Real-time micro-vibration multi-spot synchronous measurement within a region based on digital holographic interferometry

Real-time micro-vibration measurement is widely used in engineering applications. It is very difficult for traditional optical detection methods to achieve real-time need in a relatively high frequency and multi-spot synchronous measurement of a region at the same time, especially at the nanoscale. Based on digital holographic interferometry theories, a method of real-time micro-vibration multi-spot synchronous measurement of a region is proposed to satisfy the demand in engineering applications. A corresponding measuring system is built according to this approach. The high speed acquired holograms are localy calculated. Vibration information of the region can be extracted directly and instantaneously from the holograms by using a fast demodulation algorithm. By this way, the measuring range is enlarged remarkably. The proposed method can achieve real-time need in a relatively high frequency and multi-spot synchronous measurement of a region at the same time. The feasibility of the system is demonstrated by measuring the vibration of a headset diaphragm calibrated by the high precision Doppler vibration measuring instrument. The results demonstrate that the system is feasible, when the frequency range of the vibration is between 100 Hz and 2400 Hz. The measurement error is 3.7% on average and every point in the measurement region has the same accuracy.