Increase in Number of Classification Intervals

[MaZuh]

I believe that class IIIb Lasers, >5mW-<500mW, should be split into more sections. This is because it is like placing an Airsoft gun into the same category as a machine gun. One could be 6mW that can't even cause damage from a reflection to a laser that is capable of burning. That way an entertainment laser, say around 30mW can't be mistaken for a harmful one by simply a category. The FDA needs more subcategories within IIIb lasers.

 

[Bluefan]

No they don't need more categories. Class 3 is already divided into IIIa and IIIb (or 3# and 3B). The categories are fine:
Class 1: always safe
Class 2: safe for a 0.25s exposure (fast enough to blink/look away)
Class 3R: Exceeds MPE but low risk of eye injury.
Class 3B: Dangerous for direct and reflected beams. Diffuse beams are safe
Class 4: Dangerous for eyes and skin. Fire hazards. Diffuse reflections unsafe.
This works fine for pretty much everybody. Whether it's 6mW of 500mW, you need appropriate laser safety eyewear.

One could be 6mW that can't even cause damage from a reflection

INCORRECT

 

[Benm]

Class 3B is still very broad though, or class 3R is narrow, depening on how you look at things. Perhaps it would be useful to have an intermediate class (5 - 50 mW) of lasers that are dangerous, but not insanely so.

The problem with 3R is that it is worded 'safe, but only when handled properly'. I've always found that odd, since any laser is safe as long as you handle it properly.

 

[Cyparagon]

If anything, class 4 should be sub-divided. A Q-switched YAG is several orders of magnitude more dangerous than a 500mW laser diode, but they are both in the same class.

 

[anselm]

What makes much less sense to me is the fact that a 500mW and a 100kW laser are
in the same class.:thinking:
Oops, cyparagon is too fast for me.

 

[Benm]

Perhaps, but then again class-4 just means 'bloody dangerous and will possibly set stuff (or staff) on fire'.

I think the main reason that there are no further classes is that people using class 4 lasers usually know the properties of the lasers well, and take precautions accordingly.

The 445s that run a watt or two are probably the first class 4 lasers that ever got in the hands of the public. Up to this point there was nothing that looked like a laser pointer and produced this much power.

 

[Bluefan]

Class 4 is like "don't get hit by the beam anywhere and it sets things on fire". Works for 500mW and 500W. Safety measures like beam termination and laser safety eyewear scale with the laser power, that doesn't make different scales.
Class 4 lasers are now easily available for the general public, but the general public doesn't know much about laser safety. Before the high power pointers there were huge argon lasers and the like. If you owned one of those you knew what you had. Too bad that doesn't work anymore.

 

[Benm]

Indeed, now the 1 watt lasers are more or less available this is a problem. The additional problem is that the average consumer is not aware of what safety classes mean, or that those even exist.

 

[LSRFAQ]

There once was a class V safety level. It was decided eliminate it to reduce the complexity of the levels and make IV cover everything. If you ever get to work with anything well into IV, ie in the tens of watts region, you will quickly see why four is enough.

Its bad enough having to remember the new IIIM and IIIR classes for certain light sources as well.

If you read deep enough into Dr Sliney's books, you will find that the levels are based on long ago animal tests and cadaver tests, statistics, and built in safety factors, done in the 1970s.

IIIAs levels might be chosen for ensuring less then a 1 in 9,999 incident probability of detectable damage. One day I will go back and look up what that number really is.

A warning for the simple minded. Just because its only a 1 in 9,999 chance of damage, don't assume you can try something five times and quit. The math and the reality does not work that way.
Its still Russian Roulette to do so.

One should not suggest changes to existing laws that work. Back then engineers and scientists wrote the laws, lawyers cleaned up the language, and it was good. Now, a lawyer consults a engineer, laughs, and then writes what the highest bidding lobbyist wants. Often Not good!

The OP does have a valid point, the 4.95 mW of IIIA could possibly be taken up to say 15 mW if the beam size is not too small. However the safety factor starts to erode. Real damage thresholds are in mW per square centimeter, but for simplification and ease of understanding, it was decided to use total beam power.

Steve

 

[ixfd64]

The OP makes a good point. For example:

A 501 mW laser is a class IV laser
A 3 W laser is a class IV laser
A 10 TW research laser, strictly speaking, is also a class IV laser

 

[chipdouglas]

The OP makes a good point. For example:

A 501 mW laser is a class IV laser
A 3 W laser is a class IV laser
A 10 TW research laser, strictly speaking, is also a class IV laser

i might just be a simple thinker but i look at laser power as how it affects the eyes. our skin can stand much more pain. than the eyes. so i say 500mw will do the same to the eye as a 3W.

or if you compare it to fire on skin. you can pass your hand over a bic lighter, or a camp fire or the tip of a plasmer cutter with out much harm. but try any of those on the eye and it is a whole different story.

 

[Bluefan]

Safety measures always scale with the laser power, a 0.5W laser requires different laser safety eyewear then a 500W laser. Putting that in different classes requires a lot of classes. What separates class 4 from 3B is that in class 3 you only need eye protection but in class 4 you need to make sure nothing gets in the beam and the beam is safely terminated. This goes up to terawatt power level.
The same for class 2 and 3. Class 2 is safe with a normal blink reflex, class 3 requires laser safety eyewear. The eyewear is different for 5mW or 500mW, but that's it. Else you would end up with a class for every tenfold of laser power and different for different type of pulsed and continuous lasers. Separate classes for beam size and wavelength and you'd have hunderds of classes.
Laser safety always requires knowledge of the laser, classes aren't ment to completely tell everything about the laser.

The total beam power doesn't always determine it's class. DVD players and the XBOX kinect are an example. I have a pulsed YAG laser from a laser rangefinder with a label Class 3B and a large beams diameter.

 

[Benm]

I suppose the classes system is just one way of defining danger.

If you have a 10 watt laser but the beam is even and a meter in radius, it would probably be safe to look straight into the beam. This would be an example of a class 4 laser yielidng illumination within MPE limits.

On the other hand, if you focus 200 mW for bluray onto a pinprick, you'd easily burn your skin on that, despite the laser being only class 3B.

Power density is often as much a factor as total power in hazards. The MPE system is all about that, and the class system is not. One problem with it would be that a laser of given power would be in a different class up close than far away, since the beam diverges and the power density drops.

 

[LSRFAQ]

This may shock some of you here, but I have "burned" things with a 6 mW hene laser. Its all in the quality of your optics and initial beam quality. Granted the target was mounted on a high grade insulator, and was a dark metal film, but a burn is a burn. Power density matters.

Take that in perspective when you think what class IV is.

Steve

 

[Cyparagon]

But whether a beam is 1mm or 3mm, the eye's lens will (ideally) focus it to the same size spot. At the retina, the power density will (ideally) be nearly the same.

 

[Bluefan]

A 3mm beam creates a smaller spot size with the same focal length. As long as both beams aren't clipped by the aperture of your eyes the beamsize matters for the spot size.