Patent ID: 8482851

Claim:
A projection optical system that enlarges and projects an original image on a reduction-side conjugate plane onto a magnification-side conjugate plane, comprising: a first optical system that forms an intermediate image conjugate to the original image; and a second optical system that forms a final image conjugate to the intermediate image on the magnification-side conjugate plane, wherein the first and second optical systems are arranged in order from a reduction side, the first optical system includes a plurality of lenses, the second optical system includes a reflecting mirror having a concave surface with an aspheric shape, and a first lens surface, which is a reduction-side surface, and a second lens surface, which is a magnification-side surface, of a lens closest to a magnification side in the first optical system satisfy the following conditional expressions: 0.1 <Z h /h ; and 0.5 <h/h max <1 where h indicates a height from an optical axis to an arbitrary point on the first lens surface or the second lens surface, h max indicates the maximum effective height of the first lens surface or the second lens surface, Z h indicates a displacement from a point on the first lens surface or the second lens surface on the optical axis to a point on the first lens surface or the second lens that is disposed at a height h from the optical axis in the optical axis direction where displacement to the magnification side is defined as positive.