現今代表性的厚度量測方法有橢圓偏振法、干涉法與共焦法，其中部分技術能測量厚度與折射率，但僅適用於薄板量測或單層個別量測，少數能同時測量多層厚度與折射率的技術，皆未考慮每層材料相互不平行的問題。為了改善現有技術的不足，本論文以光學基本定理為基礎，提出一套新穎的光學量測方法，透過簡易的光路架構搭配歪斜光線追跡法，不僅能同時量測多層透明待測物的折射率與厚度，也能量測不平行層的傾斜角度，結合自動對焦系統，亦能提升對焦成效。
本論文特點是使用兩不同入射角的雷射作為量測光源，首先利用齊次座標轉換與歪斜光線追跡法建立數學模型，接著擷取從待測物各介面反射之光斑訊號，經過影像處理可得到光斑位置資訊，代回方程式後解出所求未知數，依照已知厚度、折射率與傾斜角度，計算離焦距離，完成自動對焦。本論文亦利用光學軟體ZEMAX建立系統架構，透過模擬量測結果來分析系統特性，並評估系統是否可達成目標，接著依模擬參數將此系統建置於光學桌上，透過校正方法補償系統的安裝誤差後，進行實驗與分析，以此驗證實際情況下本量測系統的可行性。

The representative measurement methods, including ellipsometry, interferometry, and confocal method, can measure thickness and refractive index. However, all methods are limited by thickness range and do not consider that one layer may be unparallel to each other. In order to improve the deficiencies of these techniques, this thesis proposes a novel optical inspection method based on the fundamental theorem of geometrical optics. Through a simple optical structure, it can measure not only the thickness and refractive index of multilayer transparent samples but also the inclination angle of unparallel layer simultaneously. In addition, the measurement system, combined with the auto-focusing system, can improve the focusing effect.
First, we establish a mathematical model using the homogeneous coordinate transformation and the skew ray tracing method. The characteristic is that two lasers with different incident angles are used as the light source. And then camera would capture the spot signal reflected from each boundary. After image processing, we obtain the spot position information. Furthermore, the data are substituted into the equation to calculate the unknowns. According to the known information, the defocus distance can be calculated to achieve the auto-focusing. In this thesis, we use ZEMAX, an optical simulation software, to establish the system structure, analyze the system characteristics, and evaluate the system feasibility. Finally, a laboratory-built prototype is constructed according to the simulation parameters. The installation error is compensated by the calibration method. After that, experiments and result analysis are carried out to verify the feasibility of the measurement system.

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