I. Introduction
In the research field of industrial process tomography (PT), capacitively coupled electrical impedance tomography (CCEIT), which refers to the contactless detection idea of capacitively coupled contactless conductivity detection technique () [1]–[12], is a new electrical tomography (ET) technique. Compared with conventional contact electrical resistance tomography (ERT) or electrical impedance tomography (EIT), CCEIT can realize contactless measurement and avoid the electrode polarization and electrochemical corrosion effect [6], [10]. Furthermore, unlike the conventional ERT systems or EIT systems, CCEIT regards the conductive gas–liquid two-phase flow as an impedance and uses the whole impedance information (including the real part and the imaginary part) to implement image reconstruction, which pays sufficient attention to the importance of the imaginary part [3]–[7], [10]. For conventional ERT or EIT systems, the usage of the impedance information is not sufficient [6]–[11], [15]–[21]. The conventional ERT systems and some EIT systems usually use the real part of the impedance to implement image reconstruction [6]–[10]. Some EIT systems use the amplitude of the impedance to implement image reconstruction [6], [10], [15]–[21]. Although the amplitude is a way to use the real part and the imaginary part simultaneously, it is a simple and direct information usage approach and the role of the imaginary part has not received sufficient attention [5]–[7], [10]. Therefore, the CCEIT system has better potential in phase distribution reconstruction and parameter measurement of the gas–liquid two-phase flow [6], [10]. However, as a developing technique, the research works on the image reconstruction method of CCEIT are relatively limited.