Class 4 Laser Safety

[steveclv]

It also depends upon the duration - a Class 4 direct hit on the eye can blind in 1/100th of a second. A diffuse 50mW beam might take 2 minutes before damage occurs and then it might be temporary.

The only "safe" exposure to laser light is 1mW - that's one Joule per second - a Joule is a measurement of energy and that's how much your eye can absorb without damage. Anything greater than that causes progressively greater damage as the retina, iris or cornea starts to heat up.

Is the laser that you are using owned by the university or is it privately owned?

http://www.utexas.edu/safety/ehs/lasers/Laser Safety Handbook-tnt.pdf

This is the Laser Safety Handbook for the University of Texas. Print it and hand it to all concerned.

 

[Forestman]

Does turning down the power to about 50 mW turn the Class 4 into a Class 3?

 

[steveclv]

No, it's still a Class 4 - you could say it was operating under Class 3 limits but it is still a Class 4.

 

[Forestman]

No, it's still a Class 4 - you could say it was operating under Class 3 limits but it is still a Class 4.

While operating under Class 3 limits is it safe to assume that it's not going to be full power to cause potential diffused reflection danger?

Sorry if I seem trivial. I just want to be safe. My teammates claimed it was safe.

 

[steveclv]

The issue is that it is a Class 4 laser and is capable of operating as a Class 4. So even if you operate it as a Class 3, how do you know that someone hasn't fiddled with it and switched it back to Class 4 power?

Even a Class 3 can cause sight damage from a reflection - for example off of a piece of jewelry or a silver watch strap etc. It just takes a little longer. I have to assume that everyone in the room has safety goggles? And remember that safety goggle protect you from indirect light and will not save you if you suffer a direct hit.

When a laser is being handled by just you then you can feel safe as you are in control. If it's being operated by a team of colleagues who have already demonstrated their lack of understanding and respect of a Class 4 laser then I for one would be getting out of there pronto. It's a tragic accident waiting to happen.

 

[InfinitusEquitas]

Class four starts at 500mW...

499mW is still way more than enough to do damage from a direct hit, or specular reflection.

Damage from diffuse reflection depends on the material, and to a lesser degree exposure time. (Generally people don't force themselves to stare at things that make their eyes uncomfortable.)

No offense, but your teammates need to read up on laser safety and stay the hell away from lasers until they do. This should not be a question to ask on a hobby forum, when it deals with a university setting.

 

[Benm]

Impossible to answer that question. It would depend on the material the the laser beam is terminating on.

Personally I haven't been able to get either of my LPM's to register a diffuse reflection off of common household stuff that's matte from further than a few inches with a ~1.5W laser. (Obviously not a very scientific test.)

As long as the sensor area of your LPM is comparable to the pupil aperture, this is a perfectly sound method, provided your lpm can read power levels below 5 mW reliably.

When considering purely diffuse reflections the amount of power/mm2 decreases with the distance from the spot squared, and even at a foot away it would take tremendous power (>>10 watts) to create a diffuse reflection that would exposre your eye to over 5 mW.

The practical implication would really be that if the material you shine the laser onto is something like white paper, it would catch fire at a much lower power level than that required for a diffuse reflection to be dangerous viewed from a foot away.

 

[Forestman]

As long as the sensor area of your LPM is comparable to the pupil aperture, this is a perfectly sound method, provided your lpm can read power levels below 5 mW reliably.

When considering purely diffuse reflections the amount of power/mm2 decreases with the distance from the spot squared, and even at a foot away it would take tremendous power (>>10 watts) to create a diffuse reflection that would exposre your eye to over 5 mW.

The practical implication would really be that if the material you shine the laser onto is something like white paper, it would catch fire at a much lower power level than that required for a diffuse reflection to be dangerous viewed from a foot away.

The material was reflective tape. This tape to be exact; 2 in. x 36 in. Reflective Tape-PN03440 at The Home Depot

 

[Seoul_lasers]

Hey guys,

I am fairly new to lasers and am still learning about how to be safe with them.

At my college I am working with a team on a project where we are using a Class 4 laser.

My teammates think that the reflection from a Class 4 is not dangerous, however I disagree from what I have read and feel very uncomfortable with their actions.

Today, they were testing the laser and there were a few moments where I saw the reflected beam for nothing more than a second or two. This in and of itself raises concern.

How do I know if there is any damage to my eye from the reflected beam?

I'm not sure if it was a matte surface or a reflective surface. I didn't stare at it to find out.

Any help and insight is greatly appreciated. I care about my eyes and I don't want dummies at school ruining them.

Thanks again

I have to call BS on this story! What college allows use of a class IV laser without a laser safety officer? These are extremely hazardous devices capable of causing serious damage to skin and eyes... not to mention if they are +1W output, a serious fire hazard.
A college allowing use without a safety officer is asking for a wild lawsuit on their hands.
Sounds like the poster is trolling!

 

[steveclv]

That's why I asked if it was a university laser or privately owned. I suspect there are a lot of Class 4 lasers in universities that are privately owned and that's a scary thought given the nature of a lot of college students pranks. Yep, I watched Road Trip too

I also suspect that a troll might be at work here but nonetheless, it's worth erring on the side of caution.

 

[InfinitusEquitas]

As long as the sensor area of your LPM is comparable to the pupil aperture, this is a perfectly sound method, provided your lpm can read power levels below 5 mW reliably.

When considering purely diffuse reflections the amount of power/mm2 decreases with the distance from the spot squared, and even at a foot away it would take tremendous power (>>10 watts) to create a diffuse reflection that would exposre your eye to over 5 mW.

The practical implication would really be that if the material you shine the laser onto is something like white paper, it would catch fire at a much lower power level than that required for a diffuse reflection to be dangerous viewed from a foot away.

Well, the sensor area on both of the LPM's is actually quite a bit larger than the pupil... which would further reduce the hazard. The two LPM's I used for testing were a usb laserbee, and an ophir.

The material was reflective tape. This tape to be exact; 2 in. x 36 in. Reflective Tape-PN03440 at The Home Depot

That's not good... no way to tell anything without testing though.

I have to call BS on this story! What college allows use of a class IV laser without a laser safety officer? These are extremely hazardous devices capable of causing serious damage to skin and eyes... not to mention if they are +1W output, a serious fire hazard.
A college allowing use without a safety officer is asking for a wild lawsuit on their hands.
Sounds like the poster is trolling!

Idk about that. It's possible, but in many situations students are left to run amok to a degree, once they show a measure of responsibility. I do find it odd that a laser would be handed over without some emphasis on safety though.

 

[Forestman]

That's why I asked if it was a university laser or privately owned. I suspect there are a lot of Class 4 lasers in universities that are privately owned and that's a scary thought given the nature of a lot of college students pranks. Yep, I watched Road Trip too

I also suspect that a troll might be at work here but nonetheless, it's worth erring on the side of caution.

Sorry to hear you guys think I am trolling.

All I know is that the individual on our group who has been in "charge" of the laser started to ignore the rules and regulations given to him by professors.

He thinks it's "safe" in certain circumstances. Obviously from my research he's an idiot. I had something done about it and this is why the power was turned down to around 50 mW. However I still believe this is unsafe. I just wanted to hear from the hobby folks if it was indeed safe or not since I don't know very much about lasers nor do I work with them. Only reason I'm even around this laser is because I'm working on this team project in school that happens to involve the use of a high powered laser.

Your input is appreciated.

 

[lazeristasUVISIR]

What kind of a laser do you use in your project?
Wavelength, pulsed or CW, any enclosures/tubes, eye-safety goggles.

If a laser is Class 4, it and you should have a lot of safety features, otherwise it should not be operated by individuals who are stamped as idiots.

 

[cheech226]

op never even stated the color.

 

[Forestman]

op never even stated the color.

Sorry here are the laser specs.

Wavelength

650nm

Power output

>900mW

Power Stability

5%

The Output Beam diameter(mm)

6*3mm

Divergence Angle(mrad)

<4mrad


Light central height

15mm

It's Red

 

[steveclv]

It is depend on laser length because some lasers not effects to eyes and some high reflected laser can scare to eyes. You should wear laser safety glasses during use to any type of laser because it will protect your eyes against all effects of laser.

I think I can understand what you mean and I assume English isn't your first language, but you are mistaken.

At >900mW it matters not what the wavelength is because any laser light produced from a modern diode will blind you faster than you can blink.

Secondly, safety glasses will not protect your eyes against ALL effects of laser - they are not designed for a direct hit and will ultimately fail (unless you have mega expensive glass lenses). Assume that safety glasses are a last line of defense - good operating practice is your first line of defense.

1. Do not operate a laser unless it is secured and cannot fall over.
2. Be aware of any reflective surfaces in the vicinity of the laser
3. Avoid other people entering the area when the laser is operating
4. Use the laser for the minimum amount of time for what you need it for
5. When you have finished using your laser, remove the batteries.
6. Treat your laser like a firearm, know where it is and who has access to it.

Plus all the regular stuff about never pointing at a person, building, window, animal or vehicle.