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NIRS spectra contain all the information about the samples that can be evaluated. In addition to the content substances that are to be determined, there are frequently other influences to which the samples are subject at the time of measurement which are determined in the spectra. These can impair the determination of the desired content substance, but in part they also contain valuable information about the sample.
Modern NIRS devices can often accommodate many hundreds of wavelengths in the form of discrete data points for one sample. In this situation, bands in the NIR often extend over several wavelengths which are determined in accordance with the resolution of the device in the spectrum. The broad bands, and other causes too, lead to the absorption values on a wavelength frequently rising or falling together with the absorption values of the adjacent wavelengths. This phenomenon of multi co-linearity is dealt with hereinafter, as well as stray or scatter light correction. | |
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