| 摘要 |
PROBLEM TO BE SOLVED: To provide a compact high-performance prism optical system where aberration caused by eccentricity is excellently compensated by appropriately using a rotationally asymmetric surface. SOLUTION: This optical system is constituted of a 1st translucent surface 4, a 1st reflection surface 5, a 2nd reflection surface 6, a 3rd reflection surface 7 and a 2nd translucent surface 8 in order that a light beam passes from an object side. In the case of projecting an axial principal light beam 1 to a plane regulated by three points on the light beam 1 on the surfaces 4, 5 and 6, the projected axial principal light beam is bent in the same direction by two continuous reflection surfaces 5 and 6 by setting the advancing direction of the light beam as reference, and it takes an optical path bent in a different direction therefrom on another surface 7. Then, at least one reflection surface is the rotationally asymmetric surface.
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