I'm putting RGB LEDs behind panels. My challenge is to get the red, green, and blue light to diffuse into one color, rather than identifiable component colors that sort of overlap.

For example, if I light the red & the blue, I'd like the panel to glow with a uniform purple.

For counter-example, if you look at this Instructables example, you can see how the light is identifiable by component around the edge.

How can I buy or make panels that diffuse light like this? Will it work, or do I need to do something fundamentally different?

 

Yes you need that type of lampshade or some shaded lampshade (through that you cannot see the bulb).If you search "mood light" on google they all using some sort of lampshades to spread out the light equally & smoothly.

It will display the real colour if the LED is a RGB type single LED.Instead of seperate three LED's.

3W RGB LEDs superb for this.

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A similar question was asked a while ago and my guess at a way to diffuse it was to coat the LEDs with salt. Salt is actually a clear substance but appears white because it reflects and refracts the light internally. The poster tried coating an LED in super glue and then in salt and reported success. I'd try it on a cheap LED first.

Mike.

 

http://videos.howstuffworks.com/labr...work-video.htm

I don't think this will help but interesting on the approach to what your doing.

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I've used hot glue, but you have to keep turning it until the glue cools in a blob. Also uncolored plastic, like from a milk jug works fairly well.

 

The other option is to use the same material that is used in an integrating sphere. Normally I would have just said the name, but I can't remember it right now. It works amazingly well. I use it to take bounce a laser beam around such that it fills the aperture of a ccd camera.

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If you're planning on lighting a panel...I would use epoxy (optical grade clear stuff) to glue the LED's into the panel.

The reason RGB LED's don't 'diffuse' too well is because of the packaging, you want as large a viewing angle as possible, preferably >100 degrees. Using epoxy will effectively bond to the LED lens, no air gap means no focusing, which gives a massive viewing angle. This mixes the colours quite nicely within 5mm of an acrylic panel.

A simpler option would be to use a plastic white 'box' (or like a small shallow tray). Put the LED at the side so it shines into the tray/box, then cover the whole thing with some sort of diffusing film. - drafting paper seems to work quite well. A white surface is a lambertian reflective surface, which means it scatters light in all direction, effectively mixing all wavelengths and scattering them. After bouncing around in a reflective box for a while they'll mix quite nicely.

Blueteeth.

Ps. all the above is what I tried for an LED TFT backlight.

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The name of the material I was thinking of is spectralon

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mmm on the cheap you can make a reasonable diffuser by simply sanding the LED

 

One last thought, I use a garage lightbox for taking pictures of little items. I found that 2-3 sheets of 24lb bright white paper works pretty good.

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I've used this method in the past and it works ok, but the best i've gotten for low power is by using tissue paper folded a couple of times and put over the RGB LED's


On a larger scale, I mounted the LED's facing toward a white painted gutter like skirting and using the reflected light to diffuse and "meld" into one color on the targeted wall/roof. Worked perfectly and was quite the marvel to watch.

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I'm sure you can get diffused RGB LEDs.

Failing that, you could make a clear LED frosted by sanding it with fine sand paper.

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I've sanded clear LEDS before, does wonders. Last time I bought RGB leds I got a diffuse plastic package, even better. Sanding that would help too. A simple tracing paper cap will help further.

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