Method and system for measuring surface type of lens by using long-wave infrared band interference

Abstract

The invention relates to a method for measuring the surface type of a lens by using long-wave infrared band interference. The method comprises the following steps: acquiring a long-wave infrared interferometer which is adjusted in advance; the long-wave infrared interferometer emits a long-wave infrared light beam, the long-wave infrared light beam is reflected by the standard lens and the to-be-measured lens to form interference fringes, the to-be-measured lens is a milled lens, and the surface of the to-be-measured lens is a rough surface; and obtaining surface type data of the to-be-detected lens according to interference fringe analysis. The invention also relates to a system for measuring the surface type of the lens by using the long-wave infrared band interference. The method has the beneficial effects that the strong penetrability of long-wave infrared light is utilized, the long-wave infrared light can penetrate through the surface microstructure of the rough lens, the scattering interference is reduced, more reflected light participates in interference, the surface roughness can be analyzed more stably, the measurement time of the lens surface type is shortened, and the subsequent processing procedure can be carried out more timely.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical testing, in particular to a method and system for measuring the surface profile of a lens by long-wave infrared interferometry. BACKGROUND

[0002] In the process of precision optical processing, the surface of the glass after milling and grinding usually needs to be detected by means of a three-coordinate measuring instrument. However, for large-diameter lenses, three-coordinate measurement has significant drawbacks: the measurement is extremely time-consuming, which not only seriously affects production efficiency, but also may delay the subsequent processing procedures due to the excessively long measurement period. On the other hand, although existing interferometers can be used for lens surface profile measurement, they can only measure the relatively smooth mirror surface after polishing through short-wave infrared measurement, and cannot be applied to rough lenses after milling and grinding. SUMMARY

[0003] The technical problem to be solved by the embodiments of the present application is to provide a method and system for measuring the surface profile of a lens by long-wave infrared interferometry. Based on the strong penetration of long-wave infrared light, the surface microstructure of the rough lens can be penetrated, the scattering interference is reduced, more reflected light is ensured to participate in interference, the measurement time of the lens surface profile is shortened, and the subsequent processing procedures can be carried out more timely.

[0004] To solve the above technical problems, the present application provides a method for measuring the surface profile of a lens by long-wave infrared interferometry, comprising, obtaining a long-wave infrared interferometer adjusted in advance; The long-wave infrared interferometer emits a long-wave infrared light beam, and the long-wave infrared light beam forms interference fringes after being reflected by a standard lens and a lens to be measured. The lens to be measured is a lens after milling and grinding, and the surface of the lens to be measured is rough. According to the interference fringes, the surface profile data of the lens to be measured is obtained.

[0005] In a feasible implementation manner, the long-wave infrared interferometer adjusted in advance is obtained, comprising, determining the device parameters of the long-wave infrared interferometer according to the size of the lens to be measured and the test accuracy requirement; calibrating and debugging the long-wave infrared interferometer to determine whether the long-wave infrared interferometer meets the preset standard, and obtaining the long-wave infrared interferometer adjusted in advance.

[0006] In a feasible implementation manner, the long-wave infrared interferometer emits a long-wave infrared light beam, and the long-wave infrared light beam forms interference fringes after being reflected by a standard lens and a lens to be measured, comprising, The long-wave infrared interferometer emits a long-wave infrared light beam; The long-wave infrared beam is incident on the standard lens to form a first ray and a second ray. The first ray returns through the standard lens to form a reference beam, and the second ray is transmitted through the standard lens to the lens under test and then returns to form a reflected beam. The long-wave infrared interferometer receives the reference beam and the reflected beam, and the interference forms the interference fringes.

[0007] In one feasible implementation, obtaining the surface profile data of the lens under test based on the interference fringe analysis includes, Based on the shape, spacing, and intensity distribution characteristics of the interference fringes, and combined with a preset optical model and mathematical algorithm, the interference fringes are converted into height difference information of the surface of the lens under test, thereby obtaining the surface profile data of the lens under test.

[0008] In one feasible implementation, the method further includes, Calculate the error range between the surface profile data of the lens under test and the standard data; Determine whether the error range exceeds a preset threshold. If it does, check and optimize the measurement process. If not, directly output the surface data of the lens under test.

[0009] In one feasible implementation, the standard data is obtained by measuring a standard surface sample lens using the long-wave infrared interferometer.

[0010] Accordingly, this application also relates to a system for measuring the surface profile of a lens using long-wave infrared interferometry, comprising, Equipment preparation module, used to pre-adjust the long-wave infrared interferometer; The surface shape measurement module emits a long-wave infrared beam through the long-wave infrared interferometer. The long-wave infrared beam forms interference fringes after being reflected by a standard lens and the lens under test. The lens under test is a milled lens with a rough surface. The data analysis module is used to analyze the interference fringes to obtain the surface profile data of the lens under test.

[0011] In one feasible implementation, the center of the standard lens near the surface of the lens under test coincides with the center of the lens under test.

[0012] In one feasible implementation, the wavelength of the long-wave infrared beam is .

[0013] In one feasible implementation, the long-wave infrared interferometer includes a detector for capturing the interference fringes.

[0014] Implementing this invention has the following beneficial effects: By utilizing the strong penetrability of long-wave infrared light, it is possible to penetrate the surface microstructure of rough lenses, reduce scattering interference, and allow more reflected light to participate in interference. This enables more stable resolution of surface roughness, shortens the measurement time of lens surface shape, and allows subsequent processing steps to be carried out more promptly.

[0015] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description

[0016] Figure 1 This is a step diagram of the method for measuring the surface shape of a lens using long-wave infrared interferometry according to the present invention; Figure 2 This is a flowchart illustrating the steps of obtaining a pre-adjusted long-wave infrared interferometer according to the present invention; Figure 3 This is a step diagram illustrating the formation of interference fringes according to the present invention; Figure 4 This is the optical path diagram of the long-wave infrared band interferometric measurement lens surface of the present invention. Detailed Implementation

[0017] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0018] It should be noted that when a component is said to be "fixed to" another component, it can be directly attached to the other component or there may be an intervening component. When a component is said to be "connected to" another component, it can be directly connected to the other component or there may be an intervening component. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0020] An interferometer is used to measure the surface shape of a lens. However, the interferometer uses short-wave infrared light. For rough surfaces with high roughness, the short-wave infrared interferometer is prone to scattering due to the irregular structure of the lens surface, which leads to signal attenuation or distortion. Therefore, it cannot measure the roughness of the lens surface.

[0021] A method for measuring the surface profile of a lens using long-wave infrared interferometry, referring to... Figure 1 , Figure 4 ,include, Step S100: Obtain the pre-adjusted long-wave infrared interferometer 10; In step S200, the long-wave infrared interferometer 10 emits a long-wave infrared beam. The long-wave infrared beam is reflected by the standard lens 20 and the lens under test 30 to form interference fringes. The lens under test 30 is a milled lens with a rough surface. Step S300: Obtain the surface profile data of the lens 30 under test based on interference fringe analysis; Step S400: Calculate the error range between the surface profile data of the lens 30 to be tested and the standard data; In step S500, determine whether the error range exceeds the preset threshold. If yes, check and optimize the measurement process. If no, directly output the surface data of the lens 30 to be tested.

[0022] Specifically, this invention measures the rough surface after milling using long-wave infrared light. Utilizing the strong penetrability of long-wave infrared light, it can penetrate the surface microstructure of the rough lens, reduce scattering interference, improve the signal-to-noise ratio, and allow more reflected light to participate in interference. This enables more stable resolution of surface roughness, shortens the measurement time of the lens surface shape, and allows subsequent processing steps to be carried out more promptly.

[0023] A comparative test is conducted using a sample lens with a known standard surface shape. The surface shape data obtained by the method of this invention is compared with the standard surface shape data of the sample lens, and the difference is calculated to evaluate the measurement error range. If the error exceeds a preset threshold, the testing process is checked and optimized, including recalibrating the interferometer and checking the stability of the lens fixation, until the measurement accuracy meets the requirements.

[0024] In one feasible implementation, a pre-adjusted long-wave infrared interferometer 10 is obtained, with reference to... Figure 2 ,include, Step S101: Determine the equipment parameters of the long-wave infrared interferometer 10 according to the size of the lens 30 to be tested and the test accuracy requirements; Step S102: The long-wave infrared interferometer 10 is calibrated and adjusted to ensure that the long-wave infrared interferometer 10 meets the preset standard, and the adjusted long-wave infrared interferometer 10 is obtained.

[0025] Specifically, a suitable long-wave infrared interferometer 10 is selected. Based on the size of the lens 30 under test and the expected test accuracy requirements, the model and relevant technical parameters of the interferometer are determined to ensure that it can cover the test range of the lens and has sufficient resolution.

[0026] The long-wave infrared interferometer 10 was calibrated and debugged to ensure stable operation and that its measurement accuracy met the preset standards. The calibration process included precise adjustment of key parameters such as light source intensity and optical path difference, as well as calibration of the sensitivity of the detector inside the long-wave infrared interferometer 10, to ensure accurate reception and recording of interference signals.

[0027] In one feasible implementation, a long-wave infrared interferometer 10 emits a long-wave infrared beam. The beam, after being reflected by a standard lens 20 and a lens under test 30, forms interference fringes, as referenced... Figure 3 ,include, Step S201: The long-wave infrared interferometer 10 emits a long-wave infrared beam; In step S202, the long-wave infrared beam is incident on the standard lens 20 to form a first ray and a second ray. The first ray returns through the standard lens 20 to form a reference beam, and the second ray is transmitted through the standard lens 20 to the lens under test 30 and then returns to form a reflected beam. In step S203, the long-wave infrared interferometer 10 receives the reference beam and the reflected beam, and interference fringes are formed.

[0028] Specifically, the long-wave infrared interferometer 10 is turned on, emitting a long-wave infrared beam that illuminates the surface of the lens 30 under test. The long-wave infrared beam is incident on the last surface of the standard lens 20 (i.e., the surface closest to the lens 30 under test), forming a first ray and a second ray. The first ray returns along the same path after reaching the last surface of the standard lens 20, forming a reference beam. The second ray is transmitted through the standard lens 20 to the lens 30 under test and then returns along the same path, forming a reflected beam. The long-wave infrared light can penetrate the relatively rough microstructure of the milled lens surface well, interacting with the lens surface to produce reflected light. The reflected light interferes with the reference light, thus forming interference fringes.

[0029] In one feasible implementation, the surface profile data of the lens 30 under test is obtained based on interference fringe analysis, including: Based on the shape, spacing, and intensity distribution characteristics of the interference fringes, combined with the preset optical model and mathematical algorithm, the interference fringes are converted into height difference information of the surface of the lens 30 under test, and the surface profile data of the lens 30 under test are obtained. The standard data is obtained by measuring the standard surface sample lens using a long-wave infrared interferometer 10.

[0030] Specifically, interference fringe information is acquired using the detector of an interferometer. The surface profile data of the lens is calculated through analysis and processing of the interference fringes. Preprocessing (denoising and smoothing) can be performed on the acquired fringe images, and Fourier transform can be used to extract the spatial frequencies of the fringes. A phase unwrapping algorithm can be used to eliminate... Phase ambiguity results in a continuous phase distribution; according to the conversion formula: ; Where λ = 10 μm, For phase difference, The height is used to calculate the height value of each point on the lens surface, and then the surface shape of the lens is reconstructed.

[0031] Accordingly, this application also relates to a system for measuring the surface profile of a lens using long-wave infrared interferometry, comprising, Equipment preparation module, used to pre-adjust the long-wave infrared interferometer 10; The surface measurement module emits a long-wave infrared beam through the long-wave infrared interferometer 10. The long-wave infrared beam is reflected by the standard lens 20 and the lens under test 30 to form interference fringes. The lens under test 30 is a milled lens with a rough surface. The data analysis module is used to analyze interference fringes to obtain the surface profile data of the lens 30 under test.

[0032] Among them, the long-wave infrared interferometer 10 is used to transmit and receive long-wave infrared beams; The standard lens 20 is located on the light-emitting side of the long-wave infrared interferometer 10. After the long-wave infrared beam is incident on the standard lens 20, it forms a first ray and a second ray. The first ray returns through the standard lens 20 to form a reference beam. The second ray is transmitted through the standard lens 20 to the lens under test 30 and then returns through the same path to form a reflected beam. The lens under test 30 is located on the light-emitting side of the standard lens 20. The reference beam and the reflected beam interfere with each other in the long-wave infrared interferometer 10 to form interference fringes. The lens under test 30 is a milled lens with a rough surface.

[0033] Specifically, the system also includes a fixing device for clamping the standard lens 20. This device uses a three-point support mechanism, with each support point equipped with a piezoelectric fine-tuning stage to correct the lens's mounting tilt angle and ensure stability without wobbling during testing. The fixing device must be designed according to the lens's shape and weight to securely clamp the lens without damaging its surface or introducing additional stress.

[0034] This embodiment uses an infrared long-wavelength interferometer 10. Because of its longer wavelength, it can detect rougher spherical or aspherical surface profiles, significantly increasing the measurement speed when inspecting the surface profile of large-aperture lenses. It also meets the high-precision testing requirements for milled lenses.

[0035] Interferometers process interference fringes using phase analysis or height analysis. For example, phase changes correspond to the gradient of surface height, while height changes directly reflect the amplitude of roughness fluctuations. For rough surfaces, the longer wavelengths of long-wave infrared light can cover a larger range of height differences (e.g., on the order of several micrometers), avoiding phase ambiguity caused by heights exceeding wavelength orders, thus resolving surface roughness more stably.

[0036] An interferometer based on the long-wavelength infrared band is used to measure large-aperture lenses. Compared with traditional coordinate measuring machines (CMMs), the long-wavelength infrared interferometric testing method of this invention has significant advantages. In terms of measurement speed, it greatly shortens the testing time for the surface shape of large-aperture lenses, effectively improving production efficiency and enabling subsequent processing steps to be carried out more promptly.

[0037] In terms of measurement accuracy, by reasonably selecting the interferometer and through a precise calibration and debugging process, the high-precision testing requirements of the milled lens can be met, providing reliable data support for subsequent precision machining.

[0038] In addition, long-wave infrared interferometry has a lower risk of damaging the lens surface, which helps to ensure the quality and performance of the lens.

[0039] In one feasible implementation, the center of the surface of the standard lens 20 near the lens under test 30 coincides with the center of the lens under test 30.

[0040] Specifically, when the two centers coincide, the long-wave infrared beam, after being transmitted through the standard lens 20, can be precisely focused on the curvature center (spherical lens) or vertex (aspherical lens) of the lens under test 30. The reflected beam can return to the interferometer completely along the original optical path, maintaining coaxial interference with the reference beam. If the centers do not coincide, the beam will generate an additional optical path difference due to the incident angle deviation, causing a systematic shift in the interference fringes and affecting the accuracy of the surface data.

[0041] In one feasible implementation, the wavelength of the long-wave infrared beam is .

[0042] Specifically, long-wave infrared beams have longer wavelengths, allowing them to penetrate microscopic surface roughness and reduce scattering interference. Their wavelength range can cover surface height differences on the order of several micrometers, avoiding phase ambiguity caused by heights exceeding the wavelength order, thus stabilizing the resolution of surface roughness. In contrast, short-wave infrared beams have shorter wavelengths (e.g., It is difficult to cover the height difference range of a rough surface, and therefore cannot form effective interference.

[0043] In one feasible implementation, the long-wave infrared interferometer 10 includes a detector for capturing interference fringes within the long-wave infrared interferometer 10. Specifically, detectors (such as infrared focal plane arrays) can convert the optical signals of interference fringes into electrical signals, and their pixel resolution determines their ability to capture fringe details. For rough surfaces after milling, the local curvature and spacing changes of interference fringes directly reflect the surface height difference. Detectors capture these subtle changes with high sensitivity, ensuring that subsequent algorithms (such as phase unwrapping) can accurately convert them into surface height data, achieving high-precision surface reconstruction.

[0044] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0045] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for measuring the surface profile of a lens using long-wave infrared interferometry, characterized in that, include, Obtain a pre-adjusted long-wave infrared interferometer; The long-wave infrared interferometer emits a long-wave infrared beam, which forms interference fringes after being reflected by a standard lens and a lens under test. The lens under test is a milled lens with a rough surface. The long-wave infrared beam emitted by the long-wave infrared interferometer is configured to cover the surface height difference of the lens under test. The surface profile data of the lens under test are obtained based on the interference fringe analysis. The process of acquiring the pre-adjusted long-wave infrared interferometer includes: The equipment parameters of the long-wave infrared interferometer are determined based on the size of the lens under test and the required testing accuracy. The long-wave infrared interferometer is calibrated and adjusted to ensure that it meets the preset standard, thus obtaining the adjusted long-wave infrared interferometer.

2. The method for measuring the surface profile of a lens using long-wave infrared interferometry according to claim 1, characterized in that, The long-wave infrared interferometer emits a long-wave infrared beam, which, after being reflected by a standard lens and the lens under test, forms interference fringes, including... The long-wave infrared interferometer emits a long-wave infrared beam; The long-wave infrared beam is incident on the standard lens to form a first ray and a second ray. The first ray returns through the standard lens to form a reference beam, and the second ray is transmitted through the standard lens to the lens under test and then returns to form a reflected beam. The long-wave infrared interferometer receives the reference beam and the reflected beam, and the interference forms the interference fringes.

3. The method for measuring the surface profile of a lens using long-wave infrared interferometry according to claim 1, characterized in that, The process of obtaining the surface profile data of the lens under test based on the interference fringe analysis includes, Based on the shape, spacing, and intensity distribution characteristics of the interference fringes, and combined with a preset optical model and mathematical algorithm, the interference fringes are converted into height difference information of the surface of the lens under test, thereby obtaining the surface profile data of the lens under test.

4. The method for measuring the surface profile of a lens using long-wave infrared interferometry according to claim 1, characterized in that, The method also includes, Calculate the error range between the surface profile data of the lens under test and the standard data; Determine whether the error range exceeds a preset threshold. If it does, check and optimize the measurement process. If not, directly output the surface data of the lens under test.

5. The method for measuring the surface profile of a lens using long-wave infrared interferometry according to claim 4, characterized in that, The standard data is obtained by measuring the standard surface sample lens using the long-wave infrared interferometer.

6. A system for measuring the surface profile of a lens using long-wave infrared interferometry, characterized in that, The method for implementing the interferometric measurement of lens surface profile using long-wave infrared band as described in any one of claims 1-5 includes, The equipment preparation module is used to pre-adjust the long-wave infrared interferometer; The surface shape measurement module emits a long-wave infrared beam through the long-wave infrared interferometer. The long-wave infrared beam is reflected by the standard lens and the lens under test to form the interference fringes. The lens under test is a milled lens with a rough surface. The data analysis module is used to analyze the interference fringes to obtain the surface profile data of the lens under test.

7. The system for measuring the surface profile of a lens using long-wave infrared interferometry according to claim 6, characterized in that, The center of the standard lens near the surface of the lens under test coincides with the center of the lens under test.

8. The system for measuring the surface profile of a lens using long-wave infrared interferometry according to claim 6, characterized in that, The wavelength of the long-wave infrared beam is .

9. The system for measuring the surface profile of a lens using long-wave infrared interferometry according to claim 6, characterized in that, The long-wave infrared interferometer is equipped with a detector used to capture the interference fringes.

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