Patent ID: 7817352
Filing Date: 2010-10-19
Classification: G02B

Abstract:
1. A zoom lens comprising, sequentially from an object side thereof, a first lens elements group having a negative refraction power as a whole, a second lens elements group having a positive refraction power as a whole, and a third lens element group having a negative refraction power as a whole, wherein the first lens elements group is made up by disposing three lens elements which include a first lens element which is a negative lens, a second lens element which is a positive lens, and a third lens element which is a negative lens, wherein the second lens elements group is made up by disposing four lens elements which include a fourth lens element which is a positive lens, a fifth lens element which is a positive lens, a sixth lens element which is a negative lens, and a seventh lens element which is a positive lens, and where the third lens element group is made up by disposing an eighth lens element which is a negative lens, wherein a variable power is realized by shifting positions of the first lens elements group and the second lens elements group in a direction of an optical axis thereof, or shifting, in addition to the first lens elements group and the second lens elements group, a position of the third lens element group, wherein a configuration of positive/negative powers of the individual lens elements of the whole lens system is made to be a configuration of negative, positive, negative, positive, positive, negative, positive, negative which is symmetrical with respect to a boundary between the fourth lens element and the fifth lens element, and wherein a distribution of volumes of powers of the constituent lens elements is also made to be substantially symmetrical in a similar manner.