Laser ultrasonics is a non-destructive testing technique where a focused laser is used for generating an ultrasound pulse and a second laser is used for detection. This ultrasound pulse is used for detecting surface or near surface defects. A defect will not only reflect the incoming surface wave, but also alter the frequency contents of the transmitted wave. When the detection laser was scanned along the surface, changes in frequency contents of the sound pulse were detected and could be analysed to give information about the diameter of the defect.