| 摘要 |
A projection optical system for projecting an image of an object onto an image plane. The projection optical system includes a first imaging optical system for forming an image of the object in which the first imaging optical system includes a first mirror for reflecting and collecting abaxial light from the object, a second imaging optical system for re-imaging the image upon the image plane, a second mirror for reflecting light from the first mirror to the image plane side, whereby the abaxial light is caused to pass outside of an effective diameter of the first mirror, and a field optical system including three lenses each having a positive refractive power. The abaxial light passed through the outside of the effective diameter of the first mirror is refracted by the three lenses toward a direction nearing an optical axis of the three lenses. Light that has passed through the three lenses is directed to the second imaging optical system, and the first and second imaging optical systems are disposed along a common optical axis.
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