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:
Jan. 26, 1999
Filed:
Jun. 18, 1997
Nobuo Takeshita, Nagaokakyo, JP;
Teruo Fujita, Nagaokakyo, JP;
Mitsubishi Denki Kabushiki Kaisha, Tokyo, JP;
Abstract
In an optical disk device for recording or playing back information on or from an optical information recording medium having land parts forming information tracks and groove parts interposed between adjacent land parts, the land part is illuminated with a first light spot, and the groove part is illuminated a second light spot, a first focus error signal is produced in accordance with the reflected light beam of the first light spot, and a second focus error signal is produced in accordance with the reflected light beam of the second light spot, and focus control is performed in accordance with the first and second focus error signals. In another aspect of the invention, each of the light receiving sections of a photodetector used for receiving the reflected light has an array of tapered projections along in a region between main parts the light receiving sections, and the tapered projections of the light receiving sections are interdigitated with each other. Improved devices for tilting the objective lens is also provided.