shows the luminescence emission spectrum of the laminated sensor material after excitation with a 405 nm LED showing a temperature independent emission at 450–525 nm due to the optical brightener in the paper matrix and a temperature dependent emission of the ..... at 525–725 nm. Obviously, the inertluminescence of the paper brightener lends itself as an internalreference for the temperature dependent emission of rutheniumcomplex. When using a RGB color camera combined with an UVexcitation source, ratiometric temperature imaging is possible withdetection of the brightener luminescence in the blue channel andthe temperature sensitive Ru(phen)3emission in the red channelof the camera chip, respectively