Modified concentric spectrograph

摘要

A modified concentric spectrograph for diffracting light with high stray light rejection without astigmatism is provided. The modified spectrograph includes a grating, a lens, and at least one entrance port and one exit port. The grating has a concave surface and a meridian plane with a first side and a second side. The lens has a substantially planar surface and a convex surface. Preferably, the convex and concave surfaces are substantially concentric. The ports are substantially located on different sides of the meridian plane near a focal plane of the spectrograph. The position of a focal plane may be modified using an optically transmissive triangular prism with a reflective surface, and an optically transmissive block. The position of a focal plane may further be modified with one or more optically transmissive plates. Methods for using the spectrograph are also provided.