Method for high-efficiency combined machining of aspheric optical element

Abstract

A method for high-efficiency combined machining of an aspheric optical element comprises the steps that a tool clamp is manufactured according to the shape of the optical element to be machined, the lower surface of an optical element blank is ground and polished, and the optical element blank is fixed to the tool clamp; performing aspheric surface forming processing on the upper surface of the optical element blank through rough grinding and accurate grinding to obtain an aspheric surface sample piece; measuring the surface shape data of the aspheric sample piece by using a contourgraph; the surface shape data are imported into an air bag polishing machine tool, an NC code for compensation machining is obtained through calculation, a tool clamp and the aspheric surface sample piece are fixed to a transition clamp of the polishing machine tool together, and rough polishing and fine polishing are conducted on the upper surface of the aspheric surface sample piece through different air bag polishing heads; and after machining is completed, measuring the surface shape data of the aspheric surface sample piece by adopting a contourgraph, soaking the aspheric surface sample piece and the tool clamp in an acetone solution after the aspheric surface sample piece is qualified, and taking out the sample piece. The process is scientific and reasonable, the surface shape of the element can be rapidly measured, the clamping error is reduced, the machining quality and the machining efficiency are improved, and the production cost is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of optical element processing and manufacturing, and relates to a method for high-efficiency composite processing of aspheric optical elements. Background Art

[0002] Aspheric optical components are widely used in various optical instrument lenses, windows, etc. due to their excellent optical imaging quality and reduced device weight structure. The existing processing method is to use the traditional grinding + mold polishing method, which has the following disadvantages:

[0003] 1. The surface quality during the grinding process is difficult to achieve stable control, which affects the subsequent polishing removal time to a certain extent;

[0004] Second, mold polishing requires precise molds, but the molds are easily worn and reduce the polishing quality, so the processing efficiency is low and the cost is high, which seriously limits the application of aspheric 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 aspheric optical elements, which has the characteristics of high processing efficiency, good product quality, simplicity and practicality.

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

[0008] 1) A jig is made according to the shape of the optical element to be processed, the lower surface of the optical element blank is ground and polished, and fixed to the jig by gluing, and the jig is fixed to the transition fixture of the grinding machine;

[0009] 2) Performing aspheric forming processing on the upper surface of the optical element blank by rough grinding + fine grinding to obtain an aspheric sample;

[0010] 3) Use a profilometer to measure the surface data of aspheric samples;

[0011] 4) Importing the surface data of the aspheric sample into the airbag polishing machine, calculating the NC code for compensation processing, and fixing the fixture and the aspheric 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 aspheric sample;

[0013] 6) After processing, use a profilometer to measure the surface data of the aspheric sample. If qualified, immerse the aspheric sample and the 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 fixture is divided into two parts, the lower part is a cylindrical structure that cooperates with 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 close to the inner ring is formed into a concave spherical surface that cooperates with the upper surface of the optical element to be processed.

[0015] Furthermore, the lower cylindrical structure of the tooling fixture has a center 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 consistent with the inner diameter of the transition fixture, the lower part of the tooling fixture is inserted into the transition fixture and is positioned against the upper end surface of the transition fixture through a step surface, and the step surface is provided with a positioning convex ring extending horizontally outward.

[0016] Furthermore, the specific process of grinding and polishing the lower surface of the optical element blank in step 1) is: fixing the upper surface of the optical element blank on the jig by gluing with hot melt adhesive, and adjusting the position of the optical element blank by dialing so that the center of the optical element blank is aligned with the center of the jig, the jig is fixed on the transition jig of the grinder workpiece axis, and the lower surface is ground and polished.

[0017] Furthermore, in the step 1), after the lower surface of the optical element blank is ground and polished to meet the requirements of the drawing, a protective paint is applied to the lower surface, the lower surface is fixed to the fixture with hot melt adhesive, and the position of the optical element blank is adjusted by dialing, the micrometer is aligned with the cylindrical positioning surface of the outer side of the optical element blank, and the position of the optical element blank is adjusted before the adhesive layer is cooled, so that the circular runout error of the optical element blank is less than 2μm, the center of the optical element blank is aligned with the center of the fixture, and the fixture is placed in a transition fixture on the workpiece axis of the grinder for fixation.

[0018] Preferably, the specific process of rough grinding + fine grinding in step 2) is: using a metal-based arc grinding wheel to perform rough grinding and aspheric molding processing on the upper surface of the optical element blank, the grinding wheel diameter is selected to be 120mm±10mm, the arc radius is less than 50mm, and the rough grinding process parameters are as follows: grinding wheel speed 6000±500rpm, component blank speed 60±10rpm, cutting depth 0.1±0.01mm, feed speed 0.05±0.005mm / rev; using a resin-based arc grinding wheel to fine grind the element, the grinding wheel diameter is selected to be 120±10mm, the arc radius is less than 50±5mm, and the fine grinding process parameters are as follows: grinding wheel speed 6000±500rpm, component blank speed 60±10rpm, cutting depth 0.02±0.001mm, feed speed 0.02±0.001mm / rev, to obtain a finely ground aspheric sample.

[0019] Furthermore, the specific process of step 3) is: using a spectral confocal displacement sensor to detect the component surface shape in situ, obtaining the component surface shape by measuring the aspheric contour generatrix, and determining the aspheric surface shape error by the deviation between the actual contour line and the aspheric equation.

[0020] Furthermore, the airbag polishing head in step 5) adopts 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 0.1±0.01mm, and polishing pad diameter 32±3mm.

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

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

[0023] Compared with the prior art, the advantages of the present invention are: by establishing a process flow of rough grinding-fine grinding-airbag rough polishing-airbag fine polishing, the process flow of aspheric optical components is optimized and improved, a spectral confocal displacement sensor is used to detect the surface shape of the component after grinding, and an airbag polishing method is used to improve the polishing efficiency; a special tooling fixture is designed to reduce the time for replacing the fixture, and reduce the clamping error and clamping time. The processing technology of the present invention is scientific and reasonable, which can not only realize the rapid measurement of the component surface shape during the grinding process, but also reduce the clamping error, greatly improve the processing quality and processing efficiency of aspheric optical components, and reduce the production cost. It is particularly suitable for the processing of axisymmetric aspheric optical components with a diameter of less than 120 mm and a surface shape accuracy requirement of less than 0.5 μm. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the structure of the bottom surface upward clamping and centering provided by an embodiment of the present invention;

[0025] Figure 2 is a cross-sectional view of the structure provided by an embodiment of the present invention after the lower surface is clamped upward;

[0026] Figure 3 is a cross-sectional view of the structure provided by an embodiment of the present invention after the upper surface is clamped upward;

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

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

[0029] Figure 6 It is a schematic diagram of the structure of the upper surface in-situ detection provided by an embodiment of the present invention;

[0030] Among them: 1. Fixture, 2. Optical element, 3. Transition fixture, 4. Micrometer, 5. Adhesive layer, 6. Spectral confocal displacement sensor. DETAILED DESCRIPTION

[0031] The present invention is further described in detail below with reference to the accompanying drawings.

[0032] like Figures 1 to 6 As shown, a method for high-efficiency composite processing of aspheric optical elements comprises the following steps:

[0033] 1. A jig is manufactured 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 jig 1 is divided into two parts, the lower part is a cylindrical structure 1-3 that fits in with the inner hole of the transition jig, 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 close to the inner ring is formed into an inner concave spherical surface 1-1 that fits in with the upper surface of the optical element 2 to be processed. The lower cylindrical structure 1-3 of the fixture 1 has a center hole coaxial with the upper part, and the transition fixture 3 is a hollow inverted T-shaped cylindrical structure. The diameter of the lower cylindrical structure 1-3 of the fixture 1 is consistent with the inner diameter of the transition fixture 3, which can ensure that the fixture 1 can be loaded into the transition fixture 3. The lower part of the fixture 1 is inserted into the transition fixture 3 and is positioned against the upper end surface of the transition fixture 3 through the step surface 1-4. The step surface 1-4 is provided with a positioning convex ring extending horizontally outward. The step surface 1-4 is perpendicular to the cylindrical structure 1-3, ensuring that the clamping center of the fixture 1 and the center of the transition fixture 3 are in a straight line.

[0034] 2. Grind and polish the lower surface 2-2 of the optical element 2 blank, and fix it on the jig 1 by gluing. The jig 1 is fixed on the transition fixture 3 of the grinding machine: first, fix the upper surface 2-1 of the optical element 2 blank on the jig 1 by gluing with hot melt adhesive as the adhesive layer 5, and adjust the position of the optical element blank 2 by using a dial so that the center of the optical element 2 blank is aligned with the center of the jig 1. The jig 1 is installed on the transition fixture 3 of the workpiece axis of the grinder and fixed, and the lower surface 2-2 is ground and polished. 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, and the lower surface 2-2 is fixed to the fixture 1 with a hot melt adhesive layer 5, and the position of the optical element 2 blank is adjusted by dialing, and the micrometer 4 is aligned with the outer cylindrical positioning surface 2-3 of the optical element 2 blank. The position of the optical element blank 2 is adjusted before the adhesive layer 5 is cooled, so that the circular runout error of the optical element 2 blank is less than 2μm, and the center of the optical element 2 blank is aligned with the center of the fixture 1, and the fixture 1 is placed in the transition fixture 3 on the workpiece axis of the grinder for fixation.

[0035] 3. The upper surface 2-1 of the optical element 2 blank is subjected to aspheric forming processing by rough grinding + fine grinding to obtain an aspheric sample: a metal-based arc grinding wheel is used to perform rough grinding aspheric forming processing on the upper surface of the blank. The diameter of the grinding wheel is 120mm, the arc radius is less than 50mm, and the rough grinding process parameters are as follows: the grinding wheel speed is 6000rpm, the component blank speed is 60rpm, the cutting depth is 0.1mm, and the feed speed is 0.05mm / rev.

[0036] A resin-based arc grinding wheel was used to fine-grind the component. The grinding wheel diameter was selected to be 120 mm, the arc radius was less than 50 mm, and the fine-grinding process parameters were as follows: grinding wheel speed 6000 rpm, component blank speed 60 rpm, cutting depth 0.02 mm, feed speed 0.02 mm / rev, and a fine-grinded aspheric sample was obtained.

[0037] 4. Use a profilometer to measure the surface data of aspheric samples: Use a spectral confocal displacement sensor 6 to detect the component surface shape in situ, obtain the component surface shape by measuring the aspheric contour generatrix, and determine the aspheric surface shape error by the deviation between the actual contour line and the aspheric equation.

[0038] 5. Import the surface shape data of the aspheric sample into the airbag polishing machine, calculate the NC code for the compensation processing, and fix the fixture and the aspheric sample together on the transition fixture of the polishing machine; import the component surface shape error data obtained by in-situ detection into the airbag polishing machine, calculate the NC code for the polishing compensation processing, remove the fixture and the sample from the grinder, and fix them in the liquid expansion fixture on the workpiece axis of the polishing machine.

[0039] 6. Use different airbag polishing heads to perform rough polishing and fine polishing on the upper surface of the aspheric sample: the airbag polishing head uses a semi-flexible airbag polishing head, and the rough polishing process parameters are: polishing head speed 900rpm, sample speed 800rpm, airbag pressure 1.2MPa, compression 0.1mm, and polishing pad diameter 32mm.

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

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

[0042] The invention adopts the process flow of rough grinding-fine grinding-airbag rough polishing-airbag fine polishing to optimize and improve the processing process of aspheric optical components, and designs special tooling fixtures to reduce the time for replacing fixtures, reduce clamping errors and clamping time; uses a spectral confocal displacement sensor to perform in-situ detection of the surface shape of the ground component, and uses an airbag polishing method to improve polishing efficiency.

[0043] The present invention can realize rapid measurement of the component surface shape during the grinding process, effectively improve the processing quality and processing efficiency of aspheric optical components, and reduce production costs. The present invention is particularly suitable for the processing of axisymmetric aspheric optical components with a diameter of less than 120 mm and a component surface shape accuracy requirement of less than 0.5 μm.

[0044] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for high-efficiency composite processing of aspheric optical elements, characterized in that The following steps are involved: 1) A jig is made according to the shape of the optical element to be processed, the lower surface of the optical element blank is ground and polished, and fixed to the jig by gluing, and the jig is fixed to the transition fixture of the grinding machine; 2) Performing aspheric forming processing on the upper surface of the optical element blank by rough grinding + fine grinding to obtain an aspheric sample; 3) Use a profilometer to measure the surface data of aspheric samples; 4) Importing the surface data of the aspheric sample into the airbag polishing machine, calculating the NC code for compensation processing, and fixing the fixture and the aspheric 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 aspheric sample; 6) After processing, use a profilometer to measure the surface data of the aspheric sample. If qualified, immerse the aspheric sample and the fixture in acetone solution and take out the sample.

2. The method according to claim 1, characterized in that: 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 fixture is divided into two parts, the lower part is a cylindrical structure that cooperates with 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 close to the inner ring is formed into a concave spherical surface that cooperates with the upper surface of the optical element to be processed.

3. The method according to claim 2, characterized in that: The lower cylindrical structure of the tooling fixture has a center 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 consistent with the inner diameter of the transition fixture. The lower part of the tooling fixture is inserted into the transition fixture and is positioned against the upper end surface of the transition fixture through a step surface, and the step surface is provided with a positioning convex ring extending horizontally outward.

4. The method according to claim 3, characterized in that: The specific process of step 1) grinding and polishing the lower surface of the optical element blank is: fixing the upper surface of the optical element blank on the jig by gluing with hot melt adhesive, and adjusting the position of the optical element blank by dialing so that the center of the optical element blank is aligned with the center of the jig, and the jig is fixed on the transition jig of the grinder workpiece axis, and the lower surface is ground and polished.

5. The method according to claim 4, characterized in that: In the step 1), after the lower surface of the optical element blank is ground and polished to meet the requirements of the drawing, a protective paint is applied to the lower surface, the lower surface is fixed on the fixture by hot melt adhesive, and the position of the optical element blank is adjusted by dialing, the micrometer is aligned with the cylindrical positioning surface of the outer side of the optical element blank, and the position of the optical element blank is adjusted before the adhesive layer is cooled, so that the circular runout error of the optical element blank is less than 2μm, the center of the optical element blank is aligned with the center of the fixture, and the fixture is placed in a transition fixture on the workpiece axis of the grinder for fixation.

6. The method according to claim 1, characterized in that: The specific process of the rough grinding + fine grinding of the step 2) is as follows: a metal-based arc grinding wheel is used to perform rough grinding and aspheric molding processing on the upper surface of the optical element blank, the grinding wheel diameter is selected to be 120mm±10mm, the arc radius is less than 50mm, and the rough grinding process parameters are as follows: grinding wheel speed 6000±500rpm, component blank speed 60±10rpm, cutting depth 0.1±0.01mm, feed speed 0.05±0.005mm / rev; a resin-based arc grinding wheel is used to fine grind the element, the grinding wheel diameter is selected to be 120±10mm, the arc radius is less than 50±5mm, and the fine grinding process parameters are as follows: grinding wheel speed 6000±500rpm, component blank speed 60±10rpm, cutting depth 0.02±0.001mm, feed speed 0.02±0.001mm / rev, to obtain a finely ground aspheric sample.

7. The method according to claim 1, characterized in that: The specific process of step 3) is: using a spectral confocal displacement sensor to detect the component surface shape in situ, obtaining the component surface shape by measuring the aspheric contour generatrix, and determining the aspheric surface shape error by the deviation between the actual contour line and the aspheric equation.

8. The method according to claim 1, characterized in that: The airbag polishing head in step 5) adopts 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 0.1±0.01mm, polishing pad diameter 32±3mm. The fine polishing process parameters are: polishing head speed 900±100rpm, sample speed 800±100rpm, airbag pressure 1.2±0.1MPa, compression 0.1±0.01mm, polishing pad diameter 16±1mm.

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

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