| Hadamard transform (HT) spectrometer has been developed which can be used for Raman spectroscopy in the near-infrared (NIR). Several liquid crystal electro-optic shutter arrays were tested as possible stationary Hadamard encoding masks. This Hadamard transform Raman instrument is able to do simultaneous multi-wavelength detection with a single diode as the detector. Hadamard transform spectrometers have many advantages similar to Fourier transform spectrometers and also have the advantage of no continuously moving parts.;Three different liquid crystal displays were used as stationary Hadamard encoding masks. Many problems, previously observed with movable Hadamard encoding masks, were eliminated with the stationary character of liquid crystal displays. However, problems with poor optical transmission and polarization effects warrant the continual search for new switching materials.;A 127 element cholesteric liquid crystal optical shutter array was used to acquire NIR HT-Raman spectra. The frequency precision advantage is demonstrated by performing spectral subtraction on a mixture, and coaddition is performed to show how the signal-to-noise ratio can be improved.;Two second generation 255 element stationary Hadamard encoding masks have been constructed and have significant advantages over the original cholesteric liquid crystal masks. Some of these advantages include the absence of polarizers and smaller pixel sizes, which yield better resolution. The multiplex advantage is demonstrated by HT-Raman with a polymer-dispersed-liquid-crystal mask. The selective multiplex advantage is presented in detail using HT-Raman spectra as an example of the advantages gained. In addition, the ability to quantitate HT-Raman data in the spectral domain and the encodegram domain is demonstrated using a mixture of two liquids.;Fluorescence has been a major problem with visible Raman spectrometry. The near-infrared Nd:YAG laser (1.064... |
