Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

I How to estimate the power of a laser pointer

  1. Aug 14, 2015 #1
    Not sure if this is the right place, but I'm hoping to ask two questions:
    1. I shine a laser pointer at a mirror at night, and the reflecting beam glaces off of my eye. Obviously it's quite bright, and I want to know if this has caused any serious damage. Of course I shut my eye, but apparently only 5mW is safe for eyes.

    2. Does anyone know how to estimate the power of this pointer?
    All that's said on the laser is that its max power output is less than 1000 milliwatts. That's obvious.
    The model is apparently a "JD-303". I looked that up, and it's a 500mW laser, which doesn't seem right.

    From this video , it seems that 500 mW should be able to burn anything, from my eyeball to my bedsheets- which mine can't do.
    It's quite bright- At night, if I shine it out of my window, it (the whole beam, not the dot) clearly goes for quite a few kilometers. (allowing me to point it into hotel rooms and such.)

    The battery in the laser:
    "BRC 18650 4800mAh
    3.7Volts lithium ion battery"
    Perhaps that helps.

    is it just that my laser has a bad focus/lens, since it's apparently not very powerful?

    Perhaps the battery stats can help explain the power output of this laser. Will I need to see a doc....?


    oh. and I bought this laser off the street....... In China. I honestly don't know if it's a fake, but from what I can tell, so far it is actually quite authentic. I don't think that just because I purchased this off the street that it should be considered fake, although it's a possibility. I'm not sure if street peddlers can really sell fake lasers though.
     
    Last edited: Aug 14, 2015
  2. jcsd
  3. Aug 14, 2015 #2
    You wrote,

    "
    All that's said on the laser is that its max power output is less than 1000 milliwatts. That's obvious.
    The model is apparently a "JD-303". I looked that up, and it's a 500mW laser, which doesn't seem right."

    Why don't you believe that number, I would?

    To estimate power use a volt/amp meter to determine current passing out of the battery and the battery voltage while the laser is working, this will likely require some jury rigging. Current times voltage gives power. Google the efficiency of solid state lasers?

    https://www.google.com/search?sourc...id state lasers&aqs=chrome..69i57j0.11126j0j8

    Notice anything wrong with your vision?

    Be careful with dangerous tools.
     
    Last edited: Aug 14, 2015
  4. Aug 14, 2015 #3
    I don't believe it because it's far from burning matches, or paper.

    I unfortunately don't have the items or ability to measure this sort of stuff.

    I don't think anything is wrong with my vision....... I suppose I wouldn't be asking here if there was something wrong.
     
  5. Aug 14, 2015 #4

    blue_leaf77

    User Avatar
    Science Advisor
    Homework Helper

    To burn things, you need high intensity, not high power. How much Watt higher do you think the lamp in your room has, and you are still alive?
     
  6. Aug 14, 2015 #5
    Ok......
    Well the beam seems pretty darn well like a laser beam.....

    I can't possibly focus it more than it already is. And I feel absolutely no heat even if I stick the laser on my hand. ??
     
    Last edited by a moderator: Aug 14, 2015
  7. Aug 14, 2015 #6

    berkeman

    User Avatar

    Staff: Mentor

    Yes, taking even a low-intensity laser hit in your eye can start to create damage. Please do your best to avoid that. It would be a good idea for you to have an eye exam, and talk to the doctor about laser safety.

    And why are you shining your laser into hotel rooms? That can earn you an assault or battery charge if you are caught...
     
  8. Aug 14, 2015 #7

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    This is impossible to tell based on that description.
    To ruin other's vision? ...

    The power drawn from the batteries is probably a good start - it gives a very hard upper limit on laser power and allows to make a reasonable estimate.
    An even better idea is to not use lasers of unknown power.
     
  9. Aug 14, 2015 #8
    Yep. I'll try to avoid that...... I assure you I didn't stick my eye in front of the laser......

    I assure you, if it was your first time getting a neat laser like that you wouldn't be able to resist doing that.
    But i'm also not in the US, people don't get beat up for small things like this :-]
     
  10. Aug 14, 2015 #9

    berkeman

    User Avatar

    Staff: Mentor

    Thread is done.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: How to estimate the power of a laser pointer
  1. Laser Pointers. (Replies: 16)

  2. Green Laser Pointers (Replies: 1)

  3. Laser pointer life (Replies: 1)

  4. Laser pointer and CD (Replies: 1)

Loading...