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. 16, 1991
Filed:
Apr. 23, 1990
Yoshinari Hamanishi, Wako, JP;
Nikon Corporation, Tokyo, JP;
Abstract
A lens system enabling close distance photographing has an excellent image forming performance for a wide focussing range from infinite distance to equi-magnification distance while employing a relatively simple lens composition. The lens system has a basic composition including a 1st group of positive refractive power, a 2nd group of positive refractive power and a 3rd group of negative refractive power arranged in this order from the object side and in focussing from infinite distance to closest distance, the 1st group and the 2nd group move to the object side away from the 3rd group, which is fixed relative to the image plane, while expanding the space between the 1st and the 2nd groups, the 3rd negative group has a positive lens and a negative lens arranged in this order from the object side.