253μm, which is smaller than the Airy radius of 0.863μm. Figure 9b As shown. The optimized optical path difference of rays at different cross-sectional heights is within 0.025 wavenumbers, satisfying the equal optical path requirement of the aforementioned formula (2), as shown. Figure 9c As shown.

[0109] Next, based on the shell parameters of the sequential mode, a simulation model of the non-sequential mode is established. An extinction groove structure is set at a preset position to allow stray light reflected from the inner surface of the shell to enter the extinction groove, suppressing stray light transmission and reducing its interference with the signal, as described above. Figure 5 The circular groove shown.

[0110] The simulated light source mimics a laser diode with three emitting regions. When focused, i.e., the emitting surface of the laser diode is at the focal plane of the emitting lens, the laser beam is collimated by the emitting lens and then emitted through the aforementioned casing. The simulated beam shapes at a distance of 10m from the radar are shown for horizontal scanning angles of 0°, 45°, 90°, and 135°. Figure 10a As shown in the figure. Simulation results show that the collimation effect of the light spot at a horizontal scanning angle of 0° is the best. Because the light-transmitting shell has the least effect on beam divergence in this exit angle region, three clearly visible luminous areas are observed. The collimation effect of the light spot at a horizontal scanning angle of 90° is the worst. Because the light-transmitting shell has the greatest effect on beam divergence in this exit angle region, the three luminous areas are indistinguishable due to angular divergence. The light spot emission characteristics at horizontal scanning angles of 45° and 135° are similar, with the luminous areas of the light spot slightly widened due to angular divergence. The effect of the light-transmitting shell on beam divergence in this exit angle region is between that of the 0° and 90° horizontal scanning angles. It can be seen that the above beam characteristics change with the scanning angle in accordance with the previous analysis, and this demonstrates that the divergence angle σ of the light passing through the shell mainly affects the beam.

[0111] By defocusing the light source and moving it forward by 0.02mm using the above method, the light spot shape at a distance of 10m from the radar was simulated again at horizontal scanning angles of 0°, 45°, 90°, and 135°. Figure 10b As shown. After defocusing, three clear and distinct light-emitting zones are observed at various scanning angles of 0°, 45°, 90°, and 135°. The defocusing method can evenly adjust the divergence effect of the light-transmitting shell on different scanning angles, which is consistent with the previous analysis.

[0112] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0113] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. 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 of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A lidar, characterized in that, The laser radar's light source defocus position ensures that the absolute value of the difference between the first divergence angle and the second divergence angle is less than a preset threshold; wherein, the first divergence angle is the divergence angle of the light beam emitted by the light source from the defocus position when the radar scanning angle is 0°, and the second divergence angle is the divergence angle of the light beam emitted by the light source from the defocus position when the radar scanning angle is 90°. The light-transmitting outer shell of the lidar has a rotationally symmetrical structure about the axis of rotation of the lidar, and the inner surface of the light-transmitting outer shell is parabolic in shape, and the inner surface is parabolic in the cross-sectional plane passing through the axis of rotation; The light-transmitting shell also includes an extinction structure, which is disposed in a preset area on the top of the light-transmitting shell. The preset area allows light beams reflected from the inner surface and converging at the focal point of the parabolic shape to enter the extinction structure.

2. The lidar according to claim 1, characterized in that, The equation for the parabolic shape is: ； Wherein, the z-axis of the coordinate system used in the equation is parallel to the rotation axis, and the plane containing the x-axis and y-axis of the coordinate system is parallel to the radar scanning plane; f is the focal length of the parabolic shape, R is the top rotation radius of the inner surface, and R0 is the bottom rotation radius of the inner surface.

3. The lidar according to claim 2, characterized in that, The parabolic shape is a conical surface, the vertex radius of curvature of the conical surface is 2f, and the conic coefficient of the conical surface is -1.

4. The lidar according to claim 2, characterized in that, The origin of the coordinate system is the focus of the parabola, the z-axis of the coordinate system coincides with the rotation axis, the x-axis of the coordinate system corresponds to 0° of the radar scanning plane, and the y-axis of the coordinate system corresponds to 90° of the radar scanning plane.

5. The lidar according to claim 1, characterized in that, The extinction structure is a groove structure.

6. The lidar according to claim 5, characterized in that, The groove structure is either a circular groove or a polygonal groove.

7. The lidar according to claim 1, characterized in that, The surface of the matting structure is covered with a matting material.

8. The lidar according to claim 1, characterized in that, The material of the light-transmitting outer shell is polycarbonate.

9. The lidar according to any one of claims 1-8, characterized in that, The lidar is a single-line lidar.

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