IR collimation with green in pointer

[Benm]

There have been quite some discussions about the dangers of IR leaking from green pointers here. One of the issues is whether or not the IR is combined with the green beam. Some say it is, some say it comes out in more of a wide flashlight pattern.

My LS50 pointer was running out on its batteries, to a point where there was just a tiny tinge of green left, but IR was still coming out (insufficient for the doubling process to work well). I was able to take a pic with a camera thats a bit ir sensitive - see below. I had to use a page with some text on it to get the AF to 'bite'.

Distance to the paper is about a foot, and you can see the IR pattern is about twice as wide as the green (drawn circle matches green beam size in normal operation). At the point this picture was taken, total output was lower than a few mW (i have nothing to measure lower power levels).

I'd conclude that whenever you would be hit by the IR in the beam, you're poiting the green portion dangerously close to your eyes as well.

 

[murrat]

You are absolutely right

You can read this thread http://www.laserpointerforums.com/forums/YaBB.pl?num=1234914014/0

 

[Cyparagon]

Let's say you have 80mW of green and 20mW of IR. The IR is double the diameter which means it covers four times the area for a total of one eighth the power density of the green beam.

Why would the beam be 4 mm from your pupil to begin with?

 

[Benm]

Right.. the only way you could shine IR into your eye by accident is when you are.. well.. having your eyebrows laser-trimmed from accross the room

In any case, it makes a good argument against asking for IR filters on greens, since those do cause a loss in green output, while they don't improve safety much.

One dangerous scenario is when a laser runs low and someone stares in to the barrel to see what's going on - but that's just plain stupid and could seriously hurt your eyes even with a filter in place... on the off chance that the laser decides to kick in again at that time

 

[styropyro]

Here's a picture of the IR from an unfiltered greenie I have from about 35ft. This roughly puts the divergence of the IR from the laser at about 2.5mRad.

 

[ElektroFreak]

All of these replies have overlooked the real danger of IR from laser pointers. If a beam containing both IR and green gets passed through a prism, the IR and green beams will be separated at a fairly large angle. This same effect can be observed by passing the beam through a pane of glass (although the angle at which they separate will be smaller). It's the unpredictability of having the IR become separated from the green that is the real concern. Unless you can guarantee that at NO time whatsoever will the beam EVER be reflected or passed through a prism- or dichro-like surface, then you can't guarantee complete safety.

Their your only eyes, why take chances? You can't afford $10 toward your eye safey? Just go buy an IR filter rather than waste time here talking about how it may or may not be safe.. What's $10??

The bottom line is no amount of speculation by people who have no clue about the true dangers of IR will lead to useful conclusions.

If you believe the dangers of IR are a big joke or some kind of hype to make more money, then buy yourslf an 808nm dilda from o-like and shine it directly into your eyes, then do us all a favor and do a writeup on what happens. Apparently the only way to prove it to some of you is for someone to blind themselves. {THE PRECEDING STATEMENT WAS OBVIOUS SARCASM}

 

[Cyparagon]

You don't understand. With DX pointers: low power, and low power density. O-like 808 pointers: high power, potentially extremely high power density.

why take chances?

... what chances? What chance is there that you'll be blinded by the IR and NOT the green?

Did you know incandescent bulbs emit UV? It's a very small amount, but why take chances? Use candles.

More crucially: did you know over 40,000 people are killed and millions injured in car crashes EVERY YEAR in the USA ALONE? Why take chances? Walk or ride a bicycle.

What would your life be like if you never took chances that didn't need to be taken?

 

[RA_pierce]

If you believe the dangers of IR are a big joke or some kind of hype to make more money, then buy yourslf an 808nm dilda from o-like and shine it directly into your eyes, then do us all a favor and do a writeup on what happens. Apparently the only way to prove it to some of you is for someone to blind themselves.

That's a completely different case than <30mW of IR leakage from a DPSS laser.
Nobody is saying a Class IIIb IR laser is not dangerous.

The point that is being made is that IR leakage is generally negligible and only poses a threat to people who are careless and dangerously close to the green output anyway.

I can second this. Of the several greens I have owned, the IR leakage does not diverge like a flashlight, but rather it remains pretty close to the divergence of the green. This is true for all my green lasers except one. On this laser, the IR output is about 2 inches across at 3 inches from the aperture. The green output is only 5mW so the IR leakage can not be more than 1-2mW.

 

[691175002]

ElektroFreak has a point here, and by claiming that the IR has low divergence you are only reinforcing his argument.

Instead of a single beam coming from a green pointer you have two, both of which can blind you, but only one that you can see. Normally these two beams stay together so if you aren't looking into the green, you aren't looking into the IR; however they can split up under certain circumstances, such as reflection off a diffracting surface (such as a CD), refraction through a prism or glass, and potentially even reflection off a non-front surface mirror.

Once this happens the situation becomes completely different, you no longer have a single beam, you now have a second invisible beam which can potentially blind you and is traveling in a completely different direction to the green beam.

Would you feel safe if your green laser had a built in IR laser that shot at 90 degrees to the right?

 

[Hemlock_Mike]

Once again, science is needed here. Use IR pass filters and meter the IR output. I have done this long ago, reported my results and I am not scared of IR scatter. Keep your nose away from the output.
Many people rehash what others have said - without testing and it goes on and on -- like globule warming.

Mike

 

[rog8811]

What chance is there that you'll be blinded by the IR and NOT the green

Not a good argument, we have a built in blink reflex, if a green beam hits you that reflex may save your vision.... there is no blink reflex with IR.

Regards rog8811

 

[ElektroFreak]

You don't understand. With DX pointers: low power, and low power density. O-like 808 pointers: high power, potentially extremely high power density.

[quote author=ElektroFreak link=1235262582/0#5 date=1235339157]why take chances?

... what chances? What chance is there that you'll be blinded by the IR and NOT the green?

Did you know incandescent bulbs emit UV? It's a very small amount, but why take chances? Use candles.

[highlight]More crucially: did you know over 40,000 people are killed and millions injured in car crashes EVERY YEAR in the USA ALONE? Why take chances? Walk or ride a bicycle.
[/highlight]
What would your life be like if you never took chances that didn't [highlight]need to be taken?[/highlight][/quote]

I understand your argument here, but if I thought that I could spend $10 and save one of those people, I would.. This entire issue could be rendered moot by buying a cheap filter.

Sure, by all means take as many chances as you want. That doesn't mean we all have to take the same chances as you.. There's a lot to be said for trying to educate people about possible risks posed by using lasers. I believe it's better to try to make the dangers known and then let everyone figure out what risks they want to take for themselves.

I'm not trying to make people nervous by pointing out these dangers, in fact at times in low powered systems IR poses little or no danger. I just hate to see blatantly false statements get passed on as the truth..


Why do chances with IR "need to be taken?" I see no need for it save for being completely unable to afford to buy a filter. If that's the case then I advise you to just be careful and avoid shiny surfaces...




EDITed

 

[Hemlock_Mike]

EF -- We all subscribe to safey here.
What data have you gathered with your meters and filters ???
My testing using IR pass filters and Scientech meters show little IR leakage. Cameras can vary widely in IR sensitivity and provide no science.
In higher powered portables, the design needs all the 808 available to make green.

Mike

 

[691175002]

I have not done any testing, but people say that IR may make 10-20% of a cheap greens power. When dealing with a 50mW pointer I would consider 5-10mW of IR potentially dangerous even with its high divergence because you lose the blink reflex and can be completely unaware you are getting hit.

 

[ElektroFreak]

EF -- We all subscribe to safey here.  
What data have you gathered with your meters and filters ???
My testing using IR pass filters and Scientech meters show little IR leakage.  Cameras can vary widely in IR sensitivity and provide no science.
In higher powered portables, the design needs all the 808 available to make green.

Mike

My tests show little IR leakage as well depending on the setup. I have a 100mW module I bought from DX a year and a half ago that averages about 123mW and loses about 30mW when I pass the beam through an IR filter. 28mW give or take of IR alone is enough to pose a mild hazard, and there are non-IR filtered Chinese greens that go up to 200mW, maybe even higher. These, to me, pose a true possible hazard. Even if it is fairly unlikely that the IR would come into direct contact with any retinas, I still think that the point should be stated. Being too comfortable with a hazard is what leads to accidents.

As I just said, I'm not trying to make people nervous, and I don't really want to ruffle anyone's feathers either but I've seen a few threads around here lately that contain posts insinuating that the IR danger is just cooked up to bolster profits for the manufacturers, or just to freak people out. I can't support this line of thought given the possibility of the green and IR becoming separated. That's all I mean...

I do want to add, however, that I do feel that manufacturers charge way too much more for an IR filtered laser versus non-IR filtered. It's a $10 piece of blue glass..

 

[Hemlock_Mike]

I have not done any testing, but people say ---------


I lived through many cycles since ~ 1950 ---
1. Crude oil will be gone by 1980...........
2. We are going into another ice age ...........
3. The Ozone hole will kill us all ............
4.  OMG, the Y2K bug will destroy all of us.
5.  Globule warming -- I'd love to see some of that  

What I'm saying is show me the science.  Things like IR leakage get repeated enough times to become truth and take on life.  The people who repeat these "facts" seldom have the equipment to verify those "facts".

Mike

When using a filter, something must be used to account for reflection and absorbtion of the filter. I have an 808 nM pointer to provide reference on my filters.