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運用結構光投射與多維影像融合精確重建具尖銳邊緣之三維形貌

建立日期：2018/08/02
  • 作者： 北科大自動化所/黎孟忠、林志哲教授；台大機械系/陳亮嘉教授
  • 出處： 2017 AOI論壇與展覽
  • 內容： Sharp surface edges present very crucial visual information which corresponds to discontinuities in the geometry and physical properties of objects, such as major changes in surface reflectance, illumination, orientation and depth. The research in this dissertation presents a new method employing structured illumination imaging and image fusion to overcome one of the greatest difficulties in 3-D optical measurement: accurate surface sharp edges reconstruction. The surface sharp edges are extremely critical for extracting key geometric dimension information required for fulfilling the tremendous demands of various kinds of precision engineering. Measurement and reconstruction of surface sharp edges using optical surface profilometry is rather difficult, since there exist complicated optical phenomena around surface edges, such as complex diffraction or interference. Noisy reconstructed data around surface edges are commonly observed in many optical detection methods, such as optical moiré projection, confocal microscopy or interferometry. Thus, in this research, a new method is proposed to reconstruct an edge surface profile by integrating a 2-D surface edge with its neighboring 3-D surface profile. The 2-D surface edge is extracted from a high spatial resolution 2-D image, which is obtained using structured illumination imaging to achieve optical super-resolution, so the projected edge contour of the 2-D contour along the optical imaging axis can be accurately determined. The 3-D surface profile neighboring the edge is simultaneously detected by an adequate 3-D optical measuring method, such as phase-shifting based moiré fringe projection, as well as either confocal measurement or optical interferometry. Moreover, in order to have accurate 3-D surface sharp edges reconstruction, the invalid point cloud data existing around the sharp edges is filtered away from the 3-D optical detection result. The neighboring surface between the 2-D accurate detected edge and the identified 3-D surface contour is then reconstructed using extrapolation by NURBS surface fitting to detect the intersecting edge. Some experiments are performed to verify the feasibility, effectiveness and accuracy of the developed method by comparing the reconstructed 3-D sharp edge with one determined using a pre-calibrated high precision instrument. The proposed method ensures that the maximum deviation between tactile CMM measurement and our developed method can keep the measured error to be within 3 𝜇m so that a resolution of the optical imaging system of better than 0.5 pixels can be achieved. The improvement of the measured error of the proposed method, using SIM, over that of using conventional image fusion was 52%. The experimental results demonstrate that the proposed method is effective, accurate and reliable.
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