Patent ID: 8270096

Claim:
An image lens system, in order from an object side to an image side thereof, comprising: a first lens group with negative refraction power, wherein the first lens group comprises a first lens with negative refraction power and a second lens with positive refraction power; a second lens group with positive refraction power wherein the second lens group comprises a third lens with positive refraction power and a fourth lens with positive refraction power; and a third lens group with positive refraction power, wherein the third lens group comprises a fifth lens with positive refraction power; wherein the first lens group and the third lens group are positioned immovably along the optical axis of the image lens system, the second lens group is positioned movably along the optical axis of the image lens system; the image lens system satisfies the following formulas: 2.1≦ Lw/ ( a*Y )<2.5; 1.9 ≦|Fp 1 /F 1|≦2.2; and 0.6 ≦|Fp 2 /F 2|≦0.7, where “Lw” represents the overall length of the image lens system when the image lens system is in the wide angle state, “a” represents the zoom ratio of the image lens system which is the ratio of the effective focal length of the image lens system in the telephoto state to that is in the wide angle state, “Y” represents the maximum height of image that the image lens system generates, “Fp 1 ” represents the effective focal length of the second lens, “F 1 ” represents the effective focal length of the first lens group, “Fp 2 ” represents the effective focal length of the fourth lens, “F 2 ” represents the effective focal length of the second lens group.