That’s Hot

Glass blocks heat, as you can see with the clear prescription glasses on the fellow on the left. So glass lenses or mirrors are problematic for a thermal IR camera.

The early video cameras used expensive thorium fluoride lenses, and recent research has focused on less radioactive elements like yttrium fluoride and calcium fluoride.

When looking around with one of these cameras, it’s also spooky to see yourself casting no image in a mirror.