disclosed here is an efficient flat light source based on uv light excited photoluminescence of phosphors . an electrical discharge is confined to be substantially planar by a glass enclosure . this electrical discharge produces ultraviolet photons . these uv photons in turn excite phosphors to produce visible light with great efficiency and high intensity . in this invention , light is taken out of the light source from one side only . a uv light recycling means is also provided . means for collimation of this light source is disclosed for projection display applications . polarization conversion means is also described for such flat light sources , so that the light output is almost totally linearly polarized .