Researchers analyze performance of first updatable holographic 3D display

Researchers analyze performance of first updatable holographic 3D display
These digital camera images show holograms created with the photorefractive polymer in an updatable holographic 3D display. Image credit: Christenson, et al. ©2010 IEEE.

(PhysOrg.com) -- In 2008, researchers from the University of Arizona created a holographic 3D display that could write and erase images, making it the first updatable (or rewritable) holographic 3D display ever demonstrated. The key to the display was a photorefractive polymer material, which enabled the researchers to take advantage of the potential of holography to a greater extent than previously allowed. Now, in a follow-up study, the researchers have reported the results of their analysis on the performance of the display, including how the polymer enables display enhancements and what more needs to be done before such displays can be widely used.

As the researchers explain, there is a big jump between developing static holograms, such as those that appear on credit cards and drivers’ licenses, and updatable holograms. A variety of materials can be used to make full-color, large-size static holograms, but none of these materials are updatable. As the researchers’ previous study showed, photorefractive polymers have the potential to offer colorful images and large sizes in an updatable display. The display they demonstrated was, at 4 in. x 4 in., the largest yet created. It could display new images every 3 minutes, and images could be viewed for several hours without the need for refreshing. With these features, the display could serve as the basis for future displays that could offer a variety of glasses-free 3D applications in medical, industrial, military, and entertainment imaging.

“Photorefractive polymers are primarily beneficial because the method for achieving an index of refraction change is reversible and can be very fast, which is necessary for a real-world display,” coauthor Cory Christenson from the University of Arizona told PhysOrg.com. “Some materials currently used to make holograms are permanent and take hours to write. Additionally, the material permits making displays with large sizes (at least 4 in. x 4 in.), and in principle is scalable. Also, a single display device is stable for many months to a year or more before a noticeable drop in performance is observed. Photorefractive polymers are also attractive because modifying them with different polymers is relatively easy. If we want to test the effects of a different or new polymer to see if it helps increase speed or efficiency, it is not a significant challenge to make that composite.”

Holograms, like photographs, are recordings of reflected light. Here, the researchers created a hologram based on a 3D model of an object on a computer, and no real physical object was required. They then generated 2D perspectives of the object on the computer, which were processed and combined to create about 120 holographic pixels, or “hogels.” To create a single hogel, the researchers modulated a laser beam with that hogel, focused the beam on a thin vertical line, and made the beam interfere with a second, unmodulated laser beam. The entire hologram could be written by repeating this process with all 120 hogels and positioning them next to each other. After all hogels were written, the researchers could illuminate the sample with a simple LED to make the 3D hologram viewable. The sensation of 3D is created due to parallax: each eye is seeing a different perspective of the object.

Ideally, a should have a combination of a fast write-erase rate (required for video applications) and a high efficiency (required for bright images). Getting a high efficiency means adding traps for the charges generated, but traps also take time and slow down the write-erase rate, resulting in a tradeoff between these two features. In their study, the researchers tested two slightly different copolymers, each of which exceeded in one of the two areas.

“In looking at both the standard display material composition and one that was slightly different, we were able to study the effects of adding more sensitizer and traps (in the form of C60) to the material,” Christenson said. “The greatest significance of this is a more in-depth understanding of the physics that leads to the formation of the hologram. This understanding gives us a better idea of its potential for use in new applications and will guide future studies as we attempt to improve the material.”

The researchers determined that improvements could be made by mechanisms such as pulsed writing and reflection geometry, with the ultimate goal of creating realistic 3D holographic applications.

“The primary area for improvement is the sensitivity of the material,” Christenson said. “The media for permanent holograms is more sensitive to light than these photorefractive polymers, which permit better looking holograms. We are trying to find ways of decreasing the light needed to write a , which will make it much easier to expand into the areas mentioned in the paper, such as white-light viewing and writing at video rates.”


Explore further

Touchable Hologram Becomes Reality (w/ Video)

More information: -- Cory W. Christenson, et al. “Materials for an Updatable Holographic 3D Display.” Journal of Display Technology. To be published. Doi: 10.1109/JDT.2010.2046620
-- Savaş Tay, et al. “An updatable holographic three-dimensional display.” Nature 451, 694-698. Doi:10.1038/nature06596

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May 26, 2010
interesting. I think there are two holographic effects I understand, but don't really understand that well how they relate to each other. the first is the effect mentioned above, each eye seeing a different imagine resulting in perspective; understood. The second is, being able to move your head in any direrction and see a different ANGLE of the image.

So how does the seond really work and how is it related to the first? Holography isn't my field, but I still love it.

Thanks.

May 26, 2010
The problem with the types of holograms that we have seen in the movies such as the ones in Star Wars is that the images are being projected onto empty space which means the image needs to essentially reflected of nothing. I'm not sure if this new advancement takes care of this but I have seen another technology that most closely replicates the movie holograms. I'll post a link to a video that shows this technology in use during a live video conference. It's pretty impressive to say the least.

http://www.ndep.u...nference

May 26, 2010
The problem with the types of holograms that we have seen in the movies such as the ones in Star Wars is that the images are being projected onto empty space which means the image needs to essentially reflected of nothing. I'm not sure if this new advancement takes care of this but I have seen another technology that most closely replicates the movie holograms. I'll post a link to a video that shows this technology in use during a live video conference. It's pretty impressive to say the least.

http://www.ndep.u...nference


Seen it, not really like star wars. That one requires the space to be enclosed. I do think a true starwars hologram is possible, but probably 100 years away.

May 29, 2010
The second is, being able to move your head in any direrction and see a different ANGLE of the image.

So how does the seond really work and how is it related to the first? Holography isn't my field, but I still love it.

Thanks.


2nd method works by recreating lightwave reflected/scattered from the original object.

One method is to expose a photographic film to light reflected from the original object. You have to set up condition such that phase of scatterned light wave from the object is captured in the film. This done by intefering a light from the object and a reference beam of light. Then you take the film and shine light on it, and the light going throught film will be modified to 'recreate' wave from the original object.

Another way is to directly write 'phase' pattern in the film or any other optical media, as described in this article. The pattern can be computed from a computer model (largely matrix computation).

May 29, 2010
(Continued)

The reason 2nd method is not used is because technology doesn't yet exist to make it cheap. Because you are working with phase of lightwave, the resolution of the optical media has to be smaller than the wavelength of light (

May 31, 2010
Polymers used in holographic research have cost over $500 Million dollars to date and the bone yard is littered with polymer failures.

Holographic storage using polymers is unreliable, complex, and costly.

I think its time polymer films used in holographic storage should be put to rest.

Jun 01, 2010
(Continued)

The reason 2nd method is not used is because technology doesn't yet exist to make it cheap. Because you are working with phase of lightwave, the resolution of the optical media has to be smaller than the wavelength of light (


Thanks, understood.

Jun 04, 2010
Its nice but very much complicated

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