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Proceedings Paper

Measuring spherical aberration for the dynamic compensation of substrate-thickness errors
Author(s): Takeshi Shimano; Tetsuo Ariyoshi; Mariko Umeda; Takeshi Maeda; Hirofumi Sukeda; Takuji Nomura; Kouichi Murata
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Paper Abstract

In high-density optical disc systems that use high-NA objective lenses and multi-layered discs, it is important to reduce spherical aberration (SA). With high-NA lenses, SA is induced by errors in substrate thickness. The distance between layers in multi-layered discs also leads to SA. To use a type of phase-shifting device as a dynamic compensator for SA, a method of differential focus-error detection has been proposed for the real-time measurement of SA as a spherical aberration signal (SAS). The derivation of an equivalent substrate-thickness variation from the SAS with an accuracy of up to 0.8 mm is demonstrated in this paper. Using the SAS to drive a liquid-crystal phase-shifter, the fluctuation of the SAS caused by the substrate thickness error has been suppressed successfully during real-time disc rotation.

Paper Details

Date Published: 10 January 2002
PDF: 8 pages
Proc. SPIE 4342, Optical Data Storage 2001, (10 January 2002); doi: 10.1117/12.453393
Show Author Affiliations
Takeshi Shimano, Hitachi Ltd. (Japan)
Tetsuo Ariyoshi, Hitachi Ltd. (Japan)
Mariko Umeda, Hitachi Ltd. (Japan)
Takeshi Maeda, Hitachi Ltd. (Japan)
Hirofumi Sukeda, Hitachi Ltd. (Japan)
Takuji Nomura, Asahi Glass Co., Ltd. (Japan)
Kouichi Murata, Asahi Glass Co., Ltd. (Japan)

Published in SPIE Proceedings Vol. 4342:
Optical Data Storage 2001
Terril Hurst; Seiji Kobayashi, Editor(s)

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