Sausage casings are long, thin tubes used to wrap meet in sausage production. Such casings are made of collagen extracted from natural material. Production process may introduce some defects (e.g. perforation), but much more frequent and therefore problematic are unfiltered inclusions from the raw material. Those do not affect the quality or safety of the final product, but dark spots on some sausages do not look tasty.
The quality inspection system was installed just before the end of production process where the casings are cut in pieces and packed manually. A beacon light is used to inform the operator that a current batch has a defect.
The image shows a detected defect in see-through, grayscale image of a casing.