| 摘要 |
PURPOSE:To make a zoom lens compact by arranging two lens groups, i.e. a 1st lens group which has positive refracting power and a 2nd lens group which has negative refracting power from an object side, and varying the lens gap between the both for zooming. CONSTITUTION:The 1st lens group A consists of a 1st element L1 which has its convex surface on the object side, a 2nd element L2 which is formed by cementing a biconcave lens to a biconvex and has its convex surface on the image side and negative composite power, and a 3rd element L3 which is a biconvex lens having a large-curvature surface on the object side in order from the object side, and the 2nd lens group B consists of a 4th element L4 which has a large-curvature surface on the image side, a 5th element L5 which is a biconcave lens having a large-curvature surface on the object side, and a 6th element L6 which is a negative meniscus lens having a large-curvature surface on the object side. Then inequalities I-III hold, where fW is the focal length of the whole system in wide-angle mode, f1 and f2 the focal lengths of the 1st and 2nd lens groups A and B, and f13 the focal length of the 3rd element L3. Consequently, the compact zoom lens is obtained.
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