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Laser safety

  1. Jul 6, 2009 #1

    Pengwuino

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    For a certain sexah project I'm going to do, I have a bunch of lasers that have an intensity of "<5mW". I have 780nm IR lasers and 650nm red lasers. When i made a lazy hookup to a 3V power source, the red laser was briiiiight which leads me to believe I've only ever used <1mW lasers in our labs. What safety procedures do I need to observe, ESPECIALLY with the IR laser since I've never used a laser I can't see :rofl: ?
     
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  3. Jul 6, 2009 #2

    mgb_phys

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    Can you make everything enclosed?
    I would definitely want (and the regs pretty much demand) anything IR>1mw to be enclosed
     
  4. Jul 6, 2009 #3

    Pengwuino

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    No, infact it's going to be used in the open as a pointer. I've been using my cell phone camera to see the IR lights and the laser seems extremely dim compared to what it picks up off say, my remote control or the IR port on my laptop. Maybe IR LED's work off a different wavelength that the camera is more sensitive too?
     
  5. Jul 6, 2009 #4

    negitron

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    See these exposure limits:

    http://www.safety.vanderbilt.edu/pdf/laser_exposure_limits.pdf [Broken]

    Basically, the major concern with the lasers you're using is ocular damage; this can be minimized by using appropriate filter glasses:

    http://www.cascadelaser.com/nearir.html

    These are particularly important for lasers with wavelengths you can't see. I don't believe the IR laser you describe here would be rated higher than Class 3B, so full enclosures aren't necessary, although a key switch and safety interlocks are. Protective eyewear as described in teh previous link is also typically required.
     
    Last edited by a moderator: May 4, 2017
  6. Jul 6, 2009 #5

    mgb_phys

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    The regs are little complicated but you have to worry about -

    Power - basically anything >1mW makes me nervous
    Wavelength - IR means there is no blink reflex, but 780nm is still focussed by your eye
    Range - how far away is the victim
    Motion - if you are waving this around how long will it be pointed in one place
    Optics - how collimated is the beam, will anyone be viewing it through binoculars
     
  7. Jul 6, 2009 #6

    Pengwuino

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    Thank you for those documents! I was wondering under what applications these apply and how far off they are for my needs. The pointer will have 2 lasers, 1 red, 1 IR built into it and i suppose the typical distance that it will be used at will be 10 feet from the target area. It'll all be on momentary switches so no worrys about the lasers being on without being in use (absent any malfunction). It will be pointed towards non-reflecting surfaces and no one would be viewing through any optical equipment like binoculars. The beam divergence is <0.8mrad.
     
  8. Jul 6, 2009 #7

    negitron

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    Well, I'd be remiss if I categorically declared your setup to be safe, but given your evident understanding of the risk factors and the pitfalls involved, I do feel comfortable in stating that simply crossing the street is likely an order of magnitude or two more dangerous.
     
  9. Jul 6, 2009 #8

    mgb_phys

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    Ditto - not an official sign-off but a warning not to look into the beam would be enough for me, especially if there is a visible laser to let the victim know the beam is there
     
  10. Jul 6, 2009 #9

    Pengwuino

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    Yah, i'll get some final words of advice from our optics prof at my department. I know how the words 'safety' and 'laser' shouldn't share the same bed :rofl:. The IR laser is quite a curious bugger though considering it appears so dim through my camera. I'll probably go ask if he has a photometer that can pick up infrared light to see more clearly what I'm dealing with here. lasers make me happy.

    Worst case scenario, i sue cyrus for giving me this idea. Win Win!
     
  11. Jul 6, 2009 #10

    negitron

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    Me too. I have a 16 mW Siemens HeNe laser which makes an awesome cat toy (I keep the beam moving rapidly so if if they do catch a specular reflection, the exposure time is in the microsecond range.) My two furbeasts LOOOOOVE it.

    Oh, and for serious laser science projects, too, of course.
     
  12. Jul 6, 2009 #11

    Pengwuino

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    I bought like 5 laser modules just to play with, I think I'm going to turn my .22 into a sniper's rifle :biggrin:.
     
  13. Jul 6, 2009 #12

    mgb_phys

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    If you are at a uni the laser safety guys should have a power meter.
    The beam looks faint on your camera because the IR is filtered - otherwise everything outoors would be washed out (silicon is fairly sensitive at 780nm)
     
  14. Jul 6, 2009 #13

    Pengwuino

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    The IR Led in my remote control comes out fairly bright though. My IR port on my laptop (which i only found out about by having my camera pointed at it one day for some reason!) shows up brightly too. It's a camera phone from years back that's like 0.3Mpixels, maybe they didnt bother filtering it? I took a quick look at radio shack and hte LED they sold there was in the 940nm range. I'm guessing the remote control uses a similar IR LED... although that seems a bit backwards as to why the remote control woudl be brighter if the CCD is sensitive at 780nm... maybe it's more sensitive at 940nm? I'll look it up!
     
  15. Jul 6, 2009 #14

    mgb_phys

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    Silicon is a lot more sensitive at 780 than 940nm, most remotes are 780 because the detectors are more sensitive. A lot of lasers are 940nm

    Colour cameras might have a separate IR filter but it can also be part of the rgb Bayer mask. The filter might not be as effective at the longer wavelength because the detector is less sensitive.
    I could also be that the laser is focussed on only a few pixels so doesn't appear bright on the display because it saturates those few, the LED might illuminate hundred of pixels so gives a brighter looking blob - either way you don't want to use a webcam as a laser power meter!
     
  16. Jul 7, 2009 #15

    Andy Resnick

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    I realize I'm late to this thread, but...

    The #1 safety hazard with lasers is electrical- there are high voltage components within the laser, and these are the most common cause of injury.

    In terms of optical hazards, the two wavelengths have a dfferent set of safety regulations associated with them, and in addition there are different guidelines for direct viewing and reflected light hazards. Finally, pulsed and CW systems have different safety guidelines.

    Kentek makes a couple of great pamphlets:

    http://www.kenteklaserstore.com/category.aspx?categoryID=181

    The laser classification scheme has recently been changed, but based on what you wrote for the specs, the 650 nm lasers are class 3R (IIIa in the old system), while the 780 nm laser is class 3b (IIIb). Both of these do require safety procedures- Class 3b lasers require eye protection, a manual power interlock, as well as understanding where the laser light is confined (beamline, specular scattering, diffuse scattering) etc. Class 3R systems are unsafe for direct viewing, but diffuse relfections are ok, IIRC.

    Turning a rifle scope into a spotter with these lasers is not a good idea unless you know what you are doing- the 780nm backreflections off the glass can damage your retina. The 650 nm will likely trigger your aversion response, so that's less of a concern.
     
  17. Jul 7, 2009 #16

    mgb_phys

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    Our laser safety office said the only laser injury they had ever known was somebody who had been hit by the forklift unloading the truck the laser came in.
     
  18. Jul 7, 2009 #17

    negitron

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    Not for the ones the OP is dealing with--those are evidently diode lasers--actually, modules, complete with driving circuitry and collimating optics. In any case, most commercially-made laser systems have the high-voltage supply well insulated; cwertainly this is the case with smaller units typically available to hobbyists and such. The power supply for mine is entirely potted and fitted with Alden connectors to keep curious fingers from harm. Unless you chew through the cable, it's a practical impossibility to shock yourself with it.

    In any event, I dispute your claim that electrical injuries are most common with respect to lasers in general and request you provide suitable documentation.
     
  19. Jul 7, 2009 #18

    Pengwuino

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    I have a quick follow up question since apparently I know jack about electronics. I am going to need these 2 lasers running off the same power source but one runs from 3-6V while the other runs 3V and I'm thinking I'll use a 6V supply since the 3-6V IR laser seems dim at 3V. What can I do to remedy this? I'm surprised how little I know with simple electronics!

    And just to throw in some specifics, the solution needs to be small. Heck the lasers themselves are like an inch long and a cm in diameter :P
     
  20. Jul 7, 2009 #19

    negitron

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    Run the one directly off your 6V supply and feed the other one through a 3V regulator like a BA03T. Small package size and no external pass transistor required if the load current is less than 1 A.
     
  21. Jul 7, 2009 #20

    Pengwuino

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    Man, what I don't know about simple electronics could fill a book. Actually it probably has, many many books! So just pass it through a regulator? I thought I could just use a resistor or something. I'm making a pointer so I want something pen sized and I simply am going to have probably a stack of 4 button cell batteries 1.5V each (although I bought a 3V lithium battery but it seems kinda weak!).

    The battery I have, it seems to have a .15A output but the laser has an operating current of <50mA. Does this mean that if i directly connect the laser to the battery, that the current reduces to 50mA or that 100mA is still flowing to the other end of the battery? God these are embarassing questions from someone with a BS in physics...
     
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