Light Pipe design guidelines...

Hi All,

Has anyone else here designed a lightpipe? or can give any good tips? Materials, finishes and process’s

I’m having a bit of trouble getting light to be evenly spread across my design.

…a light pipe, edge lighting, is like a lens or prizm…what goes in one end comes out the other…what you likely need to spread the light evenly is a diffuser between the light source and where you want the light to exit… a texture molded on the back side of the panel will help and/or multiple light sources, if possible…also you may need to cover, mask, all surfaces of your pipe except where it goes in and where you want it to come out (black is ok, chrome is better, chrome backed with black is best)…go to a junk yard and look at the instrument panel from a car and you will see all the above techniques…

mmm…nice cromed i’ll give that one a try. I’m asuming that will help with all those internal reflections.

cheers

…the mask (chrome or other) is to contain and redirect any light which might be deflected by the pipe material before it exits where you want it to…the longer the distance from source to exit the more you will benefit from the mask…

You can go to Lumex and check out their stock light pipes. I think there’s a lot that can learned from those:

http://www.lightpipes.net/

Warren

You only need to have the outer-most surface - the one you see - to be diffuse in texture. Rubbing it with a fine-grain wet-sandpaper for example. I think that the angles being correct is quite important as well. If you need to actually bend it, have the first surface (right next to, or on top of the LED) be polished, and like mrd wrote the length makes a difference, but not as much as you think.

Materials should be the clearest stuff you can find, acrylic, polycarbonate.

Good link ‘warrenginn’ I’ll take a look at there samples.

I’ve done a quick diagram of the problem below:

I’ve got a fixed object which is currently causing a shadow on the diffuser and I need there to be even illumination on the top of the diffuser from the two illumination sources. There is also a hot spot directly above the lights which is not desirable.

I can’t move the fixed object or the illumination sources but I can change the form/finish/material of the diffuser.

Try using a 3M light diffuser film. Most vinyl/sign shops can get you some. Its all about moving the light around… if you have a hot spot it is most likely because your light source is too close to your surface. If you can’t move it away, try a using a light source that isn’t so bright, or make the interior surface of your box white to reflect some of the light, then you can use the ambient light to illuminate your panel.

This is the same method that most sign shops use to create channel letters with either neon or LED light.

I took apart a few things which had real good even illumination and they had a little peice of film in them…i guess this was the stuff. Look like Avery do some aswell.

I also found out (well a quick google search on light diffuser film) about POC’s DTF® Directional Turning Film (link)

Your problem is not that complicated. Osram has solved by using two layers of diffuser and an edge firing light source.

http://www.osram-os.com/products/lampmoduls/ma_line5.php?lan=eng&id=116

:)ensen.

that uses edge lighting, i can’t move the position of my LED’s which are paralel to the top surface. also my top surface is roughly 20 x 15 x 5mm, so its a bit small. I trying to get hold of the diffuser film i think this will be my best shot for spreading the light around.

The Osram solution is quite elegant. To bad you can’t reconfigure.

As such, the short distances are your enemy here. May I suggest using a number of thin diffuser elements separated by space. You lose a lot of the intensity, but the amount of diffusion will be a lot higher than a single element of the same overall “depth.”

:)ensen.