Investigation of vibration modes for optically transparent components by using digital speckle interferometry and finite element method

An experimental method for studying the natural vibration modes of the acting faces of large-sized optically-transparent components used in the imaging and interference systems in optical-electronic sets is proposed. Based on a noise-proof digital pattern speckle interferometer, an optical system was developed to provide the registration of the normal component of the vibration displacement vectors on the flat optical surface with the deposited diffusing coating. The optimal transmission of the coating was determined for recording the contrast speckle-interferograms. The vibration modes of the flat, diffusing element included in the digital speckle pattern interferometer are investigated in order to verify the results of numerical modeling of its vibrations at resonant frequencies. For natural vibration modes recorded in the range from 0 to 900 Hz, deviations between experimental and numerical results within 5…7% were found.