本論文建立起一套無鏡頭式寬頻超聲波顯微鏡波速量測系統，此量測系統利用單頻脈衝調制(Tone-Burst)信號進行聲波干涉量測，由頻譜分析儀鎖定單一頻率接收回波訊號，直接得到V(z)振盪曲線；此系統的優點在於可針對特定頻率進行聲波干涉量測，並且可選擇不同的操作頻率進行寬頻量測。
　　此系統使用新設計的雙層無鏡頭式超聲波換能器，這些換能器採用雙層式壓電膜的設計，使激發訊號以及回波訊號分別經由兩片相同曲率但各別獨立的PVDF薄膜激發與接收，此設計可解決激發與接收信號的切換電路問題，保護接收端的放大電路；同時可以提高信噪比。
　　經由數種不同材料之表面波與板波的實驗結果，證明新設計的雙層無鏡頭式超聲波換能器的可行性，也確定量測系統的準確度。此外，藉由數種具有鍍膜的複合板試件實驗，配合複合板板波理論推估出鍍膜的機械性質，亦證明本量測系統可應用於鍍層的機械性質檢測。

　　In this thesis, a broad band lensless ultrasonic microscopy measurement system has been set up for material characterization. The measurement system utilizes tone burst signal for sound wave interfering measurement. The reflective signal is received by spectrum analyzer. In this way, V(z) curve can be obtained directly. The advantage of this measurement system is that we can choose certain specific frequency for broad band sound wave interfering measurement.
　　This measurement system utilizes new designed lensless ultrasonic transducers. There are two pieces of piezoelectric thin film in these transducers. Exciting and receiving signals are operated by different PVDF thin film. The electric circuit of both signals is isolated by this manipulation. Therefore, the amplifier circuit of receiver is protected from exciting signal, and the signal/noise ratio is improved.
　　The fabricated two layers line-focused transducers are experimentally tested to characterize their performance. Furthermore, the Lamb wave dispersion curves of coated plates are also measured. Based on a theoretical model for composite plate of bi-layer structure, the theoretical dispersion curves of the coated plates can be obtained. By comparing the theoretical data to the experimental ones, we can estimate the mechanical properties of the coated layer.

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