A method of analysis and automatic visual inspection system has been developed through digital images which operate on-line in the detection of disparities in plain surfaces, preferably plates over a transportation belt. The objective of the system is to classify the surfaces of the plates in surfaces free of disparities and surfaces with disparities. The information necessary to determine the difference between the plates is given by the color and texture of the surface under inspection. The plain surface (2) of the plate, is entirely and homogeneously lit by a Fresnel type spotlight (1). An image of each face of the plate is obtained by digital CCD cameras (3) and (4). This digital signal is sent to a frame buffer in a frame grabber (6). A series of algorithms, for the processing of digital images, enhances the details of the plate's surface image for its further analysis. The final image is analyzed by a processor (5) obtaining an indicative parameter of the physical quality of said plate.