Fig. 1. Principle diagram of hot image formation

Fig. 2. Distribution of phase defect

Fig. 3. Spatial distribution of beam with defect point. (a) Intensity on beam propagation axis (b) intensity on hot image screen; (c) intensity on hot image screen with a shadow in nonlinear medium

Fig. 4. Optical schematic of band-pass imaging

Fig. 5. Spatial frequency spectra of 16 phase defects

Fig. 6. Three optical types applied to calculate the hot image intensity. (a) Optical type 1; (b) optical type 2; (c) optical type 3

Fig. 7. Linear fitting of hot image relative intensity and relative brightness of defect filtered by band-pass window function in type 1

Fig. 8. Linear fitting of hot image relative intensity and relative brightness with the optimal band-pass window for the different optical types. (a) Optical type 1; (b) optical type 2; (c) optical type 3