Dynamic information storage or retrieval – With servo positioning of transducer assembly over track... – Optical servo system
Patent
1996-04-29
1997-09-30
Tran, Thang V.
Dynamic information storage or retrieval
With servo positioning of transducer assembly over track...
Optical servo system
369112, 369 4441, 369 4442, 369103, G11B 709
Patent
active
056732414
ABSTRACT:
The focus detection mechanism of the invention diffracts the return light reflected off target surface by means of holographic element. The diffracted beams are both received by two long photodetection means as two astigmatic convergent beams that forms circles of least confusion on the same plane near focal plane of a lens. The focus detection signal is obtained from differential output of them. Since the mechanism can form two diffracted beams having circles of least confusion on the same plane, the photodetection means for detection can be disposed side by side, thus simplifying production with increased dimensional accuracy. Also, although a holographic element is used, wavelength fluctuation can be absorbed to provide extremely high reliability.
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Proc. Int. Symp. on Optical Memory, No Month 1987; Japanese Journal of Applied Physics, vol. 26 (1987) Supplement 26-4; "A Multi-Functional Reflection Type Grating Lens for the CD Optical Head" by Kenji Tatsumi, Tadashi Matsushita, and Syo Ito; Mitsubishi Electric Corporation, 5-1-1 Ofuna, Kamakura City 247, Japan, pp. 127-130.
Arimura Toshio
Koyama Fumio
Sakata Hidefumi
Takeda Takashi
Yokoyama Osamu
Seiko Epson Corporation
Tran Thang V.
Watson Mark P.
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