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. 15, 2000
Filed:
Nov. 24, 1998
Kazuo Yoshikawa, Saitama, JP;
Fuji Photo Optical Co., Ltd., Saitama, JP;
Abstract
An extender lens group removably incorporated in a zoom lens equipped with a temperature compensating feature for increasing the prim-lens focal length to achieve increased magnification is comprised of a front extender lens sub-group including four lens elements and a rear extender lens sub-group including two lens elements, the front extender lens sub-group including two positive bi-convex lens elements each of which has a strong curvature at the subject side surface followed by an overall positive doublet comprising a positive bi-convex lens element with a strong curvature at the subject side surface and a negative bi-concave lens element with a strong curvature at the image side surface and the rear extender lens sub-group including an overall positive doublet comprising a bi-concave lens element with a strong curvature at the image side surface and a positive meniscus lens element with a concave surface on the subject side. The extender lens group satisfying the following conditions: ##EQU1## where P1 is the temperature coefficient of refraction index of the negative lens element in the front extender lens sub-group and P2 is the temperature coefficient of refraction index of the positive lens element in the rear extender lens sub-group, the P1 and P2 being defined by dn/dt relative (.times.10.sup.-6 /.degree.C.) for a wave length of e-line.