20100813

Simple light-diffusing plastic with materials available at the local drugstore

I have been experimenting with lazy ways of making the hallucination goggles. At the moment, its fairly easy to mass produce electronics, so thats not an issue. The main annoyance is building suitable goggles themselves. The only requirement is that enough diffusing media needs to be placed between the eye and the LED in order to create a uniform stimulation of the entire visual field. Today I experimented with pouring various mixtures available at your local KMart into cheap swimming goggles, also from the local KMart.

The overall idea is to get some clear liquid plastic that can be poured into the goggles, and to get some sort of powdered or granular substance that can be mixed with the liquid to make it diffuse light. Technically, any clear granular substance would work since you only need to create a heterogeneous index of refraction in order to scatter light. I tried both PLA ground in a coffe grinder and table salt. For liquids, I tried silicone and clear 5 minute epoxy (5 minutes is quite necessary if you want to be able to get a smooth finish. Anything else cured before I could pour it. Make sure your epoxy mix is clear, not yellow. ) You don't need much of whatever you're adding to the liquid to make it diffusive. I would say no more than 25% of the total volume. I used about a teaspoon for one pair of goggles.

Silicone mixed with PLA that had been powdered in a coffee grinder did not work. The silicone was much to viscous to pour or mold properly, and the PLA flakes were too large and hard to mix.

Epoxy mixed with table salt seems promising. The table salt doesn't seem to effect the curing of the epoxy.


Initial tests are totally awesome suggest that the epoxy+table salt solution works extremely well, and is much faster and more sturdy than the ping-pong ball construction method. If you find that the slight yellowing skews the white balance, the software in the original goggles post should contain some variables for adjusting the white point. Adjust the location of the LEDs so that the perceived light inside the goggles is as uniform as possible, which may appear off-center on the outside of the goggles.


As an added bonus, these goggles are still totally waterproof. Hello do-it-yourself submerged neutral bouyancy sensory deprivation chamber. If I had to do this again, I would pour less epoxy, presently these goggles collide with my eyelashes. Not to mention the fact that epoxy cant stick to flexible surfaces like the seal on the goggles, so if you pour it up there its just going to flake off and make the whole job look messy.

The exterior could be more stylish though. Perhaps there is some way to put the LEDs inside the goggles, or to make some nicely fitted PCBs.

You might want to rinse the goggles in water after the epoxy sets. This will dissolve the few grains of salt that managed to be exposed on the surface.


9 comments:

  1. Very elegant!

    Having the whole googles blink is important, aesthetically, which means no PCBs on the eyes. Mounting the LEDs inside would be elegant, but presents problems with space and positioning. Any way to get another layer of epoxy on the outside that doesn't look tacky?

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  2. At the moment my best guess is drill out a hole in the goggles, insert LED, then pour epoxy. The epoxy should fill in and make the whole thing water-proof again. Might need to think about how the holes are drilled to prevent epoxy from oozing out. Maybe just open up holes for a small wire or connector.

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  3. I'd throw a piece of tape on the outside of the lens, which should hold the epoxy while it cures. How thick is the epoxy layer relative to the LED? Would the thinner section over the LED diffuse the light sufficiently.

    Theoretically, if all googles are alike, you can standardize the positioning of the LEDs.

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  4. I can't imagine how that piece of tape is going to give you a clean finish. I think drilling out a hole on the side of the goggles, and then making some sort of single, solid cable the diameter of that hole, will work well.

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  5. Alternatively I'm sure theres something more uniform than tape that could be used to cover the exterior. Also, some sort of laser-cut diffusive plexiglass + PCB might be tolerable. For purposes of personal hallucinations, theres nothing wrong with exposed LEDs on the outside, but I understand these need style to be taken to raves.

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  6. and by that I mean... I'm sure there is some way of layering on epoxy that doesn't require tape. Maybe some sort of standardize ring or something. this would, however, make the goggles considerably more bulky.

    I'd say 8mm of material is sufficient for diffuing the light for purposes of hallucination, and considerable less (4mm?) for the exterior display. If the LEDs aren't too off center, insufficient diffusion just makes them look like luminous pupils anyway, which is generally acceptable.

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  7. Anonymous26.3.11

    How about painting the lenses w/ a thin layer of white paint... then you could glue a half ping pong ball to the outside and bounce the light off the ball back onto the lens.

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  8. Anonymous26.3.11

    Or maybe even sand/sand-blast to make the lenses translucent ? Good ideas -- post a link if you find something good.

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  9. Anonymous27.3.11

    i tried frosting spray w/ a half ping pong ball glued to the outside.. w/ the LED inside the ball, pointing away from the eye. it works great.

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