Vibration mode shape visualization with dual function DSPI system

Digital speckle pattern interferometry (DSPI) and digital shearography (DS) are full field, non-contact optical methods for deformation or its derivative measurement. These techniques are also well suited for the measurement of vibrations. For the present work we use a dual-function DSPI system for the visualization of resonance frequencies and their mode shapes. The system is convenient and also efficient to switch over from an out-of-plane sensitive configuration to shearography. A time-average technique using a refreshing reference frame used for better visualization of the modes. The technique suppresses ambient disturbances such as thermal noise and low freq. noise, etc so that measurement can be performed under harsh environmental condition. Vibration mode shapes are investigated for objects vibrating sinusoidally at different resonant frequencies, for both out-of-plane and shearography configurations.