Co-Inventor of the Charge Coupled Device for which he won the 2009 Nobel Prize in Physics
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Bbbrrring, bbbrrring. It’s that darn videophone again. These things will never catch on, thinks Willard Boyle as he squirms in his chair before answering, trying to find a position that is comfortable, but he doesn’t put his face in view of the camera. It’s too early in the morning to be seen and Boyle knows who’s calling — his boss, Jack Morton, head of advanced research at Bell Labs in New Jersey and the father of transistor electronics.
It’s about 8:30 a.m., a lovely day in early October 1969. From the window Boyle sees beautiful rolling hills; the leaves have not yet taken on their fall colours. Boyle has a big office at Bell’s world-famous think-tank and research centre. Fifteen years of brilliant invention, including the first continuous ruby laser, have elevated him to executive director of device development at Bell Labs. But he still has a boss, a very demanding boss, who calls him every morning on that annoying Bell videophone. Reluctantly, he picks up.
“So what happened yesterday?” came the familiar question.
Boyle shifted a little more in his chair.
“I can’t see you, Bill,” said Morton.
“Right here, Jack.”
“So what’d you guys do yesterday?”
“You know, more of the same. We’re still working on those new transistors,” said Boyle.
“Look, Bill, the other guys are doing great stuff with magnetic bubbles. It’s terrific. What are you semiconductor guys doing? The heck with transistors. Try and come up with something different. I’ll call tomorrow.” And he hung up.
Boyle thought about it for a while and then called another physicist down the hall, George Smith, to ask him to drop by after lunch. For the rest of the morning Boyle worked on other things.
After lunch, George went to Boyle’s office and they brainstormed at the blackboard. They worked on an idea for handling little pockets of charge in a silicon matrix in a way that was similar to the popular notions of moving microscopic bubbles of magnetism around on other kinds of material. They fiddled with some math and drew some sketches on the blackboard showing how this new device could be made. After about an hour and a half Boyle said, “Okay, this looks pretty good.”
“We should name it something,” said Smith.
“Well, we’ve got a new device here. It’s not a transistor, it’s something different,” said Boyle.
“It’s got charge. And we’re moving the charge around by coupling potential wells,” said Smith.
“Let’s call it a charge coupled device,” said Boyle.
“Sure, ‘CCD.’ That’s got a nice ring to it.”
Researchers and colleagues pooh-poohed Boyle and Smith’s idea, saying it would never work. Remember, at this point it was only a theory, a bunch of equations and diagrams on a blackboard. But the pair decided to take the plans to the shop down the hall to see if the device could be made. Some months later it was made, and it worked exactly as expected.
Soon afterwards, Boyle presented a paper about the CCD invention at a conference in New York on “The Future of Integrated Circuits” and, as he says, “All hell broke loose.” The phone started to ring with calls from people and companies anxious to learn more. One of the calls was from Boyle’s boss, Jack Morton.
“I guess there’s probably a future in this semiconductor IC thing after all,” said Morton, and that was all the praise Boyle was going to get from him.
In the succeeding years Boyle and Smith went on to win many awards for the device that is at the heart of virtually every camcorder, digital camera and telescope in use today.
Boyle’s major contributions include the first continuously operating ruby laser, which he invented with Don Nelson in 1962. Ruby was the first material ever made to produce laser light, and ruby lasers are now used for tattoo removal, among other things. Before Boyle’s invention, lasers could only give short flashes of light. He was also awarded the first patent (with David Thomas) proposing a semiconductor injection laser. Today, semiconductor lasers are at the heart of all compact disc (CD) players and recorders, but when Boyle patented the idea nobody had even dreamed of cds. Stereo hi-fi (or high fidelity) records were the new thing.
In 1962 Boyle became director of space science and exploratory studies at Bellcomm, a Bell subsidiary providing technological support for the Apollo space program of the U.S. National Aeronautics and Space Administration. While with NASA, Boyle helped work out where astronauts should land on the moon. In 1964 he returned to Bell Labs and switched from research to the development of electronic devices, particularly integrated circuits, which are now essential building blocks in telecommunications and electronics in general.
Despite all these great achievements, Boyle is best known as co-discoverer of the charge coupled device. Besides their use as image sensors, CCDs can be used as computer memory, electronic filters and signal processors. As imaging devices they have revolutionized astronomy; virtually every large telescope, including the Hubble Space Telescope, uses CCDs because they are about 100 times more sensitive than photographic film and work across a much broader spectrum of wavelengths of light. CCDs have created entirely new industries (for example, video cameras and camcorders). To this day, Boyle and Smith continue to receive awards for their invention.
In 1975, Boyle returned to research as executive director of research for Bell Labs’ Communications Sciences Division in New Jersey, where he was in charge of four laboratories until his retirement in 1979. Since then he has served on the research council of the Canadian Institute of Advanced Research and the Science Council of the Province of Nova Scotia.
In the late 1920s, when Boyle was about three, his family moved from Nova Scotia to Quebec, where his dad was the resident doctor for a logging community called Chaudiere, about 350 kilometres north of Quebec City. Instead of a car, they got around by dog sled. Boyle received no formal education and was home-schooled by his mother until high school.
One evening, when Boyle was about eight years old, his father asked him to go feed the huskies. The dogs made a lot of noise barking, so they lived in a kennel about 100 metres from the house. Boyle was bundled up in a winter parka, given a bucket of dog food and a small kerosene lantern and sent out into the cold, dark night. There was lots of snow and trees and an absolutely black sky, with no moon or stars. The place had no electricity and no electric lights. “It was terrifying to be in the little circle of light from my kerosene lamp, surrounded by the utter cold, black void,” says Boyle. “I had this feeling: I’m a person alone, and if I’m going to get through this, there’s only one person that’s going to do it and that’s me.” As it turned out he accomplished his task without incident, but the primal fear he felt that night stayed with him all his life.
In grade 9 he went to Lower Canada College, a private school in Montreal. The contrast of coming from the backwoods to join the children of the upper class was jarring, but Boyle did very well, partly because of the many books he had read under his mother’s guidance.
After high school Boyle joined the Royal Canadian Navy to fight in World War II, but boats made him seasick, so he applied to the Fleet Air Arm of the navy and was sent to England to learn how to land Spitfire fighter planes on aircraft carriers. Boyle was about 19 years old when he found himself piloting one plane among a small squadron of about three other Spitfires; after weeks of practising landings on an imaginary aircraft carrier painted on a conventional runway, the young pilots were now attempting their first landing on a real ship at sea. Boyle watched from the air as, one after the other, his friends crashed their planes onto the flight deck, or missed the boat completely and ditched in the sea. Fortunately, no one was hurt.
Now it was Boyle’s turn. He thought back to that cold, dark night in the woods and said to himself, “Well, you’re on your own here again. No one is coming to help you. Let’s go for it.” He made his turn onto final approach, set up his glide path and headed directly for the large white stripes on the deck. Nobody was more surprised than Boyle when he made a shaky but passable landing. He shut off the engine, raised the cockpit cowling, whipped off his helmet and was wiping the sweat from his brow as he began climbing down when his commanding officer walked up and shouted, “What are you doing, Boyle?”
“I landed it!” yelled Boyle, triumphantly.
“Get back in that cockpit and take off immediately, officer. You do seven more if you want to qualify.”
Boyle dutifully completed his pilot training, but the war ended soon after and he never saw active combat. He went on to earn his doctorate in 1950 and three years later he joined Bell Laboratories.
Boyle’s branch of science is called solid state physics or condensed matter physics, and it involves the behaviour of materials that are solid — things such as crystals, metals and rocks. In particular, he worked on semiconducting materials such as the element silicon. He invented many things while at Bell Labs, but his most famous invention was the Charge Coupled Device or CCD.
1. At the heart of many camcorders and digital cameras is a charge coupled device (CCD), typically about a square centimetre in size.
2. Light in the form of incoming photons enters through the lens of the camera and falls onto the surface of the CCD chip, often passing through a colour filter array. This generates free electrons in the silicon of the CCD, more where the light is brighter and fewer where it is less intense. These electrons collect in little packets created by the geometry of the silicon and surrounding electrical circuitry, laid out in a two-dimensional grid on the chip. Typical CCD chips have from one to five million such packets of charge, which can also be pictured as buckets on a conveyor belt.
3. The CCD operates on the principle of charge coupling. The packets of charged electrons can be moved one row at a time by varying the voltage of adjacent rows, thereby creating a potential well that couples two rows and causes the charge to move over.
4. Imagine buckets on conveyor belts catching falling rain, to represent photons of light. Each bucket (packet) contains a different amount of water (charge), depending on how much rain fell on that part of the array. The buckets are shifted in an orderly fashion to a collecting row, then to a final measuring device at the front. In this way the quantity of water in each bucket is counted. In a typical CCD this can happen very fast: about 30 times per second for every one of millions of “buckets” on the CCD.
Modern CCDs have colour filters (red, green, blue) arranged in a pattern over the chip so that colour images can be collected. The output of the CCD is a string of numbers that define the intensity and the colour of light over the entire image. A computer or camcorder can store these numbers or use them to recreate the image on any kind of viewing screen or printer. For more on how a CCD works visit the Molecular Expressions website.
In recent years, complementary metal oxide semiconductor (CMOS) imagers are replacing CCD chips in some imaging devices. These are not based on the CCD principle but are rectangular arrays of individually addressable pixels. CMOS is the dominant technology for all microchip manufacturing, so cmos image sensors are cheaper to make. In addition, supporting circuitry can be incorporated onto the same device in a single manufacturing process. CMOS sensors also have the advantage of lower power consumption and better infrared sensitivity, or heat imaging, than CCDs. However, for many high-end cameras and camcorders a CCD is still preferred because of its sharper, cleaner images for most photographic applications.
Boyle expects that many cosmological mysteries will yield their secrets due to the superior imaging power of CCDs, which are now used in virtually every telescope. “We’re going to see much greater understanding of the origin of our universe by having the ability to see things that are eight billion light-years away,” he says. “The mother of all mysteries is the origin of the universe.”
James R. Janesick, Scientific Charge-Coupled Devices, SPIE Press Monograph, vol. PM83, 2001.
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