[2A6] Sub-pixel displacement measurements using quantitative visual vibrometry
L Dougill
University of Bristol, UK
The research focuses on the field of visual vibrometry and its application to NDT through the use of various video and processing techniques. The concept of visual vibrometry was explored by utilising regular cameras to recover the displacement of a structure when excited.
Visual vibrometry works by measuring relative changes in pixel values, which may be used to detect and track motion. It is due to a camera’s ability to collect spatially dense full-field measurements that visual vibrometry has potential as a rapid non-contact large-area testing method for structural health monitoring (SHM). Visual vibrometry as a method for NDE works on the basis that damage alters the vibrational modes in a way that is imperceptible to the human eye but potentially visible through image processing. It is through the application of optical flow-based analysis that sub-pixel displacement measurements may be extracted from video data.
The present work involved the development of a simulation tool for exploring the effect of different camera dynamics. The sensitivity of the visual system was explored by taking experimental video data for an excited specimen and comparing its performance with a laser displacement sensor. Preliminary testing showed displacements of less than 1/100th of a pixel could be extracted.
The present work involved the development of a simulation tool for exploring the effect of different camera dynamics. The sensitivity of the visual system was explored by taking experimental video data for an excited specimen and comparing its performance with a laser displacement sensor. Preliminary testing showed displacements of less than 1/100th of a pixel could be extracted.
