A method for high-efficiency composite processing of aspheric optical elements

Abstract

A method for high-efficiency composite machining of aspherical optical components includes the following steps: fabricating a fixture according to the shape of the optical component to be processed; grinding and polishing the lower surface of the optical component blank and fixing it on the fixture; performing aspherical forming machining on the upper surface of the optical component blank through rough grinding and fine grinding to obtain an aspherical sample; measuring the surface shape data of the aspherical sample using a profilometer; importing the surface shape data into an airbag polishing machine to calculate the NC code for compensation machining; fixing the fixture and the aspherical sample together on the transition fixture of the polishing machine; and performing rough and fine polishing on the upper surface of the aspherical sample using different airbag polishing heads; after machining, measuring the surface shape data of the aspherical sample using a profilometer; after passing the test, immersing the aspherical sample and fixture in an acetone solution and then removing the sample. This invention features a scientifically sound process that enables rapid measurement of the component's surface shape, reduces clamping errors, improves machining quality and efficiency, and lowers production costs.

Description

Technical Field

[0001] This invention belongs to the field of optical component processing and manufacturing technology, and relates to a method for high-efficiency composite processing of aspherical optical components. Background Technology

[0002] Aspherical optical elements are widely used in lenses and windows of various optical instruments due to their excellent optical imaging quality and reduced weight. Existing processing methods employ traditional grinding followed by die polishing, which has the following drawbacks:

[0003] First, the surface quality during the grinding process is difficult to control consistently, which affects the subsequent polishing and removal time to some extent.

[0004] Second, the polishing process requires precise molds, but these molds are prone to wear, which reduces the polishing quality. As a result, the processing efficiency is low and the cost is high, which severely limits the application of aspherical optical components.

[0005] Therefore, it is necessary to propose an innovative technical solution to improve product quality and processing efficiency. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a method for high-efficiency composite processing of aspherical optical elements, which has the characteristics of high processing efficiency, good product quality, and simplicity and practicality.

[0007] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: a method for high-efficiency composite processing of aspherical optical elements, characterized by comprising the following steps:

[0008] 1) Make tooling fixtures according to the shape of the optical element to be processed, grind and polish the lower surface of the optical element blank, and fix it to the tooling fixture with glue. The tooling fixture is fixed on the transition fixture of the grinding machine tool.

[0009] 2) The upper surface of the optical element blank is aspherically shaped by rough grinding and fine grinding to obtain an aspherical sample;

[0010] 3) The surface shape data of the aspherical sample was measured using a profilometer;

[0011] 4) Import the surface shape data of the aspherical sample into the airbag polishing machine, calculate the NC code for compensation machining, and fix the tooling fixture and the aspherical sample together on the transition fixture of the polishing machine.

[0012] 5) Use different airbag polishing heads to perform rough polishing and fine polishing on the upper surface of the aspherical sample;

[0013] 6) After processing, use a profilometer to measure the surface shape data of the aspherical sample. If it is qualified, immerse the aspherical sample and tooling fixture in acetone solution and take out the sample.

[0014] As an improvement, the lower surface of the optical element to be processed in step 1) is a plane, and the upper surface is an aspherical surface. The tooling fixture is divided into two parts, the lower part is a cylindrical structure that fits into the inner hole of the transition fixture, and the upper part is an expanded cylindrical structure. The upper end face of the upper part is a plane, and the side of the upper end face near the inner ring is formed into a concave spherical surface that fits into the upper surface of the optical element to be processed.

[0015] Furthermore, the lower cylindrical structure of the tooling fixture has a central hole coaxial with the upper part, and the transition fixture is a hollow inverted T-shaped cylindrical structure. The diameter of the lower cylindrical structure of the tooling fixture is the same as the inner diameter of the transition fixture. The lower part of the tooling fixture is inserted into the transition fixture and positioned by abutting against the upper end face of the transition fixture through a stepped surface. The stepped surface is provided with a positioning protrusion extending horizontally outward.

[0016] Furthermore, the specific process of grinding and polishing the lower surface of the optical element blank in step 1) is as follows: the upper surface of the optical element blank is fixed on the tooling fixture by hot melt adhesive, and the position of the optical element blank is adjusted by dial gauge so that the center of the optical element blank is aligned with the center of the tooling fixture. The tooling fixture is installed on the transition fixture of the workpiece shaft of the grinding machine for fixation, and the lower surface is ground and polished.

[0017] Furthermore, in step 1), after grinding and polishing the lower surface of the optical element blank to meet the drawing requirements, a protective varnish is applied to the lower surface. Hot melt adhesive is used to fix the lower surface to the tooling fixture, and the position of the optical element blank is adjusted by dial indicator. The dial indicator is aligned with the cylindrical positioning surface on the outer side of the optical element blank. Before the adhesive layer cools, the position of the optical element blank is adjusted so that the circumferential runout error of the optical element blank is less than 2μm, so that the center of the optical element blank is aligned with the center of the tooling fixture. The tooling fixture is placed in the transition fixture on the workpiece shaft of the grinding machine for fixation.

[0018] Preferably, the specific process of rough grinding + fine grinding in step 2) is as follows: A metal-based circular arc grinding wheel is used to rough grind the upper surface of the optical element blank to form an aspherical shape. The grinding wheel diameter is selected as 120mm±10mm, and the arc radius is less than 50mm. The rough grinding process parameters are as follows: grinding wheel speed 6000±500rpm, element blank speed 60±10rpm, cutting depth 0.1±0.01mm, and feed rate 0.05±0.005mm / rev. A resin-based circular arc grinding wheel is used to fine grind the element. The grinding wheel diameter is selected as 120±10mm, and the arc radius is less than 50±5mm. The fine grinding process parameters are as follows: grinding wheel speed 6000±500rpm, element blank speed 60±10rpm, cutting depth 0.02±0.001mm, and feed rate 0.02±0.001mm / rev, resulting in a finely ground aspherical sample.

[0019] Furthermore, the specific process of step 3) is as follows: the surface shape of the element is detected in situ using a spectral confocal displacement sensor, the surface shape of the element is obtained by measuring the generatrix of the aspherical profile, and the surface shape error of the aspherical surface is determined by the deviation between the actual profile and the aspherical equation.

[0020] Furthermore, in step 5), the airbag polishing head is a semi-flexible airbag polishing head, and the rough polishing process parameters are: polishing head speed 900±100rpm, sample speed 800±100rpm, airbag pressure 1.2±0.1MPa, compression amount 0.1±0.01mm, and polishing pad diameter 32±3mm.

[0021] The fine polishing process parameters are as follows: polishing head speed 900±100rpm, sample speed 800±100rpm, airbag pressure 1.2±0.1MPa, compression amount 0.1±0.01mm, and polishing pad diameter 16±1mm.

[0022] Finally, the aspherical optical element is an axisymmetric aspherical optical element with a diameter of less than 120 mm and a surface shape error requirement of <0.5 μm.

[0023] Compared with existing technologies, the advantages of this invention are as follows: By establishing a process flow of rough grinding-fine grinding-airbag rough polishing-airbag fine polishing, the processing flow of aspherical optical components is optimized and improved. A spectral confocal displacement sensor is used for in-situ detection of the surface shape of the ground component, and an airbag polishing method is employed to improve polishing efficiency. Dedicated tooling fixtures are designed to reduce fixture change time, clamping errors, and clamping time. The processing technology of this invention is scientifically sound and reasonable, enabling rapid measurement of the component surface shape during grinding and reducing clamping errors. This significantly improves the processing quality and efficiency of aspherical optical components, reduces production costs, and is particularly suitable for processing axisymmetric aspherical optical components with a diameter of less than 120mm and a surface shape accuracy requirement of less than 0.5μm. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the structure of the dial indicator clamped with the lower surface facing upward, according to an embodiment of the present invention;

[0025] Figure 2 This is a cross-sectional view of the structure after clamping with the lower surface facing upward, as provided in an embodiment of the present invention;

[0026] Figure 3 This is a cross-sectional view of the structure after clamping with the upper surface facing upward, provided in an embodiment of the present invention;

[0027] Figure 4 This is a structural cross-sectional view of the tooling fixture provided in the embodiment of the present invention;

[0028] Figure 5 This is a schematic diagram of the structure of the optical element to be processed provided in an embodiment of the present invention;

[0029] Figure 6 This is a schematic diagram of the structure for detecting the upper surface in situ provided in an embodiment of the present invention;

[0030] The components include: 1. tooling fixtures, 2. optical components, 3. transition fixtures, 4. dial indicator, 5. adhesive layer, and 6. spectral confocal displacement sensor. Detailed Implementation

[0031] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0032] like Figures 1-6 As shown, a method for high-efficiency composite fabrication of aspherical optical elements includes the following steps:

[0033] 1. Make tooling fixtures according to the shape of the optical element to be processed: The lower surface 2-2 of the optical element 2 to be processed is a plane, and the upper surface 2-1 is an aspherical surface. The tooling fixture 1 is divided into two parts, the lower part is a cylindrical structure 1-3 that fits into the inner hole of the transition fixture, and the upper part is an expanded cylindrical structure. The upper end face 1-2 of the upper part is a plane, and the side of the upper end face near the inner circle is formed into a concave spherical surface 1-1 that fits into the upper surface of the optical element 2 to be processed. The lower cylindrical structure 1-3 of the tooling fixture 1 has a central hole coaxial with the upper part. The transition fixture 3 is a hollow inverted T-shaped cylindrical structure. The diameter of the lower cylindrical structure 1-3 of the tooling fixture 1 is consistent with the inner diameter of the transition fixture 3, which can ensure that the tooling fixture 1 can be installed in the transition fixture 3. The lower part of the tooling fixture 1 is inserted into the transition fixture 3 and is positioned by abutting against the upper end face of the transition fixture 3 through the stepped surface 1-4. The stepped surface 1-4 is provided with a positioning protrusion extending horizontally outward. The stepped surface 1-4 is perpendicular to the cylindrical structure 1-3, ensuring that the clamping center of the tooling fixture 1 and the center of the transition fixture 3 are on a straight line.

[0034] 2. Grind and polish the lower surface 2-2 of the optical element 2 blank, and fix it to the tooling fixture 1 with adhesive. The tooling fixture 1 is fixed to the transition fixture 3 of the grinding machine. First, fix the upper surface 2-1 of the optical element 2 blank to the tooling fixture 1 with hot melt adhesive as the adhesive layer 5. Adjust the position of the optical element 2 blank by dialing so that the center of the optical element 2 blank is aligned with the center of the tooling fixture 1. The tooling fixture 1 is installed into the transition fixture 3 of the workpiece shaft of the grinding machine for fixation. Grind and polish the lower surface 2-2. After the lower surface 2-2 is ground and polished to meet the requirements of the drawing, a protective paint is applied to the lower surface 2-2. The lower surface 2-2 is fixed to the tooling fixture 1 using a hot melt adhesive layer 5. The position of the optical element 2 blank is adjusted by dialing. The dial indicator 4 is aligned with the cylindrical positioning surface 2-3 on the outer side of the optical element 2 blank. Before the adhesive layer 5 cools, the position of the optical element 2 blank is adjusted so that the circumferential runout error of the optical element 2 blank is less than 2μm, so that the center of the optical element 2 blank is aligned with the center of the tooling fixture 1. The tooling fixture 1 is placed in the transition fixture 3 on the workpiece shaft of the grinding machine for fixation.

[0035] 3. The upper surface 2-1 of the optical element 2 blank is formed by rough grinding and fine grinding to obtain an aspherical sample: The upper surface of the blank is formed by rough grinding with a metal-based circular arc grinding wheel. The grinding wheel diameter is selected as 120mm and the arc radius is less than 50mm. The rough grinding process parameters are as follows: grinding wheel speed 6000rpm, element blank speed 60rpm, cutting depth 0.1mm, and feed rate 0.05mm / rev.

[0036] The component was precision ground using a resin-based circular arc grinding wheel with a diameter of 120mm and a radius of less than 50mm. The precision grinding process parameters were as follows: grinding wheel speed 6000rpm, component blank speed 60rpm, cutting depth 0.02mm, and feed rate 0.02mm / rev, to obtain a precision ground aspherical sample.

[0037] IV. Measuring the surface shape data of aspherical samples using a profilometer: The surface shape of the element is detected in situ using a spectral confocal displacement sensor 6. The surface shape of the element is obtained by measuring the generatrix of the aspherical profile. The surface shape error of the aspherical surface is determined by the deviation between the actual profile line and the aspherical equation.

[0038] 5. Import the surface shape data of the aspherical sample into the airbag polishing machine, calculate the NC code for compensation machining, which is the numerical control code, and fix the tooling fixture and the aspherical sample together on the transition fixture of the polishing machine; import the component surface shape error data obtained by in-place detection into the airbag polishing machine, calculate the NC code for polishing compensation machining, and remove the fixture and sample from the grinding machine and place them in the hydraulic expansion fixture on the workpiece shaft of the polishing machine for fixation.

[0039] VI. Rough and fine polishing of the upper surface of the aspherical sample using different airbag polishing heads: The airbag polishing head is a semi-flexible airbag polishing head. The rough polishing process parameters are: polishing head speed 900 rpm, sample speed 800 rpm, airbag pressure 1.2 MPa, compression amount 0.1 mm, polishing pad diameter 32 mm.

[0040] The fine polishing process parameters are: polishing head speed 900 rpm, sample speed 800 rpm, airbag pressure 1.2 MPa, compression amount 0.1 mm, and polishing pad diameter 16 mm.

[0041] 7. After processing, use a profilometer to measure the surface shape data of the aspherical sample. If it is qualified, immerse the aspherical sample and tooling fixture in acetone solution, remove the sample from tooling fixture 1, take out the sample, and clean the surface of the sample with alcohol.

[0042] The invention adopts a process flow of rough grinding-fine grinding-airbag rough polishing-airbag fine polishing to optimize and improve the processing flow of aspherical optical components. It also designs special tooling fixtures to reduce fixture change time, clamping errors and clamping time. A spectral confocal displacement sensor is used to detect the surface shape of the ground components in situ, and an airbag polishing method is used to improve polishing efficiency.

[0043] This invention enables rapid measurement of the surface shape of components during grinding, effectively improving the processing quality and efficiency of aspherical optical components and reducing production costs. This invention is particularly suitable for processing axisymmetric aspherical optical components with a diameter of less than 120mm and a surface shape accuracy requirement of less than 0.5μm.

[0044] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for high-efficiency composite fabrication of aspherical optical elements, characterized in that... Includes the following steps: 1) Make tooling fixtures according to the shape of the optical element to be processed, grind and polish the lower surface of the optical element blank, and fix it to the tooling fixture with adhesive. The tooling fixture is fixed on the transition fixture of the grinding machine tool. 2) The upper surface of the optical element blank is aspherically shaped by rough grinding and fine grinding to obtain an aspherical sample; 3) The surface shape data of the aspherical sample was measured using a profilometer; 4) Import the surface shape data of the aspherical sample into the airbag polishing machine, calculate the NC code for compensation machining, and fix the tooling fixture and the aspherical sample together on the transition fixture of the polishing machine. 5) Use different airbag polishing heads to perform rough polishing and fine polishing on the upper surface of the aspherical sample; 6) After processing, use a profilometer to measure the surface shape data of the aspherical sample. If it is qualified, immerse the aspherical sample and tooling fixture in acetone solution and take out the sample. The lower surface of the optical element to be processed in step 1) is a plane, and the upper surface is an aspherical surface. The tooling fixture is divided into two parts, the lower part is a cylindrical structure that fits into the inner hole of the transition fixture, and the upper part is an expanded cylindrical structure. The upper end face of the upper part is a plane, and the side of the upper end face near the inner ring is formed into a concave spherical surface that fits into the upper surface of the optical element to be processed. The lower cylindrical structure of the tooling fixture has a central hole coaxial with the upper part. The transition fixture is a hollow inverted T-shaped cylindrical structure. The diameter of the lower cylindrical structure of the tooling fixture is the same as the inner diameter of the transition fixture. The lower part of the tooling fixture is inserted into the transition fixture and positioned by abutting against the upper end face of the transition fixture through a stepped surface. The stepped surface is provided with a positioning protrusion extending horizontally outward. The airbag polishing head in step 5) is a semi-flexible airbag polishing head. The rough polishing process parameters are: polishing head speed 900±100rpm, sample speed 800±100rpm, airbag pressure 1.2±0.1MPa, compression amount 0.1±0.01mm, and polishing pad diameter 32±3mm. The fine polishing process parameters are as follows: polishing head speed 900±100rpm, sample speed 800±100rpm, airbag pressure 1.2±0.1MPa, compression amount 0.1±0.01mm, and polishing pad diameter 16±1mm.

2. The method according to claim 1, characterized in that: The specific process of grinding and polishing the lower surface of the optical element blank in step 1) is as follows: the upper surface of the optical element blank is fixed to the tooling fixture by hot melt adhesive, and the position of the optical element blank is adjusted by dial gauge so that the center of the optical element blank is aligned with the center of the tooling fixture. The tooling fixture is installed on the transition fixture of the workpiece shaft of the grinding machine for fixation, and the lower surface is ground and polished.

3. The method according to claim 2, characterized in that: In step 1), after grinding and polishing the lower surface of the optical element blank to meet the requirements of the drawing, a protective varnish is applied to the lower surface. Hot melt adhesive is used to fix the lower surface to the tooling fixture, and the position of the optical element blank is adjusted by dial indicator. The dial indicator is aligned with the cylindrical positioning surface on the outer side of the optical element blank. Before the adhesive layer cools, the position of the optical element blank is adjusted so that the circumferential runout error of the optical element blank is less than 2μm, so that the center of the optical element blank is aligned with the center of the tooling fixture. The tooling fixture is placed in the transition fixture on the workpiece axis of the grinding machine for fixation.

4. The method according to claim 1, characterized in that: The specific process of rough grinding + fine grinding in step 2) is as follows: A metal-based circular arc grinding wheel is used to rough grind the upper surface of the optical component blank to form an aspherical shape. The grinding wheel diameter is selected as 120mm±10mm, and the arc radius is less than 50mm. The rough grinding process parameters are as follows: grinding wheel speed 6000±500rpm, component blank speed 60±10rpm, cutting depth 0.1±0.01mm, and feed rate 0.05±0.005mm / rev. A resin-based circular arc grinding wheel is used to fine grind the component. The grinding wheel diameter is selected as 120±10mm, and the arc radius is less than 50±5mm. The fine grinding process parameters are as follows: grinding wheel speed 6000±500rpm, component blank speed 60±10rpm, cutting depth 0.02±0.001mm, and feed rate 0.02±0.001mm / rev, resulting in a finely ground aspherical sample.

5. The method according to claim 1, characterized in that: The specific process of step 3) is as follows: the surface shape of the element is detected in situ using a spectral confocal displacement sensor, the surface shape of the element is obtained by measuring the generatrix of the aspherical profile, and the surface shape error of the aspherical surface is determined by the deviation between the actual profile and the aspherical equation.

6. The method according to claim 1, characterized in that: The aspherical optical element is an axisymmetric aspherical optical element with a diameter of less than 120 mm and a surface shape error requirement of <0.5 μm.

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