Lasers (again!)

[TimR]

I've had a search both on here and some other sites and I have yet to find concrete answers for a few things relating to lasers.

 

I've recently purchased a 30mw green Kam DMX laser. I know that audience scanning has a few H&S strings attached to it, and so I've ordered a copy of HSG95 to guide me through completing a risk assessment before turning anything on with a live crowd.

 

The one thing thats worrying me is that a few places have stated that any performance laser without a keyswitch to enable/disable it is flat out illegal to operate in the UK. Is this true? Have I been sold an illegal unit? If so, does anyone know if wiring said laser to a 13amp spur and installing a keyed switch would be acceptable?

 

Sorry if this has been covered and I've missed it. I'd really appreciate a laser guru giving me a hand.

 

Thanks.

[Brian]

At 30mW you've got a class 3B device. The European standard for laser systems requires that class 3B devices have key-operated master control switches.

[musht]

Not any actual criminal law directly aimed at display lasers in the UK, that I am aware of, but mebbe just not aware of any....

 

But anyway , use of the word `illegal` should be substituted for `ill advised` key switch will save some drunken dj/punter going `gies a go of your laser chief !`. Put it into the mains or the supply to the diode regulator, not in between regulator and diode, laser diodes are very fragile.

 

Audience scanning is really a whole lot of trouble, Maximum Permitted Exposure , MPE as HSG 95 rattles on about is not straightforward to calculate and you should have scan failure detection fitted to drop the beam in the event of it going static.

 

Can be quite uncomfortable for the audience as well to be honest, 30mW isnt going to give an amazing liquid sky but in otherwise dead black out can be ok, bounce mirrors and mirrors on spinners placed around the room van be very effective, as long as they don`t slip and aim static beam into customers eyes.

 

www.photonlexicon.com is a friendly laser forum with a slant towards display and several UK members.

[Tomo]

Legally, the keyswitch requirement will probably come under CE marking - thus illegal to sell something that does not conform to the EU standards for the 'something' - in this case, a LASER system.

 

Does the unit have a CE mark, and is it clearly labelled with the class of LASER device that is really is?

 

As far as audience scanning is concerned - very difficult, and extremely dangerous if you get it wrong.

A blind punter is probably worse than a dead punter, at least as far as payouts are concerned!

[chipito]

A blind punter is probably worse than a dead punter, at least as far as payouts are concerned!

Blimey !

How powerful does the laser have to be to kill 'em?

(and will it carry a CE mark?) :P

[JimWebber]

How powerful does the laser have to be to kill 'em?

(and will it carry a CE mark?) :P

 

I can't answer the first question, but the second is definitely yes! Even industrial lasers will have to have some sort of approval, chances are CE marked...

 

EDIT-- As an aside, I can kind of see the logic of a key switch to gain approval marking, but I'd have thought a dead man's handle would be a far more important feature???

 

Jim

[Dave_NA]

I have a 500mW laser in one of my nightclubs and I use it regularly for crowd scans. However you cannot point single beams into the crowd, or anywhere where a person could be. So mirror scans have to finish in dead ground and you have to ensure they never go anywhere that a crowd or staff member could inadvertantly walk into.

 

The one thing I do have is a safety cut-off right next to my control keyboard. This is purely an inline switch between the main power supply and my laser. If its pressed it needs a key to bring the button back up. If anything happens with the laser I can just hit the button and the control PC stays on, but the laser loses power instantly.

 

Its a DPSS laser so only needs a 13amp power supply, I don't think I would do this with other styles of laser systems, but its perfectly acceptable for mine and the local council were happy.

[laserman]

What Nightclub do you work in Dave nA?

 

I try and make a decent living out of laser displays, safe laser displays, and because of people who audience scan without doing any radiation calculations who can put in a lower price are making a mess of the industry. Soon some one will get seriously hurt and there will be a big no no on audience scanning by the authorities that will mess up everything for all the pro's.

 

All Damage to the retina is permanent!

 

Do you think that "if anything happens" you could press the EM stop next to your keyboard in less than 0.25 seconds? Otherwise you might just permanantly damage someones eye sight.

 

Nice one

 

Moderation: This post has been edited by the moderators as it contained angry material directly aimed at another Blue Room member. Please remember that the terms and conditions of this site require us all to treat all other members with respect.

[Dmills]

Small CW DPSS (like the OPs 30mW) are IMHO not too much of a problem, for one thing the beam divergence tends to be crap, and they are normally a fairly high order mode, so your chances of coupling sufficient 532nm energy into a spot on the retina are tiny.

One thing to watch however is the fact that some cheap dpss have an output that has a LOT of 1064nm IR leakage (this usefully increases the reading on a simple power meter), but the eye does not have an aversion response to this IR, and it is not considered an 'eye safe' wavelength.

 

On the subject of alleged 'professionals' a crowd I was in was audience scanned by a rather large Q-SWITCHED doubled yag (~10Kw peak, 30W or so average) , and I have seen (And put a stop to) audience scanning with copper bromide lasers (multi KW peak, a few watts average). These clowns I would worry about, not a penny ante CW green job.

 

To the OP, do grab a copy of the HSEs HS(g) 95 note which discusses some of the issues.

 

Regards, Dan.

[jfitzpat]

One thing to watch however is the fact that some cheap dpss have an output that has a LOT of 1064nm IR leakage (this usefully increases the reading on a simple power meter), but the eye does not have an aversion response to this IR, and it is not considered an 'eye safe' wavelength.

 

I've brought this up a number of times as well. The problem seems especially prevelant with some of the Chinese import gear. 1064nm is essentially UV and can cause corneal damage as well (much like an unfiltered metal halide lamp).

 

-jjf

[merlin24]

How powerful does the laser have to be to kill 'em?

 

Some of the bigger YAGs and the likes of Copper Vapour Lasers will do some very neat amputation if used at close range.

Something as small as a Laser pointer/pen can do serious and irrepairable damage to the human retina if it enters the eye at exactly the right angle, and in one case I do know of cause blindness. Hence the reason that that the little gimick laser pen toys were modified and the sale of controlled. It would be very hard to put a beam into somebodies eye at that angle on purpose however by accident is a whole different ballgame. Mirror balls for example it looks pretty but unless used with proper control measures incredibly stupid.

Having spent a good few years working with large frame entertainment lasers my advise would be:

When it comes to laser effects if you are not sure don't it isn't worth the risk... WHen it comes to Audience scanning if you are allowed to do it always remember the effect must be a moving effect ie the galvos (scanning heads) creating an image as well as the image actually moving across the audience. Always remember that unless you are using a very high quality set of scanning heads in every image there is very likely a primary beam (the start and end point of the image) This cannot go into the audience.

 

Andy

[Dmills]

1064nm is essentially UV and can cause corneal damage as well (much like an unfiltered metal halide lamp).

 

I think you mean Infra Red not Ultra Violet (other end of the visible spectrum)!

 

Regards, Dan.

[jfitzpat]

I think you mean Infra Red not Ultra Violet (other end of the visible spectrum)!

Regards, Dan.

 

Oooops! My typo. You are correct.

 

For the uninitiated (who I have now confused even more), an Nd:YAG laser in display applications is normally pumped at 1064nm, then a birefringent crystal is placed at the proper angle for "freqency doubling" (I think that the technical term is 'second harmonic generation', but in any event, 1064 becomes 532). I'm not sure what is normally used in better quality lasers for the crystal (probably KDP or KTP), but the crystals in some imports are crummy, and no downstream filtering is used. That's were the unwanted 1064 comes from. As Dmills noted, it is basically Infrared, which is why simple laser power meters (which essentially measure heat) are fooled.

 

The point I was trying to make (my two letter typo notwithstanding) is that unlike the bright spot burnout normally associated with lasers and the retina, bright 1064 EMR can cause signifant damage to other tissue layers in your eye and, as Dmills noted, you'll never blink (and will almost certainly not notice the damage until well after the fact).

 

I think that the reason I had a brain fart is that I was thinking of metal hallide lamp injuries as an example and without proper shielding they present IR, UV, and point source hazards. But whatever the reason, I'm sorry.

 

-jjf

[JimWebber]

For the uninitiated (who I have now confused even more), an Nd:YAG laser in display applications is normally pumped at 1064nm, then a birefringent crystal is placed at the proper angle for "freqency doubling" (I think that the technical term is 'second harmonic generation', but in any event, 1064 becomes 532). I'm not sure what is normally used in better quality lasers for the crystal (probably KDP or KTP), but the crystals in some imports are crummy, and no downstream filtering is used. That's were the unwanted 1064 comes from. As Dmills noted, it is basically Infrared, which is why simple laser power meters (which essentially measure heat) are fooled.

 

I'm Interested here, I understand what you are saying, the laser generates light at 1064nm and by using a crystal actually emits the harmonic of this at 532nm.

 

However, I was under the impression that harmonics sat "On top" of the fundamental frequency (in this case 1/1064nm) Does this not mean that the actual light oputput is 1064nm AND the 532nm that we are actually interested in? - In fact the IR component will be somewhat higher, as it is the fundemental?

 

Or am I spectacularly wrong?

 

Just thought about it, as I guess that the IR component isn't a huge problem, as long as there is visible light along with it to initiate the blink response?

 

Jim

 

Jim

[musht]

Big YAG lasers generate a 1064 fundamental but diode pumped lasers have an additional step using a diode at 808 nM which is still IR, theres also a lot of it, a typical 5mW green pointer will use 200mW of 808nM to generate 5mW of 532nM.

 

http://greyghost.dyndns.org/repairfaq/sam/l54-101.gif

 

http://www.laserfaq.org/sam/lptrcmp1.gif

 

JJF be able to explain non linear optics better, personally with Arthur C Clarke on this one ` any sufficiently advanced technology is indistinguishable from magic`

 

Usually the 1064 and 808 will be filtered out at the output coupler, excuse have heard used, is that as >5mW steps into class 3B shouldn`t be looking into beam anyway so no need for an IR filter, hey decent dichroic coatings cost money

 

IR diverges more than the 532 green so the IR is spilling out wider than the visible beam, risk is spread wider than is visible.