Additive colour mixing by surface relief gratings utilizing the power spectrum of a fluorescent lamp

Additive colour mixing produced by diffractive grating structures is studied. The gratings produce almost monochromatic primary colours to a selected viewing angle, providing thus a very large colour gamut. The colours inside the gamut are obtained by additive colour mixing in the reflected diffraction order. The amount of a single primary in the additive colour mixing within one colour pixel is determined by the area fraction of the corresponding grating. We demonstrated the concept by fabricating samples which appear white at 30° viewing angle when illuminated by 4000 K fluorescent lamp.