Advances in self-mixing vibrometry

摘要

In this paper, an extremely small and laser Doppler sensor lof low cost is presented. The sensor consists of a laser diode and of an optical system composed by two lenses in order to focus the laser light onto the target. The sensor measures velocity and it is based on the self-mixing effect that occurs in a semiconductor laser diode when the radiation generated inside the cavity is back refelcted into the cavity. Velocity is calculated measuring the position of the freuqency peak on the frequency spectrum of the Doppler spectrum generated by the photodiode present inside the lase diode when modualted by feedback light comign from the moving scattering particle.s The laser Doppler self-mixing velocimeter has been statically calibrated, using a rotating disk covered with white paper. Authors reprot about the Doppler signal amplitude of the velocimeter as function of the characteristics and colour of the target surface. Dependence of the Doppler peak amplitude from the target distance and the angle between target and optical axis of the sensor are also reported. Results regarding dynamic characteristics of hte sensor are reported and it is shown its capability to be used as a laser Doppler vibrometer.