Sensor and method for checking value documents, in particular bank notes, and value document processing apparatus

Patent metadata

Field	Value
Publication number	US-12266233-B2
Application number	US-202118017355-A
Country	US
Kind code	B2
Filing date	Jul 8, 2021
Priority date	Jul 23, 2020
Publication date	Apr 1, 2025
Grant date	Apr 1, 2025

Abstract

A sensor and a method for checking value documents are provided, each having a luminescent sheet-like substrate and a luminescent feature applied to a partial surface of the substrate, and to a value document processing apparatus. From the spectral vectors obtained for a plurality of measurement points and characterizing the intensity of the luminescent radiation of the value document detected in at least two spectral ranges, substrate intensity values and feature intensity values are determined, based on which a pure substrate mask is determined, which contains only those measurement points which reliably lie outside the feature. From the spectral vectors of the measurement points contained in the pure substrate mask, a mean substrate vector is determined, based on which corrected substrate intensity values and corrected feature intensity values and/or a spectral signature of the substrate and/or of the feature are or is, respectively, determined from the spectral vectors.

First claim

The invention claimed is:

1. A sensor for checking value documents, in particular banknotes, each having a luminescent sheet-like substrate and a luminescent feature applied to a partial surface of the substrate, comprising:
a detection device which is configured to detect luminescence radiation emitted by a value document to be checked in at least two different spectral ranges in a spatially resolved manner,
wherein a plurality of measurement points is obtained, to each of which a spectral vector is assigned which contains at least two intensity values which characterize the intensity of the luminescence radiation detected at the respective measurement point in the at least two spectral ranges, and
an evaluation device which is configured
a) to determine, for each of a plurality of measurement points, a substrate intensity value and a feature intensity value from the spectral vectors using a predetermined substrate basis vector and a predetermined feature basis vector, the substrate basis vector and the feature basis vector each having at least two intensity values, which characterize the expected intensity of the luminescence radiation emitted by the substrate or feature, respectively, in the at least two spectral regions,
b) to determine, on the basis of the substrate intensity values and feature intensity values, a pure substrate mask which contains those measurement points which correspond to locations on the value document which lie outside the feature, and
c1) to determine, from the spectral vectors of the measurement points contained in the pure substrate mask, a mean substrate vector which contains at least two intensity values which are obtained in each case by combining, in particular by averaging or quantile formation, the intensity values contained in the spectral vectors for each of the at least two spectral ranges, and
i) to determine, for each of a plurality of measurement points, a corrected feature intensity value and/or a corrected substrate intensity value from the spectral vectors using the mean substrate vector, and/or
ii) to determine a spectral signature of the substrate and/or a spectral signature of the feature, by which a spectral composition of the luminescence radiation emitted by the substrate or the feature, respectively, is characterized, using the mean substrate vector, and/or
c2) to determine a temporal behavior of the luminescence radiation emitted by the substrate and/or the feature using measurement points contained in the pure substrate mask, and
d) to check, in particular with regard to authenticity, the value document on the basis of the corrected feature intensity values and/or on the basis of the corrected substrate intensity values and/or on the basis of the spectral signature of the substrate and/or of the feature and/or on the basis of the temporal behavior of the luminescence radiation emitted by the substrate and/or by the feature.

2. The sensor according to claim 1 , wherein the evaluation device is configured to correct the predetermined substrate basis vector using the mean substrate vector or to replace the predetermined substrate basis vector with the mean substrate vector,
wherein a corrected substrate basis vector is obtained.

3. The sensor according to claim 1 , wherein the evaluation device is configured to compare the mean substrate vector with the predetermined substrate basis vector using a predetermined comparison criterion, and,
if the comparison criterion is met, to correct the substrate basis vector using the mean substrate vector or to replace the substrate basis vector with the mean substrate vector, and/or
if the comparison criterion is not met, to classify the value document as a value document to be rejected.

4. The sensor according to claim 1 , wherein the evaluation device is configured to,
to determine, on the basis of the feature intensity values, a feature mask which contains those measurement points which correspond to locations lying on the feature,
subtract the mean substrate vector from each of the spectral vectors of the measurement points contained in the feature mask,
wherein background-corrected spectral vectors of the measurement points contained in the feature mask are obtained, and
determine, from the background-corrected spectral vectors of the measurement points contained in the feature mask, a mean feature vector which contains at least two intensity values each of which being obtained by combining, in particular by averaging, the intensity values contained in the background-corrected spectral vectors for each of the at least two spectral ranges.

5. The sensor according to claim 4 , wherein the evaluation device is configured to correct the predetermined feature basis vector using the mean feature vector or to replace the predetermined feature basis vector with the mean feature vector,
wherein a corrected feature basis vector is obtained.

6. The sensor according to claim 2 , wherein the evaluation device is configured to determine the corrected substrate intensity values and corrected feature intensity values using the corrected substrate basis vector and the, in particular corrected, feature basis vector from the spectral vectors.

7. The sensor according to claim 1 , wherein the evaluation device is configured, for checking the value document, in particular with regard to authenticity,
to compare the corrected substrate intensity values of one or more measurement points or the intensity values of the mean substrate vector with one or more predetermined substrate intensity values, and/or
to compare the corrected feature intensity values of one or more measurement points or the intensity values of the mean feature vector with one or more predetermined feature intensity values.

8. The sensor according to claim 1 , wherein the evaluation device is configured:
to determine, when determining the spectral signature of the substrate, a, in particular scalar, signature value of the substrate from the at least two intensity values of the mean substrate vector, and/or
to determine, when determining the spectral signature of the feature, a, in particular scalar, signature value of the feature from the at least two intensity values of the mean feature vector,
wherein the evaluation device is in particular configured, for checking the value document, in particular with regard to authenticity, on the basis of the spectral signature of the substrate and/or on the basis of the spectral signature of the feature, to compare the signature value of the substrate and/or the signature value of the feature in each case with one or more predetermined comparison value(s) of the substrate or with one or more predetermined comparison value(s) of the feature, respectively.

9. The sensor of claim 8 , wherein, during checking, the check result “authentic” is assigned to the value document if the at least two intensity values of the mean substrate vector are above a threshold and the at least two intensity values of the mean feature vector are above the same or above another threshold, and the signature value of the feature and the signature value of the substrate are different from each other.

10. The sensor according to claim 1 , wherein the detection device is configured to detect the luminescence radiation emitted by the value document to be checked for a plurality of measurement points at two or more points in time,
wherein to each of the measurement points two or more intensity values are assigned which characterize the intensity of the luminescence radiation detected at the respective measurement point at the two or more points in time.

11. The sensor according to claim 10 , wherein the evaluation device is conf

Assignees

• Giesecke & Devrient Currency Technology Gmbh

Inventors

• Rauscher Wolfgang
• Deckenbach Wolfgang
• Danhof Julia
• Happ Thomas

Classifications

• G07D7/2008

  using pre-processing, e.g. de-blurring, averaging, normalisation or rotation · CPC title

• G07D7/2016

  using feature extraction, e.g. segmentation, edge detection or Hough-transformation · CPC title

• G07D7/205

  Matching spectral properties · CPC title

• G07D7/1205 Primary

  Testing spectral properties · CPC title