Light-emitting Diode (LED) and Liquid-crystal Displays (LCDs)

Light-emitting Diode (LED) and Liquid-crystal Displays (LCDs)

In LED, a matrix of diodes is arranged to form the pixel positions in the display and picture definition is stored in a refresh buffer. Information is read from the refresh buffer and converted to voltage levels that are applied to the diodes to produce the light patterns in the display.

Liquid crystal displays (LCD) are the device that produces a picture by passing polarized light from the surroundings or from an internal light source through a liquid crystal material that transmit the light. Liquid-crystal displays (LCDs) are commonly used in small systems, such ' as calculators and portable, laptop computers.  (LCDs are commonly used in small systems, such as calculators and portable, laptop computers. These non-emissive devices produce a picture by passing polarized light from the surrounding or from an internal light source through a liquid crystal material that can be aligned to either block or transmit the light.) The term liquid crystal refers to the fact that these compounds have a crystalline arrangement of molecules, yet they flow like a liquid. Flat panel displays commonly use liquid crystal compounds that tend to keep the long axes of the rod– shaped molecules aligned. In a flat panel display, two glass plates, each containing a light polarizer at right angles to the other plate, sandwich the liquid crystal material. Rows of horizontal transparent conductors are built into one glass plate and columns of vertical conductors are put into the other plate. The intersection of two conductors defines a pixel position. Polarized light passing through the material is twisted so that it will pass through the opposite polarizer. The light is then reflected back to the viewer. To turn off the pixel, we apply a voltage to two intersecting conductors to align the molecules so that the light is not twisted.