Beam shape effects on grating spectrometer resolution

The collimated optical beam in a grating spectrometer may be circular or el liptical in cross section, so that different parts of the beam illuminate d ifferent numbers of grooves on the grating. Here we estimate the consequent loss in spectral resolution relative to that obtained with a beam that ill uminates a fixed number of grooves. The effect reduces the intrinsic resolv ing power of the spectrometer by similar to 15%, exclusive of other contrib utions such as finite entrance-slit width. (C) 2000 Optical Society of Amer ica OCIS codes: 050.1940, 050.1950.