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. 28, 2001
Filed:
Oct. 13, 1999
Yasuyuki Tomita, Utsunomiya, JP;
Canon Kabushiki Kaisha, Tokyo, JP;
Abstract
A zoom lens includes a first lens unit having a positive refracting power and is fixed during zooming, a second lens unit having a negative refracting power and is movable during zooming, a third lens unit having a positive refracting power and used to correct the image surface by the zooming, and a fourth lens unit having a positive refracting power. These lens units are arranged in the order named from the object side. In order to properly correct halo/coma that tends to occur during zooming, an aspherical surface is formed in the third lens unit at a focal length fm given by fm=fw·z,, where fw is the wide-angle focal length, and z is the zoom ratio, when the imaging magnifications of the second and third lens units simultaneously pass through −1-time point during zooming.
Data source: USPTO (United States Patent and Trademark Office) public patent records. Weekly synchronization. How IDiyas builds this profile