| Summary: | 碩士 === 國立清華大學 === 動力機械工程學系 === 103 === This research integrated the digital image correlation (DIC) method system with the currently popular light field camera to establish a novel optical measurement (NOM) system. To attempt to break through the current DIC technique with limitation on measuring surface topography of opaque bodies, this research manufactured transparent specimens made of PDMS mixed with phosphor powder (hereinafter called phosphor powder specimen). To investigate the feasibility of measuring the internal deformation by using the established NOM system, this research attempted to simulate the volumetric digital Image correlation (VDIC) method. To compare the experimental results obtained by the NOM system with the traditional DIC method system, same experiment was performed on the transparent specimens with spray coating.
Four types of experiments were performed in this research. To the phosphor powder specimens, three experiments were implemented to study the limit of the DIC method, including rigid body translation experiment by the 2D-DIC method (for the aluminum plate and phosphor powder specimens), four-point-bending experiment by the 2D-DIC method (for the white PDMS specimen covered with random black speckle pattern and phosphor powder specimen) and out-of-plane displacement experiment by the 3D-DIC method (for the white PDMS specimen covered with random black speckle pattern and phosphor powder specimen).
The fourth experiment was performed by using the NOM system to the displacement measurement of a step-shaped specimen. The characteristic of this experiment is to demonstrate the refocus feature and the measurement superiority of the light field camera. Traditional DIC method was also used to compare and verify the NOM system.
Regarding the phosphor powder specimens, in contrast to the small difference between the theoretical and experimental results obtained by the 2D-DIC method, displacement measurement was unable to carry out by the 3D-DIC method due to the shielding effect of speckles.
On the displacement measurement experiment of the step-shaped specimen by the 2D-DIC method, better image resolution on the focal plane was achieved and lower matching error in the speckle matching process was obtained. Therefore, accurate results were obtained. Because of the specification limit and insufficient operational experience of the light field camera, the results obtained by using the NOM system in this research are not satisfactory. However, based on the latest report of the technology development of the light field camera, the NOM system has full potential to become a useful system.
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