Real-time three-dimensional vibration mode visualization system based on laser speckle interference

In this paper, we describe an improved system that visualizes the 3-D vibration modes on the device surface in quasi-real time without precision optical adjustment. We used three visible semiconductor lasers with adequately separated wavelengths. The incident angles of the lasers are set to detect the two in-plane vibrations and one out-of-plane vibration. A color video camera using three CCDs (red, green, and blue) captures the three isolated speckle images generated by each laser. The experimental results using a rectangular AT-cut quartz resonator show the effectiveness of the system.