Patent ID: 8286467

Claim:
A method for producing an image indicative of variations of a surface of an object, the steps comprising: a) positioning an ultrasonic transducer in spaced relationship over the surface of an object; b) operating the ultrasonic transducer to apply an acoustic force to the surface at a selected acoustic force frequency; c) sensing an acoustic emission field produced by the object in response to the applied acoustic force; d) repeating steps b) and c) while moving the ultrasonic transducer over the surface of the object; e) providing a calibration signal that indicates standing waves between the surface of the object and the ultrasonic transducer for a plurality of different distances between the surface of the object and the ultrasonic transducer; and f) producing an image indicative of variations of the surface of the object using the acoustic emission fields sensed in steps c) and d) and using the calibration signal provided in step e).