presented in fig6 the last step 38 f is to compare the value of g t against the threshold value and declare whether the pixel under examination is a potential edge pixel or not the method of this invention has several advantages one of the advantages is that the edge detection by the method of the present invention is not affected by the change of light intensity on the surface 24 or noise generated by the light source 22 over time this is particularly a problem when luminance generated by the light source 22 is affected by the environment for example if the edge detecting system 20 is installed in an automobile the heat generated by the automobile may reduce the light intensity output as shown in fig1 a and 10 b the directions of background gradient directions n at low light intensity and the direction of background gradient directions n u2032 at high light intensity remain mostly unchanged as a result the background gradient directions t at low light intensity and the background gradient directions t at high light intensity remain mostly unchanged as well therefore the method of detecting an edge of the object of the present invention is not affected by any changes of background light intensity fig1 shows another aspect of the edge detection system 20 according to one embodiment of the present invention in this aspect the edge detection system 20 comprises an initialization image capturing module.