Sports Venue LED Displays Technology Showcase
Jan 5, 2011 12:00 PM, By Bennett Liles
The march of video technology has rarely been as public and spectacular as in the realm of large LED displays for sports venues where digital signage is hyped with live video and game replays. The progression from incandescent light rows for scoreboard numbers to crawling text to HD video on LED boards has seen increasingly capable display elements and vastly more sophisticated control systems. These displays have become the technical and visual centerpiece of their respective venues.
The high-profile events in which they are used and the financial investment required have combined to usher in a new level of reliability and service friendly design with modular construction and rugged wiring connections behind the scenes to ensure maximum performance at game time. Recent years have seen a dramatic rise in screen resolution, widening angles of view, smoother motion, expansion of color palette, and some bombastic examples of sheer size.
On the boards, or the modules of which they are composed, there are either discrete LED lamps in a lamp-based design or a surface-mount device (SMD) style that uses lenses for all the lamps in each pixel and allows a greater angle of view without a color distortion known as shouldering. This is where individual LEDs begin blocking each other and altering the colors as the viewing angle becomes extreme. With SMD displays, the angle can extend up to 160 degrees. SMD boards can also provide a smaller LED pitch with 3mm to 9mm between individual display elements. The smaller the pitch, the shorter the minimum viewing distance—as short as 10ft. from a 3mm board and between 150ft. and 300ft. from a 20mm board. Cutting the pitch in half increases the number of display elements four times for a board of specific size.
LED displays may use either static drive or scan drive. In a static-drive unit, all the LEDs in the display light up simultaneously to show the image. In a scan drive product, the LEDs are illuminated one line at a time within a certain group of lines. A scan drive is similar to the way an image is painted, line by line, onto a CRT screen. Scan drives are used on smaller-pixel-pitch displays to reduce the number of IC drivers used on the display, thereby saving money and space on the PC board. Scan drive requires higher currents and limits the brightness of LED displays. Consequently, it is used only on smaller-pixel-pitch displays, typically indoor types, because of their lower brightness requirements. Exterior models with larger pixel pitch usually require static drive to achieve the brightness levels needed for outdoor viewing.
Advances in design have included a black matte finish and small continuous or segmented louvers over the elements to mitigate the effect of ambient light on display contrast. The size of some of the more recently installed units has required the display company to assume to some degree the roles of architect and construction foreman to meld the aesthetic and structural aspects of the product with those of its new home. The unit's International Protection (IP) rating refers to its ability to seal out dust and other particles (first IP digit 0-6) and water (second IP digit 0-8) and a third digit can indicate impact protection. Among outdoor displays for sports venues, the IP rating, such as IP65, is a significant factor considering the investment and expected lifetime of the products.
Typical of the outdoor LED display modules from Akira Digital Signage is the Neoart LED series including the DL18.75 featuring discrete LEDs in a 1R, 1B, 1G pattern with an 18.75mm pitch and 2844 pixels per square meter. Each unit is 23.6"x11.8" and provides a brightness of 6500 nits (candelas per square meter) and a contrast ratio of 900:1. Units with 7000 and 8000 nits are also available. The display allows a horizontal viewing angle of 140 degrees and a vertical angle of 100 degrees while producing 14-bit color with a color depth of 16,384 steps at a 400Hz refresh rate. Higher refresh rates are available. The modules mount from the front using guide pins for proper alignment and an adjustable T-bar arrangement allows mounting in curved frames. The modules may also be daisy-chained in single file for strip LED displays with each DL18.75 using a maximum 200W. The rear structure has die-cast aluminum cooling fans and is reinforced to prevent bending. The internal fans have an autoprotection sensor, and the unit features autodetection of switch-mode power supply (SMPS) activity and data transmission error.
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