Patent ID: 8238043

Claim:
An imaging lens system, comprising: three lens groups having four lenses including a first lens, a second lens, a third lens, and a fourth lens arranged in order from an object side; and an aperture stop arranged between the first lens and the second lens, wherein the second lens and the third lens are joined each other; the first lens is a negative meniscus lens having a convex surface at an object side; the second lens is a positive lens having a convex surface having a large curvature at an image side; the third lens is a negative lens having a concave surface having a large curvature at an object side; the fourth lens is a positive lens having a convex surface having a large curvature at an image side; the following conditions are satisfied: 1.4 <|f 1 /F|< 2.2 0.4 <|f 1 /f 23|<1.6 where F is a focal length of the entire imaging lens system, f1 is a focal length of the first lens, and f23 is a combined focal length of the second lens and the third lens which are joined each other; and the following condition is satisfied: 1.80<N1 where N1 is a refractive index of material of the first lens for a d line.