Patent ID: 8456759

Claim:
A lens system for imaging an object on an image plane, the lens system comprising, in this order from the object side to the image side thereof: a first lens of positive refractive power; a second lens of negative refractive power; a third lens of positive refractive power; a fourth lens of positive refractive power, the fourth lens comprising an object-side surface facing the object side and an image-side surface facing the image side; and a fifth lens of negative refractive power; wherein the lens system satisfies the following condition formulas: D/TTL> 1.05; (1) Z/Y> 0; (2) G 3 R 1/ F 3> G 1 R 1/ F 1>0; (3) G 1 R 2/ F 1< G 3 R 2/ F 3<0; (4) and G 5 R 1/ F 5< G 5 R 2/ F 5<0, (5) where D is the diameter of optical images formed by the lens system on the image plane, TTL is the total length of the lens system, Z is the distance between an outer periphery of the image-side surface to the center of the object-side surface along a direction parallel to an optical axis of the lens system, Y is the distance between the outer periphery of the image-side surface to the center of the object-side along another direction perpendicular to the optical axis of the lens system, G3R1, G1R1, G2R2, G3R2, G5R1 G5R2 are the radii of curvature of an object-side surface of the third lens, an object-side surface of the first lens, an image-side surface of the second lens, an image-side surface of the third lens, an object-side surface of the fifth lens, and an image-side surface of the fifth lens, respectively, and F1, F3, F5 are focal lengths of the first, third, and fifth lenses, respectively.