The advanced displacement measurement technique using computer vision has shown several advantages, such as high spatial resolution and no mass loading effect, compared to conventional sensing techniques. However, the accuracy and robustness of vision-based techniques are subjected to the various conditions, including uneven illumination and insufficient lighting. This study introduces an accurate 2-dimension displacement measuring technique with high robustness to the illumination change, which uses two complex Gabor filters and a specially designed marker. The linear phase can be generated around the marker by optimizing the filter parameter for accurate motion estimation. The nonlinearity caused by the complex conditions, such as low light and uneven illumination, can also be reduced by emphasizing marker features. Phase-based optical flow is further employed to extract the displacement based on the extracted phase. The measurement performance is compared with Laser Doppler Velocimetry (LDV) to validate the proposed technique under various lighting conditions and its robustness is demonstrated. The proposed technique is also applied to different structures to show the ability of measuring high-accuracy displacement signals under various conditions.
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