It is possible by modern methods to shape the grooves of a grating in such a manner that a major portion of the incident flux is reflected into the desired order and wavelength region; but this wavelength region of high efficiency is small for gratings used in conventional mounts. By solving, simultaneously, the law of specular reflection and the grating diffraction law, it is possible to determine the conditions for working on the blaze, that wavelength region for which the direction of diffracted flux coincides with that of specularly reflected flux. It can be shown that by rotation of the grating in combination with rotation and translation of a plane mirror from which the diffracted flux is reflected, the grating may be used on the blaze over wide wavelength regions in a particular order. Design equations are derived and examples of visible and infrared applications are given. The system is particularly applicable to infrared spectrometry where ordinarily several gratings are required to cover the desired wavelength range.
© 1951 Optical Society of America
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