MIT scientists have created a transparent screen using silver nanoparticles for an augmented reality display that places digital images over the real world.
Wearable HUD Google Glass is not an augmented reality device. Rather, it's a screen in your field of vision. The prism that overlays the world with interactive digital images is too thick and too small to cover your full field of view, as with a true augmented reality device.
In fact, producing such a device is proving difficult. Although devices are attempting it, such as Laster's SeeThru, the Vuzix M100 and the Meta Space Glasses, they all face similar screen size and thickness limitations.
A technology being developed by MIT might be the answer. A team led by physics PhD candidate Chia Wei Hsu has developed a new kind of transparent display based on the way nanoparticles of silver reflect laser light. Unlike other displays of its kind, it can offer a wide viewing angle and can be applied to quite a thin piece of glass.
In the experiment, the team mixed round silver nanoparticles with polyvinyl alcohol (PVA) and poured the mixture on to a flat piece of glass. The resulting transparent polymer film was just 0.46 millimetres thick. This formed the display.
The silver nanoparticles have very narrow optical resonances. This means that they scatter light at a very specific wavelength, and are transparent at all others. A very tightly focused laser tuned to the resonance of the silver reflects off the screen when projected, making it visible, while the rest of the screen remains transparent.
So far, the team has only tested the concept with nanoparticles sensitive to blue, but a screen containing nanoparticles sensitive to all three primary colours would return a full-colour display.
There is, alas, a very good reason why the screen won't make it to mass market quite just yet: the use of lasers means it's probably not entirely safe for customers to be putting a tiny projector next to their eyes, at least until further testing is conducted. However, the team suggests potential applications that could include a car wind shield or aircraft HUD, or even a regular window turned into an information display.
You can read the full paper, "Transparent displays enabled by resonant nanoparticle scattering", online in the journal Nature Communications.