Patent ID: 8135267

Claim:
An image pickup device comprising: a focus lens unit that moves during focusing; a magnification lens unit that moves during zooming; a splitting optical system disposed in an optical path on an image side of the focus lens unit, wherein the splitting optical system splits a light beam from a subject into a reflected light beam and a passed light beam, and wherein the passed light beam is used for imaging the subject image; an image pickup element to which the passed light beam through the focus lens unit and the magnification lens unit is directed; a focus detection unit that detects a focus state of the subject image by using the reflected light beam split in the splitting optical system; and a drive unit that drives the focus lens unit to a focal position for imaging the subject image by using the passed light beam based on the detection result of the focus detection unit; wherein a reflectance of the splitting optical system against the light beam from the subject has a distribution in which the reflectance is of the maximal value on an optical axis and becomes gradually lower as the light beam is away from the optical axis, and the distribution has rotational symmetry about the optical axis; and wherein the focus detection unit detects the focus state of the subject image by using a portion of the reflected light beam which is reflected by the higher reflectance portion of the splitting optical portion including the optical axis.