Friday, March 17, 2017

Throwing Light #2 - Channel Size & Angled Reflector

Learned a lot about the basics of throwing and controlling light from NeoPixels in Part-1 of this series. But I wasn't getting the amount of light I wanted, probably because I was using a 3v board instead of a 5v - the LEDs are simply not as bright as I'm used to.

I decided to see if bigger "channels" would allow more light to be output, and whether adding a 45 degree "reflector" over the NeoPixels would help project more light.

The answer to both questions is YES: larger light channels do help, and an angled reflector helps (especially when silvered). And painting the channel with silver paint makes a huge differences at both sizes.

The design of the medallion remains essentially the same except for the increased depth of the channels.

Do Bigger Channels Make Brighter Light Rays

Yes, more light escapes from bigger channels. But to make a noticeable difference, I had to make the much larger. So much larger that it makes the pendant slightly bulky, almost 8mm total thickness. And, it is so large I could now put a strip of NeoPixels "on edge" and project the light directly down the channel instead of bouncing it 90 degrees.

To test, I printed the thinnest pendant I could, with the channel's top only about 1mm above the face of the LED. Then I printed another one with roof about 4mm above the NeoPixel. You can see the results below.

With the raw black PLA the difference is noticeable, but not extreme (blue light). The difference is much more pronounced when the interior of the channels is painted with silver paint (shown in red at bottom of page)

A comparison of the amount of light coming out of a 1x4mm channel (top) and a larger 4x4mm channel (bottom). Notice that there is a distinct difference in the amount of light emitted from the two channels. This is the raw black PLA print. Even more light is emitted when the interior of the channel is painted with reflective paint.

Do Angled Reflector Surfaces Really Work
Yes, especially if the reflector-panel is painted with silver paint. The raw black PLA does reflect some additional light from the angled surface (blue image). But if the angled surface is painted silver, then the effect is much more pronounced. Unfortunately, the silver also scatters the light in all direction, making the "ray" shape less pronounced.

I wonder if only painting the angled surface, but not the rest of the channel would be "the best of both worlds" - bouncing more light, but scattering it less. Or maybe a tiny mosaic mirror would be ideal for reflecting and directing light. But as noted, at this thickness, the NeoPixels could be mounted vertically, negating the need for any reflector altogether.

An angled surface (shown at right above) was added to one half of the medallion. I wanted to see if the angled surface would reflect more light from the LEDs (shown as the red boxes).

Even the raw black PLA shoes a small increase in the amount of light when using an angled surface.

When the interior surfaces of the channels are painted silver, the
amount of light reflected off the angled surfaces increases dramatically.

Next test is probably going to be masks and gobos.