The image of Princess Leia, imploring “Help me, Obi-Wan Kenobi. You’re my only hope”, holds an iconic status in the history of motion pictures. The entire visual experience is evocative of watching an old fuzzy TV, but at the same time, it was, and still is futuristic. In the decades since, 3D holograms became the hallmark of science fiction movies and fantasy novels, perhaps most notably in the “Holodeck” of Star Trek series. The protagonists in such fictional works keep finding startling and exciting new ways of interacting with various holographic devices or even characters. However, this artistic aspiration is in stark contrast to what scientist have achieved so far, that is, after seven decades of research it is still impossible to create realistic 3D holograms.
Now, a team at Bilkent University, Turkey have devised a way to project holograms enabling complex 3D images. Their method is higlighted on the cover of the latest issue of Nature Photonics. “We achieve this feat by going to the fundamentals of holography, creating hundreds of image slices, which can later be used to re-synthesize the original complex scene”, says Dr. Ghaith Makey, the first author of the paper, from the Department of Physics and National Nanotechnology Center at Bilkent University.
“So far, it has not been possible to simultaneously project a fully 3D object, with its back, middle and front parts. Our approach solves this issue with a conceptual change in the way we prepare the holograms. We exploit a simple connection between the equations that define light propagation, the very same equations that are invented by Jean-Baptiste Joseph Fourier and Augustin-Jean Fresnel, in the early days of the field”, says Prof. Onur Tokel from the same department, and one of the lead authors of the paper. However, in order to reach their goal, the researchers had to introduce another critical ingredient. The 3D projection would suffer from interference between the constituent layers, which had to be efficiently suppressed. “Rarely a technological breakthrough can be directly traced to a fundamental mathematical result”, comments Prof. Fatih Ömer Ilday, from the same department and the other lead author of the paper. “Realistic 3D projections could not be formed before, mainly because it requires back-to-back projection of a very large number of 2D images to look realistic, with potential crosstalk between images. We use a corollary of the celebrated “central limit theorem” and “the law of large numbers” to successfully eliminate this fundamental limitation.”
“Our holograms already surpass all previous digitally synthesized 3D holograms in every quality metric. Our method is universally applicable to all types of holographic media. The immediate applications may be in 3D displays, medical visualization, air traffic control, but also in laser-material interactions and microscopy” says Prof. Serim Ilday of the Bilkent team. “The most important concept associated with holography has always been the third dimension. We believe future challenges will be exciting, considering the vision set by the Holodeck; or the Holovision of Isaac Asimov in the Foundation novels. Even Jules Verne touched upon this idea, in Carpathian Castle published in 1892. Clearly, the ensuing decades left us craving for more. We are closer to the goal of realistic 3D holograms”, adds Prof. Tokel.
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