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:
Oct. 12, 1993
Filed:
Nov. 12, 1992
Kenzaburo Suzuki, Tokyo, JP;
Yoshinari Hamanishi, Wako, JP;
Nikon Corporation, Tokyo, JP;
Abstract
The rear conversion lens of the present invention is compact and maintains an excellent imaging performance even when it is mounted on a telephoto objective lens the enlargement magnification of whose focal length is relatively high, e.g. about double and whose F-number is of the order of 2-2.8, and moreover does not intercept a light beam even in the fully open state of the aperture. The rear conversion lens of the present invention is an RCL adapted to be mounted on the image side of an objective lens and having negative refractive power for enlarging the combined focal length of itself and the objective lens, and has, in succession from the objective lens side, a first lens unit of positive or negative refractive power, a second lens unit of negative refractive power and a third lens unit of positive refractive power, the first lens unit having a positive lens most adjacent to the object side, and when the air gap between the first lens unit and the second lens unit is D.sub.1 and the air gap between the second lens unit and the third lens unit is D.sub.2 and the on-axis lens thickness from the first surface to the last surface of the RCL is .SIGMA.d and the focal length of the entire RCL system is f.sub.R, the RCL satisfies the following conditions: