Compact optical sensor with a self-mixing laser diode for non-contact measurement of ultrasonic vibration

Self-mixing interference in a semiconductor laser is employed for the measurement of ultrasonic vibrations. It has been confirmed by numerical simulations and experiments that there is a linear relation between the vibration amplitude and the amplitude of a signal detected from a self-mixing laser diode (SM-LD)-laser diode subject to optical feedback-for vibration amplitudes less than the half-wavelength of the illuminating light. The proposed method is statable for constructing compact and inexpensive optical systems for measurement of ultrasonic vibrations.