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. 13, 1996
Filed:
Jun. 13, 1994
Jun Hirakawa, Tokyo, JP;
Asahi Kogaku Kogyo Kabushiki Kaisha, Tokyo, JP;
Abstract
A two-group zoom lens is provided which has a first lens group of negative power and a second lens group of positive power, located in this order from an object to be photographed. The first and second lens groups are moved relative to one another to provide various degrees of magnification. The first lens group includes a first lens of negative power, a second lens of negative power, and a third lens of positive power. The second lens group includes a fourth lens of positive power, a fifth lens of positive power, a sixth lens of negative power, and a seventh lens of positive power. The fifth lens is cemented to the sixth lens. The fifth and sixth lenses satisfy the following conditions: (a) 0.1<n.sub.N -n.sub.P <0.4; (b) -1.3<r.sub.c /f.sub.2 <-0.5; and (c) 0.6<d.sub.1-2 /f.sub.w <1.2; wherein, n.sub.P represents a refractive index of the fifth lens, n.sub.N represents a refractive index of the sixth lens, r.sub.c represents a radius of curvature of the cementing surface of the fifth and sixth lenses, f.sub.2 represents a focal length of the second lens group, d.sub.1-2 represents a distance between the first and second lens groups, and f.sub.w represents a focal length of the entire zoom lens at a wide angle extremity.