Optical: systems and elements – Lens – Multiple component lenses
Patent
1996-05-20
1998-12-01
Font, Frank G.
Optical: systems and elements
Lens
Multiple component lenses
G02B 934
Patent
active
058447296
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.
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Font Frank G.
Nikon Corporation
Stafira Michael P.
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