There seem to be overlap with Germanium, but doesn't seem enough for far infrared imaging.
https://www.edmundoptics.com/knowledge-center/application-notes/optics/the-correct-material-for-infrared-applications/
Physics noob here. I have the cheapest FLIR sensor (80x60 px sensor). It captures Longwave infrared, 8 μm to 14 μm. It has a tiny lens (probably 1mm in diameter). Trying to add a zoom ability to this sensor.
I have different DSLR lens and other optical scopes. I tried holding the tiny FLIR...