CN111390652A - Preparation method of off-axis aspheric silicon carbide reflector - Google Patents
Preparation method of off-axis aspheric silicon carbide reflector Download PDFInfo
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- CN111390652A CN111390652A CN202010205914.7A CN202010205914A CN111390652A CN 111390652 A CN111390652 A CN 111390652A CN 202010205914 A CN202010205914 A CN 202010205914A CN 111390652 A CN111390652 A CN 111390652A
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- silicon carbide
- axis aspheric
- reflector
- aspheric surface
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B24—GRINDING; POLISHING
- B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
- B24B1/00—Processes of grinding or polishing; Use of auxiliary equipment in connection with such processes
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/08—Mirrors
- G02B5/10—Mirrors with curved faces
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- Mechanical Engineering (AREA)
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- Optics & Photonics (AREA)
- Optical Elements Other Than Lenses (AREA)
Abstract
A preparation method of an off-axis aspheric silicon carbide reflector relates to the technical field of reflector processing, solves the problem of low manufacturing efficiency in the prior art, and comprises the following steps: s1, taking a silicon carbide flat plate, and processing one surface of the silicon carbide flat plate into an initial off-axis aspheric surface through milling; and S2, polishing the initial off-axis aspheric surface by adopting a prestress processing technology to obtain a final off-axis aspheric surface, and manufacturing the off-axis aspheric silicon carbide reflector. The invention pre-processes the upper surface of the silicon carbide flat plate into a rough initial off-axis aspheric surface with a target aspheric surface shape without changing the original prestress polishing technology, and then polishes the rough initial off-axis aspheric surface by adopting the prestress polishing technology. The off-axis aspheric silicon carbide reflector is applied to large-scale foundation astronomical telescopes and space telescopes.
Description
Technical Field
The invention relates to the technical field of reflector processing, in particular to a preparation method of an off-axis aspheric silicon carbide reflector.
Background
The main mirror of the large-aperture optical astronomical telescope is formed by splicing dozens of off-axis aspheric surface thin plate reflectors or even nearly thousands of off-axis aspheric surface thin plate reflectors, and because the number of the required off-axis aspheric surface thin plate reflectors is huge, the contradiction between the large number of the required off-axis aspheric surface thin plate reflectors and the long processing period cannot be solved by the traditional optical processing technology, and the technology of quick polishing is urgently needed to be invented.
In the last 80 th century, the technology of pre-stress polishing was developed to polish off-axis aspheric surfaces in accordance with the above requirement. The first step of the prestress polishing technology is that according to the calculation result of the elastic thin plate small-deflection deformation theory, a plurality of external forces are applied to a parallel thin plate mirror blank, and stress distribution required by enabling a mirror surface to be deformed into an off-axis aspheric surface is generated in the mirror blank, so that the mirror blank generates deformation response; secondly, under the condition that the deformation state of the mirror blank is kept, a spherical grinding disc with the diameter larger than that of the mirror blank is used for carrying out full-aperture removal and polishing on the mirror blank, and a spherical surface with the same curvature radius as that of the grinding disc is formed; and thirdly, after the external force is removed, when the mirror blank recovers the natural state, obtaining the required off-axis aspheric surface. Here, the thin plate is a plate having a thickness dimension much smaller than a dimension in the plate surface extending direction (about several tens or more). The prestress polishing technology has the advantages that a polished object can be converted from an aspheric surface into a spherical surface, and the caliber of the grinding disc is larger than that of the off-axis aspheric surface thin plate reflector to be polished, so that the processing efficiency of the reflector is greatly improved. At present, the method is adopted for polishing a low-expansion glass off-axis aspheric surface thin plate reflector of a primary mirror of a large astronomical telescope system.
Silicon carbide is a high-quality space reflector material with the properties of stable chemical properties, high thermal conductivity, small thermal expansion coefficient, large specific stiffness and the like, and is widely applied to a single-body mirror space remote sensing and observation system. However, since silicon carbide is a brittle material with ceramic properties, it is currently processed mainly by small-area contact tool processing techniques (collectively referred to as sub-aperture processing techniques) such as mechanical milling, small grinding head, magnetorheological, and the like. The sub-aperture processing method has the defects that medium-high frequency errors are easily caused, namely, the surface roughness is large, the requirement of smooth finish can be met only by subsequent polishing, and the processing and polishing of the off-axis aspheric silicon carbide thin plate reflector in the prior art is long in time consumption and only suitable for single-piece or small-batch production.
At present, the application of prestress polishing in the processing of off-axis aspheric silicon carbide thin plate reflectors at home and abroad is still blank. In addition, because the silicon carbide material has high hardness, low removal rate and slow surface convergence, even if the off-axis aspheric silicon carbide thin plate reflector is polished by adopting a prestress polishing technology after sub-aperture processing, the used time is more than 5 times of that of polishing a glass reflector, the efficiency is extremely low, and the high efficiency advantage of prestress polishing cannot be exerted. Therefore, in order to mass-produce and apply the off-axis aspheric silicon carbide thin plate reflectors to large-scale ground astronomical telescopes and space telescopes, a manufacturing method capable of improving the manufacturing efficiency of the off-axis aspheric silicon carbide reflectors and shortening the manufacturing time is needed.
Disclosure of Invention
The invention provides a preparation method of an off-axis aspheric silicon carbide reflector, aiming at solving the problem of low manufacturing efficiency of the existing off-axis aspheric silicon carbide reflector.
The technical scheme adopted by the invention for solving the technical problem is as follows:
a method for preparing an off-axis aspheric silicon carbide reflector comprises the following steps:
s1, taking a silicon carbide flat plate, and processing one surface of the silicon carbide flat plate into an initial off-axis aspheric surface through milling;
and S2, polishing the initial off-axis aspheric surface by adopting a prestress processing technology to obtain a final off-axis aspheric surface, and finishing the manufacture of the off-axis aspheric silicon carbide reflector.
The off-axis aspheric silicon carbide reflector is prepared by the preparation method of the off-axis aspheric silicon carbide reflector.
The invention has the beneficial effects that:
the surface of the silicon carbide flat plate is pre-processed by adopting a mature mechanical milling and grinding processing technology without changing the original prestress polishing technology, so that the upper surface of the silicon carbide flat plate is a rough surface in a desired target off-axis aspheric surface shape to form an initial off-axis aspheric surface, then the silicon carbide plate with the rough initial off-axis aspheric surface is polished by adopting the prestress polishing technology, and finally the final off-axis aspheric surface with high finish degree is achieved. The method has the advantages that the material to be removed is few, the polishing speed is doubled, and the problem that the off-axis aspheric silicon carbide thin plate reflector cannot be applied in a large batch can be solved. The manufactured off-axis aspheric silicon carbide reflector is applied to large-scale foundation astronomical telescopes and space telescopes.
Drawings
FIG. 1 is a flow chart of a method for making an off-axis aspheric silicon carbide reflector of the present invention.
Fig. 2 is a schematic operation diagram of a second step of the method for manufacturing an off-axis aspheric silicon carbide reflector according to the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples.
The invention discloses a preparation method of an off-axis aspheric silicon carbide reflector, which comprises the following steps as shown in figure 1:
step one, taking a silicon carbide flat plate, and processing one surface of the silicon carbide flat plate into an initial off-axis aspheric surface through milling to obtain a semi-finished reflector 1.
A silicon carbide flat plate is taken, the thickness and the size of the flat plate are not limited, and the flat plate is determined according to the caliber, the off-axis amount and the curvature radius of an off-axis aspheric surface (called a target off-axis aspheric surface for short) of an ideal target reflector, and the target reflector of the embodiment has the caliber of 350mm and the thickness of 10 mm. And milling the lower surface of the silicon carbide flat plate according to the selected thickness of the silicon carbide flat plate and the thickness of the target reflector to change the thickness of the silicon carbide flat plate. And processing the upper surface of the silicon carbide flat plate into an initial off-axis aspheric surface by milling according to the target off-axis aspheric surface. The spherical aberration term coefficient, the coma aberration term coefficient and the astigmatism term coefficient of the initial off-axis aspheric surface shape and the target off-axis aspheric surface shape are the same, other high-order terms change along with the milling process, and the specific precision is not considered and is not limited. The precision achievable by milling is typically of the order of a few tens of micrometers, when the upper surface of the mirror blank 1 is a rough surface with respect to the following step two. And milling to obtain a semi-finished product of the reflector, namely obtaining the silicon carbide reflector with the initial off-axis aspheric surface.
And step two, polishing the initial off-axis aspheric surface by adopting a prestress processing technology to obtain a final off-axis aspheric surface, and finishing the manufacture of the off-axis aspheric surface silicon carbide reflector.
As shown in fig. 2, polishing the initial off-axis aspheric surface of the semi-finished reflector 1 by using a pre-stress processing technology according to the target off-axis aspheric surface to obtain a final off-axis aspheric surface, so as to obtain the off-axis aspheric silicon carbide reflector, wherein the off-axis aspheric surface silicon carbide reflector is manufactured, the final off-axis aspheric surface has a surface shape accuracy RMS of not higher than 300nm, and the final off-axis aspheric surface has a surface shape accuracy RMS of 200-300 nm in the embodiment.
According to the technical scheme, the method for preparing the off-axis aspheric silicon carbide reflector disclosed by the invention has the advantages that the initial off-axis aspheric surface is polished by the prestress polishing method, so that the problems that the hardness of the silicon carbide material is high, the removal rate is low, the surface shape convergence is slow, and if the off-axis aspheric silicon carbide thin plate reflector is polished by the traditional prestress polishing technology, the time used for polishing the off-axis aspheric silicon carbide thin plate reflector is more than 5 times that of the polished glass reflector, the efficiency is extremely low, and the high efficiency advantage of prestress polishing cannot be exerted are solved. The surface of the silicon carbide flat plate is pre-processed by adopting a mature mechanical milling and grinding processing technology without changing the original pre-stress polishing technology and equipment, so that the surface of the silicon carbide flat plate becomes a rough surface of a desired target off-axis aspheric surface shape to form an initial off-axis aspheric surface. Then, polishing the silicon carbide plate with the rough initial off-axis aspheric surface by adopting a prestress polishing technology, and finally achieving the off-axis aspheric surface with high finish. Only the burr part on the surface needs to be removed, the material needing to be removed is few, the polishing speed is accelerated in a multiple way, and the problem that the off-axis aspheric silicon carbide thin plate reflector cannot be applied in a large batch can be solved. The off-axis aspheric silicon carbide reflector manufactured by the method is applied to large-scale foundation astronomical telescopes and space telescopes.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (5)
1. A preparation method of an off-axis aspheric silicon carbide reflector is characterized by comprising the following steps:
s1, taking a silicon carbide flat plate, and processing one surface of the silicon carbide flat plate into an initial off-axis aspheric surface through milling;
and S2, polishing the initial off-axis aspheric surface by adopting a prestress processing technology to obtain a final off-axis aspheric surface, and finishing the manufacture of the off-axis aspheric silicon carbide reflector.
2. The method of claim 1, wherein the initial off-axis aspheric surface and the target off-axis aspheric surface have the same spherical aberration, coma and astigmatism coefficients.
3. The method of claim 1, wherein the final off-axis aspheric surface has a surface profile with an RMS of 200-300 nm.
4. The method of claim 1, wherein said S1 further comprises milling the other surface of the silicon carbide plate according to the thickness of the target reflector.
5. An off-axis aspherical silicon carbide mirror produced by the method for producing an off-axis aspherical silicon carbide mirror according to any one of claims 1 to 4.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010205914.7A CN111390652A (en) | 2020-03-23 | 2020-03-23 | Preparation method of off-axis aspheric silicon carbide reflector |
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| CN202010205914.7A CN111390652A (en) | 2020-03-23 | 2020-03-23 | Preparation method of off-axis aspheric silicon carbide reflector |
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Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103737451A (en) * | 2014-01-08 | 2014-04-23 | 中国科学院长春光学精密机械与物理研究所 | Grinding wheel home position automation shaping and milling processing method of off-axis aspheric reflector |
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- 2020-03-23 CN CN202010205914.7A patent/CN111390652A/en active Pending
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103737451A (en) * | 2014-01-08 | 2014-04-23 | 中国科学院长春光学精密机械与物理研究所 | Grinding wheel home position automation shaping and milling processing method of off-axis aspheric reflector |
Non-Patent Citations (1)
| Title |
|---|
| 大口径离轴非球面镜预应力环抛方法研究: "李新南，章海鹰，崔向群等", 《天文学报》 * |
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