Object lens and optical head for reproducing data from optical d

Details Object lens and optical head for reproducing data from optical d Object lens and optical head for reproducing data from optical d

1996-12-26

1999-03-30

Swann, Tod R.

Dynamic information storage or retrieval

Specific detail of information handling portion of system

Radiation beam modification of or by storage medium

369 94, 369 4423, 369118, 369 4424, 369119, G11B 7135

Patent

active

058897488

ABSTRACT:
The objective lens has a numerical aperture NA=0.6 when reproducing a DVD having a thickness of 0.6 mm and NA=0.42 when reproducing a CD having a thickness of 1.2 mm. At a boundary of NA 0.42, a slight stepped portion is formed so as to establish a phase difference. In this case, a designed wavelength is 0.635 .mu.m, and an optimum designed substrate thickness of a central portion is approximately 0.8 mm. While the DVD is reproduced, wave front aberration is on the order of 0.025.lambda., and jitter contained in the reproduction signal of the CD is equivalent to the present jitter. As a consequence, such an objective lens and an optical head with employment of this objective lens are provided, which precisely reproduce signals from the CD having the substrate thickness of 1.2 mm, and the DVD having the substrate thickness of 0.6 mm.

REFERENCES:
patent: 5703862 (1997-12-01), Lee et al.
Optical Review, vol. 1, No. 1, 1994, "Dual Focus Optical Head for 0.6 mm and 1.2 mm Disks", Komma et al. pp, 27-29.
Mitsubishi Denki New Release Development, No. 9507 (Jun., 21, 1995)

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