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:
Apr. 18, 2000
Filed:
Oct. 21, 1997
Hiroyasu Ozaki, Tokyo, JP;
Asahi Kogaku Kogyo Kabushiki Kaisha, Tokyo, JP;
Abstract
A telephoto zoom lens includes a first positive lens group, a second negative lens group, a third positive lens group and a fourth lens group. A resultant refractive power of the third and fourth lens groups are moved from an image side to an object side upon zooming from a short focal length extremity to a long focal length extremity, so that a distance between the first and second lens groups increases, a distance between the second and third lens groups decreases, and a distance between the third and fourth lens groups becomes smallest at an intermediate focal length. The zoom lens satisfies a condition specified by (0.1<X.sub.3 /X.sub.1 <0.5), wherein X.sub.1 represents a distance between a position at the short focal length extremity and at the long focal length extremity of the first lens group on an optical axis, and X.sub.3 represents a distance between the positions at the short focal length extremity and at the long focal length extremity of the third lens group on the optical axis, respectively.