Edge detection is one of the most important techniques in image processing

it is often used in the field of image analysis and image recognition for many applications. Pan and King firstly presented an algorithm of edge detection based on fuzzy sets

this algorithm has been found for many successful applications in the area of pattern recognition and medical image procesing. In this paper

an improved algorithm of edge detection proposed by Pal and King is presented

and the approach of edge detection is also developed to be an automatic one. The steps of this approach can be summarized as follows:firstly

a threshold is selected in an image by using an automatic algorithm of thresholding; secondly

in order to extract the fuzzy property plane from the spatial domain

a new membership function based on the threshold is defined; thirdly

image enhancement is performed in the fuzzy domain by using fuzzy enhancement operator; then

the modified spatial domain is obtained; finally

the edge detection is executed using min or max operators. This algorithm is also extended to the edge detection of the multi-thresholds image. The effectiveness of the algorithm is experimentally demonstrated.