整合原子力顯微鏡式和光學式微小形變量測系統之設計開發與性能測試分析

Abstract

本論文的研究目的在於設計開發微小形變及位移量測系統，整合了DVD讀取頭雷射量測功能以及原子力顯微鏡(AFM)探針掃描量測功能。量測系統可以在微小的量測範圍內達到奈米級的解析度，同時也可以進行快速掃描量測。使用DVD讀取頭作為AFM之光學量測系統，以取代原有的光槓桿系統，像散現象將被測物之形變或位移轉變成雷射反射光點之形狀變動，四象限光感測器與訊號處理裝置，將雷射光點轉化成聚焦誤差訊號。透過幾何光學分析，可以從量測光電系統架構推導得聚焦誤差訊號與位移關係曲線(S-曲線)，同時以光學分析軟體模擬驗證像散量測原理中的雷射光點變化情形。以光纖干涉儀作為位移校正設備進行實驗性能測試，探討系統之穩定性、解析度、重現性及線性量測範圍。AFM探針尖端具有比雷射光點更小的直徑，因此可以獲得較佳的水平位移量測解析度，但是容易折損的弱點限制了其用途；相對的，雷射光束卻有不會折損的優點，可以適用於較粗糙的被測物。最後透過量測壓電元件之微小形變，來測試所開發系統之實際性能，包括分析靜態、動態以及多軸向形變，從中獲知剪應變式及積層式壓電元件形變影響參數和其產生效果，以作為精密壓電致動器設計開發之依據。

The aim of this thesis is to design and develop a micro deformation and displacement measurement system that is integrated with the laser measurement function of the DVD pickup head and the scanning measurement function of the atomic force microscope (AFM) probe. The developed measurement system can achieve the nano-scale resolution in small measuring range and can carry out the fast scanning measurement. The DVD pickup head is used as the optical system of the atomic force microscopy to replace the beam deflection system. The astigmatic effect converts the deformation or the displacement of the measured object into the form variation of the reflected laser spot; and the four quadrant photodiode and the corresponding signal processing device transform the laser spot into the focus error signal. Through the analytical method of the geometry optics, the relationship between the focus error signal curve and the displacement (S-curve) is derived; and the optical analytical software also simulates the form variations of the laser spot. By applying the fiber Fabry-Perot interferometer (FFPI) as the calibration instrument, the stability, resolution, repeatability, and the linear range of the measurement system are investigated. Because the AFM-probe has smaller diameter than that of the laser spot; therefore, it can achieve better resolution in measuring the horizontal displacement. But the AFM-probe is very brittle against deflection so it confines its application field. Relatively, the laser beam is very flexible and can be applied to measure rougher objects. Finally through investigating the micro deformation of the piezoelectric elements, the actual measuring performance of the developed system for static, dynamic and multiaxial deformations are tested and validated. At the same time, the derived influential parameters and their effects can be used as the fundamentals for developing precision piezoelectric actuators.