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標題: 液晶顯示投影三維曲面量測系統相對方位校正之研究
Study of relative orientation calibration in LCD fringe projection profilometry
作者: 曾棋文
關鍵字: relative orientation;相對方位;camera calibration;absolute phase;相機校正;絕對相位
出版社: 機械工程學系
本研究使用液晶投影機(LCD)配合電荷藕合元件(CCD)還原出三維曲面輪廓,並且以相對方位(Relative Orientation)校正CCD和LCD之間的相對位置,以取得其旋轉和平移的關係,之後再應用實際所求得之尺寸和量測所求得之尺寸之間比例校正基底尺寸。由於相對方位的校正是以CCD相機成像位置之射線及液晶投影機成像位置之射線交點當其校正的依據,但因為射線在經過相機取像和投影機投影時,會通過其透鏡而使的射線扭曲,近而使成像產生變形或投射出的影像產生變形,故在校正相對方位時,要先校正射線因透鏡所產生的扭曲。其中液晶投影機成像位置是以格雷式編碼及五步相位移所計算出的絕對相位替代。以此方法計算出的絕對相位也可以避免傳統雙攝影機找尋空間中對應點的問題,並且也可避免傳統相位移量測曲面時落差太大所遭遇的相位不連續的缺點。

In this paper, we propose a method to construct the surface profile from our measurement by using a LCD projector and a CCD camera. In order to calibrate the relative position between LCD projector and CCD camera, we use Relative Orientation to obtain their relationship of translation and rotation, and then we can calibrate the baseline scale by comparing measurement size physical size. While acquiring images from the camera, lens will introduces distortion. For that reason, before calibrating the relative position between LCD projector and CCD camera, we have to calibrate the distortion first. Because the projector dose not have a physical image plane, so we use Gray code and phase shifting technique to restore the absolute phase and obtain a virtual image plane of the projector, thus we can calibrate the distortion in images. With this method, we need not to find the feature point like in binocular stereo vision system and also can avoid discontinuous phase problem when measuring a surface with a drop height in conventional phase shift measurement.
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