LONDON Because liquid crystal display (LCD) pixels are relatively large it is possible to integrate memory in the active memory backplane at each pixel site. Sharp Corp. has done this for a 96 x 96 pixel miniature monochrome LCD and claims a power saving of a factor of 130 compared to standard LCDs of equal size.
By including a memory at each pixel data only needs to be sent to the display as content changes from frame to frame. For most LC displays a microcontroller has to rewrite the complete screen content from frame to frame at a rate of 50- to 60-Hz even though most, or all, of the image remains the same. And it is this redundant data transmission that can waste a lot of energy.
Sharp said that its memory-LCD of 1.35 inches diagonal size consumes about 15-microwatt in operation whereas a standard LCD of comparable size needs about 2-milliwatt to render an image.
The memory-LCD has been developed based on Sharp's proprietary Continuous Grain Silicon technology. As a result, and differently from other reflective displays, the new type of LCD does not need polarisers. Thanks to a special liquid crystal material the image is generated by the status of the pixel just changing from black to white with a reflectivity of 50 percent. As a result of the low power consumption small-size solar cells can provide enough electricity to drive memory-LCDs, Sharp said.
The display is therefore suitable for portable applications such as wrist watches, heart-rate meters and other fitness devices and price tags. Samples of the memory-LCD are available starting Q2 2009.
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