Grism

The advantage of grisms is that the same camera can be used both for imaging (without the grism) and spectroscopy (with the grism) without having to be moved.

If this grism is placed in an ƒ/4 beam at s = 120 mm, the plate factor P ≈ 1100 Å/mm.

As the name implies, grisms are a combination of a transmission grating and a prism. One common configuration uses the refraction at the grism surface to redirect nonzero diffractive orders along the original optical path.

The grism usually consists of an SR transmission grating mounted on the hypotenuse of a right-angle prism.[…]Volumetric phase holographic grisms, which are capable of relatively high angular dispersions, have begun to appear.