Breakthrough Promises Better Digital Pictures
A pair of newly patented technologies developed by Rochester researchers soon may soon enable the power-hungry chips in digital cameras to use a fraction of their current energy, capture better images, shrink in size, and run for years on a single battery.
The team of Mark Bocko, a professor of electrical and computer engineering, and Zeljko Ignjatovic, an assistant professor of electrical and computer engineering, has designed a prototype chip that can connect light to a digital signal right on the pixel, and they are working to incorporate a second technology that will compress the image with far fewer computations than the best current compression techniques.
“These two technologies may work together or separately to greatly reduce the energy cost of capturing a digital image,” says Bocko. “One is evolutionary in that it pushes current technology further. The second may prove to be revolutionary because it’s an entirely new way of thinking about capturing an image in the first place.”
The first technology integrates an analog-to-digital converter at each pixel location in a CMOS sensor, a common semiconductor fabrication process used in most chips manufactured today. Previous attempts at such an on-pixel conversion have required large transistors, leaving too little area to collect light.
The new designs use as few as three transistors per pixel, reserving nearly half of the pixel area for light collection. First tests on the chip show that at video rates of 30 frames per second it uses just 0.88 nanowatts per pixel—50 times less than the industry’s previous best. It also trounces conventional chips in dynamic range, which is the difference between the dimmest and brightest light it can record.
In the second advance, called “Focal Plane Image Compression,” Bocko and Ignjatovic have designed a new way to arrange photodiodes on an imaging chip so that compressing the resulting image demands as little as 1 percent of the computing power usually needed.
Team members are attempting to build a prototype chip that incorporates both technologies into a single unit to see how much real-world processing power the designs will save. They plan to integrate the technology into wireless security cameras at first.