Someone was harassing me for < 10 minutes with an illegally-bright green laser once from an apartment tower. I was busy protecting my eyes, so I didn't dare try to see what unit was doing it. I pointed one of my home security cameras at the tower to ID which unit it was and have evidence. They never did it again though. I was a little disappointed because I was ready to go to war.

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Wistar 11 hours ago | parent [-]

Mirror

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somat 10 hours ago | parent [-]

specifically a corner reflector.

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Wistar 10 hours ago | parent [-]

I went and looked at those on Edmund and, oh boy, they are expensive—at least for the solid prism ones.

https://www.meetoptics.com/mirrors/retroreflectors/corner-cu...

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adastra22 4 hours ago | parent | next [-]

A corner reflector is literally just a couple of mirrors at a right angle.

	▲	omnicognate 3 hours ago \| parent [-]
		It's 3 mirrored surfaces at right angles, yes. However the purpose is to reflect the light back where it came from, and if you want to do that accurately over a significant distance the right angles have to be very precise. Say the laser-toting miscreant is 100m away and you want to direct the beam back onto the hand holding the laser. For that you'll need the right angles to be correct to within around 0.05°. You're not going to do that by gluing mirrors together by hand. (That isn't to say that you couldn't make a useful one by hand, depending what you're trying to achieve. Just illustrating the precision calculation.) The expensive prism reflectors gp linked are even more precise than that. They say 3 arcseconds, which is less than 0.001°. There are corner reflectors placed on the moon for precisely measuring the distance to it. I bet those are really precise ones.

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ludicrousdispla 5 hours ago | parent | prev [-]

yeah, you could build one with mirrors though

https://en.wikipedia.org/wiki/Corner_reflector

	▲	smj-edison 3 hours ago \| parent [-]
		Which if you do build your own, I highly suggest working with acrylic mirrors. Very easy to cut, and you don't have to worry about glass shards.