| 摘要 |
PURPOSE:To obtain a short zoom lens consisting of a small number of lens elements by arranging lens groups which have a focusing function, a power varying function, an image plane position correcting function, and a function for converging divergent luminous flux in order from the object side, arranging a stop between 5th and 4th groups and thus obtaining specific five-group constitution. CONSTITUTION:A 1st group is a positive lens group which has the focusing function, a 2nd group a negative lens group which moves and has the power varying function, a 3rd group a negative lens group which corrects an image plane position associatively with the 2nd group, and the 4th group a fixed positive lens group for convergence. The 5th group is arranged across the stop. The front group of the 5th group is formed of a positive lens which has its large-refractive-index surface on the object side and a negative meniscus lens, and the rear group is formed of a positive and a negative meniscus lens which have large-refractive-index surfaces on the image side and a positive lens, thereby correcting spherical aberrations and coma aberrations generated by the 1st-4th groups. This constitution provides the zoom lens whose overall length is short while respective aberrations are compensated excellently over the entire zoom range although the number of lens elements is small.
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