Patent ID: 8455810

Claim:
An optical element incorporated into an imaging optical system, comprising: an effective diameter area that allows effective light flux contributing to imaging to pass; a non-effective diameter area that surrounds the effective diameter area; and an outer peripheral face that surrounds the non-effective diameter area, wherein the effective diameter area, the non-effective diameter area and the outer peripheral face are centered on an imaging optical axis, at least a thickness-direction part of the outer peripheral face or a circumferential part thereof is a non-parallel face being inclined with respect to the imaging optical axis so that the outer diameter of the optical element at the non-parallel face gradually increases toward an image-plane side, and a light incident from a face of an object side, reflected on a face of the image-plane side to the outer peripheral face and reflected on the outer peripheral face is not incident to an image plane, wherein the optical element is incorporated with a plurality of lenses into the imaging optical system.