Detection method and device for lens distortion and field curvature

Abstract

The invention relates to the technical field of lens detection, in particular to a lens distortion and field curvature detection mode, which comprises the following steps: S1, adjusting the magnification of a lens to a theoretical value; s2, projecting an image by the DMD chip and displaying a plurality of point locations on the image; s3, calculating to obtain the field curvature of the detection lens: adjusting the position of the detection camera to find the optimal focal plane of the plurality of point locations in the step S2, and obtaining a range value; and S4, calculating to obtain a distortion value of the detection lens: taking one point as a reference, moving the detection lens to mark position coordinates of a plurality of point positions, calculating a distance between two point positions at different positions, and comparing the distance with a theoretical value to obtain a distortion value at each view field position. The coordinate of each point is marked, the field curvature and the distortion value of the detection lens at the moment are directly calculated according to the coordinate of each point, and intermediate links are reduced through direct measurement and calculation, so that errors are reduced, and the detection efficiency is greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lens detection, and in particular to a method and device for detecting lens distortion and field curvature. Background Art

[0002] In modern optical imaging systems, the performance of the lens directly affects the quality of the image. Lens distortion and field curvature are two main optical defects that affect the quality of imaging. Lens distortion refers to the phenomenon that straight lines in the image become curves after imaging, which is usually divided into barrel distortion and pincushion distortion. This phenomenon will cause image distortion and affect the accuracy of the image, which is particularly important in applications such as precision measurement and scientific research.

[0003] Field curvature is another type of optical distortion, which manifests as the inconsistency between the image plane and the actual imaging plane. Specifically, field curvature will cause differences in image clarity and focus in different imaging areas, thus affecting the usability of the entire image. Especially in large field of view imaging systems, the field curvature problem is more prominent and difficult to solve by simple focus adjustment.

[0004] At present, the detection methods for lens distortion and field curvature mainly rely on laboratory testing, which usually requires the use of high-precision standard images and measurement tools. Although these methods can effectively detect distortion and field curvature, they are often complicated and time-consuming, and it is difficult to meet the needs of fast imaging equipment and real-time monitoring.

[0005] Therefore, the present application has developed a method and device for detecting lens distortion and field curvature to solve the problems existing in the prior art. Summary of the invention

[0006] The purpose of the present invention is to provide a method and device for detecting lens distortion and field curvature, so as to solve the problem of low accuracy and low efficiency in detecting field curvature and distortion in the prior art.

[0007] The technical solution of the present invention is: a method for detecting lens distortion and field curvature, comprising the following steps:

[0008] S1: Adjust the lens magnification to the theoretical value;

[0009] S2: The DMD chip projects an image and displays multiple points on the image;

[0010] S3: Calculate the field curvature of the detection lens: adjust the position of the detection camera to find the best focal plane of multiple points in step S2, and obtain the extreme difference value;

[0011] S4: Calculate the distortion value of the detection lens: take one point as a reference, move the detection lens to mark the position coordinates of multiple points, calculate the distance between two points at different positions, compare with the theoretical value, and obtain the distortion value at each field of view position.

[0012] Preferably, in step S2, by inputting parameters of the number, position, image size, distribution interval and distribution method of the points into the terminal system, the terminal system processes the different parameters to generate a static image.

[0013] Preferably, the required static image is manually drawn and sent to the DMD chip through the control board. After processing, the DMD chip converts the image into a signal that controls the state of each micromirror on the DMD chip, thereby controlling the tilt angle of each micromirror on the DMD chip to project the manually drawn image.

[0014] Preferably, in step S2, the DMD chip projects five points, which are respectively located at the four corners of the image frame and the center of the image. In step S4, the coordinates of the four corner points are marked with a detection camera based on the center point, and the distances between the four corner points and the center point are calculated respectively, compared with the theoretical value, and the distortion value is calculated.

[0015] Preferably, in step S2, the DMD chip projects nine points and distributes them on the image in a 3×3 matrix. In step S4, three groups of distances between two points on the image border in the horizontal direction are calculated, and the pairwise differences of the three groups of distances are calculated to obtain the range in the horizontal direction; three groups of distances between two points on the image border in the vertical and horizontal directions are calculated, and the pairwise differences of the three groups of distances are calculated to obtain the range in the vertical and horizontal directions.

[0016] Preferably, in step S2, the DMD chip evenly projects multiple points along the two diagonals of the image, moves the detection camera to the positions of the points at the four corners and the center of the image, adjusts the detection camera to move in the direction of the z-axis, finds the best focal plane of the five points, and calculates the extreme value of the five points in the z-axis direction.

[0017] Preferably, the detection camera is moved to mark the position coordinates of multiple points on two diagonals on the image, and the difference between the points along the corresponding diagonals and the center point is calculated based on the center point. The difference is compared with the theoretical value to obtain the distortion value of each field of view position.

[0018] A device for detecting lens distortion and field curvature, implemented by the lens distortion and field curvature detection method according to any one of claims 1 to 7, comprising:

[0019] A detection platform, wherein a three-axis moving device, a detection lens, a detection camera, a DMD chip and a control board are provided on the detection platform. The three-axis moving device is arranged on the detection platform and controls the detection camera thereon to move in three directions. The detection lens is arranged on the detection platform and corresponds to the position of the detection camera. The detection lens is fixed to the DMD chip so that the light projected by the DMD chip can be projected onto the detection camera through the detection lens. The DMD chip is electrically connected to the control board and can control the rotation direction of the micromirror on the DMD chip.

[0020] Compared with the prior art, the advantages of the present invention are:

[0021] (1) Multiple points are projected onto the image through the DMD chip, and the detection camera is controlled to move through a three-axis moving device to mark the coordinates of each point. The field curvature and distortion values ​​of the detection lens at this time are directly calculated based on the coordinates of each point. Direct measurement and calculation reduce the intermediate links, thereby reducing errors.

[0022] (2) The process of marking multiple points is relatively simple, and the number and location of the marking points can be flexibly selected, which is more convenient and can meet the testing needs of different scenarios;

[0023] (3) By marking multiple points and calculating the distance with a three-axis mobile device, the field curvature and distortion values ​​at different positions can be quickly obtained without manual adjustment, greatly increasing the detection efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0025] Figure 1 A flowchart of a method for detecting lens distortion and field curvature according to the present invention;

[0026] Figure 2 This is a schematic diagram of the structure of a device for lens distortion and field curvature detection according to the present invention;

[0027] Figure 3 Schematic diagram of different embodiments of the present invention.

[0028] Among them: 1. Detection platform; 2. Three-axis moving device; 3. Detection lens; 4. Detection camera; 5. DMD chip; 6. Control board. DETAILED DESCRIPTION

[0029] The present invention is further described in detail below in conjunction with specific embodiments:

[0030] like Figure 1-Figure 3 As shown, a method for detecting lens distortion and field curvature includes the following steps:

[0031] S1: Adjust the lens magnification to the theoretical value to ensure image clarity and quality, reduce the number of trial and error during shooting, and improve shooting efficiency.

[0032] S2: DMD chip 5 projects an image and displays multiple points on the image. DMD chip 5 is used as the core imaging device of the projector to convert digital signals into optical images for projection. DMD chip 5 is composed of thousands of tiny reflective micro-lenses, each of which can be tilted and rotated to control the reflection direction of light and generate an image. The operator inputs the number, position, image size, distribution interval and distribution method of the points into the terminal system according to the required image, so as to obtain a static image through the processing of the terminal system, and sends the static image to DMD chip 5 through control board 6. After processing, DMD chip 5 converts the image into a signal to control the state of each micro-mirror on DMD chip 5, and controls the tilt angle of each micro-mirror on DMD chip 5 to project the static image. By comparing the difference between the reference image and the ideal image, the field curvature and distortion value can be calculated. The DMD chip 5 technology can realize precise control of each micro-mirror, thereby ensuring the accuracy of the projected image, providing reliable reference data for the calculation of field curvature and distortion value, and improving the accuracy of calculation.

[0033] In another embodiment, the required static image is manually drawn on the terminal, and the static image is sent to the DMD chip 5 through the control board 6. After processing by the DMD chip 5, the image is converted into a signal for each micromirror, and the tilt angle of each micromirror is controlled to project the manually drawn image. Through manual drawing, key features in the image, such as lines, shapes, colors, etc., can be highlighted to make it easier to identify and analyze field curvature and distortion, and the manually drawn image can be quickly modified and updated.

[0034] S3: Calculate the field curvature of the detection lens 3: Use the three-axis moving device 2 to move the detection camera 4 in the z-axis direction, where the z-axis direction is perpendicular to the projection image plane. The detection camera 4 searches for the best focal planes at multiple points during the movement, records the z-axis coordinates of the best focal planes corresponding to each point, and calculates the extreme value, which is the field curvature of the image, avoiding errors that may be caused by indirect measurement. The extreme value is calculated based on the recorded z-axis coordinates, and the degree of field curvature can be accurately quantified. Compared with other methods based on image processing or simulation calculation, the method of calculating field curvature through extreme value provides more accurate field curvature information, and can comprehensively evaluate the field curvature of the entire image plane, which is applicable not only to the central area but also to the edge area, thereby providing more comprehensive field curvature information, and the process of calculating the extreme value is relatively simple and efficient, and the results can be obtained quickly, greatly improving the processing speed and calculation efficiency.

[0035] S4: Calculate the distortion value of the detection lens 3: take one point as a reference, move the detection lens 3 to mark the position coordinates of multiple points, calculate the distance between two points at different positions, and calculate the difference between the actual distance and the theoretical value, compare the difference with the theoretical value, and obtain the distortion value at each field of view position.

[0036] In one embodiment, the DMD chip 5 projects five points located at the four corners of the image frame and the center of the image. Taking the center as a reference, the three-axis moving device 2 drives the detection camera 4 to move and mark the coordinates of the four corner points. After obtaining the coordinates, the distances between the four points and the center point are calculated, and the differences between the calculated four distances and the theoretical values ​​are compared with the theoretical distances to obtain the distortion value.

[0037] In another embodiment, the DMD chip 5 projects nine points and distributes them on the image in a 3×3 matrix. In the horizontal direction, three groups of distances between two points on the image border are calculated, and the pairwise differences of the three groups of distances are calculated to obtain the range in the horizontal direction, which is the distortion value of the image in the horizontal direction. In the direction perpendicular to the horizontal direction, three groups of distances between two points on the image border are calculated, and the pairwise differences of the three groups of distances are calculated to obtain the range in the vertical and horizontal directions, which is the distortion value of the image in the direction perpendicular to the horizontal direction.

[0038] In other embodiments, the DMD chip 5 evenly projects multiple points along the two diagonals of the image, and the detection camera 4 is controlled to move and mark the position coordinates of multiple points on the two diagonals of the image through the three-axis moving device 2. The distance between the points along the corresponding diagonals and the center point is calculated based on the center point, and the difference between this distance and the theoretical distance is compared with the theoretical value to obtain the distortion value of each field of view position.

[0039] like Figure 2 As shown, based on a lens distortion and field curvature detection method, the present invention develops a device for lens distortion and field curvature detection, including: a detection platform 1, a three-axis moving device 2, a detection lens 3, a detection camera 4, a DMD chip 5 and a control board 6. The three-axis moving device 2 is arranged on the detection platform 1, and controls the detection camera 4 located thereon to move in three directions. The detection lens 3 is arranged on the detection platform 1 and corresponds to the position of the detection camera 4. The detection lens 3 is fixed to the DMD chip 5, so that the light projected by the DMD chip 5 can be projected onto the detection camera 4 through the detection lens 3. The DMD chip 5 is electrically connected to the control board 6, and can control the rotation direction of the micromirror on the DMD chip 5. The detection camera 4 is controlled to move in three mutually perpendicular directions on the detection platform 1 through the three-axis moving device 2, and points at different field of view positions are captured, and the coordinates of the points are fed back to calculate the distortion value.

[0040] The implementation principle of this embodiment:

[0041] When calculating the field curvature and distortion value of the detection lens 3, firstly, a static image is obtained by inputting the required parameters into the terminal system or manually drawing the static image, and the static image is sent to the DMD chip 5. After being processed, the DMD chip 5 controls the angle and direction of the micromirror through the control board 6 to realize the projection of the image. Then, the three-axis moving device 2 controls the movement of the detection camera 4 to obtain the best focal plane of multiple points on the image at this time, and calculates the extreme difference value, which is the field curvature. After finding the best focal plane, the three-axis moving device 2 drives the detection camera 4 to move and marks the coordinates of the points on the image. According to different actual needs, the three-axis moving device 2 is moved to capture different points, and the distance between two points on the image frame in the horizontal and vertical directions, or the distance between the points on the diagonal or the four corners and the center point is calculated, and the distortion values ​​at different positions are calculated. The field curvature and distortion values ​​of the detection lens are directly calculated through the coordinates of different points, without manual adjustment, which reduces errors and greatly increases the detection efficiency.

[0042] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with this technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the scope of protection of the present invention. For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is limited by the attached claims rather than the above description, and it is intended to include all changes within the meaning and scope of the equivalent elements of the claims in the present invention.

Claims

1. A method for detecting lens distortion and field curvature, characterized in that: The following steps are involved: S1: Adjust the lens magnification to the theoretical value; S2: The DMD chip (5) projects an image and displays multiple points on the image; S3: Calculate the field curvature of the detection lens (3): adjust the position of the detection camera (4) to find the best focal plane of multiple points in step S2, and obtain the extreme difference value; S4: Calculate the distortion value of the detection lens (3): take one point as a reference, move the detection lens (3) to mark the position coordinates of multiple points, calculate the distance between two points at different positions, compare with the theoretical value, and obtain the distortion value at each field of view position.

2. The method for detecting lens distortion and field curvature according to claim 1, characterized in that: In step S2, by inputting the number, position, image size, distribution interval and distribution method of the points into the terminal system, the terminal system processes the different parameters to generate a static image.

3. The method for detecting lens distortion and field curvature according to claim 2, characterized in that: The required static image is manually drawn and sent to the DMD chip (5) through a control board (6). After processing, the DMD chip (5) converts the image into a signal for controlling the state of each micromirror on the DMD chip (5), thereby controlling the tilt angle of each micromirror on the DMD chip (5) to project the manually drawn image.

4. The method for detecting lens distortion and field curvature according to claim 1, characterized in that: In step S2, the DMD chip (5) projects five points, which are located at the four corners of the image frame and the center of the image. In step S4, the coordinates of the four corner points are marked with a detection camera (4) based on the center point, and the distances between the four corner points and the center point are calculated respectively, compared with the theoretical value, and the distortion value is calculated.

5. The method for detecting lens distortion and field curvature according to claim 1, characterized in that: In step S2, the DMD chip (5) projects nine points and distributes them on the image in a 3×3 matrix. In step S4, three sets of distances between two points on the image border in the horizontal direction are calculated, and the pairwise differences of the three sets of distances are calculated to obtain the range in the horizontal direction. Calculate the distances between two points on the image border in three groups in the vertical and horizontal directions, and calculate the pairwise differences of the three groups of distances to obtain the vertical and horizontal extremes.

6. The method for detecting lens distortion and field curvature according to claim 1, characterized in that: In step S2, the DMD chip (5) evenly projects multiple points along the two diagonals of the image, moves the detection camera (4) to the positions of the points located at the four corners and the center of the image, adjusts the detection camera (4) to move in the direction of the z-axis, finds the best focal plane of the five points, and calculates the extreme difference values ​​of the five points in the z-axis direction.

7. The method for detecting lens distortion and field curvature according to claim 6, characterized in that: The detection camera (4) is moved to mark the position coordinates of multiple points on two diagonal lines on the image, and the difference between the points along the corresponding diagonal lines and the center point is calculated based on the center point. The difference is compared with the theoretical value to obtain the distortion value of each field of view position.

8. A device for detecting lens distortion and field curvature, implemented by the lens distortion and field curvature detection method according to any one of claims 1 to 7, characterized in that: include: A detection platform (1) is provided on the detection platform (1) with a three-axis moving device (2), a detection lens (3), a detection camera (4), a DMD chip (5) and a control board (6); the three-axis moving device (2) is arranged on the detection platform (1) and controls the detection camera (4) located thereon to move in three directions; the detection lens (3) is arranged on the detection platform (1) and corresponds to the position of the detection camera (4); the detection lens (3) and the DMD chip (5) are fixed to each other so that light projected by the DMD chip (5) can be projected onto the detection camera (4) through the detection lens (3); the DMD chip (5) and the control board (6) are electrically connected and can control the rotation direction of the micromirror on the DMD chip (5).

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