Effects of Image-Pair Processing Styles on Phase-Based Motion Extraction

Phase-based optical flow (PBOF) is a growing discipline in vibration extraction methods. Based on camera data, PBOF uses image gradients and image-pair differences to extract motion from video. Commonly, this technique is combined with the more ubiquitous digital image correlation, due in part to the restriction of PBOF to small, sub-pixel vibrations. In this chapter, work was done to delve deeper into the nominal upper bound and determine its relation to the chosen image-pair processing style. In particular, the upper bound was evaluated with respect to static (current frame-to-reference), dynamic (current frame-to-previous frame), and hybrid dynamic-static processing styles. Results include advantages of standard static and dynamic processing styles, leading to the presentation of the so-called region of goodness associated with the hybrid processing style. Discussion follows for how the hybrid processing style can be used for large-motion handling in simple structures, as well as modifications required for those that are heavily textured. The hybrid processing style is shown to extend the upper bound to the number of pixels between parallel edges within the structure, increasing the efficacy of PBOF to larger stationary vibrations.