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Noob safety questions & laser power

platinumlazing

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Sep 21, 2022
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Hello all, laser noob here. TL;DR - Is it possible to safely use a 405nm laser above 5mw (at least powerful enough to clearly see the beam in low light conditions) without eyewear? What is the mw limit if so? Any recommendations on handheld 405nm lasers under that power limit?


I'm interested in 405nm lasers, mainly for fluorescence, however I am disappointed that I cannot see the beam of my 5mw laser without heavy dust or mist in the air, even in the dark(extra lighting added from my phone camera).
1663740085978.png
Compare this to my 5mw green laser pointed at the same object in the same lighting conditions and the beam is clearly visible (the extra lighting from my phone makes it way brighter than real life but it's clearly visible).
1663740260105.png
I know that green light is more visible than violet light, my point is that I would like to own a purple laser powerful enough to produce a clear beam that is eye safe to use, ideally that looks at least as good as this (my violet laser while I blow dust in its path):
1663743214326.png

Every time I have looked up safety information on lasers above 5mw everyone says to "get laser goggles", but they "don't know much about laser goggles" themselves. I've seen many posters link to goggles like these: https://www.survivallaser_com/Eagle_Pair_190540nm_Standard_Laser_Safety_Goggles/p556088_2780808.aspx and other similar ones depending on the wavelengths, and I have also seen many posters say that these goggles are insufficient and that much higher quality ones are needed, but can never link to a specific pair. Seeing that "high quality" laser goggles can go for upwards of $150 a pair(like these: https://lasersafety_com/product/f18-p5l10-5000/), I would like to see this backed up with a personal recommendation. Couple this with the fact that I see many videos of people using high powered (up to 1W) lasers without eye protection, indoors, seemingly without any permanent eye damage, leads me to believe that I could be able to use a higher powered laser without damaging my eyes. (see this video as an example: https://www.youtube_com/watch?v=7fsmf3ttCSQ)

Basically I want a 405nm laser powerful enough where I can see the beam that will not permanently damage my eyes. I've seen some people refer to "looking at the beam" as staring down the barrel of the laser, what I mean is more like what you see in the picture of the green laser, I want to see the beam like that.

My questions are:
1. a. What is the lowest power 405nm laser where the beam is clearly visible? b. Would that laser be safe to use without eye goggles given certain safety conditions (I will list some examples below)?
2. a. Assuming the answer to 1b is not no, what is the highest power 405nm laser that would be eye safe without eye protection given certain safety conditions? b. If such a laser would start fires easily(less than 5 seconds pointed at around the same place), what is the highest power commonly available (no 38.245mw lasers) 405nm laser that would not easily start a fire?
3. Going back to the eyewear, at some point I may want a 405nm laser which requires eyewear to use. How good are the Eagle glasses I linked earlier? If you think that these glasses are subpar, can you link to a specific pair you think is better for a high powered 405nm laser?


Absolute safety conditions (would be present regardless):
  • Laser would not be pointed at or near anyone(100% indoor use, would not be pointing outside at all).
  • Laser would not be pointed at glass, the surface of liquids, polished metals, mirrors, clear plastic, or other potentially mirrored objects. The laser would be pointed at various minerals that are a few feet away.
Potential safety conditions (Things I would have to do that I don't already in order to be eye safe using a high powered laser without eyewear. Let me know if any of these are correct or applicable, or add anything you think is necessary to the list):
  • Keep a certain distance from the laser dot.
  • Only shine the laser dot at dark objects.
  • Wear sunglasses or other eyewear where the beam and color are still visible.
  • Only use the laser for a certain amount of time at a time (For example should I have laser on 5 seconds off 30? Would that even help?)
For example, take this post on this forum: https://laserpointerforums_com/threads/at-what-mw-%C2%A0do-i-need-to-wear-goggles.38474/ - some posters say that a laser up to 30mw could be safely used without much hazard, while others say that you should limit it to 5mw, and the reasoning given for the 5mw limit is that if the laser is directly in your eye you only have enough time to blink before permanent eye damage with a 5mw or lesser laser - however if there are no mirrored surfaces for the laser to reflect into my eyes, what would be safe?

As for the laser I'm considering, I was looking at getting the 10, 50, or 100mw version of this laser: https://biglasers_com/product/purple-laser-pointer/ based on the responses to this post, but if anyone has any other recommendations (like one I can get with or is compatible with a beam expander, or has easily adjustable power output) I'm open to other options (must be handheld, preferably small and portable but if its big and has additional useful features I'd consider it).

If you've made it this far thank you for reading my ted talk, hopefully the replies to this can help other noobs who see this conflicting safety information (and help me decide whether I want a more powerful laser right now).
 



WizardG

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Even @ over 500mW a 405nm laser beam doesn't look particularly impressive. Our eyes just weren't designed for this wavelength. If you want a highly visible 405nm beam you'll need watts, not milliwatts.

The danger isn't looking at the beam from the side, it's reflections. You'll be pointing this at mineral specimens? Will any of those have tiny crystalline bits capable of reflecting a portion of the beam that's still at least somewhat focused? Then good safety glasses are a must. I'll let others weigh in on the best safety glasses but $150 is a low, low price for undamaged eyes.

At the kind of power you'd need to have the beam be as visible as your green laser there is no margin for error. For making your rocks glow there are plenty of UV LED choices available that would be much safer.
 




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