Optical pick-up device using diffraction grating element having

Details Optical pick-up device using diffraction grating element having Optical pick-up device using diffraction grating element having

1990-05-11

1992-05-05

McElheny, Jr., Donald

Dynamic information storage or retrieval

With servo positioning of transducer assembly over track...

Optical servo system

369112, 369122, 369 4412, 369 4414, 359571, 359569, G11B 700, G11B 7013

Patent

active

051114496

ABSTRACT:
An optical pick-up device for focusing a laser beam emitted from a light emitting element through an optical system onto a recording medium. The beam is reflected from the recording medium and redirected through the same optical system on to a photodetector. A tracking error signal and a focusing error signal are produced from the output signals of the photo-detector. A diffracting element positioned before the light emitting element and the photo-detector and produces two sub-spots in two directions for applying the so-called 3-spots method from the laser beams that were projected from the light emitting element toward the recording medium. The diffracting element is divided into a first sub-region and a second sub-region formed in the same place and defined by a parting line aligned substantially perpendicular to the track direction. The first sub-region includes a diffraction grating for diffracting three beams that comprise a main beam toward the recording medium. The second sub-region includes a diffraction grating for diffracting the reflected beams of the three beams from the recording medium in the direction where the photo-detecting element is installed.

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patent: 4847478 (1989-07-01), Sugiura
patent: 4904856 (1990-02-01), Nagahama et al.
patent: 4945529 (1990-07-01), Ono et al.
patent: 4983002 (1991-01-01), Shikama et al.

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