Third-generation Rowland holographic mounting.

Holographic gratings using aspheric blanks and/or aberrated laser recording sources are most often required to achieve high spectral resolution over a large spectral range. We propose a configuration derived from the optimized holographic Rowland mounting, where the grating is recorded by the interference of two aberrated wave fronts diffracted from concave holographic gratings. These two auxiliary gratings are recorded with laser point sources, and the three blanks are spherical, which is well suited to the severe far-UV constraints on shape and polishing. In addition to the correction of astigmatism, coma C(1), and spherical aberration S(1) given by the optimized Rowland mounting, this mounting cancels, at least at one point of the spectrum, coma C(2) and spherical aberrations S(2) and S(3).