| 摘要 |
PROBLEM TO BE SOLVED: To provide an imaging unit realizing miniaturization while securing a necessary zoom ratio. SOLUTION: In the zoom lens, a 1st lens group is constituted of five lenses, that is, a concave lens L1, a convex lens L2 turning its strong convex surface toward an image side, a doublet consisting of a concave lens L3 turning its strong concave surface toward the image side and a convex lens L4, and a convex lens L5 turning its strong convex surface toward an object side, which are arranged in this order from the object side, and satisfies the following conditional expressions. The expressions are (1) 1.25<h1-1/h1-4<1.55, (2) d1-2/d1-3<0.4, (3) 1.65<n1-2 and (4) 0.1<H1'/f1<0.6, where f1: the focal distance of the 1st lens group, h1-i: the height of a paraxial ray on the i-th surface from the object side at the time of making the paraxial ray parallel with an optical axis on the 1st lens group, d1-i: axial space to the (i+1)th surface from the i-th surface of the 1st lens group, n1-i: the refractive index of the i-th lens of the 1st lens group on the d-line, and H1': space to the principal point on the image side of the 1st lens group from the apex of the surface nearest to the image side of the 1st lens group (- means the object side and + means the image side). COPYRIGHT: (C)2004,JPO&NCIPI
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