Author Affiliations
1School of Precision Instrument and Opto-Electronics Engineering, Tianjin University, Tianjin 300072, China2Key Laboratory of the Ministry of Education on Optoelectronic Information Technology, Tianjin University, Tianjin 300072, Chinashow less
Fig. 1. Process of detecting defocused speckle of irregular particles in IPI system
Fig. 2. Setup of simulated particle IPI system
Fig. 3. Autocorrelation analysis of irregular particle shape. (a) Simulated ice particle shape; (b) autocorrelation calculation result of (a); (c) defocused speckle in simulated particle IPI system; (d) 2D Fourier transform amplitude of (c) binarization result; (e) defocused speckle in experimental particle IPI system; (f) 2D Fourier transform amplitude of (e) binarization result
Fig. 4. Shape categories distribution and corresponding examples of ice particles in ICDC
Fig. 5. Training and testing processes of particle shape classification network
Fig. 6. Defocused speckle and correlation analysis of 5 ice particle shape categories
Fig. 7. Updating strategies of diffuser. (a) Rotating; (b) lateral translating; (c) longitudinal translating; (d) replacing
Fig. 8. Variation in speckle correlation after applying updating strategies
Fig. 9. Structure of DenseNet
Fig. 10. Training loss and accuracy curves of AlexNet, ResNet152, and DenseNet169
Fig. 11. Influence of defocused distance on classification accuracy. (a) Testing set classification accuracies at four different defocused distances; (b) confusion matrix of speckle testing set at defocused distance of 70 mm
Fig. 12. Speckle data at different bit depths. (a) 8 bit; (b) 2 bit; (c) 1 bit
Fig. 13. Influence of speckle bit depth on classification accuracy. (a) Testing set classification accuracies at different bit depths;(b) confusion matrix of 1 bit speckle testing set at defocused distance of 70 mm
Fig. 14. Influence of binarization threshold on classification accuracy of 1-bit speckle data. (a) Grayscale histogram of raw speckle and binarization thresholds. Inset: classification accuracies of speckle data under different thresholds; (b) 1-bit speckle and its sparsity corresponding to different grayscale thresholds
Fig. 15. Influence of speckle pattern size on classification accuracy of speckle data. (a) Speckle slices of different sizes; (b) testing set classification accuracies of different speckle pattern sizes
Network | AlexNet | ResNet152 | DenseNet169 |
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Training time /s | 3386.1 | 3581.5 | 1946.3 | Weight size /MB | 233.2 | 222.1 | 48.6 | Number of parameters /M | 61.0 | 60.2 | 27.2 |
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Table 1. Comparison of training parameters for AlexNet, ResNet152, and DenseNet169