200 mw green laser - safe?

Appropriate warning sign:

WARNING - LASER - DO NOT LOOK INTO BEAM WITH REMAINING EYE

Anything over around 5mw can be a problem, even if not tightly collimated or focused.

Please be careful!

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Reply to
artie
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Ask at alt.lasers and Mr. Goldwasser or Mr. Carlen will probably insist you get goggles. I googled, but I can't get a link to the gov. specs, and I'm not going to hunt it down fer you, unless you pay (=).

Use goggles, or un-collimate the damn beam!

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Reply to
Scott Stephens

I have the opportunity to purchase a green laser with an output power of

150 - 200 milliwatts. How safe are lasers at this power level? Do I need to get goggles to avoid burning out my retinas at this level, or are accidental flashes still harmless?
Reply to
Greysky

Can I ask who your source is? I might be interested in one also.

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Reply to
Mark Jones

Get goggles.

10mW is borderline for eye damage before blink reflex closes the eye. 200mW is seriously dangerous if you get a look at it.
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Reply to
Dirk Bruere at Neopax

Such a laser is a menace to humanity and will definitely blow a hole clear through your retina.

You don't sound very experienced with these sorts of things. It might be wise to experiment with a lower power laser for some time before tinkering with something like this. You need to get a feel for how laser light scatters off things, and reflects all over the place. Then you can improve your chances of avoiding hazardous eye exposure.

To be honest, sometimes I am a bit too cavalier about lasers, which is a consequence of handling them too much. To give you a clue about the danger potential of that laser, I'll tell you a story.

A few months ago I got a simple 5mW green laser pointer (1/40 of the power of the laser you are describing). Playing around with it haphazardously, I somehow managed to get zapped straight in the eye with it for a fraction of a second.

I have done this MANY times with

Reply to
Chris Carlen

power of

need to

accidental

might

Then

(...)

Interesting post. I've got a similar story.

Well, once the green lasers came down in price, I had to have one of them. I ordered a mod'ed laser pointer guaranteed to be 5 mW (z-bolt.com - mod1). I already had an old (used) He-Ne laser (~1 mW), and a couple of red laser pointers (all < 5 mW). So I was already used to the behaviour of laser light - how it relfects and interacts with most surfaces. I wasn't disappointed with the greenie. I couldn't believe how bright it was. The spot hurt my eyes to look at when I projected it on the wall a couple of yards away. The laser would light up a dark room if I projected the spot on the ceiling.

Well, I was playing around with the laser one night, standing between two mirrors and bouncing the beam betweem them. I got careless and took a direct hit in my right eye. Oof. Left quite an after image, but I didn't think much of it at the time. My vision seemed fine later. In the past I'd often caught direct reflections from my red lasers. Never seemed to do any permanent damage. HOWEVER, a couple of weeks later I started noticing this little black spot, near the center of my vision. In my right eye, near where the laser had hit. At first I noticed it when I first woke up. Usually I'd only notice it when I'd blink, or when I would quickly change what I was looking at. It would never appear all the time (thank god), but I'd occasionally catch glimpses of it. And no, it was not a floater. I've had floaters all my life - I'm familiar with them. This spot was quite fixed.

It really, really, bugged me. It made me realize how precious your vision is, and how fragile too. The eye was never designed to deal with laser radiation - at least not a direct hit from the beam. You know, the only sharp part of your vision is in the very center of the retina - the macula. This tiny part of the retina is about the size of a pinhead. If you were unfortunate enough to damage it you might never see anything well out of that eye again. Damage to the periphery of your vision can be quite bad but still not be obvious.

The spot slowly seemed to fade. I agree with Chris - I don't know if it actually healed, or if my brain is somehow compensating for it. I saw an eye doctor recently, and told the doc what happened. Doc gave me a thorough retinal exam, but could see nothing wrong. Told me my retina looked fine. Doc also told me that there are degrees of damage - apparently even low powered lasers can cause subtle celluar damage that's not obvious on an eye exam.

So... I still don't think these lasers should be banned, or regulated differentlty than they are now. BUT, buyer beware. Most of these lasers at worse can cause minor burns, but they ARE very damaging to the old peepers. So be carefull, protect your eyes and treat the laser with respect.

I shudder the thought of someone purchasing a 150 mW greenie without having prior experience with lasers.

-Eric B

Reply to
boo

I read in sci.electronics.design that Chris Carlen wrote (in ) about '200 mw green laser - safe?', on Sun, 6 Feb 2005:

It was probably a 'floater', a blob of cells exuded into the vitreous humour. I have lots of them in my left eye, due to a choroiditis about

40 years ago, and now I have a few in my right eye just due to anno domini. Their visibility varies greatly from time to time.

Such interpolation doesn't really happen, but damaged areas of retina can be very difficult to detect. The damaged area in my left eye extends from the periphery at about '4' to '5:30' on the clock face, inwards about half way to the centre, but I can only see it by deliberately looking for it with a specific object moved in my peripheral vision.

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Reply to
John Woodgate

of

to

accidental

I know nothing about lasers, but would think that 200mW also hurts/stings on normal skin, when hold still.

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Reply to
Frank Bemelman

Perhaps the inversion caused by the iris allows the laser light to "burn" part of the macula in the center of the eye, producing a blackend line, which the body slowly heals or it moves out of view?

Reply to
Mark Jones

I suspect over time, the brain can compensate for permanent damage, just as it does for the natural blind spot we are all born with.

I have had three separate jobs where I worked with lasers, and only at one was a special eye exam required. It involved a preliminary exam with retinal scan, at the beginning of my employment, to serve as a comparison for any later tests for eye damage. Without that preliminary scan, I don't know if small (but permanent) burns can be detected.

Mark

Reply to
redbelly

Sorry, what are you trying to say? The damage from a visible collimated laser is to the retina or its associated structures.

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Reply to
Sam Goldwasser

Sam

I bought a hp 5501 laser over the weekend at a swap meet it is a 1995 build date and looks different than the one in the laser page. Id be willing to photo it and send them to you for inclusion what size picts would you like horxvert pixels, kbytes

it was missing the front of the case (where the laser beam would come out.

I havent figured where to power it up yet. ive read the portion in the laser faq 2x now and havent figuered it oout quite yet.

Good Luck

JOhn Cincotta

Reply to
john cincotta

I'd like to see the pics but no guarantees on including them.

800x600 .jpg is probably good enough.

If it has the 4 pin din connector, it's just a matter of applying +/-15 V, and +5 V, and common to the appropriate pins. If you trace them to the inside, it will be obvious. If not, I can get you the pin designations.

Once power is applied (with the cover in place so the interlock is activated), the laser tube should come on in a few seconds, and if the rest of the electronics is operational, the "Locked" LED should come on in a minute or so.

How much different is it than the one in the Laser FAQ?

I assume you mean these pics:

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under "Hewlett Packard 5501 Helium-Neon Laser".

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Thanks.

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Reply to
Sam Goldwasser

is

Well the eye is not hollow, it has some kind of goo in the center, which is not just a clear liquid. Look at an eyeball in long-wave UV light - the inside will glow. A family member has a macular hole in this substance, severely affecting vision. Anyways, perhaps the iris focuses this "not too terribly bright" light enough to BURN the goo inside the eye, leaving a thin black line going from iris to retina. Slowly, over time, the damage is repaired.

I'm not sure if this is possible or not, just throwing out ideas. We do understand that the lens doesn't focus all the light energy directly onto the retina, right? There is some image-flipping going on there about 2/3rds the way to the retina. That tightly-focussed area is where I'm talking about. The light intensity-per-mil would be many times greater than "5mw."

ISTR that the cones in the retina are far more sensitive to green wavelengths however as a result of our evolution in distinguishing prey in green (leafy) environments. So it might be simple retina damage, dunno.

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Reply to
Mark Jones

part

laser is

not

iris

That "goo" is called the "vitreous humor". Depending on age (and other factors), may be a gel to a liquid. But, except for floaters, which are very common, it is very clear and shouldn't absorb visible laser light significantly at any power level we're discussing.

Even if damage to the vitreous were present, unless it was very close to the retina, the defect would be out of focus. Even with gel, it would move around somewhat, as do the floaters.

The light rays don't cross inside the eye for a collimated laser beam and normally focused eye. The smallest spot and highest power density is at the retina.

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Reply to
Sam Goldwasser

need

120mw of green does, at least at fairly close range. I'd be very hesitant to play around with 200mW and I've been messing with lasers for years.
Reply to
James Sweet

so when I'm not at work or leave my desk, I have a vacant mind? Pat

Reply to
Pat Ford

IMO, everything above 5mW is a class 1 laser, and involves training the people, safety interlocks, removing people from the site and such.

Rene

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Reply to
Rene Tschaggelar

This isn't by any chance the same laser that the FAA is looking for?

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