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:
Apr. 17, 1990
Filed:
May. 18, 1987
Akihiko Hashimoto, Hachioji, JP;
Toshihiro Kitahara, Akishima, JP;
Hiroshi Hashi, Higashimurayama, JP;
Takao Rokutan, Koganei, JP;
Olympus Optical Co., Ltd., , JP;
Abstract
An apparatus for reading and writing a data signal from and on an optical card including an optical head having a semiconductor laser for emitting a writing light beam, a light emitting diode for emitting a reading light beam, a first object lens for projecting the reading light spots onto the optical card, a second objective lens for projecting the reading light beam reflected by the optical beam onto a photodetector and a half mirror arranged in an optical axis of the second objecive lens, the first and second objective lens having inclined optical axes with respect to a surface of the optical card, a driving mechanism for feeding the optical card in its lengthwise direction, and a focusing control mechanism for moving the optical head in a direction normal to the surface of the optical card. The photodetector includes first and second detectors which are arranged to receive equally an image of a part of the optical card illuminated by the reading light beam only in a focused condition. By deriving a difference between the first and second detectors there is produced a focusing error in response to which the focusing control mechanism is driven to correct the focusing error.