Zoom optical system

The invention provides a zoom optical system. A zoom optical system according to one embodiment of the present invention includes a first lens group, a second lens group, and a third lens group arranged in order from an object side toward an image side, in which the first lens group is composed of three fixed lenses, and the third lens group is composed of three fixed lenses. The three fixed lenses comprise a first lens with positive power, a second lens with positive power and a third lens with negative power; the second lens group is composed of two movable lenses, and the two movable lenses comprise a fourth lens with positive power and a fifth lens with negative power; the third lens group is composed of two movable lenses, and the two movable lenses comprise a sixth lens with negative power and a seventh lens with negative power; adjusting magnification according to movement of the second lens group; adjusting a focus according to the movement of the third lens group; and wherein the second lens group an