Most of his work was dealing with and accounting for reflections that left the machine. If you have a prism that’s sending 95% of the light where you want it to go, when it’s a multi watt laser you can’t just let that 5% go wherever it wants. You will blind someone. So his job was getting black bodies in all the right spots to absorb the lost light.

His safety goggles looked like even more expensive Oakleys of that era and they were (much more expensive).

How can one know what is dangerous for the eyes or not? Years ago I got an "IR illuminator" (from aliexpress, probably) that I wanted to use with my raspberrypi NoIR camera, for fun. Say filming myself during the night to see how much I move while sleeping, or making my own wildlife camera trap.

But I was scared that it could be dangerous and never used it (I tested it in an empty room, but that was it).

Is there a safe way for a hobbyist to get an IR illuminator and be sure that I won't make somebody blind with it?

I assume you're concerned about reflections from the camera lens or housing? In my mind, the archetypal camera is mounted on a nice tall pole, silhouetted against open sky, and painted matte black.

> watt class lasers

Surely those would be excessive for someone attacking the sensor, unless they want to remotely sear some graffiti by burning away paint.