Physics Nobel: How telephone echoes lead to digital cameras

The 2009 Nobel Prize for Physics is split between Charles Kao, for developing fiber optics, and Willard Boyle and George Smith, who invented the Charge Coupled Device or CCD at Bell Laboratories in 1969. CCDs are now the ubiquitous heart of digital cameras.

UC Davis physics professor Tony Tyson joined Bell Labs around the same time as Boyle and Smith invented the CCD, and has worked on the development of these light-sensing chips and ever more powerful digital cameras throughout his career.

“The invention of the CCD at Bell Labs by Boyle and Smith has transformed our view of the universe and of ourselves.  The ubiquitous CCD imager inside our cameras enables us all to snap digital photos of the universe around us.  And it lets astronomers view the distant universe in increasingly wide and faint detail,” Tyson said.

Tyson’s first scientific use of a digital camera was to take pictures of red-blood cells in sickle cell anemia. In the 1990s, he built the Big Throughput Camera or BTC, which was used to make the discovery that the universe is not only expanding, but that the expansion isFirst CCD speeding up. Now, he is leading the effort to build the Large Synoptic Survey Telescope or LSST, which will have a 3-billion-pixel camera and will survey the night sky in exquisite detail.

As Tyson tells the story, Boyle and Smith’s boss at Bell Labs asked them to find a solution to the problem of echo on telephone lines. The phone company was using a delayed tape to replay signals and cancel out the echo, but the tapes kept breaking. They wanted a solid-state device that could slightly delay the audio signal in a predictable way.

“After their boss left they scribbled on the blackboard and came up with a scheme in about half an hour,” Tyson said. Boyle and Smith built their device with nine silicon electrodes in about a month and got it to work, but found a problem.

“They realised it worked better when someone was standing over it, so they tried turning out the room lights, and it worked perfectly,” Tyson said.

Within moments, Boyle and Smith realised that they had just made a nine-pixel imaging device.

Bell Labs tried to use the new technology for their Picturephone, replacing vacuum tubes with solid-state circuits. (Tyson has what may be the only surviving Picturephone in his office). But the Picturephone never took off commercially, and the company killed the project. Among other problems, the phones required so much bandwidth on the old, copper wiring as to be prohibitively expensive — a problem that would be solved with the development of fiber-optic cables.

Tyson says he initially regarded cameras based on charge-coupled devices as “an amusement” and built an early 100 by 100 pixel camera in his garage. At the time, astronomers were using 10″ by 10″ photographic plates for their observations.

But Tyson said that as he tinkered with CCDs, he realized that if they could be made in a mosaic, they could indeed be used for astronomy. Since then, he has designed and built cameras for telescopes including the BTC and the LSST.

“It’s enabled all sorts of very nice science from biomedicine to astronomy,” Tyson said.

Additonal UC Davis connection: Charles Kao is second cousin of Winston Ko, dean of mathematical and physical sciences.

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