LETTER doi:10.1038/nature09521 Holographic three-dimensional telepresence using large-area photorefractive polymer P.-A. Blanche 1 , A. Bablumian 1 , R. Voorakaranam 1 , C. Christenson 1 , W. Lin 2 , T. Gu 2 , D. Flores 2 , P. Wang 2 , W.-Y. Hsieh 2 , M. Kathaperumal 2 , B. Rachwal 2 , O. Siddiqui 2 , J. Thomas 1 , R. A. Norwood 1 , M. Yamamoto 2 & N. Peyghambarian 1 Holography is a technique that is used to display objects or scenes in three dimensions. Such three-dimensional (3D) images, or holo- grams, can be seen with the unassisted eye and are very similar to how humans see the actual environment surrounding them. The concept of 3D telepresence, a real-time dynamic hologram depicting a scene occurring in a different location, has attracted considerable public interest since it was depicted in the original Star Wars film in 1977. However, the lack of sufficient computational power to pro- duce realistic computer-generated holograms 1 and the absence of large-area and dynamically updatable holographic recording media 2 have prevented realization of the concept. Here we use a holographic stereographic technique 3 and a photorefractive polymer material as the recording medium 4 to demonstrate a holographic display that can refresh images every two seconds. A 50Hz nanosecond pulsed laser is used to write the holographic pixels 5 . Multicoloured holo- graphic 3D images are produced by using angular multiplexing, and the full parallax display employs spatial multiplexing. 3D telepresence is demonstrated by taking multiple images from one location and transmitting the information via Ethernet to another location where the hologram is printed with the quasi-real-time dynamic 3D display. Further improvements could bring applica- tions in telemedicine, prototyping, advertising, updatable 3D maps and entertainment. 3D display technology is attracting much public attention; events include the recent release of 3D films such as Avatar, the 2008 US election-night ‘hologram’ reporter interviews from CNN (http:// www.cnn.com/2008/TECH/11/06/hologram.yellin/index.html), and the demonstration of 3D televisions by some manufacturers (http:// www.3dtvsource.com/). As dramatic as these effects are, the techno- logy used is based on polarization stereoscopy (the technique currently used in cinemas and television), digital image fusion (in the case of CNN), or 2D semitransparent screens (for musion; http://www. musion.co.uk/). As such, they have little to do with holography, which is the reproduction of the amplitude and phase of light by diffraction 6 . Nevertheless, these examples show the great enthusiasm that the public, media and industry share about 3D image rendering, and for a good reason: the human physiology has adapted to observe its envi- ronment in three dimensions. Holography, with its ability to reconstitute both the intensity and wave front information of a scene, allows the observer to perceive the light as it would have been scattered by the real object itself 7 . Furthermore, there is no need for any special eyewear to be worn by the observer. It has been shown that holograms can be computer generated 8 . Unfortunately, the amount of information needed to produce a high quality hologram is so large that making a real-time video-rate display has been limited by either size or resolution 9–11 . To overcome those major issues, different solutions have been tested, such as pupil tracking 12 , the use of a holographic diffuser screen 13,14 or the synthesis of a hologram from real objects 15 . It has also been shown that the holographic stereographic technique 16 (also referred to as integral holography), using the diffraction of light to reproduce both parallax and occlusion clues (but not reproducing the phase), can be used to ease data management. Compared to normal stereograms or ana- glyphs, holographic stereography does not require the viewer to use eyewear to perceive the 3D effect. The technique reconstitutes multiple perspectives that the observer can experience by looking at the screen from different angles. Applied to permanent holographic media such as silver halide films or photopolymers, holographic stereography is capable of providing excellent resolution and depth reproduction on large-scale 3D static images (http://www.zebraimaging.com): but dynamic updating capability has been missing until now. Photorefractive inorganic crystals have been used in the past to dem- onstrate refreshable holographic displays 17,18 . However, such systems suffer from the disadvantage that crystalline materials are not scalable in size owing to their laborious growth process, and thus are not well suited for display applications. Our group has introduced an updatable holo- graphic 3D display based on the holographic stereographic technique using photorefractive polymeric materials 19 . Although this was an important step towards dynamic holography, the system had several limitations, including being monochromatic and having a low refresh rate (more than 4min per image) 20,21 ; the rapid updating needed for video rates or 3D telepresence was not possible. Here we describe a new holographic 3D display based on a novel photorefractive material capable of refreshing images every two seconds, making it the first to achieve a speed that can be described as quasi-real- time. The system is based on a pulsed laser holographic recording system and a new sensitized photorefractive polymer with remarkable holo- graphic properties. Each holographic pixel, known as a ‘hogel’ 5 , is written with a single nanosecond laser pulse. As opposed to 2D pixels, hogels contain 3D information from various perspectives. We also demonstrate multi-colour capability using angular multiplexing and 1 College of Optical Sciences, The University of Arizona, Tucson, Arizona 85721, USA. 2 Nitto Denko Technical Corporation, Oceanside, California 92054, USA. 1.0 0.8 0.6 0.4 0.2 0.0 0 50 100 150 Time (s) 200 250 300 Diffraction efficiency (%) Figure 1 | Example of diffraction efficiency dynamics under single nanosecond pulse writing. The pulsed energy at the sample location was 650 mJ cm 22 (sum of both beams). Applied voltage to the photorefractive device was 7 kV and kept constant during the whole measurement. 80 | NATURE | VOL 468 | 4 NOVEMBER 2010 Macmillan Publishers Limited. 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