Giesecke+devrient Currency Technology Gmbh

Ulf Ehrhardt

Wolfgang Deckenbach

Martin Clara

A light source driver circuit has a switching regulator including a voltage input, a voltage output, and a regulation input; a current source with a switching element and a voltage-controllable member arranged in series with the light source load. A pulse signal is applied to a control terminal of the switching element to connect, in a first switching state of the switching element, a control terminal of the voltage-controllable member to a voltage source and in a second switching state of the switching element not to connect the control terminal of the voltage-controllable member to the voltage source; and a regulation unit. An optical measuring instrument includes a light source driver circuit, a device checks value documents with the light source driver circuit, and a method is provided for operating a light source load with the light source driver circuit.

Light source driver circuit, optical measuring device comprising the light source driver circuit, device for checking value documents, and method for operating a light source load by means of the light source driver circuit

A method and a sensor for checking documents are provided in which the same detector is used for a remission measurement and a luminescence measurement of the value document. The remission measurement value being detected during the illumination of the value document with an excitation light used for luminescence excitation, and the luminescence measurement value after switching off the illumination. In order to reduce a distortion of the remission measurement value by the luminescence, a spectral detection filter is incorporated into the detection ray path, which has a transmission of at least 0.5% in the spectral region of the excitation light. The increased transmission of the spectral detection filter achieves that the excitation intensity impinging on the detector far exceeds the luminescence intensity occurring simultaneously with the excitation and thus reduces the mentioned distortion.

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Munich, Germany

Ulf Ehrhardt