Lidar blind area compensation element design method, blind area compensation device and application

Abstract

The application discloses a kind of laser radar blind area compensation element design method, comprising the following steps, S1. According to blind area, baseline, original receiving system parameter, detector size, compensation element size, the axial difference of original receiving system image intercept and combined receiving system image intercept is obtained;S2. Through formula: the image focal length of compensation element is obtained;S3. According to the material quality of selecting compensation element, the curvature radius of compensation element is obtained in combination with compensation element selection.This application also provides a laser radar blind area compensation device, and the application of the above-mentioned method and device in off-axis laser radar blind area compensation.The beneficial effect is that: without changing original receiving system, relying on measured parameter combination optical formula can quickly complete compensation element parameter calculation, realize low-cost, high-efficiency blind area compensation, and the original detection blind area can be effectively reduced to 0.2m after use.

Description

Technical Field

[0001] This invention relates to the field of lidar technology, specifically to a design method, a blind zone compensation device, and its application for lidar blind zone compensation elements. Background Technology

[0002] Based on their optical path structure, existing lidar systems are mainly divided into two categories: coaxial lidar and off-axis (paraaxial / split-axis) lidar. The detection principles and blind zone formation mechanisms of these two types differ significantly. The near-range detection blind zone of coaxial lidar is primarily caused by electrical and optical stray factors such as device dead-zone response time, stray light reflection from the front-end optical window, crosstalk within the beam splitter, and near-field echo energy saturation overflow. Because the blind zone caused by the non-overlapping optical geometric fields of view is extremely small, the near-range detection problem is relatively easy to control.

[0003] Mainstream off-axis lidar systems, limited by their optical path geometry, inherently suffer from a near-range detection blind zone, a problem that is particularly pronounced. This blind zone is determined by the geometric coupling of three factors: the baseline length of the transmitting and receiving optical paths, the effective photosensitive size of the detector, and the focal length of the receiving lens. In the near-field region, the emitted laser spot and the receiving field of view cannot effectively intersect, resulting in a detection dead zone. In practical applications, the larger the system baseline length, the smaller the focal length of the receiving lens, and the smaller the effective size of the detector's photosensitive chip, the larger the near-range detection blind zone becomes, severely limiting the near-field detection performance of off-axis lidar.

[0004] Current industry solutions for addressing the blind zone problem in off-axis lidar generally involve replacing the detector with a larger one, adding multiple receiver channels, and reconstructing the optical path of the original receiver lens to reduce the blind zone. All of these solutions require significant modifications to the lidar's original optical structure and hardware architecture. This not only increases the cost of modification, raises the overall system complexity, and makes assembly and debugging more difficult, but also reduces the versatility of the original equipment. Therefore, it is impossible to achieve low-cost, high-efficiency blind zone compensation without altering the original receiver system. Summary of the Invention

[0005] The purpose of this invention is to provide a design method, a blind zone compensation device, and an application for a lidar blind zone compensation element that can achieve low-cost and high-efficiency blind zone compensation without modifying the original receiving system.

[0006] To achieve the above objectives, the basic solution of the present invention provides a design method for a lidar blind zone compensation element, comprising the following steps. S1. Based on the blind zone, baseline, original receiving system parameters, detector size, and compensation element size, obtain the axial difference between the image-side intercept of the original receiving system and the image-side intercept of the combined receiving system. ; S2. By formula: Obtain the image focal length of the compensation element ; in The original receiving system's image-side focal length. L is the image-side focal length of the combined system, and L is the total optical length of the combined system. This represents the axial difference between the image-side intercept of the original receiving system and the image-side intercept of the combined receiving system. S3. According to By selecting the material of the compensation element and combining it with the selection of the compensation element type, the radius of curvature of the compensation element can be obtained.

[0007] The advantages of this basic scheme are: without modifying the original receiving system, the parameters of the compensation element can be quickly calculated based on the measured parameters and optical formulas, thus achieving low-cost and high-efficiency blind zone compensation.

[0008] Preferably, in step S1, the following is obtained: The steps include: R1. Draw the off-axis principal ray based on the parameters; R2. Draw the critical edge rays of the compensation element to define the critical position of the blind zone; R3. The intersection point is obtained by extending the off-axis principal ray and the critical edge ray of the compensation element; R4. Calculate the axial difference between the image-side intercept of the original receiving system and the image-side intercept of the combined receiving system. .

[0009] Preferably, in step S1, the detector size includes the detector photosensitive length.

[0010] Preferably, in step S1, the size of the compensation element includes the light transmission aperture of the compensation element.

[0011] Preferably, in S3, the radius of curvature of the compensation element is solved by modeling and simulation using Zemax optical design software.

[0012] Secondly, the present invention provides a lidar blind zone compensation device, comprising an original receiving system and a compensation element, wherein the parameters of the compensation element are determined using the lidar blind zone compensation element design method described in any of the above schemes.

[0013] Preferably, the compensation element is disposed at the front end of the optical path of the original receiving system, and the two form a dual-optical-group combined optical path.

[0014] Preferably, the compensation element is a transmissive concave lens, a cylindrical concave lens, or a convex reflector.

[0015] Thirdly, the present invention provides the application of the radar blind zone compensation element design method and / or lidar blind zone compensation device as described above in off-axis lidar blind zone compensation.

[0016] The present invention has the following beneficial effects: 1. Without modifying the original receiving system, the parameters of the compensation element can be quickly calculated based on measured parameters and optical formulas, achieving low-cost and high-efficiency blind zone compensation. Furthermore, after use, the original detection blind zone can be effectively reduced to 0.2m.

[0017] 2. The compensation element can be designed and developed independently without needing to be synchronized with the original receiving system, which can reduce the overall R&D coordination cost and shorten the project cycle.

[0018] 3. It can be adapted to a variety of existing off-axis lidars with different structures without requiring modifications to the original receiving system, thus enhancing its versatility and reusability.

[0019] 4. The original receiving system and compensation components can be manufactured, assembled, and debugged separately, making the production process more flexible and facilitating subsequent individual maintenance and replacement of compensation components. Attached Figure Description

[0020] Figure 1 This is the optical path diagram of Embodiment 1 of the present invention.

[0021] Figure 2 This is the optical path diagram of Embodiment 2 of the present invention.

[0022] Figure 3 This is the optical path diagram of Embodiment 3 of the present invention.

[0023] Figure 4 These are optical path geometry analysis diagrams of embodiments 1-3 of the present invention. Detailed Implementation

[0024] The "original receiving system" involved in this invention specifically refers to the lidar body receiving device that realizes the target detection signal receiving function, which is the original basic signal receiving unit of lidar.

[0025] The "compensation element" involved in this invention is specifically used for signal compensation processing of the blind zone of lidar detection, i.e., a lidar blind zone compensation function component.

[0026] The "combined system" involved in this invention is an integrated detection system composed of the original receiving system and compensation elements, which work together to complete the radar's full-range signal reception and processing without blind spots.

[0027] In this invention, the object intercept of the combined system is the minimum axial distance along the detection axis of the combined system, from the system's incident reference plane to the target that the system can stably detect. When the axial distance of the target is less than this object intercept, the radar echo signal cannot be effectively identified even after joint processing by the original receiving system and the compensation element; this failed detection range is the radar blind zone. In the parameter analysis and geometric model calculation process of this invention, the spatial range represented by the object intercept of the combined system and the blind zone are consistent, and the two can be used interchangeably.

[0028] The reference numerals in the accompanying drawings of this invention include: a-off-axis principal ray, b-critical edge ray of the compensation element, - The intersection of the off-axis principal ray and the edge ray of the compensation element; d: Optical distance between the original receiving system and the compensation element; L: Total optical length of the combined system (size limit after compensation); D1: Detector dimensions; D2: Dimensions of the compensation element; The original receiving system's image-side focal length; : Compensation element image focal length; Image focal length of the combined system; l: Object intercept of the combined system (which can be equivalent to the blind zone in this scheme); Image intercept of the combined system; Image intercept of the original receiving system; : The axial difference between the image-side intercept of the original receiving system and the image-side intercept of the combined receiving system.

[0029] The radar blind zone compensation element design method provided in this embodiment includes the following steps. S1. Based on the blind zone, baseline, original receiving system parameters, detector size, and compensation element size, obtain the axial difference between the image-side intercept of the original receiving system and the image-side intercept of the combined receiving system. ; S2. By formula: Obtain the image focal length of the compensation element ; in The original receiving system's image-side focal length. L is the image-side focal length of the combined system, and L is the total optical length of the combined system. This represents the axial difference between the image-side intercept of the original receiving system and the image-side intercept of the combined receiving system. S3. According to By selecting the material of the compensation element and combining it with the selection of the compensation element type, the radius of curvature of the compensation element can be obtained.

[0030] Better yet, in step S1, we obtain The steps include: R1. Draw the off-axis principal ray a based on the parameters; R2. Draw the critical edge ray b of the compensation element to define the critical position of the blind zone; R3. Extend the off-axis principal ray a and the critical edge ray b of the compensation element to obtain the intersection point; R4. Calculate the axial difference between the image-side intercept of the original receiving system and the image-side intercept of the combined receiving system. .

[0031] Better still, in step S1, the detector size includes the detector photosensitive length.

[0032] Even better, in step S1, the size of the compensation element includes the light transmission aperture of the compensation element.

[0033] Even better, in S3, the radius of curvature of the compensation element can be solved by modeling and simulating using Zemax optical design software.

[0034] Secondly, this embodiment also provides a lidar blind zone compensation device, including the original receiving system and the compensation element. The parameters of the compensation element are determined by the lidar blind zone compensation element design method of any of the above embodiments.

[0035] Even better, the compensation element is placed at the front end of the optical path of the original receiving system, and the two form a dual-optical-group combined optical path.

[0036] Even better, the compensation element is a transmissive concave lens, a cylindrical concave lens, or a convex reflector.

[0037] Furthermore, this embodiment also provides the application of the lidar blind zone compensation element design method and / or lidar blind zone compensation device provided in the above embodiments in off-axis lidar blind zone compensation. Example 1

[0038] In this embodiment, a concave transmission lens is selected as the compensation element, specifically as follows: Figure 1 As shown.

[0039] The relevant design parameters for this embodiment are as follows: The baseline length is 15mm; The original receiving system had an inherent blind zone of 1m; The optimized target blind zone is 0.2m; The optical distance d between the original receiving system and the compensation element is 5.34 mm; The total optical length L of the combined system is 12.8 mm; The detector's photosensitive length D1 is 0.4 mm; The aperture diameter D2 of the compensation element is 1mm; Original receiving system image-side focal length It is 5.5mm; One specific implementation involves using CAD software to calculate the difference between the image intercept of the original receiving system and the image intercept of the combined system. The principle of optical path solving is as follows: Figure 4 As shown, the specific steps are as follows: R1. Based on the known blind zone distance, baseline length, detector size, and compensation element aperture parameters, plot the off-axis principal ray a of the compensation element under the corresponding blind zone condition; R2. Draw the edge rays according to the aperture constraint of the compensation element, and take the critical state where the edge rays are exactly tangent to the photosensitive edge of the detector; when the target distance is too close, the echo beam is limited by the light transmission aperture of the compensation element, the edge of the beam overflows the photosensitive surface of the detector, the complete echo cannot be collected, the lidar signal is lost and a detection blind zone is formed. R3. Extend the off-axis principal ray a and the critical edge ray b of the compensation element in opposite directions to obtain the intersection point. The intersection The image of the near-range virtual target point corresponding to the 0.2m critical blind zone is the image-side intercept of the combined system. Using this image-side intercept as a unified reference, the axial installation positions of the image plane of the original receiving system and the combined receiving system with added compensation elements are calibrated. Axial dimension calculations are performed using an optical path geometric model to obtain the axial difference between the image-side intercepts of the original receiving system and the combined receiving system. It is 2mm.

[0040] The optical parameters of the combined system in this embodiment are as follows: Combined system image focal length It is 7.19mm; The object intercept l of the combined system is -200mm (this scheme adopts the geometric optics standard notation rule, the target is located in the physical area on the incident side of the system, the object intercept is negative, and its absolute value corresponds to the optimized target blind zone of 0.2m). Image intercept of combined system It is 7.46mm; Substitute the above parameters into formula 1 for calculating the focal length of the optical combination. Formula 1:

[0041] The focal length of the compensation element is obtained by solving the problem. It is -7.87mm.

[0042] Based on the obtained focal length of the compensation element, optical materials are selected. In this embodiment, optical glass is used as the lens substrate, with a refractive index Nd=1.52 and an Abbe number Vd=64.2. The transmission concave lens in this embodiment is specifically a plano-concave single-spherical thin lens, with the lens plane facing the image side (detector side) and the curved surface facing the object side incident side. The corresponding calculated radius of curvature is -4mm. This radius of curvature can be solved through modeling and simulation using Zemax optical design software, or directly calculated using geometric optics theory formulas. The complete optical path of the compensation element is as follows: Figure 1 As shown.

[0043] The transmissive concave lens provided in this embodiment is placed at the front end of the optical path of the original receiving system, forming a dual-beam combination optical path; after use, the minimum detection blind zone of the lidar is reduced from the original 1m to 0.2m. Specifically, the light rays are emitted from the object being measured and pass through it sequentially from above. Figure 1 After passing through the concave lens, the incident surface of the original receiving system, and the exit surface of the original receiving system, it enters the detector at the bottom. Figure 1 (Not shown in the drawing). Example 2

[0044] In this embodiment, a cylindrical concave lens is selected as the compensation element. This cylindrical concave lens has optical power only in one direction, and can only reduce the detection blind zone in this dimension. The specific optical path structure is as follows: Figure 2 As shown.

[0045] The relevant design parameters for this embodiment are as follows: The baseline length is 15mm; The original receiving system had an inherent blind zone of 1m; The optimized target blind zone is 0.2m; The optical distance d between the original receiving system and the compensation element is 5.34 mm; The total optical length L of the combined system is 12.8 mm; The detector's photosensitive length D1 is 0.4 mm; The aperture diameter D2 of the compensation element is 1mm; Original receiving system image-side focal length It is 5.5mm; One specific implementation involves using CAD software to calculate the difference between the image-side intercept of the original receiving system and the image-side intercept of the combined system. The optical path solution principle is as follows: Figure 4 As shown, the specific steps are as follows: R1. Based on the known blind zone distance, baseline length, detector size, and compensation element aperture parameters, plot the off-axis principal ray a of the compensation element under the corresponding blind zone condition; R2. Draw the edge rays according to the aperture constraint of the compensation element, and take the critical state where the edge rays are exactly tangent to the photosensitive edge of the detector; when the target distance is too close, the echo beam is limited by the light transmission aperture of the compensation element, the edge of the beam overflows the photosensitive surface of the detector, the complete echo cannot be collected, the lidar signal is lost and a detection blind zone is formed. R3. Extend the off-axis principal ray a and the critical edge ray b of the compensation element in opposite directions to obtain the intersection point. The intersection The image of the near-range virtual target point corresponding to the 0.2m critical blind zone is the image-side intercept of the combined system. Using this image-side intercept as a unified reference, the axial installation positions of the image plane of the original receiving system and the combined receiving system with added compensation elements are calibrated. Axial dimension calculations are performed using an optical path geometric model to obtain the axial difference between the image-side intercepts of the original receiving system and the combined receiving system. It is 2mm.

[0046] The optical parameters of the combined system in this embodiment are as follows: Combined system image focal length It is 7.19mm; The object intercept l of the combined system is -200mm (this scheme adopts the geometric optics standard notation rule, the target is located in the physical area on the incident side of the system, the object intercept is negative, and its absolute value corresponds to the optimized target blind zone of 0.2m). Image intercept of combined system It is 7.46mm; Substitute the above parameters into formula 1 for calculating the focal length of the optical combination. Formula 1:

[0047] The focal length of the compensation element is obtained by solving the problem. It is -7.87mm (that is, the focal length of the meridional cylindrical surface that produces blind spot compensation is -7.87mm).

[0048] Based on the obtained focal length of the compensation element, optical materials are selected. In this embodiment, optical glass is used as the lens substrate, with a refractive index Nd=1.52 and an Abbe number Vd=64.2. The cylindrical concave lens in this embodiment has its concave cylindrical surface facing the object-side incident side, and its flat surface facing the image-side detector side. The calculated radius of curvature of the cylindrical surface in this compensation dimension is -4mm. This radius of curvature can be solved through modeling and simulation using Zemax optical design software, or directly calculated using geometric optics theory formulas. The complete optical path of the compensation element is as follows: Figure 2 As shown, the object-side beam is incident from bottom to top onto the concave cylindrical surface of the cylindrical lens, and after being shaped and corrected by the lens, it is transmitted upward to the rear imaging optics group.

[0049] The cylindrical concave lens provided in this embodiment is placed at the front end of the optical path of the original receiving system, forming a dual-beam combination optical path; after use, the minimum detection blind zone of the lidar is reduced from the original 1m to 0.2m. Specifically, the light rays are emitted from the object being measured and pass through it sequentially from above. Figure 2 After passing through the cylindrical concave lens, the incident surface of the original receiving system, and the exit surface of the original receiving system, it enters the detector at the bottom. Figure 2 (Not shown in the drawing). Example 3

[0050] In this embodiment, a convex reflector is selected as the compensation element, and the specific optical path structure is as follows: Figure 3 As shown.

[0051] The relevant design parameters for this embodiment are as follows: The baseline length is 15mm; The original receiving system had an inherent blind zone of 1m; The optimized target blind zone is 0.2m; The optical distance d between the original receiving system and the compensation element is 5.34 mm; The total optical length L of the combined system is 12.8 mm; The detector's photosensitive length D1 is 0.4 mm; The aperture diameter D2 of the compensation element is 1mm; Original receiving system image-side focal length It is 5.5mm; One specific implementation involves using CAD software to calculate the difference between the image-side intercept of the original receiving system and the image-side intercept of the combined system. The optical path solution principle is as follows: Figure 4 As shown, the specific steps are as follows: R1. Based on the known blind zone distance, baseline length, detector size, and compensation element aperture parameters, plot the off-axis principal ray a of the compensation element under the corresponding blind zone condition; R2. Draw the edge rays according to the aperture constraint of the compensation element, and take the critical state where the edge rays are exactly tangent to the photosensitive edge of the detector; when the target distance is too close, the echo beam is limited by the light transmission aperture of the compensation element, the edge of the beam overflows the photosensitive surface of the detector, the complete echo cannot be collected, the lidar signal is lost and a detection blind zone is formed. R3. Extend the off-axis principal ray a and the critical edge ray b of the compensation element in opposite directions to obtain the intersection point. The intersection The image of the near-range virtual target point corresponding to the 0.2m critical blind zone is the image-side intercept of the combined system. Using this image-side intercept as a unified reference, the axial installation positions of the image plane of the original receiving system and the combined receiving system with added compensation elements are calibrated. Axial dimension calculations are performed using an optical path geometric model to obtain the axial difference between the image-side intercepts of the original receiving system and the combined receiving system. It is 2mm.

[0052] The optical parameters of the combined system in this embodiment are as follows: Combined system image focal length It is 7.19mm; The object intercept l of the combined system is -200mm (this scheme adopts the geometric optics standard notation rule, the target is located in the physical area on the incident side of the system, the object intercept is negative, and its absolute value corresponds to the optimized target blind zone of 0.2m). Image intercept of combined system It is 7.46mm; Substitute the above parameters into formula 1 for calculating the focal length of the optical combination. Formula 1:

[0053] The focal length of the compensation element is obtained by solving the problem. It is -7.87mm.

[0054] Based on the obtained focal length of the compensation element, optical materials are selected. In this embodiment, optical glass is chosen as the substrate for the convex mirror, with a refractive index Nd=1.52 and an Abbe number Vd=64.2. The compensation element in this embodiment is a convex mirror, with the spherical convex surface facing the object-side incident side (the incident light is reflected on the convex surface), and the flat surface facing away from the object-side and towards the image-side detector. The calculated radius of curvature of the convex mirror surface is 6mm. This radius of curvature can be solved through modeling and simulation using Zemax optical design software, or directly calculated using geometric optics theory formulas. The complete optical path of the compensation element is as follows: Figure 3 As shown.

[0055] By combining the convex reflector provided in this embodiment with the original receiving system to form a combined system, the minimum detection blind zone of the lidar is reduced from 1m to 0.2m. Specifically, the light emitted from the object being measured passes sequentially from above... Figure 3 After passing through the reflecting surface of the convex mirror, the incident surface of the original receiving system, and the exiting surface of the original receiving system, the light enters the detector at the bottom. Figure 3 (Not shown in the drawing).

[0056] The above descriptions are merely embodiments of the present invention, and common knowledge regarding specific structures and characteristics in the solutions is not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the structure of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent.

Claims

1. A design method for a lidar blind zone compensation element, characterized in that: Includes the following steps, S1. Based on the blind zone, baseline, original receiving system parameters, detector size, and compensation element size, obtain the axial difference between the image-side intercept of the original receiving system and the image-side intercept of the combined receiving system. ; S2. By formula: Obtain the image focal length of the compensation element ; in The original receiving system's image-side focal length. L is the image-side focal length of the combined system, and L is the total optical length of the combined system. This represents the axial difference between the image-side intercept of the original receiving system and the image-side intercept of the combined receiving system. S3. According to By selecting the material of the compensation element and combining it with the selection of the compensation element type, the radius of curvature of the compensation element can be obtained.

2. The design method for lidar blind zone compensation element according to claim 1, characterized in that: In step S1, we obtain The steps include: R1. Draw the off-axis principal ray based on the parameters; R2. Draw the critical edge rays of the compensation element to define the critical position of the blind zone; R3. The intersection point is obtained by extending the off-axis principal ray and the critical edge ray of the compensation element; R4. Calculate the axial difference between the image-side intercept of the original receiving system and the image-side intercept of the combined receiving system. .

3. The design method for lidar blind zone compensation element according to claim 1 or 2, characterized in that: In step S1, the detector size includes the detector photosensitive length.

4. The design method of the lidar blind zone compensation element according to claim 3, characterized in that: In step S1, the size of the compensation element includes the light transmission aperture of the compensation element.

5. The design method for lidar blind zone compensation element according to claim 3 or 4, characterized in that: In S3, the radius of curvature of the compensation element is solved by modeling and simulation using Zemax optical design software.

6. A lidar blind zone compensation device, characterized in that: It includes the original receiving system and a compensation element, wherein the parameters of the compensation element are determined using the design method for lidar blind zone compensation element according to any one of claims 1-5.

7. The lidar blind zone compensation device according to claim 6, characterized in that: The compensation element is set at the front end of the optical path of the original receiving system, and the two form a dual-optical-group combined optical path.

8. The lidar blind zone compensation device according to any one of claims 6 or 7, characterized in that: The compensation element is a transmissive concave lens, a cylindrical concave lens, or a convex reflector.

9. The application of the design method for lidar blind zone compensation element and / or lidar blind zone compensation device as described in claims 1-8 in off-axis lidar blind zone compensation.

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