London, July 23 : Building the pixels of flat-panel displays like tiny telescopes, similar to a design invented by Isaac Newton, could make them much more power efficient, or make screens easier to read in direct sunlight.
Though today's dominant display technology is the thin, cheap and durable liquid crystal display panel (LCD), the bulk of the light created by a screen's backlight is wasted, and never reaches the viewer.
The rear layer of an LCD produces light that passes through individual pixels, whose brightness is controlled by small liquid crystals that swing round like tiny shutters.
They allow at most only 10% of light to pass. A majority of that light never reaches the viewer either, being absorbed by polarising filters and the outer layers of the screen.
Now, according to a report in New Scientist, swapping the liquid crystals for microscopic mechanical mirrors arranged in a similar way to a telescope design invented by Isaac Newton can make much more efficient use of a backlight.
Anna Pyayt of the University of Washington, Seattle, worked with engineers at Microsoft to create the new "telescopic pixels."
Each circular pixel has a thin metal mirror 100 microns facing back towards the display's backlight, with a 40 micron hole in the center. A second mirror is positioned below and is slightly larger than the hole.
When a telescopic pixel is dark, the main mirror is flat. Both mirrors bounce light back to the backlight, away from the viewer.
But when a voltage is applied to the main mirror, it bends into a parabolic shape, focusing light onto the second mirror and out through the hole.
To the viewer the pixel appears lit up.
Telescopic pixels can let 36% of a backlight's output pass, compared to the puny amount allowed past by the crystals of an LCD.
"You could build a brighter monitor for the same amount of energy or use less energy to get the same brightness," Pyayt told New Scientist.
Telescopic pixels can also switch on and off around twice as fast as a typical TV LCD, in around 1.5 milliseconds.
That means an image can be changed faster, preventing blurring of fast-moving objects.
Faster switching could also cut the need for separate red, green and blue pixels made using filters laid over a pixel. Instead, a single beam of light that changes colour could be teamed up with a quick-switching telescope pixel.
Each pair could rapidly produce the output of three separate LCD pixels in sequence, fast enough to fool the eye.