How much power do IR filters reduce?

[360freak]

If I were to buy say a 200mW DX greenie and put an IR filter in it, how much output power would the IR filter reduce?

 

[Ace82]

The 200mW is supposed to be the power of the 532 only, but roomer has it DX includes ir in their overall power rating as well.  I've heard up to 30mW!  But, it isn't collimated so you shouldn't notice a significant loss (further then ~ 2' from aperture, less then ~2' might reduce burning power).

 

[Benm]

I second the above, an IR filter should cause no loss of visible power apart from its insertion loss at 532 nm, which should be in the order of a percent or if its AR coated. For an uncoated filter you can expect losses up to 4% over the entire range due to reflection (back into the laser, that is).

 

[Switch]

If I were to buy say a 200mW DX greenie and put an IR filter in it, how much output power would the IR filter reduce?

It basicly reduces 90-something percent of all the IR that is leaking out and a really small amount of the green.Can't really say for sure how much of the total power of a laser it reduces, it depends on the laser.

 

[360freak]

Is it ok just to glue the IR filter to the inside of the hole at the end of the pointer?

 

[IgorT]

I tested a filter from a CNI laser, and it takes 6% off of my already filtered CNI...

But you probably don't have to worry about IR. There is very little left due to the way the laser is built, and the little that is left is highly divergent... It can be somewhere in the vicinity of a stronger IR LED, in power as well as spread..

You should be much more worried about the green beam hitting your eyes, or an unexpected reflection.


IR was much more of a problem, when the crystals had a much lower efficiency, and a more powerful pump had to be used. The IR vs. green ratio was much higher, and the IR was collimated, before it entered the crystals.

In these lasers, the IR enters the crystals uncollimated, while the green comes out very narrow.
This is then expanded with the expamnder lens, along with a little IR, while the nut blocks most of the IR.
The collimator nut again mostly collimates the green, a little IR, while the nut holding it blocks most of the remaining IR.

Then, if the laser has a tube extending further up from the collimator, ending in a narrow aperture, this again mostly lets the green pass while blocking most of the little IR that is left.


When i was taking green lasers appart and putting them back together, i observed the amount of IR decreasing at each of these steps.

At the expander there is a huge IR glow, at the collimator it is smaller, and at the apperture, it is MUCH smaller. If produces maybe a lens flare, but doesn't blind the camera..


When i measured my lasers with a known transmissiveness IR filter, and then added the percentage back to the green, that it takes away, i got the same result as if i measured directly.. The little IR left is hardly measurable.



Otherwise, yes it is safe to glue the IR filter into the cap from the inside. Just be careful, that you don't get glue on the middle. But most likely it is not necessary, and will decrease your green output. Not visually noticeable, but measurable.

 

[360freak]

I've heard a million warnings on the IR of DX lasers, so I'm going to put one in when I buy one. Thanks.

 

[IgorT]

I've heard a million warnings on the IR of DX lasers, so I'm going to put one in when I buy one. Thanks.

Well, as i said, without a meter you won't even notice the difference in the green power. And if you glue it in from the inside, it won't look ugly. Just be careful, that you don't smear the filter with your fingers. And make it so, that you can remove it for cleaning.


Otherwise, i have heard the same million warnings about IR as you. But i tested a number of these lasers, and i have yet to find one, where the IR would be dangerous. People should really be more worried about the green beam itself.

 

[VW]

With my Spartan I can remove the lens cap and I would say it some what reduces the quality of the beam.  I don't really see any improvement other than a blue hue around the laser head.  I think the point is that what's supposed to be emmited is 473nm (for example), not 473nm + IR.  One form of light is bad for you, another form of light you can't even see is just going to make it worse.  It doesn't need to be there, if anything it's a hazard.  Kind of like polution, it seems harmless but all it's really doing is making matters worse, no matter how little it seems to effect you.

 

[RA_pierce]

People act like IR is some kind of evil entity that consciously attempts to blind laser hobbyists.
IgorT explained it pretty well, I think. IR isn't as hazardous as everyone seems to think. Standing outside in the sun exposes your eyes to more IR than a DPSS laser does.

 

[spark001uk]

i think its about 5% isnt it?