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:
Jan. 23, 2001
Filed:
Jan. 08, 1999
Hitoshi Mukaiya, Yokohama, JP;
Akihisa Horiuchi, Yokohama, JP;
Canon Kabushiki Kaisha, Tokyo, JP;
Abstract
A zoom lens of the rear focus type is disclosed, whose back focal distance is increased to accommodate a three-color separation prism and other optical elements, comprising, in order from an object side to an image side, a first lens unit of positive refractive power, a second lens unit of negative refractive power, a third lens unit of positive refractive power and a fourth lens unit of positive refractive power, the second lens unit and the fourth lens unit being moved to effect zooming and the fourth lens unit being moved to effect focusing, wherein the third lens unit has a negative lens disposed closest to the object side and having a concave surface facing the object side and has a positive lens disposed closest to the image side, and a lens surface on the image side of the positive lens has a refractive power which is stronger than that of a lens surface on the object side of the positive lens.