The Shape and Size of Glare Around Bright Lights

[Ravi]

20mm, 2mm thick, for 20 bucks. Not bad! Be careful with them, is my advice. If you drop em, they crack.

 

[Mick West]

20mm, 2mm thick, for 20 bucks. Not bad! Be careful with them, is my advice. If you drop em, they crack.

It's unpolished. But I've got a polisher, and it will be interesting to see how well it works without polishing. I was quite surprised what a good image you get reflected from a matt metal surface, so maybe a window might work somewhat with not polishing.

Here's a metal surface reflecting my hand in thermal IR.


But, it's matt, with near-zero specular reflectivity.

 

[Ravi]

Nice example!

It's of course all due to the use of long wavelengths. You need half-lambda surface quality to make a "mirror", for IR of say 10 um, this comes down to 5um, which is what likely is the surface roughness of the metal part shown.