Smaller than the Eye Can See: Selected Applications of Video-based Measurement

Abstract

Cameras offer advantages over contact sensors, particularly in structures that might be difficult to instrument in a traditional manner. Recent work including motion magnification and phase-based optical flow methods enable the extraction of displacement, vibration, and structural information from videos with imperceptible subpixel motion. In this paper we present two case studies of interest to the structural health monitoring community. One case study involves the analysis of a video from the internal observation deck near the top of the Taipei 101 tower, showing the motion of the tuned mass damper during an earthquake. The other involves using high-speed video to measure the frequency responses of everyday objects as excited by a frequency sweep as reference measurements to identifying the object's material by using separate measurements with a popular song as excitation.