Pixel-perfect pictures

Screen grabs from video streams would be as clear as a high-resolution photograph with a new technology from Oxford University researchers.

The technology, dubbed Fast Pixel Shutter Imaging (FPSI), would allow cameras to capture high-speed video and high-resolution still images simultaneously on the same detector without additional memory requirements.

Gil Bub, leader of the technology’s development team and a bio- technology researcher at Oxford, said this has never been done before because high-resolution images impose bandwidth constraints that result in increased noise (interference) with acquisition speed. Low-noise cameras typically read out frames slowly to reduce noise. High-speed, low-noise imaging is typically carried out with low-resolution detectors, so re- searchers use a second camera to capture spatial detail.

Oxford solved this problem by selectively controlling the exposure time of different parts of the image sensor using fast optical switches. This allows the embedding of high-frequency content in images that can be decoded to create a movie.

Bub said: ‘With traditional cameras you have a global shutter for the whole set of pixels. We’re going to have individual shutters to control when each pixel gets exposed.’

With a different exposure time set for each pixel, he said a camera taking a still photo could detect movement such as light turning on. The movement would be embedded as high-frequency information in the image. He added: ‘You could decode that and pull out an image sequence.’

Bub has demonstrated the technology using a prototype built out of a digital micro-mirror array comprising a vast amount of individually moveable mirrors measuring 10 microns across. He said: ‘The mirrors can be toggled on and off. I’m using them, in effect, as pixel-level optical switches.’

Bub is working with researchers at Nottingham University on fashioning the technology into a single CMOS chip that could be integrated into small electronic devices, including mobile phones.

Within six months they plan to unveil a mobile-phone-sized camera that can demonstrate FPSI and tap into an industry that was worth $3bn in 2007.

The technology is being commercialised through Oxford University spin-out ISIS Innovation.

Siobhan Wagner