Patent ID: 8322220

Claim:
A method of imaging sub-surface features of a sample, the method comprising the steps of: providing a scanning probe microscope (SPM), the SPM including a probe having a cantilever bearing a tip; providing an ultrasonic source that directs ultrasonic energy into the sample; coupling the ultrasonic energy from the ultrasonic source into a section of the sample at a first position; using the probe to detect an interaction between the incident ultrasonic energy and a sub-surface feature of the sample; successively moving at least one of the sample and the ultrasonic source with a translation stage to generate relative motion between the ultrasonic source and the sample so as to couple ultrasonic energy into different sections of the sample; and further including providing a second ultrasonic source coupled to the probe that produces an ultrasonic drive wave so as to create a beat signal having a beat frequency, thereby down converting the detected interaction.