Focus error detecting element and optical head using the same

Details Focus error detecting element and optical head using the same Focus error detecting element and optical head using the same

1993-08-20

1996-07-09

Sugarman, Scott J.

Optical: systems and elements

Lens

Including a nonspherical surface

359719, G02B 1318

Patent

active

055350585

ABSTRACT:
An optical system for detecting a focus error signal in an optical disc according to the astigmatic method is constituted by a single lens element. This lens element has a first lens surface defined by a toric surface effective to converge the incident rays of light and also to produce an astigmatism. This lens element also has a second lens surface which has a negative power so as to form a telephoto optical system, making it possible to shorten the length of the optical system.

REFERENCES:
patent: 4027952 (1977-06-01), Hugues
patent: 4501493 (1985-02-01), Kubota
patent: 4504128 (1985-03-01), Guilino et al.
patent: 4641296 (1987-02-01), Mizunoe et al.
patent: 4900138 (1990-02-01), Atkinson, III et al.
patent: 4915484 (1990-04-01), Yamamoto
patent: 4938573 (1990-07-01), Saito
patent: 4968874 (1990-11-01), Kasuga
patent: 4986641 (1991-01-01), Braat
patent: 5095477 (1992-03-01), Shimozawa
"Principles of Optical Disc Systems", Bouwhuis et al., 1985, pp. 79-80.

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