Patent ID: 7525661

Claim:
A method to perform operator-controlled slice-by-slice photo-thermo-acoustic imaging of a material through a coupling fluid, the method comprising the steps of: (a) irradiating the material at a given point for a selected period of time with an excitation waveform from an optical excitation source modulated by a linear chirp with frequency sweep producing frequency-swept modulation signals wherein frequency-swept photo-thermo-acoustic signals are responsively emitted from said material; (b) detecting said emitted frequency-swept photo-thermo-acoustic signals; (c) repeating steps a) and b) while scanning across a surface of the material along a pre-determined line or across a two-dimensional surface area of the material; and (d) electronic signal processing to convert the emitted frequency-domain photo-thermo-acoustic signals into time-domain and perform depth profilometric imaging at each point of the material while scanning to obtain thermoelastic and optical properties of the material at various subsurface depths and producing a two-dimensional slice image of subsurface structures when the scan is along said pre-determined line, or a three-dimensional volume image of subsurface structures when the scan is across said two-dimensional surface area of the sample material.