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:
Aug. 03, 1993
Filed:
Dec. 06, 1991
Akira Nakamura, Tokyo, JP;
Yuichi Nakano, Kanagawa, JP;
Sony Corporation, , JP;
Abstract
A zoom lens is provided, in which a fixed first lens group having a positive refracting power, a second lens group having a negative refracting power and which realizes a variable magnification, a fixed third lens group having a positive refracting power and a fourth lens group having a positive refracting power which compensates fluctuation of an image surface caused by the variable magnification and which focuses an image are sequentially provided from an object side. In this zoom lens, the third lens group is composed of two separate lenses of a positive lens (31) and a negative lens (32). At least one surface of the positive lens (31) is formed as an aspherical surface and a surface of the negative lens (32) opposing the image surface side is concaved to the image surface side. Thus, the zoom lens of this invention can be miniaturized and reduced in weight without deteriorating the characteristics such that a variable magnification is large and that an F number is small.