Abstract: Back lighting for an transmissive display panel such as a transparency or a liquid crystal display for direct viewing or image projection is afforded by a light source spaced from the display panel and an intervening light coupler comprising a tapered duct with reflective inner walls such as a frustoconical mirror. The small end of the duct is adjacent the light source and may include a diffuser film to enhance light uniformity at the display. Light reflection from the reflective walls provides off-axis viewability with substantially uniform brightness. The light coupler is useful in a vehicular head up display.