Lamb waves-based NDT techniques have been garnering attention, due to the sensitivity of lamb waves to small defects and their ability to travel a relatively long distance with little attenuation. A novel damage detection technique that employs laser excitation is proposed for damage visualization and diagnosis. Laser irradiation is used to generate a lamb wave in the thermoelastic regime. The relationship between the propagation state of the lamb waves, path of propagation, and damage range is discussed. In this paper, two different means based on energy characteristic value extraction and a dispersion compensation algorithm are used to evaluate structural integrity. The results indicate that the system can inspect large plates with high imaging resolution.