| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical device capable of photographing an object with reduced distortions. SOLUTION: This optical device is provided with a main mirror, having a reflection surface in rotationally symmetric shape with respect to a rotary shaft and reflecting incident light expressing the image of the object as the 1st order reflected light, and a sub mirror having a reflection surface in a rotationally symmetric shape with respect to the rotary shaft, reflecting the 1st order reflected light reflected by the main mirror as 2nd order reflected light and condensing the light at a viewing point. If the incident angle of the incident light on the rotary shaft is defined as an incident angleθ(0<=θ<=θmax) on the main mirror and the incident angle of the 2nd order reflected light with respect to the rotary shaft is defined as an incident angleϕ(0<=ϕ<=ϕmax) on the viewing point, the incident angleθon the main mirror satisfies inequality (1).
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