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Imagine a 3-D LCD display on your e-book that hardly ever needs recharging because it draws power only when you turn it on or when you go to the next page.
Stop imagining. Researchers from the Hong Kong University of Science and Technology have come up with an ultra-thin LCD screen capable of holding 3-D images without the benefit of electricity. The only unexciting thing about the device is that, for now at least, it’s limited to gray scale and its refresh rate is too slow to allow displaying video.
LCD screens, which are used in everything from digital watches to television screens, conventionally are made up of liquid crystal molecules that are held between plates of polarized glass. Electrical current is passed through this sandwich, changing the orientation of the liquid crystals and changing how they interact with polarized light, depending on the amount of current the crystals receive.
Electrodes provide the current in these traditional LCDs. The Hong Kong researchers scrapped the electrodes, which not only cut the space needed for the apparatus, but also dramatically decreased its need for energy.
Therefore, once an image is drawn on the screen, known as a bi-stable display, the device needs no power to keep it there. And the screen draws power only when the image changes. This makes the device especially suitable for devices that mostly show static images, such as e-book readers.
In the paper on their work published in the Optical Society (OSA) journal Optics Letters, the researchers said actually building a new kind of LCD was not a particularly difficult task.
Or as Abhishek Srivastava, one of the authors of the paper, told OSA’s news department, “Because the proposed LCD does not have any driving electronics, the fabrication is extremely simple. The bi-stable feature provides a low power consumption display that can store an image for several years.”
This simplicity allowed the Hong Kong researchers to take their work a step further by designing a screen that displays 3-D images. These images appear three dimensional because a human’s two eyes are a few inches apart, feeding the brain slightly different images that together express depth.
Old 3-D comic books and even modern 3-D movies manage to emulate perspective by printing two images seen from slightly different angles on a flat surface and provide readers (of comic books) or viewers (of movies) with special spectacles that filter the light so that one eye sees one image and the other sees a different one.
Because that process is tedious, the Hong Kong researchers achieve the 3-D effect by creating a three-way shift in the polarization of the display’s light. One third of the light is shifted 45 degrees to the right, a second third is shifted 45 degrees to the left, and the third is kept at normal polarization. This three-part image is then filtered and viewed, like conventional 3-D images, through special glasses.
Don’t expect to be able to buy such a screen anytime soon, though. Srivastava says he and his fellow researchers are busy figuring out how to speed up its refresh rate and make it show colors.
By Andy Tully of Oilprice.com
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Andy Tully is a veteran news reporter who is now the news editor for Oilprice.com