Design and performance of toroidal holographic gratings.

A method is developed for designing an aberration-reduced toroidal holographic grating for use with monochromators which adopt simple grating-rotation for scanning. Procedure of determining the proper recording parameters is described. A ray-tracing formula is also derived for the evaluation of designed gratings. Comparative studies are made on the four types of grating an aberration-reduced toroidal holographic-, an aberration-reduced concave holographic-, a conventional toroidal-, and a conventional concave-grating. The performance of these gratings are evaluated in terms of spot diagrams, and the result is confirmed by the experiment carried out on aberration-reduced holographic gratings of toroidal and concave types which are specifically designed and produced for use with a Seya-Namioka monochromator.The results obtained both theoretically and experimentally show the usefulness of the present design method.