Infrared lasers?

[ohisthatright]

I'm really confused about all this IR talk. From what ive read it sounds pretty bad for you, people have been saying that you should always buy a green laser with an IR filter, but then why are there infrared lasers? Why does my green laser need to have an IR filter?

 

[Ash]

I'm really confused about all this IR talk. From what ive read it sounds pretty bad for you, people have been saying that you should always buy a green laser with an IR filter, but then why are there infrared lasers? Why does my green laser need to have an IR filter?

Well, to put it simply: Your Green laser is actually an IR-laser that's put through a crystal to change the color to green and if you don't have an IR filter on it (cheap green pointers), some of the Infrared light is escaping.

Here is a pic of the crystal (Nd:YVO4) from a green pointer.

If your green pointer is above about ~30mw and has no IR filter, I would avoid prolonged eye exposure (even to the beam or dot) without IR safety goggles.

 

[Gryphon]

In addition to what Ash said, the IR that is escaping is not collimated like the green light. Different wavelengths bend at different angles relative to one another, thats why you get a rainbow from a prism, cuz each wavelength will bend a little more or a little less than the next. This is a problem with green lasers without IR filters cuz the IR spreads out, or is less colimated than the green so you could potential be exsposed to it and not know it.

 

[AdamR]

^ having said that, you are probably exposed to more infra-red by standing outside on a hot day

 

[Cyparagon]

If that were true, it would be nearly impossible to burn ants with a magnifying glass. There's quite a difference between a prism and a lens.

 

[XCreedX]

Well your just taking the light outside and focusing it to a dot with a lens, same concept with a diode, scattered light into collimated focused light.

 

[Switch]

Saying that it's not collimated isn't exactly accurate.Those green lasers are all different...I've seen ones that have the IR very well collimated, and ones that have it scattered all over.So you never know...

IR from green lasers isn't any more bad for you than any other light from the visible spectrum (after all , it's pretty close to the visible spectrum at 808nm or 1064nm). The extra danger lies in the fact that you can't see it so you can be looking at it and not notice it and not have the blink reflex.

 

[RA_pierce]

Well, to put it simply: Your Green laser is actually an IR-laser that's put through a crystal to change the color to green and if you don't have an IR filter on it (cheap green pointers), some of the Infrared light is escaping.

Here is a pic of the crystal (Nd:YVO4) from a green pointer.
If your green pointer is above about ~30mw and has no IR filter, I would avoid prolonged eye exposure (even to the beam or dot) without IR safety goggles.

I've been debating the danger of IR leakage from unfiltered green lasers for a loooong time...
I'm collecting a few >100mW lasers of different types to compare them and TEST the inherent danger of IR with an LPM, This way, we can have some cold, hard facts... and decide whether or not it is really necessary to wear IR goggles for <30mW of IR vs. the >100mW of green. *no emoticon- insert rolling eyes*

 

[Warske]

Saying that it's not collimated isn't exactly accurate.Those green lasers are all different...I've seen ones that have the IR very well collimated, and ones that have it scattered all over.So you never know...

That is correct, and its easy to check. Just put an IR pass filter (or even red plastic) on your digital camera and take a picture. Then you will know.

The real problem is when you wear safety goggles designed to protect you from your green laser. Most people seem to be buying goggles that protect against the green only, and not against the IR.

If you have such goggles and your green laser emits relatively well collimated IR, then you should wear your goggles whenever you can (because they will make you look cool) EXCEPT when you are playing with your Green/IR laser. The reason for this should be obvious, but I have never seen it mentioned on this forum before.

For example, a nice 50 mW green pointer that I measured recently puts out 13 mW of well collimated 1064 nm IR. Think about that IR going straight through your goggles and into your eye while you are thinking you are well protected and not even noticing that something is wrong.

You are arguably better off NOT wearing Green-only protection goggles around such a laser. At least then you will 1) probably be more careful 2) be more likely to blink if part of the beam hits you.

If, on the other hand, your green laser has a good IR filter, OR your goggles protect you from both green and IR, then wearing the goggles when using the laser is a very good idea.

BTW, this applies (appropriately modified) to DPSS blue lasers as well.

 

[RA_pierce]

Think about that IR going straight through your goggles and into your eye while you are thinking you are well protected and not even noticing that something is wrong.

You are arguably better off NOT wearing Green-only protection goggles around such a laser. At least then you will 1) probably be more careful 2) be more likely to blink if part of the beam hits you.

I wonder how one would manage to get that 13mW directly into their eye... Even with goggles, it's not smart to direct any laser into your eye long enough to cause damage.

And to the second part, no.
I would much rather be hit by <15mW of poorly collimated IR than 50mW of well collimated green. Any day.

As I said, I'm going to TEST the IR leakage on several different lasers and hopefully relieve some of this irrational paranoia and misunderstanding.

 

[Warske]

I wonder how one would manage to get that 13mW directly into their eye... Even with goggles, it's not smart to direct any laser into your eye long enough to cause damage.

I could mention reflections.

Assuming we are talking about lasers of 500 mW or less:

If you aren't concerned about getting a direct beam hit to an eye (your's or someone elses) then what are you concerned about?

Seriously, what do you consider the damage mechanisms to be?

 

[Warske]

And to the second part, no.
I would much rather be hit by <15mW of poorly collimated IR than 50mW of well collimated green. Any day.

I absolutely agree with you.

I specifically said "well collimated 1064 nm IR"

 

[RA_pierce]

I absolutely agree with you.

I specifically said "well collimated 1064 nm IR"

I read incorrectly then.

13mW is still less power than 50mW.

I'm not sure what you mean by:

Assuming we are talking about lasers of 500 mW or less:

If you aren't concerned about getting a direct beam hit to an eye (your's or someone elses) then what are you concerned about?

Seriously, what do you consider the damage mechanisms to be?

Do you mean 500mW green lasers or 500mW of IR?

Whenever I say "IR leakage from (x)mw green lasers is negligible" someone assumes that I am saying it's ok to shine IR lasers in your eye.

What I am saying, and what I have always said is:

IR leakage from common green lasers (up to 100mW) is negligible when the laser is operated with use of common sense. The green output is far more dangerous and proper safety should be exercised with any laser device.

I am not anti-safety laserist.
I just think some dangers are exaggerated.

 

[GooeyGus]

DONT WORRY ABOUT THE IR. THE GREEN IN THIS CASE IS WAY MORE DANGEROUS.

You probably get more IR exposure just standing out in the sun than you will from a green laser pen. The IR has to go through many obsticles and is not collimated. Even if you had 20mW of 808/1064 coming out (which is doubtful in the first place) it's all spread out... you could point it directly at yourself and probably only get around 1mW or less into your eye. MEANWHILE you're being blinded by an ass load of green in a tightly focused beam, which only gets focused tighter in your eye.

I'm sure you've all seen an uncollimated diode, that's basically what is happening to the IR light, but it's probably spreading even faster. Now, take an uncollimated diode and put a 3mm aperture about 1.5" away from the diode and see how much light actually makes it through that hole. Even if you have a diode doing a few hundred mW's, not very much will make it through. NOW add a big chunk of metal with a 1mm hole inbetween your diode and the aperture, this represents the crystal set. You will quickly realize that even with a ton of pump power, not very much is making it out the end because A) is uncollimated and hits the inner walls of the laser before it ever makes it out and B) theres a ton of crap in the way of the IR source.

IR light is no more damaging than visible light... people seem to freak out so much over it. Worry about the green, not the IR.

This brings us to the next topic. Why are people so concerned with IR filters? Well, I'll tell you why.

People wanted IR filters so they knew EXACTLY how much green they were getting. Most people were using optical meters since thermal heads weren't within a good price range yet. When an optical meter is set to 532nm, even 1mW of 808 can skew the reading by 10's of milliwatts. So, people wanted IR filters to be able to know exactly what their laser was putting out.

Somewhere along the lines this got skewed in to a wacky safety issue and was just potentiated as the forums grew, because newer members would stress the need for an IR filter without knowing the reasons behind it.

Bottom line, again, worry about the green.

 

[Warske]

GooeyGus, you have done a nice job summarizing what everyone on LPF "knows." I believed it too, until I actually ran some tests. It's clear that you have never done this.

The amazing thing is how very easy it is to run the tests, but apparently nobody bothers because they all "know the TRUTH!"

I find this absolutely fascinating. Its similar to how, not so long ago, everyone knew that the world was flat, despite evidence to the contrary.

The fact is, I don't particularly worry about IR, but I like to know what the hazards are. "What you don't know can blind you."

 

[Warske]

RA_pierce, I'm sorry it took me a while to get back to you on your questions.

Do you mean 500mW green lasers or 500mW of IR?

What I meant was lasers where the primary damage mechanism is to the eye, as opposed to some kilowatt military lasers used to destroy missiles. So this could include green or Near IR or some combination.

IR leakage from common green lasers (up to 100mW) is negligible when the laser is operated with use of common sense. The green output is far more dangerous and proper safety should be exercised with any laser device.

If no one is wearing goggles, I agree with you.

If every one in the area is wearing goggles with both green and IR protection, I agree with you.

Where I don't agree is when green protection goggles are used, and there is no IR protection. That was the point I was trying to make in my original post.

What people here don't understand is that while the 808 nm generated by the laser diode isn't well collimated, the 1064 nm generated by the crystal IS well collimated. Enough so that you can get its full dose in your eye at a distance of several feet.

Probably the reason they don't understand is that they can see the 808 nm quite well, but they can't see the 1064 nm without a camera. So they assume that all of the IR behaves like what they can see, and it is harmless. Unfortunately, they are wrong.

So look again at using green protection goggles w/o IR protection. If the beam accidentally hits your eye, then you are going to get less than 1 mW of green on your retina and 13 mW or more of IR on your retina, depending on the laser.

How is the IR negligible in that case?

And how does "use of common sense" change that?

No one is talking about deliberately aiming this thing into your eye. We are talking about accidents. If you deny the possibility of an accident, then there is no reason for anyone, anywhere, ever to wear laser safety goggles. Is that what you believe?

I stand by what I wrote in my first post in this thread:

"If ... your green laser emits relatively well collimated IR, then... You are arguably better off NOT wearing Green-only protection goggles..."

I just think some dangers are exaggerated.

We do agree on that. I am not telling anyone they have to use safety goggles or IR filters. That is up to them. But to use "common sense" it helps if you know the facts. I am trying to help with that.