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:
Dec. 01, 1998
Filed:
May. 20, 1996
Yoshiyuki Shimizu, Kanagawa-ken, JP;
Nikon Corporation, Tokyo, JP;
Abstract
A small, light weight wide angle photographic lens has attachment size of less than approximately 3.5 times the focal length and has a field angle of approximately 100.degree.. The wide angle photographic lens includes a first lens L.sub.1 having a negative refractive power and a concave surface facing the image side; a second lens L.sub.2 with a positive refractive power having the convex surface facing the object side; a third lens L.sub.3 having a negative refractive power cemented to the second lens L.sub.2 and having a surface with a larger absolute value of index of refraction on the image side; a fourth lens L.sub.4 having a positive refractive power cemented to the third lens L.sub.3 and having a surface with a larger index of refraction on the object side; and a plurality of lenses on the image side of the fourth lens L.sub.4, wherein the concave surface of the first lens L.sub.1 is an aspherical surface with a conical constant .kappa. greater than 0.3 and less than 0.3 with a curvature of the concave surface decreasing monotonically with increasing distance from the optical axis. The wide angle photographic lens also satisfies conditions 0<n.sub.4 -n.sub.3 <0.15 and 0.2<r.sub.5 /f<0.7 where n.sub.3 and n.sub.4 denote the index of refraction of the third lens L.sub.3 and the fourth lens L.sub.4, respectively, r.sub.5 denotes the radius of curvature of the boundary surface between both lenses L.sub.3 and L.sub.4, and f denotes the focal length of the total lens system.