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:
Mar. 15, 2011
Filed:
May. 18, 2009
Masakazu Kodaira, Utsunomiya, JP;
Tsuyoshi Wakazono, Utsunomiya, JP;
Masaru Sakamoto, Utsunomiya, JP;
Ryuji Nurishi, Utsunomiya, JP;
Masakazu Kodaira, Utsunomiya, JP;
Tsuyoshi Wakazono, Utsunomiya, JP;
Masaru Sakamoto, Utsunomiya, JP;
Ryuji Nurishi, Utsunomiya, JP;
Canon Kabushiki Kaisha, Tokyo, JP;
Abstract
A zoom lens system includes, in order from the object side to the image side, four lens units having positive, negative, negative and positive refractive powers. A first lens unit includes, in order from the object side to the image side: a front subunit having a negative refractive power; a middle subunit that has a positive refractive power and moves during focusing; and a rear subunit having a positive refractive power. The zoom lens system further includes a variable apex angle prism disposed on the image side of the front subunit. An average Abbe number of materials of a negative lens element and a positive lens element included in the front subunit is set appropriately so as to suppress occurrence of decentering aberration accompanying a variation of a prism apex angle.