Patent ID: 7920226

Claim:
A backlight comprising: a waveguide; and a structure overlying the waveguide, selected regions of the structure having birefringent properties whereby the interface between the waveguide and the selected regions of the structure is not totally internally reflective for at least one polarization of light propagating within the waveguide, wherein a plurality of birefringent protrusions are disposed on the first face of the waveguide of the backlight, each protrusion having a refractive index that, for light of a first polarization, is not lower than the refractive index of the waveguide whereby the protrusion is not totally internally reflective for light of the first polarization propagating within the waveguide, and wherein each protrusion has a refractive index, for light of a second polarization different from the first polarization, that is lower than the refractive index, for the second polarization, of the waveguide whereby the protrusion is totally internally reflective for light of the second polarization propagating within the waveguide.