Spectral prism spectrometer

In conclusion it can be stated that the spectral optical conductance for a prism spectrometer, a grating spectrometer, and a Michelson interferometer are approximately as 1 10 1000. 

For prism spectrometers, the spectral transmission depends on the material of the prism and the lenses. Using fused quartz, the accessible spectral range spans from about 180 to 3000 nm. Below 180nm (vacuum-ultraviolet region), the whole spectrograph must be evacuated, and lithium fluoride or calcium fluoride must be used for the prism and the lenses, although most VUV spectrometers are equipped with reflection gratings and mirrors. 

In Summary The advantage of a prism spectrometer is the unambiguous assignment of wavelengths, since the position S2(X) is a monotonic function of X. Its drawback is the moderate spectral resolution. It is mostly used for survey scans of extended spectral regions. 

For a prism spectrometer with a Littrow mounting, the spectral slit width is s = Sg + So + ... 

The free spectral range of a spectrometer is the wavelength interval 8X of the incident radiation for which a one-valued relation exists between A and the position x(A) of the entrance-slit image. While for prism spectrometers the free spectral range covers the whole region of normal dispersion of the prism material, for grating spectrometers SX is determined by the diffraction order m and decreases with increasing m (Sect.4.1.3). 

The early Fourier transform spectrometers, which were nearly all home made, came into being to measure spectral features which were clearly too weak to measure with a grating or prism spectrometer and bolometer combination. They were small instruments having modest resolution and wavelength coverage. 

Figure 7.2 Optical block diagram of the wide field Kerr-gated microscope. Note the position of the sample (S), the sequence of three matched Cassegrain objectives (COi, CO2 and CO3), polarizers (Pi and P2), the Kerr medium (K) and blocking filters (F). A prism spectrometer (PR) can be inserted into the path of the gated light allowing monitoring of the collective spectral dynamics of objects within the field of view.

The first requirement is a source of infrared radiation that emits all frequencies of the spectral range being studied. This polychromatic beam is analyzed by a monochromator, formerly a system of prisms, today diffraction gratings. The movement of the monochromator causes the spectrum from the source to scan across an exit slit onto the detector. This kind of spectrometer in which the range of wavelengths is swept as a function of time and monochromator movement is called the dispersive type. 

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