| 摘要 |
PROBLEM TO BE SOLVED: To obtain a high speed and wide angle imaging optical system by reducing astigmatism and improving imaging performance. SOLUTION: The imaging optical system has three reflection mirrors of a first reflection mirror 1, a second reflection mirror 2 and a third reflection mirror 3, which are arranged in the described order on the optical path of incident light, and the light beams reflected on the three reflection mirrors form an imaging plane 4, wherein a plane including the incident center main light beam to the first reflection mirror and the reflection center main light beam to the first reflection mirror is defined as a plane A, a plane including the incident center main light beam to the second reflection mirror and the reflection center main light beam to the second reflection mirror is defined as a plane B, a plane including the incident center main light beam to the third reflection mirror and the reflection center main light beam to the third reflection mirror is defined as a plane C, respectively, in terms of the central main light beams defined as the main light beams which are focused on the center of the imaging plane, the plane A and the plane C do not coincide, and the angle differenceΔν= ¾ν1-ν2¾ is 45°or smaller, whereν1 stands for the angle between the plane A and the plane B, andν2 stands for the angle between the plane C and the plane B. COPYRIGHT: (C)2009,JPO&INPIT
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