Focusing error detection apparatus

Details Focusing error detection apparatus Focusing error detection apparatus

1988-01-07

1990-04-24

McElheny, Jr., Donald

Dynamic information storage or retrieval

Control of storage or retrieval operation by a control...

Mechanism control by the control signal

G11B 713

Patent

active

049205277

ABSTRACT:
A light beam focusing apparatus for maintaining a level of a focus error signal below an acceptable reference value. A trisection photodetector is provided, a level of a focus error signal being calculated in accordance with three photodetector outputs which result from a light beam striking the trisection photodetector. A distance dc which the light beam can deviate from a center of a central section of the trisection photodector while maintaining a level of the focus error signal below the acceptable reference value is determined in accordance with the formula 2r+dc>a+b+c, wherein r is the radius of the light beam striking the trisection photodetector, a is a width of the central section of the photodetector, and b and c are the respective widths of the other two sections of the photodetector.

REFERENCES:
patent: 4243848 (1981-01-01), Utsumi
patent: 4625303 (1986-11-01), Shikama et al.
patent: 4658391 (1987-04-01), Nozu et al.
patent: 4695158 (1987-09-01), Kotaka et al.
patent: 4724533 (1988-02-01), Ohara et al.
patent: 4725725 (1988-02-01), Ando
patent: 4815060 (1989-03-01), Nomura

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