Patent ID: 7336426
Filing Date: 2008-02-26
Classification: G02B

Abstract:
1. An image pickup optical system for forming a light flux from an object into an optical image on an image pickup element, the image pickup optical system comprising, in order from an object side thereof: a first lens group having a positive power; a second lens group having a negative power; a third lens group having a positive power; a fourth lens group having a negative power; and a fifth lens group, wherein a distance between each neighboring lens groups among the first to fifth lens groups changes with the fourth lens group positioned at a fixed distance to an image surface of the image pickup optical system, for varying power of the image pickup optical system from a wide-angle end to a telephoto end, the fourth lens group moves in a direction substantially perpendicular to an optical axis for a shake compensation, and the image pickup optical system fulfills following conditional formulas: where f1 is a focal length of the first lens group, fw is a focal length of the image pickup optical system at the wide-angle end, f4 is a focal length of the fourth lens group, and ft is a focal length of the image pickup optical system at the telephoto end.