Delaminations are flat subsurface flaws parallel to the sample surface. Lock-in infrared thermography with optical stimulation is proposed to size the geometrical parameters of a delamination. Here we deal with semi-infinite delaminations, which are characterized by three geometrical parameters: length, depth and thickness. In a recent paper we calculated analytically and numerically the temperature oscillation of a sample containing a semi-infinite delamination when illuminated by a homogeneous and modulated laser beam. In this work, we present lock-in infrared thermography experiments performed on calibrated delaminations manufactured on AISI-304 stainless steel. We fit the numerical model to the experiments to retrieve the delamination length, depth and thickness. The agreement between nominal and retrieved values confirms the validity of the method and paves the way for characterization of finite delaminations.