Patent ID: 8581602

Claim:
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 housing containing a first sensor including a microwave transmitter for producing a primary beam of microwave energy, a waveguide for directing said primary beam of microwave energy towards the target, and a detector for receiving microwave energy reflected from said target; an alignment system for producing a signal when the orientation between the beam of microwave energy and the target surface is at a predetermined angle; and an analyzer for determining the thickness of the coating on the substrate by measuring components of the reflected microwave energy when the orientation between the beam of microwave energy and the target surface is at the predetermined angle wherein the housing has a curved lower surface for contacting the target surface while the primary beam of microwave energy is directed toward the target and wherein the housing can be moved through a range of motion while the curved lower surface is in contact with the target surface so that the angle between the beam of microwave energy and the target varies through a range of angles, said range of angles including the predetermined angle; and wherein the alignment system comprises an illumination source for directing illumination towards the target surface and an optical detector for detecting illumination reflected from the target surface and wherein the alignment system is oriented so that when the housing is moved through said range of motion while in contact with the target surface, the optical detector detects a maximum amount of illumination reflected from the surface when the orientation between the beam of microwave energy and the target surface is at the predetermined angle.