Question about potting optics

I've got a couple ideas for multi-led lights, and I want them to be very rugged and waterproof. I want to use optics instead of reflectors, partly because of the efficiency, and partly for the finished look.

My question is, will it mess up the refractive properties of the lens if I fill in the open space on the sides with epoxy? Would the type or color of epoxy matter?

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TIR optics rely on the index of refraction of both the optic itself and the medium surrounding the optic. I think typically it is assumed that this medium will be air. Changing the index of refraction of the surrounding medium is going to change the behavior of your optic.

Maybe you could use a small cylinder surrounding each optic and epoxy between cylinders?

That will kill the optics unless they are in holders that you can seal against the epoxy.

Short answer: don't let anything touch the refractive surfaces of any optic.

That's what I had assumed, just wanted to hear from someone else. Thanks for the replies.

I may just have to reinforce the outward facing end.

electromage said:

That's what I had assumed, just wanted to hear from someone else. Thanks for the replies.

I may just have to reinforce the outward facing end.

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Not too fast. It is possible. You need to get some mold release and coat the optics. Then fill up the area with epoxy, let it set, then remove the optics and clean off all the mold release. Pop the optics back in and your done. OK so there is a little more to it than that but thats the basics. You need to make sure the epoxy is blocked off from the LED and inside pocket of the optic. You also need to make sure there is nothing sticking out from the sides of the optic that would mechanically trap the optic into the epoxy. Let me know if you have any other questions.

saabluster said:

Not too fast. It is possible. You need to get some mold release and coat the optics. Then fill up the area with epoxy, let it set, then remove the optics and clean off all the mold release. Pop the optics back in and your done. OK so there is a little more to it than that but thats the basics. You need to make sure the epoxy is blocked off from the LED and inside pocket of the optic. You also need to make sure there is nothing sticking out from the sides of the optic that would mechanically trap the optic into the epoxy. Let me know if you have any other questions.

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That is correct
Make sure you use an epoxy with a high cure to shrink percentage.
That way, when you use your mold release (vasaline works good),
Your optic will have that "Air Gap" that is necessary for
optical refraction. But you could still seal around the very top edge
toward the top of the optic to acheive waterproofness. Mix some
glow powder in there while your at it
Another way to "Fully" pot the optics in epoxy is to use a Silver-Based
solution to coat the outer sides of the optic. That way you can still
have your epoxy completely potted around the optics without optical
distortion. Check with your local mirror and glass companies for some
"Silvering Agent" to do this. I hope that helps!


Robert M.

Thanks to everyone, you've got some good ideas. I hadn't thought of silvering the outside of the optic before potting it, I'll have to see if I can find some of that stuff and test it out.

Thanks saabluster for the PM, I actually thought that I had responded, but I guess it didn't go through.