Colorimeters with tri-stimuli filters

Two kinds of such colorimeters can be found:

• Colorimeters made of one single detector and a filter wheel. The latter comprises three filters, whose transmission spectra are equal to the colorimetric functions , and . By spinning the filter wheel, the three filters are then periodically set in front of the detector.

• Colorimeters made of three different photodetectors, working simultaneously, having spectral sensitivities equal to the colorimetric tristimulus functions.

In both cases, the trichromatic components of a sample are measured after calibration with a reference source whose spectrum is close to the spectrum of a normalized illuminant. These colorimeters are in general less accurate than those based on a monochromator (see below).