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. 03, 1989
Filed:
Mar. 30, 1988
Hideki Ogawa, Tokyo, JP;
Takashi Matsushita, Kanagawa, JP;
Canon Kabushiki Kaisha, Tokyo, JP;
Abstract
A photographic lens comprising, from front to rear, a first lens unit of positive power, a stop, a second lens unit of positive power, a third lens unit of negative power and a fourth lens unit of positive power. The first lens unit has at least one negative lens having a strong concave surface facing the stop, and the second lens unit has at least one negative lens having a strong concave surface facing the stop. When focusing is performed from an infinitely distant object to a close object, the first and second lens units are moved forward in unison, while the third lens unit is moved by a less amount than the amount of movement of the first and second lens units, whereby closeup optical performance is improved.