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I have a light fixture which is designed as three rows of LED light strips. The problem is that the LEDs appear as brilliant points of light. In the fixture I want to diffuse this light so that it appears pure and continuous. The fixture points downwards and is about 6" wide by 24" long.

I have tried frosted glass, but when the LEDs shine through the frosted glass, the individual points of light can still be clearly seen. The light is not continuous and smooth.

I notice that there are LED bulbs that give off an even light, so obviously they use some method to transmute the LED point sources to a continuous shine from the entire bulb, but I do not know how this is done or whether I can imitate it.

What are my options for diffusing the light from the light strip to make a continuous plane of light?

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    $\begingroup$ I think the frosted glass concept is good, but you may need multiple thin layers or a different material. There are some microscope backlight devices at my lab that have very point-like LED's inside them. I'll try to look at how the diffuser is constructed next time I go in... Increasing the distance between the diffuser surface and the point sources will help also, if that is an option $\endgroup$
    – Pete W
    Commented Apr 6, 2021 at 7:18

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The problem is probably that your frosted surface is too close to the LEDs. It needs to be far enough away, compared to the distance between the LEDs, that a point mid-way between two of them gets almost as much light as a point right in front of one.

I would guess that it will start to look the way you want when the frosting-to-LED distance is about twice the LED-to-LED spacing.

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you can take a piece of sandpaper and rub the top of each diode with it to make it rough. Try this on one diode in the array to see if it is good enough to do the trick before you rub all the diodes.

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  • $\begingroup$ this will probably increase the temperature of the LED as less light will be extracted from the device $\endgroup$
    – adrienlucca.net
    Commented Jun 10, 2021 at 15:19
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Looking at microscope and laboratory optics, I think a ground glass optical diffuser was be used, instead of frosted glass. Typically small size however, and expensive.

I believe the idea is that random reflections happen inside the thickness of the diffuser, not just at the surface.

For overhead lighting, I suspect there are similar things in cheaper materials, clear plastic micro beads evenly distributed in a clear plasic matrix. Something like this ? This link was the result of a very short search, there may be more subtypes of the material so look carefully that you get one with a good chance of working well...

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