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Madysepanganahi
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I’ve got a laser that I want to use to measure a straight line (preferably within about a millimeter) over about 2000 ft. My first thought was to focus my laser better and bring up a card until it cut the beam completely, but focusing down to a millimeter point so far away feels pretty unachievable. Instead I put a tiny speck of retroreflective film up at the far end and raised a card through the beam till the shadow of the card stopped the light from hitting the reflector. In a world with ballistic light this would work perfectly, but unfortunately we live in a world with diffraction, so if you set the card partway through the beam and walk to the end to look at it, the “shadow” of the card is super fuzzy and has diffraction fringes around it, decreasing the accuracy of my measurement.
(unless that first order fuzziness is actually linear with distance to the target and I’m not actually losing accuracy at the card? It’s hard to tell)
I’m now imagining using a moderately narrow (1mm) slit instead of an edge and moving it up and down until the reflected light is brightEST, but I feel like there should be a better, more precise way. Does anybody have any thoughts?
Thanks so much!
(unless that first order fuzziness is actually linear with distance to the target and I’m not actually losing accuracy at the card? It’s hard to tell)
I’m now imagining using a moderately narrow (1mm) slit instead of an edge and moving it up and down until the reflected light is brightEST, but I feel like there should be a better, more precise way. Does anybody have any thoughts?
Thanks so much!