When an LED video wall is turned on for the first time you don’t want to see seams between the individual LED modules. To get a flawless image without seams, LED modules must be perfectly aligned with each other. Each tiny gap between modules must be equal to every other tiny gap between modules throughout the array. Doing this with a flat video wall is complicated enough. But when you’re building a curved, faceted video wall using flat LED modules, that complexity increases.

Here is an example of a faceted LED panel connection (looking down from the top). The LED modules were aligned too close to one another and when they warmed up, they expanded slightly, resulting in damage to the module (LEDs were broken off).

Aligning the X axis (horizontal) and Y axis (vertical).
The distance from the center of one LED to the center of the next is called pixel pitch (see Coming to Terms with LED Technology”). A properly aligned display maintains an identical distance between all the modules.

Take for example a pixel pitch of 1.2 mm, where each LED is 1 mm square. That means there are 0.2 mm of space between each LED. This .2mm spacing is our reference to align one module to the next during the installation. The .2mm applies to all 4 sides of each module (sides, top, and bottom).

There is no room for error. The tolerance is only about 10% of the pixel pitch. In this example, that would be .12 mm, which is about the thickness of 20 lb. paper. If the spacing is not maintained, dark or bright lines will be seen when viewed from straight onto the display.

Aligning the Z-axis.
In addition to the X and Y axis alignments, the face of each LED must also be perfectly flat across the display. A misaligned Z-axis will result in bright and dark lines being visible in the image when viewed from an angle off center to the display.

The LED module on the right side is about ¼ of a pixel lower than the module on the left side. This amounts to about .25mm out of alignment which is above the .12mm tolerance for this pixel pitch. This will be very visible when the display is in operation.

LED panels have some built-in adjustment to help align the LED modules during installation when installed in a flat configuration. This typically works very well if the mounting structure is precisely fabricated and correctly installed.

With a faceted LED display, those built-in alignment features will not work. They are designed for a flat video wall and not one that has a slight angle between each LED panel. The alignment must be managed by the mounting structure. To find out how Draper goes about designing structures for faceted video walls, see this earlier article on the subject.

If you’d like more information, or to discuss your next LED project, click here to reach out to your Draper Pro AV representative.

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