Working with Lasers: Safety Procedures & Intensity

[Pengwuino]

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 ?

 

[mgb_phys]

Can you make everything enclosed?
I would definitely want (and the regs pretty much demand) anything IR>1mw to be enclosed

 

[Pengwuino]

Can you make everything enclosed?
I would definitely want (and the regs pretty much demand) anything IR>1mw to be enclosed

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?

 

[negitron]

See these exposure limits:

http://www.safety.vanderbilt.edu/pdf/laser_exposure_limits.pdf

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.

 

[mgb_phys]

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

 

[Pengwuino]

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.

 

[negitron]

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.

 

[mgb_phys]

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

 

[Pengwuino]

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 . 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!

 

[negitron]

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.

 

[Pengwuino]

I bought like 5 laser modules just to play with, I think I'm going to turn my .22 into a sniper's rifle .

 

[mgb_phys]

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)

 

[Pengwuino]

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)

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!

 

[mgb_phys]

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!

 

[Andy Resnick]

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 ?

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.

 

[mgb_phys]

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.

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.

 

[negitron]

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.

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.

 

[Pengwuino]

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

 

[negitron]

Run the one directly off your 6V supply and feed the other one through a 3V regulator like a http://parts.digikey.com/1/parts/612612-ic-regulator-3v-1a-to220fp-ba03t.html. Small package size and no external pass transistor required if the load current is less than 1 A.

 

[Pengwuino]

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...

 

[negitron]

A resistor could work, by acting as one half of a voltage divider (with the laser acting as the other), but this is horribly inefficient since any power not consumed by the laser will be dissipated through the resistor as waste heat, and inefficiency is not a good thing for battery operation.

As for your battery, it will supply whatever current the device under power draws at the supplied voltage, up to its maximum capacity. If the device draws 50 mA in operation, then that's all that will flow through the battery. This is true whether the battery can source .15 A or 1500 A.

 

[Pengwuino]

Ok, so how big of a resistor would I need to split the voltage in half? How would I go about figuring that out? I bought a bunch of resistor ranging from 2.2ohm all the way to 2Mohm and they're 1/4W rated.

 

[mgb_phys]

The resistor depends on the resistance of the laser, the trouble is that this could vary as the electronics inside the laser turn on.
A simple regulator will give you 3v or you could just use batteries, it should be easy to get 2 sets of 2 AA batteries, wired so you take 3V from 2 of them and 6v from 4

 

[Pengwuino]

Could I just slip in a terminal between 2 stacks of hte 2 batteries? Although this might be a problem since both lasers need to be controlled by 1 switch.

Sounds like a regulator will be the best bet. Man I wish i had some little software to design the circuit to see what I'm working with... Will the regulator be more efficient then a resistor?

 

[negitron]

Download the freeware version of http://www.cadsoftusa.com/ or try the GNU open source http://www.lis.inpg.fr/realise_au_lis/kicad/ .

And yes, the regulator will be more efficient, though still not as efficient as a DC-DC converter. Those tend to be bulkier, however.

 

[negitron]

Could I just slip in a terminal between 2 stacks of hte 2 batteries? Although this might be a problem since both lasers need to be controlled by 1 switch.circuit to see what I'm working with... Will the regulator be more efficient then a resistor?

Oh, and yes, this will work--just put the switch on the negative lead.

 

[Redbelly98]

A resistor could work, by acting as one half of a voltage divider (with the laser acting as the other), but this is horribly inefficient since any power not consumed by the laser will be dissipated through the resistor as waste heat, and inefficiency is not a good thing for battery operation.

Isn't the same true of a regulator, assuming we are talking about the linear type?

I do agree the regulator is a better choice than a resistor, though taking the 3V from half of the battery stack is more efficient and simpler as well.

Oh, and yes, this will work--just put the switch on the negative lead.

That was my first thought too. Alternatively, a double-pole switch could be used on the positive leads.

 

[Andy Resnick]

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.

http://www.industrial-lasers.com/articles/article_display.html?id=330521
http://www.laserfx.com/BasicSafety/BasicSafety3.html
http://www.geocities.com/muldoon432/Non-Beam_Laser_Hazards.htm
http://www.uwm.edu/Dept/EHSRM/LAB/LaserSafety.html
http://jrm.phys.ksu.edu/Policy/esh.html
http://www.stanford.edu/dept/EHS/prod/researchlab/radlaser/laser/program/nonbeam_hazards.html

 

[mgb_phys]

If the laser is only pulling 50mA then an AA will run it for about 80hours!

Black wire from the negative terminal of the first pair of batteries to a switch, then from other side of the switch two wires in parallel to the negative terminals of each laser.
Then a red wire from the positive terminal of the 3v laser to the positive terminal of the first battery pair and a red wire from the the positive terminal of the 6v laser to the positive terminal of the 2nd battery pair. Now just a wire from the positive terminal of the first battery pair to the negative terminal of the second pair.
You can either use two separate 2battery holders or make a connection to the mid-point of a 4battery holder.


(Sorry don't have a way of drawing on this machine)

 

[Lambduh]

This webpage has plenty of information on laser diodes.
http://www.repairfaq.org/sam/laserdps.htm

There is even an entire list of schematics for diode drivers if you want to build one of your own.
http://www.repairfaq.org/sam/laserdps.htm#dpscld

 

[Redbelly98]

This webpage has plenty of information on laser diodes.
http://www.repairfaq.org/sam/laserdps.htm

Yup, Sam is a good source for info.

There is even an entire list of schematics for diode drivers if you want to build one of your own.
http://www.repairfaq.org/sam/laserdps.htm#dpscld

It seems the OP's laser modules already include a driver circuit. He just has to supply them with 3V or 6V or whatever.

 

[rob in rowlet]

Hey guys, i don't know much about lasers but i bought a laser pen overseas and my buddy told me it was too strong and could burn things. The sticker says class III, 100mW wavelength 650. Should I be concerned?

 

[mgb_phys]

The sticker says class III, 100mW wavelength 650. Should I be concerned?

Class IIIb
Lasers in this class may cause damage if the beam enters the eye directly. This generally applies to lasers powered from 5–500 mW. Lasers in this category can cause permanent eye damage with exposures of 1/100th of a second or less depending on the strength of the laser. A diffuse reflection is generally not hazardous but specular reflections can be just as dangerous as direct exposures. Protective eyewear is recommended when direct beam viewing of Class IIIb lasers may occur. Lasers at the high power end of this class may also present a fire hazard and can lightly burn skin.

So yes - be concerned

 

[Redbelly98]

Welcome to Physics Forums.

Yes, you should be very careful!

Legally, you can only buy 5 mW max in the U.S.

To burn things you'd probably need a lens to focus the beam to a smaller area, but yes it should be possible.