Method for verifying the state of a device used to examine sheet items
AssigneeGiesecke & Devrient GmbH
InventorsAchim Philipp, Heinz Hornung
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Abstract
The invention relates to a method for checking the state of an apparatus for testing sheet material having at least one illumination device, transparent measuring window and detector. For ascertaining the soiling of a measuring window according to the invention the latter is irradiated with UV light by an illumination device, the UV light transmitted through the measuring window being filtered by a UV filter such that only a small fraction passes the filter and reaches a detector. Said fraction of UV light transmitted through the filter is detected and evaluated for determining the degree of soiling of the measuring window.
Claims8
A method for determining the degree of soiling of a transparent measuring window of an apparatus for testing a sheet material, said apparatus including at least one illumination device, a UV filter and a detector, said method comprising the following steps of:
- irradiating the measuring window with UV light;
- filtering the UV light transmitted by the measuring window with said UV filter such that only a small fraction of UV light is passed therethrough towards the detector;
- measuring the amount of UV light transmitted by the UV filter to produce a measured value;
- and
- comparing the measured value with a stored reference value.
Dependencies are inferred from the claim text.