Optical system design of aberration-corrected Czerny–Turner imaging spectrometer with high resolution

Czerny–Turner spectrometers have large and difficult to correct aberrations resulted from off-axis spherical mirrors, which affects the quality of spectrometer imaging and limits its further application in the field of analysis. In this paper, a method to suppress systematical aberrations at low cost for high-resolution Czerny–Turner spectrometers is proposed. It corrects the coma at the scanning center wavelength by the Shafer equation and reduces the coma over a wide spectral range, and corrects the field curvature by optimizing the raster position. It corrects the astigmatism at the scanning center wavelength by adding a cylindrical lens between the converging mirror and the CCD, and suppresses the astigmatism over the wide spectral range by tuning the relative angle between the cylindrical lens and the image plane. It improves the image quality and resolution of the conventional spectrometer. An instrument based on the proposed method is developed. Simulation analyses and experimental results indicate that the proposed method can significantly suppress the aberration of the spectrometer, and compress the spot width by 91.4% and reach the resolution of 0.0192 nm which is 15.8% higher than that of a unmodified spectrometer. Therefore, the proposed method and the corresponding instrument can meet the requirements of high-resolution detection such as Raman spectrum.