Optical test system with automatic centering function and automatic centering method

Abstract

The invention relates to an optical automatic centering method, aims to solve the technical problems that an existing cross-core positioning method is low in working efficiency and cannot meet the high image quality requirement of optical system testing, and provides an optical testing system with an automatic centering function and an automatic centering method. The method comprises the following steps: presetting parameters of a to-be-detected lens, controlling an electric control turntable to rotate to drive the to-be-detected lens to rotate to two contrast view fields, and performing automatic focus scanning at the two contrast view fields by using a microscopic detection system to obtain image quality parameters or other reference parameters of different image surfaces of the to-be-detected lens at the two contrast view fields; the included angle between the optical axis of the to-be-measured lens and the optical axis of the light source system is calculated, and the included angle is eliminated by rotating the high-precision rotating table, thereby realizing automatic centering.

Description

Technical Field

[0001] The invention relates to an optical automatic centering method, and in particular to an optical testing system with an automatic centering function and the automatic centering method. Background Art

[0002] In the field of optical lens testing, for some optical lenses with high image quality requirements, it is necessary to test the image quality-related indicators within their full field of view. During the test, if the optical axis of the optical lens is not parallel to the optical axis of the testing equipment, the test data will be asymmetric and thus unable to reflect the true condition of the optical lens. Therefore, before testing the optical system, in order to make the optical axis of the optical lens parallel to that of the testing equipment, it often takes a lot of time to perform through-center positioning.

[0003] Currently, the common through-hole positioning methods include the minimum trajectory circle method, the reference mirror optical axis method, the reference plane optical axis method and the image quality approximation method; the minimum trajectory circle method and the reference mirror optical axis method are only applicable to lens testing with a reference mirror; the reference plane optical axis method requires human observation, resulting in accuracy depending on the observation and judgment of the tester; the image quality approximation method determines the position of the optical axis by comparing the image quality at the symmetrical field of view of the lens under test, and then adjusting the posture of the lens under test by the approximation method until the image quality parameters at the compared field of view are consistent. Although this method is simple, it is not suitable for lenses with a large depth of focus, and since the approximation method is used for adjustment, the test efficiency is more dependent on the experience of the tester and is difficult to promote on a large scale; therefore, the existing through-hole positioning method is not only inefficient, but also cannot meet the high image quality requirements of optical system testing. Summary of the Invention

[0004] The purpose of the present invention is to solve the technical problems that the existing through-center positioning method has low working efficiency and cannot meet the high image quality requirements of optical system testing, and to provide an optical testing system and automatic centering method with automatic centering function.

[0005] To achieve the above objectives, the present invention provides the following technical solutions:

[0006] An optical testing system with automatic centering function, characterized by:

[0007] It includes a testing unit, an optical lens centering adjustment unit and a control processing unit;

[0008] The test unit includes a light source system and an electrically controlled turntable located in front of the light outlet of the light source system. A three-dimensional electrically controlled translation stage and a microscopic detection system are sequentially arranged on the top of the electrically controlled turntable from bottom to top. The three-dimensional electrically controlled translation stage is an orthogonal combination of electrically controlled translation stages that can translate forward and backward, left and right, and up and down along the optical axis of the light source system.

[0009] The optical lens centering adjustment unit is arranged on the electric-controlled turntable and is located between the light source system and the microscopic detection system. It includes a turntable and an optical lens fixture arranged on the turntable. The turntable is an electric-controlled turntable with adjustable rotation angle and pitch direction. The optical lens fixture is used to clamp the lens to be tested.

[0010] The control processing unit is electrically connected to the electric-controlled turntable, the three-dimensional electric-controlled translation stage, the rotation stage and the microscopic detection system respectively, and is used for performing rotation and translation control, data acquisition and image processing and analysis.

[0011] Furthermore, the light source system includes a light source and a collimator.

[0012] Furthermore, the microscopic detection system includes a microscope objective lens and an image acquisition unit, and the image acquisition unit adopts CCD or CMOS.

[0013] An automatic centering method, characterized by comprising the following steps:

[0014] S1: preparing an optical testing system with automatic centering function as described in any one of the above items;

[0015] S2: Set the basic parameters of the reference points required for automatic centering, including the imaging relationship of the lens to be tested, focal length, field of view, magnification of the microscopic detection system, and pixel size of the image acquisition unit;

[0016] S3: Select one of the following parameters: diffuse spot diameter, MTF, and mounting reference plane as the comparison parameter based on the type of lens to be tested, and set the corresponding comparison field of view, focus range, and number of focus sampling points.

[0017] S4: Clamp the lens to be tested using the optical lens fixture;

[0018] S5: manually controlling the electric-controlled turntable so that the object side of the lens to be tested faces the light outlet of the light source system, then controlling the three-dimensional electric-controlled translation stage to move the working surface of the microscope detection system to the target image plane, collecting the comparison parameters of the lens to be tested in real time through the image acquisition unit, and setting all the values ​​of the electric-controlled turntable and the three-dimensional electric-controlled translation stage to zero;

[0019] S6: Using a microscopic detection system to collect relevant contrast parameters of the lens under test in the contrast field of view, the control processing unit calculates the angle Δα between the optical axis of the lens under test and the optical axis of the light source system based on the relevant contrast parameters in the contrast field of view and the parameters set in steps S2 and S3;

[0020] S7: Using the control processing unit to determine whether the angle Δα is less than a preset value, if so, completing the automatic alignment of the optical system for testing; if not, executing step S8; the preset value is considered to be a value of the angle Δα close to 0;

[0021] S8: Use the control processing unit to determine the direction of the angle Δα, and adjust the rotation stage in the opposite direction to make the angle consistent with the angle Δα, and then return to step S6 until the angle Δα is at a preset value.

[0022] Furthermore, in step S3, one of the diffuse spot diameter, MTF, and mounting reference plane is selected as a comparison parameter according to the type of the lens to be tested, specifically:

[0023] For energy detection lenses, the diffuse spot diameter is selected as the comparison parameter, and the diffuse spot diameter for energy concentration and contrast field of view is set;

[0024] When selecting MTF for imaging detection lenses, you need to set the Nyquist frequency;

[0025] All types of lenses can choose the installation reference surface. The premise of selection is that the installation reference surface is processed to be perpendicular to the optical axis of the light source system during assembly, and no other parameters need to be set.

[0026] Furthermore, in step S3, the corresponding contrast field is set as follows:

[0027] When the contrast parameter is selected as diffuse spot diameter or MTF, the contrast field of view is set between ±0.7 and ±1.0 of the normalized field of view of the lens to be tested;

[0028] When selecting the mounting reference plane for comparison parameters, the comparison field of view is set at two symmetrical positions ±Y on the mounting reference plane that are as far away from the optical axis of the lens to be tested as possible, with the optical axis of the lens to be tested as the center. Y is the distance between the comparison field of view and the optical axis of the light source system.

[0029] Furthermore, in step S2, the focus sweep range and the number of focus sweep sampling points are set as follows:

[0030] In step S3, the method for setting the focus scanning range and the number of focus scanning sampling points is as follows:

[0031] The front-rear range ΔL of the movement of the microscopic detection system along the optical axis of the light source system is set as the focus range, and the number of focus sampling points n is set within the focus range, where n ≥ 10. The purpose is to fit a focus curve based on the selected contrast parameters within the set focus range through sampling point calculation, and one curve is generated at each of the two set contrast fields of view.

[0032] Furthermore, step S6 is specifically as follows:

[0033] The contrast parameter is selected as the diffuse spot diameter or MTF. According to the parameters set in steps S2 and S3, the electric-controlled turntable is rotated to the contrast field angle θ. At the same time, the three-dimensional electric-controlled translation stage is moved left and right along the optical axis of the light source system to the corresponding line field y. The movement component is:

[0034] θ = C·ω, where C is the normalized parameter of the contrast field of view, and ω is the half field angle of the lens to be tested;

[0035] y = ftanθ, which is the linear field of view of a general imaging lens, and f is the focal length of the lens to be tested; or, y = fθ, which is the linear field of view of a fisheye lens;

[0036] At this position, the diffuse spot diameter or MTF of the lens under test is collected by the microscopic detection system and the test data is given in real time. Then, the diffuse spot diameter or MTF of the lens under test is automatically scanned based on the focus range ΔL and the number of focus sampling points n. After completion, the information of the discrete focus sampling points is fitted into a focus curve. Then, the electric-controlled turntable and the three-dimensional electric-controlled translation stage are moved in the opposite direction to another comparison field of view and the focus is scanned again to obtain the focus curve at the position of the other comparison field of view.

[0037] The angle Δα between the optical axis of the lens to be tested and the optical axis of the light source system is calculated based on the focus difference at the two comparison fields and the moving distance of the three-dimensional electric-controlled translation stage to the two comparison fields.

[0038] Furthermore, step S6 is specifically as follows:

[0039] Compare the parameters and select the installation reference surface. According to the set basic parameters, move the three-dimensional electric-controlled translation stage to the Y position along the left and right directions of the optical axis of the light source system. At this position, the microscopic detection system collects the installation reference surface of the lens to be tested and displays the image of the installation reference surface in real time.

[0040] At this position, the mounting reference surface of the lens to be tested is automatically scanned based on the focus range ΔL and the number of focus sampling points n. After completion, the information of the discrete focus sampling points is fitted into a focus curve. The three-dimensional electric-controlled translation stage then moves in the opposite direction to another comparison field of view and performs focus scanning again to obtain the focus curve at the position of the other comparison field of view.

[0041] The angle Δα between the optical axis of the lens to be tested and the optical axis of the light source system is calculated based on the focus difference at the two comparison fields and the moving distance of the three-dimensional electric-controlled translation stage to the two comparison fields.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] (1) The automatic centering method of the present invention presets the parameters of the lens to be tested, controls the rotation of the electric control turntable to drive the lens to be tested to two contrasting fields of view, and then uses the microscopic detection system to automatically scan the focus at the two contrasting fields of view to obtain the image quality parameters or other reference parameters of different image planes of the lens to be tested at the two contrasting fields of view, and then calculates the angle between the optical axis of the lens to be tested and the optical axis of the light source system, and eliminates the angle by rotating the turntable. That is, the method of the present invention utilizes the algorithm and hardware control to cooperate with each other, can achieve high-precision positioning, realizes the purpose of automatic centering, and has excellent flexibility;

[0044] (2) The automatic centering method of the present invention has a wide range of applications and is not affected by the size of the lens to be tested. In addition, the centering adjustment accuracy of this method relies on image quality slice fitting, which is higher than that of existing adjustment methods.

[0045] (3) The automatic centering method of the present invention realizes automatic centering adjustment after presetting the parameters of the lens to be tested, thereby improving the efficiency of optical system testing and is not affected by the experience and level of the tester. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is a flow chart of an automatic centering method according to an embodiment of the present invention;

[0047] Figure 2 Schematic diagram of the overall structure of an optical testing system with automatic centering function in an embodiment of the present invention.

[0048] In the figure: 1-light source system, 2-electrically controlled turntable, 3-three-dimensional electrically controlled translation stage, 4-microscope detection system, 5-rotating stage, 6-optical lens fixture, 7-control processing unit. DETAILED DESCRIPTION

[0049] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0050] An optical testing system includes a light source system 1, an optical lens fixture 6, a microscopic detection system 4 and a control processing unit 7. In order to achieve the purpose of automatic centering, this embodiment provides an automatic centering method, which requires an optical testing system with an automatic centering function. Figure 2 As shown, the light source system 1 includes a light source and a collimator, and the system is equipped with a rotating table 5, an electric-controlled rotating table 2 and a three-dimensional electric-controlled translation table 3 on the basis of the optical system test system. The accuracy of the rotating table 5 is higher than 0.001 degrees.

[0051] Among them, the electric-controlled turntable 2 is arranged in front of the light outlet of the parallel light tube, and a rotating table 5 and a three-dimensional electric-controlled translation stage 3 are arranged on the electric-controlled turntable 2 in sequence along the direction of the light outlet of the parallel light tube, that is, the direction of the optical axis of the test equipment. The optical lens fixture 6 is arranged on the rotating table 5, and the rotating table 5 is an electric-controlled turntable with adjustable rotation angle and pitch direction. The optical lens fixture 6 is used to clamp the lens to be tested. A microscopic detection system is arranged on the three-dimensional electric-controlled translation stage. The three-dimensional electric-controlled translation stage 3 is an orthogonal combination of electric-controlled translation stages that can be translated forward and backward, left and right, and up and down along the optical axis. The axis angles of the three translation directions are all 90°. The microscopic detection system 4 includes a microscope objective lens and an image acquisition unit such as CCD or CMOS, and the control processing unit 7 includes a computer, various hardware controllers and control processing software, which are electrically connected to the electric-controlled turntable 2, the rotating table 5, the three-dimensional electric-controlled translation stage 3 and the microscopic detection system 4 respectively, for data acquisition, rotation and translation control, and image processing and analysis.

[0052] See attached Figure 1 As shown, the specific steps of an automatic centering method provided in this embodiment are as follows:

[0053] S1: Set the basic parameters of the lens to be tested

[0054] The basic parameters of the reference points required for automatic centering are determined based on the imaging relationship, focal length, field of view angle, magnification of the microscopic detection system, pixel size of the image acquisition unit, etc. of the lens to be tested.

[0055] S2: Set the automatic centering parameters

[0056] a. Select a comparison parameter based on the usage status of the lens to be tested:

[0057] ① For energy detection lenses, the diffuse spot diameter is selected as the comparison parameter. The diffuse spot diameter for energy concentration and contrast field comparison needs to be set.

[0058] ② When selecting MTF for imaging detection lenses, you need to set the Nyquist frequency;

[0059] ③ All lenses can select the installation reference surface, provided that the installation reference surface is perpendicular to the optical axis of the test equipment through processing during assembly. No other parameters need to be set. By default, the contrast microscopic detection system 4 pairs of installation reference surface surfaces are clearly imaged.

[0060] b. Select the corresponding contrast field according to the contrast parameters:

[0061] ① When the comparison parameter is selected as diffuse spot diameter or MTF, the comparison field of view should be selected between ±0.7 and ±1.0 of the normalized field of view of the lens to be tested;

[0062] ② When selecting the installation reference plane for comparison parameters, the comparison field of view is centered on the optical axis of the lens to be tested and at two symmetrical positions ±Y on the installation reference plane that are as far away from the optical axis of the lens to be tested as possible.

[0063] c. Set the focus sweep range and focus sweep points:

[0064] The front-rear range ΔL of the microscopic detection system 4 moving along the optical axis of the test device via the three-dimensional electric-controlled translation stage 3 is set as the focus range, and the number of focus sampling points within the focus range is set to n. The purpose is to fit the focus curve based on the above comparison parameters within the set focus range through sampling calculation. The curve is generated at each of the two set comparison fields:

[0065] ① When the contrast parameter is the diffuse spot diameter, the focus sweep curve is the curve of the diffuse spot diameter change at different image planes;

[0066] ② When the comparison parameter is MTF, the focus sweep curve is the MTF value at different image planes;

[0067] ③ When the comparison parameter is the installation reference surface, the focus curve is the clarity at different image planes.

[0068] S3: Use the optical lens fixture to clamp the lens to be tested and install the equipment components

[0069] Mount the lens to be tested on the optical lens fixture 6, with the object side of the lens to be tested facing the collimator, and visually adjust so that the optical axis of the lens is roughly parallel to the optical axis of the collimator;

[0070] Select a suitable microscope objective lens according to the relative aperture of the optical system to be measured and install it on the microscope detection system 4. The numerical aperture of the microscope objective lens should not be less than 1 / 2 of the relative aperture of the lens to be measured.

[0071] A star point plate is installed at the focal plane of the collimator. The diameter of the star point plate is smaller than the diffraction limit of the lens to be tested.

[0072] S4: Coarse adjustment: Manually control the three-dimensional electric-controlled translation stage 3 to move the working surface of the microscopic detection system 4 to the target image plane, collect the comparison parameters of the lens to be tested through the image acquisition unit, and reset the values ​​of the electric-controlled turntable 2 and the three-dimensional electric-controlled translation stage 3 to zero;

[0073] S5: Using the microscopic detection system 4 to collect relevant contrast parameters of the lens under test in the contrast field of view, the control processing unit 7 calculates the angle Δα between the optical axis of the lens under test and the optical axis of the test device based on the relevant contrast parameters in the contrast field of view and the parameters set in steps S1 and S2;

[0074] a. When the contrast parameter is diffuse spot diameter or MTF:

[0075] ① Rotate the electric-controlled turntable 2 to the comparison field angle θ, and at the same time move the three-dimensional electric-controlled translation stage 3 along the left and right directions of the optical axis of the test equipment to the corresponding line field y. The movement components are:

[0076] θ = C·ω, where C is the normalized parameter of the comparison field of view, and its value is between 0 and 1. Generally, 0.7-1.0 is selected for comparison; ω is the half field of view angle of the lens to be tested, in degrees;

[0077] y = ftanθ, which is the linear field of view of a general imaging lens, and f is the focal length of the lens to be tested, in mm; or, y = fθ, which is the linear field of view of a fisheye lens;

[0078] ② At this position, the diffuse spot diameter or MTF of the lens to be tested is collected by the microscopic detection system 4 and the test data is given in real time;

[0079] ③ Focus sweep: At this position, the focus of the lens under test is automatically swept according to the aforementioned focus sweep range ΔL and the number of focus sweep points n. After the focus sweep is completed, the information of the discrete focus sweep points is fitted into a focus sweep curve. This curve generally uses the direction axis value of the three-dimensional translation stage 3 along the optical axis of the test device during the focus sweep as the horizontal coordinate, and the value of the focus sweep diameter or MTF as the vertical coordinate. Then, the electric-controlled turntable 2 and the three-dimensional electric-controlled translation stage 3 are both moved in the opposite direction to another comparison field of view and focus is swept again to obtain the focus sweep curve at the other comparison field of view. At this time, the rotation angle of the electric-controlled turntable 2 is 2θ, and the movement amount of the three-dimensional electric-controlled translation stage 3 is 2y.

[0080] ④ Extract the difference in focus at the two sides of the field of view: In the two curves fitted at the two sides of the field of view, the maximum MTF value corresponding to the diffuse spot diameter or Nyquist frequency set in step S2 above has a corresponding axial position Z in each of the two curves. i , extract the difference Δz between the two axial positions and the distance Δy that the three-dimensional electric-controlled translation stage 3 moves to the two comparison viewing fields according to the setting parameters; and Δy=2y;

[0081] ⑤Calculate the angle Δα between the optical axis of the lens to be tested and the optical axis of the test equipment;

[0082]

[0083] b. When the comparison parameter is the installation reference surface:

[0084] ① Move the three-dimensional electric translation stage 3 to position Y along the left and right directions of the optical axis of the test equipment;

[0085] ② At this position, the microscopic detection system 4 collects the image of the mounting reference surface of the lens to be tested, and displays the image of the mounting reference surface in real time;

[0086] ③ Focus Sweep: At this position, the mounting reference surface of the lens under test is automatically focused based on the aforementioned focus sweep range ΔL and the number of focus sweep points n. After completion, the information of the discrete focus sweep points is fitted into a focus sweep curve. This curve generally uses the axis value of the direction of movement of the three-dimensional electric-controlled translation stage 3 along the optical axis of the test equipment during the focus sweep as the abscissa, and the clarity of the image on the mounting reference surface as the ordinate. The three-dimensional electric-controlled translation stage 3 then moves in the opposite direction to another comparison field of view at -Y and performs another focus sweep, obtaining a focus sweep curve at the other comparison field of view.

[0087] ④ Extract the difference in focus at two symmetrical viewpoints: In the two curves fitted at the two contrasting viewpoints, the inflection points of the two curves each correspond to an axial position Z. j , extract the difference Δz between the two axial positions and the distance Δy that the three-dimensional electric-controlled translation stage 3 moves to the two comparison viewing fields according to the setting parameters, and Δy=2Y;

[0088] ⑤Calculate the angle Δα between the optical axis of the lens to be tested and the optical axis of the test equipment.

[0089] S6: Using the control processing unit 7, it is determined whether the angle Δα is less than a preset value. If so, the automatic alignment of the optical system for testing is completed. If not, step S7 is executed. The preset value is considered to be a value of the angle Δα close to 0. The preset value is determined based on the tolerance of different lenses to the angle between their own optical axis and the optical axis of the test equipment.

[0090] S7: Use the control processing unit 7 to determine the direction of the angle Δα, and adjust the rotating stage 5 in the opposite direction to make the angle consistent with the angle Δα, and then return to step S5 until the angle Δα is at the preset value.

[0091] The above are merely embodiments of the present invention and are not intended to limit the present invention. For ordinary professionals in this field, the present invention can have various changes and variations. Any modifications, equivalent replacements, improvements, etc. made within the technical solution of the present invention should be included in the protection scope of the present invention. In addition, it should be noted that the drawings are only for example, they are not drawn according to the conditions of equal proportion, and should not be used as a limitation to the actual scope of protection required by the present invention.

Claims

1. An optical testing system with automatic centering function, characterized by: It includes a testing unit, an optical lens centering adjustment unit and a control processing unit (7); The test unit comprises a light source system (1), and an electrically controlled turntable (2) located in front of a light outlet of the light source system (1); a three-dimensional electrically controlled translation stage (3) and a microscopic detection system (4) are sequentially arranged on the top of the electrically controlled turntable (2) from bottom to top; the three-dimensional electrically controlled translation stage (3) is an orthogonally combined electrically controlled translation stage capable of translationally moving forward, backward, left, right, and up and down along the optical axis of the light source system (1); The optical lens centering adjustment unit is arranged on the electrically controlled turntable (2) and is located between the light source system (1) and the microscopic detection system (4), and comprises a high-precision turntable (5) and an optical lens clamp (6) arranged on the turntable (5), wherein the turntable (5) is an electrically controlled turntable with adjustable rotation angle and pitch direction, and the optical lens clamp (6) is used to clamp the lens to be tested; The control processing unit (7) is electrically connected to the electric-controlled turntable (2), the three-dimensional electric-controlled translation stage (3), the rotation stage (5) and the microscopic detection system (4) respectively, and is used for performing rotation and translation control, data acquisition and image processing analysis.

2. The optical testing system with automatic centering function according to claim 1, characterized in that: The light source system (1) comprises a light source and a collimator.

3. The optical testing system with automatic centering function according to claim 1, characterized in that: The microscopic detection system (4) comprises a microscope objective lens and an image acquisition unit, and the image acquisition unit adopts CCD or CMOS.

4. An automatic centering method, characterized in that: The following steps are involved: S1: Prepare an optical testing system with automatic centering function according to any one of claims 1 to 3; S2: Setting the basic parameters of the reference points required for automatic centering, including the imaging relationship of the lens to be tested, focal length, field of view angle, magnification of the microscopic detection system (4), and pixel size of the image acquisition unit; S3: Select one of the following parameters: diffuse spot diameter, MTF, and mounting reference plane as the comparison parameter based on the type of lens to be tested, and set the corresponding comparison field of view, focus range, and number of focus sampling points. S4: using the optical lens fixture (6) to clamp the lens to be tested; S5: manually controlling the electric-controlled turntable (2) so that the object side of the lens to be tested faces the light outlet direction of the light source system (1), and then controlling the three-dimensional electric-controlled translation stage (3) to move the working surface of the microscopic detection system (4) to the target image plane, collecting the contrast parameters of the lens to be tested in real time through the image acquisition unit, and setting all the values ​​of the electric-controlled turntable (2) and the three-dimensional electric-controlled translation stage (3) to zero; S6: Using the microscopic detection system (4) to collect relevant contrast parameters of the lens to be tested at the contrast field of view, the control processing unit (7) calculates the angle Δα between the optical axis of the lens to be tested and the optical axis of the light source system (1) based on the relevant contrast parameters at the contrast field of view and the various parameters set in steps S2 and S3; S7: using the control processing unit (7) to determine whether the angle Δα is less than a preset value, if so, completing the automatic centering of the optical system for testing; if not, executing step S8; the preset value is regarded as the value of the angle Δα close to 0; S8: Use the control processing unit (7) to determine the direction of the angle Δα, and adjust the rotating stage (5) in the opposite direction to make the angle size consistent with the size of the angle Δα, and then return to step S6 until the size of the angle Δα reaches the preset value.

5. The automatic centering method according to claim 4, characterized in that: In step S3, one of the diffuse spot diameter, MTF, and mounting reference surface is selected as a comparison parameter according to the type of the lens to be tested. Specifically, For energy detection lenses, the diffuse spot diameter is selected as the comparison parameter, and the diffuse spot diameter for energy concentration and contrast field of view is set; When selecting MTF for imaging detection lenses, you need to set the Nyquist frequency; All types of lenses can select a mounting reference surface. The prerequisite for selection is that the mounting reference surface is processed to be perpendicular to the optical axis of the light source system (1) during assembly, and no other parameters need to be set.

6. The automatic centering method according to claim 5, characterized in that: In step S3, the corresponding contrast field of view is set as follows: When the contrast parameter is selected as diffuse spot diameter or MTF, the contrast field of view is set between ±0.7 and ±1.0 of the normalized field of view of the lens to be tested; When selecting the installation reference plane for comparison parameters, the comparison field of view is set at two symmetrical positions ±Y on the installation reference plane that are as far away from the optical axis of the lens to be tested as possible with the optical axis of the light source system (4) as the center, where Y is the distance between the comparison field of view and the optical axis of the lens to be tested.

7. The automatic centering method according to claim 6, characterized in that: In step S3, the method for setting the focus scanning range and the number of focus scanning sampling points is as follows: The front-rear range ΔL of the microscopic detection system (4) moving along the optical axis direction of the light source system (1) is set as the focus range, and the number n of focus sampling points is set within the focus range, where n≥10.

8. The automatic centering method according to claim 7, characterized in that: Step S6 is specifically as follows: The contrast parameter is selected as the diffuse spot diameter or MTF. According to the parameters set in step S2 and step S3, the electric-controlled turntable (2) is rotated to the contrast field angle θ, and the three-dimensional electric-controlled translation stage (3) is moved along the left and right directions of the optical axis of the light source system (1) to the corresponding line field y. The moving component is: θ = C·ω, where C is the normalized parameter of the contrast field of view, and ω is the half field angle of the lens to be tested; y = ftanθ, which is the linear field of view of a general imaging lens, and f is the focal length of the lens to be tested; or, y = fθ, which is the linear field of view of a fisheye lens; At this position, the diffuse spot diameter or MTF of the lens to be tested is collected by a microscopic detection system (4) and test data is given in real time. Then, the diffuse spot diameter or MTF of the lens to be tested is automatically scanned according to the focus range ΔL and the number of focus sampling points n. After the focus is completed, the information of the discrete focus sampling points is fitted into a focus curve. Then, the electric-controlled turntable (2) and the three-dimensional electric-controlled translation stage (3) are moved in the opposite direction to another comparison field of view to scan again, and the focus curve at the position of the other comparison field of view is obtained. According to the focus difference at the two contrasting viewing fields and the moving distance of the three-dimensional electric-controlled translation stage (3) to the two contrasting viewing fields, the angle Δα between the optical axis of the lens to be tested and the optical axis of the light source system (1) is calculated.

9. The automatic centering method according to claim 7, characterized in that: Step S6 is specifically as follows: The installation reference surface is selected by comparing the parameters, and according to the set basic parameters, the three-dimensional electric-controlled translation stage (3) is moved to the Y position along the left and right directions of the optical axis of the light source system (1), and at this position, the installation reference surface of the lens to be tested is collected by the microscopic detection system (4), and the image of the surface of the installation reference surface is displayed in real time; At this position, the mounting reference surface of the lens to be tested is automatically scanned according to the focus range ΔL and the number of focus sampling points n, and after completion, the information of the discrete focus sampling points is fitted into a focus curve, and then the three-dimensional electric-controlled translation stage (3) moves in the opposite direction to another comparison field of view to perform focus scanning again, thereby obtaining a focus curve at another comparison field of view position; The angle Δα between the optical axis of the lens to be tested and the optical axis of the light source system (1) is calculated based on the difference in focus at the two contrasting viewing fields and the moving distance of the three-dimensional electric-controlled translation stage (3) to the two contrasting viewing fields.

Images