Gretag Aktiengesellschaft

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Josef A Huber

Kurt Ehrat

Fred Mast

Ernst Huber

An elevating apparatus comprises a rack (1) supporting the apparatus, and an elevating platform (7) adjustable in height and suitably guided by at least one mast (8) or column. The mast (8) may be moved from a transport position into an operating position by having it pivoted about a horizontal tilting axis (9) on the rack (1). The axis (9) is arranged at the end of two parallel beams (2) of the rack (1) so as to enable the mast to be folded between these beams (2), thus practically requiring no additional space during transport.

Elevating apparatus

The differences between the scanned values of corresponding image points of a specimen and an original are formed by point-by-point scanning and comparison with an original. The difference values are subjected to a tone or shade correction, and then a weighting process and a minimum threshold correction. In the shade or tone correction, a mean value formed from the difference values in a specific surrounding area of the associated image point is subtracted from each difference value. The weighting process is effected individually for each image point and results in systematic errors and critical image zones not producing faulty assessments. The weighting factors are determined by statistical analysis of specimens which are assessed as good visually. The minimum threshold correction eleminates all those pre-treated difference values which are below a certain minimum threshold. The difference values of the points surrounding each image point are added algebraically with distance-dependent weighting to the remaining difference values of each image point. The resulting values are compared with a threshold value for each image point. If these values exceed the threshold value at least at one image point, the specimen is assessed as faulty.

Process for assessing the quality of a printed product

A method and apparatus for detecting printing faults or errors in a sample of printed material, such as a bank note, by determining the relative positions of corresponding text on the sample and each of a number of original bank notes, each having been printed by a different printing process used in printing the sample combining the text of the originals optically or electronically taking into account the positions of the text in the originals relative to the text on the sample resulting from superimposition of the text produced by each of the printing process used to produce each original, and comparing the text of the sample with the total combined text. The relative positions of corresponding text on the sample and originals is determined by scanning the sample and originals and obtaining reflectances values at each of a number of corresponding raster points and correlating the corresponding reflectance values to obtaining the relative position values.

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Zurich, Switzerland

Josef A Huber