TW200734801A - Zoom lens - Google Patents

Abstract

A zoom lens which from the object side is comprised with a negative refraction first group and a positive refraction second group orderly in turns. The refraction forces of the first and the second groups are 1/f1, 1/f2. When the distance between the first and the second groups becomes bigger, the focal length of the optics is fw, on the contrary, when the distance between the first and the second groups becomes smaller, the focal length of the optics is fT. The present invention is fit in with 0.9≤ |f1| /(fW. fT)1/2 ≤1.1 and 1.15 ≤ |f1|/f2 ≤1.35. The first group including a negative and a positive convex-concave lens that the convex surfaces face the object side, and each lens at least has a non- spherical surface. The second group includes a first and a second accessorial groups that having a positive refraction, the first accessorial group having a double convex lens and a double concave lens, the second accessorial group having a positive convex-concave lens that the convex surface faces the object side. By such arrangement, the refraction forces of each group and the shaped of the lenses are applicable, thus ensuring well optical performance and providing a zoom lens of miniaturized size, high performance and low price.