FLIR has a good handbook on some of the physics: https://www.flirmedia.com/MMC/THG/Brochures/T559243/T559243_EN.pdf https://www.flirmedia.com/MMC/THG/Brochures/

FLIR has a good handbook on some of the physics: https://www.flirmedia.com/MMC/THG/Brochures/T559243/T559243_EN.pdf https://www.flirmedia.com/MMC/THG/Brochures/T559243/T559243_... The rest is light transport, e.g. lensing via index of refraction: https://courses.lumenlearning.com/boundless-physics/chapter/lenses/ https://courses.lumenlearning.com/boundless-physics/chapter/... Here's a cool article on a piece of an old spectrometer: https://utsic.utoronto.ca/spectroscopy-beyond-the-visible-spectrum-the-sodium-chloride-prism/ https://utsic.utoronto.ca/spectroscopy-beyond-the-visible-sp... More information from a distributor of optics: https://www.knightoptical.com/stock/default/windows-and-diffusers/ir-windows/sodium-chloride-windows.html https://www.knightoptical.com/stock/default/windows-and-diff...