Knowing the dynamic response of structure is crucial in the development and discovering deficiencies of already realised products. In the experimental determination of a dynamic response, an accelerometer is often used due to its accuracy. Instead of an accelerometer, a high-speed camera as contactless method can be used, but investment in such a camera is very high.
In this work, we presented and used a method for measuring displacements with classic camera as an alternative to high-speed cameras. Compared to high-speed cameras, the cost of implementing this method is significantly lower, while the resolution of images is much higher. Method uses harmonical changes in lighting for measuring spectral components of optical flow. We partially changed the used method - we replaced the analogue control of the light source with digital control using pulse-width modulation. We measured the oscillation amplitudes of an excited plate at different excitation frequencies. With successive measurements under the same conditions, we confirmed the validity of the method and the repeatability of measurements at lower excitation frequencies.