A geometric theory is developed for a spherical concave diffraction grating that has variable line spacing and curved grooves and can be produced with existing technology. The aberration coefficients of this grating are determined. A comparison of these coefficients with the corresponding coefficients of holographic gratings and with code v polynomial coefficients gives a clearer understanding of the similarity and difference between mechanically ruled and holographically recorded concave gratings and allows the optimization of these gratings with standard computer programs.
© 2004 Optical Society of America
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