Patent ID: 7382546

Claim:
A zoom optical system comprising: a first reflecting prism configured to bend an incident ray at about 90 degrees by reflection, and having an incident surface disposed on a subject side of an optical path and an exit surface disposed on an object side of said optical path; a second reflecting prism configured to bend an incident ray at about 90 degrees by reflection, and having an incident surface disposed on the subject side of an optical path and an exit surface disposed on the object side of said optical path, and at least one lens group including one or more lens elements arranged between the exit surface of the first reflecting prism and the incident surface of the second reflecting prism, the incident surface of the first reflecting prism, and the exit surface of the second reflecting prism being aligned substantially parallel to each other, the incident surface or the exit surface of the first reflecting prism having an optical power, and, if the incident surface of the first reflecting prism has an optical power, the incident surface of the second reflecting prism has an optical power or, if the exit surface of the first reflecting prism has an optical power, the exit surface of the second reflecting prism has an optical power, wherein the reflecting surface of the reflecting prisms are flat, an optical axis of the lens group and an axis of the optical path between the first and second reflecting prisms being coincident with each other, the lens group being movable along the optical axis thereof for zooming.