Optimal Pose Guidance for Stereo Calibration in 3D Deformation Measurement

TL;DR

This work tackles the challenge of inefficient and suboptimal stereo calibration for 3D deformation measurement by introducing an interactive pose-guidance framework. It jointly optimizes relative and absolute extrinsics, using the trace of the covariance matrix, $tr(\Sigma)$, as a loss to determine the next optimal pose and guides users via a graphical interface. The method demonstrates higher calibration efficiency and comparable or improved accuracy across simulations, real-world experiments, and thermal deformation measurements, with robustness across varying fields of view. This enables high-precision, non-contact 3D deformation analysis in practical engineering settings, including high-temperature environments, by reducing the calibration burden on non-experts.

Abstract

Stereo optical measurement techniques, such as digital image correlation (DIC), are widely used in 3D deformation measurement as non-contact, full-field measurement methods, in which stereo calibration is a crucial step. However, current stereo calibration methods lack intuitive optimal pose guidance, leading to inefficiency and suboptimal accuracy in deformation measurements. The aim of this study is to develop an interactive calibration framework that automatically generates the next optimal pose, enabling high-accuracy stereo calibration for 3D deformation measurement. We propose a pose optimization method that introduces joint optimization of relative and absolute extrinsic parameters, with the minimization of the covariance matrix trace adopted as the loss function to solve for the next optimal pose. Integrated with this method is a user-friendly graphical interface, which guides even non-expert users to capture qualified calibration images. Our proposed method demonstrates superior efficiency (requiring fewer images) and accuracy (demonstrating lower measurement errors) compared to random pose, while maintaining robustness across varying FOVs. In the thermal deformation measurement tests on an S-shaped specimen, the results exhibit high agreement with finite element analysis (FEA) simulations in both deformation magnitude and evolutionary trends. We present a pose guidance method for high-precision stereo calibration in 3D deformation measurement. The simulation experiments, real-world experiments, and thermal deformation measurement applications all demonstrate the significant application potential of our proposed method in the field of 3D deformation measurement. Keywords: Stereo calibration, Optimal pose guidance, 3D deformation measurement, Digital image correlation

Figures (10)

• Figure 1: Stereo imaging model
• Figure 2: Flowchart of the process of guiding the stereo calibration. (a) Initial input module, (b) pose output module, and (c) pose guidance module
• Figure 3: Comparison of relative extrinsic parameter estimation errors between random poses and optimized poses under Gaussian noise with different standard deviations. (a) Rotation error, and (d) translation error under Gaussian noise with a standard deviation of 0.5 pixel; (b) rotation error, and (e) translation error under Gaussian noise with a standard deviation of 1 pixel; (c) rotation error, and (f) translation error under Gaussian noise with a standard deviation of 2 pixel
• Figure 4: Sample calibration images in the comparative experiments. (a) The calibration target approximately occupied $1/9$ of the common FOV, and (b) the calibration target approximately occupied $1/2$ of the common FOV
• Figure 5: Comparative experiment on calibration accuracy. (a) Experimental setup, and (b) sample of the calibration images