Couple questions before I buy my first green laser...

Hi, I'm new to the forum and was wondering if you guys could help me out with a couple questions before I purchase a green laser. I've been reading the stickied threads and stuff to try to get some basic knowledge, but I still need some help.

First, what do you recommend for power? I'm looking for something that will have a visible beam in the night sky and won't be dangerous unless purposely used to inflict damage. From what I've read, 5mW seems to be visible at night and does not pose a risk to anyone's vision unless purposely used to try to harm someone.

Next, how dangerous is the IR radiation emitted by a 5mW laser? I'm interested in purchasing the "True Green 5mW Laser" from DealExtreme, and they warn that it does not include an IR filter. I was reading about how to add IR filters to lasers that do not have them, but I don't think this is something I'd be able to do.

Finally, has anyone dealt with DealExtreme before (particularly with this specific laser)? I've heard some mixed things about them. They warn about "EMS shipping" if the country it's being shipped to does not allow green lasers, will this be an issue for the US? It's my understanding that a 5mW laser is Class IIIa and legal in the US. I've seen "Wicked Lasers Core" 5mW green lasers on eBay for $22 more, would you recommend going with that or sticking with the DealExtreme laser?


Any help would be really appreciated, thanks in advance.

Personally, from what I've heard (I personally do not own and have not used any green lasers) DX is a grab-bag, you might get a good one or you might now. concensus is that they are very easy to break though, so unless you're gonna be very careful you'll probably be better off with the WL, as those tend to be constructed better (again all based on what Iv'e heard, I have _NO_ experiance with greenies)

I've been told that for astronemy 15mw is reccomended. However, again no personal experiance. 5mw is considered safe to use around people, though because it shouldn't cause instant, permanenet, eye-damage.

IF your laser is 5mw or less you shouldn't have a problem in the USA (UK 1mw or less) it's the high-pwoered lasers that are a problem. though this is not a garunte that your laser will get through, a customs agent might see 'green laser' and confiscate it anyway, always a possibility.

I found this website that explains a little: http://www.bfglasers.com/howtoshop.html

It is important to note however, that many people question the validity of claims that IR radiation from a green laser can cause eye damage. Instead of relying on word of mouth, mainly from people who are uneducated, self-proclaimed laser "experts" who are actually just kids playing with lasers, I decided to look up primary literature in optometry and opthalmology to find real cases of such damage or research evidence to support these claims. Nothing. There has been absolutely no research on eye damage from chromic IR radiation exposure from green laser pointers. Which makes me wonder where this claim originated from. Whether it is true, or a marketing gimmick, I don't know. But I do know there's little to no scientific evidence to back these claims.

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The website has bits of information and I would stay away from that laser.

I have a red LASER from DX, and frankly, it's amazing. The build quality, and the brightness of the output is remarkable, especially for the price. I use it in a class that I teach.

Now, green LASERs are a bit different. Here's the lowdown.

Assume for a moment that it doesn't have an IR filter. (Many on this forum report that they actually do have filters, but that DX says they don't, just to cover themselves) The way a green LASER works is that a comparatively high powered IR LASER is in the back of the works, and the beam is passed through some crystals. These crystals get excited by the beam and rebroadcast the energy (each time with losses) until it comes out green.

Of course, no optical system is perfect...so some of the IR will get through, too.

Since a lens is used to collimate the beam, and IR focuses at a different distance than visible light, the IR is not collimated into a beam. It comes out, and diverges...much like a flashlight. Consequently, it gets weaker, the further it goes.

Several people on this forum have measured the IR...some find it negligible, some find it completely absent. But, almost all agree that, at distances more than ~1 foot from the exit aperture, the IR present is not capable of doing damage. One person measured the IR output from an unfiltered DX 50mw LASER (the thread is below) and it was 0.72mw. Yes, less than 1mw.

The true danger from IR is not the power levels, but the fact that it is invisible. It could shine into our eyes for extended periods of time, and we wouldn't realize it...that's the real danger.

-- Chuck Knight