Device and method for verifying feature substances

• US 10,417,856 B2
• Filed: 12/16/2015
• Issued: 09/17/2019
• Est. Priority Date: 12/16/2014
• Status: Active Grant

• Current Assignee: Giesecke & Devrient (Giesecke & Devrient GmbH)
• Original Assignee: Giesecke & Devrient GmbH
• Inventors: Clara, Martin, Giering, Thomas, Kecht, Johann, Rauscher, Wolfgang, Stark, Martin, Happ, Thomas
• Primary Examiner(s): Ayub, Hina F
• Assistant Examiner(s): Merlino, Amanda
• Application Number:
  US15/536,917
• Publication Number:
  US 20170358163A1
• Time in Patent Office: 1,371 Days
• CPC Class Codes: G01N 21/65 Raman scattering
• CPC Class Codes: G01N 21/658 enhancement Raman, e.g. surface plasmons
• CPC Class Codes: G07D 7/1205 Testing spectral properties

Abstract

The invention relates to an apparatus and a method for checking value documents marked with feature substances, and to the corresponding feature substances. The feature substances are detected on the basis of Raman or SERS spectroscopy also at high transport speeds with a spatial resolution in the low millimeter region or better and reliably identified.

Claims

1. A sensor for the machine check of moved value documents having at least one Raman or SERS or SERRS security feature, wherein, for checking, the sensor is configured to illuminate the value document with excitation light from a laser source and to disperse a resulting Raman light of the security features in a spectrometer and to capture it with spectral resolution with a detector having several spectral channels;

wherein the light from the same areal region of the value document collected in the spectral channels is captured synchronously by the detector and measurement signals corresponding to the spectral channels are formed; and

wherein scattered excitation light emanating from the value document is coupled via a slit module into the spectrometer such that Rayleigh-scattered excitation light is re-imaged onto an entrance slit, wherein the slit module has an absorption element which absorbs the Rayleigh-scattered excitation light at least partly.

2. The sensor according to claim 1, wherein the synchronous capture of the spectral channels is effected within less than 500 μ

s.

3. The sensor according to claim 1, wherein the sensor has a spatial resolution in a moving direction of less than 12 mm.

4. The sensor according to claim 1 wherein the spectral channels are read out in parallel at the same time.

5. The sensor according to claim 1, wherein the sensor has less than 100 spectral channels.

6. The sensor according to claim 1, wherein the excitation light of an excitation laser directs via a beam splitter inclined toward a main beam path in the direction of the value document to be checked, wherein the beam splitter is configured as an edge filter for the selective reflection of the excitation light.

7. The sensor according to claim 1, wherein the scattered excitation light emanating from the value document is coupled via the slit module into the spectrometer, wherein the slit module has a detector element for monitoring power and/or wavelength of the Rayleigh-scattered excitation light.

8. The sensor according to claim 1, wherein a power of the excitation light is selected in dependence on a measured remission signal.

9. The sensor according to claim 1, wherein a power of the excitation light is reduced, when a measured remission is smaller than a threshold value or the measured remission does not change over several measurement cycles.

10. The sensor according to claim 1, wherein the sensor further has an evaluation unit which determines from the measurement signals corresponding to the spectral channels a background portion and subtracts this from the measurement signals to generate background-corrected measurement signals, wherein the background portion is determined with the help of a moving percentile from intensity values or with the help of the intensity values in predetermined spectral channels.

11. The sensor according to claim 1, wherein, for checking, the sensor is configured to further illuminate the value document with excitation light from a second laser source and to disperse resulting Raman light of the security features in the spectrometer and to capture it with spectral resolution with the detector having several spectral channels.

12. The sensor according to claim 1, wherein the sensor is configured to illuminate the value document with a laser line at a first wavelength and alternating thereto with two laser lines having a spectral distance of 1-50 nm.

13. The sensor according to claim 1, wherein the sensor is suitable for distinguishing and identifying a coding with feature substances, wherein the feature substances comprise marker molecules, wherein the marker molecules have strong Raman signals in one or several spectral regions with a respective spectral distance of more than 50 cm⁻

1.

14. A method for the machine check of value documents having at least one Raman or SERS or SERRS security feature by means of a sensor, wherein

during the check, the value document is moved relative to the sensor at high speed,

for checking, the value document is illuminated with excitation light from a laser source,

resulting Raman light of the security features is dispersed in a spectrometer,

is captured with spectral resolution with a detector having several spectral channels,

measurement signals corresponding to the spectral channels are formed, wherein the light from the same areal region of the value document collected in the spectral channels is captured synchronously by the detector and spatially resolved measurement signals are formed by repeated measurement, and

the scattered excitation light emanating from the value document is coupled via a slit module into the spectrometer such that Rayleigh-scattered excitation light is re-imaged onto the entrance slit, wherein the slit module has an absorption element which absorbs the Rayleigh-scattered excitation light at least partly.

15. The method according to claim 14, wherein in the measurement signals corresponding to the spectral channels a background portion is determined from intensity values with the help of a moving percentile, or determined with the help of the intensity values in predetermined spectral channels and interpolated by a polynomial and subtracted from the intensity values and hence background-corrected measurement values are calculated.

16. The method according to claim 15, wherein a numerical classification of the background-corrected measurement values is carried out.

17. The method according to claim 14, wherein an authenticity recognition of the value document is carried out by a verification algorithm which is based on the calculation of a similarity measure between a measured spectrum and a reference spectrum.

18. The method according to claim 17, wherein a spectral shift of intensity values within a predetermined region is corrected or is tolerated upon the authenticity recognition.