More Than Meets the Eye: How the CCD Transformed Science
The 2009 Nobel Prize for Physics went, in part, to the inventors of the charge-coupled device George Smith and Willard Boyle this week. Their innovation, sketched out in 1969, is now the imager in millions of digital cameras and telescopes.
The very first prototype, pieced together months after Smith and Boyle laid out its working principles, is pictured above.
A charge-coupled device, in most applications, translates light into an electronic signal. Photons of light striking an array of capacitors create an electrical charge proportional to their intensity, which the charge-coupler transforms into voltage. That signal can be digitized and transformed by the dull magic of high-performance computing into Hubble’s images.
Millions of CCDs are made each year for mass market cameras, but they also proved a transformational technology in science by providing a much more sensitive light sensor than previously existed. After being overlooked for decades, the Nobel win was a mild surprise but well deserved.
“There wasn’t anything that could compete in scientific imaging,” said Tony Tyson, an astronomer at the University of California, Davis, who built the first CCD camera for scientific applications in the late 1970s. “You’re interested in getting very high signal-to-noise ratios. There’s nothing that really competes with CCDs.”
For the really dim things astronomers look at, the number of photons of light coming from a source is so small that each one counts. Out of every 100 photons, a CCD can record more than 90 of them. Photographic plates can barely reach 10 percent. And your eyes? Their quantum efficiency is in the 1 to 4 percent range.
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