LED Displays 101: The Basics
LED Insider is an article series intended to provide background information and working principles regarding the use of LED displays. Some of the concepts discussed may be foundational background that is applicable to any display type, while other topics will be very specific to contemporary LED display technology and may not transfer directly to other displays or media.
This series can be read through with each section building on the one before, to quickly come up to speed on all aspects of LED displays. If you’re already familiar with many of the concepts, you can skip through it and just use it as a refresher or a reference to fill in any gaps you may have. And of course, feedback is always welcome! If there’s a topic you’d like to see covered, or an area that can be improved on, let me know!
The LED Display
Throughout this series, we’ll be focusing on LED displays, a type of electronic display technology. To start off, we’ll look at how an LED display compares to other display technologies, and understand how and when some of these differences are important when selecting a display for a particular application.
LED displays are considered to be direct view, which is a display type that emits light directly from the viewing surface. Direct view displays are contrasted with indirect view displays, which bounce modulated light off or through a passive surface. Examples of direct view displays are those using CRT, LCD, plasma, OLED, and LED technologies. These displays come in various sizes and have differing performance characteristics, but they all emit light directly from the surface being observed. Projectors are an example of an indirect view display, where the image generating surface such as an imaging chip or film frame is at least one step removed from the viewer.
Both display types have advantages and disadvantages, depending on the context or application. Direct view displays tend to require less controlled lighting in an environment, but are typically limited in physical size based on a fabrication technology. Projection can provide very large shared viewing surfaces, but due to the light required to come from a single* source, tend to be dimmer and require a controlled environment. Projected images can also be cast onto non-planar surfaces such as the side of a building, allowing for complex video
Emissive displays emit light directly from the display surface. What kind of display is projection? Not exactly reflective compared to e-ink or other display types which modulates the light at the display surface, instead of relying on inbound pre-modulated light.
In a display with individually lit pixels, each pixel or sub-pixel is illuminated independently of and other pixels in the display. This can increase contrast as ‘black’ pixels are truly off, instead of a dark shade of grey. The tradeoff can be increased cost due to material science process differences (plasma) or increased high power driver circuitry (LED).
Modular displays are bezel-less, and can be physically combined to compose a contiguous display that is much larger than it is feasible to create in a normal electronics fabrication process. TODO Compare to projection blending, bezeled LCD/OLED tiling.
Parts of a display
- Receiver card
- Hub board
- Processing (sender card)