A large field of view high-precision laser angle measuring system

Abstract

The application discloses a large-view-field high-precision laser angle measuring system, and belongs to the technical field of laser angle measuring under a large view field.The system comprises a large-view-field high-precision laser angle measuring system which comprises an optical window and an optical system arranged in the optical window, and the system comprises a filter, a lens and a four-quadrant detector which are sequentially arranged along the input-to-output direction of light rays; the lens is a spherical mirror, and the filter is a narrow-band filter.The optical system has a relatively large aperture as far as the size, image quality and processing technology permit, so as to ensure that the system has high sensitivity, and can meet the requirement of detecting the angle information of a weak target with high precision at a long distance under a large view field.The application rationally utilizes the light-sensitive area, ensures the high uniformity and symmetry of the light spot in the view field, is beneficial to fully exerting the performance of the detector, meanwhile, only a single spherical lens is adopted, the system aberration is effectively corrected, and the processing cost of the lens is controlled.

Description

Technical Field

[0001] This application relates to the field of laser angle measurement technology with a large field of view, and more specifically, to a high-precision laser angle measurement system with a large field of view. Background Technology

[0002] The laser angle measurement optical system mainly receives the laser light diffusely reflected from the target onto the photosensitive surface of the four-quadrant detector. The corresponding four quadrants will generate current signals. When the light spot deviates from the center of the detector, the current signals generated in the four quadrants will differ. By performing sum and difference operations on the output signals of each quadrant, the position deviation information of the target can be obtained.

[0003] Currently used laser optical systems for angle measurement are limited by two main factors. First, the field of view restricts the measurable angle range to a maximum of only ±2° under high-precision conditions. Second, even with a large field of view, aberrations prevent high-precision angle measurement. Furthermore, in actual angle measurement, the weak diffuse reflection echo signal necessitates a large number of optical lenses for focusing, resulting in a large system size and weight. While aspherical lenses can reduce the number of lenses, their high manufacturing cost significantly impacts the overall size, weight, and cost of the angle measurement system. Summary of the Invention

[0004] To address at least one deficiency or improvement requirement of the existing technology, the present invention provides a large field-of-view high-precision laser angle measurement system. Based on a four-quadrant detector, it uses only a single spherical lens to correct system errors, achieving a simple, compact, small-sized, lightweight, and low-cost laser angle measurement lens optical system.

[0005] To achieve the above objectives, according to a first aspect of the present invention, a large field-of-view high-precision laser angle measurement system is provided, comprising: an optical window 1 and an optical system disposed inside the optical window 1, wherein the optical system comprises a filter 2, a lens 3 and a four-quadrant detector 4 arranged sequentially along the light input to output direction; the lens 3 is a spherical mirror and the filter 2 is a narrowband filter.

[0006] The large field-of-view high-precision laser angle measurement system as described above includes: the filter includes:

[0007] A first surface facing the optical window 1, wherein an antireflection film is coated on the first surface to reduce reflection and scattering; and a second surface coated with a filter film to receive target light signals and filter out non-target light signals.

[0008] The large field-of-view high-precision laser angle measurement system described above includes:

[0009] The optical window 1 adopts a concentric circle structure, and the axes of the optical window 1, the filter 2 and the lens 3 are collinear.

[0010] As described in the large field-of-view high-precision laser angle measurement system, the air gap between the filter 2 and the lens 3 is 0.5 mm, and the aperture of the narrow-band filter is 25 mm; the lens 3,

[0011] As described in the large field-of-view high-precision laser angle measurement system, the second surface of the filter and the lens 3 are used to correct system aberrations and / or chromatic aberrations.

[0012] As described in the large field-of-view high-precision laser angle measurement system, the optical system includes multiple optimized parameter features, including curvature variables, thickness variables, and air gap variables;

[0013] The curvature variable includes the radius of curvature of the first surface and the radius of curvature of the second surface of the lens 3;

[0014] The thickness variable is the thickness of the lens 3;

[0015] The air gap variable includes the air thickness on the back surface of the filter 2 and the air thickness on the back surface of the lens 3.

[0016] As described in the large field-of-view high-precision laser angle measurement system, the thickness variable ranges from 0.5mm to 25mm, and the air gap variable ranges from 0.2mm to 25mm.

[0017] According to a second aspect of the present invention, an aberration correction method for a large field-of-view high-precision laser goniometer system is also provided, employing the large field-of-view high-precision laser goniometer system described in any of the preceding claims, the method comprising:

[0018] Determine aberrations, wherein the aberrations include spherical aberration, coma, astigmatism, and distortion;

[0019] The uniformity of the light spot is selected as a quality characteristic value, and the weighting parameters of each aberration are determined.

[0020] The Taguchi method was used to optimize the aberration weight parameters, and the optimal combination of aberration weights for each aberration weight parameter was determined through range analysis and variance analysis.

[0021] Based on the optimal aberration weight combination, the aberration correction result is obtained by using optical simulation software with a default function combined with a special operand method.

[0022] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects:

[0023] The large field-of-view high-precision laser angle measurement system includes an optical window 1 and an optical system disposed within the optical window 1. The system includes a filter 2, a lens 3, and a four-quadrant detector 4 arranged sequentially along the light input to output direction; the lens 3 is a spherical mirror, and the filter 2 is a narrow-band filter. Within the limits of size, image quality, and manufacturing process, this optical system has the largest possible relative aperture to ensure high system sensitivity. It can also detect high-precision angle information of faint targets at long distances within a large field of view. Simultaneously, the form and composition of this optical system rationally utilize the photosensitive area, ensuring high uniformity and symmetry of the light spot within the field of view, which is beneficial for fully utilizing the detector's performance. Furthermore, while detectors in general optical systems are mostly located behind the focal point, the detector in this optical system is located in front of the focal point, effectively controlling the lens size. The optical system of this invention uses only a single spherical lens, effectively correcting system aberrations and controlling lens manufacturing costs. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 A schematic diagram of a large field-of-view, high-precision laser angle measurement system provided in an embodiment of this application;

[0026] Figure 2 A schematic diagram of the principle of the four-quadrant detector provided in the embodiments of this application;

[0027] Figure 3 A schematic diagram illustrating the analysis results of normalized numbers for different fields of view in the embodiments of this application;

[0028] Figure 4 This is a schematic diagram of the fitting error analysis curve provided in an embodiment of this application. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the 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 merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0030] The terms "first," "second," "third," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or apparatuses.

[0031] Figure 1 A schematic diagram of a large field-of-view, high-precision laser angle measurement system according to an embodiment of the present disclosure is shown.

[0032] See Figure 1 A large field-of-view high-precision laser angle measurement system includes: an optical window 1 and an optical system disposed inside the optical window 1. The optical system includes a filter 2, a lens 3 and a four-quadrant detector 4 arranged sequentially along the light input to output direction; the lens 3 is a spherical mirror and the filter 2 is a narrowband filter.

[0033] Optical window 1 is a sealing element used to isolate the external environment from the internal system of the lens. It can adopt a concentric circle structure to achieve maximum correction of system aberrations. The main requirements for the material are, for example, good thermal stability, high transmittance in a specific wavelength band, and the window's protective function.

[0034] The filter includes: a first surface facing the optical window 1, wherein the first surface is coated with an antireflection film to reduce reflection and scattering; and a second surface coated with a filter film to receive target light signals and filter out non-target light signals.

[0035] In one embodiment, filter 2 is a narrowband filter, which can absorb stray light to a large extent and filter out stray light other than the target light. To meet the requirements of laser angle measurement under a large field of view, an anti-reflection coating can be deposited on the front surface and a filter coating can be deposited on the rear surface.

[0036] This invention employs narrowband filtering, which provides excellent transmission performance for the operating band and strong suppression of background noise.

[0037] This invention, while meeting the requirements of high light throughput and laser spot quality, uses a single spherical lens to correct system aberrations instead of an aspherical lens, effectively controlling processing costs.

[0038] The four-quadrant detector 4 consists of four photosensitive surfaces with identical performance. Figure 2The schematic diagram illustrates the principle of a four-quadrant detector. The echo signal reflected from the target passes through the front-end optical system and illuminates the four-quadrant detector, generating current signals in the four quadrants (1, 2, 3, 4). The current intensity is proportional to the light-receiving area.

[0039] Figure 2 The outer circle represents the four-quadrant detector, and the shaded area within the inner circle represents the laser spot formed by the echo signal. As the laser spot moves across the four-quadrant detector, the light-receiving area in each quadrant changes, causing changes in the current intensity in each quadrant. After current-to-voltage conversion and analog-to-digital conversion (A / D conversion) of the changes in current in each quadrant, the displacement (x, y) of the laser spot center relative to the center of the four-quadrant detector can be calculated through data processing.

[0040] The laser angle measurement system uses a four-quadrant detector as the receiving device. Diffuse laser light forms a spot on the four-quadrant detector, thus outputting angle information. In order to measure the distribution of laser energy in the four quadrants, the laser energy spot on the four-quadrant detector must have a certain area, and the spot must have good symmetry and uniformity.

[0041] The optical system of the present invention includes multiple optimized parameter features, wherein the optimized parameter features include curvature variables, thickness variables, and air gap variables;

[0042] The curvature variable includes the radius of curvature of the first surface and the radius of curvature of the second surface of the lens 3;

[0043] The thickness variable is the thickness of the lens 3;

[0044] The air gap variable includes the air thickness on the back surface of the filter 2 and the air thickness on the back surface of the lens 3.

[0045] Preferably, the thickness variable ranges from 0.5mm to 25mm, and the air gap variable ranges from 0.2mm to 25mm. It should be noted that there are no fewer than a hundred commonly used optical materials, and optimization requires controlling factors such as the applicable temperature range, processing difficulty, cost, and light transmittance of the materials.

[0046] The present invention will be further described in detail below with reference to the accompanying drawings and optimized embodiments:

[0047] A large field-of-view, high-precision laser angle measurement system includes: an optical window 1 and an optical system disposed inside the optical window 1. The optical system includes a filter 2, a lens 3, and a four-quadrant detector 4 arranged sequentially along the light input to output direction. The lens 3 is a spherical mirror, and the filter 2 is a narrowband filter.

[0048] The optical window has a diameter of 43mm, a center thickness of 4mm, a first surface radius of curvature of 30mm, a second surface radius of curvature of 26mm, and a distance of 11mm from the filter.

[0049] The narrowband filter has a diameter of 25mm and a center thickness of 3mm. Its first surface has an infinite radius of curvature, its second surface has an infinite radius of curvature, and its distance from the lens is 0.5mm.

[0050] The spherical lens is made of H-ZLAF90 material, with an aperture of 32mm, a center thickness of 9mm, a first surface radius of curvature of 22mm, a second surface radius of curvature of 250mm, and a distance of 10mm from the detector.

[0051] In this embodiment, the technical specifications of the optical receiving system are as follows:

[0052] 1. Effective light transmission aperture: 25mm;

[0053] 2. Focal length: 26.3mm;

[0054] 3. Optical system length: 37.5mm;

[0055] 4. Field of view: The maximum field of view is ±10°;

[0056] Anti-reflective coatings are applied to the front and back of the optical window, the front of the narrow-band filter, and the front and back surfaces of the spherical lens, resulting in an overall transmittance of over 90% for the optical system.

[0057] This invention also provides an aberration correction method for a large field-of-view high-precision laser goniometer system, the method of which includes the following:

[0058] Determine aberrations, wherein the aberrations include spherical aberration, coma, astigmatism, and distortion;

[0059] The uniformity of the light spot is selected as a quality characteristic value, and the weighting parameters of each aberration are determined.

[0060] The Taguchi method was used to optimize the aberration weight parameters, and the optimal combination of aberration weights for each aberration weight parameter was determined through range analysis and variance analysis.

[0061] Based on the optimal aberration weight combination, the aberration correction result is obtained by using optical simulation software with a default function combined with a special operand method.

[0062] Specifically, the laser detection optical system uses a four-quadrant detector as the receiving device. Diffuse laser light forms a spot on the four-quadrant detector, thereby outputting angle information. In order to measure the distribution of laser energy in the four quadrants, the laser energy spot on the four-quadrant detector must have a certain area, and the spot must have good symmetry and uniformity.

[0063] Therefore, the basic aberrations that need to be considered are mainly spherical aberration, coma, astigmatism, and distortion.

[0064] To improve design quality, the Taguchi method was applied to analyze the impact of fundamental aberrations on spot uniformity. Based on professional knowledge and extensive design experience, error factor levels were determined, and spot uniformity was selected as the quality characteristic value. The parameters of each aberration weight were optimized using the Taguchi method, and the optimal combination of each aberration weight parameter was determined through range analysis and variance analysis.

[0065] In a preferred embodiment, better results can be obtained when the weights of the four aberrations are approximately 0.8, 0.6, 1, and 0.7, respectively.

[0066] Based on the optimal aberration weight combination, the optical simulation software ZEMAX is used to optimize the aberration correction results by combining default functions with special operands.

[0067] To analyze the angular measurement accuracy of the laser optical system of this invention under large field-of-view conditions, the normalized values ​​of the optical power received by the four-quadrant detector under different fields of view were simulated, and the relationship between the normalized values ​​and the incident angle was subjected to cubic fitting. Figure 3 The fitted curve function is y = -0.7187x³ + 0.0001x² + 13.506x - 0.00003. The normalized number of this optical system under different field-of-view conditions can be basically fitted to a straight line, meeting the linearity requirement. Analysis of the fitted error curve (...) Figure 4 It can be seen that the maximum angle error of the cubic term under the field of view conditions of -10° to 10° is only 0.048°, which can realize high-precision laser angle measurement with a large field of view.

[0068] In summary, the beneficial technical effects of this invention are reflected in:

[0069] 1. Within the limits of size, image quality, and manufacturing process, this optical system has the largest possible relative aperture to ensure high system sensitivity. It is also capable of detecting high-precision angular information of faint targets at long distances within a large field of view.

[0070] 2. The form and composition of this optical system make reasonable use of the photosensitive area, ensuring high uniformity and symmetry of the light spot within the field of view, which is conducive to giving full play to the efficiency of the detector.

[0071] 3. In general optical systems, the detector is mostly located behind the focal length, while in this optical system, the detector is located in front of the focal length, which effectively controls the lens size.

[0072] 4. This optical system uses only a single spherical lens, which effectively corrects system aberrations and controls lens manufacturing costs.

[0073] 5. It employs narrowband filtering, which provides good transmission performance for the operating band and strong suppression of background noise.

[0074] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without any creative effort.

[0075] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus necessary general-purpose hardware platforms, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solutions, in essence or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in the various embodiments or some parts of the embodiments.

[0076] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A large field-of-view, high-precision laser angle measurement system, characterized in that, include: An optical window (1) and an optical system disposed inside the optical window (1), the optical system comprising a filter (2), a lens (3) and a four-quadrant detector (4) arranged sequentially along the light input to output direction; the lens (3) is a spherical mirror, the filter (2) is a narrowband filter, the second surface of the filter and the lens (3) are used to correct system aberrations and chromatic aberrations, the air gap between the filter (2) and the lens (3) is 0.5 mm, and the aperture of the narrowband filter is 25 mm; A first surface faces the optical window (1), wherein an anti-reflection coating is deposited on the first surface to reduce reflection and scattering; And a second surface, on which a filter film is coated, for receiving target light signals and filtering out non-target light signals.

2. The large field-of-view high-precision laser angle measurement system as described in claim 1, characterized in that, include: The optical window (1) adopts a concentric circle structure, and the axes of the optical window (1), the filter (2) and the lens (3) are collinear.

3. The large field-of-view high-precision laser angle measurement system as described in claim 1, characterized in that, The optical system includes multiple optimized parameter features, including curvature variables, thickness variables, and air gap variables; The curvature variable includes the first surface radius of curvature and the second surface radius of curvature of the lens (3); The thickness variable is the thickness of the lens (3); The air gap variable includes the air thickness on the back surface of the filter (2) and the air thickness on the back surface of the lens (3).

4. The large field-of-view high-precision laser angle measurement system as described in claim 3, characterized in that, The thickness variable ranges from 0.5mm to 25mm, and the air gap variable ranges from 0.2mm to 25mm.

5. An aberration correction method for a large field-of-view high-precision laser goniometer system, employing the large field-of-view high-precision laser goniometer system as described in any one of claims 1-4, characterized in that, The method includes: Determine aberrations, wherein the aberrations include spherical aberration, coma, astigmatism, and distortion; The uniformity of the light spot is selected as a quality characteristic value, and the weighting parameters of each aberration are determined. The Taguchi method was used to optimize the aberration weight parameters, and the optimal combination of aberration weights for each aberration weight parameter was determined through range analysis and variance analysis. Based on the optimal aberration weight combination, the aberration correction result is obtained by using optical simulation software with a default function combined with a special operand method.

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