Application of a laser Doppler vibrometer to nonintrusive diagnostic of frescoes damage

The paper presents the application of a laser Doppler vibrometer as a nonintrusive measurement technique to detect damage of frescoes paintings. Experimental verification is carried on a wall where detachment of the external layer from the inner substrate is artificially introduced. Impulse excitation shows that frequency response functions identify the presence of any damage. Laser beam scanning provides a way to remotely investigate large areas of paintings. Acoustic excitation is also tested; it allows to excite resonant vibrations on detached areas. A measurement procedure is proposed and tested on the experimental wall and on field tests performed on a real fresco inside a church.