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:
Dec. 23, 1986
Filed:
Jun. 16, 1983
Yoshihiro Utsumi, Tokorozawa, JP;
Pioneer Electronic Corporation, Tokyo, JP;
Abstract
A focus error detection device for use with a system for optically recording and reading out information, and which can produce a symmetrical focus error signal with respect to the amount of displacement of the reflecting surface of the recording medium from an in-focus position. A second cylindrical lens whose axial direction is perpendicular to the axial direction of a first cylindrical lens is provided, and lateral magnification between the position of the receiving surface of a photo detector and a conjugate plane, which is located adjacent to the in-focus position of the reflecting surface, is made uniform in each direction. By this feature, the output signal of the photo detector varies in a symmetric manner in both directions from the in-focus position of the reflection surface.