Characterization of spatial resolutions and imaging depth.
(A) Cross-sectional photoacoustic image of a single 7-μm carbon fiber. (B) Axial resolution and (C) lateral resolution obtained at an axial distance of 2.2 mm. (D) Axial and lateral resolutions at different axial distances. (E) Magnitude of photoacoustic signal produced by the single carbon fiber at different axial distances.