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. 25, 1985
Filed:
Oct. 07, 1981
Kenichi Ito, Hachioji, JP;
Tohru Musha, Hachioji, JP;
Kiichi Kato, Hachioji, JP;
Kimiaki Yamamoto, Hachioji, JP;
Olympus Optical Co., Ltd., , JP;
Abstract
A method and an apparatus for detecting a focussing error signal and a tracking error signal of an objective lens with respect to an information track of a video disc on which a reading light spot is focussed by the objective lens includes a detection prism having a reflection surface which is set substantially at a critical angle and a light detector for receiving the light flux reflected by the reflection surface. The light detector is arranged in a far field of the track and having four light receiving regions divided along two orthogonal directions. The focussing error signal is derived as a difference between output signals from the regions aligned in a track direction and the tracking error signal is derived as a difference between output signals from the regions aligned in a direction perpendicular to the track direction. An information signal is obtained as a sum of the output signals from the four regions.