In order to find the threshold of Otsu rule rapidly

a modifying strategy to the inertia weight in particle swarm optimization(PSO)is introduced. This makes the inertia weight being updated by the distance between the best position of the individual particle and the globally best position. With the reduction of the distance between the globally best position and the individual best position

the inertia weight of the individual particle would be reduced

vice versa. The comparison results with other methods indicate that this algorithm has less computational work and a fast convergence.