| 摘要 |
PROBLEM TO BE SOLVED: To provide a projection optical system which can secure a large and substantial image-side numerical aperture by excellently suppressing reflection loss on an optical surface by interposing a medium with a high refractive index in an optical path to an image plane. SOLUTION: The projection optical system forms an image of a 1st surface (R) on a 2nd surface (W). The projection optical system has a boundary lens (L211; Lb) whose 1st surface has positive refracting power, the optical path between the boundary lens and the 2nd surface is filled with a medium having a refractive index larger than 1.1, and a condition ¾Ns-Nm¾<0.08 is met, where Nm is the refractive index of the medium and Ns the refractive index of an optical material forming the boundary lens. In the optical path between the boundary lens and 2nd surface, at least one optical member (Lp) having nearly no refracting power is arranged to be freely insertably and extractably. COPYRIGHT: (C)2004,JPO&NCIPI
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