Fig. 1. Flow chart of wind turbine blade collision warning method based on the event camera

Fig. 2. Accumulated event frames according to monitoring frequency requirement

Fig. 3. Polarity of events generated by blade tip movement at the minimum clearance distance position

Fig. 4. Pseudo candidate blade tip distribution map

Fig. 5. Distance from blade tips to optical axis

Fig. 6. Three-dimensional scanning model diagram of wind turbine. (a) Front view; (b) left view

Fig. 7. Raw event stream output by the event camera

Fig. 8. Accumulated event frame results at different time intervals. (a) 1/30 s; (b) 1/100 s; (c) 1/500 s; (d) 1/1000 s ; (e) 1/5000 s;

Fig. 9. Comparison of event camera and optical camera outputs. (a) Optical camera captures the current frame; (b) accumulated event frames over 1/30 s time interval; (c) optical camera captures the next frame

Fig. 10. Optical camera image capture under harsh lighting conditions. (a) 100 ms exposure time; (b) minimum exposure time (50 ms)

Fig. 11. Event frames accumulated at intervals of 1/1000 s. (a) Blade at the same position in Fig. 10(a); (b) blade at the same position in Fig. 10(b)

Fig. 12. Accuracy verification of leaf tip coordinate extraction. (a) Precision displacement stage; (b) camera installation location

Fig. 13. Minimum clearance distance measured by the event camera and the optical camera