Fig. 1. (a) Experimental light path; (b) relationship between temporal contrast K and speed with ultra-short exposure time; relationship between contrast and speckle frame number under different speeds within (c) small speed range and (d) large speed range

Fig. 2. Relationship between Kd and N. (a) Small speed range; (b) large speed range

Fig. 3. Relationship between correlation coefficient C and frame index Nth. (a) Small speed range; (b) large speed range

Fig. 4. (a) Temporal contrast under different measured speeds; (b) relationship between K and N; (c) correlation coefficient of time sequence speckle image

Fig. 5. Relationship between Kd and Ns under different exposer time. (a) Short exposure time of 0.205 ms; (b) long exposure time of 10.75 ms