Image from NatureVideo (Nature Communications)
Laser experts reported Tuesday that they've now succeeded in using an experimental camera to capture three-dimensional images of objects even when they're hidden around a corner.
Study lead author Andres Velten of the Morgridge Institute for Research in Madison, Wis., part of the MIT camera technology group that built the device, suggests the technology will initially see applications in high-cost military or search and rescue operation. "For consumer use, there is a lot of miniaturization ahead," Velten says. "It's not going to happen soon." But eventually, he says, "There's no reason why this shouldn't be on your iPhone someday."
First proposed by the study team two years ago, the prototype camera reported in the Nature Communications journal demonstrated the capture of three-dimensional images of an eight-inch mannequin and shorter letters, hidden around a corner. "Two years ago this was only dreams, now there is a real demonstration," says imaging expert Allard Mosk of the University of Twente in The Netherlands, in an e-mail. Says Mosk, who was not part of the study: "amazing research - the ability to reconstruct an image by a reflection of a reasonably flat, diffuse wall."
Here's how it works: The camera emits laser pulses in 50 "femtosecond" (quadrillionth of a second) pulses at various spots on the side-angled backing wall. The light pulses reflect off the obscured object and reflect back onto the wall. The camera collects these scattered reflections and feeds them into a computer, which knits them together like a jigsaw puzzle, creating a three-dimensional picture of the hidden object within 15 millionths of a second.
The result is a slightly blobby-looking but recognizable reconstructed object, its edges about one tenth-of-an-inch off from true measurements. "There is no new physics here - improvements are just a matter of laser, camera and computer technologies that are constantly improving," Velten says.
Mosk cautions that the prototype camera equipment today is still bulky and extremely expensive.
A kind of medical imaging called optical coherence tomography, which is used to peer tiny distances inside tumors or blood vessels, also relies on a related scheme of reconstructing light bounces to create images. Law enforcement researchers have also explored efforts to use radar guns to see through walls for hostage situations. "Ultra-fast computing is making a lot of things possible (that) we could only imagine before," Velten says.