Process and device for inspecting transparent material

Method for inspecting transparent material by illumination by means of at least one light source, and by observation of the thickness of the material by at least one camera characterized comprising the steps of:

• uniformly illuminating with a first light source a bright background placed relative to the camera behind the material to be viewed by transparency through the material covering the field of view of the camera and serving as contrast reference:
• laterally illuminating with a second light source the surface of the material by grazing said surface without substantially penetrating said material in order to distinguish defects included within the material from parasitic elements deposited on its surface and diffracting light;
• viewing by transparency by the camera, placed in the vertical to the surface of the material, a sequence of contrasted images reproducing the thickness of the material;
• and
• processing information acquired by the successive images which are representative of the material seen in its thickness, to detect and locate the defects included within the thickness of the material corresponding to dark spots on the image.