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:
Sep. 30, 1997
Filed:
Apr. 29, 1996
Fumio Koyama, Suwa, JP;
Masatoshi Yonekubo, Suwa, JP;
Takashi Takeda, Suwa, JP;
Toshio Arimura, Suwa, JP;
Hidefumi Sakata, Suwa, JP;
Osamu Yokoyama, Suwa, JP;
Seiko Epson Corporation, Tokyo, JP;
Abstract
The focus detection mechanism of the invention diffracts the return light reflected off target surface by means of holographic element. The diffracted beams are both received by two long photodetection means as two astigmatic convergent beams that forms circles of least confusion on the same plane near focal plane of a lens. The focus detection signal is obtained from differential output of them. Since the mechanism can form two diffracted beams having circles of least confusion on the same plane, the photodetection means for detection can be disposed side by side, thus simplifying production with increased dimensional accuracy. Also, although a holographic element is used, wavelength fluctuation can be absorbed to provide extremely high reliability.