Experimental Quantification of Sensor-Based Stereocameras’ Extrinsic Parameters Calibration

Three-dimensional digital image correlation (3D-DIC) has shown to be a powerful tool to extract full-field displacement and deformations of structures using a series of synchronized stereo images. Before performing 3D-DIC measurements, the stereovision system must be calibrated to determine the relative position of the two cameras. Traditionally, this has been done by taking pictures of a calibration target whose dimensions are well known. Because the calibration target must be as large as the inspected object to properly calibrate the entire measurement volume (i.e., large-area calibration), for large fields of view, the calibration procedure becomes a challenge. This research aims at reducing the complexity of large-area calibration by measuring the extrinsic parameters of the stereovision system using a suite of sensors. In particular, three inertial measurement units and a laser distance meter are used to measure the cameras’ relative position and orientation in space. In this chapter, the performance of the proposed sensor-based extrinsic calibration is compared with the traditional image-based calibration method. Laboratory tests show that the extrinsic parameters computed with the sensor-based method can be used for performing a 3D-DIC analysis that yields an error below 5% when the results are compared with the displacement retrieved using a traditional approach. The results of this study demonstrate that the proposed sensor-based calibration approach is a valid and a faster alternative to traditional image-based calibration methods. The sensor-based calibration has the potential to expand the use of 3D-DIC by making it more suitable for large-scale applications.