We’re used to the idea that when you snap a photo with a camera, it’s of something you can see through the lens. We’re also used to the idea that our eyes can’t see around corners. Now some research in Scotland is challenging both these ideas with a camera that can see things hidden around the bend.
Light travels in straight lines, as you’ll remember from high school science. This means when your eye sees something, a bunch of light rays have come directly from the object in straight lines and shone right into your eyeball, where they’ve been focused into an image. This generally means the thing you were looking at was right in front of you, because light doesn’t bend around corners unless there’s a mirror angled in the right direction. Cameras work in the same way.
Recently, however, researchers in Scotland have been experimenting with laser range finders, and by performing incredibly precise measurements, they’ve realized they can make a laser “see” things that otherwise would be invisible because they were hidden around a corner—where light beams traveling in straight lines usually wouldn’t go.
The trick is to recognize that when you shine a laser onto a wall or a floor near a corner, some of the light bounces randomly off the floor and a very small portion of it gets bounced around the corner. If there’s a moving object hidden around that corner, some of the light gets reflected off it, and a very tiny portion of this is scattered back toward more or less the same part of wall or floor.
By precisely timing the time taken for the beam to travel from the laser light source to the first bounce on the floor, the second bounce off the hidden moving object, and then the third bounce on the floor or wall again (and doing some clever math to distinguish this light from other “noise”), the Scottish team has realized they can detect where the otherwise-hidden moving object is.
This is a very crude form of “seeing,” sure. But it could prove to be very important for all sorts of imaging systems in the future. Remember that laser range finders were once this experimental, but nowadays lasers form part of LIDAR systems, which are being used by companies like Apple to map places and streets with incredible accuracy. Instantly you can see how useful this sort of round-the-corner vision would be for surveillance or, possibly, for self-driving cars.