High-tech filter could produce brighter, clearer images in low light

Technology News

A new camera filter that lets in three times more light than conventional filters may be three years away, according to University of Utah researchers.

PHOTO CREDIT: Rajesh Menon In this illustration, light passes through the new camera color filter developed by University of Utah Electrical and Computer Engineering professor Rajesh Menon before it reaches the digital camera sensor. Since all of the light reaches the sensor, unlike conventional digital camera filters where only a third of the light passes through, photos taken with Menon’s new filter are much cleaner and brighter in low light.
PHOTO CREDIT: Rajesh Menon
In this illustration, light passes through the new camera color filter developed by University of Utah Electrical and Computer Engineering professor Rajesh Menon before it reaches the digital camera sensor. Since all of the light reaches the sensor, unlike conventional digital camera filters where only a third of the light passes through, photos taken with Menon’s new filter are much cleaner and brighter in low light.

Electrical and Computer Engineering professor Rajesh Menon thought of the idea while developing a new kind of spectrometer, a device that reads the wavelength or frequency of light. He realized that converting spectral information to colour for a spectrometer could be applied to color imaging.

Traditional digital cameras use an electronic sensor that collects the light to make the picture. Over that sensor is a filter designed to allow in only the three primary colors: red, green and blue. With the filter absorbing the orange, yellow, indigo and violet from the colour spectrum, much of the natural light never makes it to the sensor.

“If you think about it, this is a very inefficient way to get colour because you’re absorbing two thirds of the light coming in,” Menon said in a media release.

Menon and doctoral student Peng Wang describe their solution in the journal, Optica.

They designed a new filter that is about a micron thick (about 100 times thinner than a human hair). The wafer of glass has microscopic ridges etched on one side to bend the light as it passes through, which creates a series of colour patterns or codes. Software reads the codes to determine what colours they are. Instead of reading three colors, the sensor reads at least 25 new codes, producing photos that are much more accurate and with nearly no digital grain.

“You get a lot more colour information than a normal colour camera,” Menon said. “It’s not only better under low-light conditions, but it’s a more accurate representation of colour.”

Perhaps ironically, the new filter may be cheaper to produce because it is easier to manufacture, Menon said, because traditional filters need three steps, one for each of the three colours of light.

Menon is negotiating with large electronics and camera companies to bring this technology to market. He says the first commercial products using this new technology could be out in three years.

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