Fig 1. The effect of illumination power on absorbance and reflectance spectra.
Raw spectra of 0.05 g/mL nigrosin dye (a) and the background halogen light source (b, ω = 1) were measured. To simulate the effects of the low and high illumination power, weighting factors (ω = 0.8 and 1.2) were multiplied with the background spectrum. (c, d) Reflectance and absorbance were obtained for the three different weighting factors. Illumination power can be observed to change the scaling of reflectance spectra and the offset of absorbance spectra. (e, f) The proposed background retrieval method estimates the optical spectral power of the illumination at the sample by exploiting a normalised spectral profile of the light source (e) and the intensity ratio between the normalised spectral profile of the light source and sample data (Cs/Cb) at a wavelength displaying low absorbance in the sample of interest, here selected as 800 nm (f).