Patent ID: 6222680
Filing Date: 2001-04-24
Classification: G02B

Abstract:
A zoom lens for primary use with a projection screen television system, said zoom lens comprising, in sequential order from the enlarging side:a first lens group G.sub.1 of negative refractive power which is in a fixed position;a second lens group G.sub.2 that has positive refractive power;a third lens group G.sub.3 that has positive refractive power;a fourth lens group G.sub.4 that has negative refractive power; anda fifth lens group G.sub.5 that has positive refractive power and is fixed in positionwhereinthe axial positions of the second lens group, the third lens group, and the fourth lens group vary when zooming so as to provide a change in magnification and to correct for shifting of the image surface which otherwise would occur with zooming, andthe following conditions are satisfied:-0.9.ltoreq.f.sub.1 /F<-0.30.7<f.sub.2 /F<1.50.8<f.sub.5 /F<1.5wheref.sub.1 is the focal length of the first lens group,F is the focal length of the zoom lens at the wide-angle end,f.sub.2 is the focal length of the second lens group, andf.sub.5 is the focal length of the fifth lens group.