SPECTROSCOPIC INSTRUMENT WITH OFFSET GRATING TO IMPROVE FOCUS

摘要

In a spectroscopic instrument having a spherical grating to disperse incidentlight into a spectrum, the grating is oscillated on axis to scan the lightpassingthrough an exit slit through the spectrum or a portion of the spectrum. Theaxis ofrotation of the grating is shifted to be displaced from tangent to the centerof thespherical grating so that the light passing through the exit slit issubstantiallyfocused throughout the spectrum scanned by the instrument. The grating ismounted in the holder to shift the center of gravity of the grating and theholder tobe on the axis on which the grating is pivoted.