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

[maxcady]

Steve,
Can you link some video or images of your set up? You said that you have been doing X Y shows. Can you post some of what you have done? Where are you located? This is not to track you down; you'll do what you want, we know, but there may be someone close that can jump start your system. Do you have a power meter? They do not have to be expensive and we can show you how to find one if you don't.

Man I'd love a power meter. I want all this stuff. I want to be in control and confident in safety, and not reliant on another person every single time I have an idea, that was my goal in joining this forum, and why I'm slowly moving towards computer control of an ILDA laser instead of my current analog galvo system.

I can get some footage of an actual instance where I was using a laser at a public event (let me know if you want that), but right now I only have a video of my oscilloscope going through one of my laser shows that I had to make to send to a rock group: https://www.youtube.com/watch?v=XqdTJ4zZBYM

I appreciate everyones concern, and I'll post the specs here. But let me just say that the galvo system I'm using was designed to be used on a set where it would be aimed directly at the talent, and the laser was carefully chosen for that purpose. I have never gotten a second opinion though, I got the laser from my friend who builds this for me (and other clients) and didn't think twice about it. I assumed he measured it with a meter etc, but you're right, with the Chinese spec drift, it seems most appropriate to measure the laser power myself and make sure its really doing what we assume it would do when we acquired it.

Let me know if you want to see some footage of the laser in action. I can get it, but its not available right this second. I don't know if you just wanna see a laser show example in any form, or if you wanted to actually see the gear, or how the laser looked in person.

[maxcady]

TTL is not inherently safer than analogue modulation. with TTL, the beam is either full on or full off. with analogue modulation, the beam can be full on, full off, or any power level in between.

Interesting: my laser says TTL INPUT on it, but the laser can be dimmed. I can send it LFOs and it will dim, or i can send it pulsewave at audiorate frequencies and control dimming with PWM. So does that mean its not a true ttl input and the circuitboard on the power supply is mislabeled?

[maxcady]

Use of a simple metal mask to make sure the light only goes where you want it costs far less then engineering a "FAT " beam.
~[/COLOR]Steve
ILDA Certified LASER SAFETY OFFICER.

Thanks for posting this! About the mask.. I'm not sure what you mean. Do you mean like a non laser light and using a GOBO to make a shape of a logo or something?

- - - Updated - - -

Where are you located? This is not to track you down; you'll do what you want, we know, but there may be someone close that can jump start your system. Do you have a power meter? They do not have to be expensive and we can show you how to find one if you don't.

I'm in the DC/MD/VA area

[maxcady]

SPECS:

Blue fatbeam 350mw
Green fatbeam 50mw

I also found this in my old emails with engineer:

"the fat beam is actually bigger than the galvo mirrors, so you're losing some of the energy of the laser, but it is still fairly bright with a line about 8mm wide at 6' distance. You will lose some resolution in that regard, but it will be a really safe way to project at a venue where people are likely to come into contact with the beam."

and

"I have found sources for fat beam lasers that can be 10-20 more powerful and still maintain safety by spreading the beam out. I will let you know how this looks as soon as I have a chance to try them with galvos and/or diffraction gratings - but I think this will be of interest to you regardless, since you have expressed a desire to have equipment you can take to parties and events without worry."
--

I still haven't found the wavelength of each color but I'll find that (and when I do, I'm labeling my lasers!)

[mixedgas]

350 mW?
50 mW?

What is the beam diameter at the talent?

Steve

[JStewart]

Assuming the 8mm diameter at 6' the math(s!) is quite simple to get a rough approximation. Using 50mW beam means about 40mW can still pass through a 7mm pupil.

Translate that power value to a more common power density value expressed per cm^2, by multiplying by ~2.5. That gets you a figure of ~100mW/cm^2. 2.5mW/cm^2 is the limit for a 0.25s exposure, and 10mW/cm^2 for 1ms. So your 100mW/cm^2 potential exposure would make for some very short exposure durations to remain below the safety limits.

The important factor is power density, not the size of the beam, although the latter can lower the former. The critical question is, does it lower the power density enough to be safe?

The TTL modulation has virtually zero effect on making viewing safer.

With respect, I don't think the person who supplied you with the laser has any idea what they are talking about when it comes to laser safety. Sorry to be frank with you.

But you have come to somewhere where people will give you some good advice and pointers on the subject.

Until you have a better understanding of what the real safety implications are of direct exposure, keep the beams off peoples' faces.

James

[mixedgas]

I was going to wait till I had the diameter numbers, but I'm very much in agreement with Mr. Stewart. I think your "Engineer" needs to show you (and Us) some math and measurements. I think until some one shows you an approved CDRH model report, you are exposing yourself, your clients, and the "talent" to massive liability, and the possibility of an accident. Its not just the possibility of a retinal burn or temporary damage to the retina, but the problem of flash-blinding some one on a elevated stage, resulting in "secondary" hazards, such as falling or tripping. You should discontinue use of these devices.


Steve

[swamidog]

Interesting: my laser says TTL INPUT on it, but the laser can be dimmed. I can send it LFOs and it will dim, or i can send it pulsewave at audiorate frequencies and control dimming with PWM. So does that mean its not a true ttl input and the circuitboard on the power supply is mislabeled?

you're reducing the apparent brightness by changing the duty cycle of the pulse train. it's still TTL.

[planters]

I'm in the DC/MD/VA area

Good, that's a start. We can wait for someone in that area to PM you. If they do, you should take them up on it, really...you'll learn a lot.

You need a power meter. No discussion. No argument. This is the single most important piece of equipment you will use and EVERYTHING else follows from a knowledge of the actual power you are producing. You can calculate divergence with a plastic ruler and paper and pencil. I can ( anyone here can) tell you how to use these to generate energy density/divergence, but you have to have the actual power of your lasers before any of this has meaning. Don't rely on what SOMEONE, some guy, the manufacturer, a partner, a self proclaimed genius said your laser generates...measure it.

What Steve is recommending with the mask is a fail safe. I have been doing this for some time and just about anything that can go wrong will, really it will. The mirrors for almost all the scanners on the market are GLUED in place and guess what, the glue fails. I had a pair of well regarded commercial scanners on a 20W projector system and a scanner threw one of the mirrors into the safety shutter preventing the aperture from closing, so this is a bad event making itself worse. The mask prevented any of the laser light from going where it could be harmful. I love that mask!

I will admit to ignorance as to the term "fat-beam". I don't think you should depend on it. Measure the power, measure the dimensions of the beam and make a decision.

The emails from your engineer are not necessarily right or wrong, but they are of little value here. It is time for you to understand what you are doing and depend less on marketing specs or an engineer who is no longer around.

On a positive note, the capabilities of lasers for projection onto buildings are impressive:

https://www.hb-laser.com/en/referenc...m-germany.html

Some of the members here can and have done this level of work. It isn't beyond you too if you are interested.

[maxcady]

is there a way i could quickly measure the beam diameter and report back to you on this thread without a special tool? i have the green laser with me where i am now.