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:
May. 19, 1987
Filed:
Apr. 18, 1985
Norikazu Arai, Komae, JP;
Konishiroku Photo Industry Co., Ltd., Tokyo, JP;
Abstract
A projection lens in which F is approximately 1.0 to 1.3 used for a 3-tube television projector. The projection lens comprises a first lens of extremely low refractive power, two positive lenses arranged spaced apart from the first lens through a large air space and a negative fourth lens arranged spaced apart therefrom through a large air space, the first lens L.sub.1 having at least one surface in the form of an aspherical surface. It is possible to arrange a reflecting mirror in the large air space to thereby form an optical system into a compact form. In addition, if the second lens L.sub.2 and the third lens L.sub.3 are made of glass, even if the first lens L.sub.1 and the fourth lens L.sub.4 are formed into plastic lenses, movement of focal point due to variation in temperature hardly occurs, and a lens of low cost may be obtained.