You may know me as the person who likes lasers a little bit! Given my reputation, it may come as a shock to many of you that I don’t own any high powered laser pointers! Yes, I own high powered laser diodes, but turning those on requires reconstructing the power supply from scratch every time. None of the lasers I own that can be turned on at the drop of a hat are particularly eye-unsafe. The main reason for this is because I’m not STUPID.
If you are lucky and introduced to hobbyist lasers through proper channels, the first thing you will learn is how easily lasers will cause you permanent and irrecoverable eye damage. Human eyes are amazing and intricate machines, but they too have their limits. They are meant for things like daylight and the occasional glance at the sun, not beams of light that are focused down into spots far more intense than direct sunlight.
Sunlight has an intensity of roughly 1,000W/m2. Staring into the sun directly is dangerous, and can cause all manner of eye conditions, including burns if you keep looking too long. As a point of comparison, I was working with a 20mW fiber laser over the summer. One day I got curious and pulled out a calculator to do some back of the napkin math. At the beam focus point, the intensity of the laser pointer was roughly 77,000,000W/m2. Seventy. Seven. Million. Watts. To be fair, this was a fairly high-quality laser that had a small focal point, but your eyes do their best to focus down any laser that enters them.
So, for all of you reading this article, please stick to the low powered lasers. Your eyes, and the eyes of everyone around you, will thank you.
P.S. Especially avoid cheap green laser pointers. They sometimes use IR diodes upconverted into green light, but cheap ones often don’t have IR filters and leak many times more (invisible!) IR light than the green output you can see.
