[JonathonW]

As I understand it, uncooled commercial IR cameras aren't photodetector-based: their sensors are actually heat-sensitive and rely on heating from IR to produce an image. This limits sensitivity and resolution and increases noise.

Higher-quality IR imaging equipment is photodetector based (as in, they operate on the photoelectric effect); these require very low temperatures to operate and need the sort of active cooling the author refers to.

See also https://en.wikipedia.org/wiki/Thermographic_camera , which goes into detail on the different technologies involved.