Diffraction gratings

Blue Laser Lamp- with passive cooling technology by Richard Redpath ? Kickstarter

So dumb question for you all, if a laser is over 5mw and using a diffraction grating, is it still unsafe for your eyes, without goggles? Would beam expanders work the same way, or would it matter, since the light output is still the same, just not as focused?

All depends. What powers are you talking about? I use my 100mW 532nm laser with a diffraction grating and don't wear goggles. If a beam strikes my face I move it slightly. But the thing you have to understand is that most of the power goes into the beams that come out in an angle similar to the original beam. So the closer the resulting beam is to perpendicular with the original beam, the less power it will have. Don't let something go into your eye and just leave it there, but don't be too scared.

I wouldn't be so nonchalant with higher powers however. Anything over 500mW and I keep goggles on until I know I am in a safe gap between beams.

As for beam expanders I would say just don't look into it. It is still a powerful beam, and you have to realize that your eye is a lens and that your retina is the focal spot of that lens. So if you send a beam with a lot of power but a larger diameter into your eye, it will be focused to a pinprick on your retina and then you will be SOL with permanent eye damage most likely.

Stay safe and keep lasing!
Isaac

The center one will be the highest- all the other will meter lower-
I use the small 'twinkle RG lasers- w/o fear of any danger-

simple math tell you that each beam from the grating will only be average of the total output divided by the number of images- so even one with 30mW of 532 & 80 mW of 650 will, after the grating, be too low to read on most meters.. and it constantly moving... as are the people and only if you are silly enough to look directly into the beam would you be in any danger-- these little laser PJ are very nice in corners- you see both walls and the ceiling being hit so the three angles are all different.

With lots of fog they are impressive for something that lately can be gotten for around 20usd.