Transparent displays have a variety of potential applications - such as the ability to see navigation or dashboard information while looking through the windshield of a car or plane, or to project video onto a window or a pair of eyeglasses. A number of technologies have been developed for such displays, but all have limitations.
Now, researchers at MIT have come up with a new approach that can have significant advantages over existing systems, at least for certain kinds of applications: a wide viewing angle, simplicity of manufacture, and potentially low cost and scalability.
The innovative system is described in a paper published this week in the journal Nature Communications, co-authored by MIT professors Marin Soljacic and John Joannopoulos, graduate student Chia Wei Hsu, and four others.
Many current "heads-up" display systems use a mirror or beam-splitter to project an image directly into the user's eyes, making it appear that the display is hovering in space somewhere in front of him. But such systems are extremely limited in their angle of view: The eyes must be in exactly the right position in order to see the image at all. With the new system, the image appears on the glass itself, and can be seen from a wide array of angles.
Other transparent displays use electronics directly integrated into the glass: organic light-emitting diodes for the display, and transparent electronics to control them. But such systems are complex and expensive, and their transparency is limited.
The secret to the new system: Nanoparticles are embedded in the transparent material. These tiny particles can be tuned to scatter only certain wavelengths, or colors, or light, while letting all the rest pass right through. That means the glass remains transparent enough to see colors and shapes clearly through it, while a single-color display is clearly visible on the glass.
To demonstrate the system, the team projected a blue image in front of a scene containing cups of several colors, all of which can clearly be seen through the projected image.