Bi-modal vibration analysis with stroboscopic heterodyned ESPI

• Published in: Measurement science & technology 1997-06, Vol.8 (6), p.648-655
• Main Authors: Valera, J D R, Jones, J D C, Løkberg, O J, Buckberry, C H, Towers, D P
• Format: Article
• Language: English
• Subjects: Exact sciences and technology; Fundamental areas of phenomenology (including applications); Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Interferometers; Measurement and testing methods; Measurement methods and techniques in continuum mechanics of solids; Optical instruments, equipment and techniques; Physics; Solid mechanics; Structural and continuum mechanics
• ISSN: 0957-0233; 1361-6501
• DOI: 10.1088/0957-0233/8/6/011

An electronic speckle pattern interferometry (ESPI) system, utilizing stroboscopic illumination, has been developed for bimodal vibration analysis; timing of the illumination pulses is controlled to isolate the individual modes. An object vibrating simultaneously at two frequencies, related by an irrational number, was examined experimentally. It was observed that when the frequency of the illumination pulses corresponded to one of the vibration frequencies and the pulse train was phased with the vibration, the fringe pattern observed only showed information on the other component frequency. In this way, the fringe pattern associated with either of the component frequencies could be made to disappear, and each mode could be investigated independently. The vibration amplitude map of the remaining component was obtained using heterodyned fringe analysis techniques. (Original abstract)