Dynamic information storage or retrieval – Specific detail of information handling portion of system – Radiation beam modification of or by storage medium
Patent
1996-06-27
1998-02-10
Edun, Muhammad N.
Dynamic information storage or retrieval
Specific detail of information handling portion of system
Radiation beam modification of or by storage medium
369109, 369112, 369 4412, 359562, G11B 700
Patent
active
057176744
ABSTRACT:
An optical pickup apparatus includes a semiconductor laser generating a light having a short wavelength for reproduction of a high-density information recording medium and a semiconductor laser outputting a light for reproduction of an information recording medium with low recording density. A three-beam generating diffraction grating, a transmission type holographic optical element and a condenser lens are disposed in the light path in which the laser lights from the semiconductor lasers propagate toward the recording surface of an information recording medium. The laser light emitted from each semiconductor laser is transmitted through the three-beam generating diffraction grating and divided into three beams and then transmitted through the transmission type holographic optical element and passed through the condenser lens to reach the recording surface of the information recording medium. The transmission type holographic optical element is formed so that the product of the diffraction efficiency of the laser light in the forward optical path and the separated diffraction efficiency of the returned light increases as the wavelength of the laser light decreases. The three-beam generating diffraction grating has grooves with such depth that the diffraction efficiency of the main beam in the three-divided beams is smaller and the diffraction efficiency of the sub-beams is larger as the wavelength of the laser light is shorter.
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Inoue Yasuaki
Mori Kazushi
Tajiri Atsushi
Edun Muhammad N.
Sanyo Electrics Co., Ltd.
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