A nonlinear HVS operator to detect gray edge was presented in this paper. It’ s more accurate than normal linear edge detect operator when the difference of light intensity in the edge field is small. Further more

in this operator

the theory about HVS edge feeling of bright and dark was conformed to the theory of HVS response function to light intensity-the logarithmic function. The results of several experiments were consistent with the feeling of HVS. And normal linear operator couldn’t successfully detect the edge of the image used in these experiments.