Digital camera pixel failure no problem with new SFU technology

June 29, 2006, volume 36, no. 5
By Barry Shell

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Everyone in Glenn Chapman's research group is a camera buff. They all own big, black, digital SLR cameras, which they use to conduct research.

Engineering science graduate students Joe Dudas and Cory Jung and undergraduates David Chen and Linda Wu are working on software to locate pixel defects in all types of digital cameras. Professor Chapman is applying for a patent on the method and the students will be named in it.

Over time the image sensor in any digital camera is likely to develop a few dead pixels—microscopic elements that capture light. These might appear as minute specks in a picture. Until now, dead pixels have been difficult to locate.

"The great thing about our method is that the camera does not have to be sent in to the repair shop for testing and recalibration,” says Chapman. It can be done by anyone, he says, because the process examines the photographs rather than the camera. The patent describes a software method to analyse about 40 pictures from any camera.

The SFU system checks over a series of pictures from a camera and catalogues any bad pixels. From then on, off-the-shelf post-processing software can fill in dead pixels by interpolation, a method of averaging the colours from neighboring pixels.

The technology works for all kinds of digital imaging devices. Users of costly high-end technology like security cameras or medical X-ray systems are very focused on image quality. Software such as Chapman's can significantly extend the lifetime of expensive equipment for a relatively low cost.

Good consumer cameras today have image sensors with eight or nine megapixels. "To match good quality film you need cameras that can capture 18 to 72 megapixels," says Jung, who expects that digital cameras will one day accomplish this.

Dudas expects to see subtle improvements in image clarity, better low light performance, and increased colour range.

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