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‘Time camera’ generates 3D images from echoes of light

Imagine shouting at an animal and telling from the returning echo whether it’s a dog or a horse. A team of scientists has pulled off the photographic equivalent of that trick: They teased out a 3D image of a scene by timing the reflections of light onto a simple detector. Known as temporal imaging, the new technique demonstrates the power of a type of artificial intelligence called machine learning to unearth patterns in what appears to be mere noise.

“It’s really surprising to me that they can get anything out of this system because there’s absolutely not enough information coming out of it,” says Laura Waller, a computer scientist and electrical engineer at the University of California, Berkeley, who was not involved in the work. “That just shows the ability of machine learning to solve things that seem unsolvable.”

In conventional photography, ambient light reflects off an object, and a lens focuses it on to a screen of tiny light-sensing elements or pixels. The image is the pattern of brighter and dark spots the reflected light creates. A so-called time-of-flight camera can even add depth and make a 3D image by timing exactly when a flash of light reflected from an object arrives at the various pixels.

In recent decades, researchers have invented subtler ways to capture an image using just a single pixel detector. To do that, they expose the object not to uniform illumination, but to flashes of different patterns of light that vaguely resemble QR codes—those little square barcodes found on packaging. Each pattern will reflect off different parts of the object, so that the intensity of light measured by the pixel varies with the pattern. By tracking those variations, researchers can reconstruct the image of the object.

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