IR danger clarification

[EmoticonFury]

I have a 50mw with no IR filter. I realize that I could add one relatively easily, however I had a question about the nature of the excess IR. My understanding about what makes the green unsafe is that laser safety goggles are useless against it and it's invisible so the eye doesn't react to the IR to protect itself while doing damage. I know that since this 50mw is a class IIIB non-specular reflections should theoretically not cause eye damage without eye protection. I'm wondering, however, if viewing the laser green laser "dot" with IR is still eye damaging since by the above logic the eye's iris in shouldn't react and shrink to the same extent to deal with the full "brightness" of the laser like it would for a standard laser within the visible spectrum since a percentage of the energy output is invisible. Anyone know if this is actually the case as well?

 

[ElektroFreak]

The IR leakage will be so slight from a 50mW green that IR filtering is not necessary. Also, any stray IR will be confined to the output beam, so as long as you don't stare into the beam (which is always a bad idea anyway) you'll be fine. Since the residual IR is typically not very powerful, your eyes' reaction isn't too important.

 

[LSRFAQ]

This question really depends on many, many factors relating to the design and quality of the pointer, and if it has a IR filter installed. IR filters in Chinese lasers are usually a blue-green piece of glass at the end of the optics train.

The IR scatter is usually almost always Ok from a distance of two or three feet, except in really high power devices. The easiest way to be sure to avoid DIRECT IR without instruments is to keep your head out of a 25 degree wide cone around the end of the laser for a distance of say 3 feet.
I'd follow that rule to say 75 mW. ABOVE THAT, ALL BETS ARE OFF.

You'll find lots of posts here where one user assumes his measurements or logic applies to all pointers and other DPSS. In reality it depends on a case to case basis.

The easiest way to find the 808 nm pump light would be a IR capable black and white security camera or older black and white web cam. Some color cameras will view really BRIGHT IR, but most color cameras have a IR blocking filter. If its there, its a diverging halo around the green beam.

The response of a silicon or CCD camera to 1064 nm leakage is NIL. The easiest way to find any 1064 is with a IR viewing card or IR image converter and a prism or transmisson grating. 1064 will tend to be very weak and colinear with the 532 nm beam. 808 usually is diverging fast if it leaks out, because it diverges rapidly past the monolithic crystal in the laser. 808 nm pump is focused inside the laser to create enough energy density to pump the YAG, thus it does not come out of the yag at a optimal angle for the collimator to work, and is diverging like mad.


That is NOT to say it is weak in all designs and qualities of laser. Most manufacturers put the filter in, for a reason. A 30 mW laser is not likely to leak much IR, but again, at 1$ a mW, you have no idea what your getting. You should never look down the bore at a laser that stops emitting green. That is when the real IR hazards can arise, when the pointer has been dropped or tampered with.

Therefore err on the safe side. The primary rule is NEVER get exposed in the first place. The secondary rule is observe and measure until your sure. The Other rule is NEVER trust anybody who does not document experience with YOUR laser.

8 years as a university LSO. Working with IR and Vis lasers since 1986.
Well, some folks say 1776.

Steve

 

[Pontiacg5]

Just looking at it should be ok, but if you were to try burning up close the specular reflections might do some damage. The green glasses protect you from the green reflections, but not the IR.

As long as you use it as a normal pointer I would not worry about the IR.

 

[Benm]

This has been a subject of much debate around here.

I think what was most commonly found is:

- green pointers leak very little 1064
- green pointers sometimes leak high amounts of 808, but not collimated with the green

Combining those observations would suggest that IR is not a big safety hazard if viewing the laser from far away, or the dot unless its really close to your eyes. However, there is no hard guarantee that above statements hold true to every single dpss green, even if they aren't malfunctional.

The best practice is still to avoid exposure until you have prove that it doenst pose a danger. I know thats not a very satisfactory answer for practical use, but it is the only valid one i can come up with. Choosing to take a risk regardless of it is obviously entirely your own decision, which i would understand entirely, but never endorse.