Autolevels central spot reversed and converted to grey scale. Made from a RAW image of a white target evenly illuminated. Could be used as a layer to "burn in" central spot?

My theory is that this is just CCD noise which is ordinarily masked by normal exposure.
IR takes a longer exposure and actual signal is difficult to seperate from noise, especially in green and blue pixels

Heat related noise generated by the CCD itself would be concentrated toward the center of the chip.