Theoretical and experimental study on anamorphosis correction of Czerny-Turner imaging spectrometers.

The structure of an astigmatism-corrected Czerny-Turner imaging spectrometer will produce the focal length difference between sagittal rays and tangential rays, which contributes to the magnification difference in the spectral and spatial dimensions of the images. In this paper, the common characteristics of two optical path structures based on the Czerny-Turner imaging spectrometer to correct astigmatism (using a cylindrical and a toroidal mirror) are discussed. The magnification differences in the spectral and spatial dimensions of the image when the gratings are at zero-order and first-order diffraction and the influence of image magnification of different wavelengths are analyzed. The correction formula, methods of anamorphosis, and their common characteristics are given as well. The validity of the correction formula of anamorphosis is verified with theoretical calculation, ray tracing simulation, and experimental measurements with the imaging spectrometers. Meanwhile, this method is useful for the anamorphosis correction of an off-axis dispersion imaging spectrometer in other operating conditions of collimated light.