Tensor Display – a step closer to glasses-free 3-D TV
Holograms – most of us want them in our homes, but we still can’t have them. As an alternative and more feasible solution, MIT Media Lab’s Camera Culture group devised a multiple-perspective, glasses-free 3D display technology they named Tensor Display. Instead of the complex hardware required to produce holograms, the system developed by the Media Lab uses several layers of liquid-crystal displays (LCDs) which refresh at high rate.
A year ago we reported about HR3D technology developed by Media Lab, and it involved combination of two layers of LCD displays. In order to produce convincing 3D illusions with this system, it would require usage of displays with a 1,000-hertz refresh rate. To get the refresh rate down to currently more feasible 360 hertz, the Tensor Display adds another LCD screen, which displays yet another pattern.
Adding another display adds more computing requirements that make the problem of calculating the patterns exponentially more complex, however, the researchers exploited the fact that some aspects of a scene do not change with the viewing angle in order to reduce the amount of processed information. This natural redundancy enables the pattern-calculating algorithms to create more seamless animations and thus improve the quality of the final image.
The math behind the Tensor Display can be compared to X-ray technique used to produce 3D images of internal organs named computed tomography (CT). For those not familiar with how CT scanning works, a sensor slowly moves along or around the subject and makes a series of measurements of X-rays passing through the subject’s body. These reading are combined into a composite 3D image of the subject.
Aside Tensor Displays, the group also developed another prototype that uses only two panels with a sheet of lenses that refract light left and right. The lenses were originally developed for stereoscopic display systems actually developed for stereoscopic display systems. Although this display is able to project different patterns for each eye, the main purpose of this sheet of lenses is to widen the viewing angle of the display.
While the three-panel version of the 3D display is better than HR3D technology, the 3D illusion is consistent within a small viewing angle of 20 degrees. However, the usage of refractive-lens version widens the viewing angle to 50 degrees, and eventual combination and advancement of these two technologies could lead to smoother animation with larger viewing angles.
For more information, you can read the paper featured as a research highlight at this summer’s Siggraph computer-graphics conference: “Tensor Displays: Compressive Light Field Synthesis using Multilayer Displays with Directional Backlighting” [16MB PDF].
“The paper reveals how you would greatly improve the realism, and image depth, and physical simplicity of 3D display systems, particularly those that don’t require you to wear glasses”, said Gregg Favalora, a principal at the engineering consultancy Optics for Hire and co-chair of the SPIE Stereoscopic Displays and Applications Conference. “It’s only possible when you have these really good mathematicians and signal-processing guys and optics experts all sitting in the same room.”
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