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July 25th, 2012
New technology could make projectors more compact, energy-efficient
New technology from researchers at North Carolina State University and ImagineOptix Corp. might make smart-phone projectors as common as smart-phone cameras.
Tiny digital projectors, called pico projectors, have appeared already in smart phones like the Samsung Galaxy Beam, which has a 15-lumen output and can project up to 50 inches at a 640 x 360 resolution—but now researchers have developed a much more efficient process to polarize light in liquid crystal (LC) projectors to reduce light loss and thus heat.
“This technology, which we call a polarization grating-polarization conversion system (PGPCS), will significantly improve the energy efficiency of LC projectors,” explains Michael Escuti in a media release. “The commercial implications are broad reaching. Projectors that rely on batteries will be able to run for almost twice as long. And LC projectors of all kinds can be made twice as bright but use the same amount of power that they do now.”
Escuti is the co-author of a paper describing the research and an associate professor of electrical and computer engineering at N.C. State.
The new process will allow even more compact design in standard projectors and also will reduce the dependence on those annoyingly loud cooling fans, Escuti said.
All LC projectors—used from classrooms to conference rooms—use polarized light. But efficient light sources—such as light-emitting diodes, or LEDs—produce unpolarized light. As a result, the light generated by LEDs has to be converted into polarized light before it can be used.
The most common method of polarizing light involves passing the unpolarized light through a polarizing filter. But this process wastes more than 50 percent of the originally generated light, with the bulk of the “lost” light being turned into heat—which is a major reason that projectors get hot and have noisy cooling fans.
The new technology developed at N.C. State allows approximately 90 percent of the unpolarized light to be polarized and, therefore, used by the projector.