X-rays give a good picture of what condition bones are in because they travel straight through tissue and come out the other side. Since they harm the tissue at the same time, though, doctors don’t like to use them too often. Light rays would be a safer alternative, but they scatter so wildly on their way through tissue that you can’t tell where they came from and thus can’t make a picture of where they’ve been.
Jack Feinberg, a physicist at the University of Southern California in Los Angeles, recently found a way to use light to make X- rays. It turns out that some, the ballistic light rays, manage to make it straight through tissue and out the other side. The problem Feinberg faced was how to distinguish ballistic light from scattered light. Since ballistic light goes through tissue in a straight line, he reasoned, it travels the shortest distance, reaching the film a few trillionths of a second ahead of scattered light. If you want to look at the light that comes out first, you make a fast shutter, says Feinberg. But you can’t use mechanical shutters, because they’d have to move faster than the speed of light. Feinberg, a laser maven, decided instead to record all the light coming through the tissue, keeping track of when it hit the film.
To do this, he and Alex Rebane, an expert in low-temperature materials from Estonia’s Academy of Science, created what they call a temporal hologram. First they impregnated a very cold piece of plastic with a light-sensitive dye. Then they directed a laser through a material that simulated living tissue, making an image on the film behind the material. They also shone a second laser beam directly at the film, timed to arrive after the ballistic light but before the scattered light. The second beam altered the interference pattern recorded in the film in such a way that the images recorded before and after the beam hit the film appeared in different places.
Although Feinberg and Rebane have proved the technique’s feasibility, they still need to figure out how to get the light through tissues thicker than 1 centimeter, which turns out to be a tough problem. We’re going to need some other trick before this is going to be medically useful, says Feinberg.
University of Cincinnati’s Virtual Reality Cave of Lascaux
Innovator: Benjamin Britton
You are deep in a cave filled with Paleolithic paintings, etchings, and sculptures. You wander through the Chamber of Engravings, the Chamber of the Felines, the Hall of the Bulls. A picture catches your eye, and you turn to study it. Suddenly the bull springs to life before your eyes.
This is Benjamin Britton’s virtual reality Cave of Lascaux as seen through a virtual reality headset. The real cave, discovered near the Dordogne region of France in 1940, was closed to the public in 1963 because the wear and tear of 100,000 visitors a year threatened to destroy the artwork. In 1990, Britton, himself an artist, set out with his futuristic tools to capture the ancient paintings. It’s a blend of art and science, says Britton, assistant professor of fine art at the University of Cincinnati. It brings the spirit of humankind and the practical innovations of science and technology together in a way that helps us understand who we are.
Britton didn’t even get the chance to visit Lascaux until the project was nearly finished: he pieced his virtual cave together using high-resolution photographs. Since no software was available to help create the virtual reality, Britton and his brother David had to devise their own. Indeed, Britton left no technological stone unturned in his pursuit of realism. The virtual traveler who dons the head-mounted display sees more than a mere 3-D reconstruction of the cave. If he stares at a painting for a few seconds, artificial intelligence software kicks in a video clip of the real animal. Virtual Lascaux is not for sale but will travel to museums around the world for three years before finding a permanent home in France.
One Small Leap
Minolta Planetarium Company’s Infinium Cosmoleap
Innovators: Masamitsu Hattori and Kenji Shiba
When it comes to planetariums, Earth is still the center of the universe. But the night sky looks different from Jupiter, Mars, or the moon.
The newest planetarium from the Minolta Planetarium Company in Osaka, Japan--the aptly named Infinium Cosmoleap--allows you to travel the solar system and take a good long look from the sun, the moon, or any of five planets. Claiming to be the world’s smallest planetarium, Cosmoleap consists of two spheres and two light sources that rotate on three axes, simulating the daily rotation of the sky as well as changes in latitude and direction. All you need is a dome 26 feet in diameter--a big space savings over the conventional 49-foot planetarium dome and small enough for universities and even high schools to host their own stargazing events.
To keep things as small and inexpensive as possible, Minolta engineers Masamitsu Hattori and Kenji Shiba designed Cosmoleap to be controlled by a personal computer. A click of the mouse or a touch of the screen gives you more than 6,500 stars. Since the software contains the most current star catalog, it can calculate any planet’s position relative to any other for any date. You can even hop aboard the Space Simulator Module and watch the backdrop of stars shift as you fly through the solar system. Minolta has not yet made any moves to market the planetarium in the United States, but the firm has already sold three in Japan.
It's All Done With Mirrors
Texas Instruments’ Digital Micromirror Device
Innovator: Larry Hornbeck
Digital video made headlines last year when the first digital television broadcasting satellite began transmitting across the country. Since nobody has digital television sets to match, however, the promised improvement in picture quality was hidden in the shadowy, fuzzy, decidedly analog cathode-ray tube.
Texas Instruments took a big step toward popularizing digital display with the demonstration last year of a computer chip called the digital micromirror device, or DMD. When linked with a light source and a couple of lenses, the DMD should greatly simplify the design of digital displays. Embedded in the fingernail-size chip are 442,000 tiny mirrors, each about 16 square microns, or millionths of a meter--so small that a grain of salt would cover 100 of them. Each mirror reflects a beam of light onto a designated spot on the television screen. TI engineers cleverly designed each mirror so that it can tilt in two directions--toward or away from the screen--which neatly corresponds to the zeros and ones of digital data.
Indeed, the DMD acts as a native speaker of digital data: it takes the digital broadcast signal and, without having to translate it into an analog signal, uses it to direct light to the screen. Since the mirrors are lightning fast, they can make any spot on the screen brighter by directing light to it several hundred times during a single frame, or dimmer by directing the light away.
When products incorporating the DMD reach the market next year, their better image quality should be apparent. We didn’t really anticipate that we were going to bring this thing to market at about the time that digital video transmission was going to come into vogue, says TI engineer Larry Hornbeck, who invented the DMD in 1987 and has been developing it ever since. But this is the digital revolution, and the digital micromirror device is fitting into that very nicely.
Seeing in the Dark
Hughes Aircraft/Texas Instruments’ Nightsight Thermal Vision System
Innovator: George Hopper
High-tech as it sounds, the technology of night vision has been around since the 1960s. But originally the sensors that picked up infrared radiation from warm objects worked only at extremely low temperatures. They were too expensive for anyone but the military.
That’s changed, however. Police are now using night vision to catch criminals, thanks to Hughes Aircraft of Torrance, California, and Texas Instruments. George Hopper, a physicist and retired TI engineer, invented a new infrared sensor that works at room temperature. He started by searching for a material whose electrical properties changed in the presence of infrared radiation and that didn’t need to be cooled to absurdly low temperatures. He hit on a ceramic called barium-strontium- titanate. An infrared image falling on a slab of the material alters its capacitance. By measuring these changes at each point on the ceramic, Hopper found he could capture the image electronically. Using his device is just like watching television, says Hopper, except there’s no light whatsoever.
Since the device needs no cooling system, TI and Hughes were able to squeeze it into a package only a foot long and sell it for $7,000--less than a quarter the price of devices using the old technology. The product, called Nightsight, should be cheap enough for the more well heeled municipal police departments, which could use it for spotting still-warm discarded weapons and stolen cars as well as finding criminals in the dark.