Optical pickup apparatus for phase changing optical disk

Details Optical pickup apparatus for phase changing optical disk Optical pickup apparatus for phase changing optical disk

1992-10-06

1995-09-12

Young, W. R.

Dynamic information storage or retrieval

With servo positioning of transducer assembly over track...

Optical servo system

369 4437, G11B 7095

Patent

active

054503876

ABSTRACT:
An optical disk reproducing apparatus for optical disks which are have a material layer whose reflectivity is lowered when a temperature of this material exceeds a predetermined temperature, is fabricated on a transparent substrate. A plurality of phase pits have been formed in this substrate corresponding to an information signal. The optical disk reproducing apparatus comprises: an optical pickup for reading the information signal by irradiating on a recording plane of the optical disk, a first optical spot for reproducing the information signal, and also second and third optical spots each having lower light intensity than that of the first optical spot. The second and third optical spots located at positions where there is no adverse influence caused by a thermal history of the first optical spot. The optical disk reproducing apparatus further comprises tracking control unit for performing a tracking control of the optical pickup based upon a difference signal between detection signals derived from first and second photo detecting units of the optical pickup, for receiving light of the second and third optical spots reflected from the optical disk.

REFERENCES:
patent: 3876842 (1975-04-01), Bouwhuis
patent: 5070490 (1991-12-01), Endo
Patent Abstracts of Japan, vol. 16, No. 131, (P1332), Dec. 24, 1991, & JP3-292632.
Patent Abstracts of Japan, vol. 11, No. 354, (P638), Jun. 15, 1987 & JP62-132246.

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