Differential fibre-optic sensor for the monitoring of ultrasound

摘要

Knife-edge and differential optical beam deflection (OBD) techniques are capable of non-contact broadband measurement of laser-generated ultrasound. We describe a fibre-optic sensor based on both knife-edge and differential schemes, which has an angular deflection sensitivity of approximately equals 1 μrad. This sensitivity was sufficient to detect a Rayleigh wave propagating along various metal surfaces and Rayleigh waves reflected from artificial slot and fatigue crack defects. Further studies with the sensor have shown that it is capable of detecting defects in thin aluminum samples using mode converted laser-generated Lamb waves.