Grating Monochromator Designs
A monochromator is a spectrometer that images a single wavelength or wavelength band at a time onto an exit slit; the spectrum is scanned by the relative motion of the entrance and/or exit optics (usually slits) with respect to the grating.A plane grating is one whose surface is flat. Plane gratings are normally used in collimated incident light, which is dispersed by wavelength but is not focused. Plane grating mounts generally require auxiliary optics, such as lenses or mirrors, to collect and focus the energy. Some simplified plane grating mounts illuminate the grating with converging light, though the focal properties of the system will then depend on wavelength. For simplicity, only plane reflection grating mounts are discussed below, though each mount may have a transmission grating analogue.