CN115656967A - Laser radar's printing opacity shell and laser radar - Google Patents
Laser radar's printing opacity shell and laser radar Download PDFInfo
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Abstract
The invention provides a light-transmitting shell of a laser radar and the laser radar, wherein the light-transmitting shell has a rotational symmetry structure relative to a rotating shaft of the laser radar, the inner surface of the light-transmitting shell is in a parabolic shape, and the inner surface of the light-transmitting shell is in a parabolic shape on a section plane passing through the rotating shaft; the outer surface of the light-transmitting shell is in an even-order aspheric surface shape corresponding to the paraboloid shape on a section plane passing through the rotating shaft, the z axis of a coordinate system adopted by an equation of the even-order aspheric surface shape is parallel to the rotating shaft, the planes of the x axis and the y axis of the coordinate system are parallel to a radar scanning plane, and the even-order aspheric surface shape can enable light beams emitted at any height parallel to the x axis in an xz section plane passing through the rotating shaft to be emitted in parallel to the x axis. The defocusing position of the light source of the laser radar enables the absolute value of the difference value between the first divergence angle and the second divergence angle to be smaller than a preset threshold value. The invention can solve the problem that the deflection and the divergence of the light beam influence the transmission characteristic of the light beam, and improves the overall performance of the laser radar.
Description
Technical Field
The invention relates to the technical field of laser radars, in particular to a light-transmitting shell of a laser radar and the laser radar.
Background
Lidar is a radar system that detects objects by emitting a laser beam. The light-transmitting shell is an important part of the laser radar, and plays an important role in supporting and protecting the laser radar and in improving the performance and reliability of the whole laser radar.
At present, laser radar's printing opacity shell has certain thickness usually, because the refracting index of printing opacity shell material is different with the refracting index of air, behind the light beam of transmission through the printing opacity shell, the printing opacity shell can be refracted and make the light beam take place to deflect and diverge, and deflect and diverge and can influence light beam transmission characteristic, and then reduced laser radar's complete machine performance.
Disclosure of Invention
The embodiment of the invention provides a light-transmitting shell of a laser radar and the laser radar, and aims to solve the problem that beam deflection and divergence caused by refraction of the light-transmitting shell influence the beam transmission characteristics of the laser radar.
In a first aspect, an embodiment of the present invention provides a light-transmitting casing of a laser radar, where the light-transmitting casing is in a rotationally symmetric structure with respect to a rotation axis of the laser radar, an inner surface of the light-transmitting casing is in a parabolic shape, and the inner surface is in a parabolic shape on a section plane passing through the rotation axis;
the outer surface of the light-transmitting shell is in an even-order aspheric surface shape corresponding to the paraboloid shape on a section plane passing through the rotating shaft, the z axis of a coordinate system adopted by an equation of the even-order aspheric surface shape is parallel to the rotating shaft, the planes of the x axis and the y axis of the coordinate system are parallel to a radar scanning plane, and the even-order aspheric surface shape can enable light beams emitted at any height parallel to the x axis in an xz section plane passing through the rotating shaft to be emitted in parallel to the x axis.
In one possible implementation, the equation of the paraboloid shape is:
wherein f is the focal length of the paraboloid, R is the top radius of rotation of the inner surface, R 0 A bottom radius of rotation of the inner surface;
the equation for even aspheric is:
wherein i is a positive integer greater than 2, z s Axial coordinate of even-order aspherical shape, h s Radial coordinate of even-order aspherical shape, r s Is the apex radius of curvature, k, of the even-order aspherical surface s Conic coefficient of even-order aspherical shape, a 4 、…、a 2i Are aspheric coefficients of each order.
In one possible implementation, the equation for even aspheric shapes satisfies the following condition:
N P ×I P ＝n(N P ×O P )；
wherein P is the intersection point of the light beam emitted from any height parallel to the x axis and the inner surface, and the coordinate of the point P is (x) P ，0，z P ) (ii) a Q is the intersection point of the light beam emitted from any height parallel to the x axis and the outer surface after being refracted and transmitted by the inner surface, and the coordinate of the Q point is (x) Q ，0，z Q ) (ii) a n is a light-transmitting shellD is the thickness of the light-transmitting envelope in the x-axis direction,
is the distance from point P to point Q, NP is the normal vector corresponding to point P, I P For incident vector of P point, O P And the emergent vector corresponding to the P point is shown.
In one possible implementation, the paraboloid is a conical surface, the vertex curvature radius of the conical surface is 2f, and the conical coefficient of the conical surface is-1.
In a possible implementation manner, the light-transmitting housing further includes an extinction structure, and the extinction structure is disposed in a preset area at the top of the light-transmitting housing, and the preset area enables the light beam reflected by the inner surface and converged at the focus of the paraboloid to enter the extinction structure.
In one possible implementation, the light extinction structure is a groove structure.
In one possible realization, the groove structure is a circular groove or a polygonal groove.
In one possible implementation, the surface of the matting structure is covered with a matting material.
In a second aspect, an embodiment of the present invention provides a lidar comprising a light-transmissive envelope as set forth in the first aspect or any one of the possible implementations of the first aspect.
In a possible implementation manner, the defocusing position of the light source of the laser radar can enable the absolute value of the difference value between the first divergence angle and the second divergence angle to be smaller than a preset threshold value; wherein the first divergence angle is a divergence angle of the light beam emitted from the light source out-of-focus position by the light source when the radar scanning angle is 0 °, and the second divergence angle is a divergence angle of the light beam emitted from the light source out-of-focus position by the light source when the radar scanning angle is 90 °.
The embodiment of the invention provides a light-transmitting shell of a laser radar and the laser radar, and the light-transmitting shell with the even-order aspheric surface outer surface is adopted, so that the vertical deflection effect of the light-transmitting shell on light beam refraction can be eliminated, the problem that light beam deflection influences the light beam transmission characteristic is solved, the pointing accuracy of laser radar light beam detection is greatly improved, and the overall performance of the laser radar is improved. In addition, through light source out of focus mode, the absolute value of the difference of first divergent angle and second divergent angle is less than the light source out of focus position of predetermineeing the threshold value promptly, can realize the light-transmitting housing to the not equilibrium of the effect of diverging of the angle outgoing beam to solve the light beam and diverged the problem that influences light beam transmission characteristic, promoted laser radar's complete machine performance.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed for the embodiments or the prior art descriptions will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.
FIG. 1 is a schematic diagram of determining the shape of the outer surface of a light-transmissive envelope based on the principle of aplanatism provided by an embodiment of the invention;
FIG. 2 is a schematic diagram of optical sequence pattern optimization design of surface parameters of a light-transmissive envelope according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of stray light generated by reflection of the spherical inner surface when a light beam passes through the light-transmissive envelope according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of stray light generated by reflection from the parabolic inner surface when a light beam passes through the light-transmissive envelope being eliminated by the light-extinction structure according to the embodiment of the invention;
FIG. 5a is a schematic diagram of a groove structure and a converging point of reflected light according to an embodiment of the present invention;
FIG. 5b is a schematic diagram of a light extinction structure using a circular groove according to an embodiment of the present invention;
FIG. 6 is a schematic diagram illustrating the change of the central track of the scanning beam of the rotating mirror according to the embodiment of the present invention;
FIG. 7 is a schematic cross-sectional view of a vertical projection and a horizontal projection of a central beam at a scan angle θ according to an embodiment of the present invention;
FIG. 8 is a schematic diagram of the diverging effect of the light beam by the light-transmissive enclosure at different scan angles in the focused and defocused conditions provided by the embodiments of the present invention;
FIG. 9a is a schematic diagram of an optimized spot array for a 0 field of view emitter lens provided by an embodiment of the present invention;
FIG. 9b is a schematic diagram of a spot arrangement of 0 ° field of view vertical section light rays through an emitter lens and a light transmissive envelope provided by an embodiment of the present invention;
FIG. 9c is a schematic diagram of the relationship between the optical path difference and the relative aperture according to the embodiment of the present invention;
FIG. 10a is a schematic diagram of the shape of an emergent beam spot at different scanning angles under focusing conditions according to an embodiment of the present invention;
fig. 10b is a schematic diagram of the exit light spot shapes at different scanning angles under the defocus condition according to the embodiment of the present invention.
Detailed Description
In the following description, for purposes of explanation and not limitation, specific details are set forth, such as particular system structures, techniques, etc. in order to provide a thorough understanding of the embodiments of the invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well-known systems, devices, circuits, and methods are omitted so as not to obscure the description of the present invention with unnecessary detail.
To make the objects, technical solutions and advantages of the present invention more apparent, the following description will be made by way of specific embodiments with reference to the accompanying drawings.
As described in the related art, the light-transmitting housing of the conventional laser radar, such as the light-transmitting housing of the single-line laser radar, generally has a certain thickness, because the refractive index of the material of the light-transmitting housing is different from that of the air, when the transmitted light beam passes through the light-transmitting housing, the light-transmitting housing can refract the light beam to deflect and disperse the light beam, and the deflection and the dispersion can affect the transmission characteristic of the light beam, thereby reducing the overall performance of the laser radar, such as the detection angle resolution, the detection pointing accuracy and the like of the laser radar.
In order to solve the problems in the prior art, the embodiment of the invention provides a light-transmitting shell of a laser radar and the laser radar. The following first describes a light-transmitting housing of a lidar according to an embodiment of the present invention.
The embodiment of the invention provides a light-transmitting shell of a laser radar, which is in a rotational symmetry structure relative to a rotating shaft of the laser radar, the inner surface of the light-transmitting shell is in a parabolic shape, and the inner surface of the light-transmitting shell is in a parabolic shape on a section plane passing through the rotating shaft. The outer surface of the light-transmitting shell is in an even-order aspheric surface shape corresponding to the paraboloid shape on a section plane passing through the rotating shaft, the z axis of a coordinate system adopted by an equation of the even-order aspheric surface shape is parallel to the rotating shaft, the planes of the x axis and the y axis of the coordinate system are parallel to a radar scanning plane, and the even-order aspheric surface shape can enable light beams emitted at any height parallel to the x axis in an xz section plane passing through the rotating shaft to be emitted in parallel to the x axis.
In the embodiment of the invention, the light-transmitting shell with the even-order aspheric surface-shaped outer surface is adopted, so that the vertical deflection effect of the light-transmitting shell on the light beam refraction can be eliminated, the problem that the light beam deflection influences the light beam transmission characteristic is solved, the pointing accuracy of laser radar light beam detection is greatly improved, and the overall performance of the laser radar is improved.
In some embodiments, the parabolic equation may employ the following equation:
wherein f is the focal length of the paraboloid, R is the top radius of rotation of the inner surface, R 0 A bottom radius of rotation of the inner surface;
accordingly, the equation for the even aspheric shape corresponding to the paraboloid shape may employ the following equation:
wherein i is a positive integer greater than 2, z s Is even asphericAxial coordinate, h s Is the radial coordinate of an even aspheric surface, r s Is the apex radius of curvature, k, of the even-order aspherical surface s Conic coefficient of even-order aspherical shape, a 4 、…、a 2i Is an aspherical coefficient of each order, for example, when i is 5, the aspherical coefficient will be a 4 、a 6 、a 8 、a 10 。
A specific parabolic shape is provided below, which may be a conic surface whose vertex curvature radius may be 2f and conic coefficient may be-1.
In some embodiments, the specific parameters of the equation for even aspheric shapes may be determined according to the following conditions, namely:
N P ×I P ＝n(N P ×O P )；
wherein P is the intersection point of the light beam emitted from any height parallel to the x axis and the inner surface, and the coordinate of the point P is (x) P ，0，z P ) (ii) a Q is the intersection point of the outgoing light beam at any height parallel to the x axis and the outer surface after being refracted and transmitted by the inner surface, and the coordinate of the point Q is (x) Q ，0，z Q ) (ii) a n is the refractive index of the light-transmissive envelope, d is the thickness of the light-transmissive envelope in the x-axis direction,
is the distance from point P to point Q, NP is the normal vector corresponding to point P, I P For incident vector of P point, O P And is an emergent vector corresponding to the P point.
To facilitate understanding of the parabolic inner surface structure and the even-order aspheric outer surface structure of the light-transmissive envelope, the implementation principle thereof will be described below.
According to the principle of aplanatism and combining the paraboloid-shaped inner surface, the outer surface shape capable of eliminating the vertical deflection effect caused by the refraction of the light beam by the light-transmitting shell can be obtained. As shown in fig. 1, fig. 1 is a schematic diagram of determining the shape of the outer surface of the light-transmitting housing based on the principle of aplanatism, wherein a rotation axis of the laser radar coincides with a z-axis of a coordinate system, an xy-plane is parallel to a radar scanning plane, an x-axis corresponds to a 0 ° angle scanned by the radar, i.e. a right-ahead direction, a y-axis corresponds to a 90 ° angle scanned by the radar, an origin of the coordinate system is located at the same position as a focus of a parabolic shape, and as can be seen from the foregoing description, an equation of the parabolic shape is as follows:
referring to fig. 1 again, the light beam emitted from any height parallel to the x axis in the xz cross-section plane of the rotation axis intersects with the inner surface at point P, intersects with the outer surface at point Q through refraction and transmission of the inner surface, and then is emitted parallel to the x axis, that is, the original emission direction is kept unchanged. Suppose the P point coordinate is (x) P ，0，z P ) For the beam to achieve the above-mentioned transmission characteristics, the Q point coordinate (x) Q ，0，z Q ) Aplanatic conditions must be satisfied:
wherein the content of the first and second substances,
the distance from point P to point Q can be expressed as:
combining the law of refraction, the normal vector, the incident vector and the emergent vector corresponding to the P point can satisfy the following relations:
N P ×I P ＝n(N P ×O P ) (3)
simultaneous equations (2) and (3) can be solved by x P Coordinate (x) of point Q as a parameter Q ，0，z Q ) Thereby obtaining the surface shape of the outer surface of the shell. It should be noted that the above-mentioned definition relationship is not limited to the light-transmitting casing material with a constant refractive index, and the same holds true for the light-transmitting casing material with a graded refractive index, and when the light-transmitting casing material with a graded refractive index is adopted, the corresponding refractive index can be selected at the corresponding coordinate.
To further understand the parabolic inner surface structure and even aspheric outer surface structure of the light-transmissive envelope, a method of manufacturing the light-transmissive envelope is provided below.
1) Top radius of rotation R and bottom radius of rotation R of the inner surface of the light-transmitting envelope according to the refractive index n 0 And the relative positions of the rotating reflector, the emission lens and the light source, and establishing an optical sequence mode simulation model taking the optical axis of the emission lens as the main optical axis, as shown in fig. 2.
2) Removing the transparent shell or setting the refractive index of the transparent shell to be 1 according to the aperture A corresponding to the transparent area of the transparent shell of 0 DEG p And optimizing the spherical aberration of the transmitting lens to be minimum by adopting a conventional lens optimization method, namely, the diameter of a light spot on an image surface is minimum.
3) The parabolic inner surface of the focal length f is represented by a conic surface, and the vertex curvature radius is r p =2f, conic coefficient k = -1;
4) Introducing a light-transmitting shell with a refractive index n, determining the vertex position of the outer surface of the shell according to the thickness d of the top of the shell, and expressing the outer surface as an even-order aspheric surface equation with variable parameters, namely:
setting the coefficients as variables, then adopting a lens optimization method to enable light beams of the longitudinal section to converge to a focal plane as much as possible, optimizing the system spherical aberration of the combination of the transmitting lens and the light-transmitting shell to be minimum, namely, the light spot diameter of the image plane is minimum, and then corresponding to the aplanatic condition, thereby determining the even aspheric equation;
5) In the non-sequential optical mode, the determined cross section of the shell is determined according to the top rotating radius R and the bottom rotating radius R of the inner surface of the light-transmitting shell 0 The laser radar is rotated by a rotating shaft, so that a light-transmitting shell is formed.
It should be noted that the sequence mode refers to ideal geometric imaging, and the laser system adopts a sequence design mode, so that the system can be optimized. The non-sequence mode is complex, can embody the imaging effects of stray light, light splitting and the like, and is closer to the actual situation.
In some embodiments, the light-transmissive enclosure further comprises a light-extinction structure disposed at a predetermined region of the top of the light-transmissive enclosure, the predetermined region enabling light beams reflected by the inner surface and converging at a focus of the parabolic shape to enter the light-extinction structure. Thus, the light-transmitting shell with the paraboloid-shaped inner surface can eliminate stray light interference.
Specifically, the light-transmitting casing of the conventional lidar, such as the light-transmitting casing of the single line lidar, generally adopts a cylindrical, conical or spherical structure, however, since the refractive index of the material of the light-transmitting casing of the lidar is different from that of air, when the emitted light beam passes through the inner surface of the light-transmitting casing, the inner surface of the light-transmitting casing reflects the light beam to generate stray light. The stray light can affect the transmission characteristics of light beams, and further the overall performance of the laser radar is reduced, such as the detection angle resolution, the detection precision and the like of the laser radar.
Taking a laser radar adopting a light-transmitting shell with a spherical structure as an example, as shown in fig. 3, a schematic diagram of stray light generated by reflection of a spherical inner surface when a light beam passes through the light-transmitting shell is shown, in fig. 3, a laser diode of the laser radar is used as a light source to emit a light beam from a, and the light beam is reflected to the inner surface of the light-transmitting shell through a rotating reflector of the laser radar.
In addition, the inner surface of the cylindrical, conical or spherical surface shape often has aberration, such as spherical aberration of the spherical inner surface, so that stray light generated by reflecting light beams by the inner surface is converged at different points of a focal plane to form a stray light region with a large range, and the stray light is further subjected to diffuse reflection or mirror reflection after passing through the stray light region, thereby further enhancing the stray light interference degree.
In the embodiment of the invention, because the paraboloid can converge the reflected light beam at the focus of the paraboloid, stray light generated by the reflection of the inner surface of the light-transmitting shell can be converged at the focus of the paraboloid by adopting the light-transmitting shell with the paraboloid inner surface, and the stray light converged at the focus of the paraboloid and reflected by the inner surface can be eliminated by the extinction structure arranged in the preset area at the top of the light-transmitting shell, so that stray light interference is eliminated, the problem that the stray light influences the light beam transmission characteristic is solved, and the overall performance of the laser radar is improved. As shown in fig. 4, a schematic diagram of stray light generated by reflection from the parabolic inner surface when a light beam passes through the light-transmitting envelope is eliminated by the light-extinction structure.
In addition, compared with the inner surface with the shape of a column, a cone or a sphere, the inner surface with the shape of a paraboloid can converge stray light generated by reflection of the inner surface at the focus of the shape of a paraboloid instead of the focus plane with the shape of a column, a cone or a sphere, and the stray light converged at the focus of the shape of a paraboloid is easier to eliminate, so that the difficulty in eliminating the stray light can be reduced, the stray light eliminating effect can be improved, and the overall performance of the laser radar can be greatly improved.
In some embodiments, the light-extinction structure may be a groove structure, such as a circular groove or a polygonal groove, or a planar structure covered with a light-extinction material, which may be a material capable of absorbing a laser beam.
For the mutual position of the groove structures and the reflected light, as shown in fig. 5a, which shows a schematic view of various groove structures and converging points of the reflected light, it may be provided that the converging point F of the reflected light is above, in or below the entrance plane of the groove structures, as long as it is ensured that the reflected light beams of the solid angle Ω are all transmitted into the extinction structure. In addition, the inner wall of the groove structure can be a straight wall, so that the processing and the assembly are facilitated. In order to better eliminate the signal of stray light secondary reflection, the inner wall with the section being in a trapezoid shape or a curved surface shape which is inclined inwards can be adopted in the groove structure.
As shown in fig. 5b, a schematic diagram of a light extinction structure using a circular groove is provided, and as can be seen from fig. 5b, the circular groove 51 is provided at a predetermined region of the top center region of the light-transmissive envelope, which allows stray light 52 generated by reflection from the inner surface of the light-transmissive envelope to enter the circular groove 51 and be eliminated.
In some embodiments, the surface of the groove structure can be covered with a light extinction material to better eliminate stray light.
It should be understood that, the sequence numbers of the steps in the foregoing embodiments do not imply an execution sequence, and the execution sequence of each process should be determined by functions and internal logic of the process, and should not limit the implementation process of the embodiments of the present invention in any way.
The embodiment of the invention also provides a laser radar which adopts the light-transmitting shell.
In some embodiments, the defocusing position of the light source of the laser radar can enable the absolute value of the difference value between the first divergence angle and the second divergence angle to be smaller than a preset threshold value; wherein the first divergence angle is a divergence angle of the light beam emitted from the light source out-of-focus position by the light source when the radar scanning angle is 0 °, and the second divergence angle is a divergence angle of the light beam emitted from the light source out-of-focus position by the light source when the radar scanning angle is 90 °.
It should be noted that when the defocus position of the light source of the laser radar is set in the foregoing manner, the problem that the beam divergence affects the transmission characteristics of the light beam can be solved, and the solution principle thereof will be described below.
Because the optical axis of laser radar's transmitting lens is difficult to coincide completely with laser radar's pivot, consequently, rotate when rotatory speculum and make the collimated light beam of reflection scan on different horizontal angles, the height at emergent beam center can change along with scanning angle, and its situation of change is: when the distance between the optical axis of the emitting lens and the rotating shaft is x 0 And when the horizontal scanning angle is 180 degrees, the central height of the light beam is lowest, and then the central height of the light beam increases along with the increase of the scanning angle until the highest value of the initial position.
As shown in fig. 6 and 7, fig. 6 is a schematic diagram showing the change of the central locus of the scanning beam by the rotation of the rotary mirror. Fig. 7 shows a schematic vertical projection and horizontal projection cross-sectional view of the light beam at the center of the scan angle θ. According to the spatial relationship between the reflected light beam and the shell, the variation relationship can be qualitatively analyzed in the vertical direction and the horizontal direction. Specifically, assume that the z-axis coordinate of the intersection of the rotating mirror and the rotation axis is z 0 Theta is the horizontal scanning angle, and the height of the center of the reflected beam is the z-axis coordinate z of the intersection of the center of the emergent beam and the reflector surface M Then z is M The variation relationship with the scanning angle theta is as follows: z is a radical of formula M ＝z 0 +x 0 cos θ. When the mirror is rotated, the vertical position of the central beam varies with different scanning angles, and when the beam is coplanar with the rotation axis, i.e. 0 ° and 180 ° horizontal scanning angles, the central beam does not diverge when passing through the housing, it can be considered that when the beam makes an angle δ of 0 with the horizontal projection plane of the inner surface normal, the divergence of the central beam through the housing is minimal, the divergence angle σ of the central beam through the housing increases with 6, and the maximum value of 6 is around 90 ° horizontal scanning angle, where R is the angle of 6 θ To pass through the vertical position z of the central beam M The horizontal cross-section of (a) intersects the inner surface.
The diverging effect of the light-transmitting envelope on the outgoing light beam can be regarded as the negative passage of the light beam through the meniscusThe transmission characteristic of the lens, collimated light beam can be regarded as light beam parallel to the optical axis of the meniscus lens, the divergence angle of the light beam after passing through the lens and the distance x of the light beam from the optical axis 0 sin θ, the larger the distance the larger the divergence angle. When θ is 0 ° and 180 °, the divergence angle is 0. Under the condition that the laser diode light source is positioned in the focal plane of the transmitting lens, namely under the condition of focusing, when the horizontal scanning angle of 0 degrees is increased, the divergence angle is also increased to the maximum value, then the divergence angle is gradually reduced until the horizontal scanning angle of 180 degrees, and the divergence angle is zero again; as the scan angle continues to increase from 180 deg., the divergence angle also increases to a maximum value and then gradually decreases again until 360 deg. horizontal scan angle, the divergence angle is zero. This makes the housing have different divergence effects on the beam at different scan angles, with the housing having the smallest effect near 0 ° and 180 ° and the output beam having better characteristics, and the housing having the largest effect near 90 ° and 270 ° and the output beam having poorer characteristics, making the difference between the output beams at different scan angles larger and not making use of practical applications.
In order to reduce the above difference, according to the diverging action of the meniscus lens on the light beam, the light source position can be moved forward to the lens direction to make the light source out of focus to generate a converging action of a small angle, so that the influence of the housing around 0 ° and 180 ° is minimized to make the output light beam converging at a small angle, and the output light beam characteristic is slightly worse than before, but the output light beam characteristic of the housing around 90 ° and 270 ° can be improved because the converging action of the output light beam is offset from the diverging action of the housing. As shown in FIG. 8, FIG. 8 shows a schematic diagram of the light-transmitting housing acting on the beam divergence under different scanning angles under focusing and defocusing conditions, as can be seen from FIG. 8, the actual defocusing also causes the original focused beam to change slightly with the relation of the scanning angle, the curve shape changes slightly, through qualitative analysis, it can be found that the defocusing adjustment amount and the convergence angle of the exit angle are monotonous, therefore, one defocusing position can be found so that the exit convergence angles (- σ) of the housing near 0 ° and 180 ° can be found 1 ) With the exit divergence angles (σ) of the envelope around 90 ° and 270 ° 1 ) Are equal in size.
On the basis of steps 1) -5) of the manufacturing method of the light-transmitting shell, the defocusing position of the light source can be determined through the following step 6), which specifically includes the following steps:
6) According to the relative relation of the radar complete machine, a rotating reflector, the transmitting lens and a light source laser diode are introduced, a non-sequence optical simulation model is established, and the divergence angle sigma of 0-degree scanning angle and 90-degree scanning angle is simulated and calculated by changing the rotating direction of the reflector around a rotating shaft x And σ y I.e. a first divergence angle and a second divergence angle. In particular, the divergence angle σ x And σ y Can be calculated by the following method: placing the detectors at a distance L, respectively 1 And L 2 Then simulating to obtain the corresponding spot size x 1 、y 1 And x 2 、y 2 And finally calculate
And
then sigma can be obtained x And σ y 。
In some embodiments, the light source defocus position at which the absolute value of the difference between the first divergence angle and the second divergence angle is smaller than the preset threshold value may be determined by: firstly, a light source defocusing initial position is given, then the light source is moved forward by delta z, and sigma is calculated through simulation x And σ y And comparing σ x And σ y In this case, if σ x ＜σ y The light source is shifted forward by Δ z/2 if σ x ＞σ y Then the light source is shifted back by Δ z/2. Thereafter, the comparison of σ is continued x And σ y If σ is large x ＜σ y The light source is shifted forward by Δ z/4 if σ x ＞σ y Then the light source is moved back by Δ z/4. Thus, the moving distance is halved after each comparison, and the iteration is repeated until the sigma is reached x And σ y The difference value of (d) is less than a preset value epsilon, and at this time, the final light source defocusing position setting is completed. Therefore, through the light source defocusing mode, different light-transmitting shell pairs can be realizedThe divergence effect of the angle outgoing light beam is balanced, so that the problem that the light beam divergence influences the transmission characteristic of the light beam is solved, and the overall performance of the laser radar is improved. In addition, the optical element is not changed in the defocusing mode of the light source, and the method has the advantages of simplicity and easiness in implementation.
A specific implementation is provided below.
The material of the light-transmitting shell is PC polycarbonate plastic, a 905nm working wavelength laser is selected, the corresponding refractive index n is 1.569, the top rotating radius R =37mm of the inner surface of the light-transmitting shell and the bottom rotating radius R0=25mm of the inner surface of the light-transmitting shell. Aperture A corresponding to the light transmission area of the light transmission shell at 0 degree p =23mm, the spherical aberration of the emission lens is optimized to be minimum by a conventional lens optimization method, and the image plane spot RMS radius is 0.275 μm, the geometric radius is 0.387 μm and is smaller than the Airy radius of 0.852 μm according to a dot sequence diagram, as shown in FIG. 9 a.
The optimized lens is a plano-convex aspheric lens, the center thickness of the lens is 5mm, the rear surface is a plane, and the front surface is an even aspheric surface with the following parameters:
r＝16.988mm；
k＝-1；
a 4 ＝1.071×10 -5 mm -3 ；
a 6 ＝4.609×10 -9 mm -5 ；
a 8 ＝1.116×10 -12 mm -7 ；
a 10 ＝-5.408×10 -15 mm -9 。
the focal length f is set to 16mm, and the vertex curvature radius of the parabolic inner surface is set to r p The light-transmitting shell with the refractive index n =1.569 is introduced at a position 33.56mm away from the vertex of the front surface of the emission lens, namely, the distance from the vertex of the top of the inner surface of the light-transmitting shell to the front surface of the emission lens is 33.56mm, the thickness d of the top of the shell is 2.5mm, a rectangular diaphragm with the size of 23mm multiplied by 0.4mm is arranged to obtain the light rays with the longitudinal section for carrying out spherical aberration optimization, the RMS radius of an image spot after optimization is 0.080 μm, the geometric radius is 0.253 μm and is smaller than the Airy radius 0.863 μm, as shown in FIG. 9 b.The optical path difference of the optimized light rays with different section heights is within 0.025 wave number, and the aplanatic requirement of the formula (2) is met, as shown in fig. 9 c.
Then, according to the housing parameters of the sequence mode, a simulation model of the non-sequence mode is established, and an extinction groove structure is set at a preset position to allow stray light reflected by the inner surface of the housing to enter the extinction groove, so that the transmission of the stray light is inhibited and the interference of the stray light on signals is reduced, for example, a circular groove shown in fig. 5.
The simulated light source simulates laser diodes in three light emitting areas, and under the condition of focusing, namely the light emitting surface of each laser diode is positioned at the focal plane of the emitting lens, laser is collimated by the emitting lens and then emitted through the shell, and the shapes of light spots at the positions of 10m away from the radar with the horizontal scanning angles of 0 degree, 45 degrees, 90 degrees and 135 degrees are simulated respectively, as shown in fig. 10 a. The simulation result shows that: the light spot emergent collimation effect at the horizontal scanning angle of 0 degree is the best, and as the light-transmitting shell has the minimum light beam dispersion effect in the emergent angle area, three visible light-emitting areas are presented; the light spot emitting collimation effect at the 90-degree horizontal scanning angle is the worst, and because the light-transmitting shell has the largest effect on the divergence of light beams in the emitting angle area, the three light-emitting areas cannot be distinguished due to angle divergence; the exit characteristics of the light spots at 45-degree and 135-degree horizontal scanning angles are similar, the light emitting areas of the light spots are slightly widened due to angle divergence, and the light beam divergence effect of the light-transmitting shell in the exit angle area is between the influences of 0-degree and 90-degree horizontal scanning angles. It can be seen that the above-described trend of the beam characteristics with scan angle is consistent with the previous analysis and illustrates the main effect of the divergence angle σ of the light rays through the housing on δ.
The light source is defocused by the above method, moved forward by 0.02mm, and the spot shapes at distances of 10m from the radar with horizontal scanning angles of 0 °, 45 °, 90 ° and 135 ° are simulated again, as shown in fig. 10 b. After the defocusing adjustment, clear and obvious three light emitting area structures are shown at the scanning angles of 0 degree, 45 degrees, 90 degrees and 135 degrees, and the defocusing mode can be used for uniformly adjusting the divergence effect of the light-transmitting shell on different scanning angles, and is consistent with the previous analysis.
In the above embodiments, the description of each embodiment has its own emphasis, and reference may be made to the related description of other embodiments for parts that are not described or recited in any embodiment.
The above-mentioned embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the same; although the present invention has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; such modifications and substitutions do not depart from the spirit and scope of the embodiments of the present invention, and they should be construed as being included therein.
Claims (10)
1. A light-transmitting housing for a lidar, the light-transmitting housing being rotationally symmetric about a rotational axis of the lidar, an inner surface of the light-transmitting housing being parabolic, the inner surface being parabolic in a cross-sectional plane through the rotational axis;
the outer surface of the light-transmitting shell is in an even-order aspheric surface shape corresponding to the paraboloid shape on a section plane passing through the rotating shaft, a z axis of a coordinate system adopted by an equation of the even-order aspheric surface shape is parallel to the rotating shaft, planes where an x axis and a y axis of the coordinate system are located are parallel to a radar scanning plane, and the even-order aspheric surface enables light beams which are emitted at any height and are parallel to the x axis in an xz section plane of the rotating shaft to be emitted in parallel to the x axis.
2. The lidar light-transmissive enclosure of claim 1, wherein the parabolic equation is:
wherein f is the focal length of the paraboloid, R is the top radius of rotation of the inner surface, and R 0 A bottom radius of rotation of the inner surface;
the equation for the even aspheric shape is:
wherein i is a positive integer greater than 2, z s Is the axial coordinate of the even aspheric surface, h s Is the radial coordinate of the even aspheric surface, r s Is the apex radius of curvature, k, of the even aspheric surface s Is the conic coefficient of the even-order aspherical shape, a 4 、…、a 2i Are aspheric coefficients of each order.
3. The light-transmissive envelope for a lidar of claim 2, wherein the equation for the even aspheric shape satisfies the following condition:
N p ×l p ＝n(N P ×O P )；
wherein P is the intersection point of the light beam emitted from any height parallel to the x axis and the inner surface, and the coordinate of the point P is (x) P ,0,z P ) (ii) a Q is the intersection point of the light beam emitted from any height parallel to the x axis and the outer surface after being refracted and transmitted by the inner surface, and the coordinate of the Q point is (x) Q ,0,z Q ) (ii) a n is a refractive index of the light-transmitting envelope, d is a thickness of the light-transmitting envelope in an x-axis direction,
distance from point P to point Q, N P Normal vector corresponding to P point, I P For incident vector of P point, O P And is an emergent vector corresponding to the P point.
4. The lidar light-transmissive enclosure of claim 2, wherein the parabolic surface is a conical surface having a vertex radius of curvature of 2f and a conic coefficient of-1.
5. The light-transmissive envelope of lidar of claim 1, further comprising an extinction structure disposed at a predetermined area of a top portion of the light-transmissive envelope, the predetermined area causing a beam reflected from the inner surface and converging at a focus of the parabolic shape to enter the extinction structure.
6. The lidar light-transmissive enclosure of claim 5, wherein the light-attenuating structure is a groove structure.
7. The light-transmissive envelope for lidar according to claim 6, wherein the groove structure is an annular groove or a polygonal groove.
8. The lidar light transmissive enclosure of claim 5, wherein a surface of the light attenuating structure is covered with a light attenuating material.
9. Lidar characterized by comprising a light-transmissive envelope according to any of claims 1 to 8.
10. The lidar of claim 9, wherein a defocus position of a light source of the lidar is such that an absolute value of a difference between the first divergence angle and the second divergence angle is less than a preset threshold; wherein the first divergence angle is a divergence angle of the light beam emitted from the light source out-of-focus position by the light source when the radar scanning angle is 0 °, and the second divergence angle is a divergence angle of the light beam emitted from the light source out-of-focus position by the light source when the radar scanning angle is 90 °.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202211261827.9A CN115656967A (en) | 2022-10-14 | 2022-10-14 | Laser radar's printing opacity shell and laser radar |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202211261827.9A CN115656967A (en) | 2022-10-14 | 2022-10-14 | Laser radar's printing opacity shell and laser radar |
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| CN202211261827.9A Pending CN115656967A (en) | 2022-10-14 | 2022-10-14 | Laser radar's printing opacity shell and laser radar |
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