405 nm LASER SAFETY

[mixedgas]

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

[Pangolin]

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" . 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

[Greeeen]

Hi,

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

[Laser Ben]

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.

[mixedgas]

[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

[mixedgas]

[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" . 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

[Laser Ben]

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.

[allthatwhichis]

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... Sounds like me before I joined...

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.

[mixedgas]

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... 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

[The_Doctor]

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.