Ultra-smooth surface polishing device and process for optical element with complex curved surface

Abstract

The invention discloses an ultra-smooth surface polishing device and process for a complex curved surface optical element, and belongs to the technical field of optical element machining. The device comprises a solution tank, a workpiece clamp, a three-layer composite polishing belt, a driving mechanism, a finishing wheel, an XYZ three-axis motion platform, a positioning system and a pressure control system; the process comprises the steps of workpiece pretreatment and cleaning, clamping and positioning, process parameter planning, solution injection and polishing execution, aftertreatment and detection. According to the method, through atomic-scale removal dominated by catalytic reaction, flexible attachment of the composite polishing belt and timed updating of the catalyst, subsurface damage-free polishing of a complex curved surface is achieved, the method is matched with various hard and brittle materials such as monocrystalline silicon, silicon carbide and fused quartz glass, and the ultra-smooth requirements of the fields such as laser, aerospace and extreme ultraviolet lithography for optical elements are met.

Description

Technical Field

[0001] This invention relates to the field of optical component processing technology, and in particular to an ultra-smooth surface polishing device and process for complex curved optical components. Background Technology

[0002] With the advancement of modern science and technology, especially the rapid progress in microelectronics, optics, and related technologies, an increasing number of modern scientific research projects and civilian and commercial equipment require optical components with high surface quality. Optical components are widely used in various key optical instruments and equipment in laser, aerospace, space exploration, and other cutting-edge technology fields. In conventional optical systems, optical components used for reflection and refraction require a surface roughness Ra < 0.012 μm to be usable. However, the development of short-wavelength optics, especially high-power laser technology, electronics, and thin-film technology, places even more stringent requirements on the surface roughness of optical components, requiring a surface roughness of less than 1 nm. For extreme ultraviolet lithography machines, the surface roughness requirement for the lithography objective lens is as high as 0.2 nm. These stringent surface quality requirements in these fields pose challenges to the ultra-precision manufacturing technology of optical components, especially the manufacturing technology for ultra-smooth surfaces. In the future, more and more applications may require surface roughness at the sub-nanometer or even picometer level. In fact, ultra-precision polishing technology for optical components has become one of the important factors restricting the further development of modern optical technology.

[0003] Traditional polishing methods typically utilize a polishing film to create relative motion between the polishing powder and the workpiece, thereby removing surface material. This process easily generates processing stress, leading to subsurface damage and leaving polishing powder residue on the surface after processing, causing surface contamination. Currently, catalyst-assisted etching polishing technology is a novel abrasive-free polishing technique. Its polishing principle is as follows: molecules in a fluid decompose under the action of a catalyst to generate active hydroxyl groups. These hydroxyl groups adsorb onto the microscopic protrusions on the workpiece surface and undergo hydrolysis, forming covalent bonds between catalyst atoms on the polishing wheel and workpiece surface atoms. Due to the continuous rotation of the polishing wheel, atoms at these bonds are stripped, and atoms on the surface protrusions preferentially form covalent bonds and are thus preferentially removed, ultimately achieving surface polishing. Because no abrasive is involved in the process, this technology has significant advantages such as no subsurface damage and no abrasive embedding. It is worth emphasizing that this technology has successfully achieved extremely low surface roughness of less than 0.1 nm on various materials such as single-crystal silicon, silicon carbide, gallium nitride, fused silica glass, and YAG ceramics, which is difficult to achieve with other polishing techniques. The surface roughness achievable by chemical mechanical polishing (CMP) technology, which is widely used in industry, is around 0.5-1 nm; the surface roughness achievable by magnetorheological polishing technology is about 0.4-0.5 nm; while ion beam polishing technology is mostly used to correct low-frequency surface shape errors, but its ability to correct high-frequency roughness is relatively weak.

[0004] Although catalyst-assisted etching and polishing technology has been studied for many years, the research has primarily focused on planar components, using full-aperture ring polishing methods and mainly applying it to the processing of third-generation semiconductor wafers. There are few reports on ultra-smooth polishing technology for the increasingly widely used aspherical and even free-form surface components. Furthermore, in catalyst-assisted polishing technology, the catalytic efficiency of the catalyst on the polishing pad surface decreases significantly with processing time, which severely affects the polishing efficiency and stability. To address these two issues, there is an urgent need for a polishing device and process capable of efficiently obtaining ultra-smooth surfaces with extremely low roughness on complex curved surfaces. Summary of the Invention

[0005] The purpose of this invention is to provide an ultra-smooth surface polishing device and process for complex curved optical components. It combines traditional belt abrasive polishing technology with catalyst-assisted etching polishing technology, taking into account the advantages of both processing methods. It realizes the timed renewal of the catalyst on the surface of the polishing disc, improves polishing efficiency, and can achieve ultra-smooth polishing of complex curved surfaces of various non-metallic materials.

[0006] This invention provides an ultra-smooth surface polishing device for complex curved optical elements, comprising: Solution tank, used to hold polishing solution; The workpiece clamp is fixed in the solution tank to fix the workpiece to be polished. The workpiece clamp can be made of glue, clay or asphalt to fix the workpiece to be polished, or an existing clamp can be selected to fix the workpiece to be polished so that the workpiece to be polished remains stationary during the polishing process. The composite polishing belt has a three-layer composite structure, consisting of a support layer, a buffer layer, and a catalyst layer from the substrate to the working surface. The composite polishing belt is placed above the workpiece to be polished. The driving mechanism, on which the composite polishing belt is sleeved, drives the composite polishing belt to move, thereby achieving relative movement with the surface of the workpiece to be polished; The dressing wheel, made of hard material, is located on one side of the composite polishing belt and is used to intermittently scrape and renew the surface of the catalyst layer of the composite polishing belt. X Y Z-axis three-axis motion platform, the drive mechanism is located at X Y On the Z-axis motion platform, X Y The Z-axis motion platform is used to drive the drive mechanism and the dressing wheel along the X, Y, and Z axes to achieve full-envelope polishing of complex curved optical components; X Y The Z-axis motion platform uses cylinders or ball screw slides with servo motors and linear guides to connect in the X, Y and Z directions, respectively, to achieve linkage in the X, Y and Z directions. The positioning system, including a non-contact laser displacement sensor or laser tracker, is used to scan the curved surface of the workpiece to be polished and generate a pose compensation file.

[0007] Preferably, in the above-mentioned ultra-smooth surface polishing device for complex curved optical elements, the thickness of the support layer is 0.5-1.5 mm, and it is made of polyester fiber or cotton cloth matrix and Al2O3 or SiC abrasive with a particle size of 5-30 μm. The support layer can also adopt other structures to give the polishing belt a certain degree of flexibility.

[0008] Preferably, in the above-mentioned ultra-smooth surface polishing device for complex curved optical elements, the buffer layer has a thickness of 1.0-3.0 mm, a hardness of 60-80 Shore A, and an elastic modulus in the range of 10-100 MPa, and is bonded to the carrier layer by coating or hot pressing.

[0009] Preferably, in the above-mentioned ultra-smooth surface polishing apparatus for complex curved optical elements, the catalyst layer has a thickness of 100-300 nm and is a metal catalyst film prepared by magnetron sputtering or electrochemical deposition, or a bonded metal catalyst foil. The catalyst layer can use a catalyst, such as nickel, platinum, or other alloys, as long as it has catalytic ability.

[0010] Preferably, in the above-mentioned ultra-smooth surface polishing device for complex curved optical elements, the driving mechanism includes a drive wheel, a contact wheel, and a tension wheel. The drive wheel drives the contact wheel to rotate via a motor. The outer layer of the contact wheel is covered with polyurethane with a hardness of 60-80 Shore A and a wheel diameter of 20-50 mm.

[0011] Preferably, in the above-mentioned ultra-smooth surface polishing device for complex curved optical elements, the dressing wheel is a diamond dressing wheel or a carbide wheel with fine texture on its surface. The dressing wheel is equipped with a feeding mechanism to drive the dressing wheel to contact and move away from the composite polishing belt. The dressing wheel is driven to rotate by a motor and performs a scraping action for 5-10 seconds every 10 minutes of processing to renew the surface of the catalyst layer of the composite polishing belt. The feeding mechanism adopts a cylinder or ball screw slide combined with a servo motor and a linear guide.

[0012] Preferably, the surface of the catalyst layer of the composite polishing belt can be renewed without the use of a dressing wheel, and a catalyst renewal method can be used, such as chemical dissolution or electrochemical dissolution.

[0013] Preferably, in the above-mentioned ultra-smooth surface polishing apparatus for complex curved optical elements, the polishing solution is an acidic or neutral hydrogen peroxide mixed solution, specifically formulated as: deionized water, 3%-10% H2O2 by volume, and 0.1 mol... L of H2SO4 or HCl, with the pH adjusted to 3-5. The above catalytic process can also be accomplished using other chemical solution formulations, such as pure water, hydrofluoric acid solution, or by adding additives.

[0014] Preferably, the above-mentioned ultra-smooth surface polishing device for complex curved optical elements also includes a pressure control system, which performs closed-loop feedback control through a pressure sensor installed on the contact wheel shaft, and dynamically adjusts the polishing pressure according to the workpiece curvature.

[0015] A polishing process for an ultra-smooth surface device for complex curved optical elements, as described above, is provided, comprising the following steps: Step 1: Pre-treatment and cleaning of the workpiece. The workpiece to be polished is ultrasonically cleaned for 10 minutes each in acetone, anhydrous ethanol and deionized water, and then dried with high-purity nitrogen. Step 2: Workpiece clamping and spatial positioning. Use a workpiece fixture to fix the workpiece to be polished in the solution tank. Scan the workpiece surface through the positioning system to generate high-precision point cloud data, and fit it to generate a pose compensation file. Step 3: Process parameter planning and CNC code generation. Based on the workpiece's surface geometry, plan the polishing path and dynamically adjust the polishing pressure. Integrate the path, pressure parameters, spindle speed, and dressing wheel intermittent motion program into the CNC program. The polishing path is either a grating path with equal residual height or an Archimedean spiral path, with a path step size equal to 1 / 3 of the polishing strip contact width. 5 to 1 3. Polishing pressure is 0.5-2 psi in convex curved areas with small radius of curvature, and 2-5 psi in flat areas or areas with large radius of curvature. Step 4: Inject the solution and perform polishing. Inject polishing solution into the solution tank, start the drive mechanism to move the composite polishing belt, and move it via X. Y The Z-axis motion platform drives the drive mechanism to move along the planned trajectory, and the dressing wheel performs catalyst surface renewal actions according to the preset cycle, continuously polishing until the predetermined time. Step 5: Post-processing and inspection. Remove the workpiece and ultrasonically clean it with deionized water. After drying it with nitrogen, measure the surface roughness using a white light interferometer or atomic force microscope.

[0016] Preferably, in the above-mentioned ultra-smooth surface polishing process for complex curved optical elements, the intermittent operation procedure of the dressing wheel in step 4 is to perform a scraping action lasting 5-10 seconds every 10 minutes of polishing.

[0017] Therefore, the present invention employs the above-described ultra-smooth surface polishing device and process for complex curved optical elements, which has the following beneficial effects: (1) The material removal mechanism is transformed from traditional mechanical force-dominated to chemical reaction-dominated. Through the interaction of a specially designed catalyst and solution system, highly active chemical substances are activated in situ on the workpiece surface. These active substances selectively form weakly bonded intermediate states with surface atoms, significantly reducing the interatomic binding energy. When external force is introduced, the weakened atomic layers detach from the substrate in a near-zero stress manner, achieving atomic-scale layer-by-layer peeling. Since the reaction depth is precisely controlled at the level of a single atomic layer and the effective range is strictly limited to the catalyst contact area, the material removal process completely avoids damage such as lattice distortion, microcracks, or phase transitions caused by mechanical friction. This removal principle based on chemical bond reconstruction is theoretically applicable to all hard materials that can undergo controllable chemical reactions with active substances, providing a universal solution for obtaining ultra-smooth surfaces with intrinsic crystal integrity in fields such as optics and semiconductors.

[0018] (2) The flexible contact allows the polishing belt to better adapt to the shape changes of the workpiece surface. The core of this is the synergistic effect of the elastic deformation capability of the carrier substrate and the dynamic pressure control system: when in contact with a non-planar surface, the flexible layer can conform to the shape and compensate for the gap difference caused by the curvature change in real time; through the real-time feedback of the pressure sensor, when the pressure in the raised area increases, X Y The Z-axis three-axis motion platform drives the composite polishing belt to move along the Y-axis, achieving automatic pressure reduction to prevent over-polishing. When the pressure decreases in the concave area, the X-axis... Y The Z-axis motion platform drives the composite polishing belt to move along the Y-axis, achieving automatic pressure increase to ensure sufficient contact. This flexible polishing method eliminates the edge effects and surface distortion caused by "point contact" or "line contact" of traditional rigid tools, and achieves consistent polishing of the entire surface of complex components such as free-form surfaces and off-axis aspherical surfaces.

[0019] (3) Introducing a periodic physical renewal mechanism for the catalyst: During continuous operation, a correction wheel automatically removes the reaction byproduct accumulation layer and oxide coating on the catalyst surface, continuously exposing fresh active sites. This constructs a metabolic cycle system for the catalyst, ensuring that the catalytic activity is always maintained close to the initial level. This mechanism ensures industrial-grade stability in the ultra-precision polishing process, providing a reliable mass production guarantee for high-value-added products such as wafers and infrared windows that require long-term continuous processing.

[0020] (4) The processing method proposed in this invention has wide applicability to materials. By replacing traditional abrasives with catalysts, its processing capability is no longer limited by the mechanical properties of the workpiece material, but depends on whether the material has chemical properties that can undergo hydrolysis. This enables uniform and low-damage processing of a variety of materials with different properties, from optical glass to hard and brittle semiconductors, breaking through the limitations of traditional mechanical polishing methods in adapting to material hardness.

[0021] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the overall structure of the ultra-smooth surface polishing device for complex curved optical elements according to the present invention. Figure 2 This is a side view of an ultra-smooth surface polishing device for complex curved optical elements according to the present invention; Figure 3 This is a schematic diagram of the connection structure of the drive mechanism and the composite polishing belt of an ultra-smooth surface polishing device for complex curved optical elements according to the present invention. Figure 4 for Figure 3The enlarged structural diagram at point a is a schematic diagram of the composite polishing belt. Figure 5 This is a process flow diagram of an ultra-smooth surface polishing process for complex curved optical elements according to the present invention. Figure 6 The figures show a comparison of the surface roughness test results of the workpiece before and after polishing using the ultra-smooth surface polishing process of the present invention. In the figure, a is the roughness test result before polishing; b is the roughness test result after polishing.

[0023] Reference numerals: 1. Solution tank; 2. Workpiece fixture; 3. Workpiece to be polished; 4. Composite polishing belt; 5. Drive wheel; 6. Contact wheel; 7. Tensioning wheel; 8. Dressing wheel; 9. X Y Z-axis motion platform; 41. Bearing layer; 42. Buffer layer; 43. Catalytic layer. Detailed Implementation

[0024] To better understand the above technical solutions, a detailed description of the solutions will be provided below in conjunction with the accompanying drawings and specific embodiments. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0025] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a,” “the,” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms, and “multiple” generally includes at least two unless the context clearly indicates otherwise.

[0026] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that an article or device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or device. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or device that includes said element.

[0027] like Figures 1-4 As shown, the present invention provides an ultra-smooth surface polishing device for complex curved optical elements, comprising: Solution tank 1 is used to contain the polishing solution. The polishing solution is an acidic or neutral hydrogen peroxide mixture, specifically formulated as follows: deionized water, 3%-10% (v / v) H₂O₂, and 0.1 mol / L H₂SO₄ or HCl, with the pH adjusted to 3-5. H₂O₂ is a source of hydroxyl radicals; a concentration below 3% results in a slow reaction rate, while a concentration above 10% may lead to an uncontrollable and economically unfeasible reaction. An acidic environment stabilizes H₂O₂, inhibiting its rapid decomposition and facilitating the dissolution of certain metal oxide reaction products.

[0028] The workpiece clamp 2 is fixed in the solution tank 1 and is used to fix the workpiece 3 to be polished. The workpiece clamp 2 uses at least one of glue, clay or asphalt to fix the workpiece 3 to be polished, and the workpiece 3 to be polished remains stationary during the polishing process. The composite polishing belt 4 has a three-layer composite structure, consisting of a support layer 41, a buffer layer 42, and a catalyst layer 43 from the substrate to the working surface. The composite polishing belt 4 is placed above the workpiece 3 to be polished. The bearing layer 41 has a thickness of 0.5-1.5mm and is made of polyester fiber or cotton cloth matrix and Al2O3 or SiC abrasive with a particle size of 5-30μm. This layer mainly provides structural strength and the main mechanical support for the polishing process, ensuring the overall strength and durability of the polishing belt.

[0029] The buffer layer 42 has a thickness of 1.0-3.0 mm, a hardness of 60-80 Shore A, and an elastic modulus in the range of 10-100 MPa. It is bonded to the bearing layer by coating or hot pressing. The moderate hardness can provide sufficient support to prevent excessive collapse at the high point of the curved surface, and also has a certain degree of flexibility to adapt to the contour changes of complex curved surfaces, so as to achieve flexible bonding of surface contact or large contact area.

[0030] The catalyst layer 43, with a thickness of 100-300 nm, is a metal catalyst film prepared by magnetron sputtering or electrochemical deposition, or a bonded metal catalyst foil; preferably platinum or nickel, which exhibit high catalytic efficiency in solutions such as hydrogen peroxide and can effectively decompose to generate hydroxyl radicals. The thickness of this layer must ensure sufficient catalytic active sites; excessive thickness will increase the film's brittleness and make it prone to peeling, while insufficient thickness will result in insufficient catalytic lifetime. The three layers are hot-pressed together using a high-performance polyurethane adhesive to ensure no delamination occurs during dynamic polishing.

[0031] The driving mechanism includes a composite polishing belt 4 mounted on it. The driving mechanism drives the composite polishing belt 4 to move, achieving relative movement with the surface of the workpiece 3 to be polished. The driving mechanism includes a drive wheel 5, a contact wheel 6, and a tension wheel 7. The drive wheel 5 drives the contact wheel 6 to rotate via a motor. The contact wheel 6 is covered with polyurethane with a hardness of 60-80 Shore A and a wheel diameter of 20-50 mm. The polyurethane coating with the same or similar hardness as the buffer layer of the polishing belt can further amplify the flexibility of the polishing belt and form a uniform and stable contact pressure with the curved surface of the workpiece. It enables the composite polishing belt 4 to contact the surface of the workpiece, and its flexible coating helps to evenly distribute the polishing pressure.

[0032] The dressing wheel 8, made of hard material, is positioned on one side of the composite polishing belt 4 and is used to intermittently scrape the surface of the catalyst layer of the composite polishing belt 4. The dressing wheel 8 is a diamond dressing wheel or a carbide wheel with a finely textured surface. It is equipped with a feeding mechanism to move the dressing wheel 8 in contact with and away from the composite polishing belt 4. The dressing wheel 8 is driven by a motor to rotate, performing a scraping action lasting 5-10 seconds every 10 minutes of processing. The feeding mechanism uses a cylinder or ball screw slide combined with a servo motor and linear guide rail. During catalytic polishing, the surface of the metal catalyst layer may form a passivation film due to adsorption of reaction products or slight oxidation, leading to a decrease in catalytic efficiency. The dressing wheel 8, through periodic feeding, lightly touches and scrapes away the passivation layer on the outermost surface of the catalyst layer, exposing a fresh, highly active catalyst surface, thereby maintaining the long-term stability of the material removal rate.

[0033] X Y Z-axis three-axis motion platform 9, the drive mechanism is located at X Y On the Z-axis motion platform 9, X Y The Z-axis motion platform 9 is used to drive the drive mechanism and the dressing wheel 8 to move along the X, Y, and Z axes, achieving full-envelope polishing of complex curved optical components; X Y Z-axis motion platform 9 uses cylinders or ball screw slides combined with servo motors and linear guides. The positioning system, including a non-contact laser displacement sensor or laser tracker, is used to scan the curved surface of the workpiece to be polished and generate a pose compensation file. Before processing, the non-contact laser displacement sensor or laser tracker is removed and set at the same height as the bottom of the current composite polishing belt. A high-density point cloud scan is performed on the workpiece fixed in the solution tank 1. Alternatively, before fixing the workpiece, the non-contact laser displacement sensor or laser tracker is used to scan the curved surface of the workpiece. The actual curved surface is then fitted and compared with the theoretical CAD model to generate a pose compensation file containing surface normal information. This file is used to adjust the posture of the polishing head in real time during subsequent polishing, ensuring that the polishing belt always maintains optimal contact with the workpiece surface. Precise positioning of the composite polishing belt and the workpiece is achieved through the non-contact laser displacement sensor or laser tracker.

[0034] It also includes a pressure control system, which uses a pressure sensor mounted on the 6-axis of the contact wheel for closed-loop feedback control to dynamically adjust the polishing pressure according to the curvature of the workpiece.

[0035] The working principle of this processing device is as follows: During processing, the workpiece 3 to be polished is first placed in a solution. The drive wheel 5 drives the contact wheel 6 to rotate, thus ensuring relative movement between the polishing belt and the workpiece surface. Because the polishing belt surface is coated with a catalytic layer, the catalyst can dissociate the solution components to generate activators, namely hydroxyl radicals. These hydroxyl radicals react chemically with surface atoms to form chemical bonds. These bonds weaken the bonding force between surface atoms and substrate atoms. As the polishing belt rotates, surface atoms are removed. Based on the above analysis, material removal only occurs within the catalytic region. Since the catalytic region is very thin, only the outermost atoms are removed, resulting in extremely low surface roughness. Furthermore, because material removal during processing is based on a chemical reaction process, the processed surface will not introduce scratches or damage.

[0036] This technology uses a flexible polishing belt as a carrier, and the contact wheel 6 and the buffer layer of the polishing belt are made of a flexible polyurethane layer, which ensures that the processing method has good processing flexibility, thus adapting to the surface polishing of flat, curved, and complex shaped components. At the same time, since the rate of catalytic etching is usually related to the reaction contact area and the density of reactive sites, the dressing wheel 8 in the device can ensure the real-time renewal of the surface of the metal catalyst layer, so as to prevent the catalyst surface from reducing the catalytic efficiency due to oxidation and other reasons, thereby ensuring the catalytic efficiency and the stability of material removal during the processing.

[0037] like Figure 5 As shown, a polishing process for an ultra-smooth surface device for complex curved optical elements is provided, comprising the following steps: Step 1: Pre-treatment and cleaning of the workpiece. The workpiece 3 to be polished is ultrasonically cleaned for 10 minutes each in acetone, anhydrous ethanol and deionized water, and then dried with high-purity nitrogen gas to ensure that there are no organic pollutants, particles and moisture on the surface.

[0038] Step 2: Workpiece clamping and spatial positioning. Use workpiece fixture 2 to fix the workpiece 3 to be polished in solution tank 1. Start the laser tracker or non-contact laser displacement sensor to scan the workpiece surface and generate high-precision point cloud data. Align the actual surface with the theoretical model using software, and fit to generate a CNC compensation file containing spatial position and normal information to complete precise spatial positioning.

[0039] Step 3: Process parameter planning and CNC code generation. In the CAM software, the polishing path is planned according to the workpiece surface geometry, and the polishing pressure is dynamically adjusted. The path, pressure parameters, spindle speed, and the intermittent action program of the dressing wheel 8 are integrated into the CNC program. The polishing path is a grating path or an Archimedean spiral path with equal residual height, and the path step is 1 / 5 to 1 / 3 of the polishing strip contact width. The polishing pressure is 0.5-2 psi in convex curved areas with small curvature radius and 2-5 psi in flat or large curvature areas. Closed-loop feedback control is performed through a pressure sensor installed on the contact wheel 6 axis. In convex curved areas with small curvature radius, a lower pressure is used to prevent over-polishing; in flat or large curvature radius areas, a slightly higher pressure is used to improve efficiency.

[0040] Step 4: Inject the solution and perform polishing. Inject polishing solution into solution tank 1, start the drive mechanism to drive the composite polishing belt 4 to move, via X Y The Z-axis motion platform 9 drives the drive mechanism to move along the planned trajectory, and the dressing wheel 8 performs catalyst surface renewal actions according to a preset cycle, continuously polishing until the predetermined time is reached; the intermittent action program of the dressing wheel 8 is to perform a scraping action lasting 5-10 seconds every 10 minutes of polishing. The drive wheel 5 drives the composite polishing belt 4 to move at a set speed; the multi-axis motion platform drives the workpiece to move along the planned trajectory and adjusts its posture in real time according to the compensation file; the pressure control system maintains the set dynamic polishing pressure; the dressing wheel 8 automatically performs catalyst surface renewal actions according to a preset cycle; the entire polishing process continues until the predetermined time is reached.

[0041] Step 5: Post-processing and inspection. Remove the workpiece and ultrasonically clean it with deionized water. After drying it with nitrogen, measure the surface roughness using a white light interferometer or atomic force microscope.

[0042] like Figure 6The image shows a roughness comparison of the workpiece 3 before and after polishing using the polishing device and process of this invention. It is evident that the ultra-smooth surface polishing device and process proposed in this invention for complex curved optical components can significantly reduce the surface roughness of the workpiece. From the core surface roughness index, the roughness is reduced to within 5×5μm. 2 Within the detection area, the surface roughness parameters of the workpiece before processing were RMS 0.705nm and Ra 0.446nm, while after processing, RMS dropped to 0.0663nm and Ra dropped to 0.0517nm. Both achieved a significant reduction of more than an order of magnitude. Moreover, the Ra after processing was far below the stringent surface quality requirements of extreme ultraviolet lithography objective lenses and short-wavelength optical components, reaching the sub-nanometer level of ultra-smoothness.

[0043] In terms of surface contour smoothness, the fluctuation range of the height difference on the workpiece surface before processing was -3.8nm to 2.2nm, and the fluctuation range after processing was narrowed to -248.2pm to 238.2pm. The microscopic protrusions and depressions on the surface were effectively smoothed out, proving that the polishing technology can accurately eliminate high-frequency microscopic undulations on the surface through atomic-level removal dominated by catalytic reaction and flexible bonding polishing, thus avoiding the surface contour distortion caused by traditional mechanical polishing.

[0044] Therefore, this invention employs the aforementioned ultra-smooth surface polishing device and process for complex curved optical elements, transforming the material removal mechanism from traditional mechanical force-dominated to chemical reaction-dominated. Through the interaction of a specially designed catalyst and solution system, highly reactive chemical substances are activated in situ on the workpiece surface. These reactive substances selectively form weakly bonded intermediate states with surface atoms, significantly reducing the interatomic binding energy. When external force is applied, the weakened atomic layers detach from the substrate with near-zero stress, achieving atomic-scale layer-by-layer peeling. Because the reaction depth is precisely controlled at the level of a single atomic layer, and the effective range is strictly limited to the catalyst contact area, the material removal process completely avoids damage such as lattice distortion, microcracks, or phase transitions caused by mechanical friction. This removal principle based on chemical bond reconstruction is theoretically applicable to all hard materials capable of undergoing controllable chemical reactions with reactive substances, providing a universal solution for obtaining ultra-smooth surfaces with intrinsic crystal integrity in fields such as optics and semiconductors.

[0045] The use of flexible contact allows the polishing belt to better adapt to changes in the shape of the workpiece surface. Its core lies in the synergistic effect of the carrier substrate's elastic deformation capability and the dynamic pressure control system: when contacting a non-planar surface, the flexible layer can conform to the shape, compensating in real time for gap differences caused by curvature changes; through real-time feedback from pressure sensors, when the pressure increases in raised areas, X... Y The Z-axis three-axis motion platform drives the composite polishing belt to move along the Y-axis, achieving automatic pressure reduction to prevent over-polishing. When the pressure decreases in the concave area, the X-axis... Y The Z-axis motion platform drives the composite polishing belt to move along the Y-axis, achieving automatic pressure increase to ensure sufficient contact. This flexible polishing method eliminates the edge effects and surface distortion caused by "point contact" or "line contact" of traditional rigid tools, and achieves consistent polishing of the entire surface of complex components such as free-form surfaces and off-axis aspherical surfaces.

[0046] A periodic physical renewal mechanism is introduced for the catalyst: during continuous operation, a correction wheel automatically removes the accumulation of reaction byproducts and oxide coatings on the catalyst surface, continuously exposing fresh active sites. This establishes a metabolic cycle system for the catalyst, ensuring that its catalytic activity remains close to its initial level. This mechanism ensures industrial-grade stability in the ultra-precision polishing process, providing reliable mass production assurance for high-value-added products such as wafers and infrared windows that require long-term continuous processing.

[0047] The processing method proposed in this invention has broad material applicability. By replacing traditional abrasives with catalysts, its processing capability is no longer limited by the mechanical properties of the workpiece material, but rather depends on whether the material has chemical properties that allow for hydrolysis. This enables uniform and low-damage processing of a variety of materials with diverse properties, from optical glass to hard and brittle semiconductors, overcoming the limitations of traditional mechanical polishing methods in adapting to material hardness.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A polishing device for ultra-smooth surfaces of complex curved optical elements, characterized in that, include: Solution tank, used to hold polishing solution; A workpiece clamp is fixed inside the solution tank to hold the workpiece to be polished. The composite polishing belt has a three-layer composite structure, consisting of a support layer, a buffer layer, and a catalyst layer from the substrate to the working surface. The composite polishing belt is placed above the workpiece to be polished. The driving mechanism, on which the composite polishing belt is sleeved, drives the composite polishing belt to move, thereby achieving relative movement with the surface of the workpiece to be polished; A dressing wheel is positioned on one side of the composite polishing belt to intermittently renew the surface of the catalyst layer of the composite polishing belt. X Y Z-axis three-axis motion platform, the drive mechanism is located at X Y On the Z-axis motion platform, X Y The Z-axis motion platform is used to drive the drive mechanism and the dressing wheel to move along the X, Y, and Z axes to achieve full-envelope polishing of complex curved optical components. The positioning system, including a non-contact laser displacement sensor or laser tracker, is used to scan the curved surface of the workpiece to be polished and generate a pose compensation file.

2. The ultra-smooth surface polishing device for complex curved optical elements according to claim 1, characterized in that, The bearing layer has a thickness of 0.5-1.5 mm and is made of polyester fiber or cotton fabric matrix and Al2O3 or SiC abrasive with a particle size of 5-30 μm.

3. The ultra-smooth surface polishing device for complex curved optical elements according to claim 1, characterized in that, The buffer layer has a thickness of 1.0-3.0 mm, a hardness of 60-80 Shore A, and an elastic modulus in the range of 10-100 MPa. It is bonded to the bearing layer by coating or hot pressing.

4. The ultra-smooth surface polishing device for complex curved optical elements according to claim 1, characterized in that, The catalyst layer has a thickness of 100-300 nm and is a metal catalyst film prepared by magnetron sputtering or electrochemical deposition, or a bonded metal catalyst foil.

5. The ultra-smooth surface polishing device for complex curved optical elements according to claim 1, characterized in that, The drive mechanism includes a drive wheel, a contact wheel, and a tension wheel. The drive wheel drives the contact wheel to rotate via a motor. The outer layer of the contact wheel is covered with polyurethane with a hardness of 60-80 Shore A and a wheel diameter of 20-50 mm.

6. The ultra-smooth surface polishing device for complex curved optical elements according to claim 1, characterized in that, The dressing wheel is a diamond dressing wheel or a carbide wheel with a fine texture on its surface. The dressing wheel is equipped with a feeding mechanism to drive the dressing wheel to contact and move away from the composite polishing belt. The dressing wheel is driven to rotate by a motor and performs a scraping action for 5-10 seconds every 10 minutes of processing.

7. The ultra-smooth surface polishing apparatus for complex curved optical elements according to claim 1, characterized in that, The polishing solution is an acidic or neutral hydrogen peroxide mixture, specifically formulated as follows: deionized water, 3%-10% (v / v) H₂O₂, and 0.1 mol / L hydrogen peroxide. Add L of H2SO4 or HCl, and adjust the pH to 3-5.

8. The ultra-smooth surface polishing device for complex curved optical elements according to claim 1, characterized in that, It also includes a pressure control system, which uses a pressure sensor mounted on the contact wheel shaft for closed-loop feedback control to dynamically adjust the polishing pressure according to the workpiece curvature.

9. A polishing process for an ultra-smooth surface of an optical element with complex curved surfaces as described in any one of claims 1-8, characterized in that, Includes the following steps: Step 1: Pre-treatment and cleaning of the workpiece. The workpiece to be polished is ultrasonically cleaned for 10 minutes each in acetone, anhydrous ethanol and deionized water, and then dried with high-purity nitrogen. Step 2: Workpiece clamping and spatial positioning. Use a workpiece fixture to fix the workpiece to be polished in the solution tank. Scan the workpiece surface through the positioning system to generate high-precision point cloud data, and fit it to generate a pose compensation file. Step 3: Process parameter planning and CNC code generation. Based on the workpiece's surface geometry, plan the polishing path and dynamically adjust the polishing pressure. Integrate the path, pressure parameters, spindle speed, and dressing wheel intermittent motion program into the CNC program. The polishing path is either a grating path with equal residual height or an Archimedean spiral path, with a path step size equal to 1 / 3 of the polishing strip contact width. 5 to 1 3. Polishing pressure is 0.5-2 psi in convex curved areas with small radius of curvature, and 2-5 psi in flat areas or areas with large radius of curvature. Step 4: Inject the solution and perform polishing. Inject polishing solution into the solution tank, start the drive mechanism to move the composite polishing belt, and move it via X. Y The Z-axis motion platform drives the drive mechanism to move along the planned trajectory, and the dressing wheel performs catalyst surface renewal actions according to the preset cycle, continuously polishing until the predetermined time. Step 5: Post-processing and inspection. Remove the workpiece and ultrasonically clean it with deionized water. After drying it with nitrogen, measure the surface roughness using a white light interferometer or atomic force microscope.

10. The ultra-smooth surface polishing process for complex curved optical elements according to claim 9, characterized in that, The intermittent operation procedure of the dressing wheel in step 4 is to perform a scraping action lasting 5-10 seconds every 10 minutes of polishing.

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