Focus detection device for reading information from an optical r

Details Focus detection device for reading information from an optical r Focus detection device for reading information from an optical r

1992-12-23

1994-09-06

Nelms, David C.

Radiant energy

Photocells; circuits and apparatus

Photocell controls its own optical systems

367 4437, G01J 120, G11B 700

Patent

active

053450728

ABSTRACT:
A focus detection device for use in a focus detection device includes a main light source and two auxiliary light sources. These auxiliary light sources are offset to the main light source along the optical axis of the main optical system while being symmetrically positioned perpendicular to the optical axis. A exposure units having apertures are provided above the two auxiliary light sources for constricting the amount of auxiliary lights so that the convergence of the auxiliary beams on the optical disk is less than that of the main light beam. As a result, an optical system with a broad focus error detection range can be constructed while increasing the convergence of the main light beam.

REFERENCES:
patent: 3992574 (1976-11-01), Bouwhuis et al.
patent: 4973836 (1990-11-01), Matsuoka
patent: 5105076 (1992-04-01), Premji

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