Fig. 1. Schematic of extrapolated boundary

Fig. 2. Two-dimensional model of tissue. (a) Monolayer issue; (b) multi-layer tissue

Fig. 3. Propagation of ultrasound

Fig. 4. Mesh settings. (a) Mesh setting of monolayer tissue; (b) mesh setting of multi-layer tissue

Fig. 5. Three-dimensional distribution of fluence rate under different lengths of beams. (a) 0.1 cm; (b) 0.2 cm; (c) 0.4 cm; (d) 0.8 cm

Fig. 6. Characteristics of axial and radial light distribution. (a) Radial light distribution at different axial distances; (b) axial light distribution at different radial distances

Fig. 7. Modulation results of Hanning window ultrasound and sinusoidal ultrasound. (a)(d) Pressure curves at different points; (b)(e) fluence rate curves corresponding to each point; (c)(f) acousto-optical signals

Fig. 8. Schematic of acousto-optical imaging system

Fig. 9. Ultrasound waveform used in the experiment and measured acousto-optical signals. (a) Ultrasound waveform; (b) acousto-optical signal waveform obtained by oscilloscope

Fig. 10. Influence of optical parameters on acousto-optical signal in monolayer tissue. (a) Absorption coefficient μa; (b) scattering coefficient μs; (c) g

Fig. 11. Influence of optical parameters of non-target tissue on acousto-optical signal in multi-layer tissue. (a) μa2; (b) μs2; (c) μa1; (d) μs1

Fig. 12. Influence of optical parameters of target tissue on acousto-optical signal in multi-layer tissue. (a) μa1; (b) μs1; (c) μa2; (d) μs2