近場量測於非平坦表面之成像

Imaging of Rough Surfaces By Near Field Measurement

詹舜傑(Shun-Jie Chan)

指導教授 ： 丘建青

淡江大學/工學院/電機工程學系碩士班/碩士(2020年)

https://doi.org/10.6846/TKU.2020.00258

摘要

微波成像是一種以微波作為訊號傳遞的成像方法，屬於電磁逆散射問題。其原理是用微波照射被測物體，然後通過物體外部散射場的測量值進行數學式的計算來獲得最終的目標-介電系數的分布。介電係數可以用來重建物體的形狀、材質等等。由於介電系數與生物組織的含水量密切相關，所以微波成像常用來作生物組織的成像。
本論文將對週期性非平坦表面的近場量測進行研究，比較近場與遠場的誤差，結果顯示近場的重建效果較遠場來的好。吾人利用已知邊界條件及量測到的散射場值，可以推導出一組積分方程式，再由散射場積分方程式算出電場，將逆散射問題轉換成最佳化問題，接著使用自我適應之動態差異型演化法(SADDE)重建出物體位置及介電系數分佈，並比較其對非均勻物體重建之蒐尋速度及穩定性。
利用自我適應之動態差異性演化法重建出週期性非平坦表面，不論一開始的猜測值如何，自我適應之動態差異性演化法總會收歛到整體的極值(global extreme)，因此在數值模擬顯示中，即使最初的猜測值遠大於實際值，吾人還是可以求得準確的數值解，成功的重建出表面形狀函數、週期長度和相對介電常數，模擬結果顯示在近場量測的誤差要比遠場量測來的小

關鍵字

微波成像 ； 近場量測 ； 非平坦表面 ； 自我適應之差異型演化法

並列摘要

Microwave imaging is an imaging method that uses microwaves as a signal transfer, and belongs to the problem of electromagnetic backscattering. The principle is to irradiate the measured object with microwave, and then use the measurement value of the external scattering field to calculate the mathematical formula to obtain the final target-dielectric coefficient distribution. The dielectric coefficient can be used to reconstruct the shape, material, etc. of the object. Because the dielectric constant is closely related to the water content of biological tissues, microwave imaging is often used to image biological tissues.
In this paper, we will study the near-field measurement of periodic non-flat surfaces and compare the error between the near and far fields. The results show that the reconstruction effect of the near field is better than that of the far field. Using known boundary conditions and measured scattering field values, we can derive a set of integral equations, and then calculate the electric field from the scattering field integral equations, convert the inverse scattering problem into an optimization problem, and then use the dynamic difference of self-adaptation Model evolution method (SADDE) reconstructs the object position and dielectric coefficient distribution, and compares the search speed and stability of the reconstruction of non-uniform objects.
Using the self-adaptive dynamic differential evolution method to reconstruct a periodic non-flat surface, regardless of the initial guess value, the self-adaptive dynamic differential evolution method will always converge to the global extreme (global extreme), so in the numerical simulation In the display, even if the initial guess value is much larger than the actual value, we can still find an accurate numerical solution and successfully reconstruct the surface shape function, period length and relative dielectric constant. The simulation results show that the error in the near field measurement Smaller than measured in the far field.

並列關鍵字

Microwave Imaging ； Near Field Measurement ； Rough Surfaces ； Self-Adaptive Dynamic Differential Evolution (SADDE)

參考文獻

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