A switch panel having a touch plate, light converter, and light analyzer
are disclosed. The touch plate includes an optically transparent layer
having first and second surfaces, and having an index of refraction
greater than that of air. The touch plate conducts light of an excitation
wavelength between the first and second surfaces and emits part of that
light through the second surface at one of a plurality of emission
locations depending on the position at which pressure is applied to the
first surface. The light converter is positioned to receive the light
emitted through the second surface and generates light having a plurality
of distinct location-specific spectra, one of the location-specific
spectra corresponding to each of the emission locations. The light
analyzer generates a signal indicative of which of the location-specific
spectra was generated by the light converter.