MIT researchers develop new transparent display technology

MIT researchers have developed a new transparent display system that can have significant advantages over existing systems, at least for certain kinds of applications: a wider viewing angle, simplicity of manufacture, and potentially low cost and scalability.

A number of technologies have been developed for transparent displays, but all have limitations. 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 them. 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 colours, or light, while letting all the rest pass right through. That means the glass remains transparent enough to see colours and shapes clearly through it, while a single-colour display is clearly visible on the glass. To demonstrate the system, the research team projected a blue image in front of a scene containing cups of several colours, all of which can clearly be seen through the projected image.

While the team’s demonstration used silver nanoparticles - each about 60 nanometres across - that produce a blue image, they say it should be possible to create full-colour display images using the same technique. Three colours (red, green, and blue) are enough to produce what we perceive as full-colour, and each of the three colours would still show only a very narrow spectral band, allowing all other hues to pass through freely.

The system is described in a paper published this week in the journal Nature Communications, co-authored by MIT professors Marin Soljačić and John Joannopoulos, graduate student Chia Wei Hsu and four others.

Such displays might be used, for example, to project images onto store windows while still allowing passers-by to see clearly the merchandise on display inside, or to provide heads-up windshield displays for drivers or pilots, regardless of viewing angle.

Soljačić says that his group’s demonstration is just a proof of concept and that much work remains to optimise the performance of the system.

The work, which also included MIT graduate student Bo Zhen, recent PhD recipient Wenjun Qiu, MIT affiliate Ofer Shapira and Brendan Lacey of the US Army Edgewood Chemical Biological Center, was supported by the Army Research Office and the National Science Foundation.