Researchers in Switzerland are developing a new nano technology they claim will double the range of colors that future TVs can produce — displaying every hue the human eye can see.
By comparison, most of today’s TVs — be they plasmas, LCDs or projectors — display only about half the visible colors.
“Current displays do not faithfully reproduce the hues of blue one can see in the sky or in the sea,” said Manuel Aschwanden, who developed the new technology with Andreas Stemmer at the Swiss Federal Institute of Technology.
Their invention uses diffraction grating — a series of fine parallel grooves — bonded to a flexible material, known as an elastomer, that stretches when voltage is applied.
Most diffraction gratings are fixed. When white light hits the grating, it splits into a rainbow of its constituent colors. A common example is the rainbow that shines off a CD or DVD: fine pattern of data tracks, by coincidence, produces a diffraction grating.
But Aschwanden’s and Stemmer’s stretchable grating changes the size and spacing of the grooves when it flexes so that it can be tuned to reflect different colors. A recent article for the Optical Society of America describes the details of the researchers’ “artificial muscle.”
A grid with millions of these tiny tunable diffraction gratings could reflect a full-color, high-definition image to beam onto the screen of a TV. Aschwanden believes it is also possible to pass light through a flexible grating in order to make flat-panel TVs that compete with LCD and plasma sets — and that expands the number of colors used to paint an image.
Most of today’s TVs and computer screens form images by varying the intensity of just three primary colors: red, green and blue. Bright yellow, for example, is composed of equal parts red and green, with no blue component. That works pretty well, but not as well as actually producing yellow light.
TV makers are already expanding their color palettes. Last year Texas Instruments introduced a DLP projection technology called BrilliantColor (.pdf) that augments the typical red, green and blue color flashes with up to three others: cyan, magenta and yellow. Mitsubishi and Samsung, among others, use the technology in some TV sets.
It’s also possible to produce 6-color LCD panels, according to Karl Lang, an engineer who has designed monitors and color-management systems for the professional graphics business. As LCD screen resolution continues to increase, designers have a choice, according to Lang: increase the spatial resolution with more red-green-blue pixels per screen, or increase the color resolution by packing more primary colors into each pixel.
Along with providing additional colors, however, the tunable diffraction grating system also improves their intensity. In most LCDs, for example, the fluorescent backlights and color filters in the screen produce only so-so shades of red, green and blue — limiting the range of colors they can make.
The tunable diffraction grating will use a white light-emitting diode, said Aschwanden, to provide the full spectrum of visible light. Some LCDs currently on the market have LED backlights that increase the color gamut by up to 30 percent, according to Lang. But the tunable diffraction grating could raise it by about 100 percent.
Despite the promise, the tunable diffraction grating system faces many challenges. One is efficiency. Current prototypes require up to 300 volts to stretch the elastomer. Adjusting LCD pixels takes at most about five volts.
Response time is another issue: The tunable diffraction grating currently can’t change color at 60 times per second like LCD, plasma and projection sets. Aschwanden is optimistic about improving speed, but he doesn’t know for sure what can be done.
“The maximum response time I cannot tell you,” he said.
Karl Lang was skeptical about the ability of these artificial muscles to flex the hundreds of millions of times required over the lifetime of a TV.
“The idea that an elastomer can do this without breaking down is hard to believe,” said Lang. But Aschwanden said the pixels have already been shown to survive for at least hundreds of thousands of cycles.
The biggest challenge, however, may be time. Aschwanden estimates that his system could appear in commercial products in about eight years, with significant funding. A lot can happen to other technologies in the meantime.
“LCD just has huge legs,” said Karl Lang. “We know where we’re going with it for the next 10 years.”
This story is licensed from Wired Magazine
