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:
Sep. 16, 1980
Filed:
Apr. 08, 1977
Seiji Yonezawa, Hachioji, JP;
Teruichi Tomura, Kunitachi, JP;
Akira Fukuhara, Tachikawa, JP;
Keizo Kato, Hachioji, JP;
Masuo Umemoto, Hachioji, JP;
Hitachi, Ltd., , JP;
Abstract
In order to record information spirally on a disk and to reproduce the recorded information accurately without any contact, at the recording, an information signal and a predetermined signal for synchronous detection are added together, the resultant signal is subjected to frequency modulation and, while a laser beam intensity-modulated by the frequency-modulated signal is minutely swung in the radial direction of the rotating disk at the same frequency as that of the synchronous detection signal, it is caused to impinge on the disk to thereby record the information spirally on a recording medium of the disk without any contact. During the reproduction, as the disk is being rotated, a light spot is caused to impinge along an information groove formed on the disk, and reflected light or transmitted light from the disk is detected in the form of an electric signal. A synchronous detection signal is derived from the electric signal and an envelope signal of the electric signal is synchronously rectified by the use of the snychronous detection signal to thus detect the offset between the light spot and the information groove and, as the offset is being corrected, the information signal is reproduced.