A grism combines an optical prism with a diffraction grating. Their angular deviations can be chosen to cancel at a selected wavelength, while neighboring wavelengths emerge in different directions. This lets an instrument introduce spectral dispersion with approximately straight-through propagation at its design wavelength.
Inserting the grism into an imaging beam turns compact object images into dispersed optical spectra. The cancellation is wavelength-specific and order-specific: overlapping spectra and other diffraction orders remain potential sources of confusion. An optical filter can restrict the recorded band.
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A grism is an optical component used in spectroscopes and other imaging devices to disperse light into its constituent wavelengths. It combines the functions of a grating and a prism: it consists of a transparent optical element, typically made of glass, that has a diffraction grating etched onto one of its surfaces. The grism operates by diffracting light into different wavelengths, allowing for spectroscopic analysis.