Echelle spectrometer crossed-grating

In addition, Echelle spectrometers are often used [50], By combination of an order-sorter and an Echelle grating either in parallel or in crossed-dispersion mode, high practical resolution (up to 300 000) can be realized with an instrument of fairly low focal length (down to 0.5 m) (Fig. 94). Therefore, the stability as well as the luminosity are high. By using an exit slit mask with a high number of preadjusted slits, highly flexible and rapid multielement determinations are possible. 

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. 

Figure 2.27 An echelle spectrometer optical layout. The eohelle grating disperses the light to a second wavelength selector, called a cross disperser. The cross disperser may be a prism or a conventional grating. [ 1993-2014 PerkinElmer, Inc. All rights reserved. Printed with permission.

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