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"The issue with green laser pointers"

Zom-B

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Anyone know Brainiac75? I did't know this youtuber was that deep into lasers.

He made a good video explaining why cheap green DPSS lasers all emit harmful IR light and does several tests.

 
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paul1598419

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This keeps coming up from time to time, but few including your YT examiner bother with measuring the power of IR being emitted by the 532nm lasers. At worst it is 20% of the actual power of the laser as measured on a LPM. Also, the IR leakage is not nearly as collimated as the visible green beam on these lasers. This is what I call fear mongering by people who want to show the leakage from these green DPSS lasers with IR cards. I was using these same cards back in the 1970s to look at IR remotes and they are pretty sensitive to IR showing it brightly. You do need to "charge" the card first by exposing it to visible light for a few seconds, but then it can detect IR levels that are very low. The problem is they don't show relative power at all.

Also, since the IR leakage is not as collimated as the visible green light, it has a much lower power density at a distance than the green light does. So, worst case scenario with a 50 mW green DPSS laser is 10 mW of IR in a wider beam than the green light, so at 15 feet, the power density may easily be so small that you wouldn't get any affects from an IR strike without IR goggles.
 

Zom-B

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He addresses all those things. Either in the video or the comments. In one comment he talks about window panes that reflect 100% IR as a power saving feature. I then added to that with that most green-blocking goggles pass IR
 
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paul1598419

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Glass does not reflect 100% of any near IR light, so I have no idea what he might have been talking about with windows. At best they will reflect a % of the light striking them and pass the remainder.
 
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paul1598419

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If you are talking about IR filters, I bought a half dozen several years ago that block 97% of the IR and pass 95% of the 532nm light. I used them in some of my builds, but it wasn't worth the added effort as the amount of IR leaking is small and not well collimated.
 

Benm

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Also, since the IR leakage is not as collimated as the visible green light, it has a much lower power density at a distance than the green light does. So, worst case scenario with a 50 mW green DPSS laser is 10 mW of IR in a wider beam than the green light, so at 15 feet, the power density may easily be so small that you wouldn't get any affects from an IR strike without IR goggles.
This certainly is true, especially for the 808 pump light leaking out that is not collimated with the 532 nm at all. I would be slightly more weary of the 1064 line though, as that would be co-collimated with the 532 nm light at the source, though it may spread out faster than the 532 nm due to chromatic aberration.

There are really two things missing from this video:
- power measurements of the IR (and visible for that matter)
- distinction between 808 and 1064 light leaking from actual lasers during tests

I wound't totally disqualify this video though as he does have a point and at least demonstrates it to some degree. Also the point of using goggles that block both 532 and IR is good - especially when you're tinkering with lasers and viewing them at very close range where even the badly collimated IR could still pose a real risk.

There are still people that look down the barrel to see if there is -any- light coming out and seeing only a faint red light... when you do that right up to your eye it may not be well collimated but the power density of 808 nm light spewing from a defective 532 could be quite dangerous.
 

paul1598419

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Looking in the lens of a 532nm laser that seems to not be working is one of the stupidest things people do with these things. They are pumped with much higher powers of 808nm IR than the actual power of the green light. If the crystals are pushed out of the way or are just not functioning, you could get an eyeful of 500 mW to 1 watt of 808nm laser light directly in your eye. Never do this as a test to see if one is working.
 
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lasersbee

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Anyone know Brainiac75? I did't know this youtuber was that deep into lasers.

He made a good video explaining why cheap green DPSS lasers all emit harmful IR light and does several tests.

I saw that video this morning... Not that great.
Some of his logic is flawed or at least missing.

I commented on the missing info and data.
Good to make people ware of IR emitted by
cheap 532nm Lasers but his tests at ~2"
were skimming over the real power facts.

Partial fact Fear Mongering is what I saw.

Seems like all the "I got hit in the eye"
trolls were commenting as well.

Jerry
 
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paul1598419

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I'm not impressed with the videos I've seen by him so far. The only good thing about using an IR card was to show how divergent the IR was at a small distance from the laser. But, power levels of the IR were omitted completely. :undecided:
 

Benm

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True, i guess he did not have access to a power meter.

The video does demonstrate the IR is there with the cheaper pointers and not (or to a far lower degree) with the more expensive ones.

I can't really repoduce any of it either since i don't have one of those IR pass filters. I do have IR blocking filters, but looking at the power difference on a 532 with and without such a filter isn't really feasible.

If the difference is something like 5% it could simply be caused by insertion loss or reflection due to the filter, so if a 200 mW green went down to 190 mW with the filter inserted that would not prove there was 10 mW of IR in there.

Using a grating to split the IR off onto a different direction could be more effective, but that'd only work for the 808 nm light i think, has 1064 nm gets diffracted exactly double the amount of 532 nm, so they would still hit the same spot if they were co-collimated to begin with... which is quite likely since both wavelengths are formed in the same cavity.
 

Pelagius

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Thanks everyone for your interpretation.
I was attempting to light a match with first a 532 nm "Gatling Laser." Black match? Yes-in about 20-30 seconds at the focal point. The 303? Nope. I was using my Eagle 190-540 mm- and was no more than a few feet from the laser focus on the match. With the Gatling? No eye discomfort. With the 303? A dull eye ache (similar to what I get when I get too much reflection off of snow). The 303 Green spot is dimmer than the Gatling. I suppose the best solution is to TOSS the 303! From what I am reading from people who know a lot more than I-I suspect it's likely not IR-just accumulated eye strain. I have noted that any eye ache is always associated with the 303.
Not the 532 nm Gatling or the 1 watt 520 nm.


Still, I am accumulating much better lasers so ditching the 303 just means a loss of $10. I have a 492 nm being built at Sanwu right now. :)
 
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RedCowboy

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Wow a 492nm, please share some pics once you have it. :)
 




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