Full-colour holograms can be viewed with ordinary white light

Projecting images is typically an inefficient process. When white light shines on an object, we see only the reflected colour that reaches our eyes, while the rest of the spectrum – 95 per cent for an LCD screen – is absorbed, wasting light.

Inspired by the principle behind how some butterflies’ wings display their vivid colours, a team of engineers from the University of Utah set about finding a more efficient way to project images.

Rather than just reflecting select colours, all the light falling on the wings is redirected so the wavelengths of the wing colours can be seen at different locations. This means that none of the light is absorbed and wasted.

“You can have rich colours at high efficiency, with high brightness and at low cost. And you don’t need fancy lasers and complicated optics,” said Professor Rajesh Menon.

Using a new fabrication method and algorithms, the engineers were able to create holograms that also redirect colours to the right locations in order to create bright images in 2D or 3D with full, natural colours.

Currently, full-colour holograms require lasers to be viewed, while Prof Menon’s holograms can be viewed with regular white light. Perhaps more significantly, they can be viewed from any angle without the details of the image changing.

“Projecting an image before was very inefficient, and you need a massive lamp,” said Prof Menon. “Here, you can do it with just a piece of plastic and a flashlight. It’s much simpler and more efficient this way.”

This technology could be used in security holograms – such as on currency, identification badges and passports – in which a simple torch could be used to authenticate these documents rather than an expensive laser scanner. Although Prof Menon and his colleagues have so far only produced still 2D images, they believe that it would not be difficult to create similarly vivid and detailed 3D moving images within two years – these could be used in virtual-reality headsets, 3D films and high-tech amusement rides.

“Imagine going through a ride and you want a monster to jump out. This is a way to do that with much richer colour with higher efficiency and in a much more ubiquitous manner because it’s so cheap,” said Prof Menon.