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. 21, 1993
Filed:
Sep. 13, 1991
Koji Hirata, Kamakura, JP;
Hiroki Yoshikawa, Hiratsuka, JP;
Tooru Numata, Chigasaki, JP;
Kiyoshi Wada, Yokohama, JP;
Masayuki Muranaka, Yokohama, JP;
Isao Yoshizaki, Yokohama, JP;
Takahiko Yoshida, Miura, JP;
Shigeru Inaoka, Yokohama, JP;
Hitachi, Ltd., Tokyo, JP;
Abstract
In a projection lens device having at least two plastic lenses for magnification-projecting an original image displayed on a display screen onto a screen, one of the two plastic lens is convex at a center thereof toward the screen and concave at a periphery thereof, and the other lens has a weak positive refractive power toward the screen at a center thereof and a stronger positive refractive power at a periphery thereof. A variation of a lens power due to a change of a surrounding environment is cancelled out by the concave shape at the periphery of the one lens and the positive refractive power at the periphery of the other lens.