Figure 4

Differentiated A-line strategy and A-line number verification for IVPA-US imaging at 16 fps. (a) Timing diagram of IVPA-US imaging. \({\tau }_{0}\), 0 µs; \({\tau }_{1}\), 0.126 µs; \({\tau }_{2}\), 8.126 µs; \({\tau }_{3}\), 258.126 µs. TTL trigger refers to the trigger signal from laser. (b) Cross-sectional IVPA image of a single carbon fiber with diameter of 30 µm for spatial resolution characterization. The image shown was reconstructed by raw imaging data without A-line interpolation. Inset shows the zoom-in IVPA image. Scale bar: 1 mm. (c) Lateral plot of the carbon fiber in IVPA image at an axial position of 2.38 mm. The lateral resolution of 305 µm is estimated by the full with at half maximum (FWHM) of Gaussian fitted curve. (d) IVPA lateral resolution at different axial position at imaging speeds of 1, 5, 10, and 16 fps.