Diffusion pattern for back-lit/edge-lit signage

Hello! Longtime lurker, first time poster. :slightly_smiling_face:

I was taking apart a beer sign that I had, which was edge-lit by LEDs. I found the diffusion pattern inside quite interesting, so I thought I’d share my discovery, in case it helps anyone.

Essentially the whole thing is a plastic sandwich with the following ingredients (front to back):

  • Protective acrylic
  • Printed transparency
  • Dimpled edge-lit acrylic to diffuse light
  • White sheet to reflect light forward
  • Black sheet to prevent light from spilling out the back

Here’s the bottom three layers:

Here it is lit:

…and here’s a closeup:

Most of the awesome edge-lit projects I’ve seen so far have been purely acrylic and not mixed-media (if this counts as that). Hopefully, this helps someone with a project.


That is great! thanks for sharing! Should be really easy to do on the :glowforge: and looks like it will disperse light nicely.
I wonder if you could get some cool effects by changing the density of of the dots???


yes. this is called halftone.

this is for printing, but it’s essentially the same technique one would use on a laser-engraved light.


Yes, that is really cool–would be fun to experiment with the concept.

This is really cool! I can see it being used with different dithering effects to make some pretty complex stuff!

I have so many LED bases stockpiled for the day I get my GF! I’m going to drive everyone crazy with edge lit signs…


This process is used in light guid plates in LCD panels. It performs like a Fiber optic cable, except its flat, with a strip of LEDS (or Cold Cathode Florescent if it’s old school) at the bottom. The guide plate is tapered slightly (Thinner at the top). The top also has more dots per square inch to help it pull more light out of the panel to compensate for the loss of light over distance.

In larger displays the LEDs are arranged along the edge, but most laptops have a single light source.

Thicker LED backlight panels have the LEDS in a grid along the back of the panel. It allows them to use less LEDs, and gives the option to dim different areas of the screen to improve contrast in darker scenes.


cool - thanks for the write up! I bet there are a bunch of us glowfolk who never grew out of our childhood habit of taking stuff apart to see how it works. :nerd_face: nice to have a community which celebrates that spirit.


I’m no mathematician but I’m sure someone here could figure out the ratio and subsequent array of holes needed using the inverse square law for a given/known light source.

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Thanks for posting @cgaeden. I see that you have had the cake all along! I’m intrigued by this. I have so much 1/4" acrylic and could make some nice difusion panels with it, some LEDs and some plywood. Great project inspiration, and I took the liberty of putting it in that category instead of everything else.

Edit: well, reading the second July update, my organizational attempts are for naught. Seems like project inspiration is disappearing soon.

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