A high-speed camera measurement set-up for deflection shape analysis

This research discusses the experimental techniques required to increase the minimal identifiable displace-ments and the spectrum range of optical measurement approaches. A pseudo-random excitation, tailored to the camera frame rate and recording time, is used to eliminate the windowing effect. The influence of motion estimation parameters, camera settings and the visual pattern is discussed. Because of the cameras limited sampling speed, frequency zooming is used to measure the response at frequencies above the Nyquist frequency by allowing aliasing. Multiple measurements of consecutive sections of excited frequency ranges are combined to produce greater displacements and form a data set spanning over the Nyquist frequency up to the sampling frequency. At a distance of 3 m deflection shapes of a 840x510 mm plate were measured at more than 7000 locations with a noise floor of 0.0003 pixel / approx. 0.3 mu m using an 8-bit B&W high speed camera at 2000 fps and a resolution of 816x850 pixels.