# New user question re goggles/glasses

#### Paul6ppca

##### Flashlight Enthusiast
I bought a 5mW laser from Amazon to try to spot bouys on my boat at night.
My question after reading many posts is, Do I or others on the boat need any safety glasses?The bouys are reflective and will be over 100 yards away.It is rated as a 5mW but many posts say it can be as high as 70mW and I dont fully understand IR part of the power rating /eye damage.Does focusing make any difference? I intend to make a wide focus for a larger spot to find/identify the bouys.
Thanks for any help.I dont want to injure anyones eyes!

Paul

This one;
http://www.amazon.com/dp/B007IAZJCY/?tag=cpf0b6-20

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#### parabola949

##### Newly Enlightened
Paul - a 5mW red, especially from that distance, is not very threatening.
Calculations:
Safe distance for direct laser viewing (straight at you) - 52ft.
50 / 50 chance of retinal damage: 16ft. (remember, that's pointed directly into the eye, focused)

Basically, bouncing off the bouy 100 yards away, then travelling back (which, the travel back will be more diffused due to the bouy), you are safe at that distance.

I just also noticed the part about it being unfocused.
Let's readjust the calculations to give it a 20 degree angle, or 349 milliradians:
Safe distance: 0.15ft :O
50 / 50 chance of damage: 0.05ft.

I'd say you're pretty safe there.

If you'd like to run more calculations (say, for that 70mW), try this:
http://www.tryptrecords.com/safety.html

#### lazerphase

##### Newly Enlightened
You don't need goggles for any laser that is 5mW or under and the IR is emitted by green laser pointers that use a frequency doubling crystal to send 1064nm IR through it to cut its wavelength in half and produce the desired 532nm green wavelength.