The research on infrared radiant characteristics of typical target is important for the detection and recognition of
target, infrared simulation calculation and design of electro-optical countermeasures. Thus it is essential to select
appropriate test method and optimal calculation method to improve the test accuracy and reliability of infrared radiant
intensity. In this paper, three instruments including SR5000 spectroradiometer (CI, MigdalHaEmek, Israel), remote
sensing interferometer spectrometer Tensor37 (Bruker, Germany) and Image IR8325 (InfraTec Ltd, Germany)
mid-infrared thermal imager were applied to test the infrared radiant (1μm-3μm，3μm-5μm) intensity of decoy samples.
Three methods were designed based on two operational principles including direct test and indirect test. The SR5000
spectroradiometer which is able to obtain the value of radian intensity immediately is regard as direct test. The other two
instruments which deduce and calculate infrared radiant intensity according to Planck's law and Lambert's cosine law
with some preliminary tested parameters such as the response voltage，the distribution of infrared radiant temperature of
flaming samples and calibrated data by blackbody, however, are regard as indirect test. Reasons for the diversity of
experiment results were provided through analysis on the concrete measurement theory and detailed calculation methods.
Moreover, some rules and suggestions were put forward to improve the test accuracy and reliability of infrared radiant
intensity when different methods were adopted.
It is shown from experiment results that the average mid-infrared radiant intensity obtained from SR5000 was about
903W/Sr in near-infrared band，whereas Tensor 37 and Image IR8325 was about 834W/Sr and 547 W/Sr respectively. It
was proved that maximum relative of calculated results from remote sensing interferometer spectrometer Tensor37 and
results measured with SR5000 spectroradiometer is below 13%, which meet the general accuracy requirements.
Although rigorous reasoning applied, results gained by Image IR8325 mid-infrared thermal imager varied so much from
above-mentioned two instruments and the relative error is about 25%~40%. It is analyzed that complexity of the
measurement procedure and similarity hypothesis is the main reason for the errors generated.