Laser photo-thermo-acoustic (PTA) frequency swept heterodyned lock-in depth profilometry imaging system

摘要

A method and apparatus for biomedical subsurface imaging and measurement of thickness, elastic and optical properties of industrial and biomedical materials based on laser Photo-Thermo-Acoustic (PTA) frequency-swept heterodyne depth profilometry, In particular, the invention relates to biomedical imaging and measure of tissue and tumour thickness, L, speed of sound, c_s, acoustic attenuation coefficient, γ, optical absorption coefficient, μ_a, and optical scattering coefficient, μ_s. The method and apparatus involves providing for a sample of the material to be characterized; irradiating the material for a selected period of time with an excitation waveform from a modulated optical excitation source wherein a photo-thermo-acoustic emission is responsively emitted from said solid; detecting said emitted photo-thermo-acoustic emission; processing the electronic signal to convert the frequency-domain signal into time-domain and perform depth profilometric imaging and determining thermoelastic and optical properties of the material sample.