Patent ID: 8385001

Claim:
A zoom projection lens system, in order from the magnification side to the minification side thereof, comprising: a first lens group with negative refraction power, the first lens group comprising a first aspherical plastic lens; a second lens group with positive refraction power, the second lens group comprising a second aspherical plastic lens; a third lens group with positive refraction power; a fourth lens group with negative refraction power, the fourth lens group comprising a third aspherical plastic lens; and a fifth lens group with positive refraction power; the first lens group, the second lens group, the third lens group, and the fourth lens group being movably positioned, the fifth lens group being immovably positioned, the zoom projection lens system satisfying the formula: −2.4 ≦F a1 /F w ≦−2.1 2.9 ≦F b1 /F w ≦3.2 −3.8 ≦F a2 /F w ≦−3.6 wherein F a1 , F a2 , F b1 are the effective focal lengths of the first, second, third aspherical plastic lenses respectively, F w is the effective focal lengths of the zoom projection lens system in a wide angle state.