Fig. 1. Views of bubbles illuminated by light from different angles. (a) Main view; (b) top view; (c) left view; (d) left view of bubbles pass through optical path

Fig. 2. Simulation results of optical path without bubbles in liquid phase. (a) Optical path simulation; (b) geometrical circle energy distribution

Fig. 3. Simulation results of optical path with bubbles in liquid phase. (a) Lightpath simulation diagram; (b) geometrical circle energy distribution; (c) system energy attenuation under different bubbles' sizes

Fig. 4. Optical measurement system and optical transmission path. (a) Schematic of measuring system; (b) optical transmission path

Fig. 5. Bubble size measurement results. (a) Pictures of bubbles by high-speed camera; (b) response of the detection system to bubble size; (c) measurement results of bubble diameter

Fig. 6. Measurement results of bubble frequency. (a) Response of the system to bubble frequency; (b) measurement results of bubble frequency

Fig. 7. Measurement results of bubble movement velocity. (a) Pictures captured by high-speed camera at different time;(b) measurement results of bubble movement velocity