Risk Of Eye Damage From Lasers

[Dave Sheldrake]

Just a quick pic of how different wavelengths affect and damage the eyes.

299887

I'm sure most if not everybody knows but for those that don't please be aware anything above around 780nm - 820nm does NOT stimulate the human blink reflex so both the 1064 Fiber/Yag wavelength and the 10,600 CO2 wavelength will do damage before your brain registers there is a problem. Same with anything under around 380 down into the near UV/UV spectrum.

Like is often said "Do not stare into beam with remaining eye"

cheers

Dave

[Bill Stearns]

DAVE -
Good that you remind us of this! - 'cause, periodically, customers walking in - will be interested in my running laser machine and stare into the light! I tell 'em not to - but, well, you know ... maybe, not fast enough from what you're telling us.

Bill

[Scott Shepherd]

Thanks for posting that Dave, where's the CO2 wavelength come in there?

[abby ZHANG]

sounds that a pair of protect glasses is really necessary

[Dave Sheldrake]

The water bearing in-vivo soft tissue Scotty, (the middle image) from 1,400 NM to 1mm wavelength. The 1064nm Fiber / YAG is especially dangerous due to no blink reflex and the len's ability to pass that wavelength onto the back of the eye the (400 visible - 1,400 near infra red)

It's mostly the 780 - 1,400 range that concern, no blink reflex, invisible and deep damage to the back of the eye:(

cheers

Dave

[John Bion]

Hi Dave,
Thanks for this, my physics does not run too far past the: “don’t stare into beam with remaining good eye”; so for us simpletons, what are the implications of running enclosed lasers both on operators and general public. Having experienced “arc eye” several times in my life (welding difficult objects), I have no intention of staring at a bright light; however, does the “glass” on our laser cabinets protect us from the light spectrums you are speaking of? I have often wondered about both the health as well as insurance implications.
Thanks and Kind Regards, John

[Dave Sheldrake]

Heya John,

I'll have to refresh on the different classes as I think our system *may* vary a little bit from the US,but a class I laser (a laser with no line of sight to the beam) is considered safe but the same laser in an open bed machine may well be a class IV, classes aside though for the 10,600 wavelength (CO2 lasers both RF and DC Glass tube) simple clear cast acrylic absorbs the light at very close to 100% efficiency (part of the reason it cuts so well) if effect a sheet of 6mm acrylic will block the beam as well as a 4 inch thick brick wall.
So the most common types we all use if they are shielded present no real hazard (other than light flash blindness if you stare at the bright cutting point for extended time) that can be taken care of by the orange tint on most cabinet lid windows so overall yes they *can* in theory be dangerous but only if a set of very very unlikely conditions occur all at the same time. (think of it like a single bouncing betty in the Sahara, you *could* step on it but what are the chances)

1064nm is a little different, it is reduced by acrylic but to a far lesser extent so a lot of the energy will pass through, the protective sheets for 1064 are a different material (off the top of my head I can't recall what is used but Matt Knott at Halo will know straight away)

Insurers here go by the class of the machine, HSE go by examination to decide what class it is, I remember when I had the general engineering shop all the machines would get ignored and the inspector always made a bee-line straight for the two lasers I had, even now all these years later Graham the HSE chap has become a close personal friend but he leaves me with no illusions, if the lasers don't make the standard I get shut down the same day. There's not even a suggestion of flexibility ;)

AS to the UV systems, I *Believe* UV laser burns are photo chemical much the same as arc eye, and while not nice, due to them being at the surface they can be treated far more successfully than the deep damage of the 1064nm wavelength.Outside of my paygrade though so that would need to be verified.

I'll give Graham a call this afternoon and see if he can let me have the UK inspection standards to copy and post for people.

So far it seems to be enclosed systems, not a problem...open bed or unshielded galvo's etc...they look VERY closely. Matt Knott is the man here for that kind of stuff as Halo make Galvo systems in the fiber wavelength so I'm pretty sure he's forgotten more about that than I'll ever know. If I can get hold of Graham I'll give you a call later my friend

cheers

Dave

[John Bion]

Thanks for the info Dave.
Much appreciated :)
Kind Regards, John

[Mike Null]

Dave

Thank you very much for initiating this topic. We're looking forward to the followup.

Abby

Can you tell us what the material is in the safety glasses you pictured? How much do they cost?

[Darrin Davis]

Being concerned about the students in my classroom I asked the distributor of our GCC LaserPro support technician about "naked eye" viewing through the protective cover and here was the response along with a PDF document.

"Regarding laser eye safety, in general, if you close the PC Window when using laser, the laser light will not go through the PC window. However, we still recommend users wear safety glasses to protect eyes when operating the laser. Extra protection can’t hurt!"

http://rangerwoodshop.com/lasertest.pdf

Sounds like being over-safe is the new norm in our society. I personally don't wear the safety glasses unless I have the side panel removed for large objects but then again, I don't just sit there and stare at it either.

[Keith Colson]

My 2 cents on the subject...

What I have read is 10.6um c02 laser light does not go through glass. Glass and acrylic are supposedly opaque at this wavelength. Being the DIYer I am I plan to do some tests to truly confirm this as I don't believe everything I am told.

For a test, I will see if I can burn some paper after going through some glass. I would like to do this to be confident using my laser. What is still bad is the ?burning dot" you see in the laser machine could still be "too bright" for your eyes, some materials make brighter cutting light than others e.g. wood makes lots of light when cut where acrylic barely puts out any light at all, apparently it is not the infrared content that is the issue unless you engage the interlocks and run the machine with the doors open. I run the front door open when the sheet is too big to fit the bed.

Cheers
Keith

[Dan Hintz]

What I have read is 10.6um c02 laser light does not go through glass. Glass and acrylic are supposedly opaque at this wavelength. Being the DIYer I am I plan to do some tests to truly confirm this as I don't believe everything I am told.

The depth that frequency will pass through glass is measured in micrometers... you're good with a 1/8" thick piece ;) Not to mention, if glass passed that wavelength, we wouldn't be able to engrave it.

[Keith Colson]

Thanks Dan, I am familiar with microns and I am extremely pleased light is not measured in inches. My curiosity was what percentage of laser light would make it through the glass. Is it a flat 0% or does some make it through? You can still cut/engrave something that only absorbs a percentage of the lasers energy.

Cheers
Keith

[Dan Hintz]

In any thickness we would ever hope to handle, the energy will not make it through... as I said, the vast majority of energy will be absorbed within a couple hundred micrometers.

[Dave Sheldrake]

Being the DIYer I am I plan to do some tests to truly confirm this as I don't believe everything I am told.

Wise words Keith, I'd stake my life on it not penetrating but it's one time I'd also say ignore me and what I say,same with Dan, we are right but that extra test is always good for lasers.

Best test material is thermal printer rolls, the stuff they use on till's, that will change colour if even fractions of a watt get through at well below anything that will damage eyesight.

A good example is the 532nm wavelength, the laser pointers that produce this do so by taking 1064nm infra red and doubling the frequency (double the frequency halves the wavelength) so even though you may use a set of glasses proofed at OD6+ for 532 if they do not also block 1064 then you can still cook your vision. A good percentage of the green lasers that can be purchased still kick out 30-75% in the IR spectrum we just can't see it.Again no blink reflex so a 250mW pointer available from China may still be kicking out 150mW of 1064nm IR as well as a nice 90mW of bright green(more than enough to blind you with a beam you cannot see)

No offence to Dan (he's one chap I really listen to who DOES really know his stuff)or anybody else here but no matter what any of us say, be pedantic when it comes to safety, whatever any of us say(including me), verify verify verify and when you are sure, check again.

A Greek friend of mine who does a lot of work with laser diodes now reads with one eye after a tiny oversight :(

cheers

Dave