Automatic measuring device and detection method for center thickness of lens

Abstract

The application discloses a kind of automatic measuring device and detection method of lens center thickness, including spectral confocal system and Fizeau interference system, spectral confocal system includes light source, confocal pinhole and optical system, and optical system includes first half reflection half permeation lens, chromatic focus lens and spectroscope;Fizeau interference system includes Fizeau interferometer and computer, and Fizeau interferometer includes laser emission component and first imaging mirror, reference mirror, second beam expander, second half reflection half permeation lens, second imaging mirror and CCD camera.The lens center thickness with error component is measured using spectral confocal system, the physical translation error component, tilt error component of the lens to be measured are detected in real time using field calibration and Zernike wave surface fitting in Fizeau interference system, and the measured lens center thickness is automatically corrected using error correction formula, and then the lens center thickness is accurately measured, which can greatly save labor and time cost, and improve detection efficiency.

Description

Technical Field

[0001] This invention relates to the field of lens thickness detection technology, and in particular to an automatic measuring device and detection method for the center thickness of a lens. Background Technology

[0002] Coplanar capacitance and spectral confocal methods are common methods for measuring lens thickness. However, the coplanar capacitance method struggles to locate the vertices of the lens's two surfaces, and its accuracy is significantly affected by environmental factors such as air humidity and temperature. While the spectral confocal method is less demanding in terms of environmental conditions, traditional spectral confocal lens thickness measurement requires ensuring that the optical axis of the lens under test is collinear with the optical axis of the optical system to guarantee measurement accuracy. Fixing the lens typically involves manual or machine clamping to adjust its position. Manual fixing is not only highly demanding on operators but also fails to effectively control the lens offset within the error range, requiring repeated adjustments and resulting in low testing efficiency. Machine clamping not only increases costs but also easily scratches and damages the lens surface during fixation, further affecting measurement accuracy.

[0003] Therefore, in order to solve the problems of low detection accuracy and low detection efficiency caused by the non-collinearity between the optical axis of the lens under test and the optical axis of the optical system in the above-mentioned spectral confocal method for measuring the center thickness of a lens, it is necessary to provide a new lens center thickness detection device and detection method. Summary of the Invention

[0004] The purpose of this invention is to provide an automatic measuring device and detection method for the center thickness of a lens, which solves the problems of low detection accuracy and low detection efficiency caused by the non-collinearity of the optical axis of the lens under test and the optical axis of the optical system in the process of measuring the center thickness of a lens using the spectral confocal method in the prior art, thereby improving the detection accuracy of the center thickness of the lens.

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

[0006] An automatic measurement device and detection method for the center thickness of a lens includes a spectral confocal system and a Fizeau interferometer system. The spectral confocal system includes a light source, a confocal aperture, and an optical system. The confocal aperture is connected to a spectrometer. The optical system includes a first semi-reflective lens, a chromatic lens, and a beam splitter arranged sequentially from the direction closest to the light source to the direction furthest from the light source. The light source is connected to the spectrometer via a Y-type optical fiber. The emitted beam of the Y-type optical fiber is coaxial with the optical axis of the optical system. The distance from the light source to the optical axis of the optical system is equal to the distance from the confocal aperture to the optical axis of the optical system.

[0007] The Fizeau interferometer system includes a Fizeau interferometer and a computer. The Fizeau interferometer includes a laser emitting component and a first imaging mirror, a reference mirror, a second beam expander, a second semi-reflective lens, a second imaging mirror, and a CCD camera arranged in sequence. The laser emitting component is correspondingly arranged with the second semi-reflective lens. The reference mirror is connected to a PZT phase shifter. The optical axes of the first imaging mirror, the reference mirror, the second beam expander, the second semi-reflective lens, the second imaging mirror, and the CCD camera are located on the same straight line and perpendicular to the optical axis of the optical system. A lens under test is placed between the first imaging mirror and the beam splitter.

[0008] Preferably, the laser emitting assembly includes a laser, a reflector, and a first beam expander, wherein the reflector is located on one side of the laser, and the first beam expander is located between the reflector and the second semi-reflective lens.

[0009] Preferably, a filter is provided between the CCD camera and the second semi-reflective lens.

[0010] Preferably, the light source is a bromine-tungsten point light source.

[0011] A method for detecting the center thickness of a lens, characterized by comprising the following steps:

[0012] Step 1: Correct the field of view so that the optical axes of the first imaging mirror, reference mirror, second beam expander, second semi-reflective lens, and second imaging mirror coincide with the optical axis of the CCD camera;

[0013] Step 2: Field calibration, which is to determine the correspondence between the pixels of the CCD camera and the actual physical spatial distance;

[0014] Step 3: Install the lens to be tested at the designated lens placement position;

[0015] Step 4: Start the light source, use a spectrometer to detect the spectral distribution of the light emitted from the confocal aperture, start the laser emission assembly, and use a Fizeau interferometer to obtain a sequence of multiple interference images;

[0016] Step 5: Obtain the center thickness of the lens under test based on the two wavelengths λ1 and λ2 on the spectral distribution diagram. The specific method is as follows:

[0017] Based on the functional relationship of the chromatic aberration confocal system obtained from relevant calibration, the axial chromatic difference S1 and S2 of monochromatic light with wavelength λ1 after passing through the optical system are obtained. Then, the axial chromatic difference S between monochromatic light with wavelengths λ1 and λ2 after passing through the optical system is calculated. Following this, the relationship between the axial chromatic difference S and the center thickness x′ of the lens under test can be obtained based on the geometric relationship of the light path in the lens under test, thus determining the center thickness x′ of the lens under test. The specific formula for calculating the center thickness x′ of the lens under test is as follows:

[0018]

[0019] Where S is the axial chromatic aberration difference between monochromatic light of wavelength λ1 and wavelength λ2 after passing through the chromatic focusing lens; R is the radius of curvature of the surface of the lens under test; n(λ2) is the refractive index of monochromatic light of wavelength λ2 in the lens under test; β is the angle between monochromatic light of wavelength λ2 after passing through the chromatic focusing lens and the optical axis of the optical system; β max This represents the maximum image-side aperture angle of monochromatic light with a wavelength of λ² in an optical system.

[0020] Step 6: Use a computer to process the multiple interference image sequences obtained by the Fizeau interferometer in Step 4. The image processing process consists of three steps: phase extraction, unwrapping, and Zernike wavefront fitting, to obtain a surface shape map with the surface shape of the lens under test.

[0021] Step 7: Based on the offset between the surface center of the lens under test and the surface map center obtained in Step 6, and combined with the correspondence between the CCD camera pixels and the actual physical space distance determined in Step 2, the physical translation error component h of the lens under test is obtained, and the tilt error component α of the lens under test is obtained according to the Zernike wavefront fitting process.

[0022] Step 8: Correct the center thickness x′ of the lens measured in Step 5 based on the physical translation error component h and tilt error component α obtained in Step 7, as follows:

[0023] When the lens under test produces a physical translation error component, the following translation error correction formula is used for correction: Where x represents the actual center thickness of the lens under test, x' is the center thickness of the lens under test obtained in step 5, R is the radius of curvature of the surface of the lens under test, and h is the physical translation error component of the lens under test obtained in step 7.

[0024] When the lens under test produces a tilt error component, the following tilt error correction formula is used for correction: Where x represents the actual center thickness of the lens under test, x' is the center thickness of the lens under test obtained in step 5; R is the radius of curvature of the surface of the lens under test; and α is the tilt error component of the lens under test.

[0025] When the lens under test generates both physical translation error components and tilt error components, since there is no coupling relationship between the two error components, the translation error correction formula is first used to correct the lens to return to the center position, and then the tilt error correction formula is used to correct the lens to obtain the actual center thickness of the lens under test.

[0026] Step 9: End.

[0027] This invention employs an automatic lens center thickness measurement device and detection method with the above-described structure. It utilizes a spectral confocal system to measure the lens center thickness with error components, and uses a Fizeau interferometer system to correct the error in the measured lens center thickness. This reduces the difficulty of fixing the lens under test, realizes intelligent automatic detection of lens center thickness, saves labor and time costs, and improves detection efficiency. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of an embodiment of an automatic lens center thickness measuring device according to the present invention;

[0029] Figure 2 This is a logic flowchart of a method for detecting the center thickness of a lens according to the present invention;

[0030] Figure 3 This is a schematic diagram of the translation error correction formula in the lens center thickness detection method of the present invention;

[0031] Figure 4 This is a schematic diagram of the tilt error correction formula in the lens center thickness detection method of the present invention.

[0032] Figure Labels

[0033] 1. Light source; 2. Confocal aperture; 3. Spectrometer; 4. First semi-reflective lens; 5. Chromatic lens; 6. Beam splitter; 7. Computer; 8. First imaging mirror; 9. Reference mirror; 10. Second beam expander; 11. Second semi-reflective lens; 12. Second imaging mirror; 13. CCD camera; 14. PZT phase shifter; 15. Lens under test; 16. Laser; 17. Reflector; 18. First beam expander; 19. Filter. Detailed Implementation

[0034] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0035] like Figure 1As shown, an automatic lens center thickness measuring device includes a spectral confocal system and a Fizeau interferometer system. The spectral confocal system includes a light source 1, a confocal aperture 2, and an optical system. The light source 1 is a tungsten bromide point light source 1, and the confocal aperture 2 is connected to a spectrometer 3. The optical system includes a first semi-reflective mirror 4, a chromatic focusing lens 5, and a beam splitter 6, arranged sequentially from near to far from the light source 1. The light source 1 is connected to the spectrometer 3 via a Y-type optical fiber, and the emitted beam from the Y-type optical fiber is coaxial with the optical axis of the optical system. The distance from the light source 1 to the optical axis of the optical system is equal to the distance from the confocal aperture 2 to the optical axis of the optical system; that is, the confocal aperture is positioned at the conjugate position of the light source, allowing monochromatic light of wavelength λ1 and wavelength λ2 to converge well at the confocal aperture 2.

[0036] The Fizeau interferometer system includes a Fizeau interferometer and a computer 7. The Fizeau interferometer includes a laser emitting assembly and a first imaging mirror 8, a reference mirror 9, a second beam expander 10, a second semi-reflective mirror 11, a second imaging mirror 12, and a CCD camera 13 arranged sequentially. A filter 19 is provided between the CCD camera 13 and the second semi-reflective mirror 11 to filter stray light and ensure the accuracy and stability of the interference image sequence acquisition process. The laser emitting assembly is correspondingly arranged to the second semi-reflective mirror 11 and includes a laser 15, a reflector 17, and a first beam expander 18. The reflector 17 is located on one side of the laser 15, and the first beam expander 18 is located between the reflector 17 and the second semi-reflective mirror 11. The reference mirror 9 is connected to a PZT phase shifter 14, which allows the reference mirror 9 to move. The optical axes of the first imaging mirror 8, the reference mirror 9, the second beam expander 10, the second semi-reflective lens 11, the second imaging mirror 12, and the CCD camera 13 are located on the same straight line and perpendicular to the optical axis of the optical system. A lens to be tested is provided between the first imaging mirror 8 and the beam splitter 6.

[0037] A method for detecting the center thickness of a lens includes the following steps:

[0038] Step 1: Correct the field of view so that the optical axes of the first imaging mirror 8, reference mirror 9, second beam expander 10, second semi-reflective mirror 11, and second imaging mirror 12 coincide with the optical axis of the CCD camera 13.

[0039] Step 2: Field calibration, determining the correspondence between the pixels of CCD camera 13 and the actual physical spatial distance;

[0040] Step 3: Install the lens under test 15 at the lens under test placement position;

[0041] Step 4: Start the light source 1, use the spectrometer 3 to detect the spectral distribution of the light emitted from the confocal aperture 2, start the laser 15 emission assembly, and use the Fizeau interferometer to obtain a sequence of multiple interference images.

[0042] The process of obtaining the spectral distribution map is as follows: After the light source 1 is introduced into the optical system through the Y-type optical fiber, it forms monochromatic light of different wavelengths. Among them, the monochromatic light of wavelength λ1 converges on the surface of the lens under test 15 near the beam splitter 6, and the monochromatic light of wavelength λ2 converges on the surface of the lens under test 15 near the first imaging mirror 8. According to the reversibility of the optical path, the monochromatic light of wavelength λ1 and the monochromatic light of wavelength λ2 will eventually converge well at the confocal aperture 2. The spectrometer 3 detects the spectral distribution of the light emitted from the confocal aperture 2, and the obtained spectral distribution map is a pattern of two peaks with peak wavelengths of λ1 and λ2.

[0043] The process of obtaining the interference image sequence is as follows: the light emitted by the laser emitting component passes sequentially through the second half-reflecting lens 11, the second beam expander 10, the reference mirror 9, the imaging mirror, and the lens under test 15. Reference light is reflected from the reference mirror 9, and test light is reflected from the lens under test 15. The reference light and test light converge at the target surface of the CCD camera 13 and are processed by the CCD camera 13 to obtain an interference pattern. Phase shifting is introduced using a PZT phase shifter 14, thereby obtaining a sequence of multiple interference images. The specific method of phase shifting by the PZT phase shifter 14 is as follows: by discretely changing the applied electric field, the piezoelectric ceramic pushes the reference mirror 9 to undergo a small displacement in the optical axis direction of the CCD camera 13, thereby changing the interference cavity length between the reference mirror 9 and the CCD camera 13 to introduce phase shifting.

[0044] Step 5: Obtain the center thickness of the lens 15 under test based on the two wavelengths λ1 and λ2 on the spectral distribution diagram. The specific method is as follows:

[0045] Based on the functional relationship of the chromatic aberration confocal system obtained from relevant calibration, the axial chromatic difference S1 and S2 of monochromatic light with wavelength λ1 after passing through the optical system are obtained. Then, the axial chromatic difference S between monochromatic light with wavelengths λ1 and λ2 after passing through the optical system is calculated. Following this, the relationship between the axial chromatic difference S and the center thickness x′ of the lens 15 under test can be obtained based on the geometric relationship of the light path in the lens 15 under test. The specific formula for calculating the center thickness x′ of the lens 15 under test is as follows:

[0046]

[0047] Where S is the axial chromatic aberration difference between monochromatic light of wavelength λ1 and wavelength λ2 after passing through the chromatic focusing lens; R is the radius of curvature of the surface of the lens 15 under test; n(λ2) is the refractive index of monochromatic light of wavelength λ2 in the lens 15 under test; β is the angle between monochromatic light of wavelength λ2 after passing through the chromatic focusing lens 5 and the optical axis of the optical system; β max This represents the maximum image-side aperture angle of monochromatic light with a wavelength of λ² in an optical system.

[0048] Step 6: Using computer 7, the multiple interference image sequences obtained from the Fizeau interferometer in Step 4 are processed. The image processing involves three steps: phase extraction, unwrapping, and Zernike wavefront fitting, to obtain a surface shape map showing the surface shape of the lens 15 under test. As known from existing technology, the phase extraction process, also known as phase decomposition, mainly includes two steps: phase shift calibration and phase solution. In actual measurement, the interference cavity length is difficult to maintain consistently for different lenses 15 under test. Therefore, the phase shift must be calibrated before phase solution in each measurement process. After phase calibration, the phase extraction algorithm needs to calculate the wavefront phase from a series of light intensity interferograms, regardless of the type... Phase extraction algorithms all utilize inverse trigonometric functions to extract the phase, and the obtained wavefront phase values ​​range from [0 to 2π]. Therefore, when there are multiple interference fringes in the same image, the phase distribution will span multiple periods, and a 2π jump will occur at the junction of two periods. Therefore, it is necessary to stretch the discontinuous wavefront and unfold it into a complete wavefront, which is the true wavefront phase distribution of the wavefront to be measured. This process is called unwrapping calculation. The final step is to use Zernike polynomials (generally the first 36 terms are selected) to fit the unwrapped phase distribution to obtain the wavefront morphology information of the surface of the lens 15 to be measured, and obtain a surface shape map with the surface shape of the lens 15 to be measured.

[0049] Step 7: Based on the offset between the surface center of the lens 15 under test and the surface pattern center obtained in Step 6, and combined with the correspondence between the pixels of the CCD camera 13 and the actual physical space distance determined in Step 2, the physical translation error component h of the lens 15 under test is obtained, and the tilt error component α of the lens 15 under test is obtained according to the Zernike wavefront fitting process.

[0050] Step 8: Correct the center thickness x′ of the lens 15 measured in Step 5 based on the physical translation error component h and tilt error component α obtained in Step 7, as follows:

[0051] 1) When the lens 15 under test produces a physical translation error component, the following translation error correction formula is used for correction: Where x represents the actual center thickness of the lens 15 under test, x' is the center thickness of the lens 15 under test obtained in step 5, R is the radius of curvature of the surface of the lens 15 under test, and h is the physical translation error component of the lens 15 under test obtained in step 7.

[0052] The principle behind obtaining the translation error correction formula is as follows: Figure 3Let point A be the intersection of the test surface of lens 15 with the optical axes of the first imaging mirror 8, reference mirror 9, second beam expander 10, second semi-reflective lens 11, and second imaging mirror 12. Draw a perpendicular line AB from point A to the line containing the optical axis of lens 15. Let point C be the intersection of the test surface of lens 15 with the optical axis of lens 15. Then x = x' - BC. Since the radius of curvature of lens 15 is known, let it be R. Point O is the center of the circle containing the radius of curvature. Then BC = R - BO. Therefore, we can conclude that:

[0053] 2) When the lens 15 under test produces a tilt error component, the following tilt error correction formula is used for correction: Where x represents the actual center thickness of the lens 15 under test, x' is the center thickness of the lens 15 under test obtained in step 5; R is the radius of curvature of the surface of the lens 15 under test; and α is the tilt error component of the lens 15 under test.

[0054] The principle behind obtaining the translation error correction formula is as follows: Figure 4 Let point A be the intersection of the test surface of the lens 15 and the optical axes of the first imaging mirror 8, the reference mirror 9, the second beam expander 10, the second semi-reflective lens 11, and the second imaging mirror 12. Draw a perpendicular line AB from point A to the line containing the optical axis of the lens 15. The lens tilt component α can be obtained by fitting the Zernike wavefront, then AB = x'·sinα. Point O is the center of the circle containing the radius of curvature. Since the radius of curvature of the lens 15 under test is known, let it be R. Therefore, we can conclude that:

[0055]

[0056] 3) When the lens under test 15 produces both physical translation error component and tilt error component, since there is no coupling relationship between the two error components, the translation error correction formula is first used to correct the lens to return to the center position, and then the tilt error correction formula is used to correct the actual center thickness of the lens under test 15.

[0057] Step 9: End.

[0058] In this embodiment, the following equipment may adopt the following model standards:

[0059] (1) Bromine tungsten point light source: model is Tianjin Gangdong Technology / GY-30A, power is continuously adjustable, maximum output power: >150W, band range: 350~1200nm, SMA905 fiber optic interface output.

[0060] (2) First half-reflective lens and second half-reflective lens: Daheng, GCC-4011 series broadband beam splitter prism, transmittance / reflectance: 50 / 50; material K9; external dimensions: 25.4mm*25.4mm*25.4mm.

[0061] (3) Chromatic focal length lens: Number of lenses: 4 (8 surfaces), applicable wavelength: 400~1200nm, aperture: 30mm, axial chromatic aberration: 30mm (key parameter, can be adjusted according to testing requirements), object / image numerical aperture: 0.22 / 0.2, object distance: 100-170mm.

[0062] (4) The beam splitter has f = 16 mm and φ = 20.4 mm;

[0063] (5) Confocal aperture: Model: Daheng / GCO-P50A, aperture stop (pinhole), diameter: 50μm.

[0064] (6) Spectrometer: Model: Shanghai Fuxiang Optics Co., Ltd. / FX2000-RD, 200-1100nm, resolution: 0.13nm, integration time: 1ms, SMA905 fiber optic interface input, supports secondary development, and has C++ development dynamic library.

[0065] (7) Laser: 532nm wavelength, 200mw solid-state laser, single longitudinal mode;

[0066] (8) Filter: GCC-2030 series bandpass filter, center wavelength 550nm, half bandwidth 80nm;

[0067] (9) PZT phase shifter: Piezoelectric ceramic PZT drive controller module, linear 130V high voltage output, number of control loops: 1, number of phases: single-phase output channels: 13, accuracy class: 0.2, contact type: 1NO;

[0068] (10) Reference mirror: aperture: 30.48cm, F number: 0.82, reference surface radius: 224.99mm, transmission wavefront peak-to-valley value: 0.095λ, root mean square value: 0.028λ;

[0069] (11) First imaging lens and second imaging lens: brand Daheng, Φ25.4K9 biconvex lens, f=100mm, light transmission aperture: 90%;

[0070] (12) CCD camera: Basler acA2400-50gm area array CCD, 2048*1536 pixels, imaging area size of 3626μm x 2709μm, pixel size of 1.75μm x 1.75μm, maximum speed of 50 frames per second.

[0071] (13) Computer: Model: Advantech IPC-610L-701VG, processor: Intel i5-2400, supports JPEG hardware encoding and decoding, memory: 4GB DDR3. Supports RGB 24-bit interface and TVOUT video output.

[0072] Therefore, the present invention employs the above-mentioned automatic measurement device and detection method for lens center thickness, uses a spectral confocal system to measure the lens center thickness with error components, and uses a Fizeau interferometer system to correct the error of the measured lens center thickness, thereby realizing intelligent automatic detection of lens center thickness, saving labor and time costs, and improving detection efficiency.

[0073] The above are specific embodiments of the present invention, but the scope of protection of the present invention should not be limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A method for detecting the center thickness of a lens based on an automatic lens center thickness measuring device, characterized in that: The automatic lens center thickness measurement device includes a spectral confocal system and a Fizeau interferometer system. The spectral confocal system includes a light source, a confocal aperture, and an optical system. The confocal aperture is connected to a spectrometer. The optical system includes a first semi-reflective lens, a chromatic focal lens, and a beam splitter arranged sequentially from the direction closest to the light source to the direction furthest from the light source. The light source is connected to the spectrometer via a Y-type optical fiber. The emitted beam of the Y-type optical fiber is coaxial with the optical axis of the optical system. The distance from the light source to the optical axis of the optical system is equal to the distance from the confocal aperture to the optical axis of the optical system. The Fizeau interferometer system includes a Fizeau interferometer and a computer. The Fizeau interferometer includes a laser emitting component and a first imaging mirror, a reference mirror, a second beam expander, a second semi-reflective lens, a second imaging mirror, and a CCD camera arranged in sequence. The laser emitting component is correspondingly arranged with the second semi-reflective lens. The reference mirror is connected to a PZT phase shifter. The optical axes of the first imaging mirror, the reference mirror, the second beam expander, the second semi-reflective lens, the second imaging mirror, and the CCD camera are located on the same straight line and perpendicular to the optical axis of the optical system. A lens under test is placed between the first imaging mirror and the beam splitter. The lens center thickness detection method includes the following steps: Step 1: Correct the field of view so that the optical axes of the first imaging mirror, reference mirror, second beam expander, second semi-reflective lens, and second imaging mirror coincide with the optical axis of the CCD camera; Step 2: Field calibration, which is to determine the correspondence between the pixels of the CCD camera and the actual physical spatial distance; Step 3: Install the lens to be tested at the designated lens placement position; Step 4: Start the light source, use a spectrometer to detect the spectral distribution of the light emitted from the confocal aperture, start the laser emission assembly, and use a Fizeau interferometer to obtain a sequence of multiple interference images; Step 5: Based on the two wavelengths on the spectral distribution diagram and The specific method for obtaining the center thickness of the lens to be measured is as follows: Based on the functional relationship of the chromatic confocal system obtained from relevant calibration, the following can be obtained: Axial chromatic aberration of monochromatic light of a given wavelength after passing through an optical system , Axial chromatic aberration of monochromatic light of a given wavelength after passing through an optical system And then to obtain Monochromatic light of wavelength and The axial chromatic aberration difference produced by monochromatic light of a certain wavelength after passing through an optical system Then, based on the geometric relationship of the light path in the lens under test, the axial chromatic aberration value can be obtained. With respect to the center thickness of the lens under test The relationship between the two is used to determine the center thickness of the lens under test. The center thickness of the lens under test The specific calculation formula is as follows: ； in, for Monochromatic light of wavelength and The axial chromatic aberration difference produced when monochromatic light of a certain wavelength passes through a chromatic focusing lens; Let be the radius of curvature of the surface of the lens to be measured; for The refractive index of monochromatic light of a given wavelength in the lens under test; yes The angle between the wavelength of monochromatic light and the optical axis of the optical system after passing through a chromatic focusing lens; express The maximum image-side aperture angle of monochromatic light of a given wavelength in an optical system; Step 6: Use a computer to process the multiple interference image sequences obtained by the Fizeau interferometer in Step 4. The image processing process consists of three steps: phase extraction, unwrapping, and Zernike wavefront fitting, to obtain a surface shape map with the surface shape of the lens under test. Step 7: Based on the offset between the surface center of the lens under test and the center of the surface pattern obtained in Step 6, and combined with the correspondence between the CCD camera pixels and the actual physical space distance determined in Step 2, the physical translation error component h of the lens under test is obtained. The tilt error component of the lens under test is then obtained according to the Zernike wavefront fitting process. ; Step 8: Based on the physical translation error component h and tilt error component obtained in Step 7 The center thickness of the lens under test measured in step 5 The following corrections have been made: When the lens under test produces a physical translation error component, the following translation error correction formula is used for correction: ,in, This indicates the actual center thickness of the lens being measured. The center thickness of the lens to be tested is obtained in step 5. Let be the radius of curvature of the surface of the lens under test, and h be the physical translation error component of the lens under test obtained in step 7. When the lens under test produces a tilt error component, the following tilt error correction formula is used for correction: ,in, This indicates the actual center thickness of the lens being measured. The center thickness of the lens to be tested is obtained in step 5; Let be the radius of curvature of the surface of the lens to be measured; This represents the tilt error component of the lens under test; When the lens under test generates both physical translation error components and tilt error components, since there is no coupling relationship between the two error components, the translation error correction formula is first used to correct the lens to return to the center position, and then the tilt error correction formula is used to correct the lens to obtain the actual center thickness of the lens under test. Step 9: End.

2. The lens center thickness detection method based on an automatic lens center thickness measuring device according to claim 1, characterized in that: The laser emitting assembly includes a laser, a reflector, and a first beam expander. The reflector is located on one side of the laser, and the first beam expander is located between the reflector and the second semi-reflective lens.

3. The lens center thickness detection method based on an automatic lens center thickness measuring device according to claim 2, characterized in that: A filter is provided between the CCD camera and the second semi-reflective lens.

4. The lens center thickness detection method based on an automatic lens center thickness measuring device according to claim 3, characterized in that: The light source is a bromine-tungsten point light source.

Images