An ordinary IR seeker sees hotspots but more like a radar display than a TV image.
Within a field of view a retreating fighter in full AB might appear as two dots or areas of heat with a third hotspot in the sky that is the sun. Old IR missiles chased the hottest biggest thing they could see, which usually meant the sun. To prevent the IR seekers chasing the sun they got filters and if they saw several hot things to not chase the hottest one, which led pilots to carry Flares of different intensities.
Late model IR guided missiles like R-73 and AIM-9M had much more sensitive seekers and saw an aircraft as a collection of hotspots and were never locked onto the hottest spot... they could lock onto the front of an aircraft at closer range. That is when flares had to be released in batches to form patterns in the sky to distract the missiles.
The IR seeker designers then went to two colour models that looked in IR and UV... because a front on lock on a warm spot on an aircraft wont be broken by flares because the front of fighters might have a signal in IR but no signal in UV,while the flares had a signal in both frequencies. The missile simply homed on to the locked on IR spot on the front of the aircraft and ignored anything giving off UV light (ie burning material).
DIRCM was the solution and IIR an attempt to defeat DIRCM by using filters that blocked polarised laser waves etc etc etc...