Questions about a 7W handheld

[steve001]

I have. If there is something you think I've missed, provide a link. :thanks:

I don't know what you've been reading but it probably wasn't these three sites. These articles describe affects of blue light from lower intensity leds save the first article. I wonder what retinal damage is done by a significantly brighter 7W 445nm laser?
http://www.archlighting.com/technology/blue-light-hazard-and-leds-fact-or-fiction_o<br>
https://ehp.niehs.nih.gov/122-a81/

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4734149/

 

[Richie89]

someone should do a series of tests having a laser pointed at a surface with an lpm nearby at different distances to measure the mw thats coming off the surface. i wouldnt be suprised if the actual scatter actually registers on the lpm.

That seems like a pretty cool idea but I'm not too sure it would pick anything up only because every time I do a LPM test I have a super bright flashlight aimed on the wall next to it and nothing registers on the meter and white light is still photons going everywhere, plus I think the scattered light from the laser doesn't have enough evergy to pick up on the meter. I could be wrong, but I don't know :thinking:

 

[paul1598419]

I don't know what you've been reading but it probably wasn't these three sites. These articles describe affects of blue light from lower intensity leds save the first article. I wonder what retinal damage is done by a significantly brighter 7W 445nm laser?
http://www.archlighting.com/technology/blue-light-hazard-and-leds-fact-or-fiction_o<br>
https://ehp.niehs.nih.gov/122-a81/

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4734149/

After reading all this voluminous material on the so called hazards of blue light, I found nothing to contradict what I said in my earlier post. Most of the worry is over circadian disruption while two considered the same study where albino mice were subjected to light levels abnormal the regular mice and noted retinal damage in these mice. The problems with this study were outline in detail in several places among your links. So, while I still believe that no one should subject themselves to abnormally bright light of any wavelength, I cannot find any evidence showing damage to normal retinas in human adults from blue light exposure, other than the obvious retinal damage in certain older individuals from outside light sources.

 

[RedCowboy]

If you are in your backyard pointing your multi watt blue laser at the ground and your friend walks into your front yard 100 feet away and sees something blue on the ground in front of you, your friend is not at risk in most cases unless you are trying to burn a front surface mirror.

This has to do with divergence and distance, so pointing into my backyard from a window 50 feet away I still wear my laser safety glasses until I scan a distant area with the beam to be sure nothing reflective has found it's way into the grass.

Now if you are standing in your backyard pointing your multi watt laser at the ground in front of yourself there is no instance where you should not be wearing laser safety glasses because of damage from the diffuse reflection, that is the scattered reflection, but at a distance of 100 feet the diffuse reflection off a known substance such as a plywood target is typically safe, now if it's a mirror you are aimig at 100 feet away 1st STOP THAT and YES in that case you must be wearing eye protection as does anyone in the area because of the specular reflection, luckily the horrible divergence of these diodes negates a lot of the risk as the distance grows, but anything you are burning near yourself requires laser safety glasses that attenuate the wavelength because the energy of the diffuse reflection is harmful at short distances, ALSO don't forget about that unknown chrome foil candy bar wrapper that may get blown into your beams path so always error on the side of safety.

EDIT ---Also let me add that it's the good divergence of 532nm lasers that pose a distraction hazard to aircraft even though they are far away, there are NOHD tables that laser show producers use to determine safe exposure, also duration of exposure, but as a rule of thumb anything that burns needs eye protection when you use it to burn and anything that produces a visible beam must be kept away from passers by who could be distracted by it.

Very important note, you can do damage to your eyes and not know it until much later, some is cumulative, I have even read that strong blue light exposure can bring on the onset of macular degeneration before natural aging would, in short you must protect not only your vision but the vision and distraction hazard posed to passers by, and don't think that because you got away with looking at something that it's safe, that is a very ignorant testing criteria as we still can't fix much of what we can easily break.

Stay safe, alarm no one and protect your eyes, those are good basic guidelines although I'm sure there are more.

 

[paul1598419]

If you are in your backyard pointing your multi watt blue laser at the ground and your friend walks into your front yard 100 feet away and sees something blue on the ground in front of you, your friend is not at risk in most cases unless you are trying to burn a front surface mirror.

This has to do with divergence and distance, so pointing into my backyard from a window 50 feet away I still wear my laser safety glasses until I scan a distant area with the beam to be sure nothing reflective has found it's way into the grass.

Now if you are standing in your backyard pointing your multi watt laser at the ground in front of yourself there is no instance where you should not be wearing laser safety glasses because of damage from the diffuse reflection, that is the scattered reflection, but at a distance of 100 feet the diffuse reflection off a known substance such as a plywood target is typically safe, now if it's a mirror you are aimig at 100 feet away 1st STOP THAT and YES in that case you must be wearing eye protection as does anyone in the area because of the specular reflection, luckily the horrible divergence of these diodes negates a lot of the risk as the distance grows, but anything you are burning near yourself requires laser safety glasses that attenuate the wavelength because the energy of the diffuse reflection is harmful at short distances, ALSO don't forget about that unknown chrome foil candy bar wrapper that may get blown into your beams path so always error on the side of safety.

This^^^^ is absolutely correct. One must always be aware of the possibility of reflected light from any laser, but especially higher power ones. The scattered light coming back from a nonreflective surface is like any other bright light source and diminishes as the reciprocal of the distance squared from it to your eyes. At larger distances this becomes less of a problem with lasers with high divergence angles as the chance of the reflection making it back to your eyes decreases with distance. However one should always use appropriate eye protection when using lasers over 5 mW in power in close proximity unless you are absolutely certain there is no chance of a stray reflection getting back to you.

 

[steve001]

After reading all this voluminous material on the so called hazards of blue light, I found nothing to contradict what I said in my earlier post. Most of the worry is over circadian disruption while two considered the same study where albino mice were subjected to light levels abnormal the regular mice and noted retinal damage in these mice. The problems with this study were outline in detail in several places among your links. So, while I still believe that no one should subject themselves to abnormally bright light of any wavelength, I cannot find any evidence showing damage to normal retinas in human adults from blue light exposure, other than the obvious retinal damage in certain older individuals from outside light sources.

Are you so certain you'd be willing to put the no photo reactive retinal damage conclusion to the test? Probably not I suspect.

 

[paul1598419]

What kind of test? It depends on whether it proves that just blue light is damaging to the retinas of healthy individuals or not. I can't imagine a test you could make that would prove that one way or the other because apparently some people have tried, (the albino mice), and came up empty.