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Nitto Denko Technical Corporation (NDT), a U.S.-based R&D subsidiary of Japan's leading diversified materials company Nitto Denko Corporation (Nitto Denko), has successfully developed a novel, image-rewritable holographic display jointly with an American research team led by Prof. N. Peyghambarian of the University of Arizona, Nitto Denko announced today.
More specifically, in the joint effort, NDT succeeded for the first time in the world in developing a holographic display with an outstanding image persistence as well as image updating capability, by taking advantage of Nitto Denko's proprietary organic photorefractive material demonstrating both a diffraction efficiency at the world's highest level and a fast writing speed, says Nitto Denko. The company foresees applications for the holographic display in devices and apparatuses requiring three-dimensional visualization in the fields such as medical care, industrial operation and security assurance.
For the readers' information, the system setup as well as the basic scientific principles and other details of the latest development are presented in an article in the February 7 issue of the world-renowned scientific journal "Nature".
NDT has been engaged in the development of photorefractive materials from the viewpoint of developing novel, rewritable recording materials. The research company particularly focused on organic polymer-based materials which are inexpensive to produce and at the same time easy to coat on glass and plastic media. As a result, NDT succeeded in 2002 to come up with a photorefractive material and the associated system demonstrating an excellent compositional stability while at the same time exhibiting image strength at the highest level in the world as well as fast writing speed.
In the recent years, with the need for displays capable of creating dynamic holographic images continuing to expand further, various approaches to realizing such holographic imaging have been explored, but many technical issues still need to be overcome. Japan's Ministry of Internal Affairs and Communications has recently announced its plans to enter into a joint development program with the private sector to develop by 2025 a 3D-TV which would display images in three dimensions. With such a move expected to further accelerate the 3D imagery development efforts, novel materials and systems capable of continuously recording high-definition images are being awaited.
"Holograms" consist of three-dimensional images recorded on media such as film, and are used in applications such as "counterfeit-proofing" of credit cards and paper money. However, with customary holographic recording materials being non-rewritable, once the holograms have been recorded, they had the shortcoming of not allowing the re-creation of continuous dynamic images.
On the other hand, the photorefractive material and the system developed this time are superior by virtue of not only their rewritable characteristics but also the diffraction efficiency at the highest level in the world as well as the excellent compositional stability. At the same time, writing speed could be improved successfully by devising a special diffraction grating configuration.
2. Hologram Image Persistence and Rewritability
Unlike the photorefractive materials reported in the field to date, NDT made improvements in the chemical structure of the material and introduced special material layers, so that an image once recorded could be retained for a long time, while maintaining the high image strength and fast writing speed at the same time.
By so doing, the length of time over which recorded image could be retained until disappearance could be lengthened from the order of customary several seconds to several hours, so that recorded images can now be adequately viewed over a long period. Because the resulting image under the new system would form patterns which are subtly different by viewing from different angles, human eyes would perceive the patterns in total as three-dimensional images, as shown in Fig. 1 below.
3. Display Size
The size of the hologram display reported this time is larger than the customary size, at 15 cm x 10 cm, which is the largest reported for a photorefractive material-based sample. The large-area display could be created both homogeneously and defect-free by taking advantage of the polymer processing technology know-how which is one of Nitto Denko's technological strengths.
4. Application in 3D Display
Foreseeing various holographic applications for the photorefractive material developed this time in the fields such as image recognition, medical imaging and optical telecommunication, Nitto Denko plans to actively promote the development of various devices going forward.
Especially, the company expects that applications would extend to such items as rewritable three-dimensional maps, three-dimensional imaging of the surgery site in an operation, and 3D modeling for designing and fabricating vehicles and machinery in combination with the CAD/CAM technology. The ultimate target, Nitto Denko says, is the development of "3D-TVs" which would show images of objects as if they were real objects sitting right in front of the viewers' eyes.
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