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Laser questions

  1. Apr 5, 2008 #1
    Do opaque materials like wood or plastic block the harmful radiation from a laser?
    I understand how laser safety glasses filter out IR radiation. So does a piece of Aluminum or black plastic block it completely?
  2. jcsd
  3. Apr 5, 2008 #2


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    What wavelength is your laser? It depends what they emit and on the internals. For instance, green DPSS lasers emit green AND infra-red (if they are not filtered). Opaque materials will block VISIBLE radiation from lasers and anything else not in their transmission spectra.
  4. Apr 5, 2008 #3
    I have a 20 watt IR laser operating at 1064nm and use it to mark or etch parts.
  5. Apr 5, 2008 #4


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    Wood / metal will certainly block the laser - upto the point that the laser cuts through them!
    With plastic you have to be much more carefull. A lot of black pastics are transparent in the infrared, sometimes this is done deliberately in the design of the dye to reduce the amount of heat they absorb in sunlight. It can be a real pain in optics finding the light leak in a CCD camera due to some black plastic in a connector that is transparent.

    20W is enough that you would only need a leak of >0.1% to be an eye safety issue. You need some professional help to make this installation safe - remember you only get one set of eyes!!!!!

    At the very least I would recommend that you enclose everything in a metal cover - painted so that there are no stray reflections, keep the laser and parts at waist level and wear eye protection.
    A major danger in this sort of system is the laser being reflected up into your face from a screw-head or scratch on the metal. You should also have it in a locked room with some sort of interlock so that the laser turns off if anyone enters.
  6. Apr 6, 2008 #5


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    I'm glad mgb_phys already said it wants, but it bears repeating: if you do use metal, be sure to bear in mind the possibility that the surface may act as a reflector, redirecting the beam in some unforeseen direction. Therefore, if using metal, it would be necessary to completely and close the workspace, or coat the metal in some form of nonreflective paint. Also, in light of his warnings regarding the infrared transparency of some plastics, and the fact that many paints used latex (or some other polymer) as a base, be careful not to select paint that is transparent in the infrared spectrum.
  7. Apr 6, 2008 #6
    thanks for the info.
    So why does metal block infrared light?
  8. Apr 7, 2008 #7
    In laser labs we mainly use opaque plastic glass (CO2 laser 10,6 micron). As i see your laser is CO laser 1 micron, so it also preferably to use plastic opaque glass.

    1. It is opaque, so you can see what is happening in working area.
    2. It absorb laser radiation.
    3. It does not crack as window glass in pieces (plastic is melted), so it is more safety with it.
    4. It smells when burning, so you know by nose that something is wrong.

    But real safety only God can give and thick asbest plate :)))

    Metals plates are not safety becouse of mirror effect.
    Last edited: Apr 7, 2008
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