Patent ID: 7924510
Filing Date: 2011-04-12
Classification: G02B

Abstract:
1. An imaging lens comprising: in order from an object side of the imaging lens, a first lens group including a biconcave lens; a second lens group including two lenses whose convex surfaces are arranged opposite to each other, the second lens group having a positive refractive power as a whole; a third lens group including a biconcave lens; and a fourth lens group including two lenses whose convex surfaces are arranged opposite to each other, the fourth lens group having positive refractive power, as a whole, the imaging lens satisfying conditional expressions (1) and (2): wherein BF represents a back focal length BF of the imaging lens, L represents a length L in a optical axial direction from a surface of the imaging lens nearest to an object to a surface of the imaging lens nearest to an image, and N 4 represents a refractive index of the third lens group at the d-line, wherein each of the convex surfaces of the fourth lens group has a radius of curvature whose absolute value is smaller than that of the other surface of each lens.