非接觸式阻抗量測是一種利用磁感應原理檢測生物組織導電率的成像技術，其目的是針對生物阻抗的應用技術，尤其是對臨床診斷和追蹤疾病演變過程都具有十分意義。 本論文提出一非接觸式阻抗量測系統的設計方法，目的主要是用來量測實物表面的阻抗影像。本系統設計架構主要包含感測系統、掃描系統、訊號處理系統及人機介面。非接觸阻抗量測是利用電磁場感應渦電流原理，以非接觸的方法得到待測物之導電率，在量測時能夠避免接觸阻抗所帶來的影響，不過對於生物組織阻抗量測的應用中，發射磁通與感應磁通的比例可達到10000:1，為了能有效擷取出感應磁通的成分，本系統改良了傳統的同軸差動線圈，提出一正交主磁場補償差動感應線圈以消除主磁場的影響，使感測器有更佳的靈敏度，並且以高性能的掃描平台來帶動感測器，將感測器所擷取到的導電率資訊送到電腦加以計算分析並且重建影像。 在實驗結果中，吾人分別利用三項不同的性能指標來評估所設計的線圈結構，其中包含感測器的靈敏度、訊號抗雜訊能力及空間解析度，並且實際量測生物組織及金屬導體的表面阻抗影像，而實驗結果不但能驗證本系統的高性能，而且還證明吾人所提出的正交主磁場補償差動感應線圈的可行性與優越性，希望本論文所提出的方法能對非接觸阻抗量測的應用有所貢獻。 The contactless impedance measurement is a kind of technology of image construction to examine biological conductivity by magnetic induction. It is the improvement of application technology at biologic impedance, especially for clinical diagnosis and the tracking the process of disease. The goal of this thesis is to measure the surface impedance of the object. We propose a contactless scheme to measure conductivity. The major scheme includes the sensor, the scanning platform, signal processing system and graphic user interface. This system could estimate the conductivity distribution of the interesting region by contactlessly measuring the coupling field of received coil. The magnetic measurement system could remove the effect of contact impedance. For biologic tissue measurement, the ratio between the primary and secondary components can be up to 10000:1. In order to extract the part of induced current, the primary voltage must be removed from the measurement signal. We use a differential alignment coil to compensate the primary field. The differential alignment sensor could have better effect on the sensitivity. A scanning platform is used to drive the sensor, which extracts the conductivity signal to be calculated and to be reconstructed. In the experiment, three performance indexes are adopted including sensitivity, noise, spatial resolution, to evaluate the proposed coil, and to measure surface impedance of biologic tissues and metals. The experimental result not only shows the high performance of proposed system but also provides the feasibility of applying differential alignment coil in biologic tissue impedance measurement. Hopefully, these improvements can help the contactless impedance measurement be applied in various fields practically.
