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:
Nov. 22, 1994
Filed:
Mar. 15, 1993
Kenzo Sado, Saitama, JP;
Fuji Photo Optical Co., Ltd., Saitama, JP;
Abstract
First, second, third, and fourth set lenses are located in this order from the direction of a screen. The first lens group comprises a plastic lens having a weak refracting power and at least one aspherical surface. The second lens group comprises a plastic lens having a weak refracting power and at least one aspherical surface, and an achromatic lens system having a substantial effect on the refracting power of the whole projecting lens. The achromatic lens system is composed of three or four glass lenses, and a plastic lens having a positive refracting power and at least one aspherical surface. The third lens group comprises a plastic lens having a weak refracting power and at least one aspherical surface. The fourth lens group comprises a plastic lens having at least one aspherical surface, and a field flattener lens, which is located with its concave surface facing the screen and which constitutes a liquid optical coupler. Special conditions are satisfied such that an unsharp state of a projected image due to an increase in temperature may be compensated for, and a wide variable power range may be obtained.