Safe laser power for DIY spirograph, line and galvo scanner?

[Radim]

Yes, these child times were awesome. The red keychain laser pointers were one of the best toys for me. And batts for it cost fortune for me in these times (it took 3 little bats and one costed a little less than 1 USD if I remember well). I'm also surprised I did not get any eye damage - really not wise to give that to children to play with it. I remember once I was in large tee pee and there was a bit of smoke from the fire inside, I played there with that red keychain laser and I was extremely amazed by the beam visibility even that was during the day. And those lenscaps! Various patterns! These were the days I started to read books about science and people like Einstein, Hawking and many others became my close friends and teachers through these books...

Edit: My cousin had as a kid a laser pointer with switch, which brought a little mirror on spring into the beam path, what created kind of patterns you are about to do. Awesome, however these were a bit random according to how the mirror on spring moved.

 

[Skauber]

Yeah, buying that HeNe laser kit was something I really saved up for I remember. Soldered it all together and it ran off AC wall power, so I didn't have to spend on batteries anymore. Pretty dangerous kit when you think of it, had a rectifier and had several big cap/diode voltage doubler circuits in series, think the helium neon laser needed 1kV DC to run according to the manual if I remember correct. Hehe. I've been trying to find some information on that kit I had back then, but haven't been successful yet. I thought it was a Velleman kit, but doesn't seem like they've had a kit like that at all.

Anyway, back on topic. I found some glasses from "LaserPair" which seems to cover wavelengths between 200-1400 nm with OD 1.5+. The wide wavelength protection seems very attractive for me, as I didn't find similar ones from Eagle Pair, and had to order more than one pair of glasses from them. The price seems to suggest that this is more than the typical cheap chinese crap, but is Laser Pair a reputable company? Seems to me it's much much harder to find good laser safety glasses with a ton of pitfalls to run into, than it is to find lasers... Should be the other way around. Hehe.

Glasses on ebay

Laser protective glasses, laser goggles, safety glasses - Photon Technology Co. Ltd. Shenzhen radium

 

[Radim]

Be carefull, these seems to be designed for IPL not for lasers. I've looked for Univet glasses and it does not seem they have something for let's say about 500-700 nm with reasonable use, the closest would be this for example:
UL_1011

But it has extreme OD in red part (you won't see anything), but suitable in green part and VLT only 2 % - they will be very dark.
I would try to ask some laser safety stuff seller for recommendations, if you have special request like this.

Or these:
UL_1012

VLT 4 %, but otherwise still the same issues as those above.

I did not notice any suitable in their alignment, glass and interferential models. Sorry about my earlier post. At least you know what to ask...

Edit: Quick overview list.

 

[Skauber]

What is the difference between IPL and laser glasses?

From what I read, green lasers emit IR, so for green you need to have glasses that protect against both green and IR wavelengths, green 532nm + IR 808 nm. In addition the red laser is at 650 nm. Seems to be really hard to find glasses which covers these three wavelengths without spending a lot of money. Not that my eyes have a price, but would be nice if there were some "good enough" glasses for lasers below 15 mW in hobby use, seems a bit overkill to get glasses which are intended to protect against high powered lasers in this case.

Almost makes me want to get protection glasses for sun gazing.. LOL

 

[Radim]

Intense pulsed light is not coherent and not as monochromatic as laser - see here for more. I'm not an expert for those materials filters are made of, but I would not bet on using IPL glasses instead of appropriate laser glasses.

And you can use 520 nm diode for green instead - there is no IR, however the beam specs are not as good as with 532 nm. Only if you use 532 nm for green, there is IR at 808 nm from pump diode and 1064 nm from the Nd dopped crystal (actual laser, which is frequency doubled to get 532 nm output). If you go for higher quality laser, it is supposed to be IR filtered. Or you can get separate suitable IR filter for 808 nm and 1064 nm and mount it on 532 nm module output -> no need for glasses to cover it.

Edit: If you did a search here already with no results, what about asking this specific question in separate thread? Named like: "Laser safety glasses for green-red specrtum?" As we are the only two discussing here I think it will be more effective to bring out this particular question to wider part of the LPF community. A lot of much more experienced members than me are here, but maybe they are just not reading this thread. You may even link this thread to initiate the purpose of your project.

 

[Skauber]

Good idea! I guess I'll make a thread for glasses in the safety section.

As for 520nm, seems they are not available in low power (10 mW), and are quite a bit more expensive. Might see if I find a good IR filter to mount on the laser module instead for this purpose. Are there any rule of thumb on how much IR power a green 532 nm laser will emit? Like 20% of rated output or something along those lines?

The green laser I have ordered does have housing and some sort of lens on the output, as it's a focusable laser, but no idea if it has any type of IR filtering built in.. Perhaps I could contact the seller and ask, but not always the sellers know what they're talking about...

 

[Radim]

That is true with 520 nm. If you get good IR filtered laser the IR at these powers would be IMO negligible. In higher power in orders of hundreds mW I noticed the IR was like 1 mW in some review (sorry I do not remember source). However this IR especially from IR pump diode would be not nearly as colimated as output beam, therefore this fact should make it even more safe. But only if it is a good IR filter, the total IR inside is much more then output power, if you consider efficiency of the process, than significant amount of IR may leak without filter (in some cheap greenies I noticed it was more IR laser than 532 nm - again I do not remember the source, it is a long time).

 

[Skauber]

In other words, if I buy a cheap 532 nm 10mW laser, it might give ~10mW of 532nm green laser, but might be more in the IR spectrum? The one I ordered is a focusable 10 mW one, it was a kit with holder and adapter at 31.59 usd - see this link. I'm gonna assume 10 of those dollars goes to the adapter and holder accessories, so around 20 bucks for the laser itself. I'm gonna assume this has no IR filtering, so I'm gonna add that to be sure.

Here's one filter I might consider: 1pc IR Filter Glass Lens/High 532nm Laser Transmittance 9.5x9.5x1.1mm | eBay