Agrism (also called agrating prism) is a combination of aprism andgrating arranged so thatlight at a chosen centralwavelength passes straight through. The advantage of this arrangement is that one and the same camera can be used both for imaging (without the grism) and spectroscopy (with the grism) without having to be moved. Grisms are inserted into a camera beam that is alreadycollimated. They then create adispersedspectrum centered on the object's location in the camera'sfield of view.
Theresolution of a grism is proportional to thetangent of the wedge angle of the prism in much the same way as the resolutions of gratings are proportional to the angle between the input and the normal to the grating.
The dispersed wavefront sensing system (as part theNIRCam instrument) on theJames Webb Space Telescope uses grisms.[1] The system allows coarse optical path length matching between the different mirror segments.
 | Thisspectroscopy-related article is astub. You can help Wikipedia byexpanding it. |
