Here’s a camera that uses lasers and crazy high shutter speeds to see around corners. The principal behind it is easy to understand, but it’s mind-bending to think that it actually works.
Researchers at Herriot-Watt University in Edinburgh use a sensitive, high-speed camera, along with a standard laser pointer to detect moving objects around corners.
It works like this. Imagine you’re standing just before the corner of an office corridor. You shine the laser onto the floor, just past the end of the side wall. The light bounces off the floor, in all directions, like a ripple in a pond. The light then bounces of any objects–walls, furniture, walking people–and is reflected back. Finally, it rebounds off the corridor’s walls and back to you, to be captured by your camera.
A regular camera would see nothing of this except may the original laser spot on the floor, but the special camera at Herriot-Watt is a single-photon avalanche diode (SPAD) camera, which is sensitive enough to capture a single photon of light. The camera’s other trick is that it can shoot an astonishing 20 billion frames per second, so every single photon of laser light that comes back can be captured.
Because it records both the light and the direction it came from, it can piece together the reflections to construct an “image” of the scene around the corner. It’s a bit like the principle used by sonar to detect objects underwater.
The computer brains that put all this together take about a second to process the scene, which makes it fast enough to detect moving objects, comparing the difference between subsequent “frames.” In fact, movement is essential, because the camera relies on the subject’s motion in order to differentiate it from the background.
Far from just being a clever science stunt, the setup could be very useful in the real world. The researchers say that it could be “used in rescue operations, when terrain is dangerous or when you don’t want to enter a room unless you have to.” In these situations, though, a good old-fashioned camera-on-a-stick would also do the trick.
More interesting is their claim that the camera could be used in cars to detect oncoming vehicles around corners. Your car might already sound an alarm when you drift out of lane or get too close to the vehicle in front. Imagine how handy it would be to get a warning that there’s a truck hurling towards you around that blind bend.
Another advantage is that you don’t have to poke anything around the corner to sneak a peek, unlike that camera-on-a-stick or a mirror. That’s something that will likely interest the military, especially as the camera can detect the position of an object to as accurately as half an inch. That’s enough to lock on a target. All you’d need would be a gun that can shoot around corners.