Single-camera single-axis vision method applied to measure vibrations

Increased interest has been witnessed for full-field techniques measuring vibrations. 3D vision methods coupled to two high-speed cameras have proven to be a valid solution to measure 3D displacements, notably with the Stereo Digital Image Correlation (SDIC) tools. The now conventional pseudo-stereo system with a single high-speed camera and a four-mirror adapter, generating two virtual cameras, may also be used, even if it is rather complex to operate and remains limited to small objects. In a logic of simplification of the protocol, the authors present here a set-up requiring a single high-speed camera and no mirrors, with the associated full-field single-axis vision method. The latter is logically designed to measure the vibrations of items whose displacements are locally along a single axis (usually normal to the surface). This paper reports firstly the results of the full-field measurement of the vibrations of a plate, validated by a comparison with those obtained with the four-mirror adapter set-up, and secondly the application to the full-field measurement of the vibrations of a tambourine. Thirdly, the conventional pseudo-stereo technique and the proposed vision method are compared and assessed, in order to establish their respective limits and potential complementarity. Finally, once the application of the method to plane objects is validated, measurements have been carried out on a non-planar object: a bent plate; the results obtained highlight the possibility of using the proposed approach for non-planar surfaces. (C) 2019 Elsevier Ltd. All rights reserved.