Improving the spatial resolution of full-field vibration measurements for hollow structures using a speckle compensation calibration method in multi-camera DIC

This paper proposes a multi-pose speckle compensation calibration method to overcome the limitations of traditional multi-camera digital image correlation (DIC) systems, which heavily rely on large overlapping fields of view for external parameter calibration. Our method does not require auxiliary calibration equipment. By acquiring speckle images from multiple poses within the overlapping area, it can achieve precise coordinate unification even when the overlapping area is extremely small. The experiment conducted on ceramic plates verified the stitching accuracy of this method. The results show that, compared with the method based on the calibration plate, the errors of this method in the x, y, and z directions are all reduced by more than 50 %. A translation experiment on a hollow sailboard structure investigated the impact of different overlapping area selections on measurement accuracy. The results indicated that with only a two-pixel-wide overlap, the average error in static measurements could be controlled below 10 μm. In the dynamic hammering test of the sailboard, the deviation in natural frequency was less than 2 % compared to that measured by an eddy current sensor. This method optimizes the utilization of spatial resolution and is particularly effective for hollow structures with limited speckle coverage.