Fig. 1. Speckle correlation. (a) Speckle image; (b) correlation between single speckle and total speckles

Fig. 2. Schematics of speckle ranging principle. (a) When there is no occlusion in space; (b) occlusion object appears in space

Fig. 3. Schematic of speckle ranging principle when the measured object (G) is outside the standard reference plane

Fig. 4. Depth measurement algorithm overall flow

Fig. 5. Images obtained with different binarization methods. (a) Absolute threshold binarization; (b) local adaptive binarization

Fig. 6. Speckle center pixel before and after extraction. (a) Before extraction; (b) after extraction

Fig. 7. Schematics of window descriptor matching of the same speckle at different measurement distances

Fig. 8. Convolution process of speckle window descriptor and matching result. (a) Convolution process; (b) matching result

Fig. 9. Schematic of speckle ranging module

Fig. 10. Comparison of speckle images processed by absolute threshold binarization and adaptive threshold binarization. (a) Speckle image 1; (b) spekle image 2; (c) spekle image 3; (d) spekle image 4

Fig. 11. Number of speckle obtained by absolute threshold binarization and adaptive threshold binarization

Fig. 12. Effects of window size of descriptor on matching result. (a) Relationship between window size and number of speckle; (b) relationship between window size and error rate

Fig. 13. Depth map of a plane

Fig. 14. Accuracy of proposed algorithm and other algorithms