Method and apparatus for detecting and inspecting through-penetrating defects in foils and films

Apparatus for optical detection and size evaluation of defects that penetrate completely through a moving foil or film, said apparatus comprising,

• at least one image capture device and at least one elongated light source comprising an infinite number of point sources that are not in phase and are which emit light independently from one another, wherein said optical image capture device is positioned so as to be on one side a first surface of a foil or film, when present in said apparatus, and at a first distance from said first surface and said elongated light source is positioned on a second opposite side of said of said foil or film, when present in said apparatus;
• transportation means for moving the image capture device along a line normal to the surface of the foil or film;
• transportation means for moving the image capture device in a plane parallel to the surface of the foil or film;
• means of stopping the movement of the foil or film;
• and
• a computer comprising (i) at least one processor, (ii) a memory, and (iii) at least one program, wherein the at least one program is stored in the memory and executable by the at least one processor, the at least one program comprising instructions to control:
• the passing of a flat foil or film between the at least one optical image capture device and the at least one elongated light source,
• the periodic capturing of images of the foil surface with said image capture device to produce at least a first image;
• the transmission of said at least first image to the computer;
• the processing of the transmitted first image to detect whether a first light spot image associated with a defect is present and, if present, determining the brightness and area of the first light spot of said first light spot image;
• the calculating of a first generalized index of said first image by multiplying said brightness and said area of said first light spot image;
• the stopping of the movement of a foil or film upon detection of said first light spot image;
• the moving of the image capture device to a second distance from the foil or film surface;
• the repositioning of the image capture device in the plane parallel to foil or film surface;
• the stopping of the image capture device when the light spot of said defect comes into the focus;
• the automatic capturing of a second image
• the transmission of said second image to said computer;
• the processing of said second image to form a second light spot image determining the brightness and area of the second light spot of said second light spot image;
• the calculating of a second generalized index of said second image by multiplying said brightness and said area of said second light spot image;
• the calculating of a third generalized index using said first and second generalized indices;
• and
• the evaluation of the dimensions of said through defect in said foil or film by comparing the third generalized index with calibrated generalized indices.