A comparison of methods for in situ discrimination of imaged phase boundaries using electrical capacitance tomography
A comparison of methods for in situ discrimination of imaged phase boundaries using electrical capacitance tomography
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DOI：
10.1088/0957-0233/27/2/025401
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发表时间：
2016-02
影响因子：
2.4
通讯作者：
P. J. Clark;A. Tsoligkas;M. Simmons;P T Robbins;E H Stitt
中科院分区：
文献类型：
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作者：
P. J. Clark;A. Tsoligkas;M. Simmons;P T Robbins;E H Stitt
由于硬件固有的测量分辨率和图像重建过程中产生的平滑效应，使用层析成像技术检测硬边界具有挑战性。本文关注的是数据处理方法的发展，使使用电容层析成像（ECT）在实时应用中可视化界面的液体/液体和固体/液体系统的基础上，在介质中的相位介电常数的差异具有高介电连续。所开发的方法被应用到一系列的phantomy调查其有效性作为一种工具，在两相和三相系统的相边界成像。在基于ECT的断层图像中，相位之间的界面表现为过渡区域;通过基于系统内每个相应相位的已知面积应用阈值技术，可以将过渡区域解析为清晰的界面。断层图像的图像误差，定义为所有像素与其理论值的偏差，已使用逐像素方法计算;然而，这需要精确的先验知识，不适合在线应用;本文中使用的区域方法需要全局相位分布信息，从而允许实时应用。将一系列阈值应用于不同几何形状的体模的断层图像，并使用上面给出的面积和逐像素方法计算每个阈值的相应图像误差。从该范围产生最低图像误差的阈值被进一步用于二值图像中，当与默认阈值相比时，给出改进的断层图像，其中图像精度增加约40%。靠近传感器壁，由于电场线密度降低引起的重建误差，图像变得失真，导致圆形体模在靠近壁放置时延长约10%。
The detection of hard boundaries using tomographic techniques is challenging due to the measurement resolution inherent in the hardware and smoothing effects created during image reconstruction. This paper is concerned with the development of data processing approaches which enable the use of electrical capacitance tomography (ECT) in real-time applications to visualise interfaces in liquid/liquid and solid/liquid systems based upon phase permittivity differences in media with a high di-electric continuum. The methodologies developed were applied to a series of phantoms to investigate their validity as a tool for imaging phase boundaries in two and three phase systems. In an ECT based tomogram, the interface between phases is exhibited as a transition region; by applying a threshold technique based upon known areas of each respective phase within the system, the transient region can be resolved into a sharp interface. The image error of a tomogram, defined as the deviation of all pixels from their theoretical value, has been calculated using a pixel-by-pixel approach; however this requires exact a priori knowledge and is unsuitable for in-line application; the areal method used in this paper requires global phase distribution information thereby allowing for real-time application. A range of threshold values were applied to tomograms of phantoms of varying geometry and the corresponding image error for each threshold value calculated using both the areal and pixel-by-pixel approaches given above. The threshold value yielding lowest image error from this range is further used in the binary images giving improved tomograms with approximately 40% increase in image accuracy when compared with a default threshold value. Close to the sensor wall, the image becomes distorted due to reconstruction errors arising from decreased density in the electrical field lines, resulting in a circular phantom appearing elongated by approximately 10% when positioned near the wall.