摘要 |
A display unit for a head up display wherein the combiner (11), which serves to reflect light from a display surface (14) towards an observer to provide the observer with an image of the display superimposed on his view through the combiner, comprises first and second tuned reflective coatings (25c and 27c) disposed in such angular relationship with one another and the display surface that narrow waveband light from the display surface reaches the observer after being successively transmitted through the first coating, reflected at the second coating, reflected at the first coating and transmitted through the second coating.
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