Fig. 1. Schematic of vessel passing through the probe beam region

Fig. 2. Schematic of the experimental system for measuring velocity of blood flow

Fig. 3. Blood flow velocity measured by PACS method. (a) Photoacoustic image of blood flow phantom; (b) normalized P(t) signal; (c) calculated and fitted autocorrelation curves of P(t)

Fig. 4. Calculated autocorrelation data and fitted curves at repetition frequency of 2 kHz and different velocities of blood flow. (a) 1 mm/s; (b) 2 mm/s; (c) 3 mm/s; (d) 4 mm/s; (e) 5 mm/s; (f) 6 mm/s

Fig. 5. Calculated autocorrelation data and fitted autocorrelation curves at velocity of blood flow of 2 mm/s and different laser repetition frequencies. (a) 0.5 kHz; (b) 1 kHz; (c) 2 kHz; (d) 3 kHz; (e) 4 kHz; (f) 5 kHz

Fig. 6. (a) Dependence of the flow time on the designed velocity and (b) the measured velocities versus the actual velocities

Fig. 7. Ratio between the measured flow velocity and the actual flow velocity at different tilt angles