Magneto-optic pickup head including tracking and focusing error

Details Magneto-optic pickup head including tracking and focusing error Magneto-optic pickup head including tracking and focusing error

1988-04-20

1989-09-19

Richardson, Robert L.

Dynamic information storage or retrieval

With servo positioning of transducer assembly over track...

Optical servo system

369 45, 369 13, 360114, G11B 700

Patent

active

048688037

ABSTRACT:
A pickup apparatus for a magneto-optical recording medium comprises the first and second waveguides lying one upon the other for receiving a light beam reflected by a magneto-optical recording medium, and first and second focusing grating couplers disposed on the first waveguide for introducing the reflected light beam into the first waveguide in the same guided mode. A third focusing grating coupler is disposed for introducing the reflected light beam into the second waveguide in a different guided mode. First, second and third photodetectors are secured to the first or second waveguide for detecting the optical waves converged by the first, second and third 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 a difference between the output of the first and/or second photodetector and an output of the third photodetector.

REFERENCES:
patent: 3877784 (1975-04-01), Lin
patent: 4626679 (1986-12-01), Kuwayama et al.
patent: 4758062 (1988-07-01), Sunagawa et al.

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