Patent ID: 8029147

Claim:
A projection optical system having a magnification side and a reduction side for forming a magnified image on a magnification side image surface that is conjugate with a reduction side image surface, said projection optical system comprising, arranged in order from the reduction side: a first imaging system including a plurality of lens elements and lens components arranged along an optical axis; and a second imaging system including a mirror having a concave, aspheric reflecting surface; wherein an intermediate image is formed between said first imaging system and said second imaging system; said reduction side image surface is located on one side of the optical axis of the first imaging system, thereby causing said reduction side image surface and said intermediate image to be located across the optical axis of the first imaging system; and the reflecting surface of said mirror is made to be a rotationally-symmetrical surface wherein the following condition is satisfied: 0.55<|tan θ1|<0.84 where θ 1 is the maximum angle among all the angles that principal rays from said first imaging system to said second imaging system make with the normal to said reduction side conjugate image surface.