Fig. 1. Two kinds of representations of pixel eight-neighborhood. (a) Eight-neighborhood chain code representation; (b) eight-neighborhood coordinate representation

Fig. 2. Schematic of unilateral tracking search

Fig. 3. Schematics of candidate point search. (a) Chain code value of 0; (b) chain code value of 1; (c) chain code value of 2

Fig. 4. Flow chart of unilateral tracking

Fig. 5. Schematic of prediction with least square method

Fig. 6. Flow chart of line structured light center extraction algorithm based on unilateral tracking and midpoint prediction

Fig. 7. Experimental images. (a) Large curvature variation; (b) severe interference

Fig. 8. Local zoom of extraction result by each algorithm for large curvature change in Fig.7(a). (a) Geometric center algorithm; (b) gray gravity algorithm; (c) Steger algorithm; (d) proposed algorithm

Fig. 9. Extraction result by each algorithm for Fig.7(b). (a) Geometric center algorithm; (b) gray gravity algorithm; (c) Steger algorithm; (d) proposed algorithm

Fig. 10. Simulation of laser stripe with added noise

Fig. 11. Local zoom of extraction result by each algorithm. (a)(e) Geometric center algorithm; (b)(f) gray gravity algorithm; (c)(g) Steger algorithm; (d)(h) proposed algorithm

Fig. 12. Extracted result by each algorithm

Fig. 13. Measurement accuracy experiment. (a) 2 mm thick standard gauge block; (b) 5 mm thick standard gauge block; (c) 10 mm thick standard gauge block

Fig. 14. Measurement result and error of each algorithm. (a) Measurement result; (b) measurement error

Fig. 15. Extraction results of proposed algorithm for different kinds of laser stripes. (a) Folded line; (b) arc; (c) diagonal arc tangent; (d) continuous variation curve