METHOD OF MEASURING FREQUENCY CHARACTERISTICS OF MECHANICAL CONSTRUCTIONS BY OPTICAL METHOD Russian patent published in 2018 - IPC G01N21/62 G01H9/00 

FIELD: measuring equipment.

SUBSTANCE: invention relates to measuring equipment. Method for measuring the frequency characteristics of mechanical structures consists in the fact that the structure under study is illuminated with coherent laser radiation. Form a reference and subject optical waves. Using the optical system, they form simultaneously in the planes of two photodetectors – a digital video camera and a point high-speed photodetector – an image of the structure under study, covered with a speckle structure with a superimposed reference optical wave in such a way that the period of occurring interference fringes was greater than the average size of the speckles in the image plane of the structure under study, and the average size of the speckles in the image plane of the structure was larger than the maximum dimensions of the input aperture of the point high-speed photo detector. Oscillations are excited by gradually changing the frequency of the external force; they search for and record the frequencies of the resonant vibrations of the structure under study by analyzing the output voltage from a point-like fast-acting photo detector. Frequencies of the resonant oscillations of the structure under study are determined by the steady-state periodic oscillating packets of the output voltage of a point high-speed photodetector with the maximum number of oscillations in the packet, which corresponds to the resonant frequencies. Speckle interferograms are recorded that characterize the vibrational modes of the structure under study at each frequency of resonant vibrations.

EFFECT: increasing sensitivity and accuracy by eliminating measurement errors due to the interpretation of interference patterns, expanding the range of measured amplitudes and frequencies, reducing the time required to test structures, reducing the cost of testing equipment and reducing the complexity of frequency testing, expanding the range of tested structures.

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