Fig. 1. Basic principle diagram of DIC

Fig. 2. Diagram of climbing method

Fig. 3. Diagram of eight adjacent points

Fig. 4. Flow chart of improved climbing method

Fig. 5. Serial displacement images. (a) Reference map; (b) 1--50 pixel displacement

Fig. 6. Research results of traditional climbing method

Fig. 7. Research results of improved climbing method

Fig. 8. Influence of step-size change coefficient S on search time. (a) Displacement is 25 pixel; (b) subarea size is 51 pixel×51 pixel

Fig. 9. Influence of measured displacement on search time. (a) Sub area size is 51 pixel×51 pixel; (b) S=9