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FrozenGate by Avery

Playing with a 1.5w Blue laser and my eye hurts

I'm sorry but I'll have to be blunt about this. I'm just tired of how many people around here make 100mW lasers sound like they're optical bazookas that can insta-blind you from 100km away if you look at the friggin dot for 1ms.

@Livinloud: You claim OP's friends are talking bullshit but you didn't provide any scientific calculations to prove your point that looking at the diffuse reflection at that distance. Please do so. If you don't I'll provide the calculations (and their sources) to prove that you are overstating the danger by a *very* long shot.

@Spooky: No, it's not exactly the same. Not even xoul got completely blind and he got a *direct hit* by a 1W laser. A 7kW laser would probably pop your eyes like popcorn.

@OP: you shouldn't have looked at it from 5ft without goggles. Is there any chance it would damage your eyes if the surface was completely matte? No. Are you *sure* it's completely matte? No, you aren't. And that's exactly the point of using goggles, it's hard to know for sure what the optical properties of the surfaces are. And you can always make a mistake and hit something else or pass your hand in front of it.

@Everyone: I'm not advocating indoors use of lasers without protection. I'm just tired of the amount of safety misinformation being spread on these forums. Safety must be pursued, but based on facts, not fear, uncertainty and doubt.

Sorry about the rant.
 





@Atomicrox, go ahead and provide calculations, nswg. IMO anything over 5mW needs safety glasses. How many eyes do you have? If you know where to get a spare set then please let me know. Personally I only have the two in my head and the risk of reflection back into my eyes is not worth it. Call me crazy but i respect the dangers of lasers and the safety precautions that are needed. I cant control what others do but I can inform them of the dangers that come with using lasers.......if you want to call what i call safety, "over-safe" then go for it, like i said above, nswg.

Stay safe everyone :D

EDIT: Just an FYI, it doesnt matter if i meter my 300mW 650nm at 4 in or 20 feet, it still comes out at the same power readings. I ll meter it at 40 feet but im almost positive it will still come out at 300mW. Distance doesn't matter as long as you have a steadily aimed laser.
 
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Atomix,

There are too many unknowns with any laser (read: person) to base safety on calculations.A good percentage of people who read this but don't post or aren't registered will likely have fallen in here from a search on google etc, it's human nature to think the best in any given circumstance so when little Jonny who just purchased his 300mW pointer with the help of his mom (who just wanted him to shut up for the day) starts waving it round thinking he's Luke Skywalker and ends up hurting himself, a passing chopper or one of his friends you can be pretty sure "Mom" isn't going to want to take responsibility and will look for somebody to blame.

Guess who that's going to be

I'd rather have little Jonny a bit more scared than he should be so he starts out with a respectful attitude towards lasers before his actions end up getting all of us penalised for his ignorance.

Some time ago I was at a meeting involving a number of representatives from the firearms community, the FCC and the anti gun community. A lady there had lost her son in an accident when a friend has shot him with an air rifle, he was 9 years old.
A terrible thing to happen (and as a parent, I can't imagine a worse horror) but I sat through the meeting listening to this unfortunate lady blame this terrible gun for the death of her child and almost demand that the political representatives there made representations to ensure this kind of event never happened again.

As you can imagine I wasn't Mr Popular when I pointed out that the lady had committed a criminal offence that would usually attracts a 5 year prison term by giving her son the gun in the first place and that without her illegal act her child would most likely still be alive.

Not a nice thing to say, not a popular thing to say BUT absolutely accurate. All she wanted to do was absolve herself of responsibility by blaming an inanimate object for her own negligence in some part to assuage her own guilt.

I'd bet my last dime on the fact had she been better informed or even a little scared then her lad would never have been given the gun in the first place.
I'd rather have people like that a little scared by over stating the safety side than I would have them blame laser users / forums / lasers for their own mistakes and demand that we all get unjustified restrictions.

Complacency in general breeds contempt, once attitudes to safety become lax we all face the outcomes of such behaviour.If the safety bar is set at X level based on the physics of lasers, you can be sure there will be people who try to work above that as "it's only a little bit more" and will "probably be safe".

best wishes

Dave
 
The maximum permissible exposure (MPE) is the highest power or energy density (in W/cm2 or J/cm2) of a light source that is considered safe, i.e. that has a negligible probability for creating damage. It is usually about 10% of the dose that has a 50% chance of creating damage under worst-case conditions. The MPE is measured at the cornea of the human eye or at the skin, for a given wavelength and exposure time.
Click to expand...

According to this definition it's *very* safe to look at a laser below the MPE. It also includes any cumulative effects of high-frequency radiation.

Here's an MPE graph which reads 1mW/cm^2 for visible lasers for a *very* long exposure time.

And here's a paper with the laser safety formulas.

@Livinloud: Indeed a 300mW 650nm at 4 in or 20 feet will meter the same. That's because you're measuring the beam power and beam cross-sectional grows slowly because of the low divergence.

Having determined the MPE for a specific laser operating in a specific mode, you can now define a Nominal Hazard Zone (NHZ). The NHZ relates to the space within which the level of direct, reflected, or scattered radiation during normal operation exceeds the appropriate MPE. Exposure levels beyond the NHZ are below the appropriate MPE level, thus no control measures are needed outside the NHZ.
Click to expand...

Your 300mW laser, assuming 1mrad divergence and 1mm beam diameter (actual lasers would probably be around 5mm diameter and 2mrad, but let's exagerate for the sake of the discussion) will meter at 1mW/cm^2 (under 2mW on an Ophir head) from a distance of 195m (calculated NHZ). At this distance it should be safe to stare at the beam.

For 3W the NHZ would be 617m (in real life it'd be much lower because of the poor divergence of 9mm diodes).

And that's for a direct hit. If you want to measure the danger of a diffuse reflection you have to point the laser at a matte surface and meter the light reflected back, not the beam itself. This will of course be very hard to do because the powers involved are very low.

If we apply the diffuse divergence formula (assuming the worst conditions - that you're looking at a straight angle and the surface reflects 100% of the light) we get that the MPE will only be exceeded for the 300mW laser at 10cm. For OP's 1.5W laser we get 22cm and for a 5W laser about 40cm. As you can see there's no way looking at the dot of a 1.5W *on a matte surface* will do damage at 5 feet. The real danger here is if the surface isn't completely matte or if the laser hits something else. And that's why we should indeed use goggles for high power lasers indoors, specially for burning (which will make many objects reflect better).


@Spooky: I understand that concern and in general I'd agree... I usually overstate the dangers of lasers to non-laser people when I show them exactly because of this. But IMHO this forum, as a gathering place for enthusiasts, should strive to provide accurate information and unfortunately that's not what usually happens with laser safety.
 
Atomicrox said:
But IMHO this forum, as a gathering place for enthusiasts, should strive to provide accurate information and unfortunately that's not what usually happens with laser safety.
Click to expand...

Have you seen the number of "noobs" joining and viewing this place lately. I can agree with some of the things you say seeing as how i am an educated laser enthusiast HOWEVER, i agree with the above post on over stating lasers and the danger. i always recommend safety glasses to every member looking for a laser over 5mW. you got to remember, most people posting the "looking for ------ laser" are all new members or uneducated ones. the educated or regulars know what is good and junk. also keep in mind, if you use all these formulas and scientific lingo, people may come across your thread via google search. if they dont understand it, they will most likely skip over it or ignore it. being blunt and saying anything over 5mW needs glasses helps to protect our hobby. if people are "afraid" of lasers then there is less of a chance they will shine them at a car, person or air craft, thus keeping the unneeded strict regulations away from us.
 
Fair enough, you guys have a point. I guess I was being naive to assume most people that are attracted to lasers are nerds that like to get as much information as possible about their hobbies... I'll avoid arguing about this in the future for the sake of random googlers :P
 
Atomicrox said:
Fair enough, you guys have a point. I guess I was being naive to assume most people that are attracted to lasers are nerds that like to get as much information as possible about their hobbies... I'll avoid arguing about this in the future for the sake of random googlers :P
Click to expand...

saw nothing wrong with it either, i agree with you from what i remember but not everyone absorbs or cares to absorb information like we do :tinfoil:

Better to be safe or over protective especially with a hobby that we all love, than have a few uneducated morons ruin all our fun :beer:
 
Livinloud said:
1.5W is 300, let me say that again THREE HUNDRED, times more than the human eye can safely take. get some safety glasses now or please dont use your laser until you have them. it doesnt matter if the surface is matte or not. a matte surface will still reflect more than enough light to permanently damage your eye
Click to expand...
You know you have a bright mind but you are kinda paranoid about lasers. The dude said that he was playing with a 1.5w blue not pointing it directly onto his eye and I agree with you that looking at the spot of a 1.5w Is alarming but it's not 300x over the safety limit of 5mw because I don't think that he was shining it in the world's first 100% light reflecting surface anyways I agree that it is dangerous to stare at the dot of a 1.5w blue but not 300x over the safety limit dangerous cheers.
-John
 
Eh, not referring to these particular posts, but I think we have a part time former member who although busy over on another chat board most of the time, occasionally enjoys coming over here and posting this kind of thing.

Guaranteed reaction from him is if you resist something, he will persist. He's what you call a pest.
 
Yeah... I thought the same thing when I noticed the
spike in the necroposting but only by new members.
A dead giveaway...:cautious:

Jerry
 
This new forum has a list of threads that is posted and many are quite old- ATM there are 14 'links' mostly to LPF but some to advertizers.
I see no way will this necro posting will stop.
ATM there are 14 'links' somewhere on THIS page-- the source is fine print the title is NOT.
It would be very nice if Admin would add a notation that these links are not all new.
The DATES need to be checked before anyone posts.

NOT just the date of the last post--the OP date is were you start THEN see dates of the last 2 or 3 posts . THEN decide if another post is REALLY needed. THEN make or not make a new post--IF unsure PM any Vet ands get another opinion.
IIRC I saw a post--"Did your laser arrive?"--
to a thread on a "where is my laser?' thread--- that was 11 years old.. I would hope it had arrived AND why do you care? anyway?
 
Maybe this new forum software will block posting to old threads, if beyond a certain cut-off date?

Edit: Or, perhaps, limit posting to an old thread to members who have a certain amount of posts here first? Maybe that will keep the blue bird away.
 
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