Researchers at MIT’s Media Lab are reporting a new approach to generating holograms that could lead to color holographic-video displays that cost less to produce than existing monochromatic technology. Finally.
Daniel Smalley, a graduate student in the Media Lab, began by building a prototype color holographic-video display with a similar resolution to a standard-definition TV. This display could produce video images 30 times a second, which is deemed fast enough to produce the illusion of motion. All of this is thanks to an optical chip that he built himself for around $10.
When light strikes an object that has an irregular surface, it bounces off at a variety of angles. This means that different aspects of the object are shown when it’s viewed from different perspectives. In a hologram, a diffraction fringe bends the light so that it too emerges at different angles, creating a similar array of perspectives.
Smalley’s new technology was inspired by a previous Media Lab professor who created one of the very first holographic-video displays using a technique called acousto-optic modulation. With this method, a hologram was created by using precisely engineered sound waves that are sent through a piece of transparent material. The waves stretch and bend the material, sending the light in different directions. This rather-large display used a crystal that contained an expensive material, tellurium dioxide.
Instead, Smalley’s group used a smaller and less expensive crystal of lithium niobate. Just beneath the surface of the crystal, he created microscopic channels called waveguides which confine the light that travels through them. Onto these, he placed a metal electrode that produces an acoustic wave. Each waveguide corresponds to one row of pixels in the final image. Beams of red, green and blue light are sent down each channel and the frequencies of the acoustic wave passing through the crystal determine which colors pass through to the final image. This is also a more efficient way of displaying images than that used by an LCD TV.
“What’s most exciting is that it’s a waveguide-based platform, which is a major departure from every other type of spatial light modulator used for holographic video right now,” Smalley said.
Hopefully, this means that we’re not too far away from holographic television displays and even something like the holodeck from Star Trek.