Chargers could one day be a thing of the past thanks to the development of an LCD screen that doesn’t need a power source. The ultra-thin LCD display, described in Optics Letters on 22 October, is also capably of displaying three-dimensional images; making it a compact, energy-efficient way to display visual information.
Invented by scientists from the Hong Kong University of Science and Technology, the LCD screen is bi-stable, meaning it only uses power when the image on the screen changes. Therefore, it is well-suited for applications that use a static image for most of the time, such as e-book readers.
Unlike other methods for creating 3D images, to minimise energy consumption, the scientists create the illusion of depth from a single image by altering the polarisation of the light passing through the display.
Liquid crystal displays (LCDs) are used in everything from television screens to digital clock faces. In a traditional LCD, liquid crystal molecules are sandwiched between polarised glass plates. Electrodes pass current through the apparatus, influencing the orientation of the liquid crystals inside and manipulating the way they interact with the polarised light. The light and dark sections of the readout display are controlled by the amount of current flowing into them.
Newer displays do not use the electrodes; therefore making the screen thinner and decreasing its energy requirements. Once an image is uploaded to the screen via a flash of light, no power is required to keep it there. ‘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,’ explained Abhishek Srivastava, one of the authors of the paper.
To add the capability to view 3D images, instead of displaying multiple images on separate panels and carefully aligning them − which wastes both time and energy − the researchers altered the polarisation of the light passing through the display. The image is split into three zones: one in which the light is twisted 45° to the left, another in which it is twisted 45° to the right, and a third in which it is unmodified. When passed through a special filter, the light from the three zones is polarised in different directions. Glasses worn by the viewer then make the image appear three-dimensional by providing a different view to each eye.
The technology isn’t suitable to be used for television screens quite yet: it only displays images in greyscale and can’t refresh them fast enough to show a film. However, Srivastava and his colleagues are in the process of optimising their device for consumer use by adding colour capabilities and improving the refresh rate.