Method and apparatus for nondestructive measuring of a coating thickness on a curved surface

An apparatus for nondestructive measurement of a property of a target, the target including a substrate and a coating on the substrate, and the property being the thickness of the coating, the apparatus comprising:

• a microwave transmitter for producing a primary beam of microwave energy;
• a waveguide for directing said primary beam of microwave energy towards the target;
• a detector for receiving microwave energy reflected from said target;
• an alignment system for determining when the orientation between the beam of microwave energy and the target surface is at a particular predetermined angle;
• and
• an analyzer for determining the thickness of the coating on the substrate based upon the reflected microwave energy received by the detector only when the alignment system determines that the orientation between the beam of microwave energy and the target surface is at the predetermined angle.