Abstract
At present, the Monte Carlo method is the only method to evaluate the area blackbody emissivity, so it needs to be compared and verified with other calculation methods. In particular, the efficiency of Monte Carlo is low when the micro-cavity structure of the area blackbody is more complex for higher emissivity. An efficient algorithm for calculating emissivity of the area blackbody based on the multiple reflection method was put forward in this article. A multiple reflected light path that radiated into the inner micro-cavity structure of the area blackbody was simulated. The ratio of the outgoing light intensity to the incident light intensity was obtained by setting a threshold of the outgoing light intensity, and then the area blackbody emissivity was calculated. The simulation results showed that, compared with the Monte Carlo method, the results of the emissivity calculation were similar, and calculation efficiency was increased more than 100 times under the same micro-cavity structure. A practical area blackbody was made based on the simulation results from the proposed multiple reflection method, and the emissivity measurement experiments were carried out and compared to the cavity blackbody at the same temperature. The results showed that the emissivity was near one and stable for the NIR (Near Infrared) spectrum range when the temperature was higher than 280°C. Thus, the feasibility of the multiple reflection method for calculating the area blackbody emissivity was verified. The multiple reflection method proposed in this article provided one more design path for developing area blackbodies with more complex micro-cavity structures.
Highlights
In recent years, with the rapid development of infrared radiation metrology, spectral detection technology, and thermal imaging technology, it is significant to develop the blackbody radiation source for calibration [1,2,3,4]
After the light has been reflected by the V-groove area blackbody, the vast majority of the light has been absorbed and only some of the light can be returned by reflection
The measured emissivity was obtained by comparison with the cavity blackbody at different temperatures, and the theoretical emissivity was calculated based on the multiple reflection method
Summary
With the rapid development of infrared radiation metrology, spectral detection technology, and thermal imaging technology, it is significant to develop the blackbody radiation source for calibration [1,2,3,4]. Cavity blackbody has been maturely developed and applied to calibrate a small infrared instrument, but it cannot meet the calibration requirements for a large aperture area source infrared detection instrument; so, the demand for the area blackbody is becoming stronger. The emissivity calculation method of the cavity blackbody does not apply to area blackbodies; the solution of emissivity for the area blackbody is very important [5]. In the development of the blackbody, it is important to evaluate and measure its radiation capability. Buckley proposed the integral equation method in the 1930s and gradually improved it by Sparrow and Bedford et al [6]. The integral equation method assumes that the reflection occurring on the inner wall of the blackbody cavity is ideal diffuse reflection and establishes the
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