An LED ticker and video display are different and have different purposes. Our objective is to understand the differences between the two types , see how LED digital display technology works and examine the viewing parameters that need to be considered.
An LED ticker display is basically a messaging medium utilizing LED technology as the core digital display device. A ticker typically shows a line of text, numbers, or graphics scrolling past the viewer. The rate of movement of the images is variable but must be at a rate that is comfortably read by the viewer. The display can go straight, wrap it around corners, run it up a wall vertically, combine vertical with horizontal, curve it, daisy chain them together, etc. You can make it unique to your space and application.
Video (think of television or film) is a series of still images that, when viewed in order at a certain speed or frame rate, gives the appearance of full motion. The human visual system can process 10 to 12 images per second and perceive them individually, while higher rates are perceived as motion. Frame rate is the speed at which those images are shown, usually expressed as “frames per second,” or FPS. Each image represents a frame, so if a video is captured and played back at 30 fps, that means each second of video shows 30 distinct still images. The speed at which they’re shown tricks your brain into perceiving smooth motion.
With a video display, resolution is very important to ensure a clear picture to replicate what the human eye sees in nature. Increased resolution i.e. 4K and frame rates above 30 FPS approaches what the human eye can see. For video the most common display technology today is LCD but there is also OLED and for projection DLP and LCoS. In the last few years we are also seeing fine pitch direct view LED in that are appropriate for viewing video.
Since LED is the predominate display technology for large outdoor displays, ticker displays and the new indoor fine pitch LED displays, it behooves us to understand what the underlying technology is all about.
All of the digital display technologies in use today incorporate discrete (individual) pixels. Pixels are short for picture elements, and act as “points of light” to form the images we see. For a video display the pixels form each frame and for tickers they form the letters or graphics in an image. They are the smallest elements of the electronics display system that can be individually controlled and turned on or off. For monochromatic displays the pixels may be of one color (i.e. a red LED ticker). For full color displays there are red, green, and blue pixels which combine to make the full color images we see (i.e. a full motion video display or a full color ticker)
In the simplest terms, a light-emitting diode (LED) is a semiconductor device that emits light when an electric current is passed through it. Light is produced when the particles that carry the current (known as electrons and holes) combine together within the semiconductor material. Since light is generated within the solid semiconductor material, LEDs are described as solid-state devices.
Until the mid-90s LEDs had a limited range of colors, and in particular commercial blue and white LEDs did not exist. The development of LEDs based on the gallium nitride (GaN) material system completed the palette of colors and opened up many new applications for full color LED applications. Today a Rise Ticker provides 256 different levels or shades and by varying the shade of the light, you can create the 16.7 million different colors.
For an LED display the discrete pixels (individual LEDs) are mounted/installed on a circuit board. For indoor applications surface mount (SMD) manufacturing is most common mounting method. LEDs are mounted to the surface of the circuit board with each containing red, green and blue die. Surface Mount LED light disperses evenly across both horizontal and vertical angles, providing wider viewing angles. This makes them an ideal choice for indoor applications.
The circuit boards filled with LEDs are typically placed in a module. LED modules are made up multiple pixels that form the seamless building blocks that are stacked end to end to create the desired size of a video display or as shown below, the length of ticker.
Now we turn our attention to resolution. Keep in mind that high resolution is important in a video display to convey all the content, but it is not as important with a LED ticker. For ticker displays resolution refers to the number of pixels contained in the physical area of a ticker. With a ticker you are primarily looking at images such as stock prices or sports scores that are in numbers and you only need limited resolution to create a digit. At a close distance the numbers may be a little pixelated, but it is readable. The greater the number of pixels per square foot, the more detailed graphics or logos. Ticker resolution is determined by 2 factors the pixel pitch and the height of the display.
Pixel pitch describes the density of the pixels (LED clusters) on an LED display and correlates with resolution. The pixel pitch is the distance in millimeters from the center of a pixel to the center of the adjacent pixel. Since pixel pitch indicates the amount of space between two pixels, a smaller pixel pitch means there is less empty space between pixels. Higher pixel density equates to higher screen resolution. The higher the pixel density, the higher the price.
Pixel pitch is important because it influences the optimal viewing distance for your display. While higher pixel density delivers improved visual quality, it is not the ideal option for every situation. Additional pixel density is intended for a closer viewing distance. At a greater viewing distance such as a ticker, higher pixel density loses its visual advantages and simply increases the cost of the display.
One way to calculate pixel pitch relates to the distance the viewer is from the display. One rule of thumb is called the 10x Rule. This simply states that the pixel pitch x 10 = approximate viewing distance in feet. Another method is to calculate the characters size at a given viewing distance. A large character will have a longer viewing distance while a small character will have a shorter viewing distance. For ticker displays we use 50 feet of viewing distance for every one inch of character height as general guidance.
LED display technology has many benefits. First of all, the displays are seamless. LEDs provide bright high-quality images by enhancing the contrast and enriching the range of colors. They are low maintenance and have a long lifespan resulting in low total cost of ownership in comparison to other display technologies. LEDs are also environment-friendly and easy to use. Perhaps the biggest benefit of all is that they get noticed. Isn’t that the point?
this article contributed by Alan Brawn