| 摘要 |
A compact image-forming optical system is disclosed which has a high optical performance due to arranging a reflective optical unit and a refractive optical unit at suitable positions. The image-forming optical system is an optical system performing image formation from a magnifying side to a demagnifying side or from the demagnifying side to the magnifying side, and includes, in order from the magnifying side to the demagnifying side, a refractive optical unit having a positive optical power as a whole, and a reflective optical unit including at least three reflective surfaces. The image-forming optical system has a pupil on the magnifying side further from the reflective surface furthest on the magnifying side the reflective optical unit, and the focal length of the refractive optical unit is set to be within a range of 0.2 to 5 times the focal length of the reflective optical unit.
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