Friday, December 23, 2011

Simple optics: I'm still doing it wrong

I did some approximate calculations and picked the really nice (expensive) laser lenses I needed.

I drilled out some plates to mount them on since they were both super fucking small. A little super glue and they were on there perfectly without messing up the light-transmitting surfaces or even having to touch them with human hands.

Then I disassembled the laser gun and used little stand up clamps to hold them in approximately the right places.

And it totally didn't work. The light was more or less collimated but it was so out of focus it just kind of spread out on it's own. It is clearly not going to work this way. But I didn't know for a while why it wasn't working.

I noticed that the website I bought lenses from also sold duplets (just two lenses affixed to each other). I also noticed that these duplets, which I'd gotten one of in the scope and one in the original projector, seem to work far better than any other lens I have. But when I look at diagrams of how they bend the light it doesn't seem to be any different than any other lens.

So I did some root investigation. I bought some simple 5mW lasers and shined them through the duplets.

It seems like the real strength of the duplets to me is actually their tolerance for poor placement. When you shine a light through them at not quite 90 degrees and centered the lens on the far side just corrects the odd angles the lens on the near side made.

In the case of the laser, it came through clear even when I was off by a bit. Using a single lens or a lens duplet I placed myself it would always be skewed out of focus because my placement wasn't just-fucking-right.

By contrast the manufactured duplet always focused the laser on the other size like one would expect even when I did it at a bad angle or offset from center.

At least that's my theory. So I did some more approximations and bought a duplet that I think will be better for this than the ones I have.

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