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. 05, 1987
Filed:
Oct. 18, 1984
Kenjiro Hamanaka, Tokorozawa, JP;
Shinsaku Nozu, Tokorozawa, JP;
Katsuharu Sato, Tokorozawa, JP;
Hozumi Tanaka, Tokorozawa, JP;
Pioneer Electronic Corporation, Tokyo, JP;
Abstract
A focus error detection device to be used in an optical system for recording and/or playing back information, including a light detector made up of four light receiving elements arranged symmetrically with respect to the center of the light detector, a multiplication means for generating a pair of multiplication signal by multiplying output signals of two light receiving elements which are arranged symmetrically with respect to the center of the light detector. The multiplication signals are applied to a subtraction means where the focus error signal is generated by the subtraction between the multiplication signals. Thereby the off-set of the focus error signal which has been caused by the deviation of the position of the center of the light beam from the center of the light detector is by far reduced.