1997 Discover Awards: Sight: Revealed Weapons

Tuesday, July 01, 1997
RELATED TAGS: WEAPONS & SECURITY
WINNER: Sandia National Laboratories’ Compact Cadmium Zinc Telluride Sensors

INNOVATOR: Ralph James

Drums of plutonium from dismantled atomic weapons, sitting in a government site in Amarillo, Texas, are protected from theft by a sort of high-tech sentry. Attached to each container is a hockey-puck-size sensor that monitors the gamma rays emitted by the waste. Since each type of radioactive substance gives off gamma rays of a characteristic energy, the sensor can tell precisely what kind of radioactive material is contained within, and how much.

The sensors were installed in December 1996, but they are the result of a decade-long effort by Ralph James, a physicist at Sandia National Laboratories in Livermore, California. Back in 1986, when he started, you couldn’t detect a single gamma ray without germanium crystals bathed in liquid nitrogen and hundreds of pounds of expensive cryogenic equipment. James was looking for something that could form the basis of a cheaper detector. He knew that gamma rays trigger tiny electric currents in the compound cadmium zinc telluride (czt), even at room temperature. At the time, however, the typical czt crystal generated so many spurious electric signals that they drowned out any signal generated by a gamma ray. Then in 1988, a group of scientists in Ukraine found a way to grow czt crystals that didn’t have the spurious signals. It took another couple of years to make a crystal that had good transport properties--meaning the crystal has no defects that can block the electric signals from the gamma rays. From there it was a matter of learning how to make big crystals--the bigger the volume of the crystal, the more gamma rays it will detect.

Since his sensors are compact and work at room temperature, they could be used not only for monitoring plutonium but also for detecting environmental radioactivity, exploring for minerals, and helping doctors find tumors. James recently managed to make crystals that are five cubic centimeters in volume, and now he is aiming for crystals twice again as large--at that size, they could spot cancer tumors, tagged with a radioactive substance, that are as small as a millimeter across.

Finalists

Layers of Light

Brookhaven National Laboratory’s Polyplanar Optic Display

INNOVATOR: Jim Veligdan

One evening in 1993, Jim Veligdan was sitting at his desk reading an optics textbook. It’s not that he needed to study the material--he’s an optical engineer at Brookhaven National Laboratory in New York. But sometimes textbooks give him inspiration for new projects, and on this occasion a section on how light flows through an optical fiber caught his eye.

If a hair-thin glass fiber is coated with a material that reflects light, the light bounces down the fiber like water in a pipe. Any light entering at one end will flow through the fiber until it comes out the other end, even if the fiber is curved. What if, instead of fiber, Veligdan wondered, you were to use thin, flexible sheets? A fiber gives you just a point of light, but a sheet, with its long edge, would give you a line. In theory, he realized, you should be able to make large-scale television screens or computer monitors only a few inches thick. It took Veligdan only two months to whip up a prototype. All it did was shine a little red circle, he says, but it was enough to prove it would work.

In essence, Veligdan’s polyplanar optic display is a projection device. Instead of sending light from the back of a theater through the air to the screen, light is generated at the bottom of the screen by tiny solid-state lasers and sent upward through several hundred light sheets made of transparent plastic coated with a cladding that reflects the light and keeps it in the sheet. All the sheets are three-hundredths of an inch thick and four feet wide, but each one is a different height, and they are stacked in ascending order, like stair steps. Light reaching the edge of a sheet creates a single horizontal row of the image.

Last January, four years after that textbook moment, Veligdan produced a small prototype screen for the U.S. Air Force with the resolution of a standard computer monitor. His next project is to make a six-foot model suitable for tv but only a few inches thick. Since the screens could be curved, Veligdan thinks they could make a new type of instrument panel for airplane cockpits or a wraparound home entertainment screen. And since light can travel both ways through the screen’s light sheets, it might be possible to set up an interactive system that responds to a laser pointer wielded by a viewer.

Still Pictures, Only Better

Canon, Fuji, Kodak, Minolta, and Nikon’s Advanced Photo System

INNOVATORS: Kazuya Hosoe, Akikazu Mikawa, William Atkinson, Mikio Naya, Naoki Tomino

When engineers from Kodak, Fuji, Canon, Nikon, and Minolta got together in 1991, their only goal was to find ways to make life easier for the amateur photographer. It certainly wasn’t our plan to replace 35mm products, says Bill Atkinson, an engineering manager at Kodak. But when they drew up a wish list, it was obvious that the old format couldn’t accommodate it. So they gambled.

The Advanced Photo System, which made its debut in February 1996, is a constellation of new products--new film, cameras, and photo-processing equipment--that pass digital information back and forth among them. Some changes are immediately visible. The film cartridge, for instance, is smaller and has no leader sticking out. You simply drop it into the camera, and when you close the camera, the film is automatically spooled. If you open the camera in the middle of a roll, the film automatically spools safely back into the cartridge. Later, when you reload the same roll of film, the camera can automatically advance to the frame where you left off.

The real advantages, however, lie in the system’s memory. Each time a picture is taken, the camera records information on the film’s magnetic strip. Depending on the camera model, this data can include the date and time, details of the natural lighting or flash, and even the distance of the subject from the lens. When the film is developed, photo processing equipment uses this information to make adjustments and prints the information on the back of each picture. The magnetic strip also tells the processing machine which format to use for each print--the standard 31Ž2 by 5 inches, a slightly wider 31Ž2 by 6 inches, or a panoramic 31Ž2 by 101Ž2 inches. The negatives come back from the developer still nestled safely in the original cartridge.

Moving in Three Dimensions

Lawrence Livermore National Laboratory’s 3-D Motion Camera

INNOVATOR: Shin-yee Lu

Since last fall you may have seen the television advertisement in which a baseball flies straight at you and sprouts a face that screams Sega! Think of it as a peace dividend from the end of the cold war. The screaming baseball graphics were created with a three-dimensional motion camera developed at one of the nation’s top defense laboratories.

The project started in 1992 as a way to help robots grasp and manipulate three-dimensional objects. Humans can perceive 3-D because each eye scans a scene from a slightly different angle while the brain integrates the two images to produce an impression of depth. Robots, however, had no good way of matching up the two images. Shin-yee Lu, a Lawrence Livermore National Laboratory engineer, got the idea of exploiting the different textures of objects in the video frame as a guide for matching the images. Her technology worked well enough so that robots could handle nuclear waste. For robotics, you just need to know roughly the size and the location of something, she says.

Then a medical research clinic asked Lu if her technology could capture the abnormal physical movements of cerebral palsy patients for further analysis on a computer. It could not, she said. The images were too crude for the subtleties of human anatomy. But she soon realized that the resolution could be improved dramatically by projecting a series of narrowly spaced lines on a subject. A computer could then match the two stereo images by using the lines as a frame of reference.

Once it watched the images, the computer was able to figure out the shape of each object and to manipulate the images afterward, which is how the baseball came to sprout a face. That capability may also come in handy for face-recognition security systems, virtual-reality software, and computer-animated films.

Crystal Cube

3-D Technology Laboratory’s

Three-Dimensional Cube Display

INNOVATOR: Elizabeth Downing

In trying to display convincing 3-D, inventors have chiefly resorted to tricking the eye and brain into believing that one or more two- dimensional images are really solid objects. Back in 1988, Elizabeth Downing hit upon a method of creating something closer to reality.

Downing, chief executive of 3-D Technology Laboratory in Mountain View, California, realized that atoms of certain rare earth elements will absorb two slightly different colors of invisible infrared light and reradiate the energy as visible light. If you could impregnate a cube of glass with these atoms, she reasoned, and sweep two beams of infrared laser light through the cube, you could create points of light wherever the beams crossed. Sweep many beams through the cube rapidly enough and the eye would perceive those points of light as the surfaces of three-dimensional objects, much the way the individual pixels of a tv screen create two- dimensional images.

For almost nine years Downing worked to iron out one problem after another. She found she couldn’t build her cube out of ordinary glass, because the glass’s silicon dioxide molecules would hold the rare earth atoms too tightly--every time an atom absorbed a photon, the energy would dissipate through the network of molecules as heat. By using a type of glass made out of fluoride rather than silicon, she got looser structures that kept the rare earth atoms isolated. She still had years of fiddling to get the whole thing to work. There were so many reasons I should have given up and tried to do something easier, she says, but I couldn’t let go of it, because the basic concept is so simple.

Her persistence paid off last August, when she unveiled a prototype 3-D cube, about one inch high. Since then she’s been busy creating tiny 3-D line drawings of the Statue of Liberty, to get a feel for what her invention can do. She formed 3-D Technology Laboratory in 1995 to commercialize the technology. So far a few government agencies have expressed interest in sponsoring further research for medical imaging, air traffic control, radar, and other applications that might benefit from a display that shows three honest-to-goodness dimensions.
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