Mon 23 Nov 2020, 18:58
In the meanwhile, though ... yes, an infrared vision device — or rather, what this actually is, a thermal vision device — would reveal targets behind obstacles that are to some degree transparent to the appropriate infrared wavelengths; e.g. smoke, fog, shrubbery, some materials like certain types of plastic or glass panes, fabric screens, etc.
It wouldn't show targets behind e.g. a solid brick wall, or an armour panel.
The difference between IR and thermal is that IR vision shows reflected near-infrared (~1,000nm range); it requires an IR illuminator (floodlight).
Thermal picks up emitted IR radiation (~10µm range) from objects and presents thermal contrasts, showing hotter objects as brighter (or darker, depending on how you've set the display) than the ambient environment. IR is only relevant in darkness; thermal is quite useful also in full daylight.
An IR image looks pretty much like an ordinary floodlit scene in black and white, with visibility gradually diminishing as distance to the illumination source increases; a thermal image is a scene where most things are shades of grey, entirely without shadows, and where certain objects shine in brighter shades, pretty much all the way to infinity.
Not to be confused with image intensifiers (a.k.a. night vision goggles). This is a different technology altogether.
BTW, this shows that the Aliens are ecothermic — they do not generate heat internally as e.g. mammals do; they only hold ambient temperature, like reptiles and amphibians — thus not sticking out in thermal vision.
Before you use the word "XENOMORPH" again, you should read this article through:
https://www.wired.co.uk/article/aliens-throwaway-line-confusion