Patent ID: 7193786

Claim:
A zoom optical system for forming an optical image of an object on an image-sensing surface of an image pickup element, said zoom optical system comprising, in order from an object side thereof: a first lens group having a negative refractive power; a second lens group having a positive refractive power; a third lens group having a negative refractive power; and a fourth lens group having a positive refractive power, wherein the zoom optical system moves at least the second lens group and the third lens group for zooming operation from a wide-angle end to a telephoto end so as to reduce a distance between the first lens group and the second lens group and increase a distance between the third lens group and the fourth lens group, wherein the zoom optical system moves the third lens group for a focusing operation, wherein the first lens group comprises, in order from the object side of the zoom optical system, a meniscus lens having a negative refractive power whose concave surface faces an image side of the zoom optical system, a reflective optical element, and at least one lens.