LCDs Have a More Efficient Competitor

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seem to be a few reasons that stop the liquid crystal display fromoffering the best image quality. The first of them is that thepixels in a LCD do not turn completely off. Besides that, they needan average of about 25 to 40 milliseconds to switch from black towhite and otherwise, which creates a blurring effect on fast movingimages.

Another very important reason for the lack of performance LCDs comewith is the fact that they are almost impossible to use in brightlight. "There is nothing in LCD technology that stands out," saysSriram Peruvemba, vice president of marketing at electronic-paperpioneer E Ink, based in Cambridge, MA. "The only reason it has donewell is it's the lowest price [flat-panel] display today."

While the LCD displays prove to be faulty in many aspects, the newtelescopic pixels have more performance. Firstly, they have theability of completely turning off, and that in only 1.5milliseconds. The ultra fast response time means that the colordisplay will be simpler and cheaper, says Michael Sinclair fromMicrosoft Research.

In order to create a specific color, a pixel in LCDs lights upsimultaneously at different intensities three subpixels: red, greenand blue. There is also a separate transistor circuit that controlseach subpixel, and that translates into a complex circuit. For thetelescopic display, red, green and blue light emitting diods can beput behind each pixel and they would be lit up sequentially tocreate a color shade. Sinclair says that, this way, "complexity andcost of today's LCD" would be reduced.

The novel pixel design is a few times brighter then LCD

Another important feature of the telescopic pixels is thesignificantly higher brightness they offer. The LCD has only fiveto ten percent of the light coming out, as it has to pass throughthe polarizing films, the liquid-crystal layer, and the colorfilters. With the telescopic pixels, about 36 percent of lightwould be allowed to come through. "I could get by with aless-powerful backlight, because the telescopic pixel is moreefficient," Sinclair says. Having a greater brightness would allowthe novel pixel design to be more efficiently used in brightsunlight.

Two micro mirrors are used by the new pixels to block or let thelight pass. One is an aluminum disc 100-micrometer-wide and100-nanometer-thick which has a hole in the center. The other isplaced right in front of the hole and has the same dimension. Thelight is projected from behind the second mirror on the disc shapedone. While the pixel is in the "off" state, both mirrors send thelight back to the source. In the "on" state, the light bounces tothe second mirror and then comes out through the hole.

The pixels are fabricated by the researchers in a layered fashion,similar to the way silicon chips are manufactured. According toSinclair, the telescopic design needs fewer layers, which means itis simpler to fabricate than LCDs. The disc shaped mirror is bentby a small voltage applied to an electrode, which is made fromindium titanium oxide at this moment, an industry standard. Still,they consider making the electrodes from an extremely thin aluminumlayer that would become nearly transparent. The production processwould be simplified, and the costs lowered even more.

According to Peruvemba, although the new pixel technology presentsadvantages over today's LCDs, the mechanical parts are likely tocompromise robustness. "There are literally hundreds of thousandsto millions of little shutterlike devices that have a mechanicalmovement," he says. "In most devices, what fails first are themechanical parts."

Other ideas in the field have also appeared to the surface. WhileLCD and the new telescopic display have a backlight from which theytransmit light, others came up with a display that reflects ambientlight. Qualcomm has a new display with MEMS-based pixels set forlaunch this year on three different cell phones, and has announceda color screen for an MP3 player. E Ink, a black-and-white e-paperdisplays seller, also announced color and video prototypes.

Compared to LCDs, these displays do not need backlight and constantrefreshing. The screen looks even better when more light is aroundit. "We're not competing with bright ambient light--we're takingadvantage of all that sunlight," says Brian Gally, director ofengineering at Qualcomm MEMS Technologies. "So it's reallyanalogous to paper."

According to Sinclair, Microsoft Research aims at large, low-costcomputer screens. He says that any IT worker dreams of one. Therewill not be a small screen on which you would have to togglewindows, but a "whiteboard-sized thin screen" to work on.