My Eyes! My Eyes!

Hallucynogenyc said:

hell, it's 15mW, scanners go up to the watts order. Would you personally use safety goggles to operate that? really?

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15mW is still 10mW above what is eye safe. Also, many other lasers (20mW, 50mW and 150mW) were mentioned here.
As far as I remember, polished brass reflectivity is above 66%, meaning that even if the 15mW is the only laser in question, and it is not above spec, you are risking a 10mW direct hit. Not safe.

Hallucynogenyc said:

Brighter is safer because you'll see it coming before

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Are you an agent in the Matrix? I would like to see you dodge the random reflections from a mirror moving on a speaker, in a room with shiny objects such as large piece of brass in the ceiling.

Seb

you are risking a 10mW direct hit. Not safe.

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Divergence, speed etc... and still, above 5mW is "where you start to have chances to get damage". I think the problem was me using the word "safe". It's not that I mean it's safe, it's that the risk too small!

Now I can definitely agree that the risk is not very large with ~10mW moving, at a distance, etc. However the risk is there, so the problem was exactly that you said "safe". Personally I do have a small black spot, and that was from a brief hit from a 26mW laser my cousin was playing with, reflected off a glossy cupboard door, with reflectivity of 50% at the most... so it can happen if you are unlucky.

f22warzone.. with the amount of accidents you have had, it seems they were due to carelessness.

EDIT: Quote removed

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Does not sound like someone you would want to accept safety advice from.

EDIT: Thank you f22warzone

Seb

yeah well, I think you missunderstood me. I didn't meant safe as "0 risk" but as "low risk". If you take safe as "0 risk", even 5mW isn't safe, you know

The difference is, with 5mW you can blink before any damage is done - with 10mW, it may damage you before you manage to react.

A 2 metre fall can injure you or kill you if you are very unlucky, but most people will just jump down, land, and walk on.
A 5 metre fall is likely to sprain your ankle, hurt your knee, make you fall and bang your head on something after you land, etc. Some people will be lucky enough to make the jump with no injuries, but far more people will get minor or major injuries.

Most people would tell others that a 2 metre jump is safe, few people would tell an average person that a 5 metre jump is safe.

Seb

mrgoogfan said:

15mw on a scanner? Assuming he is scanning it at a decent speed, he said a specular reflection off a ceiling fan blade etc, it would be at least 15 feet. Scanned across the eye once, the total power received at the retina would be on the order of microwatts, averaged out across a line on the retina. Each cell would only receive maybe .5uW, assuming his eyes are focused at infinity (which inside they are probably not)

so, unfocused ~.05mm spot, scanned across the cells at a couple hundred cell lengths a millisecond, is safe imo.

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Your WRONG!

Way WRONG!!!

In a few days I will figure out how to link PDFs to my post...

I will post the PDF for calculating a sinusoidal scan if I can.. Problem is , you need measurement gear most LPFers DO NOT HAVE to audience scan, and I am WEARY of posting the means to attempt to DO SO.

Speeding up the laser DOES NOT significantly reduce cumulative exposure of a repeated scan.

Meanwhile back at the Ranch, F22WARZONE and I are going to have a chat at the laser show forumn... On SAFETY!!

Steve

LSRFAQ said:

Your WRONG!

Way WRONG!!!

In a few days I will figure out how to link PDFs to my post...

I will post the PDF for calculating a sinusoidal scan if I can.. Problem is , you need measurement gear most LPFers DO NOT HAVE to audience scan, and I am WEARY of posting the means to attempt to DO SO.

Speeding up the laser DOES NOT significantly reduce cumulative exposure of a repeated scan.

Meanwhile back at the Ranch, F22WARZONE and I are going to have a chat at the laser show forumn... On SAFETY!!

Steve

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I'd love to see these PDF's to finally prove these newbies wrong. You can post a PDF the same way you'd post a JPG. Or, you could upload it to a place like MEGAUPLOAD - The leading online storage and file delivery service and then link us.

Mr MGOOGFAN:

Your homework assignment:

John C. O'Hagan's thesis on laser safety...

http://www.laserfx.com/BasicSafety/C...n Hazard.pdf

and:

http://www.army.mil/usapa/med/DR_pubs/dr_a/pdf/tbmed524.pdf

READ IT! TEST FRIDAY!

Start at Page 33 Nominal Ocular Hazard Distance... In the Army one. Then admire the damaged safety goggle collection on page 69...

Steve

HOW DO I GET THE EYE SAFETY SINGLE EXPOSURE TIME GRAPH ON PAGE 49
INTO A PICTURE HERE ?? Without printing it, taking it to Kinkos and scanning it?
I Dont have a scanner at the new apartment..

John C. O'Hagan's thesis on laser safety...

http://www.laserfx.com/BasicSafety/Chapter 5 Quantifying the Laser Radiation Hazard.pdf

Steve

f22warzone said:

Just saying yes you only have 2 eyes but sometimes we here are a bit too worried about it especially if it’s only 15 mw.

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No such thing. Safety's important and ALL lasers should be properly respected. People who can't respect them shouldn't own them. The bottom line is that ANY LASER over 5mW is potentially dangerous. We can debate the intricacies of various situations (beam movement, reflective surfaces, etc), but it's always best to have blanket rules regarding safety, especially when new people come asking about it. If it's over 5mW, it's potentially dangerous. It's that simple.

While we are talking about 15mW of green, I also seem to recall over 100mW of red in the OPs original question. Obviously this is also dangerous.

There are many scenarios in which a "scanner" might emit a static beam. Unless safety features are built in to prevent this under ALL possible circumstances, the system should be treated as if it will ONLY emit static beams.

From O'Hagan

Table 5.1 NOHD as a Function of Radiant Power and Beam Divergence for a
Single Accidental Exposure to a cw Beam
Radiant Power ®
Divergence ¯
...... ... 100 mW .... 1 Watt ..... 10 Watts
1 mrad .... 71 m .... 224 m .... 708 m
2 mrad .... 36 m .... 112 m .... 354 m
5 mrad .... 15 m .... 45 m .... 142 m

Nominal Occular Hazard DATA, for a single exposure, to a single beam ,
for a few divergences. The number followed by m is the distance in meters you have to be from the laser for a single flash to be safe for ONE SINGLE EXPOSURE, The number in milli Radians is the beam divergence. For most pointers, you could assume .2 to .5 mRad, so the distance is actually longer. CONDITIONS: visible laser, not UV or IR, assumes your blink reflex works and Tmax is .25 second limited by your blink response..

THIS TABLE IS FOR A SINGLE PULSE, NOT A REPEATING SCAN.

So for a 100 mW LASER, WITH A FAT BEAM, you'd need to be at least 71 meters away to be barely safe, from a beam reflection off a mirrored surface. However the NOHD is going to be a painful flash. In reality we would DOUBLE that distance to be on the SAFE SIDE..

The original poster is going to be JUST A FEW FEET away..

THE EFFECTS ARE CUMULATIVE< SO ITS NOT SAFE TO TELL YOUR FRIENDS TO GO STAND AT THE END OF A FOOTBALL FIELD WHILE YOU HOSE THEM WITH THE LASER IN THE FACE!!!!!!!!!! PLEASE DO NOT USE THESE NUMBERS TO EXPERIMENT WITH EYE SAFETY!!!!

IN EACH SAFETY SITUATION, THE ONLY WAY TO BE SAFE IS TO ACTUALLY DO MEASUREMENTS...

THE BEST WAY IS TO NEVER GET LASER LIGHT IN YOUR EYE!

STEVE

ElektroFreak said:

No such thing. Safety's important and ALL lasers should be properly respected. People who can't respect them shouldn't own them. The bottom line is that ANY LASER over 5mW is potentially dangerous. We can debate the intricacies of various situations (beam movement, reflective surfaces, etc), but it's always best to have blanket rules regarding safety, especially when new people come asking about it. If it's over 5mW, it's potentially dangerous. It's that simple.

While we are talking about 15mW of green, I also seem to recall over 100mW of red in the OPs original question. Obviously this is also dangerous.

There are many scenarios in which a "scanner" might emit a static beam. Unless safety features are built in to prevent this under ALL possible circumstances, the system should be treated as if it will ONLY emit static beams.

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this is all very true in that a blanket system should be used to protect people. and yes lasers should be treated with respect as they could potentially blind some body.

Is this the graph you wanted Steve?



Open the PDF on your computer and then press "Print Scrn" on your keyboard, it should be directly above the Insert and Delete keys which are above the arrow keys typically. Once you've done that, open an image editor such as paint and then paste your image into a new document ( Either by using keyboard shortcuts, the edit tab or your mouse ) and then cut the section you want out. You can either delete the part which isn't cut or paste the part which you cut into a new document to save it.

Hey Guys-

I just want to comment here brifly without getting into mathematics and fancy terminolgy. I try (even for my own sake) to stay as "common sense" as possible.

It worries me a little to see some of the replies here. A Laser is a Laser is a Laser. Lasers can and do cause eye sight damage and problems. Unfortunately, these are *usually* not instantaneous problems. they usually occur very minutely over time.

the bottom line with Laser safety is overly cautious is NEVER too much.

Guys- A fast moving laser beam poses *almost* the exact same danger to our eyes that a static beam does. You need to remember, All of these images and effects that we see, are all just ONE laser beam being moved very rapidly. At any one given point in time, there is just one beam present in one location for a given period of time.

If your eye happens to be that "one location" for that given period of time, you are going to have a very bad day!!

the only sure fire ways to lower damage possibilities with lasers is to enlarge the diameter of the beam so that the power density is vastly decreased and to also distance from the source. Movement of the beam(s) do provide a miniscule amount of safety. but not in the manner that i have seen defended here.

"The beam is moving too fast to cause damage" is *NOT* a factual answer.

It sounds "cliche" but we only get one set of eyes. Do we really want to test some of these theories we have seen here?? Are the *odds* of being hurt by a laser pretty low?? Yes, of course. But please don't misconstrue some of the safety responses given here as defenses for poor safety practice.

i am not picking on any one's response. I for one, am much more obliged to read the factual safety standards than to come up with my own conclusions based on some peoples personal experiences with "accidental" over exposures!!

Lets keep it fun and safe everyone!!!! :yh:

-Marc

Very nice responses from CT Lasers and LSRFAQ!
+1

Seb

CT Lasers said:

the bottom line with Laser safety is overly cautious is NEVER too much.
.....

the only sure fire ways to lower damage possibilities with lasers is to enlarge the diameter of the beam so that the power density is vastly increased and to also distance from the source. Movement of the beam(s) do provide a miniscule amount of safety. but not in the manner that i have seen defended here.

"The beam is moving too fast to cause damage" is *NOT* a factual answer.

It sounds "cliche" but we only get one set of eyes. Do we really want to test some of these theories we have seen here?? Are the *odds* of being hurt by a laser pretty low?? Yes, of course. But please don't misconstrue some of the safety responses given here as defenses for poor safety practice. ...

-Marc

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This guy knows what he is talking about and i have retracted all of my experiences and just labeled them as lucky and glad that i was testing on my self instead of putting some body else eyes at danger : )