The Archimedes spiral cord modulating chopper's figure and its working states were simulated. The detector pixels' exposure time, exposal sequence, signal read-out mode and its impact on the following signal uniformity processing were analyzed. Result shows that the detector's exposure non-uniformity and the signal readout mode directly affect the following signal's uniformity processing; the parameter of Archimedes spiral cord, the detector's geometrical dimension, the relative position between the chopper and the detector will affect the detector′s exposal sequence and uniformity. We should synthetically consider the effect of the chopper's parameters when designing the whole thermal imaging system and electronic processing system.