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Erasable Holograms Created

Photonics.com
Feb 2008
TUCSON, Ariz., Feb. 6, 2008 -- A special light-sensitive plastic film sandwiched between two pieces of glass coated with transparent electrodes can capture images when laser light and an external electric field are applied. Pictures taken from many 2-D perspectives are assembled into a 3-D picture by the holographic device and can be erased and rewritten within minutes.
3Dresearchers.jpg
The University of Arizona optical scientists who created erasable 3-D holograms are (l-r): Pierre Blanche, Nasser Peyghambarian and Savas Tay. They are standing in front of the 3-D display setup. (Images courtesy University of Arizona)
The holographic displays -- which are viewed without special eyewear -- are the first updatable 3-D displays with memory ever to be developed, making them ideal tools for medical, industrial and military applications that require "situational awareness," said the University of Arizona (UA) scientists who created them.

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

"Holography has been around for decades, but holographic displays are really one of the first practical applications of the technique," UA optical scientist Savas Tay said.
3Dimages.jpg
Actual images from the University of Arizona 3-D display. The top row shows a hologram of a skull being erased. In the middle and bottom rows, 3-D images are shown from different angles, demonstrating horizontal parallax.
Dynamic hologram displays could be made into devices that 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 or traffic problems, for example.

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

Tay, Peyghambarian, their colleagues from the UA College of Optical Sciences and collaborators from Nitto Denko Technical Corp., an Oceanside, Calif., subsidiary of Nitto Denko, Japan, report on the research in the Feb. 7 issue of the journal Nature.

Their device consists of a photorefractive polymer sandwiched between two pieces of glass, each coated with a transparent electrode. The images are "written" into the light-sensitive plastic using laser beams and an externally applied electric field. The scientists take pictures of an object or scene from many two-dimensional perspectives as they scan their object, and the holographic display assembles the perspectives from 2-D into a 3-D picture.
3DEthane.jpg
The holographic display showing a 3-D model of an ethane molecule.
The 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 were static, not erasable or updatable. The new holographic display can show a new image every few minutes.

The 4-in. by 4-in. prototype display that Peyghambarian, Tay and their colleagues created now comes only in red, but the researchers see no problem with developing much larger displays in full color. They next will make 1-ft by 1-ft displays, then 3-ft by 3-ft displays.

"We use highly efficient, low-cost recording materials capable of very large sizes, which is very important for life-size, realistic 3-D displays," Peyghambarian said. "We can record complete scenes or objects within three minutes and can store them for three hours."

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," Tay said. "We envision this to be a life-size hologram. We could, for example, display an image of a whole human that would be the same size as the actual person."
3DIllustration.jpg
Illustration of a future holographic 3-D display created from the University of Arizona research.
Holographic displays that can be updated have important applications in medicine, Tay said.

"Three-dimensional imaging techniques are already commonly used in medicine, for example, in MRI (magnetic resonance imaging) or CAT scan (computerized axial tomography) techniques," Tay said. "However, the huge amount of data that is created in three dimensions is still being displayed on two-dimensional devices, either on a computer screen or on a piece of paper. A great amount of data is lost by displaying it this way. So I think when we develop larger, full-color 3-D holograms, every hospital in the world will want one."

For more information, visit: www.arizona.edu 


GLOSSARY
hologram
An interference pattern that is recorded on a high-resolution plate, the two interfering beams formed by a coherent beam from a laser and light scattered by an object. If after processing, the plate is viewed correctly by monochromatic light, a three-dimensional image of the object is seen.  
optical
Pertaining to optics and the phenomena of light.
photonics
The technology of generating and harnessing light and other forms of radiant energy whose quantum unit is the photon. The science includes light emission, transmission, deflection, amplification and detection by optical components and instruments, lasers and other light sources, fiber optics, electro-optical instrumentation, related hardware and electronics, and sophisticated systems. The range of applications of photonics extends from energy generation to detection to communications and...
polymer
A material whose molecular structure consists of long chains made up by the repetition of many (usually thousands) of similar groups of atoms.
pulsed laser
A laser that emits energy in a series of short bursts or pulses and that remains inactive between each burst or pulse. The frequency of the pulses is termed the pulse-repetition frequency.
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