Research On Non-transparent Structure Target Emissivity Measurement Technology Based On Integrating Sphere Reflection Method

Emissivity is one of the important parameters for evaluating infrared radiation characteristics.The internal emissivity distribution is an important parameter to evaluate the emissivity of the non-transparent target coated with different radiation characteristics or with characteristic structure.Therefore,the non-transparent structure targets emissivity distribution at room temperature are measured and studied based on the complete hemisphere laser integrated reflection scheme.The specific research contents and main research results are as follows:Firstly,the structural target emissivity distribution measurement model is studied based on the integrating sphere reflection method.Based on the reflectance distribution measurement model of non-transparent structure targets,three correction factors,including hole correction factor,non-ideality of optical path and standard gold plate reflectance,are introduced,and the non-transparent structure targets emissivity distribution measurement model is established by combining the laser spectral radiation brightness drift correction method.Secondly,a non-transparent structural target emissivity measurement system is designed and built.Based on the emissivity distribution measurement model of nontransparent structure target by integrating sphere reflection method,the near-infrared laser source subsystem,gold-plated integrating sphere subsystem,photoelectric detection subsystem and precise electronic control displacement subsystem are designed and constructed respectively.The near infrared laser is selected as the laser source,and the stability of the laser is measured and analyzed.The filter radiometer is designed to convert the photoelectric signal,and the automatic acquisition program of digital meter is used to complete the signal acquisition.The number of scanning points and dwell time of the laser are designed by writing the labview program.Finally,the emissivity distribution of the flat plate and cavity structure targets is measured at the laser power of 3 W respectively.The stability of the system is evaluated by collecting the standard gold plate surface reflected signals in different time periods.The relative standard deviation of the collected signals is 0.67%,and the repeatability of multiple measurement results is 0.30%.The laser spectral radiation brightness drift is corrected,and the measurement accuracy is improved by 28.2%.The system resolution has been improved by 33.3% and 66.7% respectively by changing the lens with different focal lengths to reduce the laser spot size.The emissivity distribution characteristics of targets with different structures are measured,the distribution characteristics of emissivity are accurately characterized.The standard uncertainty of the system for measuring the standard aluminum plates emissivity at room temperature is better than 4%(k=1).The relative deviation between the measured results in this paper and the national standard measurement value of the Institute of Optics of the National Metrology Institute is 5.90%,which is within the combined value of the declared uncertainty of the two groups of results.The good consistency verifies the reliability of the measured results in this paper.The experimental results show that the integrated sphere reflection method established in this paper is stable and reliable in measuring the emissivity distribution characteristics of non-transparent structure targets.