Skip to main content
Part of complete coverage on

A camera that can see around corners

By Ramesh Raskar, Special to CNN
August 19, 2012 -- Updated 1305 GMT (2105 HKT)
STORY HIGHLIGHTS
  • Ramesh Raskar's team at the MIT Media Lab is re-imagining what photography can do
  • By creating movies of light in motion at a trillion frames per second, camera can see around corner
  • Raskar: Technology is years away from applications in the real world
  • He says it could be helpful in preventing car crashes and aiding rescues

Editor's note: Ramesh Raskar is Associate Professor at MIT Media Lab and head of the Camera Culture research group. He is an Alfred P. Sloan Research Fellow (2009), a recipient of the DARPA Young Faculty award, the co-author of "Spatial Augmented Reality", and the holder of more than 50 US patents. He spoke at the TEDGlobal conference in June. TED is a nonprofit dedicated to "Ideas worth spreading" which it makes available through talks posted on its website.

(CNN) -- A camera that can see around a corner?

I know this sounds like something in a sci-fi movie or a superhero comic, but this is a real-world technology we've made possible with a camera that is aware of the travel time of light, an imaging technique that can create movies of light in motion with an effective rate approaching a trillion frames per second: the speed of light.

Before I joined the MIT faculty in 2008, I had done deep research in "computational photography," a field of new imaging techniques dramatically improving the capture and synthesis of photos. But, I knew there was more to photography than just depicting what the eye can see. I wanted to create a camera that could see beyond the line of sight. The speed of light isn't infinite: light travels about a foot per billionth of a second.

Photography could make X-rays obsolete

If I could build a camera fast enough to analyze light at high speeds in room-sized environments, I knew we could then create cameras to solve major problems in scientific and consumer imaging, and enable completely new functionality.

I spoke to top researchers in ultrafast lasers and photonics to understand what was currently possible. When I did, most of them asked some version of: "Why? Why spend years building a camera to look around corners when no commercial application is screaming for it and no funding agency has a call for it?" In addition, it's rare to shoot light pulses and analyze at such high speeds in large environments. Ultra-fast imaging experiments are usually limited to centimeter- or smaller-size samples.

I continued the work and in the spring of 2008, with James Davis from UC Santa Cruz, wrote a proposal that laid out the mathematical foundation and various experimental solutions for exploration.

TED.com: Boaz Almog 'levitates' a superconductor

I also began working with Media Lab graduate student Matthew Hirsch to build a prototype, hoping that we would have something to demonstrate within a few months. The grant proposal was rejected for administrative reasons (I made a paperwork error!), which meant we had to wait nearly a year to apply again. But those two years didn't yield any meaningful results, as our lab components weren't designed to be used the way we wanted.

After nearly three years of experimental work, the team -- especially postdoctoral associate Andreas Velten and MIT professor Moungi Bawendi, many students, and several collaborators -- cobbled together pieces of the puzzle and built a software program to create a first demonstration of looking around corners. Very soon afterward, we could also start creating surreal movies of light in motion.

We call this new imaging technology femto photography because we capture a segment of the image with a flashlight (in this case, a laser pulse) on for a few millionths of a billionth of a second (or a few femtoseconds) and an exposure time approaching a trillionth of a second.

Just how fast is femto photography? Think of it this way: if we took one-thousandth of a second of footage from the femto camera video output and slowed it down to the speed of 30 seconds per frame -- the approximate speed of a standard TV broadcast -- it would take us a lifetime to watch.

Photographers know that at very short exposures and even at the most sensitive setting for dark scenes, we will record barely any light. So what about in a trillionth of a second? We actually record and average millions of photos to get enough light, each photo made to look the same via carefully timed synchronization with the light pulse. So even if our exposure time is indeed nearly a trillionth of a second, to get sufficient light we must take an average. Thus, as of now, we can only record repeatable events, but this is not a fundamental limitation.

TED.com: A robot that flies like a bird

Unlike conventional cameras, our femto camera captures an image as one thin slice at a time of one-dimensional space using a "streak tube," a laboratory instrument that is commonly used by chemists to study light passing through chemical samples. We then take hundreds of these narrow videos (each shot at a slightly different angle) and create a carefully synchronized, slow-motion composite of the light pulses. It takes about an hour to collect and aggregate the data (view a demonstration of a light pulse as it travels through an ordinary Coca-Cola bottle).

To see around the corner, we use femto photography to analyze scattered light. We bounce light off of visible parts into hidden parts and then measure the time and direction of returned light.

Usually the scattering of energy is considered a nuisance -- whether driving in fog or poor reception from a cell phone tower -- and most techniques either try to avoid it (by turning on fog lights) or reduce the impact of scattering (by selecting energy for the phone only from direct paths).

In contrast, we exploit the scattering. For the camera, a laser pulse is fired at a wall, and the impact of hitting the wall causes the particles of light to scatter. Some of the scattering particles return to the camera at different times. This is repeated about 60 times per image as the camera measures how long it takes for the light to travel back and where the particles land. An algorithm then crunches the data to reconstruct the hidden image. This technique even allows us to see a three-dimensional object such as a mock-up of running person.

TED.com: Test for Parkinson's with a phone call

As exciting as this work is, don't look for this technology to be in practice tomorrow -- we're still years away from bringing this to market. But, we can already imagine multiple ways that it could have a significant, positive impact on our everyday lives.

By allowing us to "see" around a corner, for example, this technology added to our cars could let us know if there's another vehicle approaching around a blind curve. It also could give us a new way to look deep inside our bodies without X-rays, or to look through a window into a burning building from a distance to see if anyone is left inside --without risking a firefighter's life.

When I gave a TEDGlobal talk on femto photography in June, I began with a reference to Doc Edgerton, a very popular MIT professor of electrical engineering who, in 1964, wowed the world with an image of a bullet in midair, having just passed through an apple. He accomplished this by using a strobe light to freeze the action of the bullet at a millionth of a second.

What we're talking about here -- the speed of light --is a million times faster, and is opening the door to a complete rethinking of what we mean by, and can do with, photography. It is a first step toward a new world of imaging that far exceeds human ability, resynthesizing data and depicting it in ways that are within human comprehensibility.

Follow @CNNOpinion on Twitter

Join us at Facebook/CNNOpinion

The opinions expressed in this commentary are solely those of the author, Ramesh Raskar, who would like to thank his collaborators: Moungi G. Bawendi, Professor, MIT Department of Chemistry; Andreas Velten and Christopher Barsi, postdoctoral associates, MIT Media Lab; Everett Lawson, Otkrist Gupta, Nikhil Naik, Amy Fritz, Di Wu, MIT Media Lab; Matt O'toole, Kyros Kutulakos, University of Toronto; Diego Gutierrez, Belen Masia, and Elisa Amoros, Universidad de Zaragoza; Kavita Bala, Shuang Zhao, Cornell University; Ashok Veeraraghavan, Rice University.; Thomas Willwacher, Harvard University.

ADVERTISEMENT
Part of complete coverage on
November 24, 2014 -- Updated 2310 GMT (0710 HKT)
If Obama thinks pushing out Hagel will be seen as the housecleaning many have eyed for his national security process, he'll be disappointed, says David Rothkopf.
November 25, 2014 -- Updated 1311 GMT (2111 HKT)
The decision by the St. Louis County prosecuting attorney to announce the Ferguson grand jury decision at night was dangerous, says Jeff Toobin.
November 25, 2014 -- Updated 0857 GMT (1657 HKT)
China's influence in Latin America is nothing new. Beijing has a voracious appetite for natural resources and deep pockets, says Frida Ghitis.
November 24, 2014 -- Updated 2151 GMT (0551 HKT)
Iranian President Hassan Rouhani speaks during a press conference in the capital Tehran on June 14, 2014.
The decision to extend the deadline for talks over Iran's nuclear program doesn't change Tehran's dubious history on the issue, writes Michael Rubin.
November 21, 2014 -- Updated 1925 GMT (0325 HKT)
Maria Cardona says Republicans should appreciate President Obama's executive action on immigration.
November 21, 2014 -- Updated 1244 GMT (2044 HKT)
Van Jones says the Hunger Games is a more sweeping critique of wealth inequality than Elizabeth Warren's speech.
November 20, 2014 -- Updated 2329 GMT (0729 HKT)
obama immigration
David Gergen: It's deeply troubling to grant legal safe haven to unauthorized immigrants by executive order.
November 21, 2014 -- Updated 0134 GMT (0934 HKT)
Charles Kaiser recalls a four-hour lunch that offered insight into the famed director's genius.
November 20, 2014 -- Updated 2012 GMT (0412 HKT)
The plan by President Obama to provide legal status to millions of undocumented adults living in the U.S. leaves Republicans in a political quandary.
November 21, 2014 -- Updated 0313 GMT (1113 HKT)
Despite criticism from those on the right, Obama's expected immigration plans won't make much difference to deportation numbers, says Ruben Navarette.
November 21, 2014 -- Updated 0121 GMT (0921 HKT)
As new information and accusers against Bill Cosby are brought to light, we are reminded of an unshakable feature of American life: rape culture.
November 20, 2014 -- Updated 2256 GMT (0656 HKT)
When black people protest against police violence in Ferguson, Missouri, they're thought of as a "mob."
November 19, 2014 -- Updated 2011 GMT (0411 HKT)
Lost in much of the coverage of ISIS brutality is how successful the group has been at attracting other groups, says Peter Bergen.
November 19, 2014 -- Updated 1345 GMT (2145 HKT)
Do recent developments mean that full legalization of pot is inevitable? Not necessarily, but one would hope so, says Jeffrey Miron.
November 19, 2014 -- Updated 1319 GMT (2119 HKT)
We don't know what Bill Cosby did or did not do, but these allegations should not be easily dismissed, says Leslie Morgan Steiner.
November 19, 2014 -- Updated 1519 GMT (2319 HKT)
Does Palestinian leader Mahmoud Abbas have the influence to bring stability to Jerusalem?
November 19, 2014 -- Updated 1759 GMT (0159 HKT)
Even though there are far fewer people being stopped, does continued use of "broken windows" strategy mean minorities are still the target of undue police enforcement?
November 18, 2014 -- Updated 0258 GMT (1058 HKT)
The truth is, we ran away from the best progressive persuasion voice in our times because the ghost of our country's original sin still haunts us, writes Cornell Belcher.
November 18, 2014 -- Updated 2141 GMT (0541 HKT)
Children living in the Syrian city of Aleppo watch the sky. Not for signs of winter's approach, although the cold winds are already blowing, but for barrel bombs.
November 17, 2014 -- Updated 1321 GMT (2121 HKT)
We're stuck in a kind of Middle East Bermuda Triangle where messy outcomes are more likely than neat solutions, says Aaron David Miller.
November 17, 2014 -- Updated 1216 GMT (2016 HKT)
In the midst of the fight against Islamist rebels seeking to turn the clock back, a Kurdish region in Syria has approved a law ordering equality for women. Take that, ISIS!
November 17, 2014 -- Updated 0407 GMT (1207 HKT)
Ruben Navarrette says President Obama would be justified in acting on his own to limit deportations
ADVERTISEMENT