Abstract: A laser-based technique to determine glass thickness employs a pulsed laser to induce an ultrasonic wave between the surfaces of a region of glass, causing the surfaces to move in and out at a characteristic frequency. The surface motion is monitored to determine the characteristic frequency, which is proportional to the thickness of the glass in the region of the ultrasonic wave. The pulsed laser produces a short duration pulse that illuminates a surface of the glass, which is absorbed within the glass to cause a rapid thermal expansion that generates the ultrasonic wave. The surface motion induced by the ultrasonic wave is preferably detected with a laser interferometer system, the output of which is analyzed to determine the surface motion's characteristic frequency.