In this paper, a novel optical air-coupled ultrasound (O-ACU) technique is proposed. A wide broadband (100 KHz - 1 MHz) laser-acoustic based optical microphone worked as probe in an air-coupled ultrasound (ACU) system. The O-ACU modality was used to detect several CFRP and GFRP impacted laminates and the results were compared with the classical ACU modality. Infrared thermography, as an established reference technique, was used for the validation. Advanced image processing techniques were applied. Conclusively, O-ACU shows an obvious improvement in sensibility and resolution.

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Hai Zhang, Christian U. Grosse, Nicolas P. Avdelidis, Jan-Carl Grager, Stefano Sfarra, Clemente Ibarra-Castanedo, and Xavier P. V. Maldague, "A novel optical air-coupled ultrasound NDE sensing technique compared with infrared thermographic NDT on impacted composite materials," Proc. SPIE 10661, Thermosense: Thermal Infrared Applications XL, 106610X (Presented at SPIE Commercial + Scientific Sensing and Imaging: April 18, 2018; Published: 14 May 2018); https://doi.org/10.1117/12.2303494.