A system and method for measuring the radius of curvature of a spherical mirror

Abstract

The application discloses a kind of spherical mirror curvature radius measurement system and method.The method is:1) install spherical mirror on fixed support;2) install white screen, laser and camera on one-dimensional moving platform, connect one-dimensional moving platform, camera to data processing unit respectively;3) open laser and make its output light shine on white screen to form point light source, while adjusting camera alignment white screen;4) adjust the main shaft parallel of one-dimensional moving platform and spherical mirror, and make the main shaft pass through white screen;5) control moving one-dimensional moving platform by data processing unit, and utilize camera to photograph and record the size of light spot on white screen in moving process;6) data processing unit records each light spot size and its corresponding distance, and the distance of light spot minimum is obtained by fitting, namely the curvature radius of spherical mirror.The application is convenient to operate and easy to expand, and has high precision, improves measurement efficiency.

Description

Technical Field

[0001] This invention belongs to the field of measuring the radius of curvature of large-aperture spherical mirrors, and particularly relates to a system and method for measuring the radius of curvature of spherical mirrors. Background Technology

[0002] In recent years, the research and application of large-aperture observation equipment in my country has developed rapidly, involving the use of large-aperture reflectors. To reduce the difficulty of mirror manufacturing and improve resolution, large-aperture reflectors in observation equipment are assembled using modular spherical reflectors. This introduces a new problem: the assembly of large-aperture reflectors typically requires the completion of a large number of smaller reflectors. The quality of these smaller reflectors needs to be tested for their radius of curvature to determine whether they can be used in the subsequent assembly of the large-aperture reflector.

[0003] Traditional methods for measuring the radius of curvature of a reflector include interferometry and multi-point measurement. These methods require expensive equipment, consume a lot of time and manpower, and may even damage the surface of the reflector. Summary of the Invention

[0004] To address the aforementioned problems, this invention proposes a novel method for measuring the radius of curvature of a spherical mirror. This method not only automates and precisely measures the radius of curvature of a spherical mirror, improving measurement efficiency, but also uses simple instruments, reducing costs. In other words, the tools used in this invention are simple, easy to operate, and readily expandable, while also offering high accuracy.

[0005] The method for measuring the radius of curvature of a spherical reflecting mirror according to the present invention comprises the following steps:

[0006] 1. Mount the spherical reflector on the fixed bracket.

[0007] 2. Install a white screen, laser, and camera on a one-dimensional moving platform, and connect the one-dimensional moving platform and camera to the data processing unit respectively. The white screen is perpendicular to the main axis of the reflector. The laser and camera are best positioned on opposite sides of the main axis. The laser will generate a light spot on the white screen, and the reflector will also generate a light spot. The camera is aimed at the light spot reflected back from the reflector and recorded.

[0008] 3. Turn on the laser and let the light shine on the white screen to form a point light source, while the camera is pointed at the white screen.

[0009] 4. Adjust the main axis of the one-dimensional moving platform and the spherical reflector to be parallel and so that the main axis passes through the white screen.

[0010] 5. The data processing unit controls the movement of the one-dimensional moving platform. Based on the current and initial positions of the one-dimensional moving platform, the data processing unit calculates the distance between the platform and the spherical reflector. In actual operation, if the radius of curvature is R, the one-dimensional platform moves from a distance less than R, gradually increasing (i.e., moving further away from the reflector). The step size is related to the measurement accuracy; if high accuracy is required, the step size is shorter. Then, the platform moves to a distance greater than R between itself and the spherical reflector. During this movement, the light spot reflected back onto the white screen first decreases in size and then increases, reaching its minimum at the radius of curvature R.

[0011] 6. The camera takes pictures to record the changes in the size of the light spot on the spherical reflector.

[0012] 7. The data processing unit obtains the distance to the minimum point of the light spot by fitting the change in the light spot size and the corresponding distance, which is the radius of curvature of the spherical mirror.

[0013] This invention also provides a system for measuring the radius of curvature of a spherical reflector, characterized in that it includes a fixed bracket, a one-dimensional moving platform, a white screen, a laser, a camera, and a data processing unit; wherein,

[0014] The fixed bracket is used to install and fix the spherical reflector to be tested;

[0015] The white screen, laser, and camera are respectively mounted on the one-dimensional mobile platform, and the camera and the one-dimensional mobile platform are respectively connected to the data processing unit.

[0016] The one-dimensional moving platform is parallel to the main axis of the spherical reflector, and the main axis of the spherical reflector is perpendicular to the white screen;

[0017] The laser is used to output light to illuminate the white screen;

[0018] The white screen is used for diffuse reflection of incident light;

[0019] The spherical reflector is used to reflect the diffused light rays and converge them onto the white screen to form a light spot;

[0020] The camera is used to take pictures of the light spot and send them to the data processing unit;

[0021] The data processing unit is used to control the movement of the one-dimensional moving platform and to control the camera to take pictures and record the light spots; and to calculate the distance between the current one-dimensional moving platform and the spherical reflector based on the current position and the initial position of the one-dimensional moving platform, and then to fit the distance at the smallest point of the light spot according to the size of each light spot and its corresponding distance, which is the radius of curvature of the spherical reflector.

[0022] Furthermore, the laser and camera are symmetrically placed on both sides of the main axis of the spherical reflector.

[0023] Furthermore, the white screen is a diffuse reflective plate, graph paper, or white paper.

[0024] The advantages of this invention are as follows:

[0025] This invention enables the automated acquisition of the radius of curvature of a spherical reflector, achieving the measurement of the radius of curvature of a spherical reflector using a laser light source, camera, and laser. The method is automated, accurate, and efficient through image recognition and processing. Attached Figure Description

[0026] Figure 1 This invention relates to a system for measuring the radius of curvature of a spherical reflecting mirror.

[0027] Figure 2 This is the fitted curve.

[0028] Among them, 1-spherical reflector, 2-main axis of spherical reflector, 3-camera, 4-laser, 5-white screen, 6-one-dimensional moving platform, 7-data processing unit. Detailed Implementation

[0029] To better illustrate the invention and enable those skilled in the art to better understand the invention, the method for measuring the radius of curvature of a spherical reflector in the embodiments of the invention will be described in detail and completely below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the invention, and not all of them. Based on the embodiments of the invention, any other embodiments that can be obtained by those skilled in the art without creative effort should fall within the scope of protection of the invention.

[0030] The spherical mirror curvature radius measurement system of the present invention is as follows: Figure 1As shown, the spherical reflector 1 is fixed on a support with adjustable height and direction, and the support can adjust the direction of the spherical reflector. The camera 3, laser 4, and white screen 5 are fixed on a one-dimensional moving platform 6, which is connected to the data processing unit 7. The laser beam emitted by the laser 4 illuminates the white screen 5, forming an electric light source and producing diffuse reflection. The diffused light is received and reflected back by the spherical reflector 1, converging to form a light spot on the white screen 5. Simultaneously, the camera 3 is aligned with the white screen 5, and the initial laser source and the converging light spot cannot coincide. The spherical reflector 1 is adjusted so that its main axis is parallel to the moving axis of the one-dimensional moving platform 6, and the main axis 2 of the spherical reflector passes through the white screen 5. At this point, the point light source and the light spot reflected and converged by the spherical reflector 1 are seen on the white screen 5. The camera 3's field of view is aligned with the light spot for imaging. Data is transmitted to the data processing unit 7 via a cable, and the data processing unit 7 can emit signals to control the movement of the one-dimensional moving platform 6.

[0031] The white screen 5 can be a diffuse reflector, graph paper, or white paper. The movement of the one-dimensional moving platform 6 is automatically completed by the data processing unit program.

[0032] The images recorded by the camera are either black and white or color; the camera takes pictures automatically through the data processing unit program.

[0033] The data processing unit obtains the radius of curvature by fitting different spot sizes at different distances.

[0034] The data processing unit can be a computer.

[0035] The specific monitoring methods are as follows:

[0036] S1 mounts the spherical reflector on the fixed bracket;

[0037] S2 is equipped with a white screen, laser, and camera on a one-dimensional mobile platform and connected to the data processing unit;

[0038] S3 turns on the laser, and the light shines on the white screen to form a point light source, while the camera is pointed at the white screen;

[0039] S4 adjusts the main axis of the one-dimensional moving platform and the spherical reflector to be parallel and so that the main axis passes through the white screen;

[0040] S5 drives the one-dimensional moving platform through a data processing unit program control.

[0041] The S6 uses its camera to capture and record changes in the size of the light spot on the spherical reflector on the white screen.

[0042] S7 uses the change in the size of the light spot on the spherical mirror and the corresponding distance to fit the distance at the minimum point of the light spot, which is the radius of curvature of the spherical mirror.

[0043] The specific operating method is as follows:

[0044] In S1, the spherical mirror is mounted and fixed on the bracket. The bracket is required to be able to move up and down to adjust the pitch and azimuth angles of the spherical mirror, which will facilitate the subsequent adjustment of the optical axis.

[0045] In S2, a white screen, laser, and camera are installed on a one-dimensional moving platform. The laser and camera are generally located on both sides of the optical axis. The camera can cover most of the white screen area. Do not move the camera after installation.

[0046] When the laser beam in S3 hits the white screen, it will cause diffuse reflection, which is equivalent to a point light source. At this time, the point light source needs to be controlled to be relatively small, usually within 1mm, and its position needs to be in the paraxial region on the principal optical axis side of the spherical reflector, usually less than 10cm.

[0047] In S4, by adjusting the height and orientation of the spherical reflector, the principal optical axis is made parallel to the movement axis of the one-dimensional moving platform and passes through the white screen. A laser beam emitted by a laser placed on the one-dimensional platform hits the center of the spherical reflector and then returns along the same path, thus confirming that the principal axis of the reflector is parallel to the one-dimensional moving platform.

[0048] In S5, the control system of the one-dimensional moving platform is connected to the data processing unit. The data processing unit can control the movement of the platform by setting the movement settings, or by controlling the platform to move automatically according to a plan.

[0049] In S6, the data processing unit program operates the one-dimensional moving platform and the camera in conjunction. After the platform moves a certain distance, it stops, and then the camera takes a picture and records the size of the light spot on the white screen. Then, it moves a certain distance again and takes another picture. This process records a series of different distances and different light spots.

[0050] In S7, the light spot typically decreases and then increases with distance, and the point where the light spot is smallest is the radius of curvature of the spherical mirror; the fitting here is usually done using a parabolic function.

[0051] In practice, this invention has achieved excellent results through quadratic polynomial fitting; the distance at the lowest point of the parabolic function (the minimum value of the light spot) is the radius of curvature. For example... Figure 2 As shown, the vertical axis is the size of the light spot D, the horizontal axis is the distance S, and the distance at the smallest point of the light spot is the radius of curvature.

[0052] Although specific embodiments of the invention have been disclosed for illustrative purposes to aid in understanding and implementing the invention, those skilled in the art will understand that various substitutions, variations, and modifications are possible without departing from the spirit and scope of the invention and the appended claims. Therefore, the invention should not be limited to the content disclosed in the preferred embodiments, and the scope of protection claimed by the invention is defined by the claims.

Claims

1. A method for measuring the radius of curvature of a spherical reflecting mirror, comprising the following steps: 1) Mount the spherical reflector on the fixed bracket; 2) Install a white screen, a laser, and a camera on the one-dimensional mobile platform, and connect the one-dimensional mobile platform and the camera to the data processing unit respectively; 3) Turn on the laser and let its output light shine on the white screen to form a point light source, while adjusting the camera to be aimed at the white screen; 4) Adjust the one-dimensional moving platform to be parallel to the main axis of the spherical reflector, so that the main axis passes through the white screen. At this time, the light from the point light source diffusely reflected by the white screen is reflected by the spherical reflector and converges on the white screen to form a light spot; wherein, the initial light source and the converged light spot of the laser cannot coincide. 5) The data processing unit controls the movement of the one-dimensional moving platform and uses the camera to capture and record the size of the light spot on the white screen during the movement; wherein, the data processing unit calculates the distance between the current one-dimensional moving platform and the spherical reflector based on the current position and the initial position of the one-dimensional moving platform. 6) The data processing unit records the size of each light spot and its corresponding distance, and the distance at the smallest light spot is fitted to obtain the radius of curvature of the spherical reflector.

2. The method according to claim 1, characterized in that, The fixed bracket is a height- and direction-adjustable bracket used to adjust the height and orientation of the spherical reflector.

3. The method according to claim 2, characterized in that, The laser and camera are symmetrically placed on both sides of the main axis of the spherical reflector.

4. The method according to claim 1, 2, or 3, characterized in that, The white screen is a diffuse reflector, graph paper, or white paper.

5. The method according to claim 1, 2, or 3, characterized in that, The images recorded by the camera are either black and white or color images.

6. The method according to claim 1, 2, or 3, characterized in that, A laser beam output from a laser placed on the one-dimensional moving platform is incident on the center of the spherical reflector. If the laser beam returns along its original path, it is determined that the main axis of the reflector is parallel to the one-dimensional moving platform.

7. The method according to claim 1, characterized in that, The data processing unit is a computer.

8. A system for measuring the radius of curvature of a spherical reflector, characterized in that, It includes a fixed bracket, a one-dimensional moving platform, a white screen, a laser, a camera, and a data processing unit; among which, The fixed bracket is used to install and fix the spherical reflector to be tested; The white screen, laser, and camera are respectively mounted on the one-dimensional mobile platform, and the camera and the one-dimensional mobile platform are respectively connected to the data processing unit. The one-dimensional moving platform is parallel to the main axis of the spherical reflector, and the main axis of the spherical reflector is perpendicular to the white screen; The laser is used to output light to illuminate the white screen; The white screen is used for diffuse reflection of incident light; The spherical reflector is used to reflect and converge the diffused light rays onto the white screen to form a light spot; wherein the initial light source and the converged light spot of the laser cannot coincide. The camera is used to take pictures of the light spot and send them to the data processing unit; The data processing unit is used to control the movement of the one-dimensional moving platform and to control the camera to take pictures and record the light spots; and to calculate the distance between the current one-dimensional moving platform and the spherical reflector based on the current position and the initial position of the one-dimensional moving platform, and then to fit the distance at the smallest point of the light spot according to the size of each light spot and its corresponding distance, which is the radius of curvature of the spherical reflector.

9. The system according to claim 8, characterized in that, The laser and camera are symmetrically placed on both sides of the main axis of the spherical reflector.

10. The system according to claim 8, characterized in that, The white screen is a diffuse reflector, graph paper, or white paper.

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