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:
Mar. 05, 1991
Filed:
Nov. 14, 1988
Applicant:
Inventors:
Hiromichi Ishibashi, Toyonaka, JP;
Shinichi Tanaka, Kyoto, JP;
Akira Matsubara, Takatsuki, JP;
Tsuyoshi Okada, Yokohama, JP;
Assignee:
Matsushita Electric Industrial Co., Ltd., Kadoma, JP;
Attorney:
Primary Examiner:
Int. Cl.
CPC ...
G11B / ;
U.S. Cl.
CPC ...
369 4436 ; 369 4441 ;
Abstract
An apparatus is described for reading/writing an optical recording carrier, which have information pits aligned in a track. In order to get a focus error signal, the apparatus has two pairs of photo sensor elements, two phase detection circuits for the two pairs of photo sensor elements, and an adder circuit for adding outputs of the two phase detection circuits. The elements are placed symmetrically about an optical axis in a far field area of the pits.