| 摘要 |
PURPOSE:To excellently maintain image-forming efficiency in a fixed region by a method wherein the first and the second image-forming system having reflecting and reflecting systems are arranged, the shape of a reflecting mirror and a lens is specified, and they are constituted in such a manner that the image-formation multiplying factor is reduced as a whole. CONSTITUTION:The luminous flux coming from the point P1 in the prescribed region on the optical axis is reflected in the order of reflecting mirrors M11, M12 and M13, and after passing through the lens 11, the luminous flux is image-formed at the first image point P1'. Also, the first image point P1' is turned to the point P2 of the second image-forming system, and the luminous flux coming from P2 passes through lenses L21 and L22, a concave mirror M21 and two lenses L21 and L22, and image-formed at the second image point P2. Especially, the out-of-axis aberration and the block aberration frequently occurring when a reducing system is constituted can be corrected by arranging the meniscus-formed lens L11 in such a manner that the luminous flux only reflected by the concave mirror M12 pass through the lens L11. As a result, the image-forming efficiency can be excellently maintained in the region of a fixed range on the optical axis, and a highly efficient catadioptric system, having a large caliber, can be accomplished.
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