The motion system of the interferometer is probably the most important (and most interesting) subsystem of a Fourier-transform spectrometer. It is essential to understand how errors generated in the interferometer's motion system affect the output spectra. It is the goal of this chapter to portray the links between them.
In any real motion system, âerroneousâ motion is unavoidable. Its characteristics and magnitude depend largely on the quality of its mechanical drive components and the design of the overall motion system. Ultimately, the achievable spectral SNR can easily be limited by this subsystem. Figure 4.1 shows three 100% lines from three different mirrors' drive subsystems, having different motion qualities. It can be seen that spectral SNR can be extremely low when the motion quality is poor. Here, motion âqualityâ refers to the proximity of the path of the actual motion to an ideal one. The ideal motion system in an interferometer has motion in only one degree of freedom, which is in the direction of the OPD.
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