Patent ID: 8934176
Filing Date: 2015-01-13
Classification: G02B

Abstract:
1. A zoom optical system composed of a plurality of lens groups comprising: a first lens group that is a most object side lens group; and a second lens group that is a lens group having positive refractive power disposed to an image side of the most object side lens group; the second lens group including a focusing lens group that carries out focusing from an infinity object to a close object, and a decentering lens group that is movable in a direction having a component perpendicular to an optical axis; and upon zooming from a wide-angle end state to a telephoto end state, a distance between the first lens group and the second lens group varies and an interval in the optical-axis direction between the focusing lens group and the decentering lens group is fixed; wherein the first lens group has negative refractive power, upon said zooming the second lens group moves; and wherein the following conditional expression is satisfied: where βG2ft denotes an imaging magnification of the focusing lens group in a telephoto end state.