A method for monitoring production processes having at least partly transparent products, wherein interior contaminants of the product are determined, said method comprising the steps: taking a first image of the product; calculating a first unfolded rotation result image (b) from the first image, with the calculation of the unfolded rotation result image (b) comprising the steps: mathematical cylindrical unfolding of the first image along an X axis, with an outer surface of the product along the X axis being evenly distributed over a result image (a) thus produced; and mathematical linear displacement of the result image (a) along the X axis in a negative direction, with the displacement corresponding to a rotation angle α of the product by which the product has to be rotated relative to a camera for taking the rotation image and with the processed rotation result image (b) being produced; turning the product and/or the camera toward one another to take the rotation image about the rotation angle α; taking a rotation image of the product; calculating a folded intermediate result image (c) from the rotation image, with the calculation of the unfolded intermediate result image (c) comprising the step: mathematical cylindrical unfolding of the rotation image along the X axis, with an outer surface of the product along the X axis being evenly imaged at the intermediate result image (c) thus being produced; subtracting the unfolded rotation result image (b) from the unfolded intermediate result image (c) to form a result image (d). taking a first image of the product; calculating a first unfolded rotation result image (b) from the first image, with the calculation of the unfolded rotation result image (b) comprising the steps: mathematical cylindrical unfolding of the first image along an X axis, with an outer surface of the product along the X axis being evenly distributed over a result image (a) thus produced; and mathematical linear displacement of the result image (a) along the X axis in a negative direction, with the displacement corresponding to a rotation angle α of the product by which the product has to be rotated relative to a camera for taking the rotation image and with the processed rotation result image (b) being produced; mathematical cylindrical unfolding of the first image along an X axis, with an outer surface of the product along the X axis being evenly distributed over a result image (a) thus produced; and mathematical linear displacement of the result image (a) along the X axis in a negative direction, with the displacement corresponding to a rotation angle α of the product by which the product has to be rotated relative to a camera for taking the rotation image and with the processed rotation result image (b) being produced; turning the product and/or the camera toward one another to take the rotation image about the rotation angle α; taking a rotation image of the product; calculating a folded intermediate result image (c) from the rotation image, with the calculation of the unfolded intermediate result image (c) comprising the step: mathematical cylindrical unfolding of the rotation image along the X axis, with an outer surface of the product along the X axis being evenly imaged at the intermediate result image (c) thus being produced; subtracting the unfolded rotation result image (b) from the unfolded intermediate result image (c) to form a result image (d). mathematical cylindrical unfolding of the rotation image along the X axis, with an outer surface of the product along the X axis being evenly imaged at the intermediate result image (c) thus being produced; subtracting the unfolded rotation result image (b) from the unfolded intermediate result image (c) to form a result image (d).