Advantages and disadvantages of various techniques for the visualization of watermarks

This paper discusses the technical difficulties which may be encountered in the visualization indispensable in the localization and dating of papers and the investigation of watermarks. Modern digital techniques for visualizing obscured watermarks in historical documents are discussed. The advantages and disadvantages of the various digital methods will be presented and special attention will be devoted to the discriminating between writings and drawings and the underlying watermarks. As a new diagnostic method the use of heat radiation in the medium and long infrared spectrum is suggested: this creates an image of heat transmission in the medium due to the different densities and thickness variations in the paper. This type of recording is ecological, conservational and presents no health risks to the persons concerned. It can also be documented and communicated for any purpose with little expenditure of time and at high resolution

Detection of foreign substances in food using thermography

This paper gives a short introduction into the possibility of detecting foreign bodies in food by using IR thermography. The first results shown for combinations of cherries and chocolate and berries contaminated with leaves, stalks, pedicel and thorns could be easily evaluated manually. Therefore the differing emissivity coefficients or the different heat conductivities and/or capacities are used for differentiation. Applying pulse thermography, first heat conductivity measurements of different food materials are performed. Calculating the contrast of possible food/contaminant combinations shows the difficulty of differentiating certain materials. A possible automatic evaluation for raisins contaminated with wooden sticks and almonds blended with stones could be shown. The power of special adapted algorithms using statistical or morphological analysis is shown to distinguish the foreign bodies from the foodstuff

Wasserzeichendarstellung mit Hilfe der Thermographie

The contribution deals with the technical difficulties during the visualization indispensable for the localization and dating of papers and the investigation of watermarks, existing so far. The traditionally used optical and haptic techniques and the methods with exited energy as well as the relevant employment of the data and image processing are discussed. As a new method the use of heat radiation is suggested producing an illustration of the heat transmission in the diagnostic survey due to the different densities in a paper sheet. This recording is effected ecologically, conservatory and for the persons concerned unobjectionable under health aspects and it can be documented and communicated at small expenditure of time for arbitrary purposes with high resolution

Detection of foreign bodies in food by thermal image processing

This paper deals with the problem of detection of foreign bodies in food. A new method for inspecting food samples is presented, using thermographic images to detect foreign bodies that are not detectable using conventional methods. At first, the basic background of thermography is given. Then, experiments to obtain well-contrasted thermographic images of different food and foreign bodies are discussed. The main part of the present paper introduces specific Image processing methods that show a good recognition power of foreign bodies within food. Results achieved with a small set of test images are presented. The results are promising and the methods work even an some poorly contrasted images. To compare the different image processing and recognition methods, a quality index is defined. On the test Images the success of the presented methods is shown and the difference in recognition results can be measured using the introduced quality Index