Dynamic information storage or retrieval – Control of storage or retrieval operation by a control... – Mechanism control by the control signal
Patent
1985-06-14
1987-07-21
Faber, Alan
Dynamic information storage or retrieval
Control of storage or retrieval operation by a control...
Mechanism control by the control signal
369 46, 369110, 250201, G11B 709
Patent
active
046823158
ABSTRACT:
A focussing error detection device for use in a optical disk type recording system wherein a light beam is converged by objective lens means onto a recording surface of the disk and wherein the light beam reflected by said recording surface is divided by a first beam divider interposed between said objective lens means and a light beam source. The improvement comprises a second beam divider for further dividing the light beam divided by said first beam divider into central light beam fraction and a peripheral light beam fraction, a first photo detector for detecting the quantity of the central light beam fraction, a second photo detector for detecting the quantity of the peripheral light beam fraction, and a subtracter for indicating the difference between the output from the first photo detector and the second photo detector.
REFERENCES:
patent: 4152586 (1979-05-01), Elliott
patent: 4504938 (1985-03-01), Tajima
patent: 4546463 (1985-10-01), Ophey
Faber Alan
Fuji Photo Film Co. , Ltd.
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