Abstract
A optical method for evaluating the natural frequency and the quality factor (Q) of a microstructure is proposed in this paper. The proposed method is based on ultrasonic wave excitation which is a non-contact technique and does not impose undefined loadings. The images of a microstructure vibrated ultrasoniclly are captured by a CCD camera at different frequencies. The vibrational amplitudes of the microstructure are subsequently extracted using edge detection based on a Mexican Hat wavelet transform and an amplitudefrequency spectrum is obtained from which the resonant frequency is determined. The damping characteristic is evaluated subsequently using a half-power method. A silicon microstructure consisting of a perforated crossbeam (205μmX26μm) and a cantilever beam (220μmX23μm) is tested. The thickness of the microstructure is approximately 3μm. The experimental set up is relatively simple and the results show that the proposed method is an effective approach for evaluating the dynamic characteristics of a microstructure.
