Patent ID: 6233101
Filing Date: 2001-05-15
Classification: G02B

Abstract:
A modified Gaussian lens comprising, successively from an object side, meniscus first and second lenses each having a positive refracting power with a convex surface directed onto the object side, a meniscus third lens having a negative refracting power with a concave surface directed onto an image side, a meniscus fourth lens having a negative refracting power with a concave surface directed onto the object side, and a fifth lens made of a biconvex lens, said Gaussian lens satisfying the following conditional expression (1):0.37<f.sub.1,2 /f<0.57 (1)wheref is the focal length of the whole system;f.sub.1,2 is the composite focal length of the first and second lenses;further satisfying the following conditional expressions (4) to (6):22.0<.nu..sub.2 -.nu..sub.3 <36.0 (4)6.0<(1/R.sub.6 +1/.vertline.R.sub.7.vertline.).times.f<11.2 (5)-1.72<R.sub.10 /R.sub.11 <0 (6)where.nu..sub.1 is the Abbe number of the i-th lens; andR.sub.i is the radius of curvature of the i-th surface (only lens surface).