Inspection of internal structures of objects by laser ultrasonics using photorefractive liquid crystals

Laser ultrasonics using a photorefractive liquid crystal was investigated in both coaxial and counter-optical setups. The proposed laser-ultrasonic method involves irradiating an object with a laser pulse to produce an ultrasonic vibration and then using another laser beam to detect the vibration. The phase of the laser beam reflected from the object is shifted by the ultrasonic vibration. By using liquid crystals with photorefractive properties, this phase shift can be detected. Compared to traditional laser ultrasonic methods, this system offers a simpler optical setup and provides more accurate measurements that are unaffected by environmental vibrations.