Device for feedback controlling focus of an optical system in an

Details Device for feedback controlling focus of an optical system in an Device for feedback controlling focus of an optical system in an

1982-04-07

1985-03-12

McElheny, Jr., Donald E.

Dynamic information storage or retrieval

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

Mechanism control by the control signal

369 46, 369109, 369112, G11B 700

Patent

active

045049386

ABSTRACT:
In a feedback focus control system of an information recording/reproducing apparatus, an interference filter is disposed in the path of the light reflected at an optical disk so that the reflected light is transmitted through or reflected at the interference filter before it is received by a composite optical detector having a plurality of photosensitive elements. In one embodiment, the interference filter is inclined with respect to the optical axis so that the intensity of the transmitted or reflected light is positioned at a steep slope portion of an intensity vs phase difference characteristic curve. Two photosensitive elements are provided to detect the difference in intensity of the transmitted or reflected light at two portions on both sides of the optical axis. In another embodiment, an interference filter having two portions which are respectively inclined in opposite direction is used, while the optical detector comprises four photosensitive elements arranged in the form of four-quadrant. In another embodiment the light transmitted through the interference filter and light reflected at the same are respectively detected by two optical detectors each having two photosensitive elements.

REFERENCES:
patent: 3971002 (1976-07-01), Bricot et al.
patent: 4059841 (1977-11-01), Bricot et al.
patent: 4143402 (1979-03-01), Bricot et al.
patent: 4390781 (1983-06-01), Musha
patent: 4422168 (1983-12-01), Ito et al.
patent: 4423495 (1983-12-01), Musha et al.

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