Focusing error detecting apparatus with light switching and dete

Details Focusing error detecting apparatus with light switching and dete Focusing error detecting apparatus with light switching and dete

1989-07-10

1991-04-02

Nelms, David C.

Radiant energy

Photocells; circuits and apparatus

Photocell controls its own optical systems

369 4424, G01J 120

Patent

active

050049003

ABSTRACT:
A focusing error detecting apparatus comprises an objective lens system for focusing a ray flux on a surface of an optical recording disk, two photo detectors, an optical means including the lens system and a beam splitter, for focusing a ray flux reflected from the optical recording disk so that the ray flux comes to the middle of a space formed between the two photo detectors when the focal point is formed on the optical recording disk, a combination of two interruption/deflection elements and a control device for switching the ray flux transmitted from the optical recording disk at the two positions which correspond to said two photo detectors, two sampling/holding circuits respectively hold differences of output of the two photo detectors in correspondence to the switching operations of the interruption/deflection elements and the control device, and a subtracting circuit for outputting a focusing error signal on the basis of the outputs of the sampling/holding circuit.

REFERENCES:
patent: 4363961 (1982-12-01), Okada et al.
patent: 4654515 (1987-03-01), Ando 250201.5
Patent Abstracts of Japan, vol. 11, No. 248 (P-604)[2695], Aug. 13th, 1987; & JP-A-62 54 224 (Olympus Optical Co., Ltd.), 09/03/87, *Whole Abstract*.

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