Interferogram reconstructed

Fig. 6.4 Interferogram reconstruction. Modulation period is n times the sampling time (here for n = 6). n interferograms (each of m points) are recorded, with different phases of the modulation with respect to the sampling grid. Through proper selection...

Figure 3.11. (a) Chirped interferogram (b) phase-corrected spectrum of the source calculated from this interferogram (c) almost completely unchirped interferogram reconstructed from this spectrum. (Reproduced from [7], by permission of the Society for Applied Spectroscopy copyright 1974.)... 

Figure 15. Relationship between transient source emission at different times and reconstructed interferograms (31)...

Figure 12.7 Acquisition and reconstruction of interferograms in stcp-scan acquisition mode.

To obtain IR spectra on a time scale of nanoseconds, the sample cell in conventional spectrometers is usually excited by an Nd YAG laser. Flow cells with a pathlength of at least 0.1 mm must be used for photoreactive samples and the pulse repetition frequency is then limited to 1 Hz. In step scan FTIR spectroscopy,211 the time evolution is collected at single points of the interferogram, which is then reconstructed point-by-point and subsequently transformed to time-resolved IR spectra. Alternatively, dispersive instruments equipped with a strong IR source can be used.212 The time resolution of both methods is about 50 ns. FTIR instruments provide a triggerable fast-scan mode to collect a complete spectrum within a few milliseconds.213... 

A sensitive technique used for real time reconstruction of chromatograms from the interferogram is the Gram Schmidt vector orthogonalization method. The Gram Schmidt method relies on the fact that the interferogram contains information on absorbing samples at all optical retardations less than the reciprocal of the width of each band in the spectrum. 

If the unique cosine waves can be extracted from the interferogram, the contribution from each wavelength can be obtained. These individual wavelength contributions can be reconstructed to give the spectmm in the frequency domain, that is, the usual spectmm obtained from a dispersive spectrometer. A Fourier transform is used to convert the... 

The datacube reconstruction from detected interferograms has been performed. Initial steps consist of the noise reduction and time domain interpolation when instrument errors have been included in the simulation. Once the data has been reduced, the dirty datacube is calculated in two steps first through Fourier transforming in the wavenumber domain and second through two dimensional Fourier transforming in the spatial domain. 

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