Using a staccato burst of laser fire, this ingenious camera peers around a distant corner, tracking the position, movement, and rough shape of any solid object that human eyes cannot even see. The team of engineers and optics researcher, led by Genevieve Gariepy and Daniele Faccio at Heriot-Watt University in Edinburgh, Scotland, say it's the first such camera that can track moving objects around corners in real time.

"For future use, this could be incredibly helpful for [computer assisted] vehicles to avoid collisions around sharp turns. . . or emergency responders looking see around blind corners in dangerous situations," Gariepy says. The scientists explain their device in a study out today in the journal Nature Photonics.

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Echoes of Light

This fascinating new detector is basically a combination of a precise laser and an advanced camera so sensitive "it can track individual photons," Gariepy says. It works by shooting short laser pulses and then tracking the laser light as it bounces off and echoes back from any unseen objects.



For example: Imagine there's a brick wall running along your right side, with a sharp corner ahead. To see a person beyond that corner, Gariepy's detector will first focus on a small square on the floor, roughly 1000 pixels across, just beyond the corner. Then the laser will fire to the left of that square. Once the laser smacks into the ground, the light will spread out in rings in all directions, like the ripples in a pond after you toss in a pebble. The camera will sense that ring of light as it glides past its 1000-pixel square of focus. Then, as the light hits an object hidden around the corner and echoes back through the square, the camera will track the light's return and know that something is there.

"It can track individual photons."

Gariepy's device doesn't do this just once. To get an accurate reading, it will fire and record the laser's echo an astonishing 67 million times per second and average the results after three seconds. Depending the shape of the echo, and how long it took to return, the device will quickly crunch the numbers to tell you how big and far away the object is. If that object is moving, Gariepy's device will be able to make a concrete measurement every 3 seconds, tracking it as it approaches, leaves, or moves in any direction beyond the corner.

Testing their detector in their laboratory, Gariepy and her colleagues found that they could track a one-foot-tall cartoonishly shaped foam human figure with striking precision around corners—and even backwards around hairpin turns. When using the detector to estimate the size of the figure, they could do so with about a 20 percent margin of error. In a few preliminary tests Gariepy says she also found she could track multiple objects at the same time.

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Instant Snapshots

The concept of using echo mapping techniques to see around blind corners is not new, Gariepy says. In fact, some existing cameras can even create rough 3D images using the same idea. "But these other technologies, especially ones based on 3D constriction, are quite slow, taking minutes or even hours to create a snapshot," Gariepy says. And if you're looking to track motion, these slow response times are practically useless. "Let's just say that, after an hour, you'll be well aware if there was a car coming toward you from around some corner."

Gariepy's device owes its speed to its incredible camera, a feat of imaging technology developed at the University of Edinburgh. As for moving forward to commercial applications with even faster or more accurate detection, says Gariepy, that'll be a matter or developing even more sensitive cameras, or finding clever ways to decrease the noise in the data that would drown out the laser's signal. For example, Gariepy says her team is already working on using filters to cancel out all light but the very specific wavelength emitted by their laser.

"And now that we've shown the proof of principle," she says, "we're focusing our experiments on bigger scales, looking to detect objects at much larger distances."

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