| 摘要 |
PURPOSE:To hold bright and high wavelength resolution and space resolution, by constituting a collimator lens with three lenses at least and allowing the length between the collimator lens and an entrance slit, the area of an exit slit, etc. to satisfy a specific conditional inequality. CONSTITUTION:The luminous flux from an entrance slit S1 becomes a parallel luminous flux through a collimator lens L and reaches a reflective diffraction grating G, and the reflected diffracted light is condensed on an exit slit S2 by the collimator lens L, and a spectrum image is formed thereon. In this case, this optical system is so constituted that a length d0 between the collimator lens L and the extrance slit S1, a length l between the exit slit S2 and an image S'1 of the entrance slit formed by the light which is reflected by the surface of an optional lens, for example, the j-th lens of the collimator lens L, and an area S of the exit slit S2 satisfy the relation of expression I. |
