Multispectral techniques

Balogh, M.P and Li, J.B., HPLC Analysis of hypericin with photodiode-array and MS detection the advantages of multispectral techniques, LC-GC, 17(6), 558, 1999. 

False colors for the three black and white photographs belonging to the multispectral technique. Expose successively, a color photographic paper, with the three different black and white negatives, each one with a different filter, namely, red, green and blue. Preferably, use the red filter for the infrared negative. 

IR spectroscopy is a fast, simple, and cheap method for the qualitative detection of certain functional groups on insoluble supports [77-79]. Dried supports can be used directly to prepare KBr pellets for standard recording of IR spectra [54,80-82], Newer IR-based techniques, which require much less support material than required for a KBr pellet, include single-bead FT-IR spectroscopy [16,77,83-86], single-bead Raman spectroscopy [87], near-IR multispectral imaging [88], and the simultaneous analysis of several different beads by FT-IR microscopy for analysis of combinatorial libraries [89,90],... 

Tran, C. D. and Grishko, V. I. (2004) Determination of water contents in leaves by a near-infrared multispectral imaging technique. Microchem. J. 76, 91-94. 

Fischer, M. and Tran, C.D., Investigation of solid phase peptide synthesis by the near-infrared multispectral imaging technique a detection method for combinatorial chemistry, Anal. Chem., 71, 2255-2261, 1999. 

As a laboratory-based analytical technique, NIR imaging is an extension of NIR spectrometry. It accesses the same chemical information, but in a spatially resolved multispectral parallel approach. Laboratory devices are generally aimed at developing knowledge on product composition and at routine quality control. 

Within 10 years of the first attempts to use NIR multispectral or hyperspectral imaging for food products, prodigious advances have been achieved such that NIR hyperspectral imaging is now commonly used in both laboratory and on-line applications. Yet, this outstanding technique continues to raise many questions that must be addressed before it is more widely accepted. Such questions relate not only to the hardware and data processing but also to specific issues related to NIR imaging. 

To make multispectral time-resolved fluorescence measurements into a diagnostic tool, the technique must be combined with imaging. Direct imaging techniques by position-sensitive TCSPC are optically easy. They can be used with wide-field illumination and are easily integrated into endoscopes. However, it is difficult to obtain simultaneous spectral and temporal resolution. Several detectors must be used or several images of different wavelength be projected on one detector. True multispectral resolution cannot be obtained this way. 

It might be-useful to recall two photographic techniques, one linked to multispectral photography (false colors) and the other one, also in false colors but with only one photograph to be enhanced . 

This chapter has enabled us to touch upon some technical aspects, knowledge of which is essential for interpreting information gathered at a distance. Multispectral photography preferably associated with three-dimensional techniques, and exploitation of the infrared and microwave bands, open still-unsuspected prospects to the earth sciences, whether the carrier platforms are on Earth or are air- or satellite-borne. In the next chapter, we will drop back to Earth and look at some of these future prospects. 

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