Abstract: Disclosed is a method of obtaining a spectral image of each of a plurality of predetermined chemical species in a sample, comprising: (a) illuminating the sample with a first plurality of photons to produce a second plurality of photons; (b) collecting the second plurality of photons and producing a plurality of images of the sample therefrom, each of said images comprising a frame consisting essentially of a plurality of pixels; (c) for each of the predetermined chemical species, identifying at least one wavelength range at which the chemical specie exhibits a unique absorption of radiation; (d) identifying at least one wavelength range at which none of the predetermined chemical species exhibits an absorption of radiation; (e) in each of the image frames, identifying which of the pixels do not contain any of the predetermined chemical species; (f) in each of the image frames, identifying which of the pixels contain only a first the predetermined chemical species; (g) repeating the previous step for each of