Fig. 1. Recording and reconstruction of digital holography

Fig. 2. Schematic diagram of the measurement equipment

Fig. 3. (a) Gas system; (b) Light path system. 1-Gas source, 2-Air filter, 3-Gas distributor, 4-Ball valve group, 5-Flowmeter group, 6-Aspirator, 7-Cyclone, 8-Chamber, 9-Ball valve, 10-Pressure gauge, 11-Sampling probe, 12-Pipe, 13-Sampled coal flow, 14-Dilution gas, 15 and 16-Protection gas, 17-Ejector gas, 18-Laser, 19-Attenuator, 20-Spatial filter, 21-Lens, 22-Camera, 23-Laser controller, 24-Synchronizer, 25-Computer

Fig. 4. (a) Framework of the software; (b) Flow chart of holograms processing

Fig. 5. On-site experiments

Fig. 6. (a) and (d) are typical holograms of coal powders from mill B and D; (b) and (e) are reconstructed images of (a) and (d), while the particle size information are plotted in (c) and (f) respectively

Fig. 7. and results obtained by different methods 不同方法得到的 和 结果

Fig. 8. Comparison of PSD of different methods. (a) Mill B; (b) Mill D

Fig. 9. Online monitoring of pulverized coal fineness within 1 hour