| 摘要 |
PURPOSE:To obtain a small-sized zoom lens which has less aberration variation over the entire power variation range by moving two out of three lens groups, i.e. the 1st and the 2nd lens groups for power variation. CONSTITUTION:The 3rd lens group III is arranged behind the 2nd lens group II, the lens group I' composed of the 1st lens group I and the 2nd lens group II has positive refracting power, and telephoto type lens constitution is composed of the lens group I' and the 3rd lens group III. Then, specific conditions are satisfied as shown by phiw<phi1<1.5phiw (1), -1.5phiw<phi2<-0.5phiw (2), -0.6phiw <phi3<0.1phiw (3), 0.4/phiw<phi1w<0.8/phiw (4), where phi1,phi2 and phi3 are refractive index es of the 1st, the 2nd, and the 3rd lens groups, e1w is the principal-point gap between the 1st and the 2nd lens groups, and phiw is the refractive index of the whole system at a zoom position on a wide-angle end side. |
