Patent ID: 9625733
Date: 2017-04-18
CPC Classifications: G02B

Claim:
1. A zoom optical system comprising, in order from an object: a first lens group having positive refractive power; a second lens group having negative refractive power; a third lens group having positive refractive power; and a fourth lens group having negative refractive power, upon zooming, distance between the first lens group and the second lens group varies, distance between the second lens group and the third lens group varies, and distance between the third lens group and the fourth lens group varies, the third lens group or the fourth lens group including at least one contact multi-layer type diffractive optical element, and the following conditional expressions are satisfied: where φi denotes a total refractive power of the lens group including the contact multi-layer type diffractive optical element, and φdoei denotes a refractive power of the contact multi-layer type diffractive optical element, and where TLw denotes a distance from a lens surface closest to an object to an image plane in a wide-angle end state, and fw denotes a focal length of the zoom optical system in the wide-angle end state.