CN110842658A - Combined processing method for controlling edge effect of irregular clear aperture reflector - Google Patents
Combined processing method for controlling edge effect of irregular clear aperture reflector Download PDFInfo
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- CN110842658A CN110842658A CN201911195767.3A CN201911195767A CN110842658A CN 110842658 A CN110842658 A CN 110842658A CN 201911195767 A CN201911195767 A CN 201911195767A CN 110842658 A CN110842658 A CN 110842658A
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- reflector
- milling
- polishing
- clear aperture
- edge effect
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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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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Grinding And Polishing Of Tertiary Curved Surfaces And Surfaces With Complex Shapes (AREA)
- Optical Elements Other Than Lenses (AREA)
Abstract
A combined processing method for controlling an edge effect of an irregular clear aperture reflector relates to the field of optical processing and solves the problems that the polishing method of the existing optical element has poor applicability, excessive material removal after polishing can cause the change of the integral stress of the reflector, and further the surface shape of the element is influenced.
Description
Technical Field
The invention relates to the field of optical processing, in particular to a combined processing method for controlling an edge effect of an irregular clear aperture reflector.
Background
With the development of optical systems to have larger visual fields and higher resolution, off-axis visual field reflective optical systems are more and more widely applied. The application of off-axis field-of-view reflective optical systems necessarily leads to an irregular clear aperture of the optical mirror element (no longer a circular or annular regular clear aperture), and the distance between the aperture requiring reflected light and the region requiring light transmission is also greatly limited, which puts new and higher requirements on the control of the mirror edge effect. For example, the most advanced current euv lithography machines employ an off-axis arc field of view and an optical system with a six-piece mirror structure (v.bakshi. euvlithograph, Second Edition [ M ].2018.), and in order to realize the reflection and the passage of light, the light-passing apertures of the optical elements are various, including conventional circular light-passing apertures, elliptical semi-regular light-passing apertures, and irregular light-passing apertures such as broad bean shapes. In designing an optical system, the distance between the region of the irregular clear aperture optical element that reflects light and the region that transmits light is an important parameter that affects the design of the optical system, and a balance needs to be struck between the optical design and the actual manufacturability of the element. Controlling the edge effects of non-regular clear aperture mirrors is a challenge in the fabrication of such mirrors. The conventional circular clear aperture optical element is processed by processes of rough grinding, fine grinding, polishing, edge grinding and the like. Before polishing, a sufficient machining allowance is reserved, and then a required diameter and an edge effect during polishing are removed by means of external grinding (Williamson R.field Guide to Optical fiber [ M ]. 2011.). For the irregular clear aperture reflector, the distance between the region of the reflective light and the region of the transmissive light does not allow too much processing margin to be retained, and due to the irregular nature of the regions, this conventional processing method is no longer suitable. Meanwhile, excessive material removal after polishing can cause changes in the overall stress of the reflector, thereby affecting the surface shape of the element.
Disclosure of Invention
The invention provides a combined processing method for controlling an edge effect of an irregular clear aperture reflector, aiming at solving the problems that the existing polishing method for optical elements has poor applicability, and the change of the integral stress of the reflector can be caused by excessive material removal after polishing, so that the surface shape of the element is influenced and the like.
A combined processing method for controlling edge effect of an irregular clear aperture reflector is realized by the following steps:
firstly, milling and grinding the surface of a reflector;
milling the surface of a reflector, milling the back of a light transmission area of the reflector, wherein in the milling process of the light transmission area of the reflector, milling is not required, a certain thickness of a material is required to be reserved, and the thickness is determined according to the size of the light transmission area required;
step two, polishing the surface of the reflector milled in the step one;
milling the reflector to a required shape again, and milling from the back of the reflector when milling the light transmission area of the reflector;
step four, removing the edge raised edges generated by the reflector in the step three in the process of milling the reflector by adopting a non-contact polishing method; obtaining the irregular clear aperture reflector.
The invention has the beneficial effects that: the combined processing method provided by the invention aims at the optical element of the irregular clear aperture reflector, and provides a combined processing method for controlling the edge effect.
Drawings
FIG. 1 is a process flow diagram of a combined processing method for controlling edge effect of an irregular clear aperture mirror according to the present invention.
Fig. 2 is a schematic structural diagram of an irregular clear aperture mirror in an embodiment of the present invention.
Fig. 3a is a schematic view of the mirror shape after milling in step one of the combined machining method for controlling the fringe effect of the irregular clear aperture mirror, and fig. 3b is a sectional view cut along the symmetry plane of the mirror element.
Detailed Description
First, the present embodiment is described with reference to fig. 1 to 3, and a combined processing method for controlling an edge effect of an irregular clear aperture reflector is disclosed, as shown in fig. 2, a distance between an effective clear aperture edge (a dotted ellipse) of a reflecting surface S of the element and an edge of a hole requiring light transmission is small, and an edge effect cannot be controlled by a conventional processing method of milling the reflecting surface S into a final shape and then polishing the reflecting surface S. The combined processing steps adopting the embodiment are as follows:
firstly, milling and grinding the shape and the surface of a reflector;
the reflector is made of a round cake-shaped glass blank material before being processed, redundant parts of the glass blank material are removed through shape and surface milling, the structure shown in the figure 3 is formed, in the step of milling, the polished reflecting surface keeps a complete surface, and sufficient polishing allowance is reserved outside the effective clear aperture of the reflecting surface S, so that polishing is facilitated. Meanwhile, holes needing light transmission are milled and ground from the back, the thickness of the material reserved in the area needing light transmission is determined according to the size of the light transmission area, and the ratio of the thickness to the size of the reserved material is 1: 5 to 1: 10, in the present embodiment, the ratio of the thickness of the retention material to the size of the light-transmitting region is preferably 1: 10 (thinnest part), the retained material with too small thickness is easy to deform in the polishing process and is not beneficial to polishing, the retained material with too large thickness needs to be removed more materials after polishing, and the deformation is easy to cause. In this embodiment, both the deformation of the material during polishing and the large deformation caused by the removal of a large amount of material again after polishing are considered.
Step two, polishing the surface of the reflector;
in the milling process of the first step, because enough machining allowance is reserved and a relatively complete reflector surface is reserved, the edge effect of the polishing process can be controlled to be beyond the clear aperture. The technical means adopted for polishing the surface of the reflector comprises various commonly used computer-controlled polishing means, and the polishing means comprises air bag polishing, asphalt polishing, jet flow polishing and the like.
Milling the reflector to a required shape again, and milling a region needing light transmission;
when the area needing light transmission is milled, the mirror is milled from the back of the reflector, and the purpose is to control the edge of the mirror caused in the milling process to be warped instead of collapsed.
Step four, removing the raised edges of the edges by adopting a processing mode without generating an edge effect;
non-contact polishing does not produce edge effects during polishing, but the processing efficiency is low. In the third step of the processing method, the generated edge is warped, the removal amount required by modification is small, and the non-contact polishing method is suitable for the third step. Therefore, the polishing means that can be used in this embodiment includes ion beam polishing and magnetorheological polishing to obtain the irregular clear aperture mirror.
Claims (3)
1. A combined processing method for controlling edge effect of an irregular clear aperture reflector is characterized by comprising the following steps: the method is realized by the following steps:
firstly, milling and grinding the surface of a reflector;
milling the surface of a reflector, milling the back of a light transmission area of the reflector, wherein in the milling process of the light transmission area of the reflector, milling is not required, a certain thickness of a material is required to be reserved, and the thickness is determined according to the size of the light transmission area required;
step two, polishing the surface of the reflector milled in the step one;
milling the reflector to a required shape again, and milling from the back of the reflector when milling the light transmission area of the reflector;
step four, removing the edge raised edges generated by the reflector in the step three in the process of milling the reflector by adopting a non-contact polishing method; obtaining the irregular clear aperture reflector.
2. The combined machining method for controlling the edge effect of the irregular clear aperture reflector according to claim 1, wherein the method comprises the following steps: in the first step, the ratio of the thickness of the reserved material to the size of the light transmission region is 1: 5 to 1: 10, respectively.
3. The combined machining method for controlling the edge effect of the irregular clear aperture reflector according to claim 1, wherein the method comprises the following steps: in the second step, the method for polishing the surface of the reflector is any one of air bag polishing, asphalt polishing or jet polishing.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201911195767.3A CN110842658B (en) | 2019-11-28 | 2019-11-28 | Combined processing method for controlling edge effect of irregular clear aperture reflector |
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| CN201911195767.3A CN110842658B (en) | 2019-11-28 | 2019-11-28 | Combined processing method for controlling edge effect of irregular clear aperture reflector |
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| CN110842658A true CN110842658A (en) | 2020-02-28 |
| CN110842658B CN110842658B (en) | 2021-03-30 |
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Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3660947A (en) * | 1971-01-25 | 1972-05-09 | Ingersoll Milling Machine Co | Method and apparatus for turning workpieces |
| JPH09181886A (en) * | 1995-12-25 | 1997-07-11 | Futec Inc | Image pickup device |
| CN106475866A (en) * | 2016-10-26 | 2017-03-08 | 北京空间机电研究所 | A kind of large-diameter non-spherical reflecting mirror processing method eliminating edge effect |
| CN107775453A (en) * | 2017-09-05 | 2018-03-09 | 上海现代先进超精密制造中心有限公司 | A kind of high-accuracy processing method of strip speculum |
| CN107984303A (en) * | 2017-11-07 | 2018-05-04 | 中国科学院上海光学精密机械研究所 | The processing method of uniform thickness off-axis aspheric surface speculum |
| CN110039407A (en) * | 2019-05-28 | 2019-07-23 | 长光卫星技术有限公司 | A kind of fast polishing method effectively reducing mirror optics processing edge effect |
-
2019
- 2019-11-28 CN CN201911195767.3A patent/CN110842658B/en active Active
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3660947A (en) * | 1971-01-25 | 1972-05-09 | Ingersoll Milling Machine Co | Method and apparatus for turning workpieces |
| JPH09181886A (en) * | 1995-12-25 | 1997-07-11 | Futec Inc | Image pickup device |
| CN106475866A (en) * | 2016-10-26 | 2017-03-08 | 北京空间机电研究所 | A kind of large-diameter non-spherical reflecting mirror processing method eliminating edge effect |
| CN107775453A (en) * | 2017-09-05 | 2018-03-09 | 上海现代先进超精密制造中心有限公司 | A kind of high-accuracy processing method of strip speculum |
| CN107984303A (en) * | 2017-11-07 | 2018-05-04 | 中国科学院上海光学精密机械研究所 | The processing method of uniform thickness off-axis aspheric surface speculum |
| CN110039407A (en) * | 2019-05-28 | 2019-07-23 | 长光卫星技术有限公司 | A kind of fast polishing method effectively reducing mirror optics processing edge effect |
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| CN110842658B (en) | 2021-03-30 |
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