Patent ID: 8254041

Claim:
A lens system, in order from the object side to the image side, comprising a first lens with positive refractive power, a second lens with negative refractive power, a third lens with positive refractive power, a fourth lens with positive refractive power, and an aperture stop positioned between the third lens and the fourth lens; wherein, the second lens comprises a first optical portion, and a first support portion surrounding the first optical portion, the first support portion having a first surface and an opposite second surface facing the image side, and a flange protruding from the second surface and attached to the third lens; the third lens comprises a second optical portion and a second support portion surrounding the second optical portion; and the second support portion comprises a third surface and an opposite fourth surface facing the image side; the fourth lens comprises a surface facing the object side, and an annular shim mounted on the surface of the fourth lens; and the lens system satisfies the following formula: d 23 <1.1×d 34 , where d 23 is the distance along the optical axis of the lens system from the second surface of the second lens to the third surface of the third lens, and d 34 is the distance along the optical axis of the lens system from the fourth surface to the surface of the fourth lens.