Spectroscopic instrument with offset grating

摘要

In a spectroscopic instrument having a spherical grating to disperse incident light into a spectrum, the grating is oscillated on axis to scan the light passing through an exit slit through the spectrum or a portion of the spectrum. The axis of rotation of the grating is shifted to be displaced from tangent to the center of the spherical grating so that the light passing through the exit slit is substantially focused throughout the spectrum scanned by the instrument. The grating is mounted in the holder to shift the center of gravity of the grating and the holder to be on the axis on which the grating is pivoted. <IMAGE>