Optical pickup apparatus for detecting and correcting focusing a

Details Optical pickup apparatus for detecting and correcting focusing a Optical pickup apparatus for detecting and correcting focusing a

1991-05-17

1992-10-06

Nguyen, Hoa

Dynamic information storage or retrieval

Storage or retrieval by simultaneous application of diverse...

Magnetic field and light beam

360 59, 360114, 369112, 369110, G11B 1304, G11B 1114

Patent

active

051538601

ABSTRACT:
A pickup apparatus for a magneto-optical recording medium comprises a waveguide for receiving a light beam reflected by a magneto-optical recording medium, and first and second focusing grating couplers disposed side by side on the waveguide for introducing the reflected light beam into the waveguide in a TE or TM guided mode and converging the thus guided optical waves at two positions spaced from each other. First and second photodetectors are mounted on the waveguide for detecting the optical waves converged by the first and second focusing grating couplers. Tracking error and focusing error are detected based on the outputs of the first and second photodetectors, and recorded signals are detected based on the output of the first photodetector and/or the output of the second photodetector. In another embodiment, three focusing grating couplers are disposed on two waveguides.

REFERENCES:
patent: 4672187 (1987-06-01), Fujita et al.
patent: 4718052 (1988-01-01), Kondo et al.
patent: 4733065 (1988-03-01), Hoshi et al.
patent: 4737946 (1988-04-01), Yamashita et al.
patent: 4779259 (1988-10-01), Kono et al.
patent: 4797867 (1989-01-01), Sunagawa et al.
patent: 4833561 (1989-05-01), Sunagawa et al.

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