Patent ID: 6320704
Filing Date: 2001-11-20
Classification: G02B

Abstract:
An imaging lens comprising, successively from an object side, a positive first lens having a convex surface directed onto the object side, a negative second lens having a concave surface directed onto an image side, a third lens made of a positive meniscus lens having a convex surface directed onto the object side, a fourth lens made of a positive meniscus lens having a convex surface directed onto the image side, a negative fifth lens having a concave surface directed onto the object side, and a positive sixth lens having a convex surface directed onto the image side, said first and second lenses being cemented to each other, said second and fifth lenses satisfying the following conditional expression (4):.theta..sub.g,F +0.0019v.sub.d <0.650 (4)where.theta..sub.g,F is a partial dispersion ratio of a lens material expressed by:.theta..sub.g,F =(N.sub.g -N.sub.F)/(N.sub.F -N.sub.C)v.sub.d is an Abbe number of the lens material expressed by:v.sub.d =(N.sub.d -1)/(N.sub.F -N.sub.C)whereN.sub.g is the refractive index of the lens material at a wavelength of 435.8 nm;N.sub.F is the refractive index of the lens material at a wavelength of 486.1 nm;N.sub.C is the refractive index of the lens material at a wavelength of 656.3 nm; andN.sub.d is the refractive index of the lens material at a wavelength of 587.6 nm.