A video display based on light-emitting diodes is known as LED display. The LED panels serve as small displays or can be integrated into a larger display. LED panels find extensive application in the outdoors billboards and store signs. Recently they are also being used on the public transport vehicles as destination signs. Further, as an alternative form of lighting, LED panels serve the purposes of task lighting, general illumination and even stage lighting.
LED display panels are generally classified into two groups: the conventional panels with discrete LEDs and the surface-mounted device panels. The conventional discreet led display, also referred to as the individually mounted LEDs, is mostly used in outdoor screens. Red, blue and green diodes, in cluster are integrated to construct a square shaped full-color pixel. The evenly spaced apart pixels are measured along the center to obtain a complete pixel resolution. A minimum of 2,000 candelas per square meter is required for outdoor usage. Led displays with higher brightness measuring up to 5,000 cd/m² can perform better under direct sunlight.
Most of the indoor screens are built with surface-mounted device Led displays. The technology involves the mounting of the red, green and blue diodes on a chipset and then on a driver PC board. The diodes being smaller than pinheads can be set much more compactly. This trend, gaining popularity now finds extension even into the outdoor markets.
A SMD technology based screen requires at least a brightness of 600 candelas per square meter for indoor use. Although this range suffices the requisites of the corporate and retail applications, higher brightness levels are essential for clear visibility in brightly illuminated ambiances like fashion and automobile shows with powerful stage lightings. Conversely, if a screen is scheduled to appear in a television shot, the brightness levels must be lowered with low color temperatures. J. P. Mitchell's Flat Panel LED Television Display was received with recognition and awards in 1977. Three decades later, since the original designs the actual LED TV emerges with the organic electroluminescent materials. Moving ahead of the monochromatic 1977 model, today's LED television displays employ diodes with high-brightness to create a wide spectrum of colors.
The locations of large Led display panels depend on a various factors like line of sight, vehicular access, cable runs for video, power supply, overhead obstructions etc. The LED display covering the Fremont Street Experience in Las Vegas, Nevada is the largest in the world, with a length of over 450 m. The 49x22 m LED television, Center Hung Video Display, located at Cowboys Stadium, is the largest of its kind.
