Jiang Fan, Li Yuanfeng, Chen Shujun
Opt Express. 2018 Aug 20;26(17):21745-21761. doi: 10.1364/OE.26.021745.
In this paper, we introduce a method for dynamic and three-dimensional (3D) arc temperature measurement in non-axisymmetric arc plasma. Optical filters with narrow spectral bands are used to gain 696.5 nm line spectral information of a free-burning Argon (Ar) arc. A measuring system with a setup of mirrors allows a single camera chip to image multi-views of identical welding arc onto one monochromatic image. And based on the underlying characteristics of the arc plasma, we present a modified maximum likelihood expectation maximum (ML-EM) algorithm to reconstruct the emission coefficients from the line intensities. To verify the accuracy of our algorithm, two models of arc plasma have been established to simulate the reconstruction process. Simulation results demonstrated that the modified ML-EM can be utilized to improve the performance of 3D reconstruction compared to common ML-EM methods. To obtain the optimal scheme of the measuring system with limited view directions, the reconstruction quality with different directions is presented and discussed. In the experiment, asymmetric 3D plasma temperature distribution was determined at a direct current (DC) of 80 A and 100A. The results proved the feasibility of the 3D temperature measure method to characterize an asymmetric arc.
在本文中，我们介绍了一种用于非轴对称电弧等离子体中动态三维（3D）电弧温度测量的方法。使用具有窄光谱带的光学滤波器来获取自由燃烧氩（Ar）电弧的696.5nm线光谱信息。一种带有镜子设置的测量系统允许单个相机芯片将相同焊接电弧的多视图成像到一幅单色图像上。并且基于电弧等离子体的基本特性，我们提出了一种改进的最大似然期望最大化（ML-EM）算法，用于从线强度重建发射系数。为了验证我们算法的准确性，建立了两种电弧等离子体模型来模拟重建过程。模拟结果表明，与普通的ML-EM方法相比，改进后的ML-EM可用于提高3D重建的性能。为了在有限视角方向下获得测量系统的最优方案，给出并讨论了不同方向下的重建质量。在实验中，在80A和100A的直流电流下确定了非对称3D等离子体温度分布。结果证明了3D温度测量方法用于表征非对称电弧的可行性。
