US Patent 11863912 Lighting unit and display with wavelength-selective illumination

A display device may include a projector coupled to volume Bragg grating (VBG) based pupil-replicating lightguide. The projector may be a scanning projector or a display panel based projector. A lighting unit for the display panel may have spatially variant spectral composition selected to match angular and wavelength selectivity of the VBGs of the pupil-replicating lightguide, thereby improving light utilization efficiency of the display device. In scanning projector implementations, the center wavelength of the scanned light beam may be varied in coordination with the scanning, to achieve the same effect.