Accuracy of phase-based optical flow for vibration extraction

Abstract

In this paper, phase-based optical flow done using the complex steerable pyramid is evaluated to quantify upper and lower bounds of accurate pixel displacement extraction. The objective is to understand how typical image parameters affect these bounds and to determine if phase-based optical flow alone is effective and sufficient to extract vibrations. Across the current literature, phase-based optical flow is largely treated as a pre-processing step for more traditional optical methods, and its ability to extract motions rather than magnify them seems to have been largely overlooked. Rather than compound methodologies, phase-based optical flow is evaluated as a motion extraction tool in its own right in both a synthetic and experimental context. The evaluation provides expected bounds given ideal image parameters as well as a metric to adjust these bounds for a general scenario. Beyond these results, previous evaluations specific to phase-based optical flow are addressed and resulting bounds are compared. Due to dramatic effects caused by the image parameters, rules of thumb specific to this type of processing are also discussed.