Self-mixing frequency measurement using a liquid filled container with elastic bottom

In this study, a method is proposed to measure vibration of absorbing, scattering, and rough surfaces where the self-mixing method is diffucultto apply. In the method, a liquid filled container with elastic bottom is used between the vibrating surface and the laser beam. Hence, the vibration of the surface was transmitted to the liquid. The vibration of liquid surface was measured at frequencies between 10-1000 Hz by using self-mixing method. The frequency of measured self-mixing signal was obtained by continuous wavelet transform based signal processing method. Maximum 1.5 Hz error was observed between the measured frequency and the frequency of the vibration source. The proposed method can expand the range of the applications of self-mixing method where compactness and low cost of the measuring devices are essential.