Patent ID: 7929222
Filing Date: 2011-04-19
Classification: G02B

Abstract:
1. A zoom lens system, comprising, in order from an object side to an image side: a first lens unit that does not move for zooming and has a positive optical power; a second lens unit that moves during the zooming and has a negative optical power; a third lens unit that moves during the zooming and has a negative optical power; and a fourth lens unit that does not move for the zooming and has a positive optical power, wherein the first lens unit comprises a variable apex angle prism disposed on the image side of at least one lens element; and wherein the following conditions are satisfied: where fw denotes a focal length of an entire system at a wide angle end, f 1 denotes a focal length of the first lens unit, βvw denotes an imaging magnification of the second lens unit at the wide angle end, and βr denotes an imaging magnification of the fourth lens unit.