Manufacturing method of fused quartz double-aspheric-surface rod lens

Abstract

The invention discloses a manufacturing method of a fused quartz double-aspheric-surface rod mirror. The manufacturing method comprises the following steps: S1, carrying out laser-assisted ultra-precision turning on the fused quartz double-aspheric-surface rod mirror; s2, detecting the surface type precision and the surface roughness of the fused quartz double-aspheric rod mirror, if the detection result meets the processing requirement, executing the step S3, otherwise, executing the step S1; s3, performing shape-preserving polishing on the fused quartz double-aspheric rod mirror; s4, detecting the surface precision and the surface roughness of the fused quartz double-aspheric rod mirror, if the detection result meets the processing requirement, executing the step S5, and otherwise, executing the step S3; and S5, performing optical inspection on the fused quartz double aspheric rod lens. According to the method, the service life of the tool is prolonged, meanwhile, the profile precision after machining is improved, the surface roughness after machining is reduced, the turning efficiency is improved, the conformal polishing procedure is introduced after ultra-precision turning, and the roughness of the machined rod mirror is rapidly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of ultra-precision processing methods for optical elements, and in particular to a method for manufacturing a fused silica double aspheric rod mirror. Background Art

[0002] Currently, fused silica is the primary material for optical components in high-energy laser systems. It features high hardness, durability, and strong resistance to high-power laser damage. Conventional fiber laser outputters produce a high-peak-power Gaussian distribution of light intensity, making internal optical components susceptible to damage from high-peak-power laser irradiation. Fused silica double aspheric rod mirrors can achieve beam shaping while offering advantages such as simple structure, strong resistance to laser damage, and ease of integration. They hold broad application prospects in fiber laser systems.

[0003] However, fused quartz is a typically hard, brittle, and difficult-to-machine material. Traditional grinding and polishing methods for fused quartz optical components suffer from low processing efficiency, significant subsurface damage, and difficulty maintaining surface accuracy. Ultra-precision grinding is particularly challenging for machining small-aperture optical components, particularly small-aperture aspheric surfaces, where grinding head interference can occur and surface roughness can be high. Ultra-precision turning, on the other hand, can lead to significant tool wear and scratches.

[0004] Therefore, how to achieve high-precision manufacturing of fused silica double aspheric rod mirrors is currently a difficult problem. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a method for manufacturing a fused quartz double aspheric rod mirror, which is beneficial to increasing tool life, improving post-processing profile accuracy, and reducing post-processing surface roughness.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions: A method for manufacturing a fused silica double aspheric rod mirror comprises the following steps: S1, laser-assisted ultra-precision turning of fused silica double aspheric rod mirror; S2, testing the surface accuracy and surface roughness of the fused silica double aspheric rod mirror. If the test results meet the processing requirements, execute step S3; otherwise, execute step S1; S3, performing conformal polishing on the fused silica double aspheric rod mirror; S4, testing the surface accuracy and surface roughness of the fused silica double aspheric rod mirror. If the test results meet the processing requirements, execute step S5; otherwise, execute step S3; S5. Perform optical inspection on the fused silica double aspheric rod mirror.

[0007] As a further improvement of the above technical solution: Step S1 includes S1.1 rough turning: When rough turning the convex aspheric surface at one end of the rod mirror, a tool with a rake angle of -20° to -40°, a back angle of 10° to 20°, and a curvature radius of 0.3 to 0.8 mm is used; when rough turning the concave aspheric surface at one end of the rod mirror, a tool with a rake angle of -20° to -40°, a back angle of 10° to 20°, and a curvature radius of 0.3 to 0.8 mm is used. The process parameters are: workpiece speed 1000-3000rpm, tool feed speed 2-4mm / min, cutting depth 4-6μm, laser wavelength 1064nm, laser power 10-15W.

[0008] Step S1 also includes S1.2 semi-finishing turning: When semi-finishing the convex aspheric surface, a tool with a rake angle of -20° to -40°, a clearance angle of 10° to 20°, and a curvature radius of 0.3 to 0.8 mm is used; when semi-finishing the concave aspheric surface, a tool with a rake angle of -20° to -40°, a clearance angle of 10° to 20°, and a curvature radius of 0.3 to 0.8 mm is used. The process parameters are: workpiece speed 1000 to 3000 rpm, tool feed speed 1 to 2 mm / min, cutting depth 2 to 4 μm, laser wavelength 1064 nm, and laser power 10 to 15 W.

[0009] Step S1 also includes S1.3 finishing machining: When finishing the convex aspheric surface, a tool with a rake angle of -20° to -40°, a clearance angle of 10° to 20°, and a curvature radius of 0.3 to 0.8 mm is used; when finishing the concave aspheric surface, a tool with a rake angle of -20° to -40°, a clearance angle of 10° to 20°, and a curvature radius of 0.3 to 0.8 mm is used. The process parameters are: workpiece speed 1000-3000 rpm, tool feed speed 0.5-1 mm / min, cutting depth 1-2 μm, laser wavelength 1064 nm, and laser power 10-15 W.

[0010] If the detection result in step S2 does not meet the processing requirements, a compensating curvature radius is introduced to perform semi-finishing turning in step S1.2, and then finishing turning in step S1.3.

[0011] The tool is a single-point diamond tool.

[0012] The process parameters of step S3 are: workpiece rotation speed 10-15 rpm, polyurethane polishing rotation speed 8000-10000 rpm, pressure 5-10 N, and feed speed 2-4 mm / min.

[0013] The processing requirements in step S2 are surface roughness Ra<100nm, surface accuracy PV<1λ, and RMS<100nm.

[0014] The processing requirements in step S4 are surface roughness Ra<20nm, surface accuracy PV<0.1λ, and RMS<100nm.

[0015] The far-field spot energy concentration, near-field spot uniformity and power load capacity of the workpiece are measured through beam shaping experiments to test its optical performance.

[0016] Compared with the prior art, the advantages of the present invention are: The disclosed method for manufacturing a fused silica double-aspheric rod mirror utilizes laser-assisted ultra-precision turning combined with conformal polishing. This laser-assisted cutting technology increases tool life while improving post-processing profile accuracy (surface profile error PV within 1μm, RMS within 100nm), reducing post-processing surface roughness (surface roughness Ra within 100nm), and increasing turning efficiency. Furthermore, a conformal polishing step is introduced after ultra-precision turning to rapidly improve the roughness of the rod mirror (surface roughness Ra better than 20nm). In beam shaping experiments, the processed rod mirror achieved a far-field spot energy concentration of 50.19%, a near-field spot uniformity better than 85%, and a peak of 88.11%, with a power load of 14.7kW.

[0017] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of the process of manufacturing the fused silica double aspheric rod mirror of the present invention.

[0019] Figure 2 This is the result of profile accuracy inspection after the workpiece is processed by laser-assisted ultra-precision turning.

[0020] Figure 3 This is the surface roughness test result of the workpiece after laser-assisted ultra-precision turning.

[0021] Figure 4 This is the surface roughness test result of the workpiece after conformal polishing.

[0022] Figure 5 This is the far-field spot morphology of the workpiece in the far-field beam shaping experiment.

[0023] Figure 6 This is the near-field spot morphology of the workpiece in the near-field beam shaping experiment. DETAILED DESCRIPTION

[0024] In the description of the present invention, it should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention.

[0025] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature identified as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0026] In the present invention, unless otherwise expressly specified or limited, terms such as "assemble," "connect," "connect," and "fix" should be understood in a broad sense. For example, they may refer to fixed connection, detachable connection, or integration; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; and internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0027] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] See also Figures 1 to 6 Taking a fused silica double aspheric beam shaping element as an example, the rod mirror consists of two aspheric surfaces, one end is a concave aspheric surface, and the other end is a convex aspheric surface. The effective aperture of the concave surface is 6mm, and the effective aperture of the convex surface is 14mm. The processing requirements are surface accuracy PV<0.1λ, RMS<100nm, and surface roughness Ra<20nm.

[0029] The manufacturing method of the fused silica double aspheric rod mirror of this embodiment includes the following steps: Step 1: Laser-assisted ultra-precision turning of a fused silica double aspheric rod mirror; Step 2: Detecting the surface accuracy and surface roughness of the fused silica double aspheric rod mirror; Step 3, performing conformal polishing on the fused silica double aspheric rod mirror; Step 4: Detect the surface accuracy and surface roughness of the fused silica double aspheric rod mirror; Step 5: Perform optical inspection on the fused silica double aspheric rod mirror.

[0030] In step 1, the fused silica double aspheric rod mirror is subjected to laser-assisted ultra-precision turning, including rough turning, semi-finishing turning and finishing turning. When rough turning the convex aspheric surface of the rod mirror, a single-point diamond tool with a rake angle of -30°, a back angle of 13°, and a curvature radius of 0.5 mm is used; when processing the concave aspheric surface of the rod mirror, a single-point diamond tool with a rake angle of -30°, a back angle of 18°, and a curvature radius of 0.5 mm is used. The process parameters used in the processing are: workpiece speed 1000 rpm, tool feed speed 2 mm / min, cutting depth 6 μm, laser wavelength 1064 nm, and laser power 10 W.

[0031] The process parameters for laser-assisted semi-finishing turning of a fused silica double aspheric rod mirror are: workpiece speed of 1000 rpm, tool feed rate of 1 mm / min, and depth of cut of 4 μm. Reducing the feed rate and depth of cut improves turning accuracy. The laser wavelength is 1064 nm, and the laser power is 10 W. The tool parameters remain the same as for rough turning.

[0032] The process parameters for laser-assisted finish turning of a fused silica double aspheric rod mirror are: workpiece speed of 1000 rpm, tool feed rate of 0.5 mm / min, and depth of cut of 2 μm. Further reducing the feed rate and depth of cut can further improve turning accuracy to meet the required machining requirements. The laser wavelength is 1064 nm, and the laser power is 10 W. The tool parameters remain the same as those for rough turning and semi-finishing turning.

[0033] In step 2, the surface accuracy of the fused quartz double aspheric rod mirror after fine turning is tested by a high-precision surface profiler, and the surface roughness is tested by a white light interferometer. The test results are as follows: Figure 2 、 Figure 3 As shown, the convex surface Ra value is 37.89nm, the PV value is 0.73μm, and the RMS value is 88.01nm. The concave surface Ra value is 52.4nm, the PV value is 0.85μm, and the RMS value is 46.27nm. The measured surface roughness Ra is less than 100nm, the surface accuracy PV is less than 1λ (λ is the laser wavelength used by the interferometer), and the RMS is less than 100nm. Proceed to step 3. Otherwise, return to step 1 and introduce the compensated curvature radius based on the actual measured results for semi-finishing turning. The processing parameters are: workpiece speed 1000rpm, tool feed rate 1mm / min, depth of cut 2μm, laser wavelength 1064nm, and laser power 10W. Then, finish turning is performed with the following processing parameters: workpiece speed 1000rpm, tool feed rate 1mm / min, depth of cut 2μm, laser wavelength 1064nm, and laser power 10W.

[0034] In step 3, after ultra-precision turning, the component still falls far short of the technical requirements, requiring further conformal polishing of the surface. The machined fused silica double aspheric rod mirror undergoes conformal polishing using a turning-polishing machine to improve the roughness. The conformal polishing process parameters are: workpiece speed 10 rpm, polyurethane polishing speed 8000 rpm, pressure 5 N, and feed rate 2 mm / min.

[0035] In step 4, the surface accuracy and surface roughness of the processed fused silica double aspheric rod mirror are tested again. The roughness is measured using a white light interferometer. Figure 4 As shown, the convex surface Ra is measured to be 5.86nm, PV is 0.08μm, RMS is 7.38nm, the concave surface Ra is 6.21nm, PV is 0.09μm, RMS is 15.02nm, which meets the processing index requirements of Ra<20nm, PV<0.1λ, RMS<100nm, otherwise return to step 3 and perform the polishing process again according to the measured results.

[0036] In step 5, the polished double aspheric rod mirror is optically inspected, and its far-field spot energy concentration, near-field spot uniformity and power load capacity are measured through beam shaping experiments to verify its optical performance. Figure 5 As shown in the figure, the far-field spot energy concentration is 50.19%, the shaping effect is good, and the spot is more uniform after shaping. In the far-field spot shaping experiment, the fiber laser power is 50W and the wavelength is 1070nm. The near-field spot morphology is as follows Figure 6 As shown in the figure, the measured near-field spot uniformity exceeded 85%, reaching a maximum of 88.11%. In the near-field beam shaping experiment, the fiber laser power was 50W and the wavelength was 1070nm. A high-power laser of 2.9kW at the same wavelength was applied to test the power load of the processed rod mirror. It was found that the rod mirror could operate normally at 2.9kW power, and its power load was calculated to be 14.7kW.

[0037] The present invention provides a method for manufacturing a fused silica double aspheric rod mirror, which adopts laser-assisted ultra-precision turning combined with conformal polishing. By introducing laser-assisted technology combined with single-point diamond cutting technology, the tool life is increased while the post-processing profile accuracy is improved (the surface profile error PV is within 1 μm, and the RMS is within 100 nm), the post-processing surface roughness is reduced (the surface roughness Ra is within 100 nm), the turning efficiency is increased, and a conformal polishing method is introduced after ultra-precision turning to achieve a rapid improvement in the roughness of the processed rod mirror (the surface roughness Ra is better than 20 nm).

[0038] Although the present invention has been disclosed above with reference to preferred embodiments, this is not intended to limit the present invention. Any person skilled in the art can, without departing from the scope of the technical solution of the present invention, utilize the technical content disclosed above to make many possible changes and modifications to the technical solution of the present invention, or modify it into an equivalent embodiment with equivalent changes. Therefore, any simple modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for manufacturing a fused silica double aspheric rod mirror, characterized in that: The following steps are involved: S1, laser-assisted ultra-precision turning of fused silica double aspheric rod mirror; S2, testing the surface accuracy and surface roughness of the fused silica double aspheric rod mirror. If the test results meet the processing requirements, execute step S3; otherwise, execute step S1; S3, performing conformal polishing on the fused silica double aspheric rod mirror; S4, testing the surface accuracy and surface roughness of the fused silica double aspheric rod mirror. If the test results meet the processing requirements, execute step S5; otherwise, execute step S3; S5. Perform optical inspection on the fused silica double aspheric rod mirror.

2. The method for manufacturing a fused silica double aspheric rod mirror according to claim 1, wherein: Step S1 includes S1.1 rough turning: When rough turning the convex aspheric surface at one end of the rod mirror, a tool with a rake angle of -20° to -40°, a back angle of 10° to 20°, and a curvature radius of 0.3 to 0.8 mm is used; when rough turning the concave aspheric surface at one end of the rod mirror, a tool with a rake angle of -20° to -40°, a back angle of 10° to 20°, and a curvature radius of 0.3 to 0.8 mm is used. The process parameters are: workpiece speed 1000-3000 rpm, tool feed speed 2-4 mm / min, cutting depth 4-6 μm, laser wavelength 1064 nm, and laser power 10-15 W.

3. The method for manufacturing a fused silica double aspheric rod mirror according to claim 2, wherein: Step S1 also includes S1.2 semi-finishing turning: When semi-finishing the convex aspheric surface, a tool with a rake angle of -20° to -40°, a clearance angle of 10° to 20°, and a curvature radius of 0.3 to 0.8 mm is used; when semi-finishing the concave aspheric surface, a tool with a rake angle of -20° to -40°, a clearance angle of 10° to 20°, and a curvature radius of 0.3 to 0.8 mm is used. The process parameters are: workpiece speed 1000 to 3000 rpm, tool feed speed 1 to 2 mm / min, cutting depth 2 to 4 μm, laser wavelength 1064 nm, and laser power 10 to 15 W.

4. The method for manufacturing a fused silica double aspheric rod mirror according to claim 3, wherein: Step S1 also includes S1.3 finishing machining: When finishing the convex aspheric surface, a tool with a rake angle of -20° to -40°, a clearance angle of 10° to 20°, and a curvature radius of 0.3 to 0.8 mm is used; when finishing the concave aspheric surface, a tool with a rake angle of -20° to -40°, a clearance angle of 10° to 20°, and a curvature radius of 0.3 to 0.8 mm is used. The process parameters are: workpiece speed 1000-3000 rpm, tool feed speed 0.5-1 mm / min, cutting depth 1-2 μm, laser wavelength 1064 nm, and laser power 10-15 W.

5. The method for manufacturing a fused silica double aspheric rod mirror according to claim 4, wherein: If the detection result in step S2 does not meet the processing requirements, a compensating curvature radius is introduced to perform semi-finishing turning in step S1.2, and then finishing turning in step S1.

3.

6. The method for manufacturing a fused silica double aspheric rod mirror according to any one of claims 2 to 5, characterized in that: The tool is a single-point diamond tool.

7. The method for manufacturing a fused silica double aspheric rod mirror according to any one of claims 1 to 5, characterized in that: The process parameters of step S3 are: workpiece rotation speed 10-15 rpm, polyurethane polishing rotation speed 8000-10000 rpm, pressure 5-10 N, and feed speed 2-4 mm / min.

8. The method for manufacturing a fused silica double aspheric rod mirror according to any one of claims 1 to 5, characterized in that: The processing requirements in step S2 are surface roughness Ra<100nm, surface accuracy PV<1λ, and RMS<100nm.

9. The method for manufacturing a fused silica double aspheric rod mirror according to any one of claims 1 to 5, characterized in that: The processing requirements in step S4 are surface roughness Ra<20nm, surface accuracy PV<0.1λ, and RMS<100nm.

10. The method for manufacturing a fused silica double aspheric rod mirror according to any one of claims 1 to 5, characterized in that: The far-field spot energy concentration, near-field spot uniformity and power load capacity of the workpiece are measured through beam shaping experiments to test its optical performance.

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