| 摘要 |
PROBLEM TO BE SOLVED: To simultaneously measure multipoints with high efficiency and high accuracy without having a movable part by providing a spectral means composed of a prism having two spherical surfaces and a concave mirror having a spherical surface. SOLUTION: A prism 1 has two spherical surfaces 3, 7, and is formed of a material of quality having a refractive index (n). When arranging an object 11 in the vicinity of an external conjugate surface 13, in the case where an input space medium is air, the first spherical surface 3 forms a virtual image 15 of the object 11 in the vicinity of a stigmatic internal conjugate surface 17 at a distance of R1/n from the center 5. A point 15 is positioned at an intersection between a circle 17 and a circle 19, and the second spherical surface 7 forms a second virtual image 21 on a stigmatic external conjugate surface 23. The image is relayed to a concave mirror 27 having the curve center 29 arranged in the almost middle between a point 21 and a point 25. The light reflected by the concave mirror 27 concentrates on the point 25. The reflected light again reaches the second spherical surface 7 of the prism 1 to place a focus on a fourth virtual image 31. Finally, the first spherical surface 3 of the prism 1 forms a real image 33 on the last image forming point.
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