Patent ID: 8922907

Claim:
A variable focal length lens system comprising: a first lens group having positive power; a second lens group having negative power; a third lens group having positive power; and a fourth lens group having positive power sequentially arranged from a side where an object is present, wherein an aperture stop is disposed between the second lens group and the third lens group and moves integrally with the third lens group, the first lens group, the second lens group, the aperture stop, the third lens group and the fourth lens group are arranged in this order along an optical axis from an object side to an image side defining an image plane extending perpendicularly to the optical axis, the variable focal length lens system moves to and between a wide angle end state and a telescopic state, relative to the wide angle end state, in the telescopic end state, each one of the first lens group, the second lens group, the aperture stop, the third lens group and the fourth lens group is disposed away from the image plane while the first lens group and the second lens group are disposed further apart from one another, the second lens group and the third lens group are disposed closer to each other and the third lens group and the fourth lens group are disposed closer to each other, the third lens group includes a negative lens and a positive lens disposed on an image side thereof, and the variable focal length lens system satisfies the following conditional expression (1): 0.35 <f 3 /|f 3 a|< 0.8 (1) where f3a represents a focal length of the negative lens disposed in the third lens group, and f3 represents a focal length of the third lens group.