Spectrometer Instrumental Bandpass
The instrumental bandpass of an optical spectrometer depends on both the dimensions of the image of the entrance slit and the exit slit dimensions.In cases where the image of the entrance slit is wider than the exit slit (that is, w' > w"), the instrumental bandpass is said to be imaging limited, whereas in those cases where the exit slit is wider than the image of the entrance slit (w' < w"), the instrumental bandpass is said to be slit limited. [When an imaging-limited optical system is imaging limited due primarily to the grating, either because of the resolving power of the grating or due to its wavefront errors, the system is said to be grating limited.]