Random laser speckle pattern projection for non-contact vibration measurements using a single high-speed camera

3D vision methods are a powerful tool for measuring full-field vibration patterns in the most varied types of surfaces. Digital Image Correlation is typically used to track noticeable features on the surface in order to measure local displacements on the tested system. In this work, a novel randomly structured light system based on laser speckle pattern projection and its calibration procedure are proposed for applying computer vision methods to the measurement of vibration in featureless or reflective objects without modifying them. A simple projector is used based on a laser beam affected by a diffuser element. A stereo vision set-up with at least one high-speed camera is used to record video sequences from which the initial shape and evolution of the sample displacement are obtained. The vibration mode behavior of different steel plates are obtained using this full-field vibration measuring technique. The pros and cons of the proposed method are discussed and compared to similar stereovision set-ups. (c) 2021 Elsevier Ltd. All rights reserved. Lately, high-speed 3D shape measurement techniques became widely used in fields such as biomechanics, industrial quality control, and human-computer interaction. Stereo-vision systems using two fast cameras are the most popular setup to measure full-field vibrations of objects by capturing images from different viewpoints 11,2]. However, as highspeed cameras are expensive, alternative set-ups using mirrors and a single camera have been proposed 13?6], and used for measuring vibration 17]. Moreover, a simpler set-up with a single high-speed camera and without mirror may be used if only the normal out-of-mean-plane displacement of the sample is required 18]. In a 3D coordinate calculation of displacement based on triangulation, the natural features on the surface of the object or