Patent ID: 6842280

Claim:
An optical system comprising: an optical element including (a) a first optical component for forming an intermediate image of an object and having a refractive surface of rotationally asymmetric shape and at least one reflective surface, and (b) a second optical component for forming a final image with light from the intermediate image and having a refractive surface of rotationally asymmetric shape and at least one reflective surface; and an aperture stop, wherein the following relation is satisfied:  D · f1 S · AR1  < 0.1 where D is a size of a noise source near the intermediate image, f 1 is a maximum focal length of said first optical component out of those dependent upon azimuths, an azimuth at the maximum focal length of said first optical component being defined as ξ, S is an on-axis astigmatic difference at the intermediate image position, and AR 1 is a diameter of an exit pupil by said first optical component in correspondence to the azimuth ξ, at the time an aperture of said aperture stop is maximized.