Just pointing it at walls, no mirrors?
For example customer service at WL said their 15mW Nano was usually too underpowered to be a problem without glasses, unless someone pointed it directly at the eyes at close range. This is not true?
This is NOT true!
https://docs.google.com/viewer?url=...ac.uk/aboutus/healthandsafety/LaserSafety.pdf
Even at 5mW , if you don't blind and look away within a few seconds of being hit by the laser , you WILL be causing permanent damage
If you point it at a wall , there are less documentation regarding the reflected diffuse radiation .
The main reason for this is that the wall spreads out the light significantly. If the laser beam were to bounce off of a mirror, it would remain a narrow beam, and could still potentially harm your eye if you stared into it and managed to suppress your blink reflex. However, when the beam bounces off a rough surface like a wall, the reflected light is no longer a beam. Instead, it begins to spread out in the shape of a hemisphere as it propagates away from the wall.
You can tell that the reflected light is spreading out in this way because the spot looks the same on the wall no matter where you are in the room. That means it is reflecting equal amounts of light in all directions. By contrast, if you look directly at the source of the laser (which I do not recommend) you will find it is significantly brighter the closer you get to looking straight into the beam.
We can estimate how much less light hits your eye when looking at the laser spot on a wall (versus looking into the laser itself) by comparing the area over which the light is spread out. When the light first hits the wall, it is all concentrated in a narrow beam, with a diameter around a few millimeters. That gives it an area of roughly 7 square millimeters.
After bouncing off the wall, the beam spreads out to fill a hemispherical surface. At a distance of 1 meter, this hemisphere would have an area of over 6 million square millimeters. If you are even farther away, the area will continue to increase as the square of the distance, and correspondingly the intensity hitting your eye will continue to decrease.
In conclusion, the intensity of light hitting your eye when looking at the spot on the wall from 1 meter away is easily on the order of 1 million times smaller than the intensity if you looked directly into the beam.
But how do you ensure the laser won't clip on other objects indoors ?
How do you ensure the surface is matte ?
Don't take any chance when using lasers above 5mW indoors.
