運用複合式投光之聚焦形貌量測系統與演算法研製

Abstract

為實現穩健且高效率之自動化光學檢測，在本研究中建立了一完整顯微鏡系統。此系統具有主動式投射程式控制之圖案及執行垂直物鏡移動之能力，以達成高重複度及高適應性之量測。在系統建立之過程中曾產生各式問題，故於系統建立之章節中，問題產生之緣由及其對應之解決方式會被詳盡地介紹。舉例而言，為解決因數位微鏡設備引起之橫向光譜不連續問題，系統改採用柯勒照明模組以達到更佳的照明均質性及光譜連續性。 本研究之主要目的為使用聚焦量測形貌法重建同時具鏡面及粗糙面之樣本輪廓。為達成此目標，研究者提出由結合主動式及被動式投光樣本重建之複合式投光方法。樣本表面品質會先由一軟體運算方法及二維全聚焦影像進行辨別，再將正確的表面高度值分配至指定像素位置。此方法可有效的減少視場中之雜訊，故可提升重建之精確度。 除上述方法之外，本研究另提出數種運算方式以優化量測過程，其中包含投影條紋週期最佳化、創新式具焦量測運算子、及樣品表面反射率問題之解決方法。藉由此類運算過程，形貌重建之精確度、可靠度、及執行效率可獲得進一步的提升。 經由實驗結果證實，本研究建立之系統在二十倍放大倍率下具0.0047μm (1σ) 的重複度，0.497μm/pixel的空間解析度，以及介於1.28μm 與 0.64μm間的軸向解析度。除硬體表現以外，本研究所提出之方法與傳統方法所得成果之差異比較也一併呈現於章節中，且改良後之精密度增進可明確地被觀測。

In this research, a solid microscopic system is developed in the aim of achieving automated optical inspection. Such system has the capability of actively projecting the programmed pattern as well as executing vertical objective movement, along with the features of superior repeatability and adaptability. Numerous issues had emerged during the process of system establishment, and thus the encountered problems and corresponding solutions are also suggested in the article. For instance, to resolve the laterally spectral-dispersive issue caused by the digital micromirror device, a Kohler illumination module is harnessed to attain greater homogeneity and spatial integration property of the reflected beam. The primary objective of this article is to reconstruct samples which contain both specular and diffusive surfaces within a single field of view by the shape from focus method. To achieve such target, a hybrid projection method is developed by the combination of the profiles constructed by active and passive illuminated surfaces. The texture of the profile will first be assessed by a numerical method through a two-dimensional all-in-focused image of the scene, then the correct topography will be allocated to designated pixels. The method can effectively reduce the shooting noise existence within the field, thus enhancing the precision in reconstruction. Additional numerical methods are also developed in order to facilitate the measuring process. The approaches include the optimization of fringe period, a new focus measure operator, and a solution to reflectivity problem. By the application of such processes, the precision, reliability, and efficiency of the reconstruction can be further improved. From experimental results, the repeatability of the system is evaluated as 0.0047μm (1σ) from three experiments, the spatial resolution is 0.497μm/pixel, and the axial resolution lies between 1.28μm and 0.64μm, under a magnification of 20 times. Aside from mechanical performances, the comparisons between ordinary and proposed approaches are also presented, where the proposed optimal pattern and the focus measure operator have evidently better precision than the compared ones.