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Help designing a fire proof light sponge

VW

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So I'm a big fan of laser light and recently bought my first high power laser (532nm 150mW). While this wasn't my initial idea, I now want to construct some kind of indoor display for the laser. The first main factor of this is to block out light leakage generated by the dot at close distance, to maximise the beam's visibility. This obviously has to be done in some kind of box unit, my first idea was to use mirrors in a perescope style to divert the beam into the box in attempt to hide the glow, but after experimenting with some white foam I noticed it soaked up the light pretty well.

I was only using a small carboard box with the foam inside and it hid the glow pretty well, so the unit doesn't need to be all that big. The main problem now is keeping this thing fire proof! Dark material actually soaks up the dot beautifully, but you can't use dark material on a concentrated point. Will there be much risk of fire with using white foam? If so, over what period of time?

I hope you get some idea of what I'm trying to construct and any input is apreciated. Thanks in advance...
 

Switch

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I thaught of something like this a while back too, but never got around to build it.You definetly need black material to absorb most of the light.The best thing I could come up with is a 1/2 inch thick 6-7 inch long tube made from an opaque material, with something black and matte at the end as a beam stop.A piece of wood coloured black with a permanent marker would work pretty well.Don't worry about it being a fire hazard, 150mW wont set fire too plain wood not even concentrated into a 0.5mm spot.

A more advanced aproach would involve coated , polarized optics so that the beam could go in with minimal reflection but the reflection wouldn't be able to escape.
 

hawks1282

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If you are concerned about a fire hazard, perhaps placing a lens to defocus the beam inside your light absorbing box would remove any fire starting capabilities that remain at that point. Just make sure you don't focus the beam into an even smaller spot by accident. (or get any reflections off the lens back into your viewing area)
 

RA_pierce

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You can get a metal/hard plastic box and put a hole through it. The inside could be painted black if it isn't already, and inside the box you can place a metal reflective sphere/dome in the back of the box (not centered so the reflected beam does not exit the box where it entered). When the beam is reflected off the sphere, it should be diffused enough so that the reflections on the inside of the box can be absorbed by the black on the inside... It's kinda hard to explain...
It's the cheapest and easiest way I can think of as it doesn't use any special optics or anything... I made one and it works pretty well.
 

BlueFusion

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The best way to absorb it and the simplest is to terminate it on a black heatsink down about 5 inches of 3/4 inch black tubing. Bingo no more problems. Just make sure the 'sink doesn't get too hot.
 

Cyparagon

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There is no risk of fire if using white foam as a beam stop at that power level.
 




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