Both Casper and myself are a bit of trekkies, we have to admit. So this study is a bit different than the typical research I discuss on this blog. But do forgive me, there is a relation with education: elementary mathematics brings Star Treks Holodeck closer to reality
From the press release:
For many years we have been hearing that holographic technology is one step closer to realizing Star Trek’s famous Holodeck, a virtual reality stage that simulates any object in 3D as if they are real. Sadly, 3D holographic projection has never been realized. A team of scientists from Bilkent University, Turkey, again raised our hopes on Holodeck realization by showing the first realistic 3D holograms that can be viewed from any angle. Dr. Ghaith Makey, the lead author of the paper appearing in the April 2019 issue of Nature Photonics today, says “Our technique can work in realtime, and will surely pave the way to dynamic 3D video holography. Soon, it may be possible to create a simple version of a Holodeck”.
3D holographic projection relies on back-to-back stacking of a large number of 2D images. The problem is, they cross-talk! Interference between the images makes the 3D projection fuzzy and far from realistic looking. The expectations have always been placed on the development of optical technology. Prof. F. Ömer Ilday, the co-leader of the project, disagrees: “The reason of this cross-talk is the mathematics, not shortcomings of the physical components. Any pair of high-dimensional mutually random vectors tend to be orthogonal. This basic result is a consequence of the Central Limit Theorem and the Law of Large Numbers. We use this property, together with a neat, but straightforward wavefront engineering trick to add random phase to each image, to eliminate cross-talk without using any additional optics”. Prof. Onur Tokel, the other co-leader, adds “It was not possible to simultaneously project a 3D object’s back, middle and front parts. We solve this issue through a simple connection between the equations developed by Jean-Baptiste Joseph Fourier and Augustin-Jean Fresnel in the early days of the field. Using this math property, we advance the state-of-the-art from the projection of 3-4 images to 1000 simultaneous projections!”
“The best part is that 3D projection performance will become better and better with increasing hologram resolution because the orthogonality result becomes exact for infinite dimensions — as display technologies continue to improve and support higher-resolution, they enable ever more realistic looking holograms using our technique,” says Dr. Makey. The team believes that the full potential of holography may be unleashed if such a 3D capability is at hand. “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, be they static or dynamic holograms. Therefore, opportunities are vast. Immediate applications may be in 3D displays for medical visualization or air traffic control, but also 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. This is even more clear with our new 3D projection capability. Many challenges remain, but we are one step closer to the visions defined by Holodeck in Star Trek; or Holovision of Isaac Asimov in the Foundation novels. Even Jules Verne touched upon the idea, in his book Carpathian Castle published in 1892,” adds Dr. Tokel.
Abstract of the paper, published in Nature photonics:
Holography is the most promising route to true-to-life three-dimensional (3D) projections, but the incorporation of complex images with full depth control remains elusive. Digitally synthesized holograms, which do not require real objects to create a hologram, offer the possibility of dynamic projection of 3D video. Despite extensive efforts aimed at 3D holographic projection, however, the available methods remain limited to creating images on a few planes, over a narrow depth of field or with low resolution. Truly 3D holography also requires full depth control and dynamic projection capabilities, which are hampered by high crosstalk. The fundamental difficulty is in storing all the information necessary to depict a complex 3D image in the 2D form of a hologram without letting projections at different depths contaminate each other. Here, we solve this problem by pre-shaping the wavefronts to locally reduce Fresnel diffraction to Fourier holography, which allows the inclusion of random phase for each depth without altering the image projection at that particular depth, but eliminates crosstalk due to the near-orthogonality of large-dimensional random vectors. We demonstrate Fresnel holograms that form on-axis with full depth control without any crosstalk, producing large-volume, high-density, dynamic 3D projections with 1,000 image planes simultaneously, improving the state of the art for the number of simultaneously created planes by two orders of magnitude. Although our proof-of-principle experiments use spatial light modulators, our solution is applicable to all types of holographic media.