Minimum resolvable temperature difference (MRTD) is a common figure of merit for assessing the performance of thermal imagers, because it represents the thermal sensitivity and spatial resolution. The work in this paper focuses on the design of an instrument that can provide the performance parameter MRTD for the measurement. The instrument under our research, adopted a new work principle based on the theory of Heat Transfer, appears more miniaturized and more portable, which makes the impractical fieldwork possible. In this paper, the new method that enables the high accuracy plane radiation source in the instrument is presented in detail. By means of the theory of heat transfer, the finite elements analysis (FEA) method and the MATLAB software, the analysis and simulation of temperature-field of the
plane radiation source is carried out. Subsequently, the geometrical parameter of the instrument architecture is optimized and the model instrument is manufactured. Finally, the experiment with the model is implemented and the data of the temperature-field is collected. The predictions of the theoretical results are found to agree well with the experimental data. Moreover, the uniformity and stability of temperature-field can meet the requirements of the inspection for the
thermal imaging system.