| 摘要 |
PROBLEM TO BE SOLVED: To provide a zoom lens which secures brightness and has suppressed variation in astigmatism, regardless of a simple configuration and is easy to secure a viewing angle and a variable power ratio at the wide angle end, even when the brightness is secured. SOLUTION: The zoom lens is composed of a first positive group G1, a second negative group G2 and a third positive group G3 and has a diaphragm S between the second group G2 and the third group G3. In the zoom lens, when power is varied from the wide angle end to the telephoto end, the first group G1, the second group G2 and the third group G3 are moved, the second group G2 is moved to an image side and then, to an object side, and the first group G1 and the third group G3 are placed on the object side at the telephoto end, with respect to the wide angle end. The first group G1 is composed of one negative lens and one or two positive lenses. The second group G2 is composed of a first negative meniscus lens whose convex surface faces the object side, a second negative lens having the absolute value of the curvature of an image-side surface larger than that of an object-side surface and a third positive lens having the absolute value of the curvature of the object-side surface larger than that of the image-side surface. When focusing from a far distance to a near distance is performed, the second group G2 is moved. COPYRIGHT: (C)2008,JPO&INPIT
|
