Rotating Mirror Type Multi-Line LiDAR and Its Design Method

Abstract

The present invention provides a rotating mirror type multi-line lidar and its design method. The design method includes: driving the size of the reflecting mirror, the constraint conditions of the light source position and the field of view according to the field of view and the light source width; determining the constraint conditions of the width of the light-transmitting housing and the position coordinates of the edge points; determining the minimum space height of the emission optical path according to the pitch angle range of the lidar; determining the receiving aperture and the size of the reflecting mirror; optimizing the arrangement of the position of the receiving lens; selecting the structure of the light-transmitting housing and carrying out optimized design. The rotating mirror type multi-line lidar and its design method provided by the present invention can clarify the constraint relationship between the structural parameters among the components of the rotating mirror type multi-line lidar and the performance indicators of the rotating mirror type multi-line lidar, improve the system space utilization rate while ensuring the optimization of the performance indicators of the rotating mirror type multi-line lidar, and improve the compactness of the rotating mirror type multi-line lidar by optimizing the size and position parameters before each component.

Description

Technical Field

[0001] The present invention belongs to the technical field of laser radars, and in particular relates to a rotating mirror multi-line laser radar and a design method thereof. Background Art

[0002] As the autonomous driving industry grows and develops, LiDAR technology, an indispensable sensor component in this field, is also gradually maturing. For the rotating mirror multi-line LiDAR commonly used in the industry, it is necessary to have performance that meets the requirements of vehicle-mounted applications while also being more compact in structure and more reasonable in component layout in order to improve product reliability and reduce costs, thereby enhancing product competitiveness and making it suitable for matching more vehicle models.

[0003] Since the structural parameters and performance indicators of the rotating mirror multi-line laser radar influence and restrict each other, its performance improvement and structural compactness and miniaturization are often contradictory. Therefore, it is necessary to find the best compromise design solution between its structure and performance. How to achieve a balance between the performance improvement and structural compactness of the rotating mirror multi-line laser radar has become a key issue that needs to be urgently solved in the industry. Summary of the invention

[0004] The embodiment of the present invention provides a rotating mirror multi-line laser radar and a design method thereof, aiming to improve the performance of the rotating mirror multi-line laser radar while improving its structural compactness and space utilization.

[0005] To achieve the above-mentioned purpose, the technical solution adopted by the present invention is as follows: In the first aspect, a design method of a rotating mirror multi-line laser radar is provided, wherein the laser radar field of view of the rotating mirror multi-line laser radar includes a pan scanning field of view and a pitch scanning field of view, and the rotating mirror multi-line laser radar includes the following design steps:

[0006] According to the angular range requirements of the pan-tilt scanning field of view and the output aperture width of the light source, the size of the reflector, the position of the light source and the constraints between the pan-tilt scanning field of view are determined;

[0007] Determine the constraint conditions between the width of the light-transmitting shell and the edge position coordinates of the light-transmitting shell according to the position of the light source, the output aperture width of the light source, and the limit angle of the pan-tilt scanning field of view;

[0008] According to the angular range of the pitch scanning field of view, the output aperture width of the light source, and the maximum field angle of the pan scanning field of view, the minimum spatial height of the emission light path of the light source is determined;

[0009] Based on the principle of maximizing the receiving echo signal cross section and maximizing the space utilization, the aperture shape of the receiving lens is determined, and based on the maximum detection distance requirement of the system, the rotation radius of the reflector and the aperture size of the receiving lens are determined through the laser radar equation;

[0010] Establish a relationship diagram between the effective receiving aperture length of the receiving lens and the field of view of the lidar, and optimize the position of the receiving lens based on the relationship diagram;

[0011] Determine the shape of the light-transmitting housing according to the horizontal position and width of the light-transmitting housing.

[0012] Combined with the first aspect, in a possible implementation, based on the principles of maximizing the cross-section of the received echo signal and the highest space utilization rate, determine that the receiving aperture shape of the receiving lens is square; based on the system's maximum detection distance requirement, calculate the effective receiving area of the echo signal through the lidar equation, and determine the rotation radius of the mirror and the aperture size of the receiving lens through the effective receiving area of the echo signal.

[0013] In some embodiments, the method for optimizing the layout of the position of the receiving lens is: ensure the front angle of the rotating mirror type multi-line lidar, maximize the detection distance of the rotating mirror type multi-line lidar, and receive all signals within the specular reflection area of the mirror, and determine the optimal position of the receiving lens.

[0014] In some embodiments, the method for optimizing the layout of the position of the receiving lens is: maximize the integral of the effective receiving area of the echo signal within the entire field of view of the lidar field of view, and determine the optimal position of the receiving lens through the bisection method or the Newton iteration method.

[0015] In some embodiments, according to the horizontal position and width of the light-transmitting housing, the light-transmitting housing is selected as a planar structure. According to the vertical position of the light-transmitting housing and the angle of the lidar field of view, calculate the field of view angle range of the ghost image, as well as the incident angle range corresponding to the light-transmitting flat surface of the light-transmitting housing and the field of view angle range of the ghost image, and design an anti-reflection coating for the flat plate according to the incident angle range to eliminate the ghost image.

[0016] In some embodiments, according to the horizontal position and width of the light-transmitting housing, the light-transmitting housing is selected as a curved surface structure. Among them, the vertical cross-sections of the emission area and the receiving area of the light-transmitting housing with a curved surface structure are respectively composed of two parallelogram cross-sections with different inclination angles, and the included angle between the hypotenuses of the emission parallelogram cross-section and the receiving parallelogram cross-section is greater than the instantaneous receiving field of view angle.

[0017] Specifically, according to the direction vectors of the central rays of the emission optical path at different field of view angles, make a curve parametric equation perpendicular to the corresponding direction vectors, and scan the emission parallelogram cross-section and the receiving parallelogram cross-section along the trajectory of the curve parametric equation to obtain the light-transmitting housing with a curved surface structure.

[0018] The beneficial effects of the design method of the rotating mirror type multi-line lidar provided by the present invention are as follows: Compared with the prior art, the design method of the rotating mirror type multi-line lidar of the present invention can clarify the constraint relationship between the structural parameters of each component unit of the rotating mirror type multi-line lidar and the performance indicators of the rotating mirror type multi-line lidar. While ensuring the optimization of the performance indicators of the rotating mirror type multi-line lidar, it improves its space utilization rate, and by optimizing the size and position parameters between each component unit, it improves the compactness of the rotating mirror type multi-line lidar.

[0019] In a second aspect, an embodiment of the present invention further provides a rotating mirror type multi-line lidar, including a light-transmitting housing, a transmitting unit, a receiving unit, and a rotating scanning unit; wherein, a transmitting area and a receiving area are provided on the light-transmitting surface of the light-transmitting housing; the transmitting unit is arranged inside the light-transmitting housing and is provided with a light source for emitting laser signals, and the light source includes a plurality of light beams respectively emitting laser signals towards different pitching angles; the receiving unit is arranged inside the light-transmitting housing and is provided with a receiving lens for receiving echo signals; the rotating scanning unit is arranged inside the light-transmitting housing and has a horizontal rotation degree of freedom, and is provided with a reflecting mirror for reflecting the laser signal towards the transmitting area and for reflecting the echo signal returning to the receiving area to the receiving lens; the position constraint condition of the light source, the size constraint condition of the reflecting mirror, the center position and boundary constraint condition of the light-transmitting surface of the light-transmitting housing, and the size and position constraint condition of the receiving lens are all obtained by using the above-mentioned design method of the rotating mirror type multi-line lidar.

[0020] In combination with the second aspect, in a possible implementation manner, a horizontally arranged isolation component is provided inside the light-transmitting housing, and the isolation component is used for vertically separating the transmitting unit and the receiving unit and is horizontally aligned with the intersection position of the transmitting area and the receiving area; wherein, the upper edge of the receiving lens abuts against the bottom wall of the isolation component, and the lower edge of the receiving lens abuts against the inner bottom wall of the light-transmitting housing.

[0021] In some embodiments, the receiving lens has a rectangular effective receiving area, the length of the effective receiving area is in the vertical direction and is a preset value, and the width Y r (υ) is in the horizontal direction and satisfies the relationship:

[0022] Y r (υ) = min(yA(υ), yA′(υ), Ye1) - max(yB(υ), yB′(υ), Ye2);

[0023] In the formula, min represents the minimum value operation; max represents the maximum value operation;

[0024]

[0025]

[0026]

[0027] Among them, 2a is the length of the reflecting surface of the mirror, 2b is the distance between two parallel reflecting surfaces of the mirror, r is the distance from the edge point of the reflecting surface to the rotation center of the mirror, v is the field angle of the lidar field of view, and α is the angle between the reflecting surface and the horizontal plane, satisfying Ys is the vertical distance between the light source and the rotation center of the mirror, Yg is the vertical distance from the light-transmitting housing to the light source, Wg is the half-width of the light-transmitting housing, Xg is the horizontal distance between the center of the light-transmitting housing and the rotation center of the mirror, Ye1 is the maximum value of the projection height corresponding to the effective receiving area in the vertical direction, and Ye2 is the minimum value of the projection height corresponding to the effective receiving area in the vertical direction.

[0028] In some embodiments, the light-transmitting surface of the light-transmitting housing is a curved light-transmitting surface, and the curved light-transmitting surface is formed by scanning two parallelogram cross-sections along a space curve, and the included angle between the hypotenuses of the two parallelogram cross-sections is greater than the instantaneous scanning field angle;

[0029] Among them, the trajectory parametric equation F(x, y) of the space curve satisfies the relation:

[0030]

[0031] In the formula, ρ0 = |CG2| - [(2α2 + cotα2)Ys0 - b(cos2α2 - 2)cscα2], where |CG2| represents the distance between the boundary point of the light-transmitting surface of the light-transmitting housing and the intersection point of the emission light path of the light source and the reflecting surface of the mirror under the maximum field angle of the flat pendulum scanning field of view, α is the angle between the reflecting surface of the mirror and the horizontal plane, α2 represents the value of α corresponding to the maximum field angle, and Ys0 is the distance between the central light ray of the emission light path and the rotation center of the mirror.

[0032] In some possible implementation manners, the mirror is a multi-faceted mirror having at least two reflecting surfaces, and the angle between each mirror surface and the horizontal plane is an acute angle or a right angle or an obtuse angle; the detection method of the rotating mirror type multi-line lidar is single-shot multi-reception or multi-shot single-reception or multi-shot multi-reception, and the angles between adjacent beams of the rotating mirror type multi-line lidar are equal or unequal; both the transmitting unit and the receiving unit adopt linear array or planar array chips.

[0033] The beneficial effects of the rotary mirror type multi-line lidar provided by the present invention are as follows: Compared with the prior art, the rotary mirror type multi-line lidar of the present invention is designed, modeled and prepared based on the above-mentioned rotary mirror type multi-line lidar design method, and the optimal solutions of the dimensions and position parameters of each component unit are obtained from the constraint relationship between the structural parameters and performance indicators of the rotary mirror type multi-line lidar. Therefore, while improving the performance of the rotary mirror type multi-line lidar, its structural compactness and space utilization rate can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a design flow chart of the rotary mirror type multi-line lidar provided by an embodiment of the present invention;

[0035] Figure 2 It is a top view (a) and a front view (b) of the scanning and transmitting optical path of the rotary mirror type multi-line lidar provided by an embodiment of the present invention;

[0036] Figure 3 It is a relationship diagram between the light source position and the scanning field angle in an embodiment of the present invention;

[0037] Figure 4 It is a relationship diagram between the effective receiving aperture of the receiving lens and the field angle of the pendulum scanning field in an embodiment of the present invention;

[0038] Figure 5 It is a relationship diagram between the effective receiving aperture length of the receiving lens and the field angle of the lidar field in an embodiment of the present invention;

[0039] Figure 6 It is a schematic diagram of ghosting when using a light-transmitting outer shell with a planar structure in an embodiment of the present invention;

[0040] Figure 7 It is a schematic diagram of the modeling of the light-transmitting outer shell with a curved surface structure in an embodiment of the present invention;

[0041] Figure 8 It is a schematic diagram of eliminating ghosting of the light-transmitting outer shell with a curved surface structure in an embodiment of the present invention;

[0042] Figure 9 It is a schematic diagram of the cross-sectional scanning trajectory of the light-transmitting outer shell with a curved surface structure in an embodiment of the present invention;

[0043] Figure 10 It is a schematic diagram of the rotary mirror type 16-line lidar adopted in an embodiment of the present invention;

[0044] Figure 11 It is a relationship diagram between the maximum detection distance and the lidar field when the rotary mirror type 16-line lidar adopted in an embodiment of the present invention adopts two receiving lens arrangement methods respectively;

[0045] Figure 12The scanning trajectory curve diagram in the xoy plane of the curved outer shell cross-section of the rotating mirror type 16-line lidar adopted in the embodiment of the present invention at different vertical positions of the light-transmitting outer shell;

[0046] Figure 13 The internal structure schematic diagram of the rotating mirror type multi-line lidar (removing the transmitting area and receiving area of the light-transmitting outer shell) provided by the embodiment of the present invention;

[0047] Figure 14 The axonometric structure schematic diagram of the rotating mirror type multi-line lidar provided by the embodiment of the present invention.

[0048] In the figure: 10, light-transmitting outer shell; 11, transmitting area; 12, receiving area; 20, transmitting unit; 30, receiving unit; 31, receiving lens; 40, rotating scanning unit; 41, reflecting mirror; 50, isolation component. Detailed implementation manners

[0049] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0050] Now, the rotating mirror type multi-line lidar and its design method provided by the present invention will be described. Please refer to Figure 13 and Figure 14 , the rotating mirror type multi-line lidar includes a light-transmitting outer shell 10, and a transmitting unit 20, a receiving unit 30, and a rotating scanning unit 40 provided inside the light-transmitting outer shell 10; wherein, the light-transmitting surface of the light-transmitting outer shell 10 has a transmitting area 11 and a receiving area 12; the transmitting unit 20 is provided with a light source for emitting laser signals, and the light source includes a plurality of light beams that respectively emit laser signals at different pitch angles; the receiving unit 30 is provided with a receiving lens 31 for receiving echo signals; the rotating scanning unit 40 has a horizontal rotation degree of freedom and is provided with a reflecting mirror 41 for reflecting laser signals towards the transmitting area and for reflecting the echo signals returning to the receiving area to the receiving lens.

[0051] It should be noted that the main components of the transmitting unit 20 are the chip and the light source. The position of the light source and the width of the output aperture of the light source can affect the range of the lidar field of view. Therefore, a constraint relationship needs to be established with the lidar field of view. At the same time, the size of the mirror 41 is also a factor affecting the lidar field of view range. Therefore, a balanced constraint relationship also needs to be established between the mirror size and the lidar field of view; a balanced constraint relationship should be established between the shape and size of the receiving aperture of the receiving unit 30 (specifically referring to the receiving lens 31) and the maximum detection distance. The light-transmitting housing 10 specifically refers to a housing with a light-transmitting plane or a light-transmitting curved surface, and there are corresponding constraint relationships between the edge and the center position of the light-transmitting surface and the maximum detection distance.

[0052] In this embodiment, by reasonably establishing the constraint relationships among the positions, size parameters, and performance indicators of the various structural units of the rotating mirror multi-line lidar, the optimal solutions of the size and position parameters of each structural unit can be obtained, which can improve the performance of the rotating mirror multi-line lidar while enhancing its structural compactness and space utilization rate.

[0053] To avoid interference between the transmitting unit 20 and the receiving unit 30 and improve the optical isolation effect of light emission and reception of the rotating mirror multi-line lidar, in this embodiment, a horizontally arranged isolation component 50 is provided inside the light-transmitting housing 10. The isolation component 50 is used to separate the transmitting unit 20 and the receiving unit 30 vertically and is horizontally aligned with the intersection position of the transmitting area 11 and the receiving area 12; among them, the upper edge of the receiving lens 31 abuts against the bottom wall of the isolation component 50, and the lower edge of the receiving lens 31 abuts against the inner bottom wall of the light-transmitting housing 10.

[0054] Specifically, the receiving lens 31 has a rectangular effective receiving area. The length of the effective receiving area is in the vertical direction and is a preset value, and the width Y r (υ) is in the horizontal direction and satisfies the relationship:

[0055] Y r (υ) = min(yA(υ), yA′(υ), Ye1) - max(yB(υ), yB′(υ), Ye2);

[0056] In the formula, min represents the minimum value operation;

[0057] max represents the maximum value operation;

[0058]

[0059]

[0060]

[0061] Among them, 2a is the length of the reflecting surface of the mirror 41, 2b is the distance between two parallel reflecting surfaces of the mirror 41, r is the distance from the edge point of the reflecting surface to the rotation center of the mirror 41, v is the field angle of the lidar field of view, and α is the angle between the reflecting surface and the horizontal plane, satisfying Ys is the vertical distance between the light source and the rotation center of the mirror 41, Yg is the vertical distance from the light-transmitting surface of the light-transmitting housing 10 (hereinafter, all descriptions of the light-transmitting housing 10 refer to its light-transmitting surface) to the light source, Wg is the half-width of the light-transmitting housing 10, Xg is the horizontal distance between the center of the light-transmitting housing 10 and the rotation center of the mirror 41, Ye1 is the maximum value of the projection height corresponding to the effective receiving area in the vertical direction, and Ye2 is the minimum value of the projection height corresponding to the effective receiving area in the vertical direction.

[0062] The light-transmitting surface of the light-transmitting housing 10 is a curved light-transmitting surface, which is formed by scanning two parallelogram cross-sections along a space curve. The included angle between the hypotenuses of the two parallelogram cross-sections is greater than the instantaneous scanning field angle; among them, the trajectory parametric equation F(x, y) of the space curve satisfies the relational expression:

[0063]

[0064] In the formula, ρ0 = |CG2| - [(2α2 + cotα2)Ys0 - b(cos2α2 - 2)cscα2], where |CG2| represents the distance between the boundary point of the light-transmitting surface of the light-transmitting housing 10 and the intersection point of the emission optical path of the light source and the reflecting surface of the mirror 41 under the maximum field angle of the flat pendulum scanning field of view, α is the angle between the reflecting surface of the mirror 41 and the horizontal plane, α2 represents the value of α corresponding to the maximum field angle, and Ys0 is the distance between the central ray of the emission optical path and the rotation center of the mirror 41.

[0065] It should be noted that in this embodiment, the mirror used in the rotary mirror type multi-line lidar is a multi-faceted mirror with at least two reflecting surfaces, and the angle between each mirror surface and the horizontal plane is an acute angle or a right angle or an obtuse angle; the detection method of the rotary mirror type multi-line lidar is single-shot multi-receive or multi-shot single-receive or multi-shot multi-receive, and the included angles between adjacent beams of the rotary mirror type multi-line lidar are equal or unequal; the emission unit 20 and the receiving unit 30 of the rotary mirror type multi-line lidar both adopt linear array or area array chips.

[0066] It should be understood that the above-mentioned mirror can not only be a two-sided mirror, but also a three-sided rotating mirror, a four-sided rotating mirror, a six-sided rotating mirror or other rotating mirrors with multiple reflecting surfaces; each mirror surface of the above-mentioned mirror is not limited to being perpendicular to the horizontal plane, and can also be at an acute angle or an obtuse angle with the horizontal plane; for each beam detection of the above-mentioned rotating mirror type multi-line lidar, it is not limited to the corresponding detection method of single-shot and single-receive, and can also be realized by detection methods such as single-shot and multi-receive, multi-shot and single-receive or multi-shot and multi-receive for multi-line detection; the pitch angle range of the above-mentioned rotating mirror type multi-line lidar can be symmetric or asymmetric with respect to the horizontal plane, that is to say, the upward tilt angle of the above-mentioned rotating mirror type multi-line lidar and the downward tilt angle range can be equal or unequal; the angles between adjacent beams of the above-mentioned rotating mirror type multi-line lidar can be equal or unequal, and the whole can be in a state of uniform distribution or non-uniform distribution; the transmitting unit 20 of the above-mentioned rotating mirror type multi-line lidar can adopt a linear array light-emitting chip or a planar array light-emitting chip; the receiving unit 30 of the above-mentioned rotating mirror type multi-line lidar can adopt a linear array receiving detection chip or a planar array receiving detection chip; in addition, it should be emphasized that the above-mentioned rotating mirror type multi-line lidar can be applied to vehicles, such as in autonomous driving technology, and can also be used in the fields of security or transportation.

[0067] It should be noted that the position constraint conditions of the light source, the size constraint conditions of the mirror, the center position and boundary constraint conditions of the light-transmitting surface of the light-transmitting housing, and the size and position constraint conditions of the receiving lens of the rotating mirror type multi-line lidar provided in this embodiment are all obtained by using the design method of the rotating mirror type multi-line lidar provided in the following embodiments.

[0068] Please refer to Figures 1 to 9 , the lidar field of view of the rotating mirror type multi-line lidar includes a horizontal swing scanning field of view and a pitch scanning field of view, and its design method includes the following design steps:

[0069] S100, according to the angle range requirement of the horizontal swing scanning field of view and the output aperture width of the light source, determine the constraints between the size of the mirror, the position of the light source and the horizontal swing scanning field of view.

[0070] In this embodiment, as Figure 2 shown, two reflecting mirrors are used. Taking the rotation center of the mirror as the origin O, the fixed emission direction of the light source s is parallel to the x-axis, the vertical distance from the light source to the origin O is Ys, the distance between the two reflecting surfaces of the mirror is 2b, and the trajectories of two points A and B at the edge of the mirror surface are always on a circle with the origin O as the center and a radius of r when the mirror rotates. Among them, the coordinates of points A and B are:

[0071]

[0072]

[0073] The coordinates of the intersection point C of the emission optical path of the light source s and the AB reflecting surface are:

[0074]

[0075] The AB reflecting surface with a mirror length of 2a makes an angle α with the x-axis, the reflecting surface of the mirror is perpendicular to the horizontal plane, the collimated light beam emitted by the light source s is reflected by the AB surface at point C and exits through the light-transmitting housing G with a half-width of Wg at a flat-swing scanning field angle ν, the vertical distance from the light-transmitting housing to the light source is Yg, and the horizontal distance between the center of the light-transmitting housing and the origin O is Xg.

[0076] As Figure 3 shown, when considering an ideal light source with zero width and the vertical distance from the mirror being b, the maximum field angle ν2 of the flat-swing scanning field can reach π; when the vertical distance Ys between the light source and the origin O is greater than b and gradually increases, the maximum field angle ν2 gradually decreases along the curve track, after Ys gradually increases to a, the minimum field angle ν1 of the flat-swing scanning field also begins to be restricted and gradually increases along the curve track, and the field range ν2 - ν1 of the flat-swing scanning field gradually decreases. When Ys gradually increases to r, the two curves coincide as At this time, the field range of the flat-swing scanning field is 0, that is, the field of view of the lidar disappears; when the vertical distance Ys between the light source and the origin O is less than b and gradually decreases, the maximum field angle ν2 gradually decreases along the curve track, and when it decreases to 0, the maximum field angle ν2 is The minimum field angle is 0 and remains unchanged all the time.

[0077] Here, considering that the field of view of a rotating mirror type multi-line lidar is usually centered in the front, that is, ν = 90°, then the minimum field angle ν1m and the maximum field angle ν2m satisfy: ν1m + ν2m = π; in addition, considering that the actual light source has a certain width, assuming that the light source width (i.e., the output aperture width of the light source) is Ws = Ys2 - Ys1, from Figure 3 the field angle change curve, it can be seen that when the size of the scanning mirror is fixed, the smaller the light source width Ws, the easier it is to meet the field of view requirements. For the case where the ratio of the light source width Ws to the size of the mirror system a / b is fixed, the larger the size of the mirror, the easier it is to meet the field of view requirements. In order to minimize the structural volume and improve the space utilization rate, it is necessary to minimize the output aperture width Ws of the light source while maintaining sufficient energy output. After determining Ws, the constraint relationship between the mirror size and the light source position and the range of the flat-swing scanning field satisfies Equation 1:

[0078]

[0079] S200. Determine the constraint conditions between the width of the light-transmitting housing and the coordinate of the edge position of the light-transmitting housing according to the position of the light source, the output aperture width of the light source, and the limit angle of the pan scanning field of view.

[0080] In this embodiment, after determining the size of the mirror and the position of the light source through Relationship One, since the position and size of the light-transmitting housing will also affect the pan scanning field of view, combined with Figure 2 and Figure 3 , the horizontal position x G1 of the boundary point G1 on the left side of the light-transmitting housing (the light-transmitting surface, hereinafter all refer to the light-transmitting surface) or the half-width Wg of the light-transmitting housing is determined by the light ray with a vertical distance Ys1 from the light source and the minimum field of view angle ν1m, and the distance Ys1 + Yg1 between the light-transmitting housing and the origin O. The horizontal position x G2 of the boundary point G2 on the right side of the light-transmitting housing or the half-width Wg of the light-transmitting housing is determined by the light ray with a vertical distance Ys2 from the light source and the maximum field of view angle ν2m, and the distance Ys2 + Yg2 between the light-transmitting housing and the origin O. The emission beam can be output from the light-transmitting housing within the given field of view range as long as the constraint conditions satisfy the following Relationship Two:

[0081]

[0082] where Ysg = Ys1 + Yg1 = Ys2 + Yg2.

[0083] It can be seen from Relationship Two that the larger the field of view angle of the pan scanning field of view, the larger the required width of the light-transmitting housing. Under the same field of view conditions, the smaller the distance between the light-transmitting housing and the origin O, the smaller the required width of the light-transmitting housing, and the corresponding optical region is also smaller.

[0084] S300. Determine the minimum spatial height of the emission light path of the light source according to the angular range of the pitch scanning field of view, the output aperture width of the light source, and combined with the maximum field of view angle of the pan scanning field of view.

[0085] It should be understood that the rotating mirror type multi-line lidar scans and detects by rotating multiple light beam lines at different pitch angles in the horizontal direction, thereby forming the lidar field of view. In this embodiment, the angular range θ of the pitch scanning field of view is: -θ0 ≤ θ ≤ θ0. The minimum spatial height of the emission light path is H1. This height is the distance between the lower surface of the top cover of the rotating mirror type multi-line lidar and the upper surface of the isolation component between the emission unit and the receiving unit. This distance is determined by the longest transmission distance from the light source through the mirror to the light-transmitting housing among all scanning angles, that is, |SC| + |CT|. From Figure 2 it can be seen that this distance is the largest corresponding to the maximum field of view angle ν2m. And H1 satisfies the following constraint Relationship Three to ensure that the light paths of each light beam line are not blocked:

[0086]

[0087] S400. Based on the principles of maximizing the received echo signal cross-section and the highest space utilization rate, determine the aperture shape of the receiving lens. And based on the requirement of the maximum detection range of the system, determine the rotation radius of the mirror and the aperture size of the receiving lens through the lidar equation.

[0088] In this embodiment, the maximum detection range of the rotating mirror multi-line lidar is L m (a preset value according to the radar detection needs). According to the lidar equation, the relational expression four can be obtained:

[0089] where, P m is the minimum detectable received power of the system, P0 is the transmission power of the rotating mirror multi-line lidar, ρ is the reflectivity of the detection target, A r is the effective reception area of the echo signal, η r is the efficiency of the receiving lens, η e is the emission efficiency of the light source, and δ is the angle between the normal direction of the emitted beam and the normal direction of the target surface.

[0090] Since the transmission power P0 is exactly the same within the field of view of the lidar, the maximum detection range L m of different fields of view mainly depends on the effective reception area A r of the echo signal. For the field of view angle ν, its effective reception area is composed of the part where the cross-section of the echo signal in this direction is reflected by the mirror and projected onto the overlapping position of the detection plane and the aperture of the receiving lens. Therefore, the aperture shape of the receiving lens can be determined according to the change of the projection height of the echo signal cross-section in the height direction (i.e., the z-axis direction) of the rotating mirror multi-line lidar. It can be determined that the optimal solution of the aperture shape and size of the receiving lens can be obtained by fitting the path of the aperture edge with the projection height change curve.

[0091] S500. Establish a relationship diagram between the effective reception aperture length of the receiving lens and the lidar field of view, and optimize the layout position of the receiving lens based on the relationship diagram.

[0092] Figure 4 That is the relationship diagram between the effective reception aperture length of the receiving lens and the horizontal swing scanning field of view. From this, the relationship diagram between the effective reception aperture length and the lidar field of view as shown in Figure 5 can be made, so as to determine the effective reception area A r = Y r W r , where, W r = Ye1 - Ye2, is a fixed value, Y ris the vertical line length of the shaded part in the figure, which is a variable that changes with the field of view angle. On this basis, it is only necessary to ensure that Y r is as large as possible within the field of view of the lidar, and the optimal solution of the parameters and position of the receiving lens can be obtained.

[0093] S600. Determine the shape of the light-transmitting housing according to the horizontal position and width of the light-transmitting housing.

[0094] In this embodiment, after determining the size parameters and position of the light-transmitting housing, the specific shape of the light-transmitting housing can be selected based on the good protection effect on the rotating mirror type multi-line lidar. Specifically, a planar structure and a curved surface structure can be selected to improve the product reliability.

[0095] Compared with the prior art, the design method of the rotating mirror type multi-line lidar provided in this embodiment can clarify the constraint relationship between the structural parameters of each component unit of the rotating mirror type multi-line lidar and the performance indicators of the rotating mirror type multi-line lidar. While ensuring the optimization of the performance indicators of the rotating mirror type multi-line lidar, it improves its space utilization rate, and by optimizing the size and position parameters between each component unit, the compactness of the rotating mirror type multi-line lidar is improved.

[0096] In some embodiments, in combination with Figure 4 and Figure 5 , the specific implementation manner of the above step S400 is to determine that the receiving aperture shape of the receiving lens is square based on the principle of the largest received echo signal cross-section and the highest space utilization rate; based on the system's maximum detection distance requirement, calculate the effective receiving area of the echo signal through the lidar equation, and determine the rotation radius of the mirror and the aperture size of the receiving lens through the effective receiving area of the echo signal.

[0097] Since the transmit power P0 is completely the same within the field of view, the maximum detection distance L m at different field of view angles mainly depends on the effective receiving area A r of the echo signal. For the field of view angle ν, its effective receiving area is composed of the overlapping part of the projection of the echo signal cross-section in this direction reflected by the mirror on the detection plane and the aperture of the receiving lens. The projected height of the echo signal cross-section in the height direction of the rotating mirror type multi-line lidar, that is, W r always remains unchanged. Therefore, the aperture edge of the receiving lens should be a straight edge or close to a straight edge, that is, using a square hole as the optimal aperture shape of the receiving lens can meet the maximum efficiency of the receiving lens and does not increase the volume of the overall structure.

[0098] Such as Figure 5 , according to the echo cross-section projection relationship, the echo cross-section is rectangular, and the length of this rectangle remains unchanged in the height direction of the rotating mirror type multi-line lidar, which is a fixed value Wr = Ye1 - Ye2, and the width of the rectangle is the vertical line in the area enclosed by the curves yA(υ), yA′(υ), yB(υ), yB′(υ) and the straight lines Ye1, Ye2, that is, the variable Y r , where Ye1 is the maximum value of the projection height corresponding to the effective reception area on the y-axis (i.e., the highest point), and Ye2 is the minimum value of the projection height corresponding to the effective reception area on the y-axis (i.e., the lowest point). The following relationship five can be obtained:

[0099] Y r (υ) = min(yA(υ), yA′(υ), Ye1) - max(yB(υ), yB′(υ), Ye2)

[0100] where min represents the operation of taking the minimum value, and max represents the operation of taking the maximum value,

[0101]

[0102]

[0103]

[0104] From relationship five, Y r corresponding to the optimal solutions for different field-of-view angles ν can be determined, thereby obtaining the optimal solution of the effective reception area, and further determining the optimal solutions of the rotation radius of the mirror and the aperture size of the receiving lens.

[0105] One way to optimize the position arrangement of the receiving lens in the above step S500 is: ensuring the angle directly in front of the rotating mirror type multi-line lidar, maximizing the detection distance of the rotating mirror type multi-line lidar and receiving all signals within the specular reflection area of the mirror, and determining the optimal position of the receiving lens.

[0106] As Figure 5 shown, an optimized arrangement is adopted using a receiving lens with a square aperture, ensuring the angle directly in front of the lidar, that is, ν = 90°, maximizing the detection distance and being able to receive all signals within the specular reflection area of the mirror. The detection distance decreases towards both sides with the angle. The optimal positions (the edge positions on both sides) of the receiving lens obtained by satisfying the above conditions are:

[0107]

[0108] Another way to optimize the position arrangement of the receiving lens in the above step S500 is: maximizing the integral of the effective reception area of the echo signal within the entire field of view of the lidar field of view, and determining the optimal position of the receiving lens through the bisection method or the Newton iteration method.

[0109] Combined with Figure 5, the area of the region enclosed by the curves yA(υ), yA′(υ), yB(υ), yB′(υ) and the straight lines Ye1, Ye2 is the largest, that is, to ensure Y r and the integral within the lidar field of view is maximized. According to the monotonic and continuous variation relationships of each function, it can be known that the condition to meet the requirement of maximizing this integral is:

[0110] The distance between the connection lines of the intersection points yA(υa), yA′(υa′) of the ν-axis parallel line passing through Ye1 and the curves yA(υ), yA′(υ) respectively, is equal to the distance between the two intersection points yB(υb), yB(υb′) of the ν-axis parallel line passing through Ye2 and the curve yB(υ), or is equal to the distance between the connection lines of the intersection points yB(υb), yB′(υb′) of the ν-axis parallel line passing through Ye2 and the curves yB(υ), yB′(υ) respectively. Here, it should be understood that as the angle of the lidar field of view changes, the ν-axis parallel line passing through Ye2 may have two intersection points with the curve yB(υ), or may have one intersection point. In addition, as can be seen from the figure, yA(υa) = Ye1, yA′(υa′) = Ye1, yB(υb) = Ye2, yB(υb′) = Ye2, yB′(υb′) = Ye2. By determining the above conditions, the optimal solution can be obtained through the bisection method or the Newton iteration method.

[0111] It should be noted that the spatial height H2 of the receiving optical path, that is, the distance between the upper surface of the bottom cover of the rotating mirror type multi-line lidar (i.e., the bottom wall of the light-transmitting housing) and the lower surface of the isolation component between the transmitting unit and the receiving unit, is considered differently from the spatial height of the transmitting optical path. In order to achieve better isolation of the transmitting unit and the receiving unit, the receiving optical path is set in a form that closely matches the aperture of the receiving lens here, that is, the upper edge of the receiving lens is firmly attached to the lower surface of the isolation component, and the lower edge is firmly attached to the inner bottom wall of the light-transmitting housing, satisfying H2 = Wr.

[0112] For example, in the above step S600, according to the horizontal position and width of the light-transmitting housing, a planar structure is selected for the light-transmitting housing. According to the vertical position of the light-transmitting housing and the angle of the lidar field of view, the field of view angle range of the ghost image is calculated, as well as the incident angle range corresponding to the field of view angle range of the ghost image on the light-transmitting flat surface of the light-transmitting housing, and an anti-reflection film for the flat plate is designed according to the incident angle range to eliminate the ghost image.

[0113] It should be understood that the light-transmitting housing mainly considers minimizing the signal interference and ghost image problems caused by the reflection of its own optical path as much as possible, and minimizing the directivity influence on the transmitting optical path. Since the front and rear two refracting surfaces of the planar light-transmitting housing are parallel to each other, the spatial angle pointing of the detection scanning beam before passing through the planar light-transmitting housing is the same as the spatial angle pointing after passing through the light-transmitting housing. Therefore, it will not have an impact on the directivity of the transmitting optical path itself.

[0114] Due to the mirror reflection of the flat-panel structure of the transparent shell, if the target reflection signal is strong at certain angles, ghosting problems may occur: Figure 6 As shown by the solid arrow in the figure, the field angle ν of the horizontal scanning field is greater than In the case of Most of the light incident on the light-transmitting housing can be scanned and detected normally by the light-transmitting housing, while a small part of the light will be reflected by the light-transmitting housing to the reflector, and then reflected by the reflector will be emitted from the light-transmitting housing at another field of view angle ν′, such as Figure 6 As shown by the dotted arrow in , when a strong reflective object appears at the field angle ν′, its echo signal returns along the field angle ν′, is reflected by the reflector, is reflected by the transparent housing, and is finally reflected back to the receiving detector through the reflector. The system regards the object M′ detecting the field angle ν′ as the object M detecting the field angle ν, which is the ghost phenomenon, where ν=2α-π, ν′=4α-3π, ν′=2ν-π.

[0115] In order to analyze the ghost problem and optimization method caused by multiple reflections, the system light transmission path is modeled and analyzed in this embodiment. The coordinates of the intersection point T of the light of the field of view angle ν after being reflected by the reflector for the first time and the transparent housing are:

[0116] The coordinates of the intersection point F between the light reflected by the transparent shell and the mirror surface of the reflector are:

[0117]

[0118] The coordinates of the intersection point E of the light beam with the transparent shell after the light beam is reflected by the reflector for the second time are:

[0119]

[0120] Depend on Figure 6 From the light transmission path, it can be seen that for the system to produce ghost images, two conditions must be met at the same time: the light beam reflected by the transparent shell returns to the reflector, and the light beam reflected by the reflector for the second time is emitted from the transparent shell.

[0121] Among them, the coordinates satisfy the relationship formula 6:

[0122]

[0123] From equation 6, we can see that when the field of view angle ν is greater than In the case of tanα+tan 2α<0,x F >0, the smaller Ysg is, the easier it is to satisfy x F ≤x B, that is to say, the closer the light-transmitting housing is to the reflector, the larger the field of view range where ghost images are generated; the wider and more left-offset the light-transmitting housing is, that is, the larger Wg + Xg is, the easier it is to satisfy x E ≤x G1 , and the larger the field of view range where ghost images are generated.

[0124] The field of view range ν g1 ~ν g2 where ghost images are generated can be calculated through Equation 6. In this embodiment, an anti-reflection film is coated on the surface of the light-transmitting housing to eliminate the influence of ghost images. It should be noted that the anti-reflection film is designed for anti-reflection according to the incident angle .

[0125] Exemplarily, according to the horizontal position and width of the light-transmitting housing, the light-transmitting housing is selected to be of a curved surface structure. Among them, the vertical cross-sections of the emission area and the reception area of the light-transmitting housing with a curved surface structure are respectively composed of two parallelogram cross-sections with different inclination angles, and the included angle between the hypotenuses of the emission parallelogram cross-section and the reception parallelogram cross-section is greater than the instantaneous reception field of view angle.

[0126] Specifically, according to the direction vectors of the central light ray of the emission optical path at different field of view angles, the curve parametric equations perpendicular to the corresponding direction vectors are made, and the emission parallelogram cross-section and the reception parallelogram cross-section are scanned along the trajectory of the curve parametric equations to obtain the light-transmitting housing with a curved surface structure.

[0127] It should be understood that for the light-transmitting housing with a curved surface structure, it is also necessary to minimize the signal interference and ghost image problems caused by its own reflection of the optical path as much as possible, and minimize the influence on the directivity of the emission optical path.

[0128] Here, aiming at the directivity and ghost image problems of the emission optical path, this embodiment proposes a method for obtaining a light-transmitting housing with a curved surface structure: Please refer to Figure 7, the light-transmitting housing corresponding to the transmitting area is formed by scanning the cross-section of parallelogram GaGbGcGd along the trajectory of the curve parametric equation F(x, y), and the starting points of the trajectory of the curve parametric equation F(x, y) respectively correspond to the boundary points G1 and G2 of the light-transmitting housing; the light-transmitting housing corresponding to the receiving area is formed by scanning the cross-section of parallelogram GcGdGeGf along the trajectory of the curve F(x, y), and the starting points of the trajectory of the curve F(x, y) respectively correspond to the boundary points G1 and G2 of the light-transmitting housing; wherein, the parallel hypotenuses of the cross-section of parallelogram GaGbGcGd and the cross-section of parallelogram GcGdGeGf are inclined at different angles in different directions, that is, the two parallelogram cross-sections share GcGd as a common side, the two parallel hypotenuses GaGc and GbGd of the cross-section of parallelogram GaGbGcGd are inclined at a certain angle towards the inside of the radar, while the two parallel hypotenuses GcGe and GdGf of the cross-section of parallelogram GcGdGeGf are inclined at a certain angle towards the outside of the radar.

[0129] Figure 8 The principle diagram of eliminating ghost images by the light-transmitting housing with a curved surface structure is shown. It can be seen that by using the different inclination angles of the two parallelogram cross-sections, the spatial exit angle of the secondary reflection of the transmitting light path is staggered from the spatial incident angle of the secondary reflection of the echo signal in the pitch direction. When the staggered angle is greater than the receiving field of view angle, the ghost image phenomenon will disappear.

[0130] Here, it is assumed that only the inner wall of the light-transmitting housing generates reflection signals. In the yoz plane, most of the transmitted light beam 1 reflected by the mirror will be refracted out through the light-transmitting housing. Since the two parallel hypotenuses GaGc and GbGd are parallel, they have a similar function to a flat plate structure and will not change the exit direction of the light beam 1, thus ensuring that its spatial angle directivity remains unchanged; assume that the angles between the two parallel hypotenuses GaGc and GbGd and the z-axis are δ E , the pitch angle of the light beam 1 becomes -2δ after being reflected by the inner surface of the light-transmitting housing E , and then it is reflected by the mirror and exits from another position in the transmitting area of the light-transmitting housing. The angle of the light beam exiting through the light-transmitting housing is the same as the angle before exiting, that is, δ 2E = 2δ E ;

[0131] The received ghost echo signal 2 enters the light-transmitting housing at a pitch angle of δ 1R , where δ 1R = 2δ E . Similarly, since the receiving area of the housing is similar to a flat plate structure, the echo signal 2 can enter the mirror at this angle and be reflected by the mirror and then reflected by the receiving area of the light-transmitting housing. The pitch angle after reflection becomes δ 1R + 2δ R , and is reflected by the mirror again and exits at a pitch angle of δ2R Transmission, where δ 2R = 2δ E + 2δ R , that is to say, after introducing the curved light-transmitting housing, the ghost receiving signal is offset by δ in the pitch angle relative to the original receiving field of view 2R . As long as δ 2R is greater than the system receiving field of view V R , that is, 2δ E + 2δ R > V R , the ghost receiving signal can be eliminated.

[0132] It can be seen that when δ E = -δ R , it is similar to the case of a flat housing. The secondary transceiver signals coincide in the pitch direction. Therefore, the ghost signal can only be eliminated by introducing an anti-reflection film within the horizontal angle where the ghost signal is generated. For the curved light-transmitting housing, the way to eliminate the ghost is to offset the secondary transceiver signal fields of view in the pitch direction, and there is no need to use the method of plating an anti-reflection film to eliminate the ghost signal.

[0133] In this embodiment, combined with Figure 9 , in order to ensure that when the mirror performs an optical path scan, the directivity of the optical path before and after passing through the light-transmitting housing remains unchanged at different field of view angles, the conditions that the cross-sectional scan trajectory curve F(x, y) of the light-transmitting housing needs to satisfy are also analyzed in the xoy plane: For the central ray of the emitted light, the distance between it and the origin coordinates is The emitted optical path is reflected by the mirror and exits at the field of view angle ν, and the direction vector is To keep the optical path exit direction unchanged, this direction vector must coincide with the normal vector of the surface or be perpendicular to the tangent vector of the curve to meet the perpendicular incidence condition and ensure that the emitted optical path does not deflect after being refracted by the light-transmitting housing.

[0134] Among them, the equation of the trajectory curve F(x, y) changes with the parameter α and is similar to the equation of a circle with point C as the center. The difference is that as the parameter α changes, the x coordinate of the center C also changes. Therefore, the relational expression seven can be constructed as a parametric equation to describe F(x(α), y(α)):[[]]

[0135]

[0136] According to the relational expression seven, the tangent vector of the curve can be expressed as:[[]]

[0137]

[0138] According to the optical path exit direction vector and the curve tangent vector Vertical, that is The relational expression eight can be obtained:

[0139]

[0140] Combined with the initial value conditions for integral operation, the parametric equation F(x, y) of the trajectory curve can be obtained to satisfy the relational expression nine:

[0141]

[0142] where ρ0 = |CG2| - [(2α2 + cotα2)Ys0 - b(cos2α2 - 2)cscα2], |CG2| represents the distance between the boundary point G2 of the light-transmitting housing and the intersection point C of the optical path and the mirror at the maximum field-of-view angle v2m, and α2 represents the α parameter corresponding to the maximum field-of-view angle v2m, that is From the relational expression nine, it can be seen that in the limit cases of Ys0 = 0, b = 0, and a = r, x(α) = ρ0cos2α, y(α) = ρ0sin2α, and the trajectory curve F(x, y) is a circular curve with the origin O as the center and a radius of ρ0. That is, when the incident light is incident on the x-axis and the distance between the two mirrors is 0, the reflected light rotates around O with twice the angular velocity as the mirror rotates.

[0143] After determining the thickness d of the light-transmitting housing through the scanning trajectory equation of the relational expression nine, the heights H1 and H2 of the cross-sections of the parallelograms GaGbGcGd and GcGdGeGf are determined by the previous constraint relational expressions, and then the tilt angles δ E 、δ R are obtained, thereby obtaining an optimized curved light-transmitting housing.

[0144] Such as Figures 10 to 12 , and combined with Figures 1 to 9 , taking the rotary mirror type 16-line lidar as an example, the relationship between its performance indicators and structural parameters is described here:

[0145] The horizontal field-of-view angle range of the 16-line lidar is 120°, that is, ν1m = 30°, ν2m = 150°, the vertical field-of-view angle ranges from -5° to +5°, the pitch angle between each beam is 0.67°, the light source output width Ws = 7mm. According to the relational expression one, considering the limit condition where the scanning mirror parameters exactly meet the field-of-view conditions, that is, the minimum rotor radius At this time a = r, As long as the minimum rotor radius r ≥ r m , by selecting appropriate parameters for a, the emission optical path can be made to output within the given field of view. Under the limit conditions, only one value meets the requirements. As the radius r increases, the range of parameters that a can select also increases.

[0146] According to the lidar equation, i.e., relation four, the detection distance performance index is analyzed. It should be noted that the detection distance performance also needs to consider the receiving factor. The larger the rotation radius, the larger the echo cross-section, and the detection distance also increases accordingly. At the same rotation radius, it is necessary to increase the reflector width 2a as much as possible to improve the detection distance. Let the minimum detectable power P m of the receiving system be 2.2 nW, the output power P0 of the lidar be 75 W, and the efficiency η r of the receiving lens be 90%, and the efficiency η e of the transmitting lens be 90%. To enable the lidar to achieve a detection distance of 100 m for a target with a reflectivity ρ of 10% directly in front, the effective receiving area A r of the echo signal is 10.57 mm 2 . The receiving aperture is square, and it can be obtained that the half-width a of the reflector is 23 mm. The distance 2b between the plane reflectors is mainly limited by the rotor structure and the size of the motor bearings. Here, b = 16 mm, so the rotation radius is determined to be r = 28 mm.

[0147] Under the condition of a fixed rotor size (rotation radius), the boundary points of the light-transmitting housing are determined by the field of view, the position and width of the transmitting beam, and the position of the light-transmitting housing. According to relation two and the relationship between the minimum field-of-view angle ν1m and the maximum field-of-view angle ν2m, relation ten can be obtained:

[0148]

[0149] When the position of the light-transmitting housing is the limit position closest to the origin, i.e., Ysg = r, the width of the light-transmitting housing reaches the minimum value. The horizontal position of the right boundary point G2 is as close as possible to the rotor edge to ensure that the system volume is basically not increased. Here, x G2 is taken as 30 mm, and the horizontal position of the left boundary point G1 can be appropriately selected wider, specifically: x G1 = -40 mm, Xg = -5 mm, Wg = 35 mm.

[0150] From relation two, the constraint relation eleven can be obtained as follows:

[0151]

[0152] According to the above constraint relation eleven, here Ys1 = 13 mm is selected, and the center position of the light source is Ys0 = 16.5 mm.

[0153] According to the pitch angle range of the 16-line lidar: -5° ≤ θ ≤ 5°, from Equation 3, it can be obtained that H1 ≥ 10.13 mm. It should be noted that since the calculations of the above positions are all close to the extreme cases, appropriate dimensional allowances can be added in actual applications.

[0154] Regarding the optimized layout consideration of the position of the receiving lens with a square aperture for the lidar:

[0155] The first optimized layout method is that, to maximize the detection distance at the forward angle of the lidar and receive all signals within the specular reflection area, it can be calculated that Ye1 = 4.97 mm, Ye2 = -27.56 mm, and Wr = 32.53 mm.

[0156] The second optimized layout method is to determine the receiving lens parameters Ye1 and Ye2 by maximizing the area of the region enclosed by the four curves yA(υ), yA′(υ), yB(υ), yB′(υ) and the two straight lines Ye1 and Ye2, and solve for the appropriate values by the bisection method as follows:

[0157] Corresponding to Figure 5 , select a value of Ye1, calculate the abscissas νA1 and νA1′ of the intersections of this value with the curves yA and yA′ respectively, and then calculate the coordinates vB1 and vB2 of Ye2 = Ye1 - Wr with the curve yB, and construct the function: g(Ye1) = |vA1 - νA1′| - |vB1 - vB2|, where, if Then calculate If Calculate Iterate k times repeatedly like this until |g(Ye1 k )| < ε, where ε is the given error value for the solution.

[0158] Then, according to Figure 5 the relationship between the effective receiving aperture length and the lidar field of view change shown, solve for Ye1 = 4.55 mm and Ye2 = -27.98 mm, with the error value ε ≤ 0.02 mm.

[0159] Combining the system parameters obtained above with the lidar equation, the relationship curves between the maximum detection distance and the scanning field of view angle for the above two receiving lens layout methods can be obtained as shown in Figure 11As shown, it can be seen that the relationship between the maximum detection distance and the field of view angle is the same for the two layout methods within a field of view range greater than 92°, and the effective detection areas of the echoes of the two are the same. Within the field of view range less than 92°, for the first layout method, the curve characteristic is that the maximum detection distance of 100 m remains unchanged within the range of 85 - 90°, and gradually decreases towards both sides; for the second layout method, the curve characteristic is that the maximum detection distance of 100 m corresponds to only one angle value, which appears near 83.6°, and then gradually decreases towards both sides. Among them, within the field of view angle range of 83.6 - 92°, it is less than the first layout method, while within the field of view angle range of 50° to 83.6°, it is greater than the first layout method, and the integral of the maximum detection distance within the entire field of view range is maximized.

[0160] After determining the x-axis coordinate and width of the center of the light-transmitting housing based on the above optical and structural parameters, consider choosing a light-transmitting housing with a planar structure or a curved surface structure respectively. Among them, for the planar light-transmitting housing, mainly consider the influence of the ghost image factor. The ghost image is mainly related to the distance between the light-transmitting housing and the rotation center. Calculate the marginal field of view angle according to the marginal ray of the emission optical path. Table 1 shows the relevant data of Ysg and the field of view angle range [ν1g, ν2g] where the ghost image appears, as well as the corresponding incident angle range [ν1i, ν2i] of the flat surface of the light-transmitting housing.

[0161] Table 1 Vertical distance from the center of the planar light-transmitting housing to the origin and the field of view angle range where the ghost image appears

[0162]

[0163]

[0164] After determining the position and width of the planar light-transmitting housing, design an antireflection coating for the incident angle range [ν1i, ν2i] to reduce surface reflection, which can reduce the influence of the ghost image.

[0165] For the case where the light-transmitting housing has a curved surface structure, select different tilt angles δ of two parallelogram cross-sections E = 7°, δ R = 7°, which can meet the condition of eliminating the ghost image.

[0166] According to the requirement that the central ray direction of the emitted light remains unchanged before and after passing through the light-transmitting housing for different field of view angles, combined with the above-obtained parameters and curve parameter equation nine, calculate the scanning trajectory curve F(x, y) of the cross-section of the light-transmitting housing at different positions perpendicular to the xoy plane, as Figure 12As shown, a reasonable curved surface light-transmitting housing structure can be made by combining two parallelogram cross-sections according to the scanning trajectory curve F(x, y), which can eliminate the ghosting phenomenon of the lidar while minimizing the influence on the scanning directivity of the outgoing light path, thereby improving the detection angle accuracy of the lidar.

[0167] The rotating mirror type 16-line lidar constructed based on the above design method makes reasonable use of the overall structural space, can reduce the spatial redundancy, has a high compactness, and the volume of its scanning optical area can reach V = LD(H1 + H2) = 70×58×42.66 mm 3 , truly achieving the balance between performance improvement and structural compactness of the rotating mirror type multi-line lidar.

[0168] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. Design method of a rotating mirror multi-line lidar, wherein the lidar field of view of the rotating mirror multi-line lidar includes a horizontal swing scanning field of view and a pitch scanning field of view, characterized in that, Including the following design steps: According to the angular range requirement of the flat swing scanning field of view and the output aperture width of the light source, determine the size of the reflector and the constraint conditions between the position of the light source and the flat swing scanning field of view; According to the position of the light source, the output aperture width of the light source, the minimum field angle of the planar pendulum scanning field of view 1 and the maximum field angle , determine the constraint conditions between the width of the light-transmitting housing and the edge position coordinates of the light-transmitting housing; Based on the angular range of the pitch scanning field of view, the output aperture width of the light source, and in combination with the maximum field of view angle of the pan scanning field of view , determine the minimum spatial height of the emission optical path of the light source ; Based on the principles of maximizing the cross-section of the received echo signal and the highest space utilization rate, determine the aperture shape of the receiving lens, and based on the system's maximum detection distance requirement, determine the rotation radius of the reflector and the aperture size of the receiving lens through the lidar equation; Establish a relationship diagram between the effective receiving aperture length of the receiving lens and the lidar field of view, and optimize the layout of the position of the receiving lens based on the relationship diagram; Determine the shape of the light-transmitting housing according to the central horizontal position and width of the light-transmitting housing; 2. The design method of the rotating mirror type multi-line lidar according to claim 1, wherein Based on the principles of maximizing the cross-section of the received echo signal and the highest space utilization rate, determine that the receiving aperture shape of the receiving lens is square; based on the system's maximum detection distance requirement, calculate the effective receiving area of the echo signal through the lidar equation, and determine the rotation radius of the reflector and the aperture size of the receiving lens through the effective receiving area of the echo signal; 3. The design method of the rotating mirror type multi-line lidar according to claim 2, wherein The optimization method for arranging the position of the receiving lens is: ensure the front angle of the rotating mirror type multi-line lidar, maximize the detection distance of the rotating mirror type multi-line lidar, and receive all signals within the specular reflection area of the reflector, and determine the optimal position of the receiving lens; 4. The design method of the rotating mirror type multi-line lidar according to claim 2, characterized in that The optimization method for arranging the position of the receiving lens is: maximize the integral of the effective receiving area of the echo signal within the entire field of view of the lidar field of view, and determine the optimal position of the receiving lens through the bisection method or the Newton iteration method; 5. The design method of the rotating mirror type multi-line lidar according to claim 3 or 4, characterized in that, According to the central horizontal position and width of the light-transmitting housing, determine that the light-transmitting housing selects a planar structure. According to the vertical distance of the center of the light-transmitting housing from the origin and the angle of the lidar field of view, calculate the angular range of the ghost image, and the incident angle range corresponding to the light-transmitting flat surface of the light-transmitting housing and the angular range of the ghost image, and design an anti-reflection coating on the flat plate according to the incident angle range to eliminate the ghost image; 6. The design method of the rotating mirror type multi-line lidar according to claim 3 or 4, characterized in that, According to the horizontal position and width of the light-transmitting housing, determine that the light-transmitting housing selects a curved surface structure. Among them, the vertical cross-sections of the emission area and the reception area of the light-transmitting housing with the curved surface structure are respectively composed of a parallelogram cross-section with different inclination angles, and the included angle between the hypotenuses of the emission parallelogram cross-section and the reception parallelogram cross-section is greater than the instantaneous reception field of view angle; 7. The design method of the rotating mirror type multi-line lidar according to claim 6, wherein, According to the direction vectors of the central rays of the emission optical path at different field of view angles, make a curve parametric equation perpendicular to the corresponding direction vectors, and scan the emission parallelogram cross-section and the reception parallelogram cross-section along the trajectory of the curve parametric equation to obtain the light-transmitting housing with the curved surface structure; Among them, the light-transmitting housing corresponding to the transmitting area is formed by scanning along the trajectory of the parametric equation of the curve, and the starting point and the ending point of the curve trajectory respectively correspond to the boundary points of the light-transmitting housing ; the light-transmitting housing corresponding to the receiving area is formed by scanning along the trajectory of the parametric equation of the curve, and the starting point and the ending point of the curve trajectory respectively correspond to the boundary points of the light-transmitting housing and ; among them, both of the two parallelogram cross-sections take as the common side, and the two parallel hypotenuses and of the parallelogram cross-section are inclined at a certain angle towards the inside of the radar, and the two parallel hypotenuses of the parallelogram cross-section and are inclined at a certain angle towards the outside of the radar. The two parallel hypotenuses and of the parallelogram cross-section 8. Rotating mirror type multi-line lidar, characterized in that, Including: A light-transmitting housing, on the light-transmitting surface of the light-transmitting housing, there are an emission area and a reception area; An emission unit, arranged inside the light-transmitting housing, is provided with a light source for emitting a laser signal, and the light source includes a plurality of light beams respectively emitting the laser signal towards different pitch angles; A receiving unit, disposed inside the light-transmitting housing, is provided with a receiving lens for receiving echo signals. A rotary scanning unit, disposed inside the light-transmitting housing and having a horizontal rotation degree of freedom, is provided with a mirror for reflecting the laser signal towards the emission area and for reflecting the echo signal returning to the reception area to the receiving lens. Among them, the position constraint condition of the light source, the size constraint condition of the mirror, the horizontal position and boundary constraint condition of the center of the light-transmitting surface of the light-transmitting housing, and the size and position constraint condition of the receiving lens are all obtained by using the rotating mirror type multi-line lidar design method described in any one of claims 1-7.

9. The rotating mirror type multi-line lidar according to claim 8, wherein A horizontal isolation component is provided inside the light-transmitting housing. The isolation component is used to separate the emission unit and the receiving unit vertically and is horizontally aligned with the intersection position of the emission area and the reception area. Among them, the upper edge of the receiving lens abuts against the bottom wall of the isolation component, and the lower edge of the receiving lens abuts against the inner bottom wall of the light-transmitting housing.

10. The rotating mirror type multi-line lidar according to claim 8, wherein, The receiving lens has a rectangular effective receiving area, the length of the effective receiving area is in the vertical direction and is a preset value, and the width of the effective receiving area is in the horizontal direction and satisfies the relation: ； In the formula, min represents the minimum value operation. max represents the maximum value operation. ； ； ； ； Wherein, a is half of the length of the reflecting surface of the mirror, 2b is the distance between two parallel reflecting surfaces of the mirror, r is the distance from the edge point of the reflecting surface to the rotation center of the mirror, is the field angle of the lidar field of view, is the angle between the reflecting surface and the horizontal plane, satisfying , is the vertical distance between the light source and the rotation center of the mirror, the vertical distance from the light-transmitting housing to the light source, the half-width of the light-transmitting housing, the horizontal distance between the center of the light-transmitting housing and the rotation center of the mirror, is the maximum value of the projection height corresponding to the effective receiving area in the vertical direction, is the minimum value of the projection height corresponding to the effective receiving area in the vertical direction.

11. The rotating mirror type multi-line lidar according to claim 8, wherein, The light-transmitting surface of the light-transmitting housing is a curved light-transmitting surface, and the curved light-transmitting surface is formed by scanning two parallelogram cross-sections along a space curve. The included angle between the hypotenuses of the two parallelogram cross-sections is greater than the instantaneous scanning field angle. Among them, the trajectory parametric equation of the space curve satisfies the relational expression: In the formula, , where represents the distance between the boundary point of the light-transmitting surface of the light-transmitting housing and the intersection point of the emission optical path of the light source and the reflecting surface of the reflecting mirror at the maximum field angle of the pendulum scanning field of view, is the angle between the reflecting surface of the reflecting mirror and the horizontal plane, corresponding to value at the maximum field angle, is the distance between the central ray of the emission optical path and the rotation center of the reflecting mirror; a is half of the length of the reflecting surface of the reflecting mirror, and r is the distance from the edge point of the reflecting surface to the rotation center axis of the reflecting mirror.

12. The rotating mirror type multi-line lidar according to any one of claims 8-11, characterized in that, The mirror is a multi-faceted mirror having at least two reflecting surfaces, and the included angle between each mirror surface and the horizontal plane is an acute angle or a right angle or an obtuse angle. The detection mode of the rotating mirror type multi-line lidar is single-shot multi-receive or multi-shot single-receive or multi-shot multi-receive, and the included angles between adjacent beam bundles of the rotating mirror type multi-line lidar are equal or unequal. Both the emission unit and the receiving unit adopt linear array or area array chips.

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