Astigmatism-free Czerny-Turner spectrometer with a low f-number by a bicylinder lens.

A modified optical design for a broadband astigmatism-corrected Czerny-Turner spectrometer with high resolution and large throughput is presented. The theory of astigmatism correction is analyzed with the use of a bicylinder lens with different radii of curvature in tangential and sagittal planes. The optical performances of a modified spectrometer and two traditional spectrometers are compared in detail. The results show that the modified Czerny-Turner spectrometer can obtain superior astigmatism-free performance, an f-number of 2.5, and spectral resolution of 1.5 nm in 350-750 nm. Its volume decreases by approximately 77% compared with a traditional spectrometer with the same f-number.