Broadband astigmatism-corrected spectrometer design using a toroidal lens and a special filter

•Correcting astigmatism with a toroidal lens in Czerny–Turner spectrometer.•Proposed a method to eliminate non-need diffraction order light.•In a modified spectrometer any original optical elements have not been changed or moved.•The specific design process and an example are presented.

In the paper, a method to obtain a broadband, astigmatism-corrected spectrometer based on the existing Czerny–Turner spectrometer is proposed. The theories of astigmatism correction using a toroidal lens and a special filter are described in detail. Performance comparisons of the modified spectrometer and the traditional spectrometer are also presented. Results show that with the new design the RMS spot radius in sagittal view is one-eightieth of that in the traditional spectrometer over a broadband spectral range from 300 to 700 nm, without changing or moving any optical elements in the traditional spectrometer.