| 摘要 |
A compact zoom lens comprising, from front to rear, a positive 1st group movable for focusing consisting of a positive doublet of negative and positive lenses and a positive singlet, a negative 2nd group movable for variation of magnification consisting of a negative singlet and a negative doublet of negative and positive lenses, a positive 3rd group movable for image shift compensation simultaneously with the second group consisting of a positive doublet of positive and negative lenses, and a relay lens of positive power consisting of 4th and 5th groups, the fourth consisting of at least one positive lens of forward convexity and a negative lens, and the fifth consisting of a negative meniscus lens of rearward convexity and a positive lens, the zoom lens satisfying the following conditions: 0.7< phi 4,5/ phi 4<0.85 (1) 1.5< phi 4s/ phi 4,5<2.2 (2) N4n>N4p (3) 1.76<N5n<1.85 (4) 30< nu 5p<45 (5) where phi 4,5 is the overall refractive power of the 4th and 5th groups; phi 4 is refractive power of the 4th group; phi 4s the refractive power of the first surface of the positive lens in the 4th group; N4p the refractive index of the positive lens or lenses in the 4th group; N4n the refractive index of the negative lens in the 4th group; N5n the refractive index of the negative lens in the 5th group; and nu 5p the Abbe number of the positive lens in the 5th group.
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