High Speed Planar Array Infrared PA-IR Spectrograph

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Recently a new paradigm for doing infrared (IR) spectroscopy was developed in the Principal Investigator's (Pl's) laboratory. PA-IR uses a focal plane array (FPA) detector onto which a beam of light dispersed by a prism or grating is focused. The broad range of frequencies displayed on the pixel array simultaneously make this a multiplex technique without using the complex scanning mechanism or computational requirements (for Fourier transformation of the data) used in FT-IR interferometry. Thus the no-moving parts configuration of the PA-IR instrument provides the ruggedness required to make the instrument the size of a "shoe-box" and hence portable. In addition the increased sensitivity (100-1000X over single element FT-IR detectors) of the FPA can provide an IR spectrum to be accumulated in as little as 10 microseconds. The only current limitation comes from the frequency range available (3400-2000 cm[-1]) due to the initial availability of only indium-antimonide FPAs during the development of the prototype.

This proposal is to design and construct a portable "broad band" PA-IR instrument that works in the more traditional IR "fingerprint" region (2000-800 cm [-1]) now that Mercury-Cadmium-Telluride FPAs are commercially available and show that it has the sensitivity and speed for in vivo disease prediction/diagnosis. If the PA-IR instrument is coupled with an IR fiber optic sampling probe, it should be possible to characterize ocular tissues in the lens. The advantage of this fiber optic PA-IR technique over conventional dynamic light scattering (DLS) systems currently in use for eye diagnostics is that PA-IR will provide a chemical signature of the various components (collagen IV, gamma-crystallin, etc.) present simultaneously in the "real-time" domain potentially allowing both qualitative and quantitative analysis of the components. For example, PA-IR would allow the detection of protein aggregation (dimers, oligomers) and be able to detect changes in the amount of alpha-helical, beta-sheet or disordered conformation in a protein thereby detecting the onset of cataracts at a very early stage before protein particles become large enough to be detected by DLS. Once this "broad Band" PA-IR is shown to have high sensitivity then other applications such as monitoring the presence of airborne bacteria and viruses in hospital environments becomes feasible as well.

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