Patent ID: 7869134

Claim:
A zoom optical system including a first lens group having a negative optical power, a second lens group having a positive optical power, and a third lens group having a positive or negative optical power in this order from an object side, the zoom optical system being configured in such a manner that an interval between the first lens group and the second lens group is decreased in zooming from a wide angle end to a telephoto end, wherein a positive lens element in the third lens group or in a lens group closer to an image side than the third lens group satisfies the following conditional expression: vp<40 where vp is a minimum value of the Abbe number of the positive lens element; and the second lens group satisfies the following conditional expression: 0.7< f 2/ fw< 2.0 where f 2 is a composite focal length of the second lens group, and fw is a composite focal length of the entirety of the zoom optical system at the wide angle end.