Abstract: A new method of Hough transform based on gradients phase grouping for branches detection was proposed to locate the position of branches of fruit trees accurately and rapidly. After the gradient phase of edge points was calcu- lated by using the squared gradient method, the histogram of gradicnts's direction was calculated. From the histogram, several peak values were found by threshold T. Then edge points were grouped according to their gradent phases, and points in each group almost had the same gradient's direction. At last, an improved two-points Hough transform was applied to edge points in each group to calculate the parameters of lines, and the gradent's direction of every group was used to affirm the correctness of the parameters. The research results show that the proposed method has the merits of high speed, low error and strong robustness, can locate the branches of fruit trees accurately and fastly, and also can de- feet part covered branches satisfactorily.

Key words: Phase grouping, Improved sobel operator, Histogram of gradient' s phrases, Squared gradient, Two points bough transform