In-process detection of laser-generated ultrasound for controlling material laser processing

An in-process monitoring of laser processing provides real-time feedback on the processing parameters. Thus, the optimal parameters for an unknown material can be determined with minimized prior measurements. Simultaneously measurements will reduce the processing time by allowing observation of the processed structure without the postprocessing. An acoustic method observes the deep site in optically opaque materials and is used in a complementary way to optical methods. In this research, laser drilling is controlled with the sound waves generated at a laser focusing point on and inside a target material. The axial position of the objective lens was controlled by the acquired excited sound, and the results of hole drilling according to changes in surface shape caused by ablation during processing are reported.