LED Skylights Perfectly Mimic Natural Sunlight

The lights fool human brains and camera eyes

CoeLux skylight

A man in a small white-walled room steps back to look up through a skylight and squints at the bright sunny sky visible outside. "It’s pure magic," he says in this video (via Digg). He's amazed because the skylight earning such puzzling looks isn’t a window at all. It’s a technological trick.

The artificial skylight that you won't believe isn't real

"Our goal is to create in the people looking at the sun and the sky the perception of infinite depth," says Paolo Di Trapani, professor of optics and experimental physics at the University of Insubria, in Italy, and founder and CEO of a company called CoeLux. The company designed their light to mimic both the color temperature and intensity of natural sunlight.

That innovation has eluded other lights because a proper daylight-mimicking light can't just approximate the sun’s rays but must also take into account the atmosphere. The reason the sky is blue is because molecules of carbon dioxide, oxygen, nitrogen and other elements in the atmosphere scatter the shortest wavelength of light— blue — more intensely than other wavelengths. When we look up at the sun, it appears mostly unaltered. But the rest of the atmosphere appears blue because of all the short wavelength light bouncing around it.

The CoeLux light uses nanoparticles to do this scattering and essentially compresses the six miles of Earth’s atmosphere into a few millimeters. An LED projector shines in full spectrum white light to create the sun, which in the videos appears far away in the sky. This last trick depends on "a sophisticated optical system" that wasn’t explained in detail, reports Carl Engelking for Discover’s "D-brief" blog. He writes:

CoeLux envisions its lights appearing in hospitals, windowless offices and basements hundreds of feet below ground. The lights are also useful for photographers that are looking to shoot in-studio photos with natural light. The only downside for these lights, right now at least, is their price: roughly $61,000 plus $7,000 for installation.

Photos on the company’s website show the effect is convincing, and CoeLux even offers lights angled to mimic sunlight beams found in Mediterranean and Nordic countries. These lights haven’t been tested, but since other artificial lights appear to ward off seasonal blues, perhaps some denizens of northern climes would appreciate the sunny beams of the Mediterranean.

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