| 摘要 |
PROBLEM TO BE SOLVED: To obtain a zoom lens which is compact, but does not spoil optical performance by composing the lens of a 1st lens group which has positive refracting power meeting specific conditional expressions and a 2nd lens group which has negative refracting power. SOLUTION: The 1st lens group Gr1 with positive refracting power consists of a 1st lens L1-a 3rd lens L3 and the 2nd lens group Gr2 with negative refracting power consists of a 4th lens L4 and a 5th lens L5. The lens L1 which is on the most object side in the 1st lens group Gr1 meets the conditional inequalities. Namely, -0.6<ΦLp1/Φ1<-0.2, 0.2<ΦLp2/Φ1<0.6, -2.5<ΦLp1×fT<2>×(βT-βW)/FnT+ΦLp1×fT<2> /Fnt<2.5, whereΦLp1 andΦLp2 are the refracting powers of plastic lenses in the 1st and 2nd lens groups,Φ1 the refracting power of the 1st lens group, fT the focal length of the whole system at the telephoto end,βT andβW F the power of the 2nd lens group at the telephoto end and wide-angle end respectively, and FnT the F number at the telephoto end.
|
