1988 Fiscal Year Final Research Report Summary
Development of null test measurement system of aspherical mirror shape by scatter plate interferometer
| Project/Area Number |
62850004
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| Research Category |
Grant-in-Aid for Developmental Scientific Research
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| Allocation Type | Single-year Grants |
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| Research Field |
物理計測・光学
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| Research Institution | Tokyo Institute of Technology |
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Principal Investigator |
HONDA Toshio Associate Professor:Faculty of Engineering, Imaging Science & Engineering Labora, 工学部, 助教授 (10016503)
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| Co-Investigator(Kenkyū-buntansha) |
OHYAMA Nagaaki Associate Professor:Faculty of Engineering, Imaging Science & Engineering Labora, 工学部, 助教授 (50160643)
本田 捷夫 東京工業大学, 工学部, 助教授 (10016503)
TSUJIUCHI Jumpei Professor:Faculty of Engineering, Imaging Science & Engineering Laboratory, 工学部, 教授 (90016254)
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| Project Period (FY) |
1987 – 1988
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| Keywords | Scatter Plate interferometer / null test / zone-plate / common path / conic aspherical surface / fringe scan / fringe-analysis / 縞画像処理 / 偏光干渉 / PZT / 形状回帰 |
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| Research Abstract |
Main-mirror of big astronomical telescope has concave and rotationally symmetric aspherical shape. The performance of the telescope is greatly influenced by the precision of the shape of the mirror.
As a method for measuring the surface shape and/of the characteristics of optical systems, conventional interferometers have been widely used. But, if the conventional interferometer such as Twyman-Green one is used, many interference fringes generate and the interval of fringes becomes very narrow when deep aspheric surface is measured.
For overcoming these defects, computer generated hologram ( CGH ) or special optical elements are used. But these interferometers are fundamentally different-path interferometers, and can not be used for aspheric surfaces with large aperture-size and long radius of curvature.
For the interferometric measurement of these surfaces, the common-path interferometric method is inevitable. So, the purpose of this research is to develop null-test scatter-plate interfe
… More
rometer for measuring concave deep aspheric surfaces with rotationally symmetry.
The scatter-plate interferometer is one of common-path interferometers, and the principle of null-test by this interferpometer is as follows. A scatter-plate with larger aperture size of which characteristics are point-symmetry are used and a pinhole is set apart from the position behind the scatter-plate. In this optical set-up, the reference wave-front becomes aspheric and can be made almost equal to the wave-front which is reflected from the aspheric concave mirror under test. As a result, null-test can be realized.
A zone-plate interferometer is also common-path interferometer and a specially optically made zone-plate can be regarded as equivalent with a scatter-plate when the zone-plate is used in the above mentioned interfero-meter instead of the scatter-plate.
In this researh, at first, the priciple of null-test on scatter-plate interferometer is made clear, and next, the relation between the scatter-plate and the zone-plate interferometer is compared. Then, two kinds of fringe-scanninig techniqes which can be applied to common-path interferometer are developed and practised. And finally, computer-controlled fringe pattern aquisition and analysis system is constructed. Less
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