Lime-domain signals

Pyroelectric transducers exhibit response limes thal are fast enough to allow them lo track the changes in the lime-domain signal from an interferometer. For Ihis reason, most Fourier transform infrared spectrometers use this type of transducer. 

Figure 7-42 is a lime-domain signal from a source that contains many wavelengths. It is considerably more complex than those shown in Figure 7-41. Because a large number of wavelengths arc involved, a full cycle is not completed in the time period shown. A pailcrii of beats appears as certain wavelengths pass in and out of phase. In general, the signal power de-...

It is important to appreciate that a lime-domain signal contains the same information as a spectrum does in the frequency domain, and in fact, one can be... 

It is possible to show that to resolve two lines, Ihe lime-domain signal must be scanned long enough so that one complete cycle, or beat, for Ihe two lines is... 

TTic inierconversion of lime- and frequency-domain signals is complex and mathcmatfcally ledious when more Ilian a few lines are involved the operation is only practical with a computer.Today fast Fourier Iransform algorithms allow calculation of frequency-domain spectra from lime-domain spectra in seconds or less. 

The modes of encoding information as electrical quantities can be subdivided into analog domains, lime domains, and the digital domain, as illustrated in the bottom half of the circular map in Figure 1-2. Note that the digital domain is not only composed of electrical signals but also includes one nonelectrical representation, because numbers presented on any type of display convey digital information. 

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