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. 23, 1990
Filed:
Dec. 06, 1988
Masatake Kato, Tokyo, JP;
Canon Kabushiki Kaishi, Tokyo, JP;
Abstract
A secondary image forming type finder opitcal device having an objective lens solely used therefor, comprising, from front to rear, an objective lens unit including at least one positive lens, a relay lens unit formed by arranging a lens of positive refractive power and a lens of negative refractive power in spaced relation, a field lens unit consisting of a positive lens whose front surface is of strong curvature, and an eyepiece lens unit consisting of two positive lenses whose confronting surfaces are of strong curvature, satisfying the following conditions: ##EQU1## where f.sub.P is the focal length of the lens of positive refractive power of the relay lens unit, .nu..sub.P is the Abbe number of its material, R.sub.P is the radius of curvature of a lens surface of the lens of positive refractive power of the relay lens unit which is of strong curvature and faces the lens of negative refractive power of the relays lens unit, f.sub.N is the focal length of the lens of negative refractive power of the relay lens unit, .nu..sub.N is the Abbe number of its material, and R.sub.N is the radius of curvature of a lens surfaces of the lens of negative refractive power of the relay lens unit which is of strong curvature and faces the lens of positive refractive power of the relay lens unit.