Stigmatic broadband imaging spectrometer with a high numerical aperture

An advanced Dyson spectrometer has been presented for broadband stigmatic imaging. The spectrometer, with large enough axial spaces and lateral separation among the slit, the imaging plane, and the hemispherical lens, is composed of a thin hemispherical lens and two spherical lenses in the same material, and a reflection concave grating. The new spectrometer design maintains excellent optical performances and decreases inherent stray light of the concentric spectrometer with a high numerical aperture, which owns better engineering applicability.