A method for measuring a sample to identify a chemical includes receiving respective spectra for each of a plurality of chemicals. Using a processor, a plurality of binary mathematical filters are computed using the received spectra. A spatial light modulator is adjusted according to a selected mathematical filter. Light that has interacted with the sample is dispersed over the surface of the spatial light modulator, so that the spatial light modulator provides light at wavelengths corresponding to the selected mathematical filter. The light provided by the spatial light modulator is measured to provide a score corresponding to the selected mathematical filter. Filter scores are combined to determine a chemical amount. The processor can operate detection apparatus having a light source, an objective for focusing source light onto the sample, a spatial light modulator, and a detector for detecting the modulator output.