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Camera filter yields sharper, brighter photos in low light

Posted: 02 Nov 2015     Print Version  Bookmark and Share

Keywords:University of Utah  camera filter  sensor  smartphone 

A researchers from the University of Utah Electrical has created a camera colour filter for digital cameras that lets in three times more light than conventional filters. According to computer Engineering professor Rajesh Menon, the innovative device results in much cleaner, more accurate pictures taken in lowlight. The filter can be used for any kind of digital camera, but Menon is developing it specifically for smartphone cameras.

Anyone who's taken a picture of birthday candles being blown out or a selfie during a romantic candlelit dinner knows how disappointing it is when the photo comes out dark and grainy.

Rajesh Menon

Rajesh Menon (PHOTO CREDIT: University of Utah College of Engineering/Dan Hixson)

"Overall, camera phones are very good, but they are not very good in lowlight," said Menon. "If you go out on a hike in the evening and take a picture of the sky you will see that it's very grainy. Lowlight photography is not quite there and we are trying to fix that. This is the last frontier of mobile photography."

Traditional digital cameras, whether they are point-and-shoot cameras or the now-ubiquitous smartphone cameras, use an electronic sensor that collects the light to make the picture. Over that sensor is a filter designed to allow in the three primary colours: red, blue and green. But by doing so, natural light hits the filter, and the filter absorbs two thirds of the colour spectrum in order to let through each of the three primary colours.

"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 noted. "But this is how it's been done since the 1970s. So for the last 40 years, not much has changed in this technology."

Menon's solution is to use a colour filter that lets all light pass through to the camera sensor. He does this with a combination of software and hardware.

Camera colour filter

In this illustration, light passes through the camera colour filter developed by 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 filter are much cleaner and brighter in lowlight.

Menon has designed a colour filter that is about a micron thick. It is a wafer of glass that has precisely-designed microscopic ridges etched on one side that bends the light in certain ways as it passes through and creates a series of colour patterns or codes. Software then reads the codes to determine what colours they are.

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