Abstract: An optical splitter includes a housing, a diffraction grating, and an optical filter. An incidence unit and an emission unit are provided in the housing. The optical filter is disposed between the emission unit and the diffraction grating in the housing. An anti-reflection coating is formed on a surface of a filter main body of the optical filter on the emission unit side. Therefore, from light dispersed by the diffraction grating and having passed through the optical filter, light reflected at a back surface of the emission unit passes through the optical filter without being reflected by a back surface of the optical filter and is directed toward the inside of the housing. As a result, light having passed through the optical filter and having a wavelength other than a target wavelength is inhibited from being emitted from an emission slit of the emission unit.

Abstract: A spectrometer includes a grating, a cylinder retainer and a housing. The grating comprises a grating surface having a concave toroidal form. The retainer comprises an end surface having a convex contact surface compatible with the grating surface, wherein the contact surface contacts with the grating surface. The housing includes an opening which the retainer fits in.

Abstract: An optical splitter includes a housing, a diffraction grating, and an optical filter. An incidence unit and an emission unit are provided in the housing. The optical filter is disposed between the emission unit and the diffraction grating in the housing. An anti-reflection coating is formed on a surface of a filter main body of the optical filter on the emission unit side. Therefore, from light dispersed by the diffraction grating and having passed through the optical filter, light reflected at a back surface of the emission unit passes through the optical filter without being reflected by a back surface of the optical filter and is directed toward the inside of the housing. As a result, light having passed through the optical filter and having a wavelength other than a target wavelength is inhibited from being emitted from an emission slit of the emission unit.