It's the same thing used by Google Glass, and other head-up displays (like the ones built into airplanes and high-end cars). I believe it involves collimation: https://en.wikipedia.org/wiki/Collimated_light
For example, here's a description of the HUD currently available in several BMW cars:
"The image is projected in such a way that it appears to be about two metres away, above the tip of the bonnet, making it particularly comfortable to read. BMW Head-Up Display halves the time it takes for eyes to shift focus from road to the instruments and back."
For example, here's a description of the HUD currently available in several BMW cars:
http://www.bmw.com/com/en/insights/technology/technology_gui...
"The image is projected in such a way that it appears to be about two metres away, above the tip of the bonnet, making it particularly comfortable to read. BMW Head-Up Display halves the time it takes for eyes to shift focus from road to the instruments and back."