Full-Field Displacement Measurement of Rough Surfaces Using Microwave Speckle Tracking Interferometry

The microwave radar-based full-field displacement measurement technology offers appealing advantages over traditional methods, such as long-range monitoring capability and strong environmental adaptability; however, it commonly requires corner reflectors to identify and track multiple measurement points in surfaces with few macroscopic features, which may cause nonnegligible changes in monitoring lightweight structures, and a reduced number of measurement points to the level of traditional contacting sensors. The microwave speckle tracking interferometry (MSTI) method is proposed to overcome the above drawbacks. We use the grayscale distribution of holographic microwave speckles to uniquely mark the measurement points in rough surfaces, which avoids artificial marking and improves the number of measurement points to the level of vision-based methods. Specifically, the quality control method of the microwave speckle pattern for marker tracking is established theoretically by considering the surface morphology, target motion, and imaging parameters, and microwave speckle pattern correlation (MSPC) can obtain the marker tracking with 0.06-pixel accuracy by fitting the 2-D correlation function. Finally, the full-field displacement measurement with holographic phase interferometry (HPI) and the corresponding error analysis are presented. Experimental results have shown that our approach is desirable for contactless full-field displacement measurement of rough surfaces without artificial markers.