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From IEEE Spectrum:
Researchers from Microsoft say they've built a prototype of a display screen using a technology that essentially mimics the optics in a telescope but at the scale of individual display pixels. The result is a display that is faster and more energy efficient than a liquid crystal display, or LCD, according to research reported yesterday in Nature Photonics.
Anna Pyayt led the research as part of her Ph.D. thesis at the University of Washington in collaboration with two Microsoft engineers. Microsoft funded the work and has also applied for a patent on the technology.
The most common display technology, the LCD, is inefficient. The display is lit from the back, and less than 10 percent of the light reaches the surface of the screen. Pixels in a display technology work as on-off shutters, but the light has to travel through several layers before reaching the screen. In an LCD, one of those layers is a polarizing filter, which absorbs about 50 percent of the light as it passes through.
By contrast, the telescopic pixel design uses reflective optics. Each pixel functions as a miniature telescope. There are two mirrors: a primary mirror facing the backlight (away from the screen) with a hole in the middle, and a smaller secondary mirror 175 micrometers behind the primary mirror it faces. The secondary mirror is the same size and shape as the hole. Without an electric field, the mirrors stay flat, and light coming from behind the pixel is reflected back, away from the screen. But applying voltage bends the primary mirror into the shape of a parabola. The bending focuses light onto the secondary mirror, which reflects it out through the hole in the primary mirror and onto the screen.
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