Echelle gratings linear dispersion

The spectrometer used is a modified Spectrametrics Spectraspan III echelle grating spectrometer with a quartz prism cross disperser. An echelle spectrometer was chosen because of its two dimensional format display. This format allows efficient simultaneous examination of a much wider spectral range than with a linear dispersion spectrometer when a two dimensional television camera type detector is used. 

The linear dispersion of an echelle grating dl/dX) is the focal length of the spectrometer (/) multiplied by the angular dispersion ... 

In 1949 Harrison described the production of a grating intermediate between the Michelson echelon and the Wood echelette, which he called an echelle. The echelle grating possesses properties different from those of other gratings, particularly as to the method by which high resolution and linear dispersion are achieved. 

Quimby et al used a prototype version of the Spectraspan III echelle grating monochromator (Spectrametrics, Inc., Andover, Mass.) with a reciprocal linear dispersion of 0.122 nm/mm at 400 nm. The entrance slit width was 50 m slit height, 500 m exit slit width,... 

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