A method for manufacturing fused silica double aspherical rod mirrors

Abstract

This invention discloses a method for manufacturing a fused silica double aspherical rod mirror, comprising the following steps: S1, laser-assisted ultra-precision turning of the fused silica double aspherical rod mirror; S2, detecting the surface accuracy and surface roughness of the fused silica double aspherical rod mirror; if the detection results meet the processing requirements, proceed to step S3, otherwise proceed to step S1; S3, conformal polishing of the fused silica double aspherical rod mirror; S4, detecting the surface accuracy and surface roughness of the fused silica double aspherical rod mirror; if the detection results meet the processing requirements, proceed to step S5, otherwise proceed to step S3; S5, optical inspection of the fused silica double aspherical rod mirror. This invention increases tool life while improving the surface accuracy after machining, reducing the surface roughness after machining, increasing turning efficiency, and introducing a conformal polishing process after ultra-precision turning to achieve a rapid improvement in the surface roughness of the machined rod mirror.

Description

Technical Field

[0001] This invention relates to the field of ultra-precision machining methods for optical components, and in particular to a method for manufacturing a fused silica double aspherical rod mirror. Background Technology

[0002] Currently, fused silica is a primary material for optical components in high-energy laser systems, characterized by high hardness, durability, and resistance to high-power laser damage. Typical fiber laser outputs produce a Gaussian intensity distribution with high peak power, making their internal optical components susceptible to damage from high-peak-power laser irradiation. Fused silica double aspherical rod mirrors can achieve beam shaping while offering advantages such as simple structure, strong resistance to laser damage, and ease of integration, making them promising candidates for application in fiber laser systems.

[0003] However, fused silica is a typical hard, brittle, and difficult-to-machine material. Traditional grinding and polishing methods for fused silica optical components are inefficient, cause significant subsurface damage, and are difficult to guarantee surface accuracy. Ultra-precision grinding technology is particularly challenging for machining small-diameter optical components, especially when machining small-diameter aspherical surfaces, where grinding head interference occurs, resulting in a large surface roughness. On the other hand, ultra-precision turning results in significant tool wear and tool scratches.

[0004] Therefore, achieving high-precision manufacturing of fused silica double aspherical rod mirrors is currently a challenging problem. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method for manufacturing fused silica double aspherical rod mirrors that is beneficial to increasing tool life, improving the profile accuracy after machining, and reducing the surface roughness after machining.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] A method for manufacturing a fused silica double aspherical rod mirror includes the following steps:

[0008] S1. Laser-assisted ultra-precision turning of fused silica double aspherical rod mirror;

[0009] S2. Inspect the surface accuracy and surface roughness of the fused silica double aspherical rod mirror. If the inspection results meet the processing requirements, proceed to step S3; otherwise, proceed to step S1.

[0010] S3. Perform conformal polishing on the fused silica double aspherical rod mirror;

[0011] S4. Inspect the surface accuracy and surface roughness of the fused silica double aspherical rod mirror. If the inspection results meet the processing requirements, proceed to step S5; otherwise, proceed to step S3.

[0012] S5. Perform optical inspection on the fused silica double aspherical bar mirror.

[0013] As a further improvement to the above technical solution:

[0014] Step S1 includes S1.1 rough turning:

[0015] When rough turning the convex aspherical surface at one end of the bar mirror, a tool with a rake angle of -20° to -40°, a clearance angle of 10° to 20°, and a radius of curvature of 0.3 to 0.8 mm is used. When rough turning the concave aspherical surface at one end of the bar mirror, a tool with a rake angle of -20° to -40°, a clearance angle of 10° to 20°, and a radius of curvature of 0.3 to 0.8 mm is used. The process parameters are: workpiece rotation speed 1000-3000 rpm, tool feed rate 2-4 mm / min, depth of cut 4-6 μm, laser wavelength 1064 nm, and laser power 10-15 W.

[0016] Step S1 also includes S1.2 semi-finish turning:

[0017] When semi-finish turning the convex aspherical surface, a tool with a rake angle of -20° to -40°, a clearance angle of 10° to 20°, and a radius of curvature of 0.3 to 0.8 mm is used; when semi-finish turning the concave aspherical surface, a tool with a rake angle of -20° to -40°, a clearance angle of 10° to 20°, and a radius of curvature of 0.3 to 0.8 mm is used. The process parameters are: workpiece rotation speed 1000 to 3000 rpm, tool feed rate 1 to 2 mm / min, depth of cut 2 to 4 μm, laser wavelength 1064 nm, and laser power 10 to 15 W.

[0018] Step S1 also includes S1.3 finish turning:

[0019] When finishing the convex aspherical surface, a tool with a rake angle of -20° to -40°, a clearance angle of 10° to 20°, and a radius of curvature of 0.3 to 0.8 mm is used; when finishing the concave aspherical surface, a tool with a rake angle of -20° to -40°, a clearance angle of 10° to 20°, and a radius of curvature of 0.3 to 0.8 mm is used. The process parameters are: workpiece rotation speed 1000-3000 rpm, tool feed rate 0.5 to 1 mm / min, depth of cut 1 to 2 μm, laser wavelength 1064 nm, and laser power 10 to 15 W.

[0020] If the detection result in step S2 does not meet the processing requirements, a compensation radius of curvature is introduced for semi-finish turning in step S1.2, and then finish turning is performed in step S1.3.

[0021] The cutting tool is a single-point diamond tool.

[0022] The process parameters for 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.

[0023] In step S2, the processing requirements are surface roughness Ra < 100 nm, surface accuracy PV < 1λ, and RMS < 100 nm.

[0024] In step S4, the processing requirements are surface roughness Ra < 20 nm, surface accuracy PV < 0.1λ, and RMS < 100 nm.

[0025] The optical performance of a workpiece is verified by measuring the far-field spot energy concentration, near-field spot uniformity, and power load capacity through beam shaping experiments.

[0026] Compared with the prior art, the advantages of the present invention are:

[0027] This invention discloses a method for manufacturing fused silica double aspherical rod mirrors. It employs laser-assisted ultra-precision turning combined with conformal polishing. By introducing laser-assisted cutting technology, it increases tool life while improving the surface profile accuracy after machining (surface profile error PV within 1μm, RMS within 100nm), reducing surface roughness (surface roughness Ra within 100nm), and increasing turning efficiency. Furthermore, the introduction of a conformal polishing process after ultra-precision turning achieves a rapid improvement in the surface roughness of the rod mirror (surface roughness Ra better than 20nm). In beam shaping experiments, the far-field beam energy concentration of the machined rod mirror reached 50.19%, the near-field beam uniformity was better than 85%, reaching a maximum of 88.11%, and the power load reached 14.7kW.

[0028] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0029] Figure 1 This is a schematic flowchart of the manufacturing method of the fused silica double aspherical rod mirror of the present invention.

[0030] Figure 2 The results of shape accuracy inspection after laser-assisted ultra-precision turning of the workpiece.

[0031] Figure 3 The surface roughness test results are for the workpiece after laser-assisted ultra-precision turning.

[0032] Figure 4 The result is the surface roughness test result after conformal polishing of the workpiece.

[0033] Figure 5 The image shows the far-field beam morphology of the workpiece in the far-field beam shaping experiment.

[0034] Figure 6 The near-field beam morphology of the workpiece in the near-field beam shaping experiment. Detailed Implementation

[0035] In the description of this invention, it should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0036] 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 technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0037] In this invention, unless otherwise explicitly specified and limited, the terms "assembly," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0038] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0039] See Figures 1 to 6 Taking a fused silica double aspherical beam shaping element as an example, the rod lens is composed of two aspherical surfaces, one end of which is a concave aspherical surface and the other end is a convex aspherical surface. The effective aperture of the concave surface is 6 mm and the effective aperture of the convex surface is 14 mm. The processing requirements are surface accuracy PV < 0.1λ, RMS < 100 nm, and surface roughness Ra < 20 nm.

[0040] The implementation steps of the fused silica double aspherical rod mirror manufacturing method in this embodiment include:

[0041] Step 1: Perform laser-assisted ultra-precision turning on the fused silica double aspherical rod mirror;

[0042] Step 2: Inspect the surface accuracy and surface roughness of the fused silica double aspherical rod mirror;

[0043] Step 3: Perform conformal polishing on the fused silica double aspherical rod mirror;

[0044] Step 4: Inspect the surface accuracy and surface roughness of the fused silica double aspherical rod mirror;

[0045] Step 5: Perform optical inspection on the fused silica double aspherical rod mirror.

[0046] In step 1, the fused silica double aspherical bar mirror is subjected to laser-assisted ultra-precision turning, including rough turning, semi-finish turning, and finish turning. When rough turning the convex aspherical surface of the bar mirror, a single-point diamond tool with a rake angle of -30°, a clearance angle of 13°, and a radius of curvature of 0.5mm is used; when machining the concave aspherical surface of the bar mirror, a single-point diamond tool with a rake angle of -30°, a clearance angle of 18°, and a radius of curvature of 0.5mm is used. The machining parameters are as follows: workpiece rotation speed 1000rpm, tool feed rate 2mm / min, depth of cut 6μm, laser wavelength 1064nm, and laser power 10W.

[0047] The process parameters used for laser-assisted semi-finish turning of fused silica double aspherical rod mirrors are as follows: workpiece rotation speed 1000 rpm, tool feed rate 1 mm / min, depth of cut 4 μm. Reducing the feed rate and depth of cut helps improve turning accuracy. The laser wavelength is 1064 nm and the laser power is 10 W. The tool parameters are the same as those for roughing.

[0048] The process parameters used for laser-assisted finish turning of the fused silica double aspherical bar mirror are as follows: workpiece rotation speed 1000 rpm, tool feed rate 0.5 mm / min, depth of cut 2 μm. Further reducing the feed rate and depth of cut helps to improve turning accuracy to meet the machining requirements. The laser wavelength is 1064 nm, and the laser power is 10 W. The tool parameters are consistent with those used for roughing and semi-finishing.

[0049] In step 2, the surface profile accuracy of the precision-machined fused silica double aspherical rod mirror is checked using a high-precision surface profilometer, and the surface roughness is checked using a white light interferometer. The test results are as follows: Figure 2 , Figure 3As shown, the detected values ​​are: convex surface Ra = 37.89 nm, PV = 0.73 μm, RMS = 88.01 nm; concave surface Ra = 52.4 nm, PV = 0.85 μm, RMS = 46.27 nm. The surface roughness Ra < 100 nm, surface profile accuracy PV < 1λ (λ is the laser wavelength used in the interferometer), RMS < 100 nm. Proceed to step 3; otherwise, return to step 1 and perform semi-finish turning with a compensated radius of curvature based on the actual measured results. The machining parameters are: workpiece rotation speed 1000 rpm, tool feed rate 1 mm / min, depth of cut 2 μm, laser wavelength 1064 nm, laser power 10 W. Then, finish turning is performed with the following parameters: workpiece rotation speed 1000 rpm, tool feed rate 1 mm / min, depth of cut 2 μm, laser wavelength 1064 nm, laser power 10 W.

[0050] In step 3, after ultra-precision turning, the component still falls short of technical requirements and requires further conformal polishing. The machined fused silica double aspherical rod mirror undergoes conformal polishing using a turning and polishing integrated machine to improve surface roughness. The conformal polishing process parameters are: workpiece rotation speed 10 rpm, polyurethane polishing speed 8000 rpm, pressure 5 N, and feed rate 2 mm / min.

[0051] In step 4, the surface accuracy and surface roughness of the processed fused silica double aspherical rod mirror are checked again. The roughness is measured using a white light interferometer, and the results are as follows: Figure 4 As shown, the measured Ra of the convex surface is 5.86 nm, PV is 0.08 μm, and RMS is 7.38 nm, while the measured Ra of the concave surface is 6.21 nm, PV is 0.09 μm, and RMS is 15.02 nm. The processing parameters meet the requirements of Ra < 20 nm, PV < 0.1λ, and RMS < 100 nm. Otherwise, return to step 3 and perform the polishing process again based on the measured results.

[0052] In step 5, the polished double aspherical rod mirror undergoes optical testing. Its optical performance is verified by measuring the far-field spot energy concentration, near-field spot uniformity, and power loading capacity through beam shaping experiments. The far-field spot morphology is as follows: Figure 5 As shown, the far-field spot energy concentration is 50.19%, indicating a good reshaping effect. The reshaped spot is relatively uniform. In the far-field spot reshaping experiment, the fiber laser power was 50W and the wavelength was 1070nm. The near-field spot morphology is shown below. Figure 6As shown, the measured near-field beam uniformity is higher than 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 with a wavelength of 1070nm and a power of 2.9kW was applied to detect the power load of the processed rod mirror. It can be seen that the rod mirror can work normally at a power of 2.9kW. Through calculation, its power load can be obtained as 14.7kW.

[0053] The present invention discloses a method for manufacturing fused silica double aspherical rod mirrors, which employs laser-assisted ultra-precision turning combined with conformal polishing. By introducing laser-assisted technology combined with single-point diamond cutting technology, the method increases tool life while improving the surface profile accuracy after machining (surface profile error PV within 1μm, RMS within 100nm), reducing the surface roughness after machining (surface roughness Ra within 100nm), increasing turning efficiency, and introducing a conformal polishing method after ultra-precision turning to achieve a rapid improvement in the surface roughness of the rod mirror (surface roughness Ra better than 20nm).

[0054] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments, without departing from the scope of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the scope of the present invention, should fall within the protection scope of the present invention.

Claims

1. A method for manufacturing a fused silica double aspherical rod mirror, characterized in that: Includes the following steps: S1. Laser-assisted ultra-precision turning of fused silica double aspherical rod mirror; S2. Inspect the surface accuracy and surface roughness of the fused silica double aspherical rod mirror. If the inspection results meet the processing requirements, proceed to step S3; otherwise, proceed to step S1. S3. Perform conformal polishing on the fused silica double aspherical rod mirror; S4. Inspect the surface accuracy and surface roughness of the fused silica double aspherical rod mirror. If the inspection results meet the processing requirements, proceed to step S5; otherwise, proceed to step S3. S5. Perform optical inspection on the fused silica double aspherical rod mirror; Step S1 includes S1.1 rough turning: When rough turning the convex aspherical surface at one end of the bar mirror, a tool with a rake angle of -20° to -40°, a clearance angle of 10° to 20°, and a radius of curvature of 0.3 to 0.8 mm is used; when rough turning the concave aspherical surface at one end of the bar mirror, a tool with a rake angle of -20° to -40°, a clearance angle of 10° to 20°, and a radius of curvature of 0.3 to 0.8 mm is used. The process parameters are: workpiece rotation speed 1000-3000 rpm, tool feed rate 2-4 mm / min, depth of cut 4-6 μm, laser wavelength 1064 nm, and laser power 10-15 W. Step S1 also includes S1.2 semi-finish turning: When semi-finishing the convex aspherical surface, a tool with a rake angle of -20° to -40°, a clearance angle of 10° to 20°, and a radius of curvature of 0.3 to 0.8 mm is used; when semi-finishing the concave aspherical surface, a tool with a rake angle of -20° to -40°, a clearance angle of 10° to 20°, and a radius of curvature of 0.3 to 0.8 mm is used. The process parameters are: workpiece rotation speed 1000 to 3000 rpm, tool feed rate 1 to 2 mm / min, depth of cut 2 to 4 μm, laser wavelength 1064 nm, and laser power 10 to 15 W. Step S1 also includes S1.3 finish turning: When finishing the convex aspherical surface, a tool with a rake angle of -20° to -40°, a clearance angle of 10° to 20°, and a radius of curvature of 0.3 to 0.8 mm is used; when finishing the concave aspherical surface, a tool with a rake angle of -20° to -40°, a clearance angle of 10° to 20°, and a radius of curvature of 0.3 to 0.8 mm is used. The process parameters are: workpiece rotation speed 1000-3000 rpm, tool feed rate 0.5 to 1 mm / min, depth of cut 1 to 2 μm, laser wavelength 1064 nm, and laser power 10 to 15 W.

2. The method for manufacturing a fused silica double aspherical rod mirror according to claim 1, characterized in that: If the detection result in step S2 does not meet the processing requirements, a compensation radius of curvature is introduced for semi-finish turning in step S1.2, and then finish turning is performed in step S1.

3.

3. The method for manufacturing a fused silica double aspherical rod mirror according to any one of claims 1 to 2, characterized in that: The cutting tool is a single-point diamond tool.

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

5. The method for manufacturing a fused silica double aspherical rod mirror according to any one of claims 1 to 2, characterized in that: In step S2, the processing requirements are surface roughness Ra < 100 nm, surface accuracy PV < 1λ, and RMS < 100 nm.

6. The method for manufacturing a fused silica double aspherical rod mirror according to any one of claims 1 to 2, characterized in that: In step S4, the processing requirements are surface roughness Ra < 20 nm, surface accuracy PV < 0.1λ, and RMS < 100 nm.

7. The method for manufacturing a fused silica double aspherical rod mirror according to any one of claims 1 to 2, characterized in that: The optical performance of a workpiece is verified by measuring the far-field spot energy concentration, near-field spot uniformity, and power load capacity through beam shaping experiments.

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