Nokia unveils 41-megapixel imaging sensor technology

Nokia unveils 41-megapixel imaging sensor technology

The most spectacular part of Nokia's presentation Sunday at Mobile World Congress was the unveiling of a new super imaging system, a sensor -- developed with Toshiba and other Nokia partners, coupled with Carl Zeiss optics -- that can capture 41 megapixels.

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The phone's camera itself turns this capture into 2/3-, 5-, 8-, or astoundingly, 38-megapixel images. The impact can be seen in two ways, says Jo Harlow, Nokia senior vice president of smart devices. First the lower-resolution pictures can be blown up to huge sizes and yet retain crystal-clear, crisp and highly detailed images. That's because the system condenses seven pixels of information into one.

But high-resolution photos, up to the 38-megapixel maximum, can be zoomed, reframed, cropped and resized afterward to uncover details not visible to the eye. Harlow showed one photo, which was displayed on a wall, and zoomed in on a painting that was one of the objects in the photo. The result was a remarkable exploration of the image, finding new things to see, things that you simply couldn't see, without the new sensor.

PureView debuts on the Symbian-based Nokia 808 PureView phone. The sensor technology had been under development for some time when Nokia was focused on Symbian as its main platform. But Nokia executives say they fully intend to bring PureView to "other platforms," which presumably means Windows Phone.

The idea for what Nokia has branded PureView came from two Nokia engineers: Juha Alarhu and Eero Salmelin. [Salmelin is featured in one of Nokia's PureView videos on YouTube.] Eventually, hundreds of engineering staff were involved. They scrapped a lot of the conventional thinking around imaging. Unlike typical systems, PureView discards the scaling/interpolation model of digital zoom, as well as the conventional optical zoom technology, which relies on a series of lens elements moving back and forth to vary the magnification and field of view.

According to a white paper by the engineers, the key is the super-high-resolution sensor, which has an active area of 7728 x 5368 pixels, which gives the total of more than 41 megapixels. Depending on the aspect ratio chosen, the sensor uses 7728 x 4354 pixels for 16:9 images and videos, or 7152 x 5368 pixels for 4:3 images and videos.

"Conventional zoom tends to scale up images from a relatively low resolution, resulting in poor image quality," they write. "When you zoom with the Nokia 808 PureView, in effect you are just selecting the relevant area of the sensor. So with no zoom, the full area of the sensor corresponding to the aspect ratio is used."

They also used "pixel oversampling," to combine many pixels to create a single "super pixel."

"When this happens, you keep virtually all the detail, but filter away visual noise from the image," they write. "The speckled, grainy look you tend to get in low-lighting conditions is greatly reduced. And in good light, visual noise is virtually non-existent."

At maximum zoom, over five times more light reaches the PureView sensor than a generally equivalent optical-zoom digital camera. "And this means you get the benefit of faster shutter speeds."

You can find more details of the PureView sensor in the online whitepaper.

John Cox covers wireless networking and mobile computing for Network World. Twitter: john_cox@nww.comBlog RSS feed:

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