Design of a projection data acquisition system for 3D direct capacitance imaging

Unlike traditional 3D imaging based on stacking 2D images to obtain an interpolated 3D image, the 3D direct capacitance imaging acquires the 3D image directly from the measured capacitance data. A projection data acquisition system for 3D direct capacitance imaging with 16 electrodes and double capacitance measurement channels has been designed. The electrodes are divided into two groups according to the parity of the electrode number. The odd electrodes and even electrodes are connected to ac-based capacitance measuring circuit 1and 2 via a switch network respectively. The switch network is also used to set each electrode at excitation mode, detection mode or idle mode. The influence of switch coupling capacitances is discussed and its soft compensation method is proposed. System design and performance test results are described.