三維外形量測之N步彩色相位移法

Abstract

本論文提出一種N步彩色相位移法用以量測物體的三維外形。首先設計彩色條紋圖樣，並使用投影機投射至物體表面。使用兩台數位相機拍攝物體表面上的扭曲條紋圖樣，並從拍攝的彩色影像中獲得每個像素之RGB亮度值。以得到的RGB亮度值，經由相位移法計算所有像素的相位值。同時以相位誤差查詢表、紅綠藍查詢表修正相位誤差。然後使用相位重建法將相位值轉換為物體表面的高度值。相位重建的步驟包含分支切割線演算法與影像品質導引演算法，以這些演算法改善外形重建之品質。再以資料對位與整合統一從兩台相機獲得的三維座標資料點。最後，本文發展一套結合相位移步驟、相位展開步驟、資料對位、資料整合的整合程式。利用此程式，測試數個量測範例。由量測成果可證實提出之方法可以有效地降低量測誤差。

This thesis proposes a N-step color phase-shifting method for measuring 3D shape of objects. Firstly, color fringe patterns are designed and projected onto the object surface by a projector. Distorted fringe patterns on the object surface are captured by two digital cameras, and intensities of each pixel in the red, green and blue channels are obtained from the captured color images. Phase values of all pixels are calculated by the phase-shifting method from the obtained RGB intensities. At the same time, phase errors are also corrected by using a phase error look-up-table and a RGB look-up-table. Then, the phase-unwrapping technique is applied to convert phase values to the height of the object surface. In the phase-unwrapping process, both the branch cut algorithm and the quality-guided algorithm are included to improve the quality of shape reconstruction. Data registration and integration are performed to unify 3D data points obtained from two cameras. Finally, an integrated program is developed by combing phase-shifting process, phase-unwrapping process, data registration, and data integration. With the developed program, several measurement examples are investigated. From the measurement results, it shows that the proposed method can reduce measurement errors effectively.