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Measuring In-Plane and Out-of-Plane AmplitudeSensors and Ultrasonics |
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[Sensors and Measurement Systems / Acoustics] [IAP-Homepage]
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Measuring In-Plane and Out-of-Plane AmplitudeSensors and Ultrasonics |
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Fig. 1 | The Laser Out-of-Plane Amplitude Measurement System (Fig. 1) is based upon a heterodyn interferometer. A laser beam with a wavelength of 632,8 nm is split into an object beam and a reference beam. The object beam hits the object perpendicular to the vibrating surface. Due to the Doppler shift the light frequency is shifted proportionally to the out-of-plane velocity of the vibrating surface. The reflected frequency modulated beam now interferes with the reference beam. A photo diode converts the optical signal into a voltage proportional to the light intensity. From the voltage signal processed by a spectrum analyzer the amplitude distribution of the vibrating surface can be calculated. |
Fig. 2 | Fig. 2 shows a measured amplitude distribution of a compound transducer consisting of a piezo ceramic and a glass carrier. The transducer was driven at a frequency corresponding to a transversal mode of the compound. |