Objective evaluation method for advance thermal imagers based on minimum resolvable temperature difference

Advancement in thermal imaging technology has improved the day and night surveillance capability of electro-optical system. Thermal imager detects the object of interest by sensing the temperature difference. The performance evaluation of these thermal imagers plays a vital role prior to effective deployment. Key performance parameter of thermal imaging system is minimum resolvable temperature difference (MRTD), as it is able to determine the overall system performance involving a human operator. MRTD is capable of defining the minimum temperature difference required to resolve the bar target pattern of defined spatial frequencies and provides the true estimate of the range performance of a thermal imaging system. In conventional methods, 4-bar target of defined resolution is exposed to the minimum resolvable condition to compute MRTD values. Presently, subjective MRTD measurement employs an operator to observe the minimum resolvable condition, and therefore, measurement suffers from poor repeatability. During large volume production, this practice becomes a tedious procedure to evaluate large numbers of thermal imaging sights. To ease the performance evaluation procedure, an objective MRTD measurement method for the evaluation of the thermal imaging system has been presented. In the present work, objective MRTD measurement method for advance thermal imager by computing the modulation transfer function and noise equivalent temperature difference has been presented. Experiments have been conducted to measure subjective and objective MRTDs. Results for both subjective and objective MRTD measurements have been compared and presented. It is found that the proposed method is able to produce very close result within accuracy of more than 95% than that of conventional methods.