For a hologram consisting of a single color, only one diffraction pattern is calculated, Bove says, but to create a full-color image, three different patterns need to be created, one for each of the additive primary colors: red, blue, and green. The computation consists of rendering a three-dimensional model, generating the diffraction patterns, and producing a video signal, all of which can be done using off-the-shelf hardware.
Then, Bove says, the holographic video signal is sent into a light modulator, which consists of a waveguide–made of a material called lithium niobate–where light travels, covered by a piezoelectric material that converts the video signal into vibrations. The video signal changes the shape of the piezoelectric material, which changes the properties of the light moving through the waveguide. The emitted light wave is thus composed of various intensities and frequencies that, when projected onto a foggy piece of glass, recreate a three-dimensional scene. Because this novel modulator can emit light in the vertical direction as well as in the horizontal direction, it can also help eliminate some mirrors and lenses that made previous generations of displays bulky.
While the project is in its final stages of completion, it has the potential to help make holographic video more accessible. “I’m entranced by the possibilities that [the researchers] show,” says Harold Garner, professor of biochemistry and internal medicine at the University of Texas Southwestern Medical Center at Dallas. Garner has developed a holographic system for looking specifically at medical images such as MRIs. “I really look forward to a real device demonstration.”
While his expertise is in holographic images for medicine, Garner believes that people will start to demand more than just high-definition displays from their televisions and computer monitors, and will eventually want three-dimensional videos as well. “It’s only a matter of time,” he says. But what makes it challenging, Garner adds, is that consumers demand bigger and brighter images, and researchers are a long way from delivering 60-inch, high-definition holograms. Because of consumer tastes, “you may have to pick and choose” the commercial applications for this technology, Garner says.
Bove and his team currently have a fourth generation of system lined up, which will be able to display an image as large as a desktop PC monitor; in contrast, the current system’s displays are only about the size of a Rubik’s Cube. Also, the current display is only capable of monochromatic holograms, but the fourth generation will have a full range of colors, Bove says.