Method and sensor for testing documents

Patent metadata

Field	Value
Publication number	US-11756362-B2
Application number	US-201916973611-A
Country	US
Kind code	B2
Filing date	Jun 17, 2019
Priority date	Jun 20, 2018
Publication date	Sep 12, 2023
Grant date	Sep 12, 2023

Abstract

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.

First claim

The invention claimed is:

1. A sensor for checking the authenticity of documents, comprising:
an illumination device for illuminating a document with one or several excitation light pulses of an excitation light which is suitable to excite the document to emit luminescent light; and
a detector for detecting at least one remission measurement value of the document and at least one luminescence measurement value of the document; and
a detection filter which is located in a detection ray path formed between the document and the detector; and
a control device for controlling the illumination device and the detector, wherein the control device is arranged to drive the detector such that the detector detects at least one remission measurement value of the document at at least one point in time at which the document is illuminated with an excitation light pulse of the excitation light, and detects at least one luminescence measurement value of the document at at least one point in time after the end of the respective excitation light pulse;
an evaluation device for checking the document on the basis of the at least one remission measurement value detected by the detector and on the basis of the at least one luminescence measurement value detected by the detector;
wherein the detection filter is a spectral detection filter whose spectral transmission is selected such that both the luminescent light of the document impinging on the spectral detection filter and at least 0.5% of the excitation light impinging on the spectral detection filter are transmitted through the spectral detection filter;
wherein the remission of the excitation light irradiated for the luminescence measurement is detected for the at least one remission measurement value.

2. The sensor according to claim 1 , wherein the spectral transmission of the spectral detection filter is selected such that at least 80% of the luminescent light of the document impinging on the spectral detection filter is transmitted through the spectral detection filter.

3. The sensor according to claim 1 , wherein a maximum transmission which the spectral detection filter has in the spectral region of the luminescent light is greater by at least a factor of 4 than a maximum transmission which the spectral detection filter has in the spectral region of the excitation light.

4. The sensor according to claim 1 , wherein the spectral detection filter has a transmission spectrum which has a spectral luminescence transmission band in the spectral region of the luminescent light of the document and at least one additional spectral transmission band in the spectral region of the excitation light.

5. The sensor according to claim 4 , wherein the at least one additional transmission band spectrally overlaps with the excitation light or spectrally completely encloses the excitation light.

6. The sensor according to claim 4 , wherein the spectral detection filter has a greater transmission in its luminescence transmission band than in its at least one additional transmission band.

7. The sensor according to claim 4 , wherein the additional transmission band has a spectral distance from the luminescence transmission band of at least 10 nm.

8. The sensor according to claim 4 , wherein the excitation light has a spectral excitation band with an upper spectral flank and a lower spectral flank, and the spectral detection filter has a first additional spectral transmission band, which lies spectrally in the lower spectral flank of the excitation band and has a second additional spectral transmission band which lies spectrally in the upper spectral flank of the excitation band.

9. The sensor according to claim 1 , wherein the control device is arranged to drive the detector, or an electronic circuit connected therewith such that the respective remission measurement value is measured with lower sensitivity than the respective luminescence measurement value.

10. The sensor according to claim 9 , wherein the control device is arranged to switch over a sensitivity setting of the detector or of an amplifier connected with the detector or of a current-voltage converter connected with the detector in the time period between the detection of the respective remission measurement value and the respective luminescence measurement value such that the remission measurement value is measured with lower sensitivity than the luminescence measurement value.

11. The sensor according to claim 1 , wherein the detector is a semiconductor-based detector with a charge carrier lifetime of at most 20 μs.

12. An apparatus for checking a document with a sensor according to claim 1 .

13. The apparatus according to claim 12 having a transport device which is arranged to transport the document and the detector relative to each other during the detection of the remission and luminescence measurement value, wherein the control device of the sensor is arranged to drive the detector such that the respective remission measurement value and the respective luminescence measurement value are detected with such a short time interval between each other that the detection regions on the document, from which the respective remission measurement value and the respective luminescence measurement value are detected, overlap by at least 50%.

14. A method for checking the authenticity of the documents, comprising the steps of:
illuminating a document with one or several excitation light pulses of an excitation light which is suitable to excite the document to emit luminescent light;
detecting at least one remission measurement value of the document at at least one point in time at which the document is illuminated with an excitation light pulse of the excitation light, by means of a detector;
detecting at least one luminescence measurement value of the document at at least one point in time after the end of the respective excitation light pulse by means of the detector;
checking the document on the basis of the at least one remission measurement value detected by the detector and on the basis of the at least one luminescence measurement value detected by the detector;
wherein in a detection ray path formed between the document and the detector there is located a spectral detection filter whose spectral transmission is selected such that both the luminescent light of the document impinging on the spectral detection filter and at least 0.5% of the excitation light impinging on the spectral detection filter, which has been remitted by the document, is transmitted through the spectral detection filter;
wherein the remission of the excitation light irradiated for the luminescence measurement is detected for the at least one remission measurement value.

15. The method according to claim 14 , wherein the document and detector are transported relative to each other during detection and that the remission measurement value and the luminescence measurement value are detected with such a small-time interval between each other that the detection regions on the document, from which the respective remission measurement value and the respective luminescence measurement value are detected, overlap by at least 50%.

16. A sensor for checking the authenticity of documents, comprising:
an illumination device for illuminating a document with one or several excitation light pulses of an excitation light which is suitable to excite the document to emit luminescent light; and
a detector for detecting at least one remission measurement value of the document and at least one luminescence measurement value of the document; and
a detection filter whi

Assignees

• Giesecke & Devrient Currency Technology Gmbh

Inventors

• Deckenbach Wolfgang
• Danhof Julia
• Ehrhardt Ulf
• Clara Martin

Classifications

• G07D7/1205 Primary

  Testing spectral properties · CPC title

• G07D7/121

  Apparatus characterised by sensor details · CPC title