Design of freeform mirrors in Czerny-Turner spectrometers to suppress astigmatism.
Astigmatism is left uncorrected in traditional Czerny-Turner spectrometers with spherical mirrors, which leads to low throughput of modern instruments applying line-array detectors. By gradually varying the sagittal curvature, freeform mirrors are introduced to suppress astigmatism for a wide wavelength range simultaneously. So as not to reduce spectrum resolution, further calculations of the light path are performed for extra coma compensation. A design example is presented with optimized parameters. The ray-tracing result has revealed a reduction in sagittal spot size from several hundred micrometers to around 10 microm in the wavelength range from 200 nm to 800 nm.
Xu
Li
L
State Key Laboratory of Precision Measurement Technology and Instruments, Tsinghua University, 100084, Beijing, China. xulithu@hotmail.com
Chen
Kexin
K
He
Qingsheng
Q
Jin
Guofan
G