Optical disk having reduced track pitch and optical disk playbac

Details Optical disk having reduced track pitch and optical disk playbac Optical disk having reduced track pitch and optical disk playbac

1996-10-30

1998-01-13

Neyzari, Ali

Dynamic information storage or retrieval

Storage medium structure

Optical track structure

3692753, G11B 724

Patent

active

057086516

ABSTRACT:
An optical disk comprises a substrate, and a recording layer which is formed on the substrate and on which information is recorded at specific pitches in the form of pit trains, wherein the information is reproduced by projecting a light beam via an object lens, and when the wavelength of the light beam is .lambda. .mu.m and the numerical aperture of the object lens is NA, the track pitch is set in the range of (0.72 to 0.8).times..lambda./NA/1.14 .mu.m, and each of the pits has a trapezoid cross section whose upper width is in the range of (0.3 to 0.5).times..lambda./NA/1.14 .mu.m and whose lower width is in the range of (0.2 to 0.32).times..lambda./NA/1.14 .mu.m or whose inner wall has an angle of 30.degree. to 70.degree..

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Jozef Braat, Principles of Optical Disc Systems, Ch.2, "Read-out of Optical Discs", Sec. 2.2.3, 1985, pp. 17-19.
Terao et al, Fundamentals of Optical Memory, "Recordable and Erasable Optical Memory Medium", 1990, pp. 60-61.
K. Yamada et al, "Tracking Method for Optical Disk Systems with Composite Detection", Abstracts of Lectures given at the 54th Meeting of the Japanese Society of Applied Physics Sep. 27, 1993, 28a-SF-16, p.1009.
Sugaya et al., "Performance of a 600 Mbyte 90 mm Phase-Change Optical Disk against Disk Tilt", Jpn. J. Appl. Phys., vol. 32 (1993), pp. 5402-5405.

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