DE102018109142A1 - Method for verifying a fluorescent-based security feature - Google Patents

Abstract

The invention relates to a method for the verification of a fluorescent-based security feature, which contains a stimulable to the emission phosphor, by means of a smartphone. In a first step, the phosphor of the security feature is stimulated to emit by means of a lighting unit of the smartphone. The emission is detected after completion of the excitation during a predetermined cooldown, by taking a series of pictures or a video recording with an image capture unit of the smartphone. Finally, the image series or video recording is evaluated by means of a data processing unit of the smartphone, the emission detected during the cooldown being compared with stored reference data in order to verify the authenticity of the security feature.

Description

The present invention relates to a method for verifying a security feature.

From the state of the art it has long been known to provide security documents with security features in the form of luminescent substances in order to make them forgery-proof or verifiable. Such security features must be verified by appropriate procedures.

From the WO 2012/083469 A1 An apparatus for authenticating documents marked with photochromic systems is known. The photochromic security feature shows a change in color and / or a change in shape under the effect of a flashlight excitation. It is further described that the security feature is based on a retinal protein.

The WO 2013/034471 A1 describes a device for recognizing a document having a security feature with wavelength conversion properties. For this purpose, a light generating device is provided, which irradiates the security feature with excitation light, and an image pickup device which receives the light emitted by the security feature.

The WO 2013/034603 A1 describes a method for verifying a security document with a security feature in the form of a fluorescent printing element. The method provides that the printing element is excited by means of a light source and thereby emits an electromagnetic radiation, which is detected in a further step by means of a sensor. By comparing with given data, the collected data is evaluated. The verification result will be issued in a further step depending on the result of the comparison. In particular, the method should be performed with a smartphone, the flash module of the smartphone as the excitation source and the photosensor of the camera of the smartphone as a detection unit are used.

In verifying the fluorescent-based security features described in the aforementioned prior art, two hitherto unsolved problems have emerged. Previously known phosphors are regularly used as so-called conversion phosphors for the production of white LEDs, so that these phosphors are also regularly included in the flash LED of the image capture units (cameras) of smartphones and similar mobile devices. If the use of such devices for providing the excitation radiation is desired for checking security features, then the excitation source shows the same emissions that are expected from the security feature to be investigated, so that reliable verification is precluded. A second problem results from the fact that the phosphors mentioned in the prior art show very short decay times in the nanoseconds to μs range. Since the camera of a mobile device typically have a relatively low recording speed (modern premium smartphones up to 240 fps), the emissions originating from the security feature have decayed regularly before being picked up with a flash of a smartphone before taking the picture with the camera of a smartphone after completion of the excitation can.

After the state of knowledge given prior to the invention, the experts assumed that fluorescent-based security features are hardly suitable for a verification that is easy to perform under everyday conditions and at the same time satisfies comparatively high security requirements, since they are not verifiable with inexpensive and widespread devices. Either the known security features require very special test equipment, which can only be kept by larger units, such as banks or passport control points. Or the security features that can be tested with generally available devices, in particular smartphones, are easy to fake.

An object of the present invention is therefore to provide an improved method for the verification of a fluorescent-based security feature. In particular, the security feature should be detectable by means of an image capture unit of a smartphone and also verifiable with the data processing unit of the smartphone. In particular, when verifying not only the presence of an emission but specific properties of the emission to be tested.

According to the invention, the object is achieved by a method for the verification of a fluorescent-based security feature according to the appended claim 1.

A general solution to the aforementioned problem, which the invention implements, is first of all that a security feature is equipped with a specific phosphor which avoids the problems described above. This phosphor must be configured so that it is on the one hand with a light source of a smartphone or a similar mobile computing device, ie in particular a flash LED of a smartphone, excitable. At the same time, the phosphor must be one Luminescence (Lumineszenzausbeute, cooldown) have, which makes it possible to detect the decaying luminescence even after the end of the flash excitation still safe. The cooldown and emission during decay must be distinguishable from other phosphors and, in addition, the evanescent luminescent signals should not be visually perceptible to humans. It has been found that these conditions are only met by a few, specifically configured phosphors that can be used in safety features. A suitable phosphor is described in the further patent application entitled "Smartphone Verifiable Fluorescent-based Security Feature and Apparatus for Verification" filed by the same day applicant. The content of this further patent application, in particular with regard to the composition and the preparation of a phosphor which can be used here, is explicitly and completely included in the disclosure of the present invention.

The method according to the invention is used to verify a fluorescent-based emission-triggerable security feature which is arranged on a security document. The method can be executed using a smartphone or a similar mobile terminal, which is configured and controlled by software, preferably in the manner of an app.

A security feature which can be evaluated by the method according to the invention is applied to or introduced into a security document and comprises the above-mentioned security feature. Phosphor. The phosphor can be excited by an electromagnetic radiation of predetermined wavelength for luminescence, whereupon it emits radiation. The emission of the phosphor has a cooldown in the ms range. Preferably, the cooldown in the range between 1 to 100 ms, more preferably in the range between 5 to 50 ms, more preferably selected between 10 and 30 ms. Furthermore, the emission of the phosphor can be detected by means of an image acquisition unit of a smartphone.

In a first method step, the security document is positioned so that the security feature is detected by an image capture unit of the smartphone. In the simplest case, this is done by manual positioning of the security document in front of the image acquisition unit. Preferably, a semi-transparent mask or a position frame in the display of the mobile terminal is shown as a user support, which serves as a position aid. The security document may have a human visually recognizable tag positioned within the position frame. The security feature is then located near this tag so that it is within the detection range of the image capture unit.

Alternatively, an object recognition can be carried out by means of the image acquisition unit and a data processing unit of the smartphone (mobile terminal). The object recognition serves indirectly to determine the position of the security feature on the document and / or it supports the positioning of the smartphone over the security document. The object recognition can also be used for an automatic triggering of the detection.

In an optional method step, a receiving frame or a receiving window is defined, wherein its position is defined on the basis of the previously determined position of the security feature and wherein the receiving frame is selected such that the security feature is arranged in the region of the receiving frame.

In a subsequent method step, the security feature is excited by means of a lighting unit of the smartphone (mobile terminal) for luminescence, so that the security feature emits an electromagnetic radiation. By means of an app (software application), the illumination unit and the image acquisition unit are controlled by the data processing unit of the smartphone, whereby a combination of single flash and video recording or single flash and continuous shooting takes place and the lighting unit is switched off after the stimulation of the phosphor of the security feature, so that after the end of the flash the decaying Emission can be recorded by the image acquisition unit.

An optional method step provides that a reference area is defined, which is located immediately adjacent to the security feature. The evaluation of captured images of the security feature and the reference range as well as the differences recorded there (image difference, histograms, hue values) can be helpful for a verification of the document in strongly flickering extraneous light.

In a further method step, an image series or a video of the security feature as well as optionally of the reference region is recorded by means of an image capture unit of the smartphone in order to detect the emission. Preferably, the recording takes place in the specified recording area. The detection of the emission takes place after completion of the excitation, ie after switching off the flash. The recording time of the image series recorded by the image acquisition unit or the video is preferably selected such that the last Image of the image series or video no emission of the security feature is more detectable, provided that the predetermined decay times of the phosphor of the security feature are met. This last image is taken as a reference image (B _ref ). Likewise, optionally before starting the phosphor, a start image can be recorded, which can be included as a further reference in the verification.

In a further method step, the acquired or recorded image series or videos are processed by means of the data processing unit and compared with default or reference data. In the simplest case, reference data are stored in the smartphone, which are compared with the determined emission parameters.

The image differences between the acquired images and the reference image acquired after the emission has subsided are preferably generated (Δ _1R = B ₁ -B _ref ... Δ _nR = B _n -B _ref ), from which the emission values are subsequently determined by means of an RGB histogram different color channels are calculated and then the decay time of the phosphor is analyzed from the determined data. Preferably, n = 10 images are used for the calculation of the image difference. Preferably, the number of images is between 5 and 15 images.

wobei Δt das Zeitintervall zwischen den Bildern ist und E(t) der Emissionswert zu einem bestimmten Zeitpunkt des Abklingens ist.Assuming an exponential decay behavior, the decay time (τ) can be determined by the following equation: $$\mathrm{\tau \; =\; \Delta }t/ln\frac{e\left(t_1\right)}{e\left(t_2\right)}\text{With}e\left(t_1\right)=e_0{e}^{-\frac{t_1}{\tau }}\text{and}e\left(t_2\right)=e_0{e}^{-\frac{t_2}{\tau }};$$

where Δt is the time interval between the images and E (t) is the emission value at a certain time of fading.

These values can be determined from a histogram of the images or the image difference.

The spectral distribution of the emission of the phosphor can be determined from the color coordinates for different images, where: $$K_R=\frac{R}{R+G+B}\text{and}{K}_G=\frac{G}{R+G+B},$$

Furthermore, a comparison of an additional start image recorded before activation of the excitation radiation with the images of the image series recorded during the decay time and with the last image (reference image) is possible.

By means of the comparison, the presence of the security feature in the region of the receiving frame can be verified and subsequently the authenticity of the security document can be checked. In particular, verification of the security feature on the security document can verify the authenticity and integrity of the security document.

The reference image, which is the last image of the image series, is generated in a predetermined time frame, in particular in the ms range, whereby emissions with decay times greater than the ms range are also filtered out. For this purpose, the reference image can be compared with the start image recorded before activation of the excitation radiation.

• - Referenzprüfung, Vergleich des letzten Bilds (Referenzbild) aus der Serienaufnahme mit einem vor der Anregung aufgenommenen Startbild;
• - Detektion des Sicherheitsmerkmals und
• - Bestimmung der Emissionseigenschaften (τ, λ) des Sicherheitsmerkmals bzw. dessen Leuchtstoff.

The authenticity of the security feature is checked in one embodiment of the method on the basis of the following features:

• - reference test, comparison of the last image (reference image) from the series recording with a recorded before the excitation start image;
• - Detection of the security feature and
• - Determination of the emission properties (τ, λ) of the security feature or its phosphor.

The take-up speed in generating the image series is selected so that fluorescent phosphors or features with short cooldowns, i. in the μs range, are excluded as unverifiable, since such short emissions are not detected with sufficient intensity. By means of a reference test, in which a comparison of the last image in the image with the image taken before excitation takes place, phosphors with long cooldowns are excluded as unverifiable. If one of the two preceding features points to a fluorescent or phosphorescent phosphor, the result of the authenticity of the security feature is output as "false".

In addition to the presence of the searched phosphor in the security feature and the outer shape of the security feature can be checked. If the detected phosphor and the security feature do not correspond to the deposited data of the predetermined phosphor or security feature, the authenticity is determined to be "false". For the characteristic of the emission properties, the spectral distribution of the radiation emitted by the phosphor and the decay time of the phosphor of the security feature are checked. If the spectral position as well as the cooldown of the phosphor match the stored values, and if the other features are still positive ("true"), the verification indicates that the security feature is "genuine".

The optional object recognition preferably comprises various image processing steps, such as noise reduction, contrast matching or color channel enhancement filter applications, a shape analysis to detect the security feature. The noise reduction can be done for example by means of morphological filters such as erosion or dilatation. For the shape analysis a template matching can be used. The fast Fourier transform (FFT) of the images can also be used.

In a preferred method step, which makes sense above all in strong ambient light, the distance between the security document with the security feature and the image capture unit of the smartphone is selected to be less than or equal to the distance of the focus range of the image capture unit. No optical focus or focus adjustment is needed. The distance between the smartphone camera and the security feature when capturing the images can thus be chosen to be very small, since no sharp images are needed for the present method, because only the emission and if necessary the shape of the security feature are detected. The small distance between the security feature and the camera has the advantage that more energy is available for the excitation of the phosphor of the security feature, and that the emission of the phosphor is detected over a wide solid angle. The minimization of the distance between camera and security feature is particularly significant due to the quadratic dependence of the intensity of the flash light on the distance to the excitation source or the emission from the distance to the detection unit. Thus, a comparatively low emission can be detected, which would no longer be detectable when recording in the focus range. This reduces the false rejection rate (i.e., a true security document is rated false). For example, standard smartphones have a focus range of 60 mm. Preferably, therefore, a distance between 10 mm and 80 mm between the image capture unit and the security document with security feature for taking the images is used for the method. Particularly preferably, the distance during image acquisition between the image capture unit and the security document with the security feature is less than 50 mm. Another advantage of using blurred images is to reduce the resolution of the images and thus speed up the processing of the images.

In another embodiment of the method for verifying the security feature, a reference area is selected next to the area of the security feature, ie next to the area of the phosphor. Preferably, the two areas have the same visible body color. This compensates for the fluctuation in exposure during exposure to artificial light (50 Hz flickering). Preferably, the positions of the phosphor and the reference region are predefined on the security document (eg, relative to a prominent character on the document). For verification, an equal number of pixels in both areas is selected for all acquired images, and for each image, a difference in image is created for those areas.

For certain phosphors, especially silicate garnets, an additional verification factor can be used. These phosphors show a broad emission spectrum with local maxima in the green and red spectral range, which also have different cooldowns. It follows that during decay measurements over the entire visible spectral range a characteristic color shift is detected, which can also be used as authenticity criterion.

A further advantage of the method is that the known and existing in a variety of users smartphone can be used as a mobile terminal for verification of the security feature. It is a quick, internal evaluation and authentication of measured with the smartphone phosphor emissions carried out. It is also advantageous that the distance between the security feature and the image capture unit can be kept low, since at the same time covering the security feature against ambient light, such as daylight or room light occurs.

The method with its method steps is preferably provided as an application or app for the smartphone.

The frame rate of the image sensor used (in particular smartphone camera) determines a lower limit, which must be achieved by the decay behavior of the phosphor. An upper limit is given by the physiological properties of the human eye, in particular by the visual perception, ie the reception and processing of optical stimuli by the eye and the brain. In order to be able to assign the luminescent material used in the security feature to a high security level, the emission of the security feature should not be detectable by human visual perception. In particular, the cooldown of the phosphor should be less than 1 s, since from 1 s afterglow of the Phosphor takes place, which is perceptible by humans. The phosphor is chosen so that its decay time is in the single-digit or two-digit ms range. Preferably, the decay time of the phosphor (always considered from switching off the excitation source) of the security feature is in the range of 1 ms to 50 ms. The phosphor of the security feature particularly preferably has a decay time of 10 ms to 30 ms.

So that the security feature can be detected solely by means of a mobile terminal (in particular a smartphone), the phosphor is configured so that it can be excited in the visible spectral range, in particular in the blue spectral range, so that the flash light source of the smartphone can supply this excitation radiation. Furthermore, the phosphor is configured to emit in the visible spectral region, which emission due to the short decay time is not detectable by the user by visual perception.

The white light of the illumination unit of a smartphone is generated by an LED consisting of an LED semiconductor chip with an emission at about 450 nm and LED conversion phosphors placed above the LED semiconductor chip, the conversion phosphors proportionately converting the emission of the blue LEDs into longer wavelengths convert visible luminescence radiation (broadband emission in the green, yellow and red spectral range) with an emission maximum of, for example, about 560 nm. The white light of the LED, which is available as a lighting unit for commercially available smartphones, results from the additive color mixing of the individual luminescence components described, with the blue spectral component having the higher intensity. This means that the phosphor which can be used for providing the security feature according to the invention preferably has to be configured in such a way that it has a high spectral excitability efficiency, in particular in the range between 420 nm and 470 nm. Particularly preferably, the phosphor has an effective excitation wavelength of 450 nm.

For detecting the luminescence signals of the phosphor, the smartphone camera is available as image capture unit. Preferably, the image capture unit is a CMOS sensor equipped with an IR filter, whereby a spectral sensitivity to about 750 nm exists. By means of the image capture unit, individual images, image series or videos can be recorded.

The method according to the invention can in principle be used in various testing devices. Such testers can be used as a retrofit module for stationary testing (eg in ATMs) or preferably designed as a mobile terminal. The mobile terminal is preferably a smartphone, but may also be a tablet or another similar multifunctional data processing device that includes a camera with an image capture unit and / or illumination unit and a data processing unit. The data processing unit is preferably a processor, in particular a microprocessor. The check can also be performed with stationary terminals or other data processing systems with image acquisition units (eg desktop monitors or service terminals).

Preferably, the phosphor is arranged in the security feature so that it forms a pattern. The phosphor, in particular the luminescent pigments of the phosphor are preferably applied as a defined pattern on a support. The pattern may be arranged as a shape, for example a triangle or a star. Alternatively, the security feature pattern formed by the phosphor may include data and be arranged as a code, such as a QR code.

The pigments of the phosphor are printed as a security feature, for example on a security document or on a layer of a security document. The printing or application of the phosphor on the security document can with known printing methods such. As gravure, flexographic, offset, screen or digital printing process done. Furthermore, the phosphor can be applied to the security document by coating methods or laminating methods.

An authenticity check and / or integrity check can be carried out. The verification of the security feature is only possible by the choice of the phosphor with cooldowns in the ms range. It has proved to be advantageous that its emissions are still measurable safely even after completion of the excitation process by the specially selected phosphor. Both the phosphor over the cooldown and the emission spectrum, as well as the pattern formed by the phosphor can be verified as a further safety factor. Thus, a high level of security against counterfeiting can be achieved by combining several factors. For secure authentication of a security document with the security feature, it can be arranged, for example, in a region of another security feature, such as a figure.

The security feature can be applied to different security documents, for example, a banknote, an ID card, a Passport, driver's license, ticket, stamp or similar.

• 1 eine Ausführungsform eines erfindungsgemäßen Sicherheitsmerkmals auf einem Geldschein;
• 2 eine schematische Darstellung von Komponenten einer erfindungsgemäßen Anordnung zur Verifikation des Sicherheitsmerkmals;
• 3 ein Diagramm mit dem An- und Abklingverhalten eines Leuchtstoffes des Sicherheitsmerkmals bei Blitzlichtanregung;
• 4 ein Ablaufplan zur Durchführung der Verifikation des Sicherheitsmerkmals mit der erfindungsgemäßen Anordnung.

Further details, advantages and developments of the invention will become apparent from the following description of preferred embodiments of the invention, with reference to the drawing. Show it:

• 1 an embodiment of a security feature according to the invention on a bill;
• 2 a schematic representation of components of an inventive arrangement for verification of the security feature;
• 3 a diagram with the arrival and Abklingverhalten a phosphor of the security feature in flash excitation;
• 4 a flowchart for performing the verification of the security feature with the inventive arrangement.

1 shows a security feature according to the invention 01 which is on a value document, namely a symbolically represented security document 02 is applied in the form of a bill. The security feature is for the verification of the security document 02 usable. The security feature 01 here has a star shape. It is below a visible feature 03 , here the face value of the bill, positioned. The security feature 01 consists of a by means of an electromagnetic radiation having a predetermined wavelength excitable luminescence phosphor, as mentioned above and is explained in detail in the incorporated further patent application of the applicant.

The security feature 01 can be verified by a method, the authenticity of the security feature 01 is checked.

2 shows a schematic arrangement for verification of the security feature 01 , the security feature 01 by means of a lighting unit 04 an image capture unit 06 a mobile terminal, in particular a smartphone 07 , which is excited to luminesce by the lighting unit 04 Exciting light, in particular a flashlight 08 generated. The flash 08 the image acquisition unit 06 is generated by means of a white light emitting LED. The flash 08 has an intensity I _A , Upon excitation, the phosphor emits the security feature 01 an electromagnetic radiation which occurs after the end of the excitation for a decay time in the ms range. The emission I _E of the phosphor is with a camera or a detector 09 the image acquisition unit 06 detectable. Furthermore, the detector detects 09 one on the security feature 01 and the bill 02 incident and reflected at this ambient radiation I ₀ of daylight or room light. The ambient radiation I ₀ is kept low in the inventive method, since a distance d between the security feature 01 and the smartphone 07 can be kept low. Due to the small distance d , which is preferably below the focus range (focus) of the image pickup unit 06 lies, the smartphone shields 07 the ambient radiation I ₀ mostly from.

In 3 is a diagram with the arrival and decay of the phosphor, the safety feature 01 used is shown. In the diagram is an emission curve 11 of the luminescent excited security feature 01 along a timeline t shown. Furthermore, a flashlight excitation curve 12 plotted along the time axis. Will the flash using the smartphone 07 ( 2 ), the flashlamp excitation curve increases 12 Steep, holding their level for a short time and drops to zero, after the flash is extinguished. The electromagnetic radiation of the flash becomes the phosphor of the security feature 01 excited to luminescence, whereby the emission curve 11 almost at the same time as the flash emission curve 12 rises, regularly with reduced steepness. The emission curve 11 drops much more slowly than the flashlight excitation curve after the flashlight goes out. The decay behavior of the phosphor is according to the invention in the ms range.

Below the time axis are in 3 single by the detector 09 of the smartphone 07 ( 2 ) captured images 13 of the security feature 01 shown. The pictures 13 show the decaying emission of the security feature 01 as a weakening pattern over time. You can for the verification of the security document 02 be used in a further process step. After essentially complete decay of the emission, a reference image can be used as the last image of the recorded image sequence 14b be recorded.

Depending on the evaluation method, an additional reference image 14a also be recorded before activation of the excitation radiation (triggering of the flash). An additional control of the security feature is possible, for example, by the reference images 14a and 14b compared with each other.

4 shows in simplified form the basic procedure of the verification of the security feature 01 using the in 3 illustrated arrangement. In a positioning step 41 The security document to be verified is positioned so that it can be reliably detected by the image capture unit of the smartphone. In one optional reference check step 42 Already before the triggering of the flashlight excitation of the smartphone the start picture 14a of the security feature. In a detection step 43 A single flash is fired by the image pickup unit of the illumination unit of the smartphone and a burst is taken to record the luminescence signals of the phosphor used to create the security feature present after the end of the flashlamp excitation and decaying in the ms range. Finally, in an emissions analysis step 44 the recorded image series and the reference images by means of the data processing unit compared. In addition to the calculation of the image differences and their analysis, other methods of image processing such as the contrast adjustment and the histogram analysis of the different color channels are used to verify in this way both the spectral emission and the exclusive Abklingcharakteristik the phosphor used in the invention. In an optional extraction step, object recognition can be performed. By comparing the calculated parameters with the authenticity parameters of the security feature preferably stored in the data memory of the smartphone, the authenticity of the checked security document can be determined in a release step 45 beeing confirmed. In particular, the authenticity and integrity of the security document can be confirmed by the verification of the security feature on the security document.

LIST OF REFERENCE NUMBERS

01

safety feature

02

Security document / banknote / banknote

03

nominal value

04

lighting unit

05

-

06

Imaging unit

07

Smartphone

08

flashlight

09

Detector / camera

10

-

11

emission curve

12

Flash light excitation curve

13

Image capture of the security feature 01

14a

start screen

14b

reference image

41 - 45

steps

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 2012/083469 A1 [0003]
• WO 2013/034471 A1 [0004]
• WO 2013/034603 A1 [0005]

Claims (9)

A method of verifying a phosphor-based security feature comprising a phosphor excitable for emission by means of a smartphone comprising the steps of: - exciting the phosphor of the security feature for emission by means of a lighting unit of the smartphone; Detecting the emission after completion of the excitation during a predetermined cooldown by taking a series of pictures or a video recording with an image acquisition unit of the smartphone; - Evaluation of the image series or video recording using a data processing unit of the smartphone, wherein the detected during the cooldown emission is compared with stored reference data to verify the authenticity of the security feature. Method according to Claim 1 , characterized in that for the evaluation of the image series, the emission properties decay time (τ), wavelength (λ) and / or color shift are determined and compared with the reference data. Method according to Claim 1 or 2 characterized in that for detecting the emission, the image differences between the images taken during the decay time and the reference image acquired after emission decay are generated (Δ _1R = B ₁ -B _ref ... A _nR = B _n -B _ref ), and that the emission values are subsequently calculated by means of an RGB histogram as the hue value of the different color channels and from this the decay time of the phosphor is determined. Method according to one of Claims 1 to 3 characterized in that before the excitation of the phosphor the following steps are carried out: performing an object recognition by means of the image acquisition unit and the data processing unit of the smartphone for determining the position of the security feature on the security document or positioning the smartphone over the security document according to a predetermined positional frame, which in a display of the smartphone is displayed, and on the basis of a position feature of the security document on which the positioning frame is arranged; - Determining a receiving frame based on the specific position of the security feature, the security feature is located in the region of the receiving frame; - Specifying a reference region, which is arranged indirectly adjacent to the receiving frame; and that after completion of the excitation, the capture of the series of images in the frame and in the reference area takes place. Method according to Claim 4 , characterized in that the image series recorded in the recording frame is compared with the image series acquired in the reference region by means of the data processing unit. Method according to one of Claims 1 to 5 , characterized in that the recording time is selected so that the last image of the image series is taken after the end of the decay time, and that the security feature is verified as genuine only if in this last image no emission of the phosphor is detectable. Method according to Claim 6 , characterized in that a comparison of one or more images from the image series of the position frame with the last image of the image series by means of the data processing unit of the smartphone in the following sub-steps: - Emission detection, each one image difference of the captured images is determined with the reference image, an RGB Histogram is created, the hue value of the different color channels is determined and the decay time of the phosphor is determined; and object recognition, wherein a shape analysis of the security feature occurs. Method according to one of Claims 1 to 7 , characterized in that during the excitation of the phosphor and the detection of the emission of the distance between the security feature and the image capture unit of the smartphone is selected to be smaller than the focus range of the image acquisition unit. Method according to one of Claims 1 to 8th , characterized in that an application (App) is installed on the mobile terminal, which controls the illumination unit, the image acquisition unit and the data processing unit for carrying out the method.

Images