Imagine having a long-distance conversation with a colleague who, to your eyes and ears, appears to be right in front you. Now, 3-D telepresence has moved closer to reality, thanks to research by the University of Arizona and supported by the National Science Foundation.
The system they are working on features a holographic video display that refreshes every two seconds. That two-second refresh rate represents a huge step up from where the technology was a couple of years ago, when the display refreshed once every four minutes.
A three-dimensional image of a moving person or object, with 360-degree viewing capability, projected from afar in something approximating real time, could represent a major breakthrough in communications technology. Unlike depictions of holograms in popular science-fiction movies, however, the images are not projected into empty space but onto a transparent sheet of plastic—a key part of the process.
“The heart of the system is a new plastic material that we have come up with which we call … a photorefractive polymer,” says Nasser Peyghambarian, project leader and chair of photonics and lasers at the University of Arizona. Peyghambarian is also the director of the National Science Foundation’s Engineering Research Center for Integrated Access Networks.
As new images are “written” on the polymer screens, old ones are erased. The material is also able to store the projected images, and, unlike face-to-face conversations, there is a pause button. Viewers can circle the projection and view it practically in its entirety, which results in a more realistic simulation.
The process begins with 16 computer-controlled cameras arranged in a semicircle around the person or object, taking two-dimensional pictures from different angles simultaneously. “The 16 views are processed into hogel data by the host computer and sent to the holographic recording controller through an Ethernet link,” Peyghambarian explains. Hogel is a nickname for holographic pixel; hogels are the 3-D version of pixels.
When the recording has been sent, a pulsed laser inscribes the images into the polymer screen. “Once a hologram has been written, the system uses the next available hogels to update the information. The hologram is displayed using a color LED that gets scattered off the image to the viewer’s eyes,” Peyghambarian adds. This optical effect renders the 3-D image perceptible to the naked eye, no special glasses required.
The designers’ main goal is to achieve full-motion video rate—30 frames per second. They point out that other improvements need to be made as well before commercializing the technology. For instance, the color palette is very limited right now (although it is worth noting that adding color into the process doesn’t slow down the refresh rate at all). Size also presents a challenge—the maximum projection size is currently 17 inches, but the design goal is to increase that to encompass at least the average size of a person. The resolution of the projection and sensitivity of the materials need improvement as well, and the research team is working on ensuring that the optics can competently handle indoor low-light settings.
Many other important uses for the technology exist besides holding long-distance business meetings, say the researchers. These uses include digital design and engineering, and telemedicine for complex surgical procedures. Such a telepresence system would also improve 3-D printing capabilities, better enable 3-D mapping, and enhance entertainment experiences.
Affordable large-scale holographic projections may still be a long way off; however, they are moving closer to becoming a reality.—Aaron M. Cohen
Sources: The National Science Foundation, www.nsf.gov.
Nasser Peyghambarian, University of Arizona (email interview).