Rewriting holograms

University of Arizona optical scientists have developed three-dimensional holographic displays that can be erased and rewritten in a matter of minutes.

The holographic displays are the first updatable three-dimensional displays with memory ever to be developed, making them ideal for medical, industrial and military applications.

'This is a new type of device, nothing like the tiny hologram of a dove on your credit card,' said UA optical sciences Prof Nasser Peyghambarian. 'The hologram on your credit card is printed permanently. You cannot erase the image and replace it with an entirely new three-dimensional picture.'

The device basically consists of a special plastic film sandwiched between two pieces of glass, each coated with a transparent electrode. The images are 'written' into the light-sensitive plastic, called a photorefractive polymer, using laser beams and an externally applied electric field.

The US Air Force Office of Scientific Research, which has funded Peyghambarian's team to develop updatable holographic displays, has used holographic displays in the past. But those displays have been static. They did not allow erasing and updating of the images. The new holographic display can show a new image every few minutes.

The 4" by 4" prototype display that Peyghambarian, Tay and their colleagues created now comes only in red, but the researchers believe much larger displays in full colour could be developed.

'We use highly efficient, low-cost recording materials capable of very large sizes, which is very important for life-size, realistic 3D displays,' Peyghambarian said.

The researchers also are working to write images even faster using pulsed lasers.

'If you can write faster with a pulsed laser, then you can write larger holograms in the same amount of time it now takes to write smaller ones,’ said UA optical scientist Savas Tay. 'We could, for example, display an image of a whole human that would be the same size as the actual person.'

In use, dynamic holograms could help surgeons track progress during lengthy and complex brain surgeries, show airline or fighter pilots any hazards within their entire surrounding airspace, or give emergency response teams nearly real-time views of fast-changing flood situations or traffic problems.

And no one yet knows where the advertising and entertainment industries will go with possible applications, Peyghambarian said. 'Imagine that when you walk into the supermarket or department store, you could see a large, dynamic, 3D product display,' he said.