Optical focus sensor

Details Optical focus sensor Optical focus sensor

1980-12-19

1983-04-26

Faber, Alan

Dynamic information storage or retrieval

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

Mechanism control by the control signal

369 46, 369118, 369120, 250201, G11B 712

Patent

active

043815570

ABSTRACT:
Recovery from a record of data recorded in an information track, comprising depressed areas of a given width, a given depth, and variable length, alternating along the length of the track with relatively non-depressed areas, is effected by an optical playback system. The playback system employs means for focusing light from a laser source on the information track as a light spot having a diameter which is diffraction limited. The focusing system includes an independent light source (e.g., laser) which impinges on the surface of the record as a circular spot which illuminates a plurality of elongated tracks. The circular spot is imaged by a lens system on to a detector plane which is positioned at a plane which is conjugate to the record surface. The focus error signal which is used to adjust the position of the objective lens with respect to the record surface is representative of a measure of the diameter of the circular spot imaged on the detector plane, and, thus, is a measure of the diameter of the circular spot at the record surface.

REFERENCES:
patent: 4085423 (1978-04-01), Tsunodo
patent: 4152586 (1979-05-01), Elliott

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