Objective lens and optical head apparatus using the objective le

Details Objective lens and optical head apparatus using the objective le Objective lens and optical head apparatus using the objective le

1995-12-11

1997-11-04

Epps, Georgia Y.

Optical: systems and elements

Lens

Including a nonspherical surface

359710, 359711, 369112, G02B 302, G02B 306, G11B 700

Patent

active

056846410

ABSTRACT:
In an objective lens for an optical head apparatus for reading or writing an information on a recording medium such as optical disc, astigmatism is added on axial wavefront aberration so that off-axis astigmatism is to be cancelled by the axial astigmatism. At least one surface of the objective lens is a toric or cylindrical surface, and a standard deviation of astigmatism component of axial wavefront aberration is defined as Wa is to be restricted in a range of 0<Wa<0.07.lambda. (.lambda. is a wavelength of a light to be used). When the objective lens moves in a radial direction of the optical disc, a light beam enters into the objective lens in an off-axis region where the aberration is compensated by the axial astigmatism.

REFERENCES:
patent: 4789978 (1988-12-01), Shikama et al.
patent: 4886959 (1989-12-01), Hoshi
patent: 4968874 (1990-11-01), Kosuga
patent: 5535058 (1996-07-01), Tanaka et al.
"Principles of Optical Disc Systems", Published 1985 (Reprinted 1986) .COPYRGT.Adam Hilger Ltd. 1985, pp. 70-85.

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