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Reflective Displays Allow Reading In The Dark

By John Teresko If your electronic book had the latest cholesteric reflective display from Kent, Ohio-based Kent Displays Inc., venues for reading the latest Harry Potter epic could range from the bright sunlight to the dead of night. In sunlight the newly patented panel presents a bright, vivid image (remember it's reflective). At night, by reflecting infrared frequencies, panel images are visible to anyone wearing night-vision goggles. An electronic book for the military is the initial application, says Gene Miceli, president. Also possible: signage that could only be seen by those wearing night-vision goggles. Honeywell Corp. is Miceli's partner on the e-book project. The high contrast cholesteric displays feature a bistable, nonvolatile memory feature. Once an image is written, it remains indefinitely, without power, until a new image is generated. Miceli says the displays exhibit high contrast due to the reflective nature of the Cholesteric fluid. A display cell acts as a collection of tiny mirrors, each reflecting 50% of incident light. The total amount of light reflected is affected by the limited bandwidth, angular distribution of the mirrors, and depolarization of the light within the cell. The resulting total reflection approaches 40%. While underperforming paper (which reflects at least 80%), cholesteric displays substantially outperform other reflective displays, says Miceli. Currently the displays are made in monochromatic format with a choice of four standard color configurations. Multicolor and full color are coming, adds Miceli.

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