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:
Jul. 25, 1995
Filed:
Dec. 08, 1993
Osamu Yokoyama, Suwa, JP;
Masatoshi Yonekubo, Suwa, JP;
Hideaki Iwano, Suwa, JP;
Hidefumi Sakata, Suwa, JP;
Takashi Takeda, Suwa, JP;
Tetsuya Seki, Suwa, JP;
Shigeru Kogure, Suwa, JP;
Seiki Epson Corporation, Tokyo, JP;
Abstract
A small and inexpensive optical head for detecting a recorded signal, a focusing error signal and a tracking error signal, and an optical memory device utilizing the optical head. A diffraction device (103) is provided having two chirped grating regions (103A, 103B) for dividing a light beam from an optical recording medium (105) and directing the divided beams toward four band-shaped photoelectric transducers (106) and an astigmatism generator formed by the diffraction device (103) and a positive lens (102). The four photoelectric transducers are positioned in a plane inclined with respect to the optical axis of zero-order diffraction light, and the longitudinal axes of each of the band-shaped photoelectric transducers are radially arranged relative to the optical axis.