[m4x]

> The crystals act as antennaes that receive a photon emitted in the infrared, combine them with a photon from a laser and then "upconvert" the combined photon to the visible spectrum.

It doesn't sound like you need to illuminate the scene with a laser spotlight, it sounds like they will input a small amount of laser light into the crystal film on the glasses. The externally sourced IR photons will combine with the internally generated laser photons and emit a visible frequency photon.

The amount of laser energy pumped into the crystal film will probably be proportional to the amount of energy you want out of your "screen", i.e. brightness

[lolc]

Is there any chance that the "combined photon" will have the same direction as the original one? Otherwise there will be no image, just light.