1. An optical element comprising: an object-side imaging element for imaging an object on an intermediate image plane in an optical path; and an image-side imaging element for reimaging an object image formed on the intermediate image plane, on a final image plane, wherein at least one of said object-side imaging element and said image-side imaging element comprises an off-axial curved surface, and wherein aberration is generated by both of the object-side imaging element and the image-side imaging element, so as to flatten (disturbance of) a light intensity distribution on the final image plane, caused by a noise source at or near the intermediate image plane.