Systems for and methods of characterizing the thickness profile of laminated glass structures are disclosed, wherein the laminated glass structure has at least one gradual transition region between adjacent glass layers. The method includes sequentially focusing laser light at different focuses along a line within the laminated glass structure. The sequentially formed focuses define corresponding micro-volumes from which fluorescent light emanates due to a multiphoton process. The variation in the intensity of the detected fluorescent light from each micro-volume as a function of distance into the laminated glass structure is used to determine the relative locations of the multiple layers and the at least one gradual transition region.