Fig. 1. Spectrograms of two images. (a)(b) Spectrograms in polar coordinate system; (c)(d) spectrograms in rectangular coordinate syatem

Fig. 2. Two images to be registered with only relative translation

Fig. 3. Diagram of improved mesh matching algorithm

Fig. 4. Relative position of two images to be registered when value of function S is the smallest

Fig. 5. Registered images of two images with inconspicuous features. (a) Gray difference mean value of overlapped area is 6.4564×10^-4; (b) gray difference mean value of overlapped area is 8.0699×10^-4

Fig. 6. Two images to be registered

Fig. 7. Spectrograms of two images. (a)(b) Spectrograms in polar coordinate system; (c)(d) spectrograms in rectangular coordinate system

Fig. 8. Similarity curve of two spectrograms in rectangular coordinate system obtained by SAD

Fig. 9. Gray level difference curves obtained by coarse matching and fine matching of SAD. (a) Coarse matching; (b) fine matching

Fig. 10. Images after coordinate transformation. (a) Image after registration of two images; (b) image after continuous mosaic of multiple images