Ultrasensitive camera uses laser to see around corners

New Scientist : An ultrasensitive camera that was previously used to make a movie of a laser beam has been adapted to detect the movement of objects hidden around corners. The camera can identify the position of an individual photon on a grid at the equivalent of 20 billion frames per second. To see around a corner, researchers fire a laser at the floor nearby. When the light hits the floor, some of the photons are scattered, which creates a spherical “echo.” Part of the echo bounces back to the camera, and another part goes around the corner. That part then hits whatever is around the corner, which produces another echo effect. The camera is sensitive enough to detect any of the photons that make their way back to the camera. By pulsing the laser 67 million times per second, the researchers can track a moving object by monitoring the changes in the echo’s signal. The process is faster than building an image of a stationary object and could be useful for search-and-rescue teams trying to find people buried in rubble or trapped in inaccessible rooms.