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. 15, 1991
Filed:
Feb. 08, 1988
Hitachi, Ltd., Tokyo, JP;
Abstract
An optical card of the present invention has a card-shaped recording layer whose optical characteristic is varied by a laser beam applied thereon, and a resin layer for protecting this recording layer. The recording layer has optical grooves provided at a substantially equal interval in the opposite end portions of the recording layer respectively and varying the light intensity of the laser beam when the beam traverses the grooves, and first and second optical markers provided at a prescribed interval in the direction of extension of each of the optical grooves and varying the light intensity of the laser beam which passes them. The optical grooves are made longer every prescribed number thereof than others, and the longer optical grooves are used for zone access, while the shorter optical grooves are used for track access in a zone. The first and second optical markers are provided at positions deviated alternately at equal distance from the center of a track, and operate as so-called wobble pits to detect a track error. These markers are used also as timing marks for generating a clock signal.