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:
Jun. 20, 1989
Filed:
Dec. 03, 1986
Toshimasa Kamisada, Hiratuka, JP;
Akira Saito, Odawara, JP;
Hitachi, Ltd., Tokyo, JP;
Abstract
An apparatus and method for identifying focus and tracking errors in an optical disk apparatus is provided. Reflections from the disk are generated using a conventional laser light source to produce an optical image including zero and first order diffraction rays. A cylindrical lens converges the image along a single axis to form an elliptical optical image having a major and minor axis and having first and second interference portions aligned along the major axis. A half-mirror type beam splitter splits the image into first and second images which are detected at first and second photodetectors each including first, second, third, and fourth photoreceptive portions. The first and second photoreceptor portions are spaced along the minor axis, the first and fourth photoreceptor portions are spaced along the major axis. The photoreceptors are spaced forward and behind a converging focus point so that the image is converging towards one photodetector and diverging at the second photodetector. Differences that are identified in photoreception between the first and second photoreceptive portions as representative of focus error and differences in photoreception between the third and fourth photoreceptive portions are representative of tracking error.