Practical Holographic Video

Practical holography: The modulator converts a video signal (from the black cable at the bottom) into a vibration. When laser light is passed through the modulator, the vibrations modify the brightness and frequency of the light. The altered light is then shined on a screen, and the varying intensities and frequencies create a three-dimensional hologram.
Daniel Smalley

Computing

Researchers have designed a cheap and small holography system that will work with PCs and gaming consoles.

Tuesday, April 24, 2007
By Kate Greene

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The tyranny of two-dimensional computer and TV displays could soon be over. A team of MIT researchers has proposed a way to make a holographic video system that works with computer hardware for consumers, such as PCs with graphics cards and gaming consoles. The display, the researchers say, will be small enough to add to an entertainment center, provide resolution as good as a standard analog television, and cost only a couple hundred dollars.

A holographic video display could provide another way to view medical images such as MRIs and CT scans, as well as sets of complex, multidimensional data and designs for furniture and cars, says V. Michael Bove Jr., director of the consumer electronics program, CELab, at MIT. And the system would be a natural fit for displaying video games and virtual worlds. Most games now have sophisticated three-dimensional models sitting deep within their software, "but you don't see them because [the images are] rendered as a two-dimensional picture," Bove says.

The new system, called Mark III, is the third generation (following Mark I and Mark II) of MIT-designed holographic video displays that date back to the late 1980s. These earlier systems were "loud, finicky, required specialized computing hardware to generate a video signal, and were a general pain in the neck to work with," says Bove. A few years ago, he wondered if he could turn a laboratory-based holographic display system that cost tens of thousands of dollars into an affordable consumer product.

Thus, Bove and his team have developed Mark III--expected to be completed within a couple of months--which is based on the earlier systems but has three major differences. First, explains Bove, the new system processes three-dimensional images on a standard graphics processor rather than on specialized hardware. It turns out, he says, that the graphics cards that are found in high-end PCs and gaming consoles are a good fit for the type of image processing required to create a hologram. Second, his team has redesigned a gadget called an acousto-optic modulator, commonly found in telecommunications systems, to direct light from lasers to form the hologram. The new modulator has a higher bandwidth, which makes for a high-resolution hologram, and is less expensive than the ones used in Mark II. Third, the researchers have eliminated some of the clunky optical components that made the Marks I and II as large as a dining-room table.

To create a holographic video, Bove says, software produces a real-time, three-dimensional model of the objects within a scene. So, for an MRI of a beating heart, the software uses a collection of numbers that describe the position of all points on the surface of the heart, in all three dimensions. With such a model in place, software calculates how lasers need to project the light to create a hologram. In essence, the software creates a blueprint for the lasers to follow that consists of the basis of all holograms: a diffraction pattern, which occurs when light waves interfere with one another.

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