Weak-rigidity free-form surface monocrystalline silicon reflecting lens and processing method thereof

Abstract

The invention discloses a weak-rigidity free-form surface monocrystalline silicon reflecting lens and a processing method thereof. The method comprises the following steps: obtaining a monocrystalline silicon block; cutting into blocks; diamond wire cutting; precisely grinding the back surface; performing slicing; the free-form surface sucker adsorbs the lens; precisely grinding the front surface into a cylindrical surface; polishing the magnetorheological elastomer; releasing the lens; the cylindrical sucker adsorbs the lens; precisely grinding and thinning the back surface; releasing the lens; cutting edges and carrying out wet etching on the back surface; and carrying out ion beam modification processing to achieve the final surface shape precision of the free-form surface. According to the X-ray reflecting lens machining method, the free-form surface weak-rigidity reflecting mirror is clamped and deformed into the cylindrical surface for machining, the whole process is ultra-precision grinding and polishing of the cylindrical surface, the machining method is simple and mature, the manufacturing cost is extremely low, dependence on an ultra-high-precision multi-axis linkage machine tool is completely eliminated, and the machining precision is greatly improved. And the machining efficiency is greatly improved, and the method is suitable for mass production of reflectors.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical lenses, and in particular relates to a weak-rigidity free-form surface single-crystal silicon reflective lens and a processing method thereof. Background Art

[0002] X-ray telescopes are key high-end equipment in the fields of deep space autonomous navigation and communication of spacecraft, as well as deep space exploration. Grazing-incidence X-ray reflectors are the core components for deep space exploration X-ray telescopes to achieve focused imaging.

[0003] Generally speaking, the technology of building a high-performance segmented X-ray telescope using thin mirrors can be divided into the following steps: (1) manufacturing precision mirror substrates, including manufacturing precise substrates and stress-free polishing; (2) sputtering metal coatings on the surface of the substrate mirror to enhance its X-ray reflectivity; (3) accurately aligning and assembling the thin-walled mirror without introducing additional deformation; (4) aligning and integrating the modules or shells into a complete telescope. The performance of an X-ray telescope depends on the quality of its reflectors. Therefore, the first step to manufacturing a high-performance X-ray telescope is to prepare high-performance X-ray reflective mirrors.

[0004] At present, through investigation and analysis of the manufacturing process of X-ray telescope lenses at home and abroad, the reflectors of traditional deep space detection X-ray telescopes are mainly prepared using four conventional technologies: direct processing technology of microcrystalline glass, electroplating nickel-cobalt replication technology, epoxy replication technology, and hot glass molding technology.

[0005] The direct processing technology of microcrystalline glass uses microcrystalline glass as the base material of X-ray reflectors. Through the direct processing of microcrystalline glass holes, ultra-precision processing of internal and external surfaces, internal surface polishing and coating, etc., a cylindrical reflector with high surface accuracy and ultra-smooth surface can be obtained. Although this technology can process reflectors with high surface accuracy and high surface integrity, it is difficult to realize the processing of ultra-thin-wall reflectors. The wall thickness of the single-layer reflectors currently processed is relatively large, resulting in a small number of nested layers of reflectors, and the light-collecting area of ​​the telescope is severely limited; The electroplating nickel-cobalt replication technology can obtain a thin-walled cylindrical structure reflector with a thickness of <1 mm and a roughness of Ra <0.5 nm by coating a reflective film and a nickel-cobalt alloy substrate on the surface of a high-precision ultra-smooth mandrel, and then separating the substrate and the reflective film from the mandrel by cooling and demolding. However, the X-ray reflector manufactured by this method is difficult to control due to the stress distribution changes on the reflector surface during electroplating and cooling and demolding, which makes the reflector prone to deformation and difficult to ensure the surface accuracy. Therefore, the angular resolution of the X-ray telescope manufactured based on this method is poor (>10″), which directly affects the telescope's focusing performance on deep space X-rays; The epoxy replication technology uses aluminum with high strength and low density as the base material, which can build an X-ray observatory with light weight, low cost and large effective area. However, the accuracy of the lenses produced by the replication process is greatly limited. In addition, the complex assembly of thousands of mirror segments limits the angular resolution of the manufactured X-ray telescope. Therefore, this technology minimizes cost and weight at the expense of angular resolution while maximizing the effective area. Hot glass forming technology uses molten silica as the forming mandrel. The glass sheet is hot-formed and then cut into the required final shape. The reflective lenses manufactured by this technology have a smaller wall thickness (<0.5mm) and the number of nested layers can reach more than 100 layers. However, the optical components are greatly affected by temperature, and the accuracy of the replicated lenses is seriously dependent on the accuracy of the mandrel. The surface accuracy is low, which ultimately makes the X-ray telescope have a relatively medium angular resolution.

[0006] Telescopes are usually composed of multiple layers of nested thin-walled X-ray mirrors and receiving imaging devices, while the new generation of X-ray telescopes are composed of more than 30,000 weakly rigid single-crystal silicon mirrors nested in multiple layers. The extremely high service performance requires sub-nanometer surface roughness, sub-micron surface accuracy and extremely small slope deviation on hyperbolic cylindrical and parabolic cylindrical mirrors with a thickness of less than 1 mm.

[0007] However, the existing X-ray mirror manufacturing process still has the following problems: 1) The ultra-low surface error of the free-form surface reflector poses a great challenge to the accuracy and rigidity of the machine tool equipment. The machine tool needs to achieve high-precision linkage of three axes or even more axes at the sub-micron level, and also requires the machine tool to have extremely high rigidity and precision retention. 2) The cost and efficiency of using high-precision multi-axis linkage machine tools and manufacturing according to the free-form surface processing technology cannot meet the manufacturing needs of tens of thousands of reflectors. Therefore, in order to meet the requirements of lightweight, high sensitivity, and high resolution of the next generation of X-ray telescopes, it is urgent to develop efficient and high-precision X-ray mirror processing technology. Summary of the invention

[0008] In view of the problems existing in the next generation X-ray reflective lens manufacturing method, such as difficult to control surface shape accuracy, strict requirements on machine tools and equipment, and low processing efficiency, the present invention provides a weakly rigid free-form surface single-crystal silicon reflective lens and a processing method thereof.

[0009] In order to achieve the above object, the present invention adopts the following technical solution: A method for processing a weakly rigid free-form surface single-crystal silicon reflective lens comprises the following steps: 1) Cutting the single crystal silicon ingot using a diamond wire saw to obtain single crystal silicon blocks; 2) The single crystal silicon block is processed by the diamond wire saw arc cutting method to obtain the outer cylindrical surface profile of the reflector; 3) On a two-axis CNC grinder or a three-axis CNC machine tool, use an arc diamond rigid grinding wheel to perform ultra-precision grinding and shaping of the cylindrical surface of the back of the reflector, where the inner concave surface of the reflector is the front side and the outer convex surface is the back side; 4) Slicing the single crystal silicon block processed in step 3 is performed by using a diamond wire saw arc cutting method to obtain a thin-walled reflective lens with a cylindrical profile on both the back and front sides; 5) Using the high-precision free-form porous ceramic suction cup as the clamping reference, the suction of the suction cup is used to achieve the clamping deformation of the cylindrical back of the thin-walled, weak-rigidity reflective lens and make it completely fit the suction cup surface; 6) On a two-axis CNC grinding machine or a three-axis CNC machine tool, use a circular arc diamond rigid grinding wheel and a circular arc diamond elastic grinding wheel to perform high-precision grinding and shaping of the front surface of the reflector according to the cylindrical surface shape; 7) On a two-axis cylindrical grinding and polishing machine, use a polyurethane polishing pad or magnetorheological elastomer to rough polish the front of the reflector, and use magnetorheological shear hardening glue for high surface integrity fine polishing; 8) The suction cup blows air to buffer and release the reflective lens. The front of the lens is deformed from a cylindrical surface to a free-form surface after the elastic stress is released; 9) Using a high-precision cylindrical porous ceramic suction cup as the clamping reference, the suction of the suction cup is used to achieve the front clamping deformation of the free-form surface of the thin-walled, weak-rigid reflective lens and completely fit the suction cup surface shape, and the back of the reflective lens is deformed into a free-form surface; 10) On a two-axis CNC grinder or a three-axis CNC machine tool, use an arc diamond rigid grinding wheel to perform ultra-precision grinding and thinning on the back of the reflector according to the cylindrical surface shape, so that the thickness of the reflector lens is uniform and reaches the design value of <1mm; 11) The suction cup blows air to cushion and release the reflective lens, and the front and back sides of the lens elastically recover to free-form surfaces; 12) According to the actual working size of the reflective lens, trim the edges and perform wet etching on the back to eliminate the damage caused by grinding and trimming; 13) The ion beam polishing method is used to perform high-precision shaping processing on the polished front side of the reflective lens to achieve the final free-form surface accuracy.

[0010] A further improvement of the present invention is that the specific implementation method of step 3) includes: using paraffin to bond the cylindrical silicon block to a flat plate, using a two-axis linkage CNC grinder or a three-axis CNC machine tool to fix it on the machine tool, using a micrometer or a laser displacement sensor to achieve high-precision tool setting, writing a grinding CNC trajectory according to the radius of the cylindrical surface and the corresponding center angle of the arc surface, achieving deterministic grinding and forming of the arc diamond grinding wheel, and continuously compensating the surface shape based on offline and on-site surface shape detection equipment until the requirements are met, and rough grinding is carried out. Use #325 / 400 metal bond diamond grinding wheel or vitrified bond diamond grinding wheel, the grinding depth of single feed is 20-30μm, use #800 metal bond diamond grinding wheel or vitrified bond diamond grinding wheel for semi-finishing grinding, the grinding depth of single feed is 5-10μm, use resin bond diamond grinding wheel with particle size of D7 for finishing grinding, the grinding depth of single feed is 0.5-2μm, the contour surface error PV of the processed reflector is <1μm, and the surface roughness Ra is <20nm.

[0011] A further improvement of the present invention is that the specific implementation method of step 5) includes: designing and manufacturing a free-form porous ceramic suction cup based on the theoretical free-form surface shape, assuming that the surface shape of the suction cup is S0 when not deformed by adsorption, and the cylindrical surface shapes of the front and back sides of the reflective lens are both S1; when the reflective lens is adsorbed and clamped, the back side shape is adsorbed and deformed and completely fits the suction cup surface shape S0, and the front side shape is also elastically deformed to S0, at which time the elastic deformation of the front and back sides of the reflective lens are both ΔS=S0-S1; then the front side of the reflector is ultra-precision ground into a cylindrical surface S1; after releasing the reflective lens, the elastic deformation of the back side is restored to S0-ΔS=S1, that is, the back side is restored to the cylindrical surface shape S1, and the reflector The front side should elastically deform to recover the theoretical free-form surface shape S2, that is, S1-ΔS=S2, so the free-form surface suction cup shape S2=2*S1-S0. The suction cup is then manufactured until the surface shape accuracy reaches less than 1μm, the minimum vacuum degree is determined, the vacuum pump is selected, the vacuum adsorption air path and circuit are built, the adsorption and blowing buffer functions are realized, the repeated adsorption accuracy of the suction cup is tested to meet the experimental requirements, and the entire adsorption deformation process is simulated and experimentally verified to ensure that the cylindrical back side of the reflective lens is clamped and deformed and can completely fit the suction cup surface shape, and that the adsorption force and friction provided by the suction cup can fully meet the effect of the grinding force on the reflective lens during the actual grinding process.

[0012] A further improvement of the present invention is that the specific implementation method of step 6) includes: fixing the reflective lens clamped by the free-form porous ceramic suction cup on a two-axis linkage CNC grinder or a three-axis CNC machine tool, realizing high-precision tool setting based on a micrometer or a laser displacement sensor, programming the grinding CNC trajectory according to the radius of the cylindrical surface and the corresponding center angle of the arc surface, realizing deterministic forming grinding of the arc diamond grinding wheel, continuously compensating the surface shape based on the offline and on-site surface shape detection equipment until the requirements are met, and using a #325 / 400 metal bonded grinding wheel for rough grinding. The grinding depth of a single feed is 20-30μm with a #800 metal bond diamond wheel or a vitrified bond diamond wheel. The semi-finishing grinding uses a #800 metal bond diamond wheel or a vitrified bond diamond wheel with a single feed depth of 5-10μm. Subsequently, a resin bond diamond wheel or an elastic grinding wheel with a particle size of D7 is used to grind the X-ray reflector lens. The grinding depth of a single feed is 0.5-2μm. The contour surface error PV of the processed reflector is <1μm, and the surface roughness Ra is <20nm.

[0013] A further improvement of the present invention is that the specific implementation method of step 7) includes: on a two-axis cylindrical grinding and polishing machine, the full-aperture polishing of the reflector is performed with a polyurethane polishing pad or a magnetron shear hardening polishing pad; the polishing head used is a section of a cut cylindrical surface, and the surface is bonded with a magnetron polishing pad or a polyurethane polishing pad with a thickness of 1 to 5 mm, and the movement of the two vertical axes is controlled based on a dual-rotor model, and the optimized Halbach magnet arrangement is used to provide a uniform magnetic field to the polishing interface, so as to achieve uniform removal of the central area of ​​the reflector lens, and complete the manufacturing of the reflector surface error PV <1μm; during the polishing process, firstly use a polyurethane polishing pad or a magnetorheological elastomer and a 10-15% cerium oxide polishing liquid for efficient polishing, and then use a magnetorheological shear hardening glue as a polishing pad and a 8-12% silicon solution to smooth the high-frequency errors on the surface of the reflector and keep the low-frequency surface shape, and keep the reflector lens immersed in the polishing liquid during the process, and finally achieve a surface roughness Ra <0.5nm, a surface error PV <1μm, and ultra-precision manufacturing of a weak rigid free-form surface reflector.

[0014] A further improvement of the present invention is that the specific implementation method of step 9) includes: designing and manufacturing an outer cylindrical porous ceramic suction cup based on the cylindrical surface shape, the cylindrical radius of the outer cylindrical suction cup is the cylindrical radius corresponding to the best fitting cylindrical surface of the theoretical surface shape of the front side of the free-form surface reflector, and continuously detecting and correcting the suction cup surface shape until the surface shape accuracy reaches less than 1μm, and then using the adsorption force applied by the vacuum adsorption system to achieve adsorption deformation of the front side of the reflector and complete fit with the surface of the suction cup to complete positioning and clamping.

[0015] A further improvement of the present invention is that the specific implementation method of step 10) includes: fixing the reflective lens clamped by the porous ceramic suction cup on the outer cylindrical surface on a two-axis linkage CNC grinder or a three-axis CNC machine tool, realizing high-precision tool setting based on a micrometer or a laser displacement sensor, programming the grinding CNC trajectory according to the radius of the cylindrical surface and the corresponding center angle of the arc surface, realizing deterministic grinding and forming of the arc diamond grinding wheel, and continuously compensating the surface shape based on offline and in-situ surface shape detection equipment until the requirements are met. Semi-finishing grinding uses a #800 metal bond diamond grinding wheel or a ceramic bond diamond grinding wheel, and the grinding depth of a single feed is 5 to 10 μm. Fine grinding uses a D7 resin bond diamond grinding wheel, and the grinding depth of a single feed is 0.5 to 1 μm. The processed reflector profile surface error PV<1 μm and the surface roughness Ra<20nm.

[0016] A further improvement of the present invention is that the specific implementation method of step 12) includes: using a diamond wire cutting machine to remove the edge of the processed reflective lens to retain the actual required reflective mirror area, using a corrosive liquid to wet-etch the back surface to eliminate stress and damage, and protecting the front surface to avoid contact with the corrosive liquid.

[0017] A further improvement of the present invention is that the specific implementation method of step 13) includes: cleaning the reflective lens, detecting the surface shape with high precision, obtaining the surface shape data of the reflective lens, using an ion beam polisher, setting parameters to perform high-precision shaping processing on the reflective lens, and finally achieving the required sub-nanometer surface roughness and sub-micron surface shape accuracy.

[0018] A weak rigid free-form surface single crystal silicon reflective lens is manufactured by adopting the weak rigid free-form surface single crystal silicon reflective lens manufacturing method.

[0019] Compared with the prior art, the present invention has at least the following beneficial technical effects: 1. High processing efficiency and low cost for reflectors. The X-ray reflector lens processing method proposed in the present invention is based on clamping and deforming the free-form surface weak rigid reflector into a cylindrical surface for processing. The entire process is ultra-precision grinding and polishing of the cylindrical surface. The processing method is simple and mature, with extremely low manufacturing cost, completely getting rid of the dependence on ultra-high precision multi-axis linkage machine tools, greatly improving the processing efficiency, and being suitable for mass production of tens of thousands of reflectors.

[0020] 2. High surface precision of the reflector: The present invention adopts mature ultra-precision grinding technology of cylindrical surface and high-precision polishing and shaping method to obtain a weak rigid reflector lens with high surface precision and high surface quality.

[0021] 3. The present invention proposes to use a porous ceramic curved suction cup as a clamping base for a weak rigid reflector. The clamping and disassembly are extremely simple, and the repeated clamping positioning accuracy is high. This solves the clamping problem of the weak rigid reflector and improves the processing efficiency and safety compared to traditional gluing technology.

[0022] 4. The processing technology of pre-deforming the free-form surface into a cylindrical surface proposed in the present invention solves the problem of difficult processing of the free-form surface. The process is simple. It utilizes the weak rigidity of the reflector and pre-deforms the complex surface by adsorption and clamping. It is processed according to the best fitting cylindrical surface and the free-form surface can be realized after the stress is released. The processing method is safe and reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 It is a diagram of the design process of the free-form porous ceramic suction cup surface shape when the back side of the reflective lens is adsorbed and clamped according to the present invention.

[0025] Figure 2 This is a process flow chart for the efficient and high-precision processing of the weakly rigid free-form surface single-crystal silicon reflective lens of the present invention.

[0026] Figure 3 It is a schematic diagram of the efficient processing method of the weakly rigid free-form surface single crystal silicon reflective lens of the present invention. DETAILED DESCRIPTION

[0027] In the following, only some exemplary embodiments are briefly described. As those skilled in the art will appreciate, the described embodiments may be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the drawings and descriptions are considered to be exemplary and non-restrictive in nature.

[0028] When used in the present invention, the terms “include” and “comprising” indicate the presence of described features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or combinations thereof.

[0029] It should also be understood that the terms used in the present specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0030] It should be further understood that the term "and / or" used in the present description and the appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0031] Various structural schematic diagrams of the embodiments disclosed in the present invention are shown in the accompanying drawings. These figures are not drawn to scale, and some details are magnified and some details may be omitted for the purpose of clear expression. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships therebetween are only exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations, and those skilled in the art may additionally design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0032] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0033] In order to solve the problem of ultra-precision processing of thin-walled weak-rigid free-form surface single-crystal silicon reflective lenses, the present invention proposes an efficient processing method for weak-rigid free-form surface single-crystal silicon reflective lenses which sequentially adopts "diamond wire saw cutting silicon ingot into silicon block → diamond wire saw circular arc cutting of single-crystal silicon block cylindrical surface → ultra-precision grinding of single-crystal silicon block cylindrical surface → diamond wire saw circular arc cutting of single-crystal silicon thin-walled weak-rigid reflective lenses → free-form surface suction cup adsorbing the back side (convex surface) of the lens to deform → ultra-precision grinding of the front side (concave surface) of the reflective lens to be cylindrical → ultra-precision polishing of the front side of the reflective lens → suction cup releasing the lens to restore the deformation → cylindrical suction cup adsorbing the front side of the lens to deform → ultra-precision grinding and thinning of the back side of the reflective lens → suction cup releasing the lens to restore the deformation → edge trimming and wet etching of the back side of the reflective lens → ion beam shaping of the front side of the reflective lens".

[0034] Example 1 The present invention provides a method for processing a weakly rigid free-form surface single-crystal silicon reflective lens, comprising the following steps: 1) Cutting the single crystal silicon ingot using a diamond wire saw to obtain single crystal silicon blocks; 2) The single crystal silicon block is processed by the diamond wire saw arc cutting method to obtain the outer cylindrical surface profile of the reflector; 3) On a two-axis CNC grinder or a three-axis CNC machine tool, use an arc diamond rigid grinding wheel to perform ultra-precision grinding and shaping of the cylindrical surface of the back of the reflector, where the inner concave surface of the reflector is the front side and the outer convex surface is the back side; 4) Slicing the single crystal silicon block processed in step 3 is performed by using a diamond wire saw arc cutting method to obtain a thin-walled reflective lens with a cylindrical profile on both the back and front sides; 5) Using the high-precision free-form porous ceramic suction cup as the clamping reference, the suction of the suction cup is used to achieve the clamping deformation of the cylindrical back of the thin-walled, weak-rigidity reflective lens and make it completely fit the suction cup surface; 6) On a two-axis CNC grinding machine or a three-axis CNC machine tool, use a circular arc diamond rigid grinding wheel and a circular arc diamond elastic grinding wheel to perform high-precision grinding and shaping of the front surface of the reflector according to the cylindrical surface shape; 7) On a two-axis cylindrical grinding and polishing machine, use a polyurethane polishing pad or magnetorheological elastomer to rough polish the front of the reflector, and use magnetorheological shear hardening glue for high surface integrity fine polishing; 8) The suction cup blows air to buffer and release the reflective lens. The front of the lens is deformed from a cylindrical surface to a free-form surface after the elastic stress is released; 9) Using a high-precision cylindrical porous ceramic suction cup as the clamping reference, the suction of the suction cup is used to achieve the front clamping deformation of the free-form surface of the thin-walled, weak-rigid reflective lens and completely fit the suction cup surface shape, and the back of the reflective lens is deformed into a free-form surface; 10) On a two-axis CNC grinder or a three-axis CNC machine tool, use an arc diamond rigid grinding wheel to perform ultra-precision grinding and thinning on the back of the reflector according to the cylindrical surface shape, so that the thickness of the reflector lens is uniform and reaches the design value of <1mm; 11) The suction cup blows air to cushion and release the reflective lens, and the front and back sides of the lens elastically recover to free-form surfaces; 12) According to the actual working size of the reflective lens, trim the edges and perform wet etching on the back to eliminate the damage caused by grinding and trimming; 13) The ion beam polishing method is used to perform high-precision shaping processing on the polished front side of the reflective lens to achieve the final free-form surface accuracy.

[0035] Example 2 The present invention provides a method for processing a weakly rigid free-form surface single-crystal silicon reflective lens, comprising the following steps: 1) Cutting a single crystal silicon ingot using a diamond wire saw to obtain a single crystal silicon block, specifically including fixing the single crystal silicon ingot on a workbench of a wire saw and cutting out a single crystal silicon rectangular block of a desired size; 2) Processing a single crystal silicon block by using a diamond wire saw arc cutting method to obtain the outer cylindrical surface profile of the reflector, specifically including programming a cutting CNC trajectory based on the radius of the required cylindrical surface and the center angle of the arc surface, inputting it into the CNC system, and setting the cutting parameters to complete the cutting of the outer cylindrical surface of the reflector; 3) On a two-axis CNC grinder or a three-axis CNC machine tool, use an arc diamond rigid grinding wheel to perform ultra-precision grinding and shaping of the cylindrical surface of the back of the reflector (where the inner concave surface of the reflector is the front side and the outer convex surface is the back side), specifically including using paraffin to bond the cylindrical silicon block to a high-precision flat plate, using the suction cup worktable of the two-axis CNC grinder or the three-axis CNC machine tool to fix it on the machine tool, using a micrometer or a laser displacement sensor to achieve high-precision tool setting, and writing the grinding CNC trajectory according to the radius of the cylindrical surface and the corresponding center angle of the arc surface to achieve deterministic grinding and shaping of the arc diamond grinding wheel, based on the distance The line and in-position surface shape detection equipment continuously compensates the surface shape until it meets the requirements. The rough grinding uses a #325 / 400 metal bond diamond grinding wheel or a ceramic bond diamond grinding wheel, and the grinding depth of a single feed is 20-30μm. The semi-finishing grinding uses a #800 metal bond diamond grinding wheel or a ceramic bond diamond grinding wheel, and the grinding depth of a single feed is 5-10μm. The fine grinding uses a D7 resin bond diamond grinding wheel, and the grinding depth of a single feed is 0.5-2μm. The processed reflector profile surface shape error PV<1μm, and the surface roughness Ra<20nm; 4) Slicing the single crystal silicon block processed in step 3 by a diamond wire saw arc cutting method to obtain a thin-walled reflective lens with a cylindrical profile on both the back and front sides, specifically including programming a cutting CNC trajectory based on the radius of the required cylindrical surface and the center angle of the arc surface, inputting it into the CNC system, and setting cutting parameters to complete the cutting of the cylindrical front side of the reflective lens; 5) Using a high-precision free-form porous ceramic suction cup as the clamping reference, the suction of the suction cup is used to achieve the clamping deformation of the thin-walled weak-rigidity reflective lens cylinder back and make it completely fit the suction cup surface shape. Specifically, it includes designing and manufacturing a free-form porous ceramic suction cup based on the theoretical free-form surface shape. The surface design process of the free-form suction cup is as follows: Figure 1As shown, when there is no deformation due to adsorption, the surface shape of the suction cup is S0, and the cylindrical surface shapes of the front and back of the reflective lens are both S1; when the reflective lens is adsorbed and clamped, the back surface shape is adsorbed and deformed and completely fits the suction cup surface shape S0, and the front surface shape is also elastically deformed to S0. At this time, the elastic deformation of the front and back of the reflective lens is ΔS=S0-S1; then the front of the reflector is ultra-precision ground into a cylindrical surface S1; after releasing the reflective lens, the elastic deformation of the back is restored to S0-ΔS=S1, that is, the back is restored to the cylindrical surface shape S1, and the front of the reflector should be elastically deformed to restore to the theoretical free-form surface shape S2, that is, S1-ΔS=S2. Therefore, the free-form surface suction cup shape S2=2*S1-S0, and then the suction cup is manufactured until the surface shape accuracy reaches less than 1μm, the minimum vacuum degree is determined, and a suitable vacuum pump is selected to complete the construction of the vacuum adsorption gas path and circuit, realize the adsorption and blowing buffer function, and detect the repeated adsorption accuracy of the suction cup to meet the experimental requirements. At the same time, the entire adsorption deformation process is simulated and experimentally verified to ensure that the cylindrical back of the reflective lens is clamped and deformed and can completely fit the suction cup surface shape, and the adsorption force and friction force provided by the suction cup can fully meet the effect of the grinding force on the reflective lens during the actual grinding process to avoid it from falling off and shifting; 6) On a two-axis CNC grinder or three-axis CNC machine tool, use a circular arc diamond rigid grinding wheel and a circular arc diamond elastic grinding wheel to grind and shape the front of the reflector according to the cylindrical surface shape. Specifically, the reflector lens clamped by a free-form porous ceramic suction cup is fixed on the two-axis CNC grinder or three-axis CNC machine tool, and high-precision tool setting is achieved based on a micrometer or a laser displacement sensor. The grinding CNC trajectory is written according to the radius of the cylindrical surface and the corresponding center angle of the arc surface to achieve deterministic shaping grinding of the circular arc diamond grinding wheel. The surface shape is continuously compensated based on offline and on-site surface shape detection equipment until To meet the requirements, rough grinding uses #325 / 400 metal bond diamond grinding wheel or ceramic bond diamond grinding wheel, the grinding depth of a single feed is 20-30μm, semi-finishing grinding uses #800 metal bond diamond grinding wheel or ceramic bond diamond grinding wheel, the grinding depth of a single feed is 5-10μm, and then the resin bond diamond grinding wheel or elastic grinding wheel with a particle size of D7 is used to achieve the fine grinding of the X-ray reflector lens, the grinding depth of a single feed is 0.5-2μm, the processed reflector profile surface error PV<1μm, and the surface roughness Ra<20nm; 7) On a two-axis cylindrical grinding and polishing machine, use a polyurethane polishing pad or magnetorheological elastomer to perform efficient rough polishing on the front of the mirror, and use magnetorheological shear hardening glue for high surface integrity fine polishing. Specifically, on a two-axis cylindrical grinding and polishing machine, use a polyurethane polishing pad or a magnetron shear hardening polishing pad to polish the full aperture of the mirror; the polishing head used is a section of a cut cylindrical surface, and the surface is bonded with a magnetron polishing pad or a polyurethane polishing pad with a thickness of 1 to 5 mm. The movement of the two vertical axes is controlled based on a dual-rotor model, and an optimized Halbach magnet arrangement is used to provide a uniform magnetic field to the polishing interface, so as to achieve uniform removal of the central area of ​​the reflector lens, and complete the manufacturing of the reflector surface error PV <1μm. During the polishing process, a polyurethane polishing pad or a magnetorheological elastomer and a 10-15% cerium oxide polishing liquid are first used for efficient polishing, and then a magnetorheological shear hardening glue is used as a polishing pad with an 8-12% silicon solution to smooth the high-frequency errors on the surface of the mirror and to maintain the shape of the low-frequency surface. During the process, the mirror lens is kept immersed in the polishing liquid, and finally the surface roughness Ra < 0.5nm, the surface shape error PV < 1μm, and the efficient ultra-precision manufacturing of the weak rigid free-form surface mirror is achieved; 8) The suction cup performs air blowing and buffering and releases the reflective lens. The front surface of the lens is deformed from a cylindrical surface to a free-form surface after the elastic stress is released. Specifically, the vacuum pump is turned off, and compressed air is introduced to release the silicon wafer, the prestress is released, the elastic deformation is restored, and the front surface of the lens is deformed to a free-form surface; 9) Using a high-precision cylindrical porous ceramic suction cup as the clamping reference, and utilizing the suction force of the suction cup, the front free-form surface of the thin-walled weak-rigidity reflector lens is clamped and deformed to completely fit the suction cup surface shape, and the back of the reflector lens is deformed into a free-form surface. Specifically, the outer cylindrical porous ceramic suction cup is designed and manufactured based on the cylindrical surface shape. The cylindrical radius of the outer cylindrical suction cup is the cylindrical radius corresponding to the best fitting cylindrical surface of the theoretical front surface of the free-form reflector lens. The suction cup surface shape is continuously detected and corrected until the surface shape accuracy is less than 1μm. Subsequently, the suction force applied by the vacuum adsorption system is used to achieve adsorption deformation of the front of the reflector and complete fit with the surface of the suction cup to complete the positioning clamping; 10) On a two-axis CNC grinder or three-axis CNC machine, use a circular arc diamond rigid grinding wheel to perform ultra-precision grinding and thinning on the back of the reflector according to the cylindrical surface shape, so that the thickness of the reflector lens is uniform and reaches the design value of <1mm. Specifically, the reflector lens clamped by the porous ceramic suction cup on the outer cylindrical surface is fixed on the two-axis CNC grinder or three-axis CNC machine, and high-precision tool setting is achieved based on a micrometer or laser displacement sensor, and the grinding CNC trajectory is written according to the radius of the cylindrical surface and the corresponding center angle of the arc surface. , to achieve deterministic grinding and forming of arc diamond grinding wheel, based on offline and on-site surface shape detection equipment to continuously compensate the surface shape until it meets the requirements, semi-finishing grinding uses #800 metal bond diamond grinding wheel or ceramic bond diamond grinding wheel, the grinding depth of a single feed is 5-10μm, and fine grinding uses D7 resin bond diamond grinding wheel, the grinding depth of a single feed is 0.5-1μm, the processed reflector profile surface shape error PV<1μm, surface roughness Ra<20nm; 11) The suction cup blows air to buffer and release the reflective lens, and the front and back sides of the lens are elastically restored to free-form surfaces. Specifically, the vacuum pump is turned off, and compressed air is introduced to release the silicon wafer, the prestress is released, and the elastic deformation is restored. At this time, the front and back sides of the reflective mirror are both free-form surfaces; 12) According to the actual working size of the reflective lens, trim the edges and wet-etch the back to eliminate the damage caused by grinding and trimming. Specifically, use a diamond wire cutting machine to remove the edges of the processed reflective lens to retain the actual required reflective mirror area, use a corrosive liquid to wet-etch the back to eliminate stress and damage, and protect the front to avoid contact with the corrosive liquid; 13) The ion beam polishing method is used to perform high-precision shaping processing on the polished front side of the reflective lens to achieve the final free-form surface accuracy, which specifically includes cleaning the reflective lens, detecting the surface shape with high precision, obtaining the surface shape data of the reflective lens, and using an ion beam polisher to set parameters to perform high-precision shaping processing on the reflective lens, ultimately achieving the required sub-nanometer surface roughness and sub-micron surface accuracy.

[0036] Example 3 The weak rigidity free-form surface single crystal silicon reflective lens provided by the present invention is manufactured by using the weak rigidity free-form surface single crystal silicon reflective lens manufacturing method described in Example 1 or 2.

[0037] The invention points of the present invention are: 1. Technology and ideas based on clamping and deforming the free-form surface weak rigidity reflector into a cylindrical surface for processing; 2. Combined polishing technology using polyurethane polishing pads or magnetorheological elastomers for efficient rough polishing and magnetorheological shear hardening glue for high surface integrity fine polishing, the design of the polishing head, and the polishing pad, movement mode and magnetic field arrangement during the polishing process; 3. Based on the adsorption of curved surface suction cups, a system for high-precision and high-repeatability clamping and positioning of weak rigidity mirrors and implementation of adsorption prestressing is implemented, and the design idea of ​​the free-form surface suction cup surface shape.

[0038] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the attached claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention. Any figure mark in the claims should not be regarded as limiting the claims involved.

[0039] In addition, it should be understood that although this specification is described in accordance with the implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation modes that can be understood by those skilled in the art. The above content is only to illustrate the technical idea of ​​the present invention, and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution according to the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for processing a weakly rigid free-form surface single-crystal silicon reflective lens, characterized in that: The following steps are involved: 1) Cutting the single crystal silicon ingot using a diamond wire saw to obtain single crystal silicon blocks; 2) The single crystal silicon block is processed by the diamond wire saw arc cutting method to obtain the outer cylindrical surface profile of the reflector; 3) On a two-axis CNC grinder or a three-axis CNC machine tool, use an arc diamond rigid grinding wheel to perform ultra-precision grinding and shaping of the cylindrical surface of the back of the reflector, where the inner concave surface of the reflector is the front side and the outer convex surface is the back side; 4) Slicing the single crystal silicon block processed in step 3 is performed by using a diamond wire saw arc cutting method to obtain a thin-walled reflective lens with a cylindrical profile on both the back and front sides; 5) Using the high-precision free-form porous ceramic suction cup as the clamping reference, the suction of the suction cup is used to achieve the clamping deformation of the cylindrical back of the thin-walled, weak-rigidity reflective lens and make it completely fit the suction cup surface; 6) On a two-axis CNC grinding machine or a three-axis CNC machine tool, use a circular arc diamond rigid grinding wheel and a circular arc diamond elastic grinding wheel to perform high-precision grinding and shaping of the front surface of the reflector according to the cylindrical surface shape; 7) On a two-axis cylindrical grinding and polishing machine, use a polyurethane polishing pad or magnetorheological elastomer to rough polish the front of the reflector, and use magnetorheological shear hardening glue for high surface integrity fine polishing; 8) The suction cup blows air to buffer and release the reflective lens. The front of the lens is deformed from a cylindrical surface to a free-form surface after the elastic stress is released; 9) Using a high-precision cylindrical porous ceramic suction cup as the clamping reference, the suction of the suction cup is used to achieve the front clamping deformation of the free-form surface of the thin-walled, weak-rigid reflective lens and completely fit the suction cup surface shape, and the back of the reflective lens is deformed into a free-form surface; 10) On a two-axis CNC grinder or a three-axis CNC machine tool, use an arc diamond rigid grinding wheel to perform ultra-precision grinding and thinning on the back of the reflector according to the cylindrical surface shape, so that the thickness of the reflector lens is uniform and reaches the design value of <1mm; 11) The suction cup blows air to cushion and release the reflective lens, and the front and back sides of the lens elastically recover to free-form surfaces; 12) According to the actual working size of the reflective lens, trim the edges and perform wet etching on the back to eliminate the damage caused by grinding and trimming; 13) The ion beam polishing method is used to perform high-precision shaping processing on the polished front side of the reflective lens to achieve the final free-form surface accuracy.

2. The method for processing a weakly rigid free-form surface single crystal silicon reflective lens according to claim 1, characterized in that: The specific implementation method of step 3) includes: using paraffin to bond the cylindrical silicon block to the flat plate, using the suction cup workbench of a two-axis linkage CNC grinder or a three-axis CNC machine tool to fix it on the machine tool, realizing high-precision tool setting based on a micrometer or a laser displacement sensor, programming the grinding CNC trajectory according to the radius of the cylindrical surface and the corresponding center angle of the arc surface, realizing deterministic grinding and forming of the arc diamond grinding wheel, and continuously compensating the surface shape based on offline and on-site surface shape detection equipment until the requirements are met. The rough grinding adopts #325 / The 400# metal bond diamond grinding wheel or vitrified bond diamond grinding wheel has a single feed grinding depth of 20-30μm. The semi-finishing grinding uses the #800# metal bond diamond grinding wheel or vitrified bond diamond grinding wheel with a single feed grinding depth of 5-10μm. The finishing grinding uses a resin bond diamond grinding wheel with a particle size of D7 with a single feed grinding depth of 0.5-2μm. The processed reflector profile surface error PV<1μm and the surface roughness Ra<20nm.

3. The method for processing a weakly rigid free-form surface single crystal silicon reflective lens according to claim 1, characterized in that: The specific implementation method of step 5) includes: designing and manufacturing a free-form porous ceramic suction cup based on the theoretical free-form surface shape, assuming that the surface shape of the suction cup is S0 when not deformed by adsorption, and the cylindrical surface shapes of the front and back sides of the reflective lens are both S1; when the reflective lens is adsorbed and clamped, the back side shape is adsorbed and deformed and completely fits the suction cup surface shape S0, and the front side shape is also elastically deformed to S0, at this time, the elastic deformation of the front and back sides of the reflective lens are both ΔS=S0-S1; then, the front side of the reflector is ultra-precision ground into a cylindrical surface S1; after releasing the reflective lens, the elastic deformation of the back side is restored to S0-ΔS=S1, that is, the back side is restored to the cylindrical surface shape S1, and the front side of the reflector is elastically deformed The shape is restored to the theoretical free-form surface shape S2, that is, S1-ΔS=S2, so the free-form surface suction cup shape S2=2*S1-S0. The suction cup is then manufactured until the surface shape accuracy reaches less than 1μm, the minimum vacuum degree is determined, the vacuum pump is selected, the construction of the vacuum adsorption air path and circuit is completed, the adsorption and blowing buffer functions are realized, the repeated adsorption accuracy of the suction cup is tested to meet the experimental requirements, and the entire adsorption deformation process is simulated and experimentally verified to ensure that the cylindrical back side of the reflective lens is clamped and deformed and can completely fit the suction cup surface shape, and the adsorption force and friction provided by the suction cup can fully meet the effect of the grinding force on the reflective lens during the actual grinding process.

4. The method for processing a weakly rigid free-form surface single crystal silicon reflective lens according to claim 1, characterized in that: The specific implementation method of step 6) includes: using a free-form porous ceramic suction cup to clamp the reflective lens on a two-axis linkage CNC grinder or a three-axis CNC machine tool, realizing high-precision tool setting based on a micrometer or a laser displacement sensor, programming the grinding CNC trajectory according to the radius of the cylindrical surface and the corresponding center angle of the arc surface, realizing deterministic forming grinding of the arc diamond grinding wheel, and continuously compensating the surface shape based on offline and on-site surface shape detection equipment until the requirements are met. The rough grinding uses a #325 / 400 metal bond diamond grinding wheel Or ceramic bond diamond grinding wheel, the grinding depth of single feed is 20-30μm, semi-finishing grinding uses #800 metal bond diamond grinding wheel or ceramic bond diamond grinding wheel, the grinding depth of single feed is 5-10μm, and then the resin bond diamond grinding wheel or elastic grinding wheel grinding tool with a particle size of D7 is used to achieve the fine grinding of the X-ray reflector lens, the grinding depth of single feed is 0.5-2μm, the contour surface error PV of the processed reflector is <1μm, and the surface roughness Ra is <20nm.

5. The method for processing a weakly rigid free-form surface single crystal silicon reflective lens according to claim 1, characterized in that: The specific implementation method of step 7) includes: on a two-axis cylindrical grinding and polishing machine, the full-aperture polishing of the reflector is performed with a polyurethane polishing pad or a magnetron shear hardening polishing pad; the polishing head used is a section of a cut cylindrical surface, and the surface is bonded with a magnetron polishing pad or a polyurethane polishing pad with a thickness of 1 to 5 mm, and the movement of the two vertical axes is controlled based on a dual-rotor model, and the optimized Halbach magnet arrangement is used to provide a uniform magnetic field to the polishing interface, so as to achieve uniform removal of the central area of ​​the reflector lens, and complete the manufacturing of the reflector surface error PV <1μm; during the polishing process, firstly use a polyurethane polishing pad or a magnetorheological elastomer and a 10-15% cerium oxide polishing liquid for efficient polishing, and then use a magnetorheological shear hardening glue as a polishing pad and a 8-12% silicon solution to smooth the high-frequency errors on the surface of the reflector and keep the low-frequency surface shape, and keep the reflector lens immersed in the polishing liquid during the process, and finally achieve a surface roughness Ra <0.5nm, a surface error PV <1μm, and ultra-precision manufacturing of a weak rigid free-form surface reflector.

6. The method for processing a weakly rigid free-form surface single crystal silicon reflective lens according to claim 1, characterized in that: The specific implementation method of step 9) includes: designing and manufacturing an outer cylindrical porous ceramic suction cup based on the cylindrical surface shape, the cylindrical radius of the outer cylindrical suction cup is the cylindrical radius corresponding to the best fitting cylindrical surface of the theoretical surface shape of the front side of the free-form surface reflective lens, and continuously detecting and correcting the suction cup surface shape until the surface shape accuracy reaches less than 1μm, and then using the adsorption force applied by the vacuum adsorption system to achieve adsorption deformation of the front side of the reflector and complete fit with the surface of the suction cup to complete positioning and clamping.

7. The method for processing a weakly rigid free-form surface single crystal silicon reflective lens according to claim 1, characterized in that: The specific implementation method of step 10) includes: fixing the reflective lens clamped by the porous ceramic suction cup on the outer cylindrical surface on a two-axis linkage CNC grinder or a three-axis CNC machine tool, realizing high-precision tool setting based on a micrometer or a laser displacement sensor, programming the grinding CNC trajectory according to the radius of the cylindrical surface and the corresponding center angle of the arc surface, realizing deterministic grinding and forming of the arc diamond grinding wheel, and continuously compensating the surface shape based on offline and in-situ surface shape detection equipment until the requirements are met. Semi-finishing grinding uses a #800 metal bond diamond grinding wheel or a ceramic bond diamond grinding wheel, and the grinding depth of a single feed is 5 to 10 μm. Fine grinding uses a D7 resin bond diamond grinding wheel, and the grinding depth of a single feed is 0.5 to 1 μm. The processed reflector profile surface error PV<1μm, and the surface roughness Ra<20nm.

8. The method for processing a weakly rigid free-form surface single crystal silicon reflective lens according to claim 1, characterized in that: The specific implementation method of step 12) includes: using a diamond wire cutting machine to remove the edge of the processed reflective lens, retaining the actual required reflective mirror area, using a corrosive liquid to wet-etch the back side to eliminate stress and damage, and protecting the front side to avoid contact with the corrosive liquid.

9. The method for processing a weakly rigid free-form surface single crystal silicon reflective lens according to claim 1, characterized in that: The specific implementation method of step 13) includes: cleaning the reflective lens, detecting the surface shape with high precision, obtaining the surface shape data of the reflective lens, using an ion beam polisher, setting parameters to perform high-precision shaping processing on the reflective lens, and finally achieving the required sub-nanometer surface roughness and sub-micron surface shape accuracy.

10. A weakly rigid free-form surface single crystal silicon reflective lens, characterized in that: The lens is manufactured by using the weak rigidity free-form surface single crystal silicon reflective lens manufacturing method described in any one of claims 1 to 9.

Images