| 摘要 |
A catadioptric unit includes, in order from an object side to an image side, a first optical element including a first transmissive unit having positive refractive power disposed in the vicinity of an optical axis and, on the object side thereof, a first reflective unit disposed at an outer circumference relative to the first transmissive unit and having a reflective surface; and a second optical element including a second transmissive unit having negative refractive power in the vicinity of the optical axis and, on the image side thereof, a second reflective unit disposed at an outer circumference relative to the second transmissive unit and having a reflective surface. Radii of curvature of object-side and image-side surfaces of the second optical element, a thickness along the optical axis and a refractive index of a material of the second optical element are set to satisfy predetermined conditions.
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