Patent ID: 8228611

Claim:
A lens module having a magnified side and a reduced side opposite to the magnified side, the reduced side having an imaging surface, the lens module comprising: a first lens group, having a positive refractive power and comprising a first lens having a negative refractive power and a second lens having a positive refractive power, wherein the first lens is near the magnified side, a distance between a center of a surface of the first lens facing the magnified side and the imaging surface is D, an effective focal length of the lens module is F, and 1≦D/F≦3; a second lens group having a positive refractive power and located between the first lens group and the reduced side, wherein the second lens group comprises a third lens having a positive refractive power and a fourth lens having a negative refractive power and the third lens is located between the second lens and the fourth lens; and a third lens group having a positive refractive power and located between the second lens group and the reduced side, wherein the third lens group comprises a fifth lens having a positive refractive power.