| 摘要 |
<p>A zoom lens comprising a first lens group having a positive refracting power, a second lens group having a negative refracting power, a third lens group having a positive refracting power, and a fourth lens group having a positive refracting power arranged sequentially from the object side, wherein the first and third lens groups are fixed, the second lens group is moved in the direction of the optical axis principally for the purpose of varying magnification and the fourth lens group is moved in the direction of the optical axis for the purpose of correcting variation in the image position and focusing, characterized in that the first lens group consists of five lenses arranged sequentially from the object side, i.e. a concave lens, a convex lens directing the strong convex face toward the image side, a cemented lens of a concave lens directing the strong concave face toward the image side and a convex lens, and a convex lens directing the strong convex face toward the image side, and satisfies following conditional expressions; (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.</p> |
