Mukherjee, Jayanta, Das, S. and Chatterji, B.N. (1992):
Thresholding for Edge Extraction of Intensity Images,
Indian Journal of Engineering, Vol. 22, N0. 3, 20-29.  Abstract. 
A simple technique for the thresholding of edges of an intensity image is presented. This scheme is adaptive in its approach to the different variations of contrasts and gray level ranges within an image. The algorithm is simple and fast and produces satisfactory results on a wide variety of intensity images. The major advantage of the work is that the algorithm does not require any prior overall information of the gradient picture for thresholding and hence is usable as an on-line process.