Processing method of monocrystalline silicon complex curved surface optical element

Abstract

The invention discloses a machining method for a monocrystalline silicon complex curved surface optical element. The machining method comprises the steps that S1, ultra-precision turning is conducted on the monocrystalline silicon complex curved surface optical element; s2, magneto-rheological polishing and shaping are carried out on the monocrystalline silicon complex curved surface optical element; s3, fairing the monocrystalline silicon complex curved surface optical element; and S4, the surface shape precision and the surface roughness of the monocrystalline silicon complex curved surface optical element are detected, if the detection result meets the requirement, machining is completed, and if the detection result does not meet the requirement, the step S2 is executed again. The method is simple in technological process and high in operability, after ultra-precision turning, the surface shape precision is good, subsurface damage is small, the grinding process can be omitted, the task load of the follow-up process is reduced, and the machining period of the monocrystalline silicon complex curved surface optical element is effectively shortened; by adopting a processing mode of combining ultra-precision turning and magneto-rheological polishing modification, processing and manufacturing of high-precision and high-surface-quality monocrystalline silicon complex curved surface elements can be realized.

Description

Technical Field

[0001] The present invention relates to the field of ultra-precision machining methods, and particularly to a machining method for single-crystal silicon complex-curved optical elements. Background Art

[0002] Single-crystal silicon has a high refractive index, low dispersion, and good transmittance in the infrared band. Single-crystal silicon lenses are widely used in infrared optical imaging systems. In order to more effectively achieve optical monitoring and tracking of targets, optical imaging systems are developing towards having a wide field of view and high resolution. This trend has put forward more stringent standards for the design of optical systems, the machining and detection technologies of optical elements. Given the limitations of traditional planar and spherical surfaces in terms of design freedom, they are difficult to meet the current design and application requirements. In this context, complex-curved surfaces provide more abundant design flexibility and space for optical systems. Currently, the main methods for machining single-crystal silicon are grinding, lapping, and polishing on a macroscopic scale. When removing large-sized materials, the efficiency is low, the cost is high, and it is impossible to complete the machining of complex-curved surfaces and microstructures, and it is difficult to meet the requirements of high-quality surfaces and subsurfaces in actual application scenarios. Therefore, for single-crystal silicon complex-curved optical elements, high-precision machining processes are still in an immature stage, and problems such as chipping are prone to occur during the machining process, and it is also very difficult to control the surface finish and surface form accuracy. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a machining method for single-crystal silicon complex-curved optical elements, the process flow of which is simple, the operability is strong, and the machining and manufacturing of single-crystal silicon complex-curved optical elements with high precision and high surface quality can be realized.

[0004] To solve the above technical problem, the present invention adopts the following technical solutions:

[0005] A machining method for single-crystal silicon complex-curved optical elements, comprising the following steps:

[0006] S1. Ultra-precision turning of the single-crystal silicon complex-curved optical element;

[0007] S2. Magnetorheological finishing and shaping of the single-crystal silicon complex-curved optical element;

[0008] S3. Smoothing of the single-crystal silicon complex-curved optical element;

[0009] S4. Detect the surface form accuracy and surface roughness of the single-crystal silicon complex-curved optical element. If the detection results meet the requirements, the machining is completed; if the detection results do not meet the requirements, return to step S2.

[0010] As a further improvement of the above technical solution: in step S1, the workpiece self-rotation turning method is adopted.

[0011] As a further improvement of the above technical solution: in step S1, diamond blade particles are used, and the blade particle parameters are a front angle of -25 to -35°, a back angle of 10 to 15°, and an arc radius of 0.5 to 1.0 mm.

[0012] As a further improvement of the above technical solution: the process parameters of step S1 are: workpiece rotation speed 1000-3000 rpm, turning feed speed 1-5 mm / s, and each turning amount 5-10 μm.

[0013] As a further improvement of the above technical solution: in order to reduce tool wear, increase tool life, and improve the surface quality and surface accuracy of the optical element after turning, laser-assisted turning is used in step S1.

[0014] As a further improvement of the above technical solution: in step S2, the surface shape of the single-crystal silicon complex curved optical element after ultra-precision turning is first measured, and guidance is provided for subsequent magnetorheological polishing and shaping based on the detected surface shape curve, and then magnetorheological polishing and shaping are performed.

[0015] As a further improvement of the above technical solution: the process parameters of step S2 are: the abrasive is CeO2 with a particle size of 0.1-0.3um, the polishing wheel speed is 100-300rpm, the current is 7-9A, the pressing depth is 0.1-0.4mm, and the flow rate of the magnetorheological polishing liquid is 100-200L / h.

[0016] As a further improvement of the above technical solution: in step S3, a small grinding head machine tool is used in combination with a polishing liquid to smooth the workpiece after magnetorheological polishing and shaping.

[0017] As a further improvement of the above technical solution: in step S3, the material of the polishing disc is damping cloth or asphalt, and the polishing disc can be set to different curvature radii according to the surface shape of the optical element to be processed, and the polishing liquid is diamond liquid or silicon oxide.

[0018] As a further improvement of the above technical solution: the process parameters of step S3 are: the pressure of the polishing disc is 0.02-0.05 MPa, the rotation speed of the polishing disc is 100-150 rpm, and the feed speed is 100-200 mm / s. After smoothing, the texture left by magnetorheological processing on the surface of the optical element is improved.

[0019] Compared with the prior art, the advantages of the present invention are:

[0020] The processing method of the single-crystalline silicon complex-curved surface optical element disclosed by the present invention has a simple process flow, strong operability. After ultra-precision turning, the surface shape accuracy is good, and the subsurface damage is less. The grinding process can be omitted, the task amount of the subsequent process is reduced, and the processing cycle of the single-crystalline silicon complex-curved surface optical element is effectively shortened; the processing method combining ultra-precision turning and magnetorheological polishing for shape correction can realize the processing and manufacturing of high-precision and high-surface-quality single-crystalline silicon complex-curved surface optical elements.

[0021] The present invention further introduces laser-assisted ultra-precision turning, which can increase the tool life, improve the surface shape accuracy and surface quality of the processing, and is suitable for the processing of large-size single-crystalline silicon complex-curved surface optical elements.

[0022] Other features and advantages of the present invention will be described in detail in the subsequent specific implementation section. Brief Description of the Drawings

[0023] Figure 1 is a schematic flow chart of the processing method of the single-crystalline silicon complex-curved surface optical element of the present invention.

[0024] Figure 2 is the surface shape accuracy detection result of the present invention.

[0025] Figure 3 is the surface roughness detection result of the present invention. Specific Implementation Modes

[0026] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is 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 should not be construed as a limitation of the present invention.

[0027] In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "a plurality of" means two or more unless otherwise specifically defined.

[0028] In the present invention, unless otherwise clearly specified and defined, the terms "assembly", "connection", "linkage", "fixation", etc. shall be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral body; it may be a mechanical connection or an electrical connection; it may be a direct connection or an indirect connection through an intermediate medium, and it may be the internal communication between two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0029] The present invention will be further described in detail below with reference to the accompanying drawings of the specification and specific embodiments.

[0030] As Figures 1 to 3 shown, taking a 103×106.5 mm single-crystal silicon off-axis parabolic optical element as an example, ultra-precision machining with high surface form accuracy and high surface quality is carried out on it.

[0031] Specifically referring to Figure 1 , the processing method of the single-crystal silicon complex-curved surface optical element in this embodiment includes the following steps:

[0032] S1 Ultra-precision turning of the single-crystal silicon complex-curved surface optical element;

[0033] S2 Magnetorheological processing of the single-crystal silicon complex-curved surface optical element;

[0034] S3 Smoothing of the single-crystal silicon complex-curved surface optical element;

[0035] S4 Inspection of the single-crystal silicon complex-curved surface optical element.

[0036] In step S1, ultra-precision turning is carried out on the silicon mirror element. A diamond cutting tool is used, and the parameters of the cutting tool are: the rake angle is -35°, the clearance angle is 10°, and the arc radius is 0.5 mm. The processing parameters used are: the workpiece rotation speed is 3000 rpm, the grinding wheel feed speed is 3 mm / min, the turning amount is 5 μm, and the laser power is 2.3 w. After ultra-precision turning, there are still cutting tool marks and rainbow patterns remaining on the surface of the optical element, and further polishing and shaping of the surface are required. For this purpose, the surface shape of the optical element after ultra-precision turning is measured first, and according to the detected surface shape curve, it provides guidance for the next polishing and shaping. The surface shape of the workpiece after ultra-precision turning is measured using a non-contact profiler to measure the workpiece.

[0037] Step S2 performs magnetorheological polishing on the workpiece surface after ultra-precision turning. The process parameters used are: CeO2 abrasive with a particle size of 0.2um, a polishing wheel speed of 280rpm, a current of 7A, a pressure depth of 0.2mm, a magnetorheological polishing fluid flow rate of 100-200L / h, a material peak removal rate of 0.8μm / min, and a material volume removal rate of 0.1mm 3 / min.

[0038] Step S3 uses a small grinding head machine tool (the grinding head size is generally 1 to 50 mm in outer diameter and 10 to 50 mm in length) and cooperates with polishing liquid to smooth the surface of the silicon mirror after magnetorheological polishing and shaping. The polishing liquid uses a diamond liquid with a particle size of 0.1 μm (Diamond Fluid, a grinding and polishing liquid material composed of diamond abrasives (such as single crystal or polycrystalline diamond powder) and a dispersion medium (such as water, oil or other solvents)). The polishing disc can use a damping cloth, the curvature radius of the polishing disc is 879.38 mm, the size of the polishing disc is 15 mm, and the parameters of the process used are: the pressure of the polishing disc is 0.04 Mpa, the rotation speed of the polishing disc is 130 rpm, and the feed speed is 200 mm / s. After smoothing, the lines left by magnetorheological processing on the surface of the optical element are improved.

[0039] Step S4 measures the surface shape accuracy and surface roughness of the component surface after magnetorheological polishing and smoothing. The surface shape measurement uses a 6-inch VeriFire Asphere laser wavefront interferometer from Zygo. During the detection process, a compensator and its posture adjustment platform are added to the interferometer. The surface roughness is measured using a white light interferometer from Zygo. 5 to 10 points are randomly selected on the surface of the component and measured using a 20X lens. The average value is finally taken as the test result of the surface roughness. When the measured surface shape accuracy and surface roughness meet the design requirements, the detection is completed, otherwise jump to step S2.

[0040] Although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention. Any technician familiar with the art can make many possible changes and modifications to the technical solution of the present invention by using the technical content disclosed above without departing from the scope of the technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention should fall within the scope of protection of the technical solution of the present invention.

Claims

1. A processing method for a single-crystal silicon complex curved surface optical element, characterized in that: It includes the following steps: S1. Ultra-precision turning of the single-crystal silicon complex-curved optical element; S2. Magnetorheological finishing and shaping of the single-crystal silicon complex-curved optical element; S3. Smoothing of the single-crystal silicon complex-curved optical element; S4. Detect the surface form accuracy and surface roughness of the single-crystal silicon complex-curved optical element. If the detection results meet the requirements, the processing is completed. If the detection results do not meet the requirements, return to step S2.

2. The processing method of the single-crystalline silicon complex curved surface optical element according to claim 1, wherein: In step S1, the workpiece self-rotation turning method is adopted.

3. The processing method of the single-crystalline silicon complex curved surface optical element according to claim 1, wherein: In step S1, diamond cutting grains are used, and the cutting grain parameters are rake angle -25° to -35°, clearance angle 10° to 15°, and arc radius 0.5 mm to 1.0 mm.

4. The processing method of the single-crystalline silicon complex curved surface optical element according to claim 3, wherein: The process parameters of step S1 are: workpiece rotation speed 1000 rpm to 3000 rpm, turning feed speed 1 mm / s to 5 mm / s, and each turning amount 5 μm to 10 μm.

5. The processing method of the single-crystal silicon complex curved surface optical element according to claim 1, wherein: In step S1, laser is used for assisted turning processing.

6. The processing method of the single-crystalline silicon complex-curved optical element according to any one of claims 1 to 5, characterized in that: In step S2, first measure the surface form of the single-crystal silicon complex-curved optical element after ultra-precision turning, and according to the detected surface form curve, provide guidance for subsequent magnetorheological finishing and shaping, and then perform magnetorheological finishing and shaping.

7. The processing method of the single-crystalline silicon complex curved surface optical element according to any one of claims 1 to 5, characterized in that: The process parameters of step S2 are: the abrasive is CeO2 with a particle size of 0.1 μm to 0.3 μm, the polishing wheel rotation speed is 100 rpm to 300 rpm, the current is 7 A to 9 A, the depth of indentation is 0.1 mm to 0.4 mm, and the flow rate of the magnetorheological polishing fluid is 100 L / h to 200 L / h.

8. The processing method of the monocrystalline silicon complex curved surface optical element according to any one of claims 1 to 5, characterized in that: In step S3, a small grinding head machine tool is used, and the workpiece after magnetorheological finishing and shaping is smoothed with the polishing fluid.

9. The processing method of the single-crystalline silicon complex-curved optical element according to claim 8, characterized in that: In step S3, the material of the polishing disc is damping cloth or asphalt, and the polishing fluid is diamond fluid or silicon oxide.

10. The processing method of the single-crystalline silicon complex-curved optical element according to claim 9, characterized in that: The process parameters of step S3 are: the pressure of the polishing disc is 0.02 Mpa to 0.05 Mpa, the rotation speed of the polishing disc is 100 rpm to 150 rpm, and the feed speed is 100 mm / s to 200 mm / s.

Images