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Need ideas on how to repair Sega hologram parabolic mirror
RandyT:
--- Quote from: J-Rod on December 20, 2005, 03:09:08 pm ---
--- Quote ---Also, transmissive optics are very different from reflective ones. You can get away with murder on the transmissive ones, but not reflective or "imaging" optics.
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Yes, I must have glossed over that. I guess what I am not understanding is why the relfective properties aren't repaired by a gloss finish compound, that fills the scratches and fixes divergence. I mean you are the expert on optics apparently, Randy so I'll yield if you can help me understand why it is that filling a void with a transparent compound wouldn't help it reflect better.
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The answer is simple. I'm assuming you have seen a typical "funhouse" mirror. These are usually made out of polished metal, but could be made out of plastic and coated just as well.
In any case. imagine a funhouse mirror and the distorted effects it creates This is accomplished by bending the mirror in one direction or another to achieve the distortion required. If that mirror had its mirror coating stripped away, you could see perfectly through it (not counting refraction) with virtually none of the distortion seen in the reflected image.
Now consider a spherical (or parabolic) surface that has been meticulously calculated to collect light from an object a certan distance (and angle) from the mirror and then to bring the light generated by that object to focus at a very specific point in space. Any deviation in angle/curvature is going to move portions of that light disproportionately to the rest of the image, creating severe distortion. If the deviation is enough (and it doesn't take much) the reflected light will be somehwere else in space entirely and appear as a void, or a very out of focus blob in the image.
This doesn't even take into account whether or not one can polish the plastic to a point approaching the reflectivity of the original.
As for why not? I guess that's a personal choice TravistyOJ is going to have to make for himself. But if he has limited funds for purchasing experimental materials for futile "fix attempts" or values his time in the slightest, I was just trying to save him some heartache.
RandyT
TravistyOJ:
Yeah, I will try to make the current one i have as best as possible while still looking for a replacement. The only really way I know to improve it without possibly making it worse is to tape it up as close as possible, and apply some novus. From what I've gathered, any solvents, glues, etc will probably make it worse. Please PM if anyone comes across one of these or even a destroyed holo-cabinet with one in it.
vader:
I wasn't grasping what RandyT was saying before, I thought like anyone else that just a high polish woud do it, but the funhouse theory explains it pretty well
Tim
J-Rod:
I understand the funhouse effect. From my experience, when plastic breaks, it's usually not a totally clean fault. So you can put the pieces back together and they almost lock, something like a jigsaw. If that's the case, then the geometry should be almost identical. He could test by putting them back together with the tape like he wanted, and testing it out. If the image coalesces into the right spot, then it has a chance. I am bothered by the smallish triangle piece he says broke off though, instead of just one break there's several. His main hope is to look for a replacement in a busted machine, would be much cheaper than trying to have one made. Sucks in any case, good luck with your endeavor. -JC
Stingray:
--- Quote from: Avery on December 20, 2005, 05:28:07 pm ---For gluing the pieces together, what about one of those liquid solvent based glues used for models.
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I don't know what kind of plastic this is made of, but I use those types of solvent 'glues' pretty often. The two main brands that I use are Tenax & Plastruct. Both work great on styrene (which is what most scale model kits are made of) but won't touch acrylic, which seems to be what most here are assuming this dish is made of.
-S