Patent ID: 7075726

Claim:
A projection optical system for projecting an image of an object onto an image plane, comprising: a first imaging optical system for forming an intermediate image of the object, said first imaging optical system including (i) a first lens unit having a positive power, (ii) a first optical unit having a first mirror for reflecting and collecting abaxial light from the object, (iii) a second optical unit having a second mirror for reflecting light from said first mirror to the image plane side, with which the abaxial light is caused to pass an outside of an effective diameter of said first mirror, and (iv) a second lens unit having a negative power and being disposed between said first and second mirrors; a second imaging optical system for re-imaging the image upon the image plane; and a field optical system disposed between said first imaging optical system and said second imaging optical system, for projecting a pupil of said first imaging optical system onto said second imaging optical system, said field optical system including a first field mirror unit having a first field mirror, a second field mirror unit having a second field mirror, and one positive lens disposed adjacent the image plane side of said first mirror.