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DE-102024136577-A1 - Security marking, reading device and reading procedure

DE102024136577A1DE 102024136577 A1DE102024136577 A1DE 102024136577A1DE-102024136577-A1

Abstract

The invention relates to a testing device for optically checking objects for authenticity, in particular for checking whether objects have a predetermined, machine-readable code-encompassing security marking with known fluorescence properties. The test device includes a lighting unit designed and arranged to illuminate an object to be tested with electromagnetic radiation - preferably light visible to the human eye - in a first, fluorescence-stimulating wavelength range. The test device comprises an area sensor with a plurality of light-sensitive sensor elements and an imaging optic which is designed and arranged to project an image of an object onto the area sensor, wherein the area sensor is designed to output an image signal representing an image projected onto the area sensor. The imaging optics comprise an optical filter in the form of a high-pass or low-pass filter, in particular an edge filter, which is configured to block electromagnetic radiation in the first, fluorescence-exciting wavelength range, in particular to absorb it, and to transmit light in a second wavelength range, wherein the second wavelength range comprises wavelengths corresponding to expected fluorescence and wherein the second wavelength range does not overlap with the first wavelength range. The test device is designed to detect the insertion of an object, to check images of the object represented by image signals from the area sensor, and to reject an object if one or more test criteria are not met, or to accept it if the test criterion(s) are not met. The testing device is further designed to identify a security marking on an object and to test a found security marking with regard to its fluorescence properties.

Inventors

  • Gerolf Burau
  • Robert Jansen

Assignees

  • DPG DEUTSCHE PFANDSYSTEM GMBH

Dates

Publication Date
20260513
Application Date
20241206
Priority Date
20241111

Claims (15)

  1. Testing device (60) for optically testing objects for authenticity, in particular for checking whether objects have a predefined, machine-readable optical code security marking (12) with known fluorescence properties, wherein the testing device (60) comprises the following components: - an illumination unit (38.1, 38.2) configured and arranged to illuminate an object to be tested with electromagnetic radiation – preferably light visible to the human eye – in a fluorescence-stimulating excitation wavelength range, - an area sensor (40) with a plurality of light-sensitive sensor elements, - an imaging optic (42) configured and arranged to project an image of an object onto the area sensor (40), wherein the area sensor (40) is configured to output an image signal representing an image projected onto the area sensor (40), - an optical filter (54) in the form of a high-pass or low-pass filter, in particular an edge filter, configured to block electromagnetic radiation in a blocking wavelength range encompassing the excitation wavelength range, in particular to absorb it, and to transmit light in a transmission wavelength range, wherein the transmission wavelength range includes wavelengths corresponding to expected fluorescence and wherein the transmission wavelength range does not overlap with the excitation wavelength range, whereby the test device (60) is configured to detect the insertion of an object, to check images of the object represented by image signals from the area sensor (40), and to reject an object if one or more test criteria are not met, or to accept it if the test criterion(s) are met, whereby a test criterion is the readability or non-readability of a machine-readable optical code depending on the presence or absence of fluorescence.
  2. Test device (60) according to Claim 1 , in which the optical filter (54) is part of the imaging optics and is a low-pass filter and the transmission wavelength range includes longer wavelengths than the blocking wavelength range.
  3. Test device (60) according to Claim 1 or 2 , with an electronic image evaluation unit connected to the area sensor (40) to receive at least indirectly raw or pre-processed image signals from the area sensor (40), wherein the image evaluation unit has a code reading component configured to identify and interpret machine-readable codes represented by image signals.
  4. Test device (60) according to Claim 3 , which is configured to generate an object to be tested as an authentically characterizing signal if the code reading component, when illuminated with electromagnetic radiation encompassing the excitation wavelength range and with an effective optical filter (54), identifies a machine-readable code in the image of a security-mark-like image component represented by the image signals.
  5. Test device (60) according to at least one of the preceding Claims 1 until 4 , which is configured to take two images of an object to be tested, with the object being illuminated for one image with electromagnetic radiation in the fluorescence-exciting excitation wavelength range and for another image with electromagnetic radiation in the transition wavelength range in which the absorption properties of an authentic security paint change significantly.
  6. Test device (60) according to Claim 5 , which is designed to check the image of the security marking (12) recorded with electromagnetic radiation in the transition wavelength range with regard to the contrast between light and dark character components.
  7. Test device (60) according to at least one of the Claims 1 until 6 , wherein the test device (60) is configured to first detect a safety marking (12) in the images of an object projected onto the area sensor (40), and to trigger a rejection of the object if no image of a safety marking (12) is found in the images of the object projected onto the area sensor (40).
  8. Test device (60) according to Claim 7 , wherein the test device (60) is configured to check, after detecting a safety mark (12) in the images of the object projected onto the area sensor (40), whether the signal-to-noise ratio or the dynamic range of the image signals representing the images of the object projected onto the area sensor (40) exceeds a predefined value and to reject the object to be tested if the signal-to-noise ratio or the dynamic range of the image signals representing the images of the object projected onto the area sensor (40) does not reach or exceeds the corresponding predefined value.
  9. Test device (60) according to Claim 8 , wherein the test device (60) is designed to to always reject an object if the signal-to-noise ratio or the dynamic range of the image signals representing the images of a currently inspected object projected onto the area sensor (40) reaches or exceeds the specified value.
  10. A method for optically verifying the authenticity of objects, comprising the following steps: - Detecting the input of an object to be verified, - Projecting an image of the object onto an area sensor (40) and generating and outputting at least one image signal representing an image of the object projected onto the area sensor (40), - Searching for an image of a security mark (12) in the image of the object projected onto the area sensor (40), - Determining the signal-to-noise ratio or a signal dynamic range value of the image signal representing the image of the object, and - Verifying the authenticity of the security mark (12) based on intensity values of the components of the security mark (12) represented by the image signal.
  11. Procedure according to Claim 10 , additionally encompassing the step - generating a signal indicating a failed test if, when searching for an image of a security mark (12), no image of a security mark (12) is bound and/or if the signal-to-noise ratio or the signal dynamic value of the image signal representing the image of the object does not meet a specified minimum criterion and/or if a security mark (12) found fails the authenticity test.
  12. Procedure according to Claim 10 or 11 , wherein the verification of authenticity comprises the following steps: - Illuminating (S1) an object to be tested with electromagnetic radiation in an excitation wavelength range suitable for exciting a fluorescence of an authentic security color, - Capturing an image of an object to be tested with an image acquisition unit in which an electromagnetic radiation blocking filter in the excitation wavelength range prevents the capture of electromagnetic radiation in the excitation wavelength range, and - Rejecting an object to be tested if an optical code of the security marking is not recognizable and/or not decodable in an image captured under electromagnetic radiation in the excitation wavelength range.
  13. Procedure according to one of the Claims 10 until 12 , wherein the verification of authenticity comprises the following steps: S1 Illuminating a detected security mark with electromagnetic radiation in an excitation wavelength range that excites fluorescence in authentic security paint, S2 Checking whether the security mark contains an interpretable machine-readable optical code when illuminated with electromagnetic radiation in an excitation wavelength range that excites fluorescence in authentic security paint, and S6 if no interpretable machine-readable optical code is found, generating a signal indicating that the security mark has failed the verification for authenticity (S6).
  14. Procedure according to Claim 13 , wherein the verification of authenticity comprises the following steps: S3 Illuminating the detected security marking with electromagnetic radiation in the transition wavelength range, S4 Determining a ratio of incident illumination intensity and the intensity of the light reflected by character components printed with security ink on authentic security markings, and checking whether the ratio of incident illumination intensity and the intensity of the light reflected by character components printed with security ink on authentic security markings meets a predetermined test criterion.
  15. Procedure according to Claim 13 and 14 , comprising step S5 generating a signal indicating that the security marking has passed the authenticity test (S5), if the test according to step S2 has shown that the security marking contains a machine-readable optical code interpretable when illuminated with electromagnetic radiation in a fluorescent excitation wavelength range for authentic security ink, and furthermore, the test according to step S4 has shown that the ratio of incident illumination intensity and the intensity of the light reflected by character components printed with security ink in authentic security markings meets the specified test criterion.

Description

The invention relates to a method and a device for testing objects with a security marking applied to them, as well as a system with several testing devices. Such methods and devices are used, for example, in a deposit system to allow for the refund of a deposit upon return of a deposit-bearing item—such as packaging—even if the item is not returned to the place of original purchase and where the deposit was originally paid. Since the deposit value, for example in the case of beverage packaging, can be several times the value of the packaging itself, it is known to incorporate security markings that are not easily forged and are intended to make the authenticity of, for example, a deposit mark verifiable. In general, security markings are used in a variety of ways to make counterfeiting more difficult and to offer the best possible assurance of the authenticity of a document, product, banknote, or the like. Security markings are used on deposit-bearing products because the deposit value is typically higher than the value of the packaging itself. It is particularly known to apply a security marking – e.g., by printing it – to an outer packaging covering, label, or band, which may be made of, for example, plastic, metal, or cardboard. This security marking may be composed of various parts made of different materials, e.g., printed with different colors, so that the resulting security marking has several adjacent fields with different reflection and/or emission properties. The reflection and/or emission properties of the fields may be wavelength-dependent, so that the optical appearance of these fields – in particular their relative brightness (intensity of the reflected light) in relation to each other – may depend on the wavelength range in which the security marking is illuminated. Known security markings, for example, feature a contrast field with a comparatively high reflectivity across a broad illumination wavelength range, encompassing, for instance, visible and infrared light. Such a contrast field can be formed by a material or paint containing titanium dioxide, which appears white to the human eye in daylight. Security markings are also known that feature a second field, a dark field, which exhibits low reflectivity across the broad wavelength range compared to the contrast field and is formed, for example, by a material or paint containing carbon black, which appears black. A third field of a known security marking is a security field that exhibits different reflective properties in at least one a priori known illumination wavelength range than in another a priori known illumination wavelength range. For example, the security field can have low reflectivity in a first illumination wavelength range, such as that visible to the human eye. In a second, different wavelength range of light, visible or invisible to the human eye, the safety field exhibits higher reflectivity – or vice versa. The safety field is formed by a safety paint, preferably applied to a broadband highly reflective substrate, which exhibits higher absorption over a larger, visible first wavelength range than over a second, longer wavelength range. In this second, longer wavelength range, the safety paint may, for example, have high transparency, so that the reflective properties of the safety field are determined by the substrate beneath the safety paint, or the safety paint itself may have a comparatively high reflectivity in this second, longer wavelength range. Between the first and second wavelength ranges, the reflection, transmission, or absorption properties change by more than 50% in a transition wavelength range, starting from the lower of the two values. The transition wavelength range is significantly narrower than both the first and second wavelength ranges taken individually, and is, for example, only one fifth or one tenth or less than the first or second wavelength ranges taken individually. In many cases, in addition to a security marking, an identification mark is also provided, which identifies the product type, manufacturer, or banknote, etc., e.g., indicating the manufacturer, product, or value of the banknote. The identification mark can be, for example, a GTIN represented in the form of a barcode or a QR code. GTIN stands for Global Trade Item Number, i.e., a globally recognized item number. Besides the character elements typically printed in black or in a dark color across a broad wavelength range, the background – that is, the area surrounding the dark-colored elements – is also important. The character components are light, and especially white, to ensure good contrast. Typically, the light, especially white, background of the character components of the identification mark is formed by the unprinted substrate on which the dark character components of the identification mark are also printed. This is regularly the same substrate that also forms the light contrast area of the security marking. The contrast ar