Imaging chips revolutionized the photo-graphy industry, and now the chips themselves are being revolutionized by researchers at the University of Rochester. A pair of recently patented technologies may soon enable power-hungry imaging chips to use just a fraction of the energy they use today and capture better images to boot -- all while enabling cameras to shrink to the size of a shirt button and run for years on a single battery. The University of Rochester team of Mark Bocko, professor of electrical and computer engineering, and Zeljko Ignjatovic, assistant professor of electrical and computer engineering, has designed a prototype chip that can digitize an image at the level of individual pixels. The researchers are now 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 being developed integrates an oversampling "sigma-delta" analog-to-digital converter at each pixel location in a CMOS sensor. Previous attempts to do this on-pixel conversion have required far too many 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. Initial 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 that can be recorded. Existing sensors can record light 1,000 times brighter than their dimmest detectable light, a dynamic range of 1:1,000, while the Rochester technology already demonstrates a dynamic range of 1:100,000.
The second technology has taken many researchers by surprise. Using a method called focal-plane image compression, Bocko and Ignjatovic have figured out a way to arrange photodiodes on an imaging chip so that compressing an image demands as little as 1 percent of the computing power usually needed.
Difference engines
Slipsticks to the moon
In the early 1600s, John Napier, a Scottish mathematician who had previously developed Napier's Bones, which were multiplication tables inscribed on strips of wood or bone, invented logarithms. After the publication of Napier's work, Edmund Gunter of Oxford University developed a calculating device with a single logarithmic scale, which, with additional measuring tools, could be used to multiply and divide. In 1630, William Oughtred of Cambridge University invented a circular slide rule, and in 1632, he combined two Gunter rules, held together with both hands, to make a device that is recognizably the modern slide rule. The slide rule was to remain in common use for more than 300 years.
In 1815, Peter Roget (the Scotsman who gave us the thesaurus) invented the log-log slide rule, which included a scale displaying the logarithm of the logarithm. This allowed the user to directly perform calculations involving roots and exponents. This was especially useful for fractional powers. In 1859, a French army lieutenant named Amedee Mannheim developed a slide rule that was then manufactured by a firm of national reputation, which led to its being adopted by the French Artillery.
In 19th century Germany, one observatory used a steel slide rule about 2 meters long. Since astronomical work required fine computations, it had a microscope attached, giving it accuracy to six decimal places.
Throughout the 1950s and 1960s, the slide rule was the symbol of the engineer's profession. Pickett brand slide rules were the standard in the Apollo space program; a Pickett N600-MES (6 inches long, with a magnifying cursor and in "Eye-Saver" yellow) was standard equipment on all Apollo flights. Slide rules not only made getting to the moon possible, they went along for the ride.
As useful and ubiquitous as they had been, slide rules quickly passed from use with the rise of portable electronic calculators in the late 1960s.
IBM puts its spin on magnetism
IBM scientists have developed a powerful new technique for exploring and controlling magnetism at its fundamental atomic level. The new method promises to be an important tool not only in the quest to understand the operation of future computer-circuit and data-storage elements as they shrink toward atomic dimensions, but also in the quest to lay the foundation for new materials and computing devices that leverage atom-scale magnetic phenomena.
"We have developed a window into the atomic heart of magnetism," says Andreas Heinrich, research staff member at IBM's Almaden Research Center in San Jose. "We can now position atoms and then measure and control their magnetic inter-actions within precisely designed structures."
The new method, called spin-excitation spectroscopy, uses IBM's low-temperature scanning tunneling microscope designed for use with a broad range of magnetic fields up to 140,000 times stronger than the Earth's. The researchers first move atoms into position and then measure the interactions between their atomic spins, which are the fundamental sources of magnetism.
IBM researchers expect to use this new technique in the future to do the following:
-- Explore the limits of magnetic data storage.
-- Determine the feasibility of spin-based wires and a spin version of the molecular-motion cascade.
-- Investigate how engineered spin inter-actions could be applied to quantum information systems.
The new research builds upon the IBM team's development in late 2004 of spin-flip spectroscopy -- a method for measuring magnetic properties of single atoms, and a breakthrough step toward quantum computing.