405 nm LASER SAFETY

405 nm DIODE HAS SOME SIGNIFICANT LONG TERM SAFETY HAZARDS. WE NEED TO ADDRESS THIS!

YOU ALL LIKE YOUR CORNEAS , RIGHT??????????????????

I'm SURE YOU LIKE WORKING RETINAS! RIGHT??????????????????????

405 is borderline UVA or UV-A

Start HERE:

http://www.photobiology.info/AdvMods...ullen.asp.html

I'm working on the retinal side effects.

HERE is a start:

http://www.ncbi.nlm.nih.gov/pubmed/2...?dopt=Abstract

What I am reading so far is that higher end UVA, ie 390-420 is responsible for long term damage to color vision. I KNOW there are studies on daily exposure to 488 causing color vision degradation, so going shorter in wavelength is more energy per photon, so it will be WORSE. The one study suggests that a particular type of permanent damage starts with a threshold 50 times lower then the corresponding green laser threshold.

We all know a direct hit is bad, I'm however worried about LONG TERM exposure. LTE can start with just a few minutes a day.

I'M SHOUTING FOR A REASON FOLKS!


STEVE ROBERTS

Hi Steve,

I have pondered this myself.

There is a tendency lately to use 440 or 445nm Nichia blue laser diodes in projectors -- because it is simpler than using a DPSS blue and it also avoids the whole "jelly beaning" issue. BUT, although 440 or 445 could be called "simpler" or perhaps "better" from a modulation standpoint, and thus it is attractive, it is less visible than 457 or 473nm produced by DPSS lasers. Less visible means you need more of it for a given level of "human stimulation" :D. So as a result, you need even more of this light to produce a visual effect.

For graphics applications, I am not too worried about this. But for audience scanning I am a bit worried. Yes, you need more of this light to create the visual effect, and also there are photochemical effects that come into play with shorter wavelengths. So for myself, I have a bit of a concern.

However, really the only thing that we can do is go with the standards. If the laser safety standards rate these lasers as having the same hazard as a 632nm HeNe wavelength, then that's what we have got to use. I don't want to say I am smarter than the guys who wrote the standards...

My point is, Steve, you might be right. But until the laser safety standards themselves are changed, I guess we should just do what the standard says, and treat it as having the same level of hazard. Perhaps smart people can treat it with a greater hazard, but for "the world at large", I can't complain if people treat these lasers with the same hazard level as other lasers...

That's how I look at it anyway...

Bill

Hi,

Interesting thought.
I doubt if 405nM lasers existed when the exposure "standards" were written!


:confused:

I have talked to my dad about this a lot, he works with multiwatt 430nm LED sources every day. One thing that is very interesting that not many people have considered, is the problem with skin. At these wavelengths, there is a possibility for skin damage and getting the equivalent of sun burns on exposed areas. Whenever someone is working with LEDs in the lab at work, they have to wear a long sleeve shirt or lab coat and wear protective goggles. I

I don't think the safety aspect has been given enough recognition. These diodes are just like IR where they are hardly visible so people think they are safe, they are way more powerful then the might appear. I think companies need to step forth with 405nm goggles.

[QUOTE=Greeeen;73659]Hi,
bebin quote,

Interesting thought.
I doubt if 405nM lasers existed when the exposure "standards" were written!

end quote
Thank You, I think you see where I'm going with this.

The closest laser line is a lab curiosity, but has been used for research, and a expensive line to get, usually requires a large frame krypton ion laser, and its at 412 nm. It is very low gain and needs KRIII ion instead of KRII like the red lines. That means you need 440 power, and a hard driven tube to get it , hardly something that would worry the FDA et Al. The next closest blue gas laser is 442 of hecad.


Xenon sources are weak in this spectral area, metal halide sources in this area have only been out for maybe 15 years,and mercury-gallium and mercury-iron lamps, which are strong in this area have been in use in a very restricted market, reprographics and curing, where there is little or no direct exposure. The last time I opened a box for a mercury-iron lamp, it stressed that you were aware of the hazard by opening the wrapper.

Semiconductor sources of any power in this area are what, 5 years old, and only now penetrating the public access market.

So I am very worried about these lasers, now that I hear rumors of 500 mW sources from combining several diodes, being used for audience scanning.

I am further worried by a lack of research funding for the effects of blue led and violet diode sources, INCLUDING, the long term effects of having excess blue in yellow phosphor based "WHITE" led sources, the low cost ones are really leaking blue. I hope this is not another case of where the Doctors will have to see a trend in admitted cases before changes are made.

My point is new sources are on the market and I'm not seeing new safety studies.

Bounce that one off your Dad please Ben, if he cares to comment.

BE CAREFUL with the near violet lasers, please people, because their origional intent was to be in a sealed class I disk drive, not out in the open. Please, do not assume regulators are aware, funded, or even eager to consider the problem!


Steve

[QUOTE=Pangolin;73658]Hi Steve,

I have pondered this myself.

There is a tendency lately to use 440 or 445nm Nichia blue laser diodes in projectors -- because it is simpler than using a DPSS blue and it also avoids the whole "jelly beaning" issue. BUT, although 440 or 445 could be called "simpler" or perhaps "better" from a modulation standpoint, and thus it is attractive, it is less visible than 457 or 473nm produced by DPSS lasers. Less visible means you need more of it for a given level of "human stimulation" :D. So as a result, you need even more of this light to produce a visual effect.

END QUOTE:\

Bill,
My worry is not as much about the 445 nm diodes, as the 405 nm ones ripped out of DVD players. They are being offered on ebay for pointers. While 445 is somewhat actinic, it is much better studied then 405. There is a considerable spread in the research I have read of where exactly 405 gets adsorbed in the eye, between the cornea, aqueous humor, lens, and the retina. There is also a considerable spead in the wavelength of the 405 nm devices, some go down to 390, others range upwards to 415.

Steve

I know that there can be problems with excessive blue in LEDs, but it is not to the point where it is hazardous. Perhaps long term exposures to high levels of the overly blue light could be a problem, but not if used in flashlights etc... I will ask my dad what he thinks about it tonight.

Thank you for bringing this up Steve. I understand there are safety concerns and that the frequency is in an area that poses more hazards that our usual mix; I'd like to request some clarification of your point for some of us... less educated, that would like to incorporate these wavelength of laser in our projector.

Are you suggestion we do not install them at all?

Do as we will but be even more cautious in our safety measures hardware wise, and/or how and where we point our projectors? No more sitting in the balcony... ;)

If we do install them, be extra cautious on how we program their use into shows?

Try to get someone, FDA, ILDA... to perform more research on these wavelength lasers?

Or are you just warning us about the id10ts out there we already know about except they now have access to a laser that is more dangerous because of the wavelength? ;) We all know they are out there, they can now make a high power blu-ray pointer for cheaper than they can buy a low power green one. Or they can have someone make one... :rolleyes: Sounds like me before I joined... :o

Again I appreciate the warning and wisdom as usual, but as sometimes when you are posting about the internals of gas lasers, and playing with big ass power supplies... I have certain agreements with myself about voltage and avoiding them, I don't have to understand these posts. I feel this one is important and just want to be clear. ;) I like the violet pointer that someone made for me. :)

QUOTE:
Are you suggestion we do not install them at all

END QUOTE:

I'm saying not enough is known about their long term effects. I certainly would not use them for audience scanning , or any situation with prolonged day to day exposure. This is a wavelength known to cause sunburn and eye irritation. The 20 nanometer region either side of this wavelength is poorly studied.



Quote:
Do as we will but be even more cautious in our safety measures hardware wise, and/or how and where we point our projectors? No more sitting in the balcony... ;)

ENDQUOTE

You will NOT be scanning me in the Balcony with 405.


Quote:
If we do install them, be extra cautious on how we program their use into shows?
ENDQUOTE:

I would not use these as day to day programming lasers. I would be extra cautious, and I would not use them in arrays for sure. for a few tens minutes of graphics in a planatarium, ok sure. But what about waiters and clubgoers who attend the same club night after night for 3-4 hours? NO WAY!

Quote:

Try to get someone, FDA, ILDA... to perform more research on these wavelength lasers?

endquote:

FDA is probably not interested as right now they are low volume. Remember, FDA thinks they were in a class I device and are gonna be landfilled at end of life. If ILDA had money, they would be looking at other problems.


QUOTE:
Or are you just warning us about the id10ts out there we already know about except they now have access to a laser that is more dangerous because of the wavelength? ;) We all know they are out there, they can now make a high power blu-ray pointer for cheaper than they can buy a low power green one. Or they can have someone make one... :rolleyes: Sounds like me before I joined... :

END QUOTE:


A high power laser is a high power laser, at some point it gets dangerous, and the general public thinks of them as star wars death rays. Well , as one military text frequently points out, when it first goes off, a nuclear bomb is like a very large conventional explosive with a
few unique side effects. As time goes by, however those side effects get really nasty. I'm worried about cumulative exposure. I've met a few retired glassblowers with cumulative UV eye damage, they have snow white opaque corneas, even when they used the protective "didymium" glasses used to mask sodium yellow and uv flare from the torches and hot glass. They speculate it was the long term leakage of UV around the open sides glasses frames that got them. However most of the general public wouldn't tell you about scatter in their description of a IR laser powerful enough to destroy a target, they wouldn't know its there. Its not in the hollywood image of the laser "hit".

In the early 90s when I met those guys, ironically waiting on their tables at a fast food place, corneal transplants and replacements were a dream. Still , today, why RISK it?


I remember reading some place that you needed to be a full two meters from 300 mW of point source argon light on the wall for a full 8 hour day's exposure to be within the limit. The US legal limit for visible was something like 320 microwatts per square centimeter for 8 hours per day, and this is certainly a heck of lot more energetic then visible. I'm not going to recalculate that for tonight's post, but it sounds about right.

Since I no longer work for the Univ of Akron , I can't go access Scifinder Scholar and do a keyword search of the known OMNIVERSE of scientific publications and read what I'd need to know to answer this more accurately. It would cost 20-30$ a paper for me to get online access , ie about 10$ a page to read it. It would take accessing 5-10 papers to get a basic idea of where to go. I can't afford that. I could go bounce around the 4 free access university libraries ,within 100 miles of here (just paying megadollars for parking) but the odds of them having a decent text on this less then 5 years old are worse then playing the state lottery. They don't buy new physical texts either, their new stuff goes on raid arrays downstate and only the students can access them. Most of the books older then 15 years are in the ultra secure regional depository library, so that is out too.

Even the current standard exposure chart for time vs wavelength is pay to play now, I have to use a 5 year old copy.

SO: My conclusion is to avoid more then a few minutes a week of indirect 405 nm laser light and NO direct contact. I have to err on the side of conservatism. ie the medical rule of "DO NO HARM". Current statements by eye doctors say to get the newer sunglasses that block 400 as well as the older 360 nm stuff. On the flip side, I've read a few things today saying you need small amounts of UVA for dna error correction and skin cell regeneration. But there is a energy density difference between sunlight and a coherent laser spot.

A rock of depleted uranium in your driveway isn't a problem, putting it in your bed night after night would be.

Now go enjoy the sunlight, but wear sunscreen and sunglasses. Do get some solar near UV, or you wont make vitamin D and you'll get sick :-)

I hope I have answered your questions, but I have not answered mine.

Steve

I've had about 92 mW of 405 nm light shining on a white wall in my room for at least three months now, during a long term test. The only change in my vision is that due to hyperopia associated with aging. Granted, I don't stare at the spot at length, but it is easy to see at most times. I use the thing as a night light. The longer this test lasts, the less anxious I am, as no change in either the laser or my vision results. I just take care to avoid a direct hit.

While I think it is due for studies to be made on new devices made since last studies were done, I think it's easy to overestimate danger as well as to underestimate it. The only permanent damage I've had was from staring at a very bright cloud while underestimating the power of the sun that was not visible behind it, this caused a small 'floater' that does little to disrupt me. The worst medium term disruption to my vision I've ever experienced wasn't from a laser, it was from sunlight on wet sand at the Gower Peninsula in West Wales in June a few years ago. The shortwave dazzle from that is far worse than the specular reflection of a 100 mW 405 nm laser. We'd have to get close to a spot on the wall and stare into it for some time to do worse than that.

One other observation: I once tested a green laser on the palm of my hand. Whether the small brown spot there is related or not is hard to say, there's a very good chance it isn't, based on existing moles and knowledge that my grandparents also had an increase in such things with age. And I've tested the power of that 405 nm laser, as a crude guide when I didn't want to set up a meter, by shining it onto the skin between thumb and forefinger on the left or right hand. Duration and number of exposures has been greater by far than with that green laser, and despite carefully using the same place on my hands so it's easy to monitor for lesions over time, there are none. And the clarity and colour of my vision is as good as ever, only the focus is slowly declining. Night vision is still exceptional.

This might not satisfy many as a formal test, but it's a real study, done in the same spirit that the subject of my avatar has tested stuff. Sometimes it's the only way to know.

Annoying browser error, dupe post deleted.

[QUOTE=The_Doctor;73952]I've had about 92 mW of 405 nm light shining on a white wall in my room for at least three months now, during a long term test. The only change in my vision is that due to hyperopia associated with aging. Granted, I don't stare at the spot at length, but it is easy to see at most times. I use the thing as a night light. The longer this test lasts, the less anxious I am, as no change in either the laser or my vision results. I just take care to avoid a direct hit.


Ah, dude, what are U smokin?

I want real evidence, ie documented stuff.

Steve

Then you'll just have to pay for it like everyone else! We live in a world where the only EVIDENCE that counts costs at least £60 or so, in the form of written evidence from a trained professional who is a member of a recognised body. Sod the fact that these people ONLY get their evidence from studying actual things that other people do because they themselves by definition are NOT either a large, or impartial, sample. If you can't take real first hand evidence when it's handed to you for free, ok, but in that case you'll just have to buy it like everyone else does when they want 'authority' to hand it to them.

Put it another way: if I did what I did as part of a recognised clinical test I'd be paid a damn sight more than than a copy of that evidence would cost you. What exactly is it about freely given info from a single person that is so suspect? If you really want to know, test it yourself. Sounds to me like you might not trust anything less.

Put it another way: if I did what I did as part of a recognised clinical test I'd be paid a damn sight more than than a copy of that evidence would cost you. What exactly is it about freely given info from a single person that is so suspect? If you really want to know, test it yourself. Sounds to me like you might not trust anything less.[/QUOTE]

Sounds like I would like: scientific method in a recognized journal, not conjecture because you exposed your (insert body part here) for n mW/cm^2 every day. Just our luck your the one bloke with a different chromosome set or a slightly different protein, as so often happens these days, and thus more resistant from damage.

Anecdotal evidece, unless you have snow white corneas and have never been in the sun since you were born, doesn't cut it!

:-)

Steve

How would the UV radiation from a 405nm laser compare to that of 400W UV cannons (mercury vapour lamp) used in nightclubs? I presume the cannon would be nearer to 390nm, but people are often exposed to these for 8 hours at a time.

good point.. uv cannons and general blacklight tubes etc....

Steve, it's a funny scientific inquiry that rejects one of the first bits of evidence that comes its way. It all starts with anecdotal evidence, how else does anyone get an inkling of what might or might not be going on?

What would you have people do? Get normalised assessments of biological and optical function, then clamp their heads in vices and use some kind of optical speculum to wedge their eyelids open while you timed their exposure to a precisely quantifed source of emission?

Most people wouldn't accept a report of such an experiment if it came to them in triplicate because it's not realistic, never mind the moral grounds for objection.

You might not like what you see in my statement, but it's a fact. If I'd claimed a special case you'd be berating me citing facts of how humans really aren't all that different.

Just accept that if I can spend months in a modest sized room in fairly close proximity to scattered 405 nm light from a near-100 mW source, without any degradation of sight attributable to it, then I think bar staff in a night club can be assumed to be safe. Right now it's not like they can get 405 nm lasers any stronger than mine, is it? For an example of practical, real world exposure, mine is good. As time goes by there will likely be more similar. Real scientific enquiry might not even begin till such accounts indicate a need for it. And as QUAZAR and aijii said, there are plenty of other sources used in such environments more likely to cause similar effects on vision. (mainly cataracts and colour distortion).

You can claim that my lack of accredited scientific establishment counts against me if you like, but my claim that dismissing personal direct evidence is bad science will carry more weight. Sure, you can ask others, get more info, but dismissing anything is just bad science. Scepticism is often a fine word that disguises a simple inverse of credulity.



EDIT: And on a scientific balance of probablility, how often do you find that I talk out of my ass? >:) Not often, I hope.

the 365 nm light from the blacklight cannons is even more bioenergetic by a factor of 3 or 4 , and there is a lot more of it per evening. After having 354 nm uv induced conjunctivitious once, from using a poorly shielded eprom programmer when I was in college (had to do 500 eproms a day) NO way I'd blast my audience with that for more then a few minutes at a time. If the wrong type of lamp is used, you get 253.7, much, much more energetic.

conjunctivitious is a sunburned cornea and eye tissue, and it hurts like someone poured alcohol in your eyes for about 20 hours straight.

The only thing remotely making this tolerable is inverse square law.

IN the US, FDA rules exist for mercury vapor UV light exposure, and that club's 400 watts would be considered a very dodgy use.

Somewhere I read about a circus owner installing used, bare, lamps from tanning beds as black light glow lamps on childrens rides , oy vey.....

A few minutes wont hurt, but day after day exposure for the staff and regulars is bad...

When I was in college, I worked with a teen princess who would tan herself light brown week after week after week. With red skin from erythermia, you could tell when it was tanning night, she'd have real pain the next day, as this progressed, she'd have anemia and joint pain. MY bet is she is no longer with us, 10 years later. But she had to have that whole body tan for that short nearly topless, bare midriff sweater and cheerleader skirt, and she was too shallow to know better. She had to be cool. I did my best to warn her, but it went in one ear and out the other. She knew she was in pain, but willing to pay the price for being mega "A" list.

Best way to put it was imagine looking at a evenly deep fried girl, almost beet red once every two weeks.

Remember, those of us who work with technology have the duty to protect those who trust us.

UV exposure is cumulative, our creator gave us just enough resistance for life someplace mellow as far UV goes, human generated UV, or high solar altitude UV just wasn't part of the plan

UV is still limited to far less then the visible limit of 320 uW per cm^2 per 8 hour day in the US. I'll find the limit number.

So that could give you a idea of where to start the math.

Steve

[QUOTE=The_Doctor;74031]Steve, it's a funny scientific inquiry that rejects one of the first bits of evidence that comes its way. It all starts with anecdotal evidence, how else does anyone get an inkling of what might or might not be going on?


Do some reading, you'll find that it can take a decade for symptoms to creep in.
When they do, its fast and nasty and spreads to internal organs quickly.

Argument again rejected.

Steve

Quote:

---

Originally Posted by mixedgas

the 365 nm light from the blacklight cannons is even more bioenergetic by a factor of 3 or 4 , and there is a lot more of it per evening. After having 354 nm uv induced conjunctivitious once, from using a poorly shielded eprom programmer when I was in college (had to do 500 eproms a day) NO way I'd blast my audience with that for more then a few minutes at a time.

IN the US, FDA rules exist for mercury vapor UV light exposure, and that would be considered a very dodgy use.


Steve

---

Ahh, I was a bit high on my guess for the wavelength. I dont know abous Aus or the rest of Europe, but there are no restrictions for using UV in a night club environment. Many clubs now open all night and having 4 x 400W cannons installed is quite commonplace.

Interestingly though, there are regulations for tanning salons.

Although not arguing your point about UV radiation from 405nm laser emission, it would appear the the UV cannon is inherently more dangerous, but less restricted in its use and application.

405 nm has long been in the standard visible range of 400 to 700 nm, and is not generally considered a hazard as sources well beyond 400 nm are. If this needs serious revision, don't blame me for accepting it, I didn't establish this accepted status. As Bill said, until such time as this is viably disproved as good status, we should go with it.

Sure, inverse square law might be the main thing we rely on to protect us, but has it ever been otherwise? That helps even with new sources. If we know a visible-range source IS 100 mW and treat it with the same cautious avoidance of direct exposure or staring at bright diffuse sources as with obviously bright ones, then we do most of what needs to be done.

What reading? You need to be more specific. I was always told that moderate long-wave UV exposure either had little or no effect on the body, or was localised to surface effects, in the skin or corneas. No mention of internal organ failure. You need to cite the sources to be explored for that one. People have lived with equatorial sunlight for millenia, and it's known to cause damage to skin, even just accelerated aging of that skin. And cataracts. I never heard anyone say it caused internal organ failure, even after a lifetime.

EDIT: I know that a melanoma can go agly and migrate cells to damage other organs, but this is an extreme case, and plenty of obvious things go wrong before that happens. Such damage is well beyond 'creeping up' on its victim.. Probably results from traumatic exposure rather than incremental, too.

Quote:

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Originally Posted by QUAZAR

How would the UV radiation from a 405nm laser compare to that of 400W UV cannons (mercury vapour lamp) used in nightclubs? I presume the cannon would be nearer to 390nm, but people are often exposed to these for 8 hours at a time.

---

And also ar lasers, isn't 351nm one of the strongest lines and a fair bit of power produced <407nm?

Quote:

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Originally Posted by p1t8ull

And also ar lasers, isn't 351nm one of the strongest lines and a fair bit of power produced <407nm?

---

If exposed directly to the arc tube glow at close range that might be troublesome but I think the energy in that wavelength is reduced in the beam by selective use of mirror coatings. Very little of anything but the designed-for wavelength will get into the beam, as one strong resonance robs energy from other potential ones. For more on that I will defer to Steve, this is definitely his territory.

I have had some thoughts regarding the safety of these lasers as well. While I initially regarded them as equally "safe" as other visible wavelength lasers I'm not so sure anymore.

While it is not by definition UV light, it is rather energetic and still sufficient to cause photochemically induced damage in tissue (and DNA) via free radical mechanisms. Consider that the irradiance of a 100 mW laser focused to 1 mm² (100 kW/m²) is over 2000 times higher than what you receive from the sun in the form of UV-A radiation (45 W/m²). At such a high irradiance the natural defense against free radicals might be severely overpowered, causing far more damage than the sun would.

As for eye safety, which is probably our primary concern, it is my belief that there's no reason to treat it any differently than a laser on the other extreme of the visible spectrum. It is easy to underestimate the radiant power of these lasers because the eye responds poorly to them. If you're considering audience scanning with them (not recommended) you really need to look at the radiant power, not perceived brightness. If you don't understand these terms you shouldn't be doing any audience scanning whatsoever.

We are exposed to a lot of UV light from the sun on a daily basis. The solar spectrum is surprisingly flat in the 400-700 nm region. The irradiance at say 395-415 nm is only 30% lower than at 520-540 nm. Sure, high exposure to UV light from the sun does cause eye problems, but the sun is a lot stronger than a laser or blacklight (they are very inefficient).

If you're looking for safety goggles for 405 nm, think sunglasses. They're supposed to have 0% transmittance at wavelengths < 400 nm. This means very little transmission at 405 nm, because the UV-absorbers have rather broad peaks. Just make sure to test them first as they might not be as good as they should be.

tocket, I agree with all points there, but this one needs a bit of exploration:

Quote:

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Originally Posted by tocket

While it is not by definition UV light, it is rather energetic and still sufficient to cause photochemically induced damage in tissue (and DNA) via free radical mechanisms. Consider that the irradiance of a 100 mW laser focused to 1 mm² (100 kW/m²) is over 2000 times higher than what you receive from the sun in the form of UV-A radiation (45 W/m²). At such a high irradiance the natural defense against free radicals might be severely overpowered, causing far more damage than the sun would.

---

While that's also true, I can assure you that more than a very few tens of seconds of exposure to 1mm square of 100 mW hurts. >:) Avoidance is immediately demanded strongly by several body mechanisms after periods well under 2000 times shorter than we can tolerate hard sunshine. Also, it's very localised. I suspect that if such exposure was nonlocalised enough for free radicals to overwhelm that region of the body, then traumatic damage of greater significance would result. Like a serious burn.

I think that the most likely result of a small point exposure is an irreversible generation of melanin, a pigmented spot. Several causes for these exist, most of no consequence. Just watching for odd activity of such, as with any mole, might be enough to prevent cancer or other nastiness developing unchecked.

melonoma migrates inside from skin via the lymph system faster then you can say "black death"

The 351 line of argon is strong, but its ARIII+ instead of ARII+, so tubes get driven 2-3 times harder to get the 351/365 nm lines. At 40 A, the laser I used to work on did 9+ watts all lines visible. At 55 amps, it did 350 mW all lines UV or about 100 mW single line , single frequency, but one little organic film on the brewsters, or any dust at all in the cavity and its not lasing. The UV would slowly cook the teflon in the brewster stem covers and deposit it on the windows. It broke down skin cells and turned them into window films as well. Had to wear a smock, mask, and cotton gloves to work on it.

Even a fraction of a mm of polycarbonate was all you needed for safety glasses for 351, but we would still test all the glasses to make sure.

Shortly after I left that lab a chemical engineering grad student who wouldn't listen decided that running the tube at J=1100 A/cm^2 vs 700 A/Cm^2 (J = current density from the gas laser equation)current density was gonna get her graduated faster by speeding her sample exposure times, She cooked the tube in a week. It still would do 5 watts of all lines vis, but a inside window film prevented UV. I got the call to check it out, and she was dum enough to write the current levels in the log. She'd go to class or lunch and leave it at 65 amps. She didn't care, its not her money. I hope she enjoyed delaying her graduation for a year. UV argon runs that energetic inside.

But that beam was scary, I had the doors interlocked, outside and inside warning lights, and the orange shielding plastic and phosphors around the beam paths, if it drifted off a pinhole, you got a glow, and a bright one. Failure to wear goggles in that lab ment two weeks of not doing your experiment and a day long laser retraining session with me. You only that option once.

BTW the lower laser level is a 170 nM excimer like photon radiated before going back to ground state.
It doesn't make it out the windows, thank God.

Steve

Quote:

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Originally Posted by The_Doctor

While that's also true, I can assure you that more than a very few tens of seconds of exposure to 1mm square of 100 mW hurts. >:)

---

Oh, I know. It stops hurting once you get deep enough though, but that takes a few minutes. :p

No, seriously, 100 mW/mm² doesn't hurt instantaneously. It takes a few seconds. You need to focus it further to get instant pain and smoke.

Regarding laser vs sun, I suspect 1 s of laser exposure is worse than 2000 s of sun exposure (with UV-B sunblock). The reason being antioxidant depletion; their concentrations are fairly low and they're transported relatively slowly. Once the antioxidants have been depleted, radicals will be free to cause more damage before they are finally eliminated (radicals are not consumed in a reaction, so a single radical can potentially do damage to thousands of positions in your DNA). In the case of sun exposure the antioxidants can easily be transported quickly enough to maintain a sufficient concentration to efficiently scavenge radicals.

Of course this is just my hypothesis, I don't have any data to back it up. It might be completely wrong.

Oh, you don't get a sunburn from 405 nm by the way. You need UV-B to activate that mechanism. You will indeed darken existing melanin though, giving you something of a tan. :)

[QUOTE=The_Doctor;74041]If exposed directly to the arc tube glow at close range that might be troublesome but I think the energy in that wavelength is reduced in the beam by selective use of mirror coatings.

UV does leak out of the OC. Its not lasing, but there is one member of PL who will tell you that years of being around the UV from laser cathodes and yag pump lamps has earned him double cataract replacement surgery.

Steve

Look guys, my worry is that enforcement of basic technical safety principles is going to "Hell in a Handbasket" very fast. Somebody in a low production cost country we all know and love , does something like combine 20 units of 405s in a Arctos style array and we have a exposure problem, a second Moscow incident waiting to happen.

Since they cant seem to make 1 watt plus at the prices they make 100 mW for, we seem to have reached a temporary safety plateau. I have frequent nightmares about this.

We are having this discussion so that our peers on this board are more aware of a issue that can rapidly scale at 4 pieces of 200 mW 405 in a projector. That's why I have been goading the doctor..........


The jury is still out on long term or corneal exposure.

Steve
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I started working at Spectra-Physics when I was 22 years old. One of my jobs for years was final test alignment on argon & krypton lasers. I spent 8 hours a day (ore more) hunched over open cover cathodes running while aligning lasers. I left in 1984 so that was 6 years of "average" exposure of the intense uv from cathodes. 12 years later in 1996 about one week after my 40th birthday, I went blind in my right eye from a very quickly developing cataract. I had a lens implant surgery and total vision was restored in that eye perfectly. Two years later my left eye developed a cataract very quickly and I also had a lens implant in that eye restoring my vision perfectly. I am not saying that UV exposure was the cause, but I dont have enough data to say it wasnt.

Understand that "WE ARE" the lab rats for cumlitave laser exposure.

I am now 52 years old and waiting to see if any ill effects come my way because while also working there we were working with laser dyes and DMSO at the same time. We use to wear the dye on our hands as a badge of honor to show how hard we were working. The more different colored laser dyes you had on your white lab coat was also considered "experience" I also used UV lasers in the 3.5 watt watt range to pump laser dyes...double wammy!:(

Stay tuned for updates....

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Originally Posted by tocket

Oh, you don't get a sunburn from 405 nm by the way. You need UV-B to activate that mechanism. You will indeed darken existing melanin though, giving you something of a tan. :)

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I meant a heat burn in this case.. Also, I agree, existing melanin seems more likely, I got the impression that any small moles that were new might likely be enhanced by this, not created, if affected by it at all. (There is controversy about whether UVA also causes sunburn in tanning lamps but I agree that UVB is the one to do it).

I'll read up on free radicals. I've heard of them, but not looked deeply at them. I normally eat a diet high in antioxidants though, I chose sources that I know are good, usually fresh meat, or tinned fish, and lots of fresh fruit.

Steve, I agree that the Arctos thing with a lots of 405 nm diodes might be enough to tip the balance obviously, even scattered light will be strong at several feet then. Until then it might be worth looking at UV LED's as used in arrays to replace lightbox fittings for PCB exposure and such. Those are common enough that there might be some correlation between reported medical problems and use of those. I wouldn't want to have to find that scattered evidence and collect it though. All I know is that there is enough similarity in output to consider looking there, and there are lots more of them already.


Pat(?), I bet you're right, that it is related. People who work in labs don't usually get cataracts like people working all day in bright sun do. Not so far as I know, anyway..

Hmm, this has been a great thread about the 405 lasers. I know that you can do something rather stupid now and end up paying for it 20 years later. It gives me enough concern to dismantle the 405nm pointer I have until it is proven beyond the shadow of a doubt that there is no harm. Steve, thanks for bringing this up, it has been very informative.

Putting aside the total morons out there with lasers, I dont think the amount of exposure a average hobbyist, to a 405nm laser, would cause such serious damage. sure, you should be using goggles, to protect your eye's, but with most people its *click on* light the match *click off*

If they start pointing it on their skin and in their eye's, that is harmful with any laser, in which case isnt really a problem with the wavelength, but with the user. If you shine a laser on your skin, and it starts to hurt, most _regular_ people would take it away, or not even do it to begin with.

Shining it in your eye is just plain stupidity.

While I do agree with what has been said in this thread, I dont think the AVERAGE hobbyist gets enough exposure time to be any different from other lasers.

I know there are alot more people more experienced in the field than me, here , just my opinion ;)

You're probably right, and I hope you're right, but to me it's enough of a concern to discontinue using mine for now.

I accidentaly got a 405nm beam of around 100mW on my hand while adjusting the dichro on my projector. It left a tanned streak when I moved my hand and it was visible for a couple of weeks. I had the hand in the way for maybe 30 seconds to a minute. I't didn't hurt so I didn't notice it until the day after.
I won't do it again!

Would even diffuse viewing of a 405nm dot even if done fairly often surpass the exposure of a seasoned construction worker from the sun?

Quote:

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Originally Posted by Xytrell

Would even diffuse viewing of a 405nm dot even if done fairly often surpass the exposure of a seasoned construction worker from the sun?

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probably not, in the long term. But 405 is so poorly researched its not even funny.

Steve

Just found this document on 400nm laser radiation. Might be usefull to you.

I'm in vision research too - specifically age-related macular degeneration - are you at CWRU, Steve? I will pull a few papers and post references to where the 457 or 488 line of an argon laser administered to animals with high cholesterol in diffuse, non phototoxic (ie not hole burning) doses caused rapid oxidative damage and degeneration of the macula. This was done not to assess the danger of 488nm light but to quickly model in a few weeks a process that takes a lifetime in humans.

Blue and UV light causes oxidative damage to retinas. I think the closest you'll get to evidence is if somebody finds that using a 405nm diode laser in their experiments works 10 times better than a 488nm argon. BTW, smoking is the number one risk factor associated with macular degeneration and vision damage, so if you're worried about your retinas stop smoking first.

Good thread. I'm glad I gave my 405nm to Evil Adam. He can go ahead and deal with the possible macular degeneration instead of me! :rolleyes:

I did notice while I had it, something in the back of my head was putting up red flags when I was hit by glare from walls when shooting it in the dark.

It was sort of scary thinking about how much power it was actually putting out compared to how much light I was seeing with my eyes.


Another 'thank you' for highlighting this issue Steve.

-Jonathan

Ah here we go - a solution for everyone's concerns - just make sure you blast yourself with equal amounts red or yellow and you should be fine.

"In 14 experimental Cavia Coba'ya eyes were irradiated with UV-B light, lambda 312 nm, 25 J/cm2 in 15 minute exposure. Including the transmission of light through optical media: cornea, lens, humor aqueous and vitreous body, and pupil surface of 7 mm2, we can calculate that in these conditions retina can be really irradiated with 10 J/cm2. The half number of Cavia Coba'ya was simultaneously irradiated with visible light, lambda of 550-600 nm (1000 Lx). Control group was 5 Cavia Coba'ya. Two months after irradiation, eyes were enucleated and fixed in 4% formaldehyde. Histopathological findings showed alterations of all retinal layers: loss of ganglion cells, axons, reduction of photoreceptors, vacuolar degeneration and hyperplasia of retinal pigment epithelium. In the second group of irradiance, the eyes with visible light lambda 550-600 nm, all retinal alterations were in 50% decreased."

PMID: 17469745 [PubMed - indexed for MEDLINE]

until I got downsized I was Institute of Polymer Science, University of Akron, about 40 minutes south of CWRU.

Steve

I had early cataracts start in both eyes before age 40 -- one ripened enough to get a plastic replacement, the last year before they started adding ultraviolet protection to the plastic (the other eye never got bad enough for the surgery). I see more blue with the operated eye compared to the natural (aging, yellow) lens -- and can see into the ultraviolet with the eye with the plastic lens -- can see the mercury spectral lines, can walk around at night with a UV flashlight using that eye (the normal eye barely sees a faint purple glow, the operated eye sees it as moonlight level purple). (And no, I don't do that; I wear UV blocking safety glasses in ordinary daylight, for that matter. Out of curiosity I got a claimed less-than-5mw violet pointer recently. I've used it for just one single blip pointed at a wall 50 feet away. The normal (aging yellow lens) eye saw a faint violet dot The eye with the UV-transmitting plastic lens saw a bright white dot surrounded by a violet flare. It's scary how much output these things have just past the edge of what's perceptible through normal aging eyes. A child's lens hasn't started to yellow with age -- really cautionary.

I found the "Moscow Incident" described: http://www.laserist.org/2008-07_Russian-incident.htm

The prediction above is fulfilled:
_________
quote:
This guy built a 40 watt laser rifle.
“My Homemade 40W LASER SHOTGUN!!!!!”
https://www.youtube.com/watch?v=iVrJ...ature=youtu.be