Large-view-field high-precision laser angle measurement system

Abstract

The invention discloses a large-view-field high-precision laser angle measurement system, and belongs to the technical field of large-view-field laser angle measurement. The large-view-field high-precision laser angle measurement system comprises an optical window and an optical system arranged in the optical window; the system comprises an optical filter, a lens and a four-quadrant detector which are sequentially arranged in the direction from light input to light output. The lens is a spherical mirror, and the optical filter is a narrow-band optical filter. The optical system has a relative aperture as large as possible within the permissible range of size, image quality and processing technology so as to ensure that the system has high sensitivity. And long-distance high-precision weak target angle information can be detected in a large field of view. According to the invention, the photosensitive area is reasonably utilized, the high uniformity and symmetry of light spots in the field of view are ensured, the efficiency of the detector is brought into full play, meanwhile, only the single spherical lens is adopted, the system aberration is effectively corrected, and the processing cost of the lens is controlled.

Description

Technical Field

[0001] The present application relates to the technical field of laser angle measurement under a large field of view, and more specifically, to a large field of view and high-precision laser angle measurement system. Background Art

[0002] The laser angle measurement optical system mainly receives the laser diffusely reflected by the target to 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, there will be differences in the current signals generated by the four quadrants. By performing sum and difference operations on the output signals of each quadrant, the position deviation information of the target can be obtained.

[0003] The commonly used angle measurement laser optical system is limited by the field of view conditions. On the one hand, the angle range that can be measured under high-precision conditions is small, with a maximum of only ±2°. On the other hand, under the condition of a large field of view, it is affected by aberrations and cannot achieve high-precision angle measurement. In the actual angle measurement process, due to the weak diffuse reflection echo signal, more optical lenses are required for focusing, which will lead to a larger system size and excessive weight. Although the use of aspheric lenses can reduce the number of lenses, the processing cost is high, which seriously affects the size, weight and cost of the entire angle measurement system. Summary of the invention

[0004] In response to at least one defect or improvement need in the prior art, the present invention provides a large-field-of-view and high-precision laser angle measurement system, which uses only a single spherical lens to correct system errors based on a four-quadrant detector, thereby realizing a laser angle measurement lens optical system with a simple and compact structure, small size, light weight and low cost.

[0005] To achieve the above-mentioned purpose, according to the first aspect of the present invention, there is provided a large-field-of-view high-precision laser angle measurement system, comprising: an optical window 1 and an optical system arranged inside the optical window 1, the optical system comprising a filter 2, a lens 3 and a four-quadrant detector 4 arranged in sequence along the direction from light input to output; the lens 3 is a spherical mirror, and the filter 2 is a narrow-band filter.

[0006] The large-field-of-view high-precision laser angle measurement system comprises: the filter comprises:

[0007] A first surface faces the optical window 1, wherein the first surface is coated with an anti-reflection film for reducing reflection and scattering; and a second surface is coated with a filter film for receiving target light signals and filtering out non-target light signals.

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

[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 spacing distance 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 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 a plurality of optimized parameter features, wherein the optimized parameter features include a curvature variable, a thickness variable, and an air spacing variable;

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

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

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

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

[0017] According to a second aspect of the present invention, there is also provided an aberration correction method for a large-field-of-view high-precision laser angle measurement system, using any of the large-field-of-view high-precision laser angle measurement systems described above, the method comprising:

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

[0019] The uniformity of the light spot is selected as the quality characteristic value, and each aberration weight parameter is determined;

[0020] The aberration weight parameters are optimized by using the Taguchi method, and the optimal aberration weight combination of each aberration weight parameter is determined by using range analysis and variance analysis;

[0021] According to the optimal aberration weight combination, the optical simulation software is used to optimize by taking the default function combined with the special operand method to obtain the aberration correction result.

[0022] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0023] The large-field-of-view high-precision laser angle measurement system comprises an optical window 1 and an optical system arranged inside the optical window 1. The system comprises a filter 2, a lens 3 and a four-quadrant detector 4 arranged in sequence along the direction from light input to light output; the lens 3 is a spherical mirror, and the filter 2 is a narrow-band filter. The optical system has a relative aperture as large as possible within the permitted range of size, image quality and processing technology to ensure that the system has high sensitivity. And it can meet the requirements of detecting the angle information of weak targets at a long distance and with high precision under a large field of view. At the same time, the form and composition of the optical system reasonably utilize the photosensitive area, ensure the high uniformity and symmetry of the light spot in the field of view, and facilitate giving full play to the efficiency of the detector. In addition, the detectors of general optical systems are mostly located after the focus, while the detectors of the optical system are located before the focus, which effectively controls the size of the lens. The optical system of the present invention only uses a single spherical lens, which effectively corrects the system aberration and controls the processing cost of the lens. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

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

[0026] Figure 2 A schematic diagram of the principle of a four-quadrant detector provided in an embodiment of the present application;

[0027] Figure 3 A schematic diagram of the analysis results of normalized numbers of different fields of view is provided for the embodiment of the present application;

[0028] Figure 4 This is a schematic diagram of the fitting error analysis curve provided in an embodiment of the present application. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with 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 intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present 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 and claims of this application and the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally includes steps or units that are not listed, or optionally includes other steps or units inherent to these processes, methods, products or devices.

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

[0032] See also Figure 1 A large-field-of-view high-precision laser angle measurement system comprises: an optical window 1 and an optical system arranged inside the optical window 1, wherein the optical system comprises a filter 2, a lens 3 and a four-quadrant detector 4 arranged in sequence along the direction from light input to light output; the lens 3 is a spherical mirror, and the filter 2 is a narrow-band filter.

[0033] The 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 band, and the window has a protective effect.

[0034] The filter comprises: a first surface facing the optical window 1, wherein the first surface is coated with an anti-reflection film for reducing reflection and scattering; and a second surface, wherein the second surface is coated with a filter film for receiving target light signals and filtering out non-target light signals.

[0035] In one embodiment, the 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 laser angle measurement under a large field of view, the front surface can be coated with an anti-reflection film and the rear surface can be coated with a filter film.

[0036] The present invention adopts the means of narrow-band filtering, has good penetration performance for the working band, and has strong suppression ability for background noise.

[0037] The present invention adopts a single spherical lens to correct system aberrations instead of an aspherical lens while meeting the requirements of high light flux and laser spot quality, thereby effectively controlling the processing cost.

[0038] The four-quadrant detector 4 is composed of four photosensitive surfaces with the same performance. Figure 2The schematic diagram of the principle of the four-quadrant detector is shown schematically. The echo signal reflected by the target passes through the front optical system and irradiates the four-quadrant detector, generating current signals in the four quadrants (1, 2, 3, 4), and the current intensity is proportional to the light receiving area.

[0039] Figure 2 The outer circle in the middle represents the four-quadrant detector, and the inner circle shaded part in the figure represents the laser spot formed by the echo signal. When the spot moves on the four-quadrant detector, the light receiving area of ​​each quadrant will change, causing the current intensity generated in the four quadrants to change. After the current change of each quadrant is converted from current to voltage and analog-to-digital conversion (A / D conversion), data processing can be performed to calculate the displacement (x, y) of the center of the spot relative to the center of the four-quadrant detector.

[0040] The laser angle measurement system uses a four-quadrant detector as a receiving device. The diffusely scattered laser forms a spot on the four-quadrant detector to output angle information. In order to measure the distribution of laser energy in the four quadrants, the laser energy spot is required to have a certain area on the four-quadrant detector, and the spot symmetry and uniformity are good.

[0041] The optical system of the present invention includes a plurality of optimized parameter features, wherein the optimized parameter features include a curvature variable, a thickness variable and an air spacing variable;

[0042] Curvature variables, including a first surface curvature radius and a second surface curvature radius of the lens 3;

[0043] Thickness variable, which is the thickness of the lens 3;

[0044] The air spacing variables include the air thickness on the rear surface of the filter 2 and the air thickness on the rear 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 less than 100 commonly used optical materials, and the applicable temperature range, processing difficulty, cost, light transmittance, etc. of the materials need to be controlled during optimization.

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

[0047] A large-field-of-view high-precision laser angle measurement system comprises: an optical window 1 and an optical system arranged inside the optical window 1, wherein the optical system comprises a filter 2, a lens 3 and a four-quadrant detector 4 arranged in sequence along the direction from light input to light output; the lens 3 is a spherical mirror, and the filter 2 is a narrow-band filter.

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

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

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

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

[0052] 1. Effective 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] The front and back surfaces of the optical window, the front surface of the narrow-band filter, and the front and back surfaces of the spherical lens are all coated with anti-reflection films, and the overall transmittance of the optical system reaches more than 90%.

[0057] The present invention also provides an aberration correction method for a large-field-of-view high-precision laser angle measurement system, and the method using the large-field-of-view high-precision laser angle measurement system comprises:

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

[0059] The uniformity of the light spot is selected as the quality characteristic value, and each aberration weight parameter is determined;

[0060] The aberration weight parameters are optimized by using the Taguchi method, and the optimal aberration weight combination of each aberration weight parameter is determined by using range analysis and variance analysis;

[0061] According to the optimal aberration weight combination, the optical simulation software is used to optimize by taking the default function combined with the special operand method to obtain the aberration correction result.

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

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

[0064] In order to improve the design quality, the influence of basic aberrations on spot uniformity was analyzed by applying the Taguchi method. The error factor level was formulated according to professional knowledge and a lot of design experience. The spot uniformity was selected as the quality characteristic value. The parameters of each aberration weight were optimized by the Taguchi method. 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] According to the best aberration weight combination, the optical simulation software ZEMAX is used to optimize the aberration correction result by combining the default function with special operands.

[0067] In order to analyze the angle measurement accuracy of the laser optical system of the present invention under the condition of large field of view, the normalized number of the optical power received by the four-quadrant detector under different fields of view was simulated, and the relationship between the normalized number and the incident angle was fitted three times ( Figure 3 ), the fitting curve function is y = -0.7187x3 + 0.0001x2 + 13.506x-0.00003. The normalized number of this optical system under different field conditions can basically be fitted into a straight line and meet the linear requirements. By analyzing the fitting error curve ( Figure 4 ), it can be seen that the maximum angle error of the cubic term under the field of view of -10° to 10° is only 0.048°, which can achieve high-precision laser angle measurement in a large field of view.

[0068] In summary, the beneficial technical effects of the present invention are embodied in:

[0069] 1. The optical system has the largest possible relative aperture within the permitted range of size, image quality and processing technology to ensure the system has high sensitivity. It can also detect the angle information of weak targets at long distances and with high precision under a large field of view.

[0070] 2. The form and composition of the optical system make rational 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 effectiveness of the detector.

[0071] 3. The detectors of general optical systems are mostly located after the focus, while the detector of this optical system is located before the focus, which effectively controls the lens size.

[0072] 4. The optical system uses only a single spherical lens, which effectively corrects the system aberration and controls the processing cost of the lens.

[0073] 5. The narrow-band filtering method is adopted, which has good transmittance performance for the working band and strong suppression ability for background noise.

[0074] The device embodiments described above are merely illustrative, wherein the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment. Ordinary technicians in this field can understand and implement it without paying creative labor.

[0075] Through the description of the above implementation methods, those skilled in the art can clearly understand that each implementation method can be implemented by means of software plus a necessary general hardware platform, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solution is essentially or the part that contributes to the prior art can be embodied in the form of a software product, and the computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a disk, an optical disk, etc., including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment 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, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high-precision laser angle measurement system with a large field of view, characterized in that: include: An optical window (1) and an optical system arranged inside the optical window (1), wherein the optical system comprises a filter (2), a lens (3) and a four-quadrant detector (4) arranged in sequence along the direction from light input to light output; the lens (3) is a spherical mirror, and the filter (2) is a narrow-band filter.

2. The large-field-of-view high-precision laser angle measurement system according to claim 1, characterized in that: include: The filter comprises: A first surface faces the optical window (1), wherein the first surface is coated with an anti-reflection film for reducing reflection and scattering; and a second surface is coated with a filter film for receiving target light signals and filtering out non-target light signals.

3. The large-field-of-view high-precision laser angle measurement system according to 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.

4. The large-field-of-view high-precision laser angle measurement system according to claim 1, characterized in that: include: The air spacing distance between the filter (2) and the lens (3) is 0.5 mm, and the aperture of the narrow-band filter is 25 mm.

5. The large-field-of-view high-precision laser angle measurement system according to claim 1, characterized in that: include: The second surface of the filter and the lens (3) are used to correct system aberrations and / or chromatic aberrations.

6. The large-field-of-view high-precision laser angle measurement system according to claim 1, characterized in that: The optical system includes a plurality of optimized parameter features, wherein the optimized parameter features include a curvature variable, a thickness variable, and an air spacing variable; The curvature variable comprises a first surface curvature radius and a second surface curvature radius of the lens (3); The thickness variable is the thickness of the lens (3); The air spacing variable includes the air thickness of the rear surface of the filter (2) and the air thickness of the rear surface of the lens (3).

7. The large-field-of-view high-precision laser angle measurement system according to claim 6, characterized in that: The thickness variable ranges from 0.5 mm to 25 mm, and the air gap variable ranges from 0.2 mm to 25 mm.

8. A method for correcting the aberration of a large-field-of-view high-precision laser angle measurement system, using the large-field-of-view high-precision laser angle measurement system according to any one of claims 1 to 7, characterized in that: The method comprises: Determining aberrations, wherein the aberrations include spherical aberration, coma, astigmatism, and distortion; The uniformity of the light spot is selected as the quality characteristic value, and each aberration weight parameter is determined; The aberration weight parameters are optimized by using the Taguchi method, and the optimal aberration weight combination of each aberration weight parameter is determined by using range analysis and variance analysis; According to the optimal aberration weight combination, the optical simulation software is used to optimize by taking the default function combined with the special operand method to obtain the aberration correction result.

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