A laser ultrasonic inspection apparatus and method which enables remote
sensing of thickness, hardness, temperature and/or internal defect
detection is disclosed. A laser generator impinges a workpiece with light
for generating a thermo-elastic acoustic reaction in a workpiece. A probe
laser impinges the workpiece with an annularly-shaped probe light for
interaction with the acoustic signal in the workpiece resulting in a
modulated return beam. A photodetector having a sensitive region for
detecting an annularly-shaped fringe pattern generated by an interaction
of a reference signal and with the modulated return beam at said
sensitive region.