Recording/reproducing optical head producing focusing error sign

Details Recording/reproducing optical head producing focusing error sign Recording/reproducing optical head producing focusing error sign

1993-11-19

1995-04-04

Psitos, Aristotelis

Dynamic information storage or retrieval

With servo positioning of transducer assembly over track...

Optical servo system

369 4423, 369 4441, 369109, 369112, 369110, G11B 700

Patent

active

054043441

ABSTRACT:
A recording/reproducing optical head capable of causing a light spot on a photodetector for detecting a focusing error signal to stand still without being affected by variations in wavelength of light used, capable of adjusting a tracking error signal independently of the focusing error signal, and capable of utilizing light having an order of diffraction of -1 for the purpose of detecting a signal, in which a cylindrical lens for generating astigmatism and a diffraction grating made up of two regions different in the direction of diffraction or the angle of diffraction from each other are interposed between a beam splitter and a photodetector, a light beam diffracted from the diffraction grating and including the diffracted light of the zero-th order (that is, light which has passed through the diffraction grating without being deflected) is received by the photodetector, the diffracted light of the zero-th order is used for detecting a focusing error signal according to the astigmatism method, and diffracted light having an order of diffraction of +1 and diffracted light having an order of diffraction of -1 are used for detecting a tracking error signal.

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patent: 4951274 (1990-08-01), Iwanaga et al.
patent: 4970710 (1990-11-01), Lee
patent: 5095477 (1992-03-01), Shimozawa

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