Why does an infrared remote control not affect thermographic measurements, while the reflection of a person can?
This is a question of wavelength. Infrared remote controls operate in the near infrared range (e.g. 0.85 µm or 1.55 µm), while thermographic cameras usually work within MWIR (3-5) µm, or LWIR (8-14) µm. The remote controls simply do not emit any energy in the waveband that the cameras operate. While our body temperature emits radiation in both MWIR and LWIR, this can be reflected off our target objects and reflected back to the camera, this can affect our measured temperature if it is not correctly dealt with. Many other objects can be reflected in our images and cause errors, even cold objects like clouds, or in the image below, a tree.