Patent ID: 8199414
Filing Date: 2012-06-12
Classification: G02B

Abstract:
1. A variable power zoom lens that has the foremost or first lens group of positive refractivity, the second lens group of negative refractivity, the third lens group of positive refractivity, and the fourth lens group of positive refractivity disposed in sequence from a position closer to the object to photograph toward the image plane, and it meets requirements as defined in conditional formulae as follows: where Lw is the distance from the front surface of the foremost lens piece to the image plane) at the wide-angle end, Ft is a focal length of the lens optics in whole at the telephoto end, and Fw is the focal length of the lens optics in whole at the wide-angle end, and where F_Bw is a focal length from the front surface of the foremost lens piece the closest to the object in the second lens group to the image plane at the wide-angle end, and F_Bt is the focal length from the front surface of the foremost lens piece in the second lens group to the image plane at the telephoto end.