Imaging optical system

An imaging optical system comprising:

• a front lens group including at least one front lens element, and a reflector element which reflects a light bundle that exits from said front lens element, in that order from the object side;
• and
• a rear lens group provided on the image side of said front lens group,
• wherein said front lens element serves as a spherically-swingable lens group which, in an image-stabilizing operation, suppresses image shake on the imaging plane by spherically-swinging said spherically-swingable lens group about a predetermined spherical-swing center in accordance with vibrations applied to said imaging optical system, and
• wherein the following conditions (1) and (2) are satisfied:
• νd>58 (1),
• and
• f/y>3 (2),
• wherein
• νd designates the Abbe number with respect to the d-line of at least one lens element of said spherically-swingable lens group;
• f designates the focal length of said imaging optical system, in a state where the focal length is at a maximum;
• and
• y designates the maximum image height of the imaging plane.