Patent ID: 6646739
Filing Date: 2003-11-11
Classification: G01J,G02B

Abstract:
A four-stage type monochromator, comprising:a concave mirror for converting incident light which passed through a slit in an entrance slit plate into parallel light to output the parallel light; a plane diffraction grating for diffracting the parallel light emergent from said concave mirror; a plane mirror having a reflecting surface substantially perpendicular to an optical path of the diffracted light diffracted by said plane diffraction grating, for reflecting the diffracted light to cause the reflected light to be incident again on said plane diffracting grating; and a returning reflector for reflecting the diffracted light diffracted again by said plane diffraction grating and focused by said concave mirror; wherein the reflected light from said concave mirror is made incident upon said plane diffraction grating as third incident light, the diffracted light is reflected by said plane mirror and is made incident on said plane diffraction grating as fourth incident light, so as to output only light having a specific wavelength through a slit in an exit slit plate; and wherein said returning reflector includes a member for reversing a dispersing direction of the light before and after reflection.