| CPC G07D 7/121 (2013.01) [G01N 21/55 (2013.01); G01N 2021/558 (2013.01); G01N 2201/121 (2013.01); G01N 2201/1211 (2013.01); G01N 2201/12707 (2013.01)] | 17 Claims |
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15. An optical sensor for checking a value document, which is introduced into a capture range of the optical sensor for its checking, wherein the optical sensor has:
a photodetector line, which has a number K of several detector elements arranged next to one another, which are configured to detect in each case an intensity of light emanating from a detection region of the value document,
a line of light sources, which has a number N of several light sources arranged next to one another, which are configured to illuminate the value document,
a monitor detector line, which has several photosensitive monitor elements arranged next to one another, wherein each monitor element is assigned to one of the light sources and is configured to detect an intensity MSj of light emitted by this light source and impinging on the respective monitor element,
a control device which is adapted to
switch on the N light sources simultaneously for the check of the value document in order to illuminate the value document with the light from the light sources, and to control the detector elements of the photodetector line in such a manner that these detector elements record measured values of the value document that correspond to light intensity emanating from the value document as a result of the illumination, wherein the K detector elements each record a measured value Di of the value document, wherein i=1 . . . K, and
carry out a self-test of the optical sensor, in which the N light sources are switched on and, with the aid of the monitor elements, the respective light intensity MSj of the light source assigned to the respective monitor element is detected, which impinges on the respective monitor element at a time of the self-test, in order to verify the light intensities MSj detected by the monitor elements at the time of the self-test, wherein j=1 . . . N,
an evaluation device which is adapted to
correct the measured values Di of the value document based on the light intensities MSj detected by the monitor elements at the time of the self-test, wherein, when correcting, the measured value Di of the respective detector element is corrected in each case with a correction factor FKi, which is computed individually for the respective detector element based on the light intensities MSj detected by several of the monitor elements at the time of the self-test, and
check the value document based on the measured values corrected with the aid of the respective correction factor FKi.
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