Fig. 1. Principle of curvature sensor based on Fresnel zone plate

Fig. 2. Flow chart of automatic spot location and extraction algorithm

Fig. 3. Experimental setup

Fig. 4. Experimental results of automatic spot location and extraction. (a) Original image; (b)binary image; (c) spot image 1; (d) spot image 2 (e) target spot 1; (f) target spot 2

Fig. 5. Wavefront restored by two sensors. (a) Wavefront 1 restored by CS; (b) wavefront 2 restored by CS; (c) wavefront 3 restored by CS; (d) wavefront 4 restored by CS; (e) wavefront 1 restored by HS; (f) wavefront 2 restored by HS; (g) wavefront 3 restored by HS; (h) wavefront 4 restored by HS

Fig. 6. Absolute deviation histogram of spot location. (a) D/r0=2; (b) D/r0=5; (c) D/r0=10; (d) D/r0=20