Technophiles have dreamed of three-dimensional, holographic displays for decades, and in the last few years, a lot of progress has been made toward achieving that goal — from Microsoft’s Holoflector prototype to efforts at creating paper that was published in the journal Nature last week. He built a color holographic video display that’s as sharp as a standard-definition TV and updates images at the same rate.
If it works as Smalley and his team hope, then holographic televisions and communications (think FaceTime in 3D) could become a reality.
Ordinarily, to make a hologram, one uses a laser. A beam is fired at an object or a person you want to get a picture of. The beam is split, and one half illuminates the target. The illumination beam reflects off of the target and hits a photographic plate. Meanwhile the other half of the beam, which hasn’t hit anything, also hits the photographic plate.
The two beams will interfere with each other and create a ripple pattern on the plate. The ripples scatter any light that hits it in such a way that it reproduces the original image. Because the scattering, called diffraction, changes depending on the viewing angle, it creates an illusion of a 3D image.
Creating holographic video is hard because in order to get the same light-scattering effect, it’s necessary to control the light waves as they emerge from each pixel. In addition, the pixels in the image have to be close to the size of light waves, and there isn’t a video display technology that exists yet which can do that easily or cheaply.
To get around this, Smalley used a crystal of a material called lithium niobate. Just under the surface of the crystal are tiny channels that confine and guide the light that passes through them. Each channel, or waveguide, also contains a small electrode, which slightly distorts the shape of the crystal. It can do that because lithium niobate is piezoelectric, meaning that it changes shape when a current is run through it.
As the electrode alters the crystal’s shape, some wavelengths of light get filtered out and others will pass. That creates the scattering effect necessary for the 3D image.
Because it only needs one waveguide for each pixel, rather than three (one for each color) the cost is much reduced, and the use of relatively simple crystals brought the costs down even more. A single-pixel system also allows the images to refresh faster, and reduces the power consumption. Waveguides are also not a new technology in themselves; they are used in all kinds of electronics such as communications gear.
The images the team made with their first device refreshed at five frames per second and had dimensions of about 420 pixels by 420 pixels, with a depth of 156 pixels. The next hologram they hope to generate will be closer to a cube in shape and four times as large.
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This article originally published at Discovery News