A zoom optical system includes at least two optical-element groups and a variable
optical-property optical element. The two optical-element groups are movable in
a magnification change and have a magnification varying function or a compensating
function for compensating for a shift of an image surface caused by the magnification
change. The optical element has a focusing function and is disposed on the image
side of the optical-element groups. According to this configuration of the zoom
optical system, it is possible to attain a zoom optical system and an imaging apparatus
using the zoom optical system that have as small a number of movable lenses as
possible, are very small in size, and work with an extremely low power consumption
and low operation noise.
