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Class III laser safety

  1. Oct 23, 2006 #1
    I have a class III laser that I'm doing experiments with. The laser makes a point on a wall. I am starring at this point for extended periods of time. I could potentially star at this point for upwards of 10 minutes at very close range(less than 12 inches). I can't really discern weather or not the point is brighter than an ordinary light bulb or a burning candle. Given the close range and extended period of exposure, is there any danger?

  2. jcsd
  3. Oct 23, 2006 #2
    About 1% of the energy from a lightbulb ends in light. The figure for a laser is much, much higher. A laser doesn't give out light on the area of a sphere either, but a small, fixed point.

    You might want to reconsider.
  4. Oct 23, 2006 #3
    Class IIIb (USA) are potentially dangerous as diffuse reflections (what you see when you point one at a wall). But laser pointers never go above IIIa (<5mw). Anyway, why are you staring at a laser dot in the first place? :confused:
    http://electron9.phys.utk.edu/optics507/Laboratories/Laser%20Safety.htm [Broken]
    http://www.fda.gov/cdrh/radhlth/lpm.html [Broken]

    Google "laser eye protection" or similar - these are cheap color filters for your viewing pleasure.
    Last edited by a moderator: May 2, 2017
  5. Oct 23, 2006 #4
    I'm trying to detect fluctuations in the Earth's magnetic field. The laser reflects off a mirror that is mounted on an ultra sensitive compass like device. The dot is suppose to move whenever the Earth's magnetic field changes.

    The laser is just an ordinary laser pointer, and I'm, in essence, doing little more than prolonged pointing.
    Last edited: Oct 23, 2006
  6. Oct 23, 2006 #5


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    Wouldn't it make sense to have the beam projected onto a sensor array and have data recorded off there (as opposed to spending countless hours staring at a dot on a wall...and then, when you do see it move there's just your word to go by)?
  7. Oct 23, 2006 #6


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    I bought a radial saw which comes with a laser guide. It also came with filter safety glasses, which I use. One should obtain the appropriate eye protection. There should be guidelines for using a class III laser.
  8. Oct 23, 2006 #7


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    You definitely need to use a sensor arrangement. Besides the eye safety issue, your brain will play tricks on you after a while, and the dot will seem to move even though it is not moving. The easiest sensor array to use would be a cheap digital camera with continuous recording capability. Adjust the laser intensity down to reduce blooming and overloading the CCD array.
  9. Oct 23, 2006 #8


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    I think the determining factor here would be what type of surface the wall has. The more reflective it is, the greater the potential for eye damage.

    I'd use as non-reflective target as possible, such as a piece of black felt (or something similar) to focus the laser on.

    Berkeman makes a good point about the mind playing tricks though. :wink:

    moo (moo') adj. Of no practical importance; irrelevant, such as a moo point (i.e. a cow's opinion).
    Last edited: Oct 23, 2006
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