Safe bright green fatbeam w/TTL recommendation for writing on buildings

[maxcady]

thanks so much for all your help so far.

this is quite frustrating, i must say that after reading the flood of responses over the weekend i fell into a depression. I've been doing this for years with my friend who builds the devices, and i was under the impression i was working with a laserist like someone you'd find on this forum. he would always make it very clear to me that he was giving me something that would be safe within the limits and boundaries that i'd explain to him how i'd want to be using it when i got it. you can see how horrible it was for me to see everyones responses here, i felt like the past few years had been a total waste and i went about everything wrong, it crushed me because i thought i was being careful and doing everything right by working with an expert.

you've made it quite clear that i'm not up to snuff on measurements and safety precautions. but let me take this moment to point out that i've been as safe as i can possibly be at all times, theres always a mask around my projector so that if the galvos broke the beam wouldnt go where it shouldnt, it's hitting a wall far away, with people behind the projector, or far to the side, or way below if its on the side of a building. the laser is always covered with a black card until the XY modulation is turned on, the laser is always moving at audiorates pushed to the max the 40k galvos can handle, the galvo mirrors are much smaller than the fatbeam of the laser, all this was from my builder friend who said if i stuck to these guidelines it should be ok. this was a prototype system he threw together to keep me busy and experimenting with my lasershows while my larger ILDA laser is finished being built. i'm quite new to the computer controlled ILDA thing, i've never used one, but my friend has told me that the pangolin system he will be giving me prevents the beam from ever being slow enough or bright enough to damage ones eyes, he said that the software and the showcard inside my ILDA system are designed to work together to prevent anything dangerous from being output. the analog galvo system i've been experimenting and learning on was always meant to be a stepping stone for me to tide me over while i waited for my legit ILDA order to come in. it's been mainly a bedroom practicing/recording system, occasionally i've taken it to a venue with a large curtain, and people appropriately backed off, and quite recently, i did the side of a building using a red laser that i was told was as safe as a "legal" pen laser with a fatbeam lens over it for further safety. the red laser was barely visible on the building, it was not very impressive, it looked super weak, but it looked fabulous in digital photos. i know this is all bullshit because i dont have a power meter, but i guess i'm just trying to save some dignity here, as i can see how on the other side of things i can appear to be a complete idiot with no concept of laser safety, willy nilly waving around a 350mw blue laser and putting random pedestrians in danger. i assure you this is not the case, and causing damage using lasers is something i never want to be involved with. i will take your advice and stop using this stuff in public until the power is properly measured and i report back here, or talk with a laser expert in person.

i guess in the interim i'd like feedback on this post explaining my practice up until i joined the forum, i want to make sure everyone doesnt think im a complete dangerous idiot. i really appreciate the help i've found on this forum so far and i really look forward to sharing my future endeavors and getting all your feedback =]

is there any laser power meter that someone can recommend that i buy? i dont know how to go about purchasing one. or should i just contact x-laser with that query?

this is also frustrating because months ago i emailed x-laser basically explaining everything i was doing, i was excited to see that they were relatively close to my home, and i wanted to drop by to introduce myself and say hello, but they never emailed back. the only emails i got back from them were offers for super expensive laser projectors, it bummed me out. but maybe i didnt send to the right address, does anyone have a contact at x-laser i could email? or does anyone know the right email for them?

all this being said, i still think a totally safe legal green laser would work for the building i want to project on, since green is easier to see than red. arent there some lasers that are totally safe and reliable made by a non-shady company that someone could recommend that i purchase? i dont see what the problem would be if i was using a totally legal safe low power green laser, with a mask around projector, elevated platform for projector, caution tape, sandbags, and the projection going onto a section of building with no windows anywhere in sight, and way high above everyones heads.

[JStewart]

Don't be too downbeat. If you are willing to learn to do things right, there has been in this thread, and is a wealth of information on this forum that will steer you in the right direction. A much worse approach would be adopt the attitude that "my mate says it's ok, so he must be right; because he knows lasers".

I've suggested a couple of different low-cost laser power meters on my earlier post. But you will also need to learn how to use them, as it's very easy to use one of these devices incorrectly to give meaningless readings that sound safe. (and I've seen people, some on some quite high profile installs, making mistakes on how a simple power meter is used).

"Fatbeam" is not a technology that automatically makes lasers safe to view. It was a marketing term used by some manufacturers several years ago to legitimately supply 10mW and 20mW lasers to a market in the US, without a variance being required, which otherwise limited the output to less than 5mW. (the way they achieved this was to expand the higher power beam so that less than 5mW could pass through the product classification aperture - clearly doing this with an original beam of 10mW or so makes this more achievable than trying to start with a 150mW beam, and expanding it so only 5mW passes through the same aperture).

As good as Pangolin's software is, and there are lots of features in the software that can make effects safer, it doesn't automatically prevent high exposure effects from being emitted. For that you need to looking at another additional tool that Pangolin produce called PASS. But even PASS has to be set up correctly, initially, and used within the acceptable parameters.

As others have suggested, as you are so close to X Laser, why not try seeing if you can arrange a visit to them, and they may be able to help.

James

[White-Light]

Although all the posts above offer some absolutely excellent correct advice. You shouldn't be too downhearted as I do feel that perhaps you've been unintentionally frightened to an extent in so far that you've been hit with the full on (albeit abbreviated) version of the detail needed to start to safely consider audience scanning (there is much more knowledge needed to actually do it). The good news that perhaps isn't clear from all the jumble of posts is:

1. If you do NOT audience scan

2. and you take the necessary precautions to ensure your beams can NEVER accidentally enter an audience area eg physical masking etc

3. and provided you follow the ILDA guidelines for overhead scanning as set out above, ie. scan at a minimum of 3 metres height and 2.5 metres laterally away from any balconies or locations to the side where audience or accidental viewers could stand / be located,

4. and have an emergency stop fitted to the projector

5. and ensure your projection wall / area has no highly reflective surfaces eg. polished metals, mirrors, glass, highly gloss surfaces / paint finishes etc, and that there are no other reflective objects in the beam path to the wall eg light fittings, mirror balls etc,

6. and use a Continuous Wave (CW) laser projector whilst doing the above, then the whole measurement requirement goes away unless you're using very very high powers of a level likely to cause issues with spectral reflection - highly unlikely at most people's budgets.

7. It goes without saying you need insurance and such variances / licences, and approvals as are required locally to legally carry out your OVERHEAD show within state / national laws. You may also need FAA approval for outdoor locations.

However, under the above circumstances you can use a narrow beam laser of several hundred milliwatts or even watts of power provided it is CW (continuous wave). The key is keeping your beams away from causing direct exposure to your audience whether that be from a direct hit or reflection and at the safe regulated distances away from them at all times or prevent any other exposure possibilities eg people climbing on others shoulders, swinging out from balconies, projector accidents etc. (Hence the ILDA minimum distance regulations and the masking requirements).

The problems start once you want to audience scan, or if there are reflective surfaces or if you cannot meet the minimum height / distance requirements. Then the whole power measurement / calculation / lens / software / MPE knowledge / BAM / audience scanning specific variance requirements start to kick in.

BTW, just for the record, it's very difficult to legally audience scan in the US anyway with a device of Class 3 or 4. You need a special audience scanning variance that can be hard to get unless you are very experienced and can prove a high level of knowledge and safety. The only other way it can be done, is if you're exempt in a state that allows exemptions because you're using an APPROVED varianced laser below 5mw or an APPROVED varianced fat beam device (which although it may have a power level over 5mw (typically 15-30mw) internally, will have a power density below safe audience scanning levels at the manufacturers stated minimum mounting distance from the audience - the latter is the key and the difference between potentially safe and unsafe fat beam devices). I haven't actually heard of any approved fat beam devices being produced for several years now. ADJ used to make them but I think they fell out of fashion as the fat beams can look rather soft.

Also, I'm sure the US guys will chip in once more, but for any public performance, overhead or otherwise, your projector itself must be varianced. So the obvious question here, is does your friend build to an FDA approved design that he previously submitted for approval (each individual projector design needs to be registered), and that carries a registered ascension number that can be searched on the Federal Database? If the answer is no, I'm pretty sure his projectors aren't legal for public performance in the US in any event.

Several of the people above are absolute experts on audience exposure, in case you haven't gathered so if keeping your audience safe whilst legally scanning is your thing, then you've come to the right place.

[frostypaw]

I think you've done a lot in terms of safety, you've just had bad advice from one person who may themselves just be passing on bad advice they've got - when you've got your head around it you'll find it hair-raising that they'll casually sell the lasers they do.

You clearly do care about it and have taken lots of steps to keep it safe but over-optimistic reassurances from someone else have thrown you off kilter a bit, that you're so bothered about it will endear you here I think. What you're describing doesn't sound intrinsically unsafe to me, but the assumption that a stray strike would be 'ok' isn't sound - but that doesn't mean you've not already eliminated that chance down to near zero

[mixedgas]

Maxcady,

I just called the CEO of X-laser and left a message. My bet is I get a reply. I'll email him too. In business to business communications, starting with an email is often the worse thing you can do. I've found that hearing a human voice usually results in action, whereas it can often take months for a person to reply to my emails for the first time.
~
So PM me with your contact info and I'll message him with it. We'll see, but his showroom is open daily. He's the closest. The other power meter possibilities off the top of my head are in Philly and Baltimore... And there are always laser researchers at local universities.
~
Now for the good news. You tried to be safe. At 6:30 am this morning when the lead of a division of a certain Federal agency over in Rockville read your reply, I bet he smiled. Not that I have contacted him on the matter at all, nor would I if you keep heading toward the path of safety, but I know they read PL and LPF once in a while. FDA's attitude has always been its better to co-operate to improve safety then to run around citing and fining people. I just happen to know that he goes into his office at like 4:30 in the morning to avoid traffic..
~
I also smiled, because you came back and asked how to fix things. It will take time, but the cost of being legal usually adds less then 100$ to the cost of a projector.
The required permits are FREE, there is no fee. As others have said, making things safe will get you friends here.
~
Contrast that to video I have see from Arizona, of a certain repeat offender who's so called "shows" regularly damage cell phone cameras held into his beams. He showed up to a gig last week rumored to be drunk and high on Mary Jane, and his BIG corporate client had venue security kick him out. Thy shalt not show up to a gig intoxicated, steal food from the kitchen without asking, improperly dressed, use foul language, and fall asleep on a road case. Worse yet his permits were already publically revoked, after being given more then one chance to become legal again by changing his ways. Yet he still booked this show. He has been known to "allegedly" aim 5 watts point blank into the audience. He's been told he's wrong, and dangerous, in writing, by the Feds.. Many professional people from PL tried to help him to understand, including meeting him in person multiple times.
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You tried to be safe, contrast yourself to the above person. Kudos for that. Willing safety compliance while trying to improve the quality of your shows will ALWAYs make you friends here.
~

So, to reduce your guilt, there is a safety factor built into the MPE numbers, and a eye strike just above MPE will not ALWAYS result in damage. IF your Green beam divergence was actually 4.5 mR, at 10x MPE, and 50 mW, your Green NOHD drops to ~ 12 feet. There is a study in process that alleges 10X MPE is actually statistically quite safe, and that the safety factor built into the MPE is perhaps more then 10. However we can't depend on that, it's not totally accepted science. But since tracing a circle on a piece of paper in an emergency is not the way to do things, the only way to know is to make measurements. At 10x MPE, its not so good in the blue. That is still a very long distance.
~
There are a huge array of factors and variables that come into this, and if, as you state, your beams are always moving, that helps. IF the movement is slow enough but not too slow, and preferably its in both the X and Y axis. Repeat scanning across the eyes again and again in the same high speed pattern does not always reduce exposure, in fact can add to it. Hence you have to do the math for each effect and scan speed.
~

It will take some time, but let's get you legal. I think you are infested with the laser bug and want to do this right. Right now I am a full time employee and a master's student in the evenings, so it will take a while help you via posts from PL and email, but we'll get there if you try and wish to continue. I'll be glad to help you complete that paperwork for a variance that does not allow audience scanning.
~
Its a bit far off into the future, but since your close, you should attend at least a weekend of SELEM.
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I'm going top reach out to some folks and try to find a LPM near you. I just sent the PM to start that process. Networking is a good thing.
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Divergence is generally measured for a "Gaussian" laser beam by finding the 13 and 82% power points, or the 90-10 power points, depending on which set of physics rules your following. Anyways you have to scan the beam across a photo sensor, find the peak, and find two points on the slope of the curved beam shape. We tend to cheat on PL and LPF and make an approximation using just a measuring tool such as a ruler and micrometer, after burning a piece of paper, or exposing a piece of holographic film. That makes professionals like me cringe, but better to try and know something, then to just assume. Not all beams used in show systems are Gaussian, some lasers have another profile we call "TOP HAT" or Extreme Multimode, and that is a factor when you do the math.
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Laser manufacturers use the 1/E^2 definition of beam diameter, and laser safety uses 1/E, so it gets even more confusing. Basically your finding the diameter of the beam that contains 90% of the energy.
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7 mm is the accepted average diameter of a dark adapted eye pupil, so the math is adapted to show how much energy goes into eye at that point.

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So there are some other ways to try and do this without math, one of which is highly accepted overseas, but is outside the scope of this post. It still needs a sensitive, accurate power meter and a limiting aperture. So until you have that training and the proper permit, its best to have the beam be 3 meters up and 2.5 meters horizontal from any audience accessible point.
~

I'm weary of posting audience scanning equations anymore. Some times folks include them in Phone Applications and distribute them without including all the rules and conditions to make them valid. Or they end up in Google Images, etc. But I said I would post this for Maxcady to be able to understand, so here goes...





Steve

[DanG]

Hi all,

I thought I would shorten the train of communication and just post here having gotten Steve's VM.

@maxcady, drop me an email please to dan at our domain dot com (I don't want to post the full address so bots don't scrape it off and spam the crap out of me) and I'll see what I can do for you. We respond to every contact we get and keep track of them in our CRM system so I would also like to know how that ball got dropped.

I do want to tell you that most of the replies here have been concerned with technical safety, and we have to be concerned with regulatory compliance above technical safety so I think the chances of you leaving with a clear path to certifying this projector for audience scanning is next to zero because it is far more involved than simply reaching MPE. However, I am happy to meter the system for you and give you some next steps to consider.

I really applaud your desire to be safe and having read this thread I think you have gotten some much better advice here than you got from your engineer. This is one of the biggest reasons that we continue to support PL financially every month - there are just so few resources for people to get reasonable information and I think that's really important. Thanks all.

Dan

[mixedgas]

Thanks Dan!
PS, if Dan's email bounces, which is unlikely, call X-Laser and get into his voicemail.

Steve

[swamidog]

Thanks Dan!
PS, if Dan's email bounces, which is unlikely, call X-Laser and get into his voicemail.

Steve

x-laser isn't officially open today. snow day + president's day, but adam is in the office manning phones.

[maxcady]

I'm slammed with work but plan on contacting X-Laser very soon, im really excited by all the support shown here. Thanks again.

I currently have a green laser with no TTL, and I still need a green laser with TTL to project a word HIGH above everyones heads onto a blank windowless section of a building. Is there no recommendations? I think if i had one that was totally safe, like legal etc or darn near impossible to hurt someone with, i could do that in a roped off section of the art installation inside the building, or if i had a brighter green ttl laser, i could do it onto the building high above everyones heads, following the rules pointed out in the forum.

** Or I could also try projecting it much smaller on the building exterior, using a green laser thats "party safe." If nobody has any suggestions for a laser (or a few) that I could purchase for this specific purpose for this one time event, I'll just buy some stuff on amazon that says it's completely safe, like laser-pointer safe but with TTL control (if such a thing exists?).

Are there any "go-to" or trusted brands or vendors of lasers that are more reliable than others? I'm aware that i need to measure everything myself, and often, due to the specs not actually being accurate, but surely theres more reputable dealers than others right? In making little mounts for the lasers I currently have, I've learned just how shoddy and corner-cutting some of the build on the lasers is, i've had to repair my red and my blue laser twice just cuz the parts weren't that great, my friend fixed them with better parts than they were sold to me with and it cost more than the actual laser, haha, but i needed it fixed asap so i had to do it. my friend told me i should try to source better quality built lasers, but he also told me the reason that mine are not the best build is because lasers are probably expensive and are hard to find in a quality build without spending a lot of money. this was speculation on his part as he worked on the laser and we were chatting..

Thanks again, I will be following up on all the advice here. But in the meantime, if I had a safe green laser with TTL for just recording and practicing shows in my bedroom that would even be a step forward for me, because right now the only TTL lasers I have are a red thats quite dim, and a blue thats scary and i wont use it anymore until i know all the facts about it. and i really want to continue experimenting and recording laser improvisations using TTL rather than soley XY signals.

[DanG]

Hi Maxcady,

Let me see if I can clear something up that was mentioned earlier but I don't think it stuck.

TTL has (almost) NOTHING to do with the safety of a laser. In general, if you were going to choose a laser that could be safer you would NOT want TTL.

TTL only means that the diodes are at full power, or zero power. There is no 50% power. When you have a TTL laser the beam is either on or off. That's all it means.

The opposite of TTL is analog which means that the diodes can dim so you could reduce the power to say 30% which would make it generally safer.

You can put either a TTL or analog laser into an XY scanning system, or you can have them in a single beam pointer arrangement. Again, this has nothing to do with whether the beam is eye-safe or not.

Secondly, there is no such thing as "party safe." Whomever you have learned these things from is absolutely wrong. I don't mean to be rude at all, but you are talking about matters of safety in a way that is completely incorrect and I simply want to make sure you have the right information.

No laser with a useable amount of power for your application is 'completely safe.' Lasers that are 5mW of power or less are classified as 'low risk' products that are often used in small parties and such and they are generally believed to be reasonably safe, but they are not technically eye safe. Anything above that used for public displays requires a product report, variance, and some reasonable experience to use.

I hope this helps a little as you begin to work these things out. Buying lasers on Amazon is not usually the best way to go as many (but not all) of them are not legal in the US and are improperly imported from Asia. I will let other folks chime in here with suggestions beyond that.