Bi-stable display technologies such as Eink are useful because they consume little or no electricity when the image does not change. On the other hand, LCDs are attractive because you can make small pixels and create different shades of gray to create photo-style images. Sharp has a technology that combines the best of both worlds, which the company calls “Memory LCD.” These displays are different from traditional LCDs because in addition to a transistor for each pixel, the panel also has a memory component that stores the information for each pixel. As a result, the screen does not have to be constantly refreshed by the display controller, as is required by standard LCD panels. The controller can be shut down — just as with a bi-stable display — until it is needed to write a new image on the screen. Sharp makes several panels that use this technology, including an octagonal display that is about one-inch across. It has a 128 by 128 pixel resolution, which is sufficient for a smart watch or similar wearable application. The impressive part is that while it requires 45 mW of power to refresh the image, it only draws 10 mW of power when the image does not change. It uses transflective technology so that it is easy to read under bright conditions such as direct sunlight. While this technology is a few of years old, it has the opportunity to come into its own now that the wearable market is taking off. Sometimes it takes a while for product requirements to catch up with the available technology.
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