Patent ID: 8456760

Claim:
A lens system, in an order from the object side thereof to the image side thereof, comprising: an aperture stop; a first lens of positive refractive power having a first subject-side surface and a first image-side surface; a second lens of positive refractive power having a second subject-side surface and a second image-side surface; a third lens of negative refractive power having a third subject-side surface and a third image-side surface; and an image plane; the lens system satisfying the following formulae: FB/TTL>0.30; G 1 R 2 /F 1 >19.54; and D 1 /D 2 <1.62, wherein FB denotes a distance between a nearest point of the third image-side surface relative to the image plane and the image plane; TTL denotes the total track length of the lens system; G 1 R 2 denotes the curvature radius of the vertex of the first image-side surface; F 1 denotes the focal length of the first lens; D 1 denotes an orthogonal distance between a farthest point of the second image-side surface relative to an optical axis of the lens system and a central point of the second image-side surface on the optical axis of the lens system, measured along a direction substantially perpendicular to the optical axis of the lens system; D 2 denotes an orthogonal distance between the farthest point of the second image-side surface and the central point of the second image-side surface on the optical axis of the lens system, measured along a direction substantially parallel to the optical axis of the lens system; the lens system further satisfying the following formulae: −0.34>G 1 R 2 /F 2 >G 2 R 1 /F 2 >−0.68; −0.42>G 3 R 2 /F 3 >G 3 R 1 /F 3 >−1.92; wherein G 2 R 1 denotes the curvature radius of the vertex of the second subject-side surface, G 3 R 1 denotes the curvature radius of the vertex of the third subject-side surface, G 3 R 2 denotes the curvature radius of the vertex of the third image-side surface, F 2 denotes the focal length of the second lens, F 3 denotes the focal length of the third lens.