Patent ID: 7619835

Claim:
An image-forming lens set comprising a first lens with positive power, a second lens with negative power, an aperture stop, and a third lens with positive power, which are arranged along an optical axis from an object side toward an image side in order; wherein the first lens has two opposite surfaces including a concave surface facing the object side and a convex surface facing the image side, and at least one of the two opposite surfaces is a non-spherical surface; wherein the second lens is a convex-concave lens having two non-spherical opposite surfaces including a concave surface facing the image side; wherein the third lens has two non-spherical opposite convex surfaces facing the object side and image side respectively; wherein at least one of the first, second and third lenses is coated with a layer of optical film for filtering light; wherein Equation 1 is satisfied as follows: D 1 /D 2>2.3 [Equation 1] in which: D 1 is the diameter of the first lens; and D 2 is the diameter of the second lens; wherein Equation 3 is satisfied as follows: | F 2/ F 1|<| F 3|< F [Equation 3] in which: F 1 is the effective focal length of the first lens; F 2 is the effective focal length of the second lens; F 3 is the effective focal length of the third lens; and F is the effective focal length of the whole image-forming lens set; and Equation 5 is satisfied as follows: V 2>50 [Equation 5] in which V 2 is the dispersion coefficient of the second lens.