A high-precision composite detection method for infrared lens surface shape and optical axis error

Abstract

The present invention relates to a high-precision composite detection method for the surface shape and optical axis error of an infrared lens, belonging to the field of advanced optical manufacturing and detection. The method drives the infrared lens to be tested to rotate as designed by placing a lens support fixture on a workpiece stage, and cooperates with two confocal sensors in different directions for measurement, thereby realizing high-precision detection of the infrared lens to be tested. In addition to having technical advantages such as high detection accuracy and high efficiency, the present invention can also be flexibly and conveniently integrated with various commercial non-contact profile measurement equipment without damaging the mirror surface. The method solves the problems existing in traditional detection methods, such as complex detection process, dependence on lens form and position tolerance benchmark accuracy, and inability to detect lens optical axis eccentricity of partial profiles. The proposed process method can realize quantitative high-precision detection and better meet the needs of rapid batch manufacturing of large-sized infrared aspheric lenses.

Description

Technical Field

[0001] The invention belongs to the field of advanced optical manufacturing and detection, and relates to a high-precision composite detection method for infrared lens surface shape and optical axis error. Background Art

[0002] Space infrared optical remote sensors, especially infrared cameras, often use a cold screen design, which uses a catadioptric or refractive system to achieve cold stop matching and suppress external stray radiation. Therefore, space infrared optical remote sensors make extensive use of infrared lens materials such as single crystal silicon and germanium to complete secondary imaging of infrared optical systems at low temperatures, achieving cold stop matching and apochromatization of optical lenses. With the development of China's infrared optical remote sensing technology, infrared optical payloads are showing the development and construction requirements of high detection sensitivity, high performance, and satellite networking. This places higher demands on the manufacturing of the core aspheric lenses in its infrared optical payloads. Therefore, efficient manufacturing of large-scale infrared lenses has become key.

[0003] Generally speaking, the most typical infrared lens in the engineering field is a double-sided design, with one side being aspherical and the other side being spherical. Regardless of whether it is spherical or aspherical, it must go through the main processes of lens blank forming, aspherical / spherical surface milling, grinding, polishing and fine polishing in sequence; in these manufacturing processes, there are many inspection items involved, including the flatness, cylindricity, parallelism and other form and position tolerance parameters of each reference surface of the aspheric lens, the vertex curvature radius, aspheric coefficient, optical axis deviation and aspherical / spherical surface accuracy and other geometric, optical and surface parameters of the aspheric lens. As the size of infrared lenses becomes larger and larger, the optical system has stringent requirements on processing indicators. The most critical indicators for measuring the manufacturing quality of an aspheric lens are mainly surface error and optical axis deviation.

[0004] In the infrared lens processing and testing process chain, depending on the different processing stages, the detection of aspheric surface errors and the detection of optical axes are two relatively independent detection links. The detection of aspheric surface errors generally adopts common detection methods such as zero-position compensation detection method and computational holographic detection method. These methods have high detection accuracy, but require the production of supporting compensation components, and have low detection efficiency and high costs, which are difficult to match the rapid manufacturing needs of infrared lenses. In recent years, commercial contour testing equipment such as luphoscan and NMF-dui and other non-contact contour measurement equipment have emerged, which can realize convenient surface shape detection and have been widely used in the field of infrared lens manufacturing. The detection of optical axis deviation of aspheric lenses continues to use traditional mechanical centering methods, optical transmission centering methods, optical reflection centering methods and other means. The patent "CN Patent 202210866568.6 A high-precision control method based on lens eccentricity" proposes a method for grinding the edge of a set lens and controlling the optical axis eccentricity by grinding the lens edge; Patent "CN201811084502.1 Bidirectional centering and adjustment method for infrared lens group" proposes a lens centering and adjustment method based on the transmission method; Patent "CN201210475654.0 A high-precision high-order aspheric lens eccentricity measurement system and method" proposes a lens optical axis eccentricity detection method using interferometer transmission detection. These methods are mainly used for the optical axis error control of visible light lenses. After technical expansion, they are also applicable to the control of the optical axis error of infrared lenses in principle. However, there are several major problems. First, most of them are in optical Secondly, these methods need to be based on a relatively high lens shape and position reference, and generally need to be within ±5μm to avoid introducing large optical axis tilt and eccentricity test errors; thirdly, it is impossible to accurately test lenses with relatively close aspheric / spherical vertex curvature radii; fourthly, due to the band limitation of infrared materials, an infrared centering instrument is required for high-precision testing; fifthly, these traditional lens optical axis error measurement methods are limited by the superposition of light source wavelength, turntable size and lens assembly errors and are not suitable for large-size infrared lens detection; sixthly, traditional lens optical axis deviation detection methods do not take into account surface errors, especially the influence of coma components on optical axis deviation, and easily transfer errors to the optical system assembly stage, bringing disaster to the system.

[0005] The existing infrared lens manufacturing process involves a large number of frequent aspheric surface accuracy tests and optical axis deviation tests. These two key indicators are relatively independent and use different methods, principles, and test instruments for testing and processing control, which is inefficient. In addition, due to the coupling relationship between the aspheric lens surface error and the optical axis deviation, new test errors are often introduced, which brings hidden dangers to the infrared lens processing and affects the final system assembly and imaging quality. Summary of the Invention

[0006] The technical problem solved by the present invention is: to overcome the shortcomings of the existing technology and propose a high-precision composite detection method for the surface shape and optical axis error of infrared lenses, which can realize the synchronous composite high-precision detection of the surface shape error and optical axis deviation of common large-size infrared lenses such as single crystal silicon and germanium.

[0007] The solution of the present invention is:

[0008] A high-precision composite detection method for infrared lens surface shape and optical axis error, comprising:

[0009] Determine theoretical profile parameters of the infrared lens to be tested according to the design parameters of the infrared lens to be tested; and manufacture a lens support tooling according to the theoretical profile parameters of the infrared lens to be tested;

[0010] Place the lens support fixture on the workpiece stage; align the center of the lens support fixture with the center of the workpiece stage;

[0011] The infrared lens to be tested is placed on the upper surface of the lens support fixture; the infrared lens to be tested has a cylindrical structure; one axial end of the infrared lens to be tested has a spherical groove structure; the other axial end of the infrared lens to be tested has a spherical protrusion structure; the infrared lens to be tested is placed with the spherical groove structure facing upward and the spherical protrusion structure facing downward; a second confocal sensor is set up to align the infrared lens to be tested;

[0012] Moving the second confocal sensor downward so that the second confocal sensor is aligned with the bottom end of the infrared lens to be tested; adjusting the verticality of the infrared lens to be tested by using the second confocal sensor;

[0013] With the help of the electric two-position tilt and eccentricity adjustment function of the workpiece stage, the tilt and eccentricity of the concave aspheric surface are automatically adjusted until the tilt and eccentricity of the infrared lens to be tested are better than 1" / 1μm, and then the adjustment stops;

[0014] Setting up a first confocal sensor; and setting a reading fed back by the first confocal sensor to 0;

[0015] The spherical groove structure on the top of the infrared lens to be tested is sampled at discrete points by an external non-contact profilometer. During the rotation test of the infrared lens to be tested, the first confocal sensor automatically records the relative height loss value under the same ring zone at the outermost position of the spherical protrusion structure of the infrared lens to be tested.

[0016] Fitting the surface shape of the spherical groove structure on the top of the infrared lens to be measured to obtain the surface shape error of the spherical groove structure;

[0017] Calculate the relationship between the coma component in the current surface error and the optical axis of the spherical groove structure;

[0018] The relative tilt and eccentricity vectors of the spherical protrusion structure relative to the spherical groove structure are superimposed to obtain the optical axis deviation of the infrared lens to be tested;

[0019] According to the surface error of the spherical groove structure and the optical axis deviation of the infrared lens to be measured, the process guidance of processing the infrared lens to be measured is completed.

[0020] In the above-mentioned high-precision composite detection device for infrared lens surface shape and optical axis error, the theoretical profile parameters include the test aperture, aspheric coefficient, high-order aspheric parameters, component profile shape and aspheric vertex curvature radius of the infrared lens to be tested.

[0021] In the above-mentioned high-precision composite detection device for infrared lens surface shape and optical axis error, the standard for aligning the center of the lens support fixture with the center of the workpiece stage is:

[0022] The eccentricity error between the center of the lens support fixture and the center of the workpiece stage is within 0.02mm; and ensure that there is no relative sliding between the lens support fixture and the workpiece stage surface, which is strong and reliable.

[0023] In the above-mentioned high-precision composite detection device for the surface shape and optical axis error of an infrared lens, the second confocal sensor is axially aligned horizontally with the side wall of the infrared lens to be tested; the eccentricity of the cylindrical side wall of the infrared lens to be tested is tested and adjusted by the second confocal sensor, and the eccentricity error of the infrared lens to be tested is controlled to be better than 0.01 mm.

[0024] In the above-mentioned high-precision composite detection device for infrared lens surface shape and optical axis error, the method for adjusting the verticality of the infrared lens to be tested by the second confocal sensor is as follows:

[0025] The workpiece stage is controlled to rotate automatically; during one rotation, the angle of the tilted infrared lens to be tested is adjusted until the distance difference between the bottom end surface of the infrared lens to be tested and the second confocal sensor does not exceed 0.01 mm, thus completing the vertical adjustment of the infrared lens to be tested.

[0026] In the above-mentioned high-precision composite detection device for infrared lens surface shape and optical axis error, the first confocal sensor is arranged vertically upward; the first confocal sensor is located below the infrared lens to be tested and is aligned with the edge of the spherical protrusion structure of the infrared lens to be tested.

[0027] In the above-mentioned high-precision composite detection device for infrared lens surface shape and optical axis error, the discrete point sampling method is:

[0028] The radial sampling interval is 0.3-0.5mm, and the circumferential sampling interval is 1-2mm; the workpiece stage speed is controlled in the range of 0.3-1r / s.

[0029] In the above-mentioned high-precision composite detection device for infrared lens surface shape and optical axis error, the method for fitting the surface shape of the spherical groove structure is:

[0030] The nonlinear least squares fitting calculation is adopted. The proportional factor coefficient is introduced in the fitting process. At the same time, the vertex curvature radius of the spherical groove structure and the coefficients of the higher-order terms of the spherical groove structure are approximated by equations to find the optimal equation solution and obtain the surface error of the spherical groove structure. According to the equation parameters of the spherical groove structure to be measured, the relationship between the coma component in the current surface error and the optical axis of the spherical groove structure is calculated.

[0031] In the above-mentioned high-precision composite detection device for infrared lens surface shape and optical axis error, the relative height loss value is the optical axis deviation of the spherical protrusion structure relative to the spherical groove structure, expressed in the form of the maximum equal thickness difference of the edge.

[0032] In the above-mentioned high-precision composite detection device for infrared lens surface shape and optical axis error, the method for processing the infrared lens to be tested is as follows:

[0033] The surface shape error meets the processing requirements through multiple iterations; the optical axis deviation is detected by performing key point detection when the double-sided accuracy of the infrared lens to be tested enters the polishing stage; if it is out of tolerance, it is necessary to mark the inclination direction of the spherical protrusion structure relative to the spherical groove structure during the test, and correct the optical axis deviation data of the lens by grinding or polishing the spherical protrusion structure to finally meet the design requirements.

[0034] The beneficial effects of the present invention compared with the prior art are:

[0035] (1) The present invention provides a high-precision composite detection device for the surface shape and optical axis error of an infrared aspheric lens, which can be quickly and conveniently integrated with a commercial non-contact profiling platform to achieve synchronous detection of the surface shape and optical axis deviation of the aspheric lens. It is also highly portable and can be integrated and built with any test system equipped with a full range of test elements to achieve in-situ detection.

[0036] (2) Compared with the traditional mechanical centering method and the method of centering the transmission / reflection photometric axis, the lens optical axis deviation detection method provided by the present invention takes into account the influence of the coma component in the surface error of the aspheric lens on the optical axis deviation, can more realistically reflect the optical axis deviation of the lens, has high detection accuracy, and will not bring system imaging risks to subsequent optical adjustment;

[0037] (3) The detection method provided by the present invention does not rely on the form and position tolerance datum of the lens. During the test process, the two optical surfaces of the lens are used as the adjustment datum, which solves the problem of large test errors caused by the poor accuracy of the form and position tolerance datum in previous test methods.

[0038] (4) The detection method provided by the present invention can match the fast-paced manufacturing needs of infrared aspheric lenses, with short testing time and high precision. It can effectively improve the efficiency of processing and detection connection, shorten the product development cycle, and improve product development quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a flow chart of the composite detection of the present invention;

[0040] Figure 2 Schematic diagram of the detection process of the infrared lens to be tested according to the present invention;

[0041] Figure 3 Schematic diagram of the mapping relationship between the optical axis tilt / eccentricity error and the surface shape error of the infrared lens to be measured in the present invention. DETAILED DESCRIPTION

[0042] The present invention will be further described below in conjunction with the embodiments.

[0043] The present invention provides a high-precision composite detection method for the surface shape and optical axis error of an infrared lens. In addition to having technical advantages such as high detection accuracy and high efficiency, the method can also be flexibly and conveniently integrated with various commercial non-contact profile measurement equipment without damaging the mirror surface. It also solves the problems existing in traditional detection methods, such as complex detection process, dependence on the reference accuracy of lens form and position tolerances, and inability to detect the eccentricity of the lens optical axis of some contours. The proposed process method can realize quantitative high-precision detection and better meet the needs of rapid batch manufacturing of large-size infrared aspheric lenses.

[0044] The non-contact contour measurement platform of the present invention comprises a workpiece stage, a commercial contour meter probe and a spindle.

[0045] Among them, the workpiece stage provides a test and installation benchmark for the aspheric lens to be tested, and can realize two-dimensional X / Y direction tilt and eccentricity adjustment.

[0046] The commercial profilometer probe is a high-precision probe under a high-precision specific wavelength. The axial resolution error is better than 0.05nm, and the test spot beam diameter can be controlled within 10μm. During the test, it is driven by the control system and can be swung along the axial direction of the mirror.

[0047] The main axis can realize 360-degree automatic rotation test of the aspheric lens to be tested.

[0048] Independent of the non-contact profile measurement platform are two confocal displacement sensors and aspheric lens support fixtures. Among them, the laser confocal displacement sensor has a resolution better than 0.1μm and is used to perform high-precision testing of the distance between the aspheric lens surface and the probe. Laser confocal displacement sensor 1 is used to measure the height distance of the bottom surface of the aspheric lens to be measured, and can calculate the relative height loss difference under the same ring zone of the lens; laser confocal displacement sensor 2 is used to measure the axial distance of the cylindrical surface of the aspheric lens to be measured, so as to control the eccentricity error of the lens relative to the workpiece stage.

[0049] High-precision composite detection method for infrared lens surface shape and optical axis error, such as Figure 1 As shown, the specific steps include:

[0050] The theoretical profile parameters of the infrared lens to be tested are determined based on its design parameters, and a lens support fixture is fabricated based on the theoretical profile parameters. The theoretical profile parameters include the test aperture, aspheric coefficients, high-order aspheric parameters, component profile, and aspheric vertex curvature radius of the infrared lens to be tested.

[0051] Place the lens support fixture on the workpiece stage; align the center of the lens support fixture with the center of the workpiece stage. The standard for aligning the center of the lens support fixture with the center of the workpiece stage is:

[0052] The eccentricity error between the center of the lens support fixture and the center of the workpiece stage is within 0.02mm; and ensure that there is no relative sliding between the lens support fixture and the workpiece stage surface, which is strong and reliable.

[0053] The infrared lens to be tested is placed on the upper surface of the lens support fixture; the infrared lens to be tested has a cylindrical structure; one axial end of the infrared lens to be tested has a spherical groove structure; the other axial end of the infrared lens to be tested has a spherical protrusion structure; the infrared lens to be tested is placed with the spherical groove structure facing upward and the spherical protrusion structure facing downward; a second confocal sensor is set up to align the infrared lens to be tested;

[0054] The second confocal sensor is axially and horizontally aligned with the side wall of the infrared lens to be tested; the eccentricity of the cylindrical side wall of the infrared lens to be tested is tested and adjusted by the second confocal sensor, and the eccentricity error of the infrared lens to be tested is controlled to be better than 0.01mm.

[0055] The second confocal sensor is moved downward to align with the bottom end of the infrared lens to be tested; and the verticality of the infrared lens to be tested is adjusted by the second confocal sensor.

[0056] The method for adjusting the verticality of the infrared lens to be measured by the second confocal sensor is as follows:

[0057] The workpiece stage is controlled to rotate automatically; during one rotation, the angle of the tilted infrared lens to be tested is adjusted until the distance difference between the bottom end surface of the infrared lens to be tested and the second confocal sensor does not exceed 0.01 mm, thus completing the vertical adjustment of the infrared lens to be tested.

[0058] With the help of the electric two-position tilt and eccentricity adjustment function of the workpiece stage, the tilt and eccentricity of the concave aspheric surface are automatically adjusted until the tilt and eccentricity of the infrared lens to be tested are better than 1" / 1μm, and then the adjustment stops.

[0059] A first confocal sensor is set up; and a reading fed back by the first confocal sensor is set to 0.

[0060] like Figure 2 As shown, the first confocal sensor is arranged vertically upward; the first confocal sensor is located below the infrared lens to be tested and is aligned with the edge of the spherical protrusion structure of the infrared lens to be tested.

[0061] The discrete points of the spherical groove structure on the top of the infrared lens to be tested are sampled by an external non-contact profilometer; during the rotation test of the infrared lens to be tested, the first confocal sensor automatically records the relative height loss value under the same ring zone at the outermost position of the spherical protrusion structure of the infrared lens to be tested.

[0062] The method of discrete point sampling is:

[0063] The radial sampling interval is 0.3-0.5mm, and the circumferential sampling interval is 1-2mm; the workpiece stage speed is controlled in the range of 0.3-1r / s.

[0064] The surface shape of the spherical groove structure on the top of the infrared lens to be measured is fitted to obtain the surface shape error of the spherical groove structure.

[0065] The method for fitting the surface shape of the spherical groove structure is:

[0066] The nonlinear least squares fitting calculation is adopted. The proportional factor coefficient is introduced in the fitting process. At the same time, the vertex curvature radius of the spherical groove structure and the coefficients of each order of higher-order terms of the spherical groove structure are approximated by equations to find the optimal equation solution and obtain the surface error of the spherical groove structure.

[0067] Based on the equation parameters of the spherical groove structure to be measured, the relationship between the coma component of the current surface error and the optical axis of the spherical groove structure is calculated. The relationship table is shown in Table 1.

[0068] Table 1

[0069] Eccentricity (μm) 1 5 10 15 20 tilt(") Coma (λ)

[0070] The relative height loss is the optical axis deviation of the spherical protrusion structure relative to the spherical groove structure, expressed as the maximum thickness difference at the edge. Based on the corresponding relationship in Table 1, the base tilt or decentering error of the spherical groove structure in its current state is obtained. The relative tilt and decentering vectors of the spherical protrusion structure relative to the spherical groove structure are superimposed to obtain the optical axis deviation of the infrared lens under test.

[0071] According to the surface error of the spherical groove structure and the optical axis deviation of the infrared lens to be measured, the process guidance of processing the infrared lens to be measured is completed.

[0072] The method for processing the infrared lens to be tested is:

[0073] The surface shape error meets the processing requirements through multiple iterations; the optical axis deviation is detected by performing key point detection when the double-sided accuracy of the infrared lens to be tested enters the polishing stage; if it is out of tolerance, it is necessary to mark the inclination direction of the spherical protrusion structure relative to the spherical groove structure during the test, and correct the optical axis deviation data of the lens by grinding or polishing the spherical protrusion structure to finally meet the design requirements.

[0074] Example of processing process

[0075] A typical infrared aspheric lens has a concave surface that is a high-order aspheric surface, an effective aperture of Φ510mm, and a surface profile that is a tenth-order aspheric surface. The expression is:

[0076]

[0077] in, is the vertex curvature, R = -1316.93mm; K = -e 2 =0 is the quadratic curve constant;

[0078] The coefficients of the higher-order terms are: A4 = -2.1489e-09, A6 = 1.5077e-15, A8 = 2.3095e-19, A10 = 0.5879e-20.

[0079] The convex surface is a spherical surface, and the vertex curvature radius R1 = 430.88 mm.

[0080] The surface accuracy of both surfaces is required to be better than λ / 50rms, the fitting residual of 36 Zernike coefficients is required to be better than 0.02λrms, the error of the aspheric vertex curvature radius is required to be better than 1μm, and the lens thickness difference caused by optical axis deviation is required to be better than 10μm.

[0081] The process steps are as follows:

[0082] Step 1: Cutting the mirror blank

[0083] The outer diameter of the lens is 270mm. The single crystal silicon blank is rounded and cut using rough processing equipment such as a cutting machine. A 0.5mm margin is reserved on one side of the outer circle and a 1mm margin is reserved for the center thickness. The final cylindrical lens blank has a size of Φ271m and a thickness of 30.89mm.

[0084] Step 2: Mirror blank forming and surface milling

[0085] The lens blank is placed on the working platform of the milling machine. The initial outer cylindricality and any bottom surface are used as the adjustment reference to tighten the parts. The plane is then milled with a milling wheel. The flatness error after milling can reach 10μm. At this time, the surface is turned over and used as the bottom surface of the lens to start the milling of lens surface 2. Since surface 2 is a high-order aspheric surface, 3D modeling is performed according to the aspheric equation parameters, and the aspheric surface is directly milled in one step. Since the process route of milling the best-fit spherical surface and then changing it to an aspheric surface is avoided in the traditional process, a higher aspheric milling accuracy can be achieved. At the same time, the aspheric surface profile after milling is relatively smooth, laying a good process foundation for subsequent frequency band error control.

[0086] After milling, surface 2 is flipped over. Once the convex spherical surface is milled, a milling coordinate system is established using plane B as a reference, and the lens's outer diameter is machined. During the milling process, the tolerances of various geometric parameters are controlled to meet design requirements, with cylindricity errors better than 3μm, flatness errors better than 5-10μm, and parallelism errors between the convex platform and the B reference better than 5μm.

[0087] Step 3: Single-point diamond turning

[0088] A good lens shape benchmark has been established during the milling process. In the single-point diamond turning stage, the concave aspheric surface is first turned to further improve the flatness accuracy of the B reference platform surface, and its flatness error is turned to within 2μm. Then the concave aspheric surface is turned; after the concave aspheric surface turning is completed, the convex spherical surface is turned. The single-point diamond turning process method of this process is relatively mature and will not be described in detail.

[0089] The process connection between turning and polishing is established by matching frequency band error characteristics. In traditional processes, these two parts are separated. The resulting problem is that the surface shape after turning often needs to be repeatedly processed in the polishing process, resulting in waste of resources and repeated surface shape. Therefore, here, the first stage of control is carried out in the turning stage through the method of Gaussian function high-pass filtering. The typical surface shape processing error distribution after turning mainly shows surface shape errors in the low-frequency band. This is due to the error in the curvature radius of the aspheric vertex caused by tool wear during the turning process, resulting in a large POWER error. At this time, the tool parameters for single-point diamond turning are selected and the process parameters are optimized. A natural single-point diamond turning tool with an R2mm arc blade is selected, the single-point diamond X-axis step spacing is set to no less than 0.005mm, the spindle speed is reduced to 1500rpm, the feed depth is adjusted to the range of 5-8μm according to the turning damage layer on the surface of the single crystal silicon, the feed speed is reduced to F2.5, and then the surface error detection after turning is performed until the result after using Gaussian function high-pass filtering (frequency band ≥18mm) is better than 0.02λrms. The typical morphological feature distribution is as follows Figure 3 shown.

[0090] Step 4: Rough polishing by robot

[0091] The single-crystal silicon aspheric lens that has entered the rough polishing stage of the robot has a surface accuracy of about λ / 5rms and is covered with damage layers of varying depths. The depth of the damage layer is radially distributed. Observation through a laser confocal microscope shows that the damage layer causes pit defects, with the deepest depth being about 10-15μm.

[0092] First, an airbag polishing tool head is integrated on the robotic polishing platform, and an R30mm airbag is selected to extract and optimize the corresponding removal function. The process parameters are set as pressure 10N, actual output 25N; rotation speed 120rpm; and cerium oxide polishing liquid with a particle size of 1.5μm.

[0093] The present invention provides a high-precision composite detection device for the surface shape and optical axis error of infrared aspheric lenses. The device can be quickly and conveniently integrated with a commercial non-contact profiling platform to achieve synchronous detection of the surface shape and optical axis deviation of aspheric lenses. The device is highly portable and can be integrated and built with any test system equipped with a full range of test elements to achieve in-situ detection.

[0094] Compared with the traditional mechanical centering method and the method of center-biased transmission / reflection photometric axis, the lens optical axis deviation detection method provided by the present invention takes into account the influence of the coma component in the surface error of the aspheric lens on the optical axis deviation, can more realistically reflect the optical axis deviation of the lens, has high detection accuracy, and will not bring system imaging risks to subsequent optical assembly.

[0095] The detection method provided by the present invention does not rely on the form and position tolerance datum of the lens. During the test process, the two optical surfaces of the lens are used as the adjustment datum, which solves the problem of large test errors caused by the poor accuracy of the form and position tolerance datum in previous test methods.

[0096] The detection method provided by the present invention can match the fast-paced manufacturing needs of infrared aspheric lenses, has short testing time and high precision, can effectively improve the efficiency of processing and detection connection, shorten the product development cycle, and improve product development quality.

[0097] Although the present invention has been disclosed above in terms of preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications to the technical solutions of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the scope of protection of the technical solutions of the present invention.

Claims

1. A high-precision composite detection method for infrared lens surface shape and optical axis error, characterized by: include: Determining theoretical profile parameters of the infrared lens to be tested according to the design parameters of the infrared lens to be tested; Making a lens support fixture according to the theoretical profile parameters of the infrared lens to be tested; Place the lens support fixture on the workpiece stage; The center of the lens support fixture is aligned with the center of the workpiece stage; Place the infrared lens to be tested on the upper surface of the lens support fixture; The infrared lens to be tested has a cylindrical structure; one axial end of the infrared lens to be tested has a spherical groove structure; the other axial end of the infrared lens to be tested has a spherical protrusion structure; The infrared lens to be tested is placed with the spherical groove structure facing upward and the spherical protrusion structure facing downward; Set up a second confocal sensor to align the infrared lens to be tested; Move the second confocal sensor downward so that the second confocal sensor is aligned with the bottom end of the infrared lens to be tested; Adjusting the verticality of the infrared lens to be tested by using a second confocal sensor; With the help of the electric two-position tilt and eccentricity adjustment function of the workpiece stage, the tilt and eccentricity of the concave aspheric surface are automatically adjusted until the tilt and eccentricity of the infrared lens to be tested are better than 1" / 1μm, and then the adjustment stops; Setting up a first confocal sensor; and setting a reading fed back by the first confocal sensor to 0; The discrete points of the spherical groove structure on the top of the infrared lens are sampled by an external non-contact profilometer; During the rotation test of the infrared lens to be tested, the first confocal sensor automatically records the relative height loss value under the same ring zone at the outermost position of the spherical convex structure of the infrared lens to be tested; Fitting the surface shape of the spherical groove structure on the top of the infrared lens to be measured to obtain the surface shape error of the spherical groove structure; Calculate the relationship between the coma component in the current surface error and the optical axis of the spherical groove structure; The relative tilt and eccentricity vectors of the spherical protrusion structure relative to the spherical groove structure are superimposed to obtain the optical axis deviation of the infrared lens to be tested; According to the surface error of the spherical groove structure and the optical axis deviation of the infrared lens to be measured, the process guidance of processing the infrared lens to be measured is completed.

2. The high-precision composite detection method for infrared lens surface shape and optical axis error according to claim 1, characterized in that: The theoretical profile parameters include the test aperture, aspheric coefficient, high-order aspheric parameters, element profile shape and aspheric vertex curvature radius of the infrared lens to be tested.

3. The high-precision composite detection method for infrared lens surface shape and optical axis error according to claim 1, characterized in that: The standard for aligning the center of the lens support fixture with the center of the workpiece stage is: The eccentricity error between the center of the lens support fixture and the center of the workpiece stage is within 0.02mm; and ensure that there is no relative sliding between the lens support fixture and the workpiece stage surface, which is strong and reliable.

4. The high-precision composite detection method for infrared lens surface shape and optical axis error according to claim 1, characterized in that: The second confocal sensor is axially and horizontally aligned with the side wall of the infrared lens to be tested; the eccentricity of the cylindrical side wall of the infrared lens to be tested is tested and adjusted by the second confocal sensor, and the eccentricity error of the infrared lens to be tested is controlled to be better than 0.01mm.

5. The high-precision composite detection method for infrared lens surface shape and optical axis error according to claim 1, characterized in that: The method for adjusting the verticality of the infrared lens to be measured by the second confocal sensor is as follows: The workpiece stage is controlled to rotate automatically; during one rotation, the angle of the tilted infrared lens to be tested is adjusted until the distance difference between the bottom end surface of the infrared lens to be tested and the second confocal sensor does not exceed 0.01 mm, thus completing the vertical adjustment of the infrared lens to be tested.

6. The high-precision composite detection method for infrared lens surface shape and optical axis error according to claim 1, characterized in that: The first confocal sensor is arranged vertically upward; the first confocal sensor is located below the infrared lens to be tested and is aligned with the edge of the spherical protrusion structure of the infrared lens to be tested.

7. The high-precision composite detection method for infrared lens surface shape and optical axis error according to claim 1, characterized in that: The method of discrete point sampling is: The radial sampling interval is 0.3-0.5mm, and the circumferential sampling interval is 1-2mm; the workpiece stage speed is controlled in the range of 0.3-1r / s.

8. The high-precision composite detection method for infrared lens surface shape and optical axis error according to claim 1, characterized in that: The method for fitting the surface shape of the spherical groove structure is: The nonlinear least squares fitting calculation is adopted. The proportional factor coefficient is introduced in the fitting process. At the same time, the vertex curvature radius of the spherical groove structure and the coefficients of the higher-order terms of the spherical groove structure are approximated by equations to find the optimal equation solution and obtain the surface error of the spherical groove structure. According to the equation parameters of the spherical groove structure to be measured, the relationship between the coma component in the current surface error and the optical axis of the spherical groove structure is calculated.

9. The high-precision composite detection method for infrared lens surface shape and optical axis error according to claim 1, characterized in that: The relative height loss value is the optical axis deviation of the spherical protrusion structure relative to the spherical groove structure, which is expressed in the form of the maximum equal thickness difference of the edge.

10. The high-precision composite detection method for infrared lens surface shape and optical axis error according to claim 1, characterized in that: The method for processing the infrared lens to be tested is: The surface shape error meets the processing requirements through multiple iterations; the optical axis deviation is detected by performing key point detection when the double-sided accuracy of the infrared lens to be tested enters the polishing stage; if it is out of tolerance, it is necessary to mark the inclination direction of the spherical protrusion structure relative to the spherical groove structure during the test, and correct the optical axis deviation data of the lens by grinding or polishing the spherical protrusion structure to finally meet the design requirements.

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