Holographic grating recorded using aspheric wavefronts for a Seya-Namioka monochromator

The geometric theory of the holographic grating is expanded to those recorded by use of aspheric wavefronts which can be easily made. General expressions are given for the groove function and the light path function. Additional terms in the groove function unique to this recording method suggest the possibility of sufficient compensation of coma aberration over conventional holographic gratings recorded with plane and spherical wavefronts. To confirm this advantage, we compared the imaging properties of a Seya-Namioka monochromator equipped with both types of grating, which were designed and fabricated by use of spherical and aspheric wavefronts. The experimental results confirm that our method enhances resolution and throughput of the monochromator.