Critical angle focus error detector

Details Critical angle focus error detector Critical angle focus error detector

1995-06-02

1997-05-13

Westin, Edward P.

Radiant energy

Photocells; circuits and apparatus

Photocell controls its own optical systems

2502082, 369 4441, G01J 120, G11B 700

Patent

active

056295146

ABSTRACT:
A focus error detector for detecting a signal representing a degree of a focus error of an objective lens with respect to an optical disk in an optical pickup, in order to eliminate errors due to an optical axis shift or tilt of the reflected light reflected from the optical disk, includes a diffraction device for diffracting and splitting the reflected light reflected. The focus error detector a critical angle reflector having critical angle reflecting planes for reflecting the two diffracted light rays at two critical angles, two bi-segmented photo-detectors for receiving the two diffracted light rays reflected from the critical angle reflector, respectively, and detecting signals depending on the received light amount, and a circuit for differentiating and summing each signal of the two bi-segmented photo-detectors so as to offset the light amount difference due to the tilt or shift of the reflected light and outputting a desired signal. Therefore, only an original focus error signal is output, irrespective of an optical shift or tilt of the reflected light, so that malfunction of the optical pickup is prevented and clean recording and reproduction is enabled.

REFERENCES:
patent: 5243585 (1993-09-01), Hoshino et al.
patent: 5353267 (1994-10-01), Katayama
patent: 5404490 (1995-04-01), Matsubayashi et al.
patent: 5453607 (1995-09-01), Ando et al.
patent: 5495461 (1996-02-01), Komma et al.

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