運用雙相移疊紋投射之三維顯微形貌量測技術研發

Development of 3-D Microscopic Surface Profilometry Employing Dual Phase-shifting for Moiré Projection

蔡立祥(Li-Hsiang Tsai)

指導教授 ： 陳亮嘉

國立臺北科技大學/機電學院/自動化科技研究所/碩士(2011年)

摘要

在本研究中提出一種新式的摩爾(Moiré)輪廓術之量測方法用於微元件之量測。系統使用光柵片產生正弦條紋結構光並結合由電腦產生之虛擬光柵互相疊加產生摩爾條紋影像。此方法的優點在於可以藉由調整虛擬光柵之週期來改變產生之摩爾條紋的週期，也因為其優越的調變性在量測時可避免階高量測範圍之限制。不過有一個問題存在於摩爾條紋影像中，即兩個不同週期之條紋結構光進行疊加時，除了疊加的摩爾條紋部分以外，未疊加之高頻條紋結構光亦會殘留於影像上，使摩爾投光量測法受到影響。為了解決此問題，本研究提出了藉由光柵片產生之條紋結構光經投射至物體表面所產生之變形結構光，與電腦產生之具相同相位之虛擬光柵進行四步相移進行疊加，如此可獲得一清晰之摩爾條紋影像，同時，經投射至物體表面所產生之變形條紋結構光再與經相移(分別為pi/2, pi, 3pi/2)之虛擬光柵分別進行上述之疊加演算，如此可建立具四步相移之清晰摩爾條紋影像。由實驗結果證明，從標準件上多次階高塊之重複性量測結果得知，所發展之系統在一個量測標準差均可低於1μm，且量測精密度與 Keyence VK-9700掃描顯微鏡相比，兩者之間之最大相異度在2%以下，相較於傳統四步相移法量測之精確度亦提升1%以上，顯示本研究所提出量測方法之優越性。

關鍵字

自動化光學檢測(AOI) ； 表面形貌量測 ； 三維輪廓 ； 摩爾輪廓術

並列摘要

A new dual phase-shifting moiré projection method is proposed for microscopic three-dimensional surface profilometry. One of the difficult technological challenges encountered in employing moiré triangulation projection for automatic optical inspection (AOI) is to detect high contrast projected fringes from an object’s surface having vast variation of surface reflectance. Surface reflectance from different surface regions could vary significantly due to diverse surface characteristics, such as texture and roughness, in which returning light may be any form of specular reflection, diffusion or scattering. Undesired measurement results are common when deformed moiré fringes cannot be satisfactorily detected by an imaging detector. To resolve this, the proposed method generates a moiré fringe using the deformed fringe being detected from the object’s surface and a virtual sinusoidal grating being created by the computer. A spatial averaging approach is applied to phase-shifted moiré interferograms formed between one deformed fringe and virtual fringes having an equal shifted phase, such as pi/2. High-contrast phase-shifted interferograms can be generated for more accurate 3-D surface reconstruction via phase wrapping and unwrapping. One great advantage of the method is its tunable control over the moiré fringe period for reaching more measurable step heights without phase ambiguity problem. From the experimental analysis using standard targets and industrial PCB, it is verified that the method can significantly improve measurement accuracy when measuring a low reflected surface.

並列關鍵字

Automatic optical inspection (AOI) ； Surface profilometry ； Moir&eacute ； 3-D vision ； Fringe Projection.

參考文獻

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