Patent ID: 6335835
Filing Date: 2002-01-01
Classification: G02B

Abstract:
A taking lens for a photographic device comprising, in order from the object side, a first lens group which consists of a positive power first meniscus lens element convex to the object side, a fixed aperture and a second lens group which consists of a positive power second meniscus lens element concave to the object side,wherein said positive power first meniscus lens element at an image side surface and said positive power second meniscus lens element at one of image and object side surfaces are defined by the following relationship: Z=Ch2/[1+{square root over (1âˆ’+L (1+K+L )Ch2+L )}]+X1h4+X2h6+X3h8+X4h10 where Z is the surface sag at semi-aperture distance h from the axis of the lens, C is the curvature of a lens surface at the optical axis equal to the reciprocal of the radius at the optical axis, K is a conic constant, and X1, X2, X3 and X4 are aspheric constants, andwherein said positive power first and second meniscus lens elements satisfy the following conditions: |f1|>f2R1>R2where f1 is the focal length of the positive power first meniscus lens element, f2 is the focal length of the positive power second meniscus lens element, R1 and R2 are the radii of curvature of the object side and image side surfaces of the positive power first meniscus lens element, respectively.