What is an edge-lit sign?
The light comes in at the sides, not from behind. LEDs along the edges feed a light guide plate that spreads the glow evenly across the whole face of the sign.
An airfield sign must be readable at night and in poor visibility, and Annex 14 sets the luminance and colour of its face. An edge-lit sign meets that with a different arrangement from older designs: the light sources are not behind the legend but along the sign's edges, and the plate between them does the spreading.
1Light in at the edge
LED strips run along one or more edges of the sign and shine into the side of a clear acrylic light guide plate. Because the light is injected sideways, nothing sits directly behind the legend to show as a bright spot.
2Plate spreads it, face shows it
Inside the plate the light travels by reflection. A pattern of fine marks on the plate lets it escape toward the face, and the pattern is graded so the whole panel glows evenly. A reflector behind the plate returns light that would otherwise be lost, and the translucent face carries the legend and the background colour.
3What it gives the design
Even luminance across the face, and a thin housing, since there is no lamp cavity behind the panel. An edge-lit sign differs from a back-lit sign, whose light sources sit behind the face, and the plate itself is covered in its own entry, the light guide plate.
| Element | Detail |
|---|---|
| Light source | LEDs on the edges of the sign |
| Spreader | Light guide plate, which carries light across the face |
| Rear layer | Reflector, returning light to the front |
| Face | Translucent panel carrying the legend |
| Result | Even luminance and a thin housing |
| Compared with | Back-lit sign, with light sources behind the face |
| Power | From the series circuit through an isolating transformer and an LED driver |
Frequently Asked Questions
Q1What is an edge-lit sign?
An airfield sign whose light sources sit along the edges of a transparent light guide plate. The plate spreads that light across the whole face, so the legend glows evenly.
Q2How does the light reach the middle of the sign?
It enters the plate at the edge and travels inside it by reflection. A pattern of fine marks on the plate lets the light escape toward the face, and a reflector behind sends the rest forward.
Q3Why use an edge-lit design?
The light sources are at the edges, not behind the face, so the sign can be thin, the luminance is even, and there are no hot spots behind the legend.
Q4How is an edge-lit sign different from a back-lit sign?
A back-lit sign has its light sources behind the face, shining straight through. An edge-lit sign puts them at the edges and relies on the light guide plate to spread the light.
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