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Proceedings Paper

Development of a nanoprofiler using the follow-up normal vector to the surface for next-generation ultraprecise mirrors
Author(s): Koji Usuki; Takao Kitayama; Hiroki Matsumura; Takuya Kojima; Junichi Uchikoshi; Yasuo Higashi; Katsuyoshi Endo
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Paper Abstract

Ultraprecise aspherical mirrors that offer nanofocusing and high coherence are indispensable for developing third-generation synchrotron radiation and X-ray free electron laser sources. In industry, the extreme ultraviolet (wavelength: 13.5 nm) lithography used for high-accuracy aspheric mirrors is a promising technology for fabricating semiconductor devices. In addition, ultraprecise mirrors with a radius of curvature of less than 10 mm are needed in many digital video instruments. We developed a new type of nanoprofiler that traces the normal vector of a mirror’s surface. The principle of our measuring method is that the normal vector at each point on the surface is determined by making the incident light beam on the mirror surface and the reflected beam at that point coincide, using two sets of two pairs of goniometers and one linear stage. From the acquired normal vectors and their coordinates, the three-dimensional shape is calculated by a reconstruction algorithm. The characteristics of the measuring method are as follows. The profiler uses the straightness of laser light without using a reference surface. Surfaces of any shape can be measured, and there is no limit on the aperture size. We calibrated this nanoprofiler by considering the system error resulting from the assembly error and encoder scale error, and evaluated the performance at the nanometer scale. We suppressed the effect of random errors by maintaining the temperature in a constant-temperature room within ±0.01°C. We measured a concave spherical mirror with a radius of curvature of 400 mm and a flat mirror, and compared the results with those obtained using a Fizeau interferometer. The profiles of the mirrors were consistent within the range of system errors.

Paper Details

Date Published: 18 December 2012
PDF: 8 pages
Proc. SPIE 8550, Optical Systems Design 2012, 85500P (18 December 2012);
Show Author Affiliations
Koji Usuki, Osaka Univ. (Japan)
Takao Kitayama, Osaka Univ. (Japan)
Hiroki Matsumura, Osaka Univ. (Japan)
Takuya Kojima, Osaka Univ. (Japan)
Junichi Uchikoshi, Osaka Univ. (Japan)
Yasuo Higashi, High Energy Accelerator Research Organization (Japan)
Katsuyoshi Endo, Osaka Univ. (Japan)

Published in SPIE Proceedings Vol. 8550:
Optical Systems Design 2012
Laurent Mazuray; Daniel G. Smith; Jean-Luc M. Tissot; Tina E. Kidger; Frank Wyrowski; Stuart David; Rolf Wartmann; Jeffrey M. Raynor; Andrew P. Wood; Pablo Benítez; Andreas Erdmann; Marta C. de la Fuente, Editor(s)

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