New to lasers and need some safety advice

[slc79]

When searching for various information on lasers, this forum popped up and it seems to have a lot of experienced people so I decided to try asking a few questions here

Long story short, I'm one of those who were always fascinated by Jarre's laser harp and have been wanting to play one for many many years. Now I've decided that the time has come, so I'm starting to pick up parts occasionally to build one. It will be based on an Arduino and using a galvanometer with mirror plate for scanning the laser beam. But, I do also have a lot of respect for lasers, as I know they can do a lot of harm. Based on other people's experience I will be needing a green laser around 400mW (Will be using a very low powered one while building and testing the rig).

So, to my questions:

1. I know that cheap china lasers will emit IR radiation. Will I have to take other measures to protect myself from the IR radiation, or will the IR radiation always follow the green beam which I will have to make sure to stay clear of anyway?

2. I'd definitely feel safer with protective glasses, and I was also encouraged by the national radiation protection agency to have them when dealing with this kind of lasers, but are there glasses which will help protecting me from both the green beam and the IR radiation at the same time and can be bought in the $50-$100 range?

3. If I decide to try some lower cost glasses, is there a way I can actually test them to see if they will be doing the job with the laser of my choice?

Any other generic safety tips would also be greatly appreciated. I am aware that one cannot put a cost on health and in a perfect world, one would gladly pay up for whatever the cost of the protective gear, but sadly I don't have an endless pit of money, so I need to try reducing the risks without spending too much, and when I feel I have learned enough I will eventually decide whether or not to finish my project.

 

[H2Oxide]

First, off, welcome to the forum! Second, +REP for asking about safety first.

As for your questions:

1. Only DPSS lasers emit IR radiation. For diode lasers, which are most blue and red lasers, this shouldn't be a problem. There are green diode lasers, but the much more common green 532nm lasers are DPSS (I think Jarre's harp used 532nm, since they have a high brightness to power ratio). If you go with 532nm lasers, then the IR will follow the path of the beam, but it won't stay within it. It will spread out in a conical shape from the aperture, so if you use unfiltered lasers keep this in mind (especially if you're going to be standing above them). Fortunately, you can pick up small IR filters for like $2 on eBay, which should block out enough of the IR to make them safe. If you just don't want to deal with the hassle, there are 520nm diode lasers, which are also green. They are a bit bluer and not as bright as the 532nm lasers, but they're also smaller and less finicky.

2. Yes. At 400mW, these should be more than enough to take care of all your concerns. They come highly recommended.
When working with this kind of power, goggles are not just a suggestion, but a requirement.

3. Not really without a power meter.

As for general tips, 400mW is nothing to scoff at. Make sure that the beam terminates on something that can withstand continuous high-intensity radiation, and something that prevents scattering. I've found that dark-colored stones and ceramics (NOT GLAZED!) are good for this.

 

[slc79]

First of all, thanks for the response. I knew it was a good idea to ask, because what you said about the 532nm diodes casting a cone shaped IR radiation pattern was new to me, and I'm happy to hear that there is an easy fix for this. I would appreciate a detailed description on how to do this (how to mount it, how to absolutely NOT do it etc. )

2. Yes. At 400mW, these should be more than enough to take care of all your concerns. They come highly recommended.
When working with this kind of power, goggles are not just a suggestion, but a requirement.

I was looking at that brand, so happy to hear that I can use them as it seems affordable.

As for general tips, 400mW is nothing to scoff at. Make sure that the beam terminates on something that can withstand continuous high-intensity radiation, and something that prevents scattering. I've found that dark-colored stones and ceramics (NOT GLAZED!) are good for this.

Since the laser will be split into 5-10 beams at any time, and in addition will be shut off between the movements done by the galvanometer, the resulting beams will be much less than 400mW, so I'm left under the impression that this won't be a particularly big issue. I've also seen others who built these things with the same strength of the laser that I am considering playing them in their living rooms without any additional measures taken. The part I worry more about is the development/adjustment phase of it, as in where things are more likely to go wrong

Before posting here, I was starting to wonder if this might not be such a good idea after all, but your post really helped out in making a proper risk assessment. But if resolving the IR radiation issue, does that mean even these glasses would be good enough too? : Eagle Pair® 190-540nm Standard Laser Safety Goggles

 

[Encap]

First of all, thanks for the response. I knew it was a good idea to ask, because what you said about the 532nm diodes casting a cone shaped IR radiation pattern was new to me, and I'm happy to hear that there is an easy fix for this. I would appreciate a detailed description on how to do this (how to mount it, how to absolutely NOT do it etc. )



I was looking at that brand, so happy to hear that I can use them as it seems affordable.




Since the laser will be split into 5-10 beams at any time, and in addition will be shut off between the movements done by the galvanometer, the resulting beams will be much less than 400mW, so I'm left under the impression that this won't be a particularly big issue. I've also seen others who built these things with the same strength of the laser that I am considering playing them in their living rooms without any additional measures taken. The part I worry more about is the development/adjustment phase of it, as in where things are more likely to go wrong

Before posting here, I was starting to wonder if this might not be such a good idea after all, but your post really helped out in making a proper risk assessment. But if resolving the IR radiation issue, does that mean even these glasses would be good enough too? : Eagle Pair® 190-540nm Standard Laser Safety Goggles

These block 190nm to 540nm and 800nm to 1700nm IR also. They are only a couple of dollars more than the standard goggles and you would be covered for both types of green laser DPSS with or without an IR filter and direct diode green Eagle Pair® 190-540nm & 800-1700nm OD5 Laser Safety Goggles

 

[diachi]

Since the laser will be split into 5-10 beams at any time, and in addition will be shut off between the movements done by the galvanometer, the resulting beams will be much less than 400mW, so I'm left under the impression that this won't be a particularly big issue. I've also seen others who built these things with the same strength of the laser that I am considering playing them in their living rooms without any additional measures taken. The part I worry more about is the development/adjustment phase of it, as in where things are more likely to go wrong

The power is still essentially 400mW, even if you're projecting multiple beams. It's still one beam, you're just seeing it as multiple beams thanks to persistence of vision. You'd be able to see it as one beam if you filmed in slow motion.

You also need to take into account any failure modes. For example, what happens if the galvo stops unexpectedly? I've had that happen before.

 

[slc79]

The power is still essentially 400mW, even if you're projecting multiple beams. It's still one beam, you're just seeing it as multiple beams thanks to persistence of vision. You'd be able to see it as one beam if you filmed in slow motion.

But the fact that the laser would be off between movements, won't that reduce the impact it has on the surface it hits? And same with the fact that it doesn't stay on one place constantly? Would like to add that I'm not questioning your advice, I'm just asking to understand better what I'm getting myself into

You also need to take into account any failure modes. For example, what happens if the galvo stops unexpectedly? I've had that happen before.

That is a good point. Judging from a laser safety chart I saw somewhere, the 0-500mW range for shorter periods shouldn't become that hot if the IR radiation is kept to a minimum, so adding a kill switch in the setup which is easily accessible could possibly be good enough? I am thinking of having an extra control box with a small display for some feedback where I could fit that.

The chart I'm referring to is this one: http://www.lasersafetyfacts.com/resources/Spreadsheet---laser-classes.pdf

 

[CurtisOliver]

Welcome to the forum slc79.
I am also glad to see you thinking of safety. :beer:

As for the on/off with the laser. This is similar to the pulsed mode on some laser pointers. Although not constantly on, over time it can still burn depending on the repetition rate. If enough time is given for the heat to dissipate then no burning will occur. But for our eyes to see multiple beams from one, the laser must be over 60 fps therefore not allowing for much dissipation time.

 

[slc79]

Welcome to the forum slc79.
I am also glad to see you thinking of safety. :beer:

As for the on/off with the laser. This is similar to the pulsed mode on some laser pointers. Although not constantly on, over time it can still burn depending on the repetition rate. If enough time is given for the heat to dissipate then no burning will occur. But for our eyes to see multiple beams from one, the laser must be over 60 fps therefore not allowing for much dissipation time.

I see. But when it comes to actual burn, where does the limits go? And how close do you need to be to the beam for that to be of concern? Based on what you say, it also seems to make sense to have the slowest possible scan rate which makes all beams visible at the same time?

As mentioned, I've seen several videos of people with their own laser harps with lasers at 400mW who hasn't really taken any measures to protect their ceilings. Could I even be successful with 200mW for this purpose? (It needs to be visible without fog, as I cannot use fog machines at home due to the goddamn smoke detectors )

Sorry about flooding you guys with all these questions, but the reasonable part of me keeps telling me that I'm insane for doing this. It's really appreciated though and as I said I'm glad I registered to ask people with actual experience

 

[Vision]

Never stop asking questions.

 

[CurtisOliver]

Asking questions is how you learn.
Anyway, 400mW won't be a huge risk when it comes to burning your ceiling, however the risk of a slight burn after a long duration is still there.
As for scan rate, you need a fast scan rate for the effect to work well. Divergence will effect the power density over a range depending on how high the divergence is.
A 400mW 532nm is pretty bright and the beam will be visible in darker environments, but fog is what brings out the beam to what you would probably expect.

 

[slc79]

Asking questions is how you learn.
Anyway, 400mW won't be a huge risk when it comes to burning your ceiling, however the risk of a slight burn after a long duration is still there.
As for scan rate, you need a fast scan rate for the effect to work well. Divergence will effect the power density over a range depending on how high the divergence is.
A 400mW 532nm is pretty bright and the beam will be visible in darker environments, but fog is what brings out the beam to what you would probably expect.

I know it won't be as impressive without fog as with, but as long as I can actually see the beams I'm OK with it, and I once saw a laser pointer of 250mW lit up quite well.. somewhat hazy beam, but still visible. When you speak of long duration, what is considered long?

I'm also aware of the need for a fast scan rate for this to work well, as I initially considered a stepper motor for the rig until I saw youtube-videos of harps built with one.. did not look good at all, so I went ahead and ordered a galvo-set instead which should be with me in 2-6 weeks, so I still have plenty of time to research before anyhing can be built. Did some preliminary tests of the photo transistors I found and they've got an excellent response time, so I have at least one key part of this in place.

 

[Radim]

Maybe you can get some projector for that - if it is RGB, you can have almost any color of beams you like and what's more - you can add some effects when you touch the beams when playing. And in addition if there are pure diode lasers, you do not need to worry about IR as mentioned above. I would not use cheap 532 nm to be honest - they might be unreliable with power, lifetime and IR leakage. And if you go for higher power quality 532 nm, you can get to hundreds of dollars, where the diode projectors start. With projector you just add some mirror to direct beams and you are ready to go (just you need to get some SW).

 

[BobMc]

Welcome to the forum. As you can tell theirs a lot of knowledge people here more than willing to help. Be safe and enjoy and looking forward to reading some more of your posts. Once again welcome and be safe.

 

[CurtisOliver]

To be honest, you probably will not have a problem with the power at all in the sense of burning your ceiling. 400mW is powerful but not extreme. Plus I'm guessing your ceiling is white anyway so most of the beam will be reflected. You will see a 400mW 532's beam, just don't expect too much without any fog. Burning your retinas is the highest concern of all, so laser goggles are a must.

 

[slc79]

Welcome to the forum. As you can tell theirs a lot of knowledge people here more than willing to help. Be safe and enjoy and looking forward to reading some more of your posts. Once again welcome and be safe.

Thank you. Also to all the others who welcomed me, thanks a lot I think it's the first time I've been welcomed like this.

To be honest, you probably will not have a problem with the power at all in the sense of burning your ceiling. 400mW is powerful but not extreme. Plus I'm guessing your ceiling is white anyway so most of the beam will be reflected. You will see a 400mW 532's beam, just don't expect too much without any fog. Burning your retinas is the highest concern of all, so laser goggles are a must.

Right. So my primary concern will then be to get those goggles ordered and fixing an IR filter on whatever laser I end up using if it doesn't already have one, then?

I must say that I already start feeling a bit less freaked out and a bit safer already knowing more about what awaits me. Next step would be to have someone design a circuit for me that can convert the PWM output of the Arduino to true analog I'm lucky enough to know a few electronics people who can help out with that.. I will at least be doing the programming entirely by myself, which is also is the part I'm really looking forward to doing. If/when I get started on the project, I'll happily share the progress with you and maybe even get some more hints and tips along the way.

 

[CurtisOliver]

Yes, the goggles are a priority. Depending on what laser you get, it may already be IR filtered.
I'm no good with electronics myself, but if you need help from anyone on here then there are those that can.
Good luck with your project. Stay safe and have fun. :beer: