Patent ID: 8213091

Claim:
A wide-angle projection zoom lens comprising: a first lens group having a negative refractive power; a second lens group having a positive refractive power; a third lens group having a negative refractive power; a fourth lens group having a positive refractive power; and a fifth lens group having a positive refractive power, wherein the first to fifth lens groups are arranged in this order from a magnification side and a reduction side has telecentricity, during zooming from a wide angle end to a telephoto end, said first lens group and said fifth lens group are fixed, and said second lens group, said third lens group, and said fourth lens group are moved to the magnification side on an optical axis while changing gaps therebetween, said first lens group includes a first negative lens, a second negative lens, a third negative lens, and a fourth positive lens which are arranged in this order from the magnification side, said first lens is an aspheric lens made of plastic, and the wide-angle projection zoom lens satisfies the following conditional expressions: 1.6 <Bf/f W <2.6; 1.5 <|f 1 /f W |<4.5; 0.35 <D 2 /f W ; and 2.0 <L S /f W <3.0 where Bf indicates a back focal length, f W indicates the focal length of the entire system at the wide angle end, f 1 indicates the focal length of said first lens group, D 2 indicates the distance between a reduction-side surface of said first lens and a magnification-side surface of said second lens on the optical axis in said first lens group, and L S indicates the distance from a magnification-side surface of said first lens to a magnification side pupil position at the wide angle end.