The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Feb. 10, 1998
Filed:
Jun. 27, 1996
Sanyo Electrics Co., Ltd., Moriguchi, JP;
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.