相位移法三維外形量測之強度誤差校正

Intensity Error Correction for 3D Shape Measurement Based on Phase-Shifting Method

施孟宏(Meng-Hung Shih)

指導教授 ： 鍾添東

國立臺灣大學/工學院/機械工程學研究所/碩士(2011年)

https://doi.org/10.6342/NTU.2011.02283

摘要

近二十年來，使用結構光法之三維外形量測的研究持續發展。在使用商業用投影機與數位相機之三維外形量測中，投影機的非線性伽馬值與相機的非線性響應都會造成拍攝的強度誤差與相位誤差，這將造成很大的外形量測誤差。本文提出一種簡單的相位移法強度誤差校正步驟。首先，投射正弦條紋圖形於白色平板上，並從拍攝影像中取得強度資料。使用理想正弦曲線配適強度資料。利用拍攝資料曲線與配適曲線之間的差別建立一個強度查詢表。接著使用查詢表校正用於建立三維物體外形影像之強度。研究結果顯示三維外形量測之量測品質有明顯的改善。本文亦提出一個綜合誤差校正法。在強度誤差校正步驟後使用相位誤差查詢表法。與強度誤差查詢表類似，使用一白色平板透過簡單的程序來建立一個相位誤差查詢表。最後，以Visual C++發展出一套整合分析程式，所有的步驟都可以在程式中簡單快速的執行。實驗結果顯示，在大部份的結果中，綜合誤差校正法可以更有效的改善量測品質。

關鍵字

三維外形量測 ； 條紋投影 ； 相位移法 ； 強度誤差校正 ； 相位誤差校正

並列摘要

3D shape measurement based on structured light system is a field of ongoing research for the past two decades. For 3D shape measurement using commercial projector and digital camera, the nonlinear gamma of the projector and the nonlinear response of the camera cause the captured fringes having both intensity and phase errors, and result in large measurement shape error. This thesis presents a simple intensity error correction process for the phase-shifting method. First, a white flat board is projected with sinusoidal fringe patterns, and the intensity data is extracted from the captured image. The intensity data is fitted to an ideal sine curve. The difference between the captured curve and the fitted sine curve are used to establish an intensity look-up table (LUT). The LUT is then used to calibrate the intensities of measured object images for establishing 3D object shapes. Research results show that the measurement quality of the 3D shapes is significantly improved. A combined error correction method is also presented. The phase error LUT method is applied after the intensity error correction procedure. It’s similar to the intensity error LUT that a phase error LUT is created by using a white flat board with simple process. Finally, an integrated program is developed in Visual C++. Calibration of intensities and phases can be applied fast and easily in this program. Experimental result shows that this combined error correction method improves the measurement quality more effectively in most cases.

並列關鍵字

3D shape measurement ； fringe projection ； phase-shifting method ； intensity error correction ； phase error correction

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