by Klaas Robers » Fri Apr 19, 2013 6:15 pm
I think that is not too difficult. If you remember how the spectrometer works, with the moving grating or prism, and the detector, if you use a halogen incandescent lamp, then you might calibrate the system by measuring the light of the lamp without any sample in the aparatus. Then you know the spectrum of the lamp itself.
Incandescent lamps have a continuous spectrum, because it is a thermal radiator, just like the sun. A hot body. Only the emitted amount of power is not equal in all wavelengths, this is because of the limited temperature. The higher the temperature, the more short wavelength (blue) power in the spectrum. But it remains continuous, no spectrum lines.
Then when you insert a sample you measure the attenuation of that sample as a function of the wavelength, so the damping of the known / calibrated light spectrum.
If you really need a "paint" that matches with the original paint under all circumstances, then this is the only way. All systems with three filters, red green and blue, and three detectors, give though R G B values, but if you change the light source, you don't know what happens with the colour. And even worse, if you have two colours that match in R, G and B of the "meter", then still you, ore somebody else, might see a difference. No two people see the same colours, as also our eyes work with R, G and B sensitive sensors, but the curves differ from person to person.
Sometimes the R and G sensors have the same, or almost the same sensitivity curve, and then that person sees no difference between red and green.