1. System for monitoring painting quality of components, for example of motor-vehicle bodies, comprising at least one source of light for illuminating the components, at least one camera for inspecting the illuminated components and electronic means for processing the signals coming from the camera, wherein said system further comprises: a manipulator robot, carrying a monitoring head including both said source of light and said camera, with said source of light and said camera being maintained in a relatively fixed position with respect to each other, said robot being adapted to move the source of light and the camera with respect to the monitored component in a main direction of movement and according to a trajectory parallel to a surface of the component, so that such movement trajectory follows a profile corresponding to the profile of said surface of the component, and wherein: said source of light is adapted to emit a flat blade of light which impacts the monitored surface according to an illumination line, said illumination line being perpendicular to said main direction of movement, the plane of said blade of light forming an angle of incidence with respect to a plane which is perpendicular to the surface and passes through said line, said camera being positioned and oriented with respect to said source of light so that the optical axis of the camera impacts the monitored surface in a point of said illumination line and forms an angle with respect to the normal in said point on the monitored surface which is substantially equivalent to the abovementioned angle of incidence, so that said camera is capable of acquiring—by reflection—the image of the profile of the monitored surface along the intersection thereof with the blade of light emitted by said source of light, said system being characterized in that: said robot is adapted to maintain the source of light and the camera each at a constant distance from said surface of the component, said angle of incidence is comprised between 20° and 40°, and said source of light comprises an aligned series of white light LED sources, and an opaque shield arranged opposite said series of sources and having a rectilinear fissure parallel to said aligned series of sources.