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Old 06-11-2010, 12:33 PM #1
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Default Safety terms

KNOW WHAT YOUR DEALING WITH:

THIS IS SHORT BECAUSE I HAVE TO GET TO WORK!


WITH CLASS IV LASERS, NOT ONLY IS THE DIRECT BEAM A HAZARD, THE BACKSCATTER FROM EVEN A DIFFUSE SURFACE HIT BY THE LASER CAN BE POWERFUL ENOUGH TO CAUSE DAMAGE TO THE EYE. THIS CAN BE TRUE AT CLASS III AS WELL

WHEN IS THE BACKSCATTER NOT DANGEROUS? IT IS ENTIRELY DIFFERENT FOR EACH SITUATION. MEASUREMENTS AND CALCULATIONS HAVE TO BE MADE. THERE IS NO HARD AND FAST RULE TO SAY A 1 WATT 445 nM LASER SCATTERED OFF A MATERIAL AT A GIVEN DISTANCE IS SAFE. YOU HAVE TO KNOW THE POWER OF THE LASER AND THE CHARACTERISTICS OF THE LASER AND THE SCATTERING SURFACE.

A QUICK ANSWER FOR THE 1 WATT 445 nM POINTER? SOME METERS/YARDS AWAY. WHY AM I SAYING METERS? I JUST BUILT IN A GENEROUS SAFETY FACTOR FOR MY OWN MENTAL HEALTH REASONS.

INVERSE SQUARE LAW APPLIES TO THE SCATTER FOR MOST MATERIALS, AND THUS DISTANCE IS MAJOR FACTOR IN THE SITUATION. BUT SOME MATERIALS, GLASS AND CERAMICS AND SOME TRANSPARENT PLASTICS, FOR EXAMPLE, CAN BE RETROREFLECTORS

WHILE THIS MAINLY APPLIES IN DOORS, IT IS A FOOLISH THING TO AIM A CLASS III OR IV LASER OUTDOORS NEAR OTHER PEOPLE, BECAUSE OF BACKSCATTER!


DANGER, DO NOT DO THIS TEST, THIS JUST A EXAMPLE OF WHY YOU NEED TO EVALUATE EACH SITUATION YOU USE A HIGH POWERED LASER IN!


[/COLOR]
DO NOT AIM THE LASER AT A BICYCLE REFLECTOR , REFLECTIVE TAPE< OR CAR TAIL LIGHT FOR EXAMPLE, A SOMEWHAT DIFFUSE BEAM WILL COME RIGHT BACK AT YOU, BUT IT MAY NOT BE DIFFUSE ENOUGH TO PROTECT YOUR EYES. MOST BICYCLE REFLECTORS AND MANY CAR TAIL LIGHTS ARE
"RETROREFLECTORS" BY DESIGN, THE OPTICS DESIGNED TO REVERSE THE COURSE OF THE LIGHT RIGHT BACK DOWN THE PATH OF WHICH IT CAME. SOME OF THEM ARE BETTER THEN OTHERS, AND THE BIKE ONES WITH THOUSANDS OF MOLDED PRISMS CAN BE VERY GOOD AT REVERSING A LASER BEAM.

SILLY EXAMPLE: IF DARTH VADER MOUNTED A HIGH QUALITY RETRO-REFLECTOR ON A SERVO DRIVEN TURRET ON THE DEATH STAR, LUKE WOULD NOT HAVE MADE IT TO THE SEQUEL.

YOU GET THE IDEA!

NOT ONLY CAN RETROREFLCTORS DO THIS, UNDER CERTAIN CONDITIONS, THINGS LIKE GLASS RODS AND GLASSES OF WATER AND PLASTIC BOTTLES CAN REFLECT ENOUGH ENERGY TO CAUSE A PROBLEM!




(Steve said DO NOT DO THIS. SO I"M GONNA DO IT!, THAT GIVES ME NIGHTMARES. OK, IF YOU MUST, DO IT WITH A 1 mW HENE, BUT NOT MORE THEN CLASS II OR CLASS IIIA LASER, IE NOT MORE THEN 5 mW, EXPECT TO BE BLASTED IN THE EYE IF YOU DONT SET THE LASER ON A TABLE AND HOLD THE RETROREFLECTOR INTO THE BEAM, USING A WOOD STICK PAINTED BLACK WHICH REMOVES YOU FROM THE TARGET AREA, MAKE SURE YOU HAVE TOTAL CONTROL OF ENTRY TO THE ROOM AND THAT NO ONE ELSE IS AROUND THE LASER. GET USED TO PLANNING YOUR EXPERIMENT!)


SOME OTHER THINGS I've SEEN THIS MORNING THAT NEED TOUCHED ON:

Nominal Ocular Hazard Distance (NOHD):

The calculated distance in which it is possible to exceed the Maximum Permitted Exposure.

Maximum Permitted Exposure (MPE)


Maximum permissible exposure (MPE), is the level of laser radiation to which a person may be exposed without hazardous effects or biological changes in the eye. MPE levels are determined as a function of laser wavelength, exposure time and pulse repetition. The MPE is usually expressed either in terms of radiant exposure in J/cm2 or as irradiance in W/cm2 for a given wavelength and exposure duration.




Note, these are calculated numbers. IF I have my seven watt argon outdoors, the NOHD is upward of eight miles. Does that mean I can safely stand at 8.1 miles and view the beam head on? ABSOLUTELY NOT!
If I accidently illuminate a aircraft at distance farther the the MPE, its good odds that the pilots vision will be OK, but that does NOT mean it will NOT Disorient him or Flashblind Him.


Does that mean I can use a 20 watt ion laser turned down to 7 watts and be just as safe, NO! The longer 20 watt ion cavity has less divergence, because it has a longer resonator, and this less divergence. SO the NOHD is father for the better beam quality laser.


DO I CALCULATE THE MPE AND BASK IN THE LASER LIGHT AT THE MPE?
NO, INTENSE LIGHT EXPOSURE IS CUMULATIVE, TIME MATTERS!

IS it ok to spend 10x as long illuminated at 1/10 the MPE, Close, but not quite. You can still experience long term biological effects with short wavelengths etc.

It would take me a full day to research and post VERIFIED, VALID, examples, pictures and drawings, and laser safety fills whole books, like this one:

http://www.army.mil/usapa/med/DR_pub...f/tbmed524.pdf


HEADS UP FOLKS, PHYSICS IS COMPLEX, AND CAN BITE YOU. (BUT USED WITH CAUTION, AND PREPAREDNESS, IT CAN BE FUN)

KNOW YOUR TARGET !!! TEST AT VERY LOW POWERS.

(This is why lab lasers and industrial/medical lasers tend to have power controls and aiming beams.)


ONE OTHER THING, QUALITY CONTROL, JUST BECAUSE A EXPERIMENT WAS SAFE FOR YOU, DOES NOT MEAN THE MATERIALS AND GEAR ARE SAFE FOR THE NEXT GUY, PRODUCT VARIATIONS DO HAPPEN, AND NOT EVERYONE MAKING GOGGLES FOR EXAMPLE, ARE LEGIT OR TRAINED ENOUGH TO DO IT RIGHT! QUALITY CONTROL REQUIRES THINKING, PLANNING AHEAD, PAPERWORK, AND MEASUREMENTS, AS WELL AS SOME ONE ELSE CHECKING YOUR WORK BEFORE YOU RUN THE EVENT!

THE POINT OF THIS POST IS SO YOU CAN BE SAFE AND UNDERSTAND WHY CLASS IV LIGHT SOURCES DO NOT BELONG IN UNEDUCATED HANDS AND DO NOT BELONG IN UNCONTROLLED CONDITIONS!

DISClAIMER: I'M NOT A SPECIALIST IN LASER SAFETY, MOST PLACES WHERE I WORK WITH HIGH POWER LASERS, I'M DEPENDENT UPON THE WORK OF LASER SAFETY SPECIALISTS, WHO ARE EITHER ON SITE OR HAVE PROVIDED GUIDELINES. AND AT MANY OF THOSE PLACES, A SPECIALIST COMES AND CHECKS WHAT I"M DOING PERIODICALLY, TO MAKE SURE I'M FOLLOWING THE GUIDELINES AND NOT MISSING A DETAIL.

IF I even think I have to, I DO THE MATH! DON'T ASSUME ANYTHING!


Steve (WHO IS NOW LATE FOR WORK)



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Old 06-11-2010, 12:49 PM #2
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Default Re: Safety terms

This is very good information, but please edit it and remove the capitalization. It makes it very hard to read, which is a shame because this could prove to be very valuable knowledge.
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Old 06-11-2010, 01:32 PM #3
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Default Re: Safety terms

Hey Steve......

Very Confusing.... 2 similar Threads in 2 different boards....
with the same identical Title....

Jerry
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Old 06-11-2010, 01:35 PM #4
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Default Re: Safety terms

Can you turn of caps lock?
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Old 06-11-2010, 09:56 PM #5
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Default Re: Safety terms

I'm a bit concerned by Wicked Laser's safety claims, especially its "NOD" (sic) rating of a mere 200m. I came across this document on Laser Safety for Laser Operators, and was particularly interested in its radius of NOHD (R_NOHD) that it derives.

From what I gather, the basic equation is this:
R_NOHD = [ (4P / (pi*E_MPE))^(1/2) - D1] / alpha (cm)
Where P is the power (watts), E_MPE is the Energy of Maximum Permitted Exposure (for ocular exposure), D1 is the diameter of the laser at aperture, and alpha is the divergence.

The value of E_MPE is taken from ANSI Z136.1 (1983, table 5), and for the wavelength of these lasers, and the expected exposure times (18 x 10^-6 to 10 seconds), this is calculated as:
E_MPE(t) = 1.8 * t^(3/4) x 10^-3 (J/cm^2)
where t is time in seconds.

For Wicked Laser's stated laser specs: 1.5mrad divergence, 1.5mm beam diameter at aperture, and a minimum 500mW power rating for a Class IV laser, the resulting calculation is:
R_NOHD(t) = [(4(0.5) / (pi * 1.8t^(3/4)*10^-3 ))^(1/2) - 0.0015] / 0.0015
For the shortest exposure time of 18 x 10^-6 seconds this would yield:
R_NOHD(18 x 10^-6 s) = 754197 cm ~ 7.5 km
I believe I've done the math correctly. Can anyone confirm?
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Old 06-12-2010, 04:03 AM #6
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Default Re: Safety terms

From Skyzan II Software, by Rockwell Laser Safety, inc

Kind Courtesy of , Laser Wizardry, INC.

.25 second standard exposure, typical for airspace safety paperwork.

Some numbers based on Wicked's claimed 445 nM Artic Blue, others are things I have needed in the past, and some are just made up examples.

The KTP532 and Tandom Pair AR/KR ion numbers are from a real show, as are the Laserscope KTP532 numbers.

Do note how things change for my 2003 New Years Eve show , when we change from graphics, to beam effects at 15' max angle from the horizon, this is why pilots are concerned about lasers, even when at altitude.

Just so they don't get reused on a submission document, by someone who is lazy, KTP and Tandem Pair numbers are copyright 2010, All rights reserved.

All numbers are in Feet, because the Aircraft governing body in the US uses FEET!

We know most nations use meters. We know we should round these off as needed.
But its just for a example.

For Mr Bionic-Badger, 223 meters, calculated, is correct for the numbers stated by Wicked.


NOHD = 2.6 mW per cm ^2
SZED = 5o uWatts per cm^2
CZED = 5.0 uWatts per Cm^2
LFED = 500 nanowatts per cm ^2

Nominal Ocular Hazard DISTANCE = NOHD
Sensitive Zone Exposure Distance = SZED
Critical Flight Zone Exposure Distance, = CZED

BE CAREFUL, Please do not go measure off a distance and look down a beam based on these numbers, each individual laser is different, and thus measurements have to be made,

Steve



----------------------------------
AT 1.5 mm and 1 milliradian:
1 WATT 445 nm
WICKED Arctic III Blue

NOHD = 734 feet
SZED = 3702
CZED = 16,556
----------------------------------------
At 1.5 mm and 1.5 Milliradian
1 WATT 445 nm
Wicked Arctic III Blue

NOHD = 489 Feet
SZED = 2468
CZED = 11,037
------------------------------
At 1.5 mm and 2 milliradians for 405 mW
400 mW

NOHD = 232 Feet
SZED = 1171
CZED = 5235
-------------------------------
At 2 mm and 3 milliradians for 405
400 mW

NOHD = 155 FEET
SZED = 780
CZED = 3490
-----------------------------
1.5 mm and 2 milliradians for 650 nm
250 mW

NOHD = 183
SZED = 926
CZED = 4139
------------------------------

1.5 mm and 1.5 mR 650 nm
250 mW

NOHD = 245
SZED =1234
czed =5519
---------------------------
.65 mm and 1 mR 532
200 mW

.8801

NOHD = 328 feet
SZED = 1656
CZED = 7404
----------------------------------
.65 mn and 1 mR 532
1000 mW
NOHD = 734
SZED = 3702
CZED 16,556
-------------------------------
KTP532 Q switched
40 watts
4 x10-3 Joule per Pulse.
4 x10-7 pulse width
10 Khz rep rate
2 mm dia
5 mR divergence

NOHD = 1761 FEET
SZED = 4683 FEET
czed = 20,942 FEET
LFED = 209,419 FEET

--------------------

Steve's New Years EVE Show, FAA/CDRH approved, 2003
12 Watts 457-676 12 Watts 1 mR
Tandem pair of Ion Lasers, One Argon, One Krypton

Angle of Elevation zero degrees, (graphics mode)
NOHD = 2215 FEET
SZED = 12,827 FEET
CZED = 57,400 Feet


With respect to aircraft, my show, at 15' Up ANGLE FROM THE SCANNERS:
(Beam Effects Mode.)

NOHD = 2215, --- 651 foot altitude
SZED = 12,827, --- 3320 Foot Altitude
CZED = 57,400 ---14,856 Foot Altitude
(obviously why pilots can get very annoyed!)





Visual correction Factor for 445 nm = .0305
Visual correction Factor for 443 nm = .0275
Visual correction Factor for 405 nm = .0008
Visual correction Factor for 650 nm = .107
Visual Correction Factor for 532 nm = .8801

--- msg ends---

Last edited by LSRFAQ; 06-12-2010 at 04:32 AM.
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Old 06-12-2010, 05:00 AM #7
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Default Re: Safety terms

In this day and age we're obsessed with safety and dangerous stuff. That's why kids playgrounds are full of rubber and plastic and bark chips. I grew up playing with chemicals and making my own fireworks. Sure I've got some scars (a row of them on my stomach) and a permanent ringing in my ears but I survived! LOL
I'm not making fun of the safety warnings here, I take it very seriously, hell I value my eye sight and I don't wanna live the rest of my life half blind, but a lot of things we do in this life are dangerous - driving a car for instance - so what do you do, sit in a padded room wearing a helmet for your whole life, or get in there and live it, blood, sweat, mud and danger and all?

I have a serious question for the technically minded here. How do these big laser show systems not damage peoples eyes? I mean, I know about pulsing, but is that the whole story? Fact remains there's enough power to produce big impressive bright beams and the whole kit and kaboodle is aimed squarely into the faces of the onlooking crowds... it doesn't make sense to me...
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Old 06-12-2010, 05:21 AM #8
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Default Re: Safety terms

If the show was done properly, attenuation mapping could have been used to turn down the power in the audience area, or they could have increased the divergence of the laser, or used a perfect amount of haze etc.

Theres a few other ways I can't remember right now.
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Old 06-12-2010, 12:00 PM #9
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Default Re: Safety terms

IN the US, You keep things 2 meters horizontal from the Audience and 3 Meters vertical. In other words, you keep it away. The scattering off a wall or smoke is, at maximum, Class I at the audience.

There is a huge set of guidelines and procedures you follow, and you have quality control sheets for your hardware and a inspection you are supposed to do pre show and post show.

We also use techniques such as masking. My projector has a 1/32" thick AL mask. The projector is locked down on scaffolding. I would set up the beams and scan effects in a empty, controlled auditorium, and then turn the power way down, and mark the mask for drilling.

For going into airspace, or doing a show outdoors, there is a whole new layer of procedures to get a NOTAM issued to let pilots know where the laser activity is, so they can stay out of it. You have aircraft spotters looking for aircraft visually. If a aircraft is even getting close, your duty is to terminate. And you have two different means to contact the local Center, Tracon, or Tower, usually a cell and a landline, or two cells on different carriers etc.
This takes 30-90 days of advance notice to set up, and a bunch of calculations, photos, map co-ordinates, contact plans and timing.

You end up with a letter of "No Objection" from FAA and/or DOD, spelling out the conditions you operate under. You call in and inform them of startup, and then post show, you call in and inform them of shutdown.

This is true in most countries around the world, you have to contact ATC, ie Germany, UK, US, Canada, OZ and most of Europe all have similar systems and restrictions for lasers in airspace.

And it applies to scientific users, such as LIDAR and Laser Gudestars, as well.

Get the idea?

In Canada, Europe, South America, China, you add a new dimension to the problem. First off just because the beams are scanned, do NOT get the illusion that scanning faster adds safety, when you do the math, it really doesn't help and at some point it folds back on you and starts to raise your MPE. But spreading the distribution of where the beam is in time and space lets you achieve the MPE, to a point.

When you audience scan, if you do it right, you calculate and measure the MPE for each scanned effect, and you'll find the scanners zero line is set some distance above the crowd's head. Effects below the zero line are structured to be below the MPE, and while they may look equal in power to the hot stuff above the line, usually they are not. The software does attenuation mapping, color changes, eliminates "hard" points where there are static beams, adds position jitter, and you define the show so that it always sweeping over different areas.

Distance is your friend. Obviously you need to keep people back a calculated distance from the scanners!.

You also have feedback signals from the scanners, and if the scanners fail, the scanfail takes down the master shutter, hopefully in milliseconds, or less.
If your close to the MPE, your 100 to 250 millisecond blink time helps to protect you, somewhat.

In reality, a audience scanning show is ran overseas (I'm in the US) at 10X MPE or somewhat more.

Also, effects are timed. IE a given effect might be good for 10 seconds or 30 seconds before it exceeds the MPE, and done right, you'll notice much of the show is actually in the air, with breaks in between the audience scanning.

Where this breaks down, is as lasers have gotten cheaper, the controls have eroded, and Joe Blow buys a projector for 1000$, there is no enforcement of the quality control, does audience scanning, and some one gets hurt. Or he shoots into airspace without due regard and never files for the permits. Or he does not use a scanfail. Or in the case of Aquamarine Rave in Moscow, a high energy pulsed laser was aimed into the crowd for audience scanning, most likely by a under trained technician, in a rush, because the show was moved into a tent at the last minute. A lot of people went to the hospital

One DOES NOT USE any pulsed laser, be it Qswitched, Mode Locked, or Femtosecond, for audience scanning. The high peak energy rips through someone's retina far faster then you can blink. You DO NOT audience scan with Copper Vapor or Qswitched Yag lasers.

If you look at the statistics, audience scanning, done properly and in a licensed, inspected, system such as in the UK, Germany, is far safer then a ride at the amusement park. Its the rogue operators/untrained people, that can mess things up.

This is why various people and governments get very concerned as costs go down and availability and power levels go up.

And yes, I've viewed quite a few audience scanned shows, done legally by a professional in Canada, with measurements, and my retinas are just fine.

The problem is when a UNTRAINED PERSON can pick up a used 30-40 watt Qswitched medical laser for 500$ some place and and does not know any better. Not too many people take a laser power meter to a club. And it takes more gear then just a power meter to make the measurements. You really want a professional doing this sort of thing, and someone checking up on them periodically.

CONSISTENT QUALITY CONTROL = SAFETY!!!


Caveat, YOU CANNOT MOVE A POINTER BY HAND FAST ENOUGH TO LOWER THE MPE IN A CONSISTENT, REPEATABLE MANOR.

CAVEAT II, You must do measurements and calculations for each scanned effect!!! MPEs are cumulative!.


Steve

Last edited by LSRFAQ; 06-12-2010 at 12:10 PM.
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Old 06-14-2010, 03:48 AM #10
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Default Re: Safety terms

Quote:
Originally Posted by LSRFAQ View Post
----------------------------------
AT 1.5 mm and 1 milliradian:
1 WATT 445 nm
WICKED Arctic III Blue

NOHD = 734 feet
SZED = 3702
CZED = 16,556
----------------------------------------
At 1.5 mm and 1.5 Milliradian
1 WATT 445 nm
Wicked Arctic III Blue

NOHD = 489 Feet
SZED = 2468
CZED = 11,037
------------------------------
At 1.5 mm and 2 milliradians for 405 mW
400 mW

NOHD = 232 Feet
SZED = 1171
CZED = 5235
-------------------------------
At 2 mm and 3 milliradians for 405
400 mW

NOHD = 155 FEET
SZED = 780
CZED = 3490
-----------------------------
1.5 mm and 2 milliradians for 650 nm
250 mW

NOHD = 183
SZED = 926
CZED = 4139
------------------------------

1.5 mm and 1.5 mR 650 nm
250 mW

NOHD = 245
SZED =1234
czed =5519
---------------------------
.65 mm and 1 mR 532
200 mW

.8801

NOHD = 328 feet
SZED = 1656
CZED = 7404
----------------------------------
.65 mn and 1 mR 532
1000 mW
NOHD = 734
SZED = 3702
CZED 16,556
-------------------------------
KTP532 Q switched
40 watts
4 x10-3 Joule per Pulse.
4 x10-7 pulse width
10 Khz rep rate
2 mm dia
5 mR divergence

NOHD = 1761 FEET
SZED = 4683 FEET
czed = 20,942 FEET
LFED = 209,419 FEET

--------------------

Steve's New Years EVE Show, FAA/CDRH approved, 2003
12 Watts 457-676 12 Watts 1 mR
Tandem pair of Ion Lasers, One Argon, One Krypton

Angle of Elevation zero degrees, (graphics mode)
NOHD = 2215 FEET
SZED = 12,827 FEET
CZED = 57,400 Feet


With respect to aircraft, my show, at 15' Up ANGLE FROM THE SCANNERS:
(Beam Effects Mode.)

NOHD = 2215, --- 651 foot altitude
SZED = 12,827, --- 3320 Foot Altitude
CZED = 57,400 ---14,856 Foot Altitude
(obviously why pilots can get very annoyed!)





Visual correction Factor for 445 nm = .0305
Visual correction Factor for 443 nm = .0275
Visual correction Factor for 405 nm = .0008
Visual correction Factor for 650 nm = .107
Visual Correction Factor for 532 nm = .8801

--- msg ends---
This is all very interesting, (and I truly mean that), but can you clarify what NOHD, (I think you have already in this post but... ); SZED; CZED; LFED and; etc; actually mean please?

I know this is exactly what people need to know and the formulae for calculating may be above an beyond most of us but a brief explanation may help when you have the time.

Thanking you Steve,

Morgan
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Old 06-17-2010, 03:55 PM #11
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Default Re: Safety terms

Oh wow, thanks for finding that book, been reading it, very cool.
And thanks for writing this up, it's very needed.
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Old 06-21-2010, 10:29 PM #12
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Default Re: Safety terms

sorry for going offtopic:
is this steve (LSRFAQ)the same from Wicked Lasers?
thx.
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Old 06-22-2010, 03:50 AM #13
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Default Re: Safety terms

Quote:
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sorry for going offtopic:
is this steve (LSRFAQ)the same from Wicked Lasers?
thx.
God no.

Steve R.
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Old 06-24-2010, 10:07 PM #14
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Default Re: Safety terms

I love LeetKey. "To Lowercase", click, eyecancer gone
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Old 06-25-2010, 01:20 AM #15
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Default Re: Safety terms

Quote:
Originally Posted by LSRFAQ View Post
It would take me a full day to research and post VERIFIED, VALID, examples, pictures and drawings, and laser safety fills whole books, like this one:

http://www.army.mil/usapa/med/DR_pub...f/tbmed524.pdf



Looks like some interesting reading.
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Old 08-22-2010, 04:04 PM #16
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Default Re: Safety terms

we must be careful, I am deacuerdo and so it , I I have much taken care of, but even always aprede something lellendo these pos, thanks

Last edited by ppbss; 08-22-2010 at 04:27 PM.
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