Fig. 1. Schematic of experimental device

Fig. 2. Coal with smooth surface. (a) Fringe pattern; (b) background intensity; (c) binary image of coal and shadow; (d) binary image of valid measurement area

Fig. 3. Binary images of phase point distribution for two phase types of coal with smooth surface. (a) First type; (b) second type

Fig. 4. Phase distributions of coal with smooth surface. (a) First type of phase points before correction; (b) first type of phase points after correction; (c) second type of phase points before correction; (d) second type of phase points after correction

Fig. 5. Phase distribution of coal with smooth surface after correction

Fig. 6. Coal with non-smooth surface. (a) Fringe pattern; (b) background intensity; (c) binary image of valid measurement area

Fig. 7. Binary images of phase point distributions of two phase types of coal with non-smooth surface. (a) First type; (b) second type

Fig. 8. Phase distributions of coal with non-smooth surface after correction. (a) First type of phase points; (b) second type of phase points

Fig. 9. Phase distributions of coal with non-smooth surface after correction by different methods. (a) Proposed method; (b) method in Ref. [15]; (c) method in Ref. [16]; (d) method in Ref. [17]

Fig. 10. Cinder. (a) Background intensity; (b) phase distribution in valid measurement area after correction

Fig. 11. Point cloud of coal. (a) Smooth surface; (b) non-smooth surface

Fig. 12. Standard gauge block. (a) Fringe pattern; (b) 3D point cloud