Patent ID: 8159759

Claim:
A zoom lens comprising: a first lens group having a positive refractive power; a second lens group having a negative refractive power; a third lens group having a positive refractive power; and a fourth lens group having a positive refractive power, wherein the first lens group, the second lens group, the third lens group, and the fourth lens group are arranged sequentially from an object side, wherein the second lens group comprises a first aspherical lens having a negative refractive power, and a second aspherical lens having a positive refractive power, and satisfies the inequalities 1.4≦ w fno≦2.5 2≦ tf/wf≦ 5, where wfno is the minimum F-number (FNO) at the wide-angle position, tf is the focal length of the zoom lens at the telephoto position, and wf is the focal length of the zoom lens at the wide-angle position.