Non-contact full field vibration measurement based on phase-shifting

Vibration measurement systems are widely used in the industry. A variety of vibration measurement techniques are proposed, including methods using an acceleration sensor, a laser displacement meter, and tracking a marker with a camera. However, these methods have limitations that allow only one point to be measured and require markers. We present a novel, non-contact full field joint measurement technique both of vibrations and shape based on phase-shifting. Our key idea is to acquire the frequency of vibrating objects using FFT to analyze the phase-shift error of vibrating objects. Our proposed algorithm estimates the phase-shift error by iterating frame-to-frame optimization and pixel-to-pixel optimization. A feature of our approach is to measure the surface of vibration at different frequencies without markers or texture in full fields. Our developed system is a low cost system, which is composed of a digital-light-processing (DLP) projector and camera (100 frames per second). The results of our experiments show that low frequency vibration of objects can be measured in a non-contact manner with high accuracy. Also, reconstruction of the vibrating object surface can be performed with high accuracy.