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:
May. 03, 1988
Filed:
Feb. 11, 1986
Shigeru Nakamura, Hachioji, JP;
Toshimasa Kamisada, Hiratsuka, JP;
Akira Saito, Odawara, JP;
Takeshi Maeda, Kokubunji, JP;
Yoshito Tsunoda, Mitaka, JP;
Toshimitsu Kaku, Sagamihara, JP;
Tuyoshi Kato, Hachioji, JP;
Masaaki Hishiki, Odawara, JP;
Masateru Watanabe, Kanagawa, JP;
Hitachi, Ltd., Tokyo, JP;
Abstract
A focus error detection apparatus and an optical disk apparatus comprising a focusing lens for focusing reflected light coming from a light reflecting surface which is to be adjusted at the focal point of a projected light beam; a beam splitter means for dividing the output light of said focusing lens into a first and a second focused light beam; a first and a second photo-detector disposed respectively on the optical paths of said first and said second focused light beam, one of which is located behind the convergence point of said first focused light beam and the other of which is located before the convergence point of said second focused light beam, each of them generating outputs proportional to the amount of light within a predetermined region of the received light image, when it varies so that it is enlarged; and a circuit generating a focus error signal by using the difference between the outputs of said two photo-detectors.