Simulation of Vignetting Effect in Thermal Imaging System

摘要

Vignetting effect is a kind of typical nonlinear effect in the thermal imaging system and it will induce the central region of the infrared image is bright, while the edge region is dark. This geometric phenomenon generates because the radiation illumination which reaches the detector's surface decreases gradually with the increase of off-axis distance. Vignetting makes infrared imaging system receive uneven effective energy of incident light-ray from different angle, and the output signal is uneven sequentially. At last the final infrared image brings undue light or dark distortion and the generated infrared image is inconsistent with the real scene. Infrared imaging system works under low contrast between 1 percent and 2 percent. Therefore, the vignetting effect of thermal imaging system influences the quality of infrared imaging seriously. So the exact modeling of vignetting effect isvital for generating an infrared simulation image through optical system . This paper builds a realistic model for thevignetting effect resulted from infrared optical system and analyses the cause of the vignetting effect theoretically.Then simulation is carried out and the simulated results show that the simulation method of vignetting effect can provide the more precise and real infrared image signal to evaluate the capability of infrared imaging system and advance the whole performance.