Polarizing filter reduces energy drain from smartphone displays
Polarizers are indispensable in digital photography and LCD displays, but they block enormous amounts of light, wasting energy and making it more difficult to photograph in low light.
The Utah electrical and computer engineering researchers created the filter by etching a silicon wafer with nanoscale pillars and holes using a focused gallium-ion beam. The new concept in light filtering can perform the same function as a standard polarizer but allows up to nearly 30 percent more light to pass through, explained University of Utah electrical and computer engineering associate professor Rajesh Menon. The study is being published in November’s issue of Optica, a new journal from The Optical Society.
Sunlight as well as most ambient light emits half of its energy as light polarized along a horizontal axis and the other half along a vertical axis. A polarizer typically allows only half of the light to pass because it is permitting either the horizontal or vertical energy to go through, but not both. Meanwhile, the other half is reflected back or absorbed, but the resulting image is much darker. Polarizers are widely used by photographers, for example, to reduce glare in the image. They also are used in LCD displays to regulate what light passes through to create images on the screen.
“When you take a picture and put the polarized filter on, you are trying to get rid of glare,” explained Menon. “But most polarizers will eliminate anywhere from to 60 to 70 percent of the light. You can see it with your eyes.”
With the new polarizer, much of the light that normally is reflected back is instead converted to the desired polarized state. The University of Utah researchers have been able to pass through about 74 percent of the light, though their goal is to eventually allow all of the light to pass through.
LCD displays on devices such as smartphones and tablets have two polarizers that ultimately throw away most of the light when working with the liquid crystal display. “If one can increase that energy efficiency, that is a huge increase on the battery life of your display. Or you can make your display brighter,” said Menon.
Menon’s team validated their concept using a polarizer that is 20 by 20 micrometers and tested with only infrared light. But they plan to increase the size of the filter, use it with visible light, and figure out a way to make it more cost effective to manufacture.
Related articles and links:
https://unews.utah.edu
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