In this paper, Lamb wave health monitoring in plate structure for detection of nonlinear contact scatter is conducted using vibration modulation technique. The low frequency vibration varies the interface area within the contact defect; therefore the amplitude and phase of high frequency Lamb waves reflected from the contact defect will be modulated. By time-frequency analysis of modulated Lamb wave series, the nonlinear responses at frequency of vibration are extracted out and used for defect imaging. It was shown that the nonlinear Lamb wave imaging method based on vibration modulation can effectively characterize and locate the nonlinear contact defects.© (2011) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.