CN111989721A

CN111989721A - Method for verifying security features based on luminescent materials

Info

Publication number: CN111989721A
Application number: CN201980026799.2A
Authority: CN
Inventors: 拉扎尔·库利科夫斯基; 德特勒夫·斯塔里克; 曼弗雷德·佩施克; 约尔格·菲舍尔; 弗兰克·弗里策; 伊利亚·科马罗夫
Original assignee: Federal Printing Co ltd
Current assignee: Federal Printing Co ltd
Priority date: 2018-04-17
Filing date: 2019-04-15
Publication date: 2020-11-24
Anticipated expiration: 2039-04-15
Also published as: WO2019201839A1; EP3782136A1; EP3782136B1; DE102018109142A1; CN111989721B

Abstract

The invention relates to a method for verifying a security feature based on luminescent material by means of a smartphone, the security feature comprising luminescent material that can be activated to emit. In a first step, the luminescent material of the security feature is excited by the lighting unit of the smartphone to emit it. The radiation is detected by capturing a sequence of images or video with an image detection unit of the smartphone during a predetermined decay time after the excitation is finished. Finally, the image sequence or video is evaluated by means of a data processing unit of the smartphone, wherein the radiation detected during the decay time is compared with stored reference data to verify the authenticity of the security feature.

Description

Method for verifying security features based on luminescent materials

Technical Field

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

Background

It has long been known from the prior art to provide security documents with security features in the form of luminescent substances, in order to render them forgery-proof or verifiable. Such security features must be verified by a suitable method.

An instrument for authenticating documents marked with a photochromic system is known from WO 2012/083469 a 1. Photochromic security features exhibit a color change and/or a shape change upon flash excitation. It is also described that the safety feature is constructed based on retinal proteins.

WO 2013/034471 a1 describes an apparatus for identifying documents having a security feature with wavelength conversion properties. For this purpose, a light-emitting device is provided which irradiates the security feature with excitation light, and an image recording device is provided which receives the light emitted by the security feature.

WO 2013/034603 a1 describes a method for authenticating a security document having 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 emits electromagnetic radiation as a result, which is detected by a sensor in a further step. The detected data is evaluated by comparison with given data. In a further step, a verification result is output depending on the comparison result. In particular, the method will be implemented in a smartphone, wherein a flash module of the smartphone is used as excitation source and a light sensor of a camera of the smartphone is used as detection unit.

A multifunctional mobile device is known from US 2010/0144387 a 1. The device includes a camera module, a processor unit, and a display.

Two problems which have not been solved so far arise in the verification of the security features based on luminescent materials described in the above prior art. Previously known luminescent materials are often used as so-called conversion luminescent materials for generating white LEDs, so that these luminescent materials are also often contained within flash LEDs of camera units (cameras) of smartphones and similar mobile devices. If it is desired to use such a device to provide excitation radiation for the purpose of interrogating a security feature, the excitation source exhibits the same emission as the security feature to be inspected, so that reliable verification cannot be performed. A second problem is caused by the fact that luminescent materials as described in the prior art have a very short decay time in the ns to mus range. Since the camera of a mobile device typically has a relatively low shooting speed (up to 240fps for modern advanced smartphones), the radiation originating from the security features is usually attenuated already when the smartphone is fired with a flash of light, before image shooting can be performed using the smartphone's camera after the firing has ended.

According to the state of knowledge prior to the present invention, experts consider that luminescent material-based security features are hardly suitable for authentication that is simple to perform in daylight, while satisfying relatively high security requirements, because they cannot be authenticated with cheap and widely used equipment. Known security features require very special pinging devices that are available only in larger units, such as bank or transit checkpoint prescriptions. Or security features that can be verified with generally available devices, such as smartphones in particular, are easily forged.

Disclosure of Invention

It is therefore an object of the present invention to provide an improved method for verifying security features based on luminescent materials. In particular, the security feature should be detectable by the image capturing unit of the smartphone and also verifiable by the data processing unit of the smartphone. In particular, in the case of verification, not only the presence of the radiation but also the specific characteristics of the radiation should be checked.

According to the invention, this object is achieved by a method for verifying a luminescent material based security feature according to the appended claim 1.

The general solution proposed for the task adopted by the invention consists firstly in equipping the security features with specific luminescent substances which avoid the problems described above. The luminescent material must be configured to this end such that it can be excited on the one hand by the light source of the smartphone or such a mobile data processing device, and thus in particular by the flash LED of the smartphone. At the same time, the luminescent material must have a luminescence representation (luminescence capture rate, decay time) which enables a reliably detectable decaying luminescence signal even after the end of the flash excitation. The decay time and the radiation occurring during the decay must be distinguishable from the other luminescent material and furthermore the decaying luminescent signal should not be perceptible by human vision. This means that this condition is only met by a few specifically configured luminescent materials that can be used in the security feature. Such luminescent materials must in particular have a decay time in the ms range. Suitable luminescent substances are given in german patent application DE 102018109141.9 entitled "smart phone verifiable security features and facilities for verification" filed by the applicant at the same priority date (2017, 4/17). The contents of this further patent application, particularly with respect to the composition and manufacture of luminescent materials usable therein, are incorporated in full and in full into the disclosure of the present invention.

The method according to the invention is used for verifying a security feature based on luminescent material, which can be excited to emit radiation, which security feature is arranged on a security document. The method can be implemented by means of a smartphone or similar mobile terminal device, which is configured and controlled correspondingly by software, preferably in the form of an App.

The security feature that can be evaluated by the method according to the invention is applied to or incorporated into a security document and comprises the above-mentioned luminescent material. The luminescent material may be excited to luminesce by electromagnetic radiation of a predetermined wavelength, which subsequently emits the radiation. The decay time of the emission of the luminescent material is in the range of ms. The decay time is preferably selected in the range between 1ms and 100ms, particularly preferably in the range between 5ms and 50ms, and again preferably in the range between 10ms and 30 ms. Furthermore, the emission of the luminescent material may be detected by means of an image detection unit of the smartphone.

In a first method step, the security document is positioned such that the security feature is detected by an image capture unit of the smartphone. In the simplest case, this is done by manually positioning the security document in front of the image capturing unit. Preferably, a translucent mask or a positioning frame is shown in the display of the mobile terminal device as a user support. A marking positioned within the positioning frame, which marking can be visually perceived by a person, can be applied to the security document. The security feature is then placed in the vicinity of this marker so that the marker is located within the detection area of the image detection unit.

Alternatively, the object recognition may be performed by means of an image detection unit and a data processing unit of a smartphone (mobile terminal device). Object recognition is indirectly used to determine the location of security features on the document and/or to support the location of a smartphone on top of a security document. Object recognition may also be used for automatic triggering of detection.

In an optional method step, a camera frame or a camera window is provided, wherein the position thereof is defined according to a previously determined position of the security feature, and wherein the camera frame is selected such that the security feature is arranged in the region of the camera frame.

In a subsequent method step, the security feature is excited to emit light by means of an illumination unit of the smartphone (mobile terminal), so that the security feature emits electromagnetic radiation. By means of an App (software application), the illumination unit and the image capture unit are controlled by a data processing unit of the smartphone, wherein a combination of single flash and video capture or a combination of single flash and series capture is carried out, and wherein the illumination unit is switched off after the luminescent material of the security feature is excited, so that attenuated radiation can be captured by the image capture unit after the flash of light has ended.

An optional method step provides that a reference region is defined, which is directly adjacent to the security feature. The evaluation of the image and reference areas of the detected security features and of the differences (image differences, histograms, hue values) detected there can be helpful for document verification in the case of strong external light.

In a further method step, an image sequence or video of the security feature and optionally of the reference region is recorded by an image detection unit of the smartphone in order to detect the radiation. The image capture is preferably performed in a predetermined image capture area. After the excitation is finished, the emission is detected, i.e. after the flash is switched off. Preferably, the capturing time of the image sequence or of the video captured by the image detection unit is selected such that the emission of the security feature can no longer be detected in the last image of the image sequence or of the video as long as the predetermined decay time of the luminescent substance of the security feature ceases. This last image is taken as a reference image (B)_{Reference to}). Also, before exciting the luminescent material, a starting image may optionally be taken, which may be employed in the verification as a further reference.

In a further method step, the detected or captured image sequence or video is processed by a data processing unit and compared with predetermined data or reference data. In the simplest case, the reference data is stored in the smartphone and then compared to the known radiation parameters.

Preferably, an image difference (Δ) between the detected image and a reference image detected after the radiation attenuation is generated_1R＝B₁-B_{Reference to}…Δ_nR＝B_n-B_{Reference to}) The emission values are then calculated from the RGB histogram as hue values for the different color channels, and the decay time of the luminescent material is then analyzed from the learned data. Preferably, the image difference is calculated using n-10 images. The number of images is preferably between 5 and 15 images.

Assuming exponential decay behavior, the decay time (τ) can be determined by the following equation:

wherein

And is

Where Δ t is the time interval between images and e (t) is the radiation value at a determined instant of the attenuation.

These values may be known from histograms of images or image differences.

The spectral distribution of the emission of the luminescent material can be known from the color coordinates of the different images, wherein:

And is

Furthermore, a comparison of an additional starting image taken before the activation of the excitation radiation with the images of the image sequence taken during the decay time and with the last image (reference image) can be carried out.

By comparison, the presence of the security feature in the region of the camera box can be verified, and the authenticity of the security document can then be verified. In particular, by verifying security features on the security document, the authenticity and integrity of the security document may be verified.

The reference image, which is the last image in the image sequence, is generated within a predetermined time range, in particular within the ms range, so that radiation with a decay time greater than the ms range is also filtered out. For this purpose, the reference image may be compared with a starting image taken before activation of the excitation radiation.

In one embodiment of the method, the authenticity of the security feature is verified according to the following features:

reference check, comparing the last image in the series of photographs (reference image) with the starting image taken before the excitation;

-detecting a security feature, and

-determining an emission characteristic (τ, λ) of the security feature or of the luminescent material thereof.

The acquisition speed at the time of the generation of the image sequence is chosen such that fluorescent luminescent substances or features with short decay times, i.e. in the range of μ s, are inferred as being not verifiable, since such short emissions cannot be detected with sufficient intensity. By reference examination, in which the last image in the photograph is compared with the starting image taken before the excitation, luminescent substances with long decay times are inferred as not being verifiable. If one of the two features indicates a fluorescent or phosphorescent material, the result of the authenticity of the security feature is output as false.

In addition to checking for the presence of luminescent material sought within the security feature, the external shape of the security feature may also be checked. The authenticity is determined as "false" if the detected luminescent material and the security feature do not correspond to the stored data of the predetermined luminescent material or security feature. For the emission-characterized feature, the spectral distribution of the radiation emitted by the luminescent material and the decay time of the luminescent material of the security feature are examined. If the spectral position and decay time of the luminescent material coincide with the stored values, and if the other features are still confirmed to be positive ("true"), a verification is obtained that the security feature is "true".

The optional object recognition preferably comprises different image processing steps, such as filter applications for noise reduction, contrast matching or color channel enhancement, for detecting shape analysis of the security feature. The noise reduction may be performed, for example, by means of morphological filters, for example, by erosion or dilation. Template matching may be used for shape analysis. A Fast Fourier Transform (FFT) of the image may also be used.

In a preferred method step, which is meaningful in particular in strong ambient light, the distance between the security document with the security feature and the image detection unit of the smartphone is selected to be equal to or less than the distance of the focusing area of the image detection unit. No optical focusing or focus adjustment is required. Since no sharp image is required for the method, the distance between the smartphone camera and the security feature can be chosen to be small when detecting the image, since only the emission of the security feature and, if necessary, the shape of the security feature are detected. The advantage of a small distance between the security feature and the camera is that more energy is available to excite the luminescent material of the security feature and the emission of the luminescent material is detected over a wide spatial angle. Minimizing the distance between the camera and the security feature is particularly important due to the quadratic dependence of the intensity of the flash light on the distance to the excitation source or the quadratic dependence of the emission on the distance of the detection unit. Thus, it is also possible to detect radiation which is relatively low and is no longer detectable when recording in the focus region. This reduces the false rejection rate (i.e. the true security document is rated as false). For example, a typical smartphone has a focus area of 60 mm. For the method, therefore, a distance of between 10mm and 80mm between the image detection unit and the security document with security features is preferably used for capturing the image. The distance between the image recording unit and the security document with the security feature is particularly preferably less than 50mm during image recording. Another advantage of using blurred images is that the resolution of the image is reduced and thus the processing of the image is accelerated.

In a further embodiment of the method for authenticating a security feature, the reference area is selected next to the area of the security feature, i.e. next to the area of the luminescent material. Both areas preferably have the same visible surface color. Thus, it can be used to compensate exposure fluctuations during photographing under artificial light (50Hz flicker). Preferably, the positioning of the luminescent material and the reference area on the security document is predefined (e.g. with respect to a particular symbol on the document). For verification, an equal number of pixels is selected in both regions of all detected images, and an image difference is created for these parts for each image.

For certain luminescent materials, in particular silicate garnets, additional validation factors can be used. These luminescent substances exhibit broad emission spectra with local maxima in the green and red spectral range and, in addition, different decay times. It follows that the characteristic color shift is ascertained when the attenuation is measured over the entire visible spectral range, which can also be used as an authenticity criterion.

Another advantage of the method is that a large number of users can use known smart phones as mobile terminal devices to verify the security features. A rapid, internal evaluation and verification of the luminescent material emissions measured with the smartphone is performed. It is furthermore advantageous that the distance between the security feature and the image capturing unit can be kept small, since the security feature is simultaneously shielded from ambient light, for example sunlight or indoor light.

The method and its method steps are preferably provided as an application or App of a smartphone.

The image frequency of the image sensor used, in particular the smartphone camera, determines the lower limit that can be reached by the attenuation behavior of the luminescent material.

The upper limit is predetermined by the physiological properties of human vision, in particular by the visual perception, i.e. the reception and processing of optical stimuli by the eyes and brain. In order to be able to assign the luminescent materials 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 decay time of the luminescent material should be less than 1s, since the afterglow of the luminescent material is perceivable by humans from 1 s. The luminescent material is selected such that its decay time is in the range of several ms or tens of ms. The decay time of the luminescent material of the security feature (always considered from switching off the excitation source) is preferably in the range of 1ms to 50 ms. The luminescent material of the security feature particularly preferably has a decay time of 10ms to 30 ms.

In order to make the security feature detectable only by the mobile terminal device, in particular a smartphone, the luminescent material is configured such 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 emit this excitation radiation. Furthermore, the luminescent material is configured such that it emits in the visible spectral range, wherein this emission cannot be detected by visual perception by a user due to the short decay time.

The white light of the lighting unit of the smart phone is generated by an LED, the LED is composed of an LED semiconductor chip with the emission wavelength of about 450nm and an LED conversion luminescent material arranged above the LED semiconductor chip, wherein the conversion of the luminescent material converts the emission of the blue LED in portions into longer-wavelength visible luminescent radiation (broadband emission in the green, yellow and red spectral range) with an emission maximum peak of about 560nm, the white light of the LED provided as a lighting unit of commercially available smartphones results from the additive color mixing of the individual luminescent components, this means that the luminescent material that can be used to provide the security feature according to the invention is preferably configured such that it has a high efficiency of the excitability of the spectrum, in particular in the range of 420 to 470 nm.

The smartphone camera may be used as an image detection unit to detect the luminescent signal of the luminescent material. The image detection unit is preferably a CMOS sensor equipped with an IR filter, whereby the spectral sensitivity is up to about 750 nm. A single image, sequence of images or video can be acquired by the image detection unit.

In principle, the method according to the invention can be used in different pinging devices. This inspection device can be used as a retrofit module for fixed inspections (for example in automatic teller machines) or preferably be designed as a mobile terminal. The mobile terminal device is preferably a smartphone, but may also be a tablet computer or other similar multifunctional data processing device, which comprises a camera with an image detection unit and/or a lighting unit and which comprises a data processing unit. The data processing unit is preferably a processor, in particular a microprocessor. The verification may also be performed using a stationary terminal device or other data processing system with an image detection unit, such as a desktop display or a service terminal.

The luminescent material is preferably arranged in a patterned manner within the security feature. The luminescent material, in particular the luminescent pigment of the luminescent material, is preferably applied as a defined pattern on the carrier. The pattern may be arranged in the shape of e.g. a triangle or a star. Alternatively, the pattern of security features formed by the luminescent material may contain data and be arranged as a code, for example a QR code.

The pigments of the luminescent substance are printed as security features, for example, on the security document or on a layer of the security document. The printing or application of the luminescent material on the security document may be performed by known printing methods, such as gravure, flexography, offset printing, screen printing or digital printing methods. Furthermore, the luminescent material may be applied to the security document by a coating process or a lamination process.

A plausibility check and/or an integrity check may be performed. The security feature must be verified by selecting a luminescent material with a decay time in the ms range. It has proven advantageous if the particular choice of the luminescent material is such that the emission of the luminescent material can also be reliably measured after the end of the excitation process. Not only the luminescent material can be verified by decay time and emission spectrum, but also the pattern formed by the luminescent material can be verified as an additional security factor. Therefore, high security against forgery can be achieved by a combination of a plurality of factors. In order to authenticate the security document with the security feature more reliably, this security feature may be arranged, for example, in the region of a further security feature, for example, in the region of an image.

Security features may be applied to different security documents such as banknotes, identity cards, passports, driver licenses, tickets, stamps and the like.

Drawings

Further details, advantages and improvements of the invention result from the following description of preferred embodiments of the invention with reference to the drawings. Wherein:

figure 1 shows an embodiment of a security feature according to the present invention on a banknote;

FIG. 2 shows a schematic illustration of components of a facility for authenticating security features according to the present invention;

FIG. 3 shows a schematic diagram of the appearance and decay behavior of a luminescent material of a security feature upon flash excitation;

fig. 4 shows a flow chart for performing security feature verification with a facility according to the invention.

Detailed Description

Fig. 1 shows a security feature 01 according to the invention, which security feature 01 is applied to a document of value, namely a security document 02 illustrated symbolically in the form of a banknote. The security feature may be used to authenticate the security document 02. The security feature 01 here has a star shape. The security feature 01 is positioned below the visible feature 03 (here the denomination of the banknote). The security feature 01 consists of a luminescent material which is capable of being excited to luminesce by electromagnetic radiation having a predetermined wavelength, as described above, and which is explained in detail in the cited further patent applications of the applicant.

The security feature 01 may be verified by a method in which the authenticity of the security feature 01 is checked.

Fig. 2 shows a schematic arrangement for verifying a security feature 01, wherein the security feature 01 is excited to emit light by an illumination unit 04 of an image recording unit 06 of a mobile terminal, in particular a smartphone 07, in such a way that the illumination unit 04 generates excitation light Except for a flash 08. The flash 08 of the image detection unit 06 is generated by an LED emitting white light. Flash 08 has intensity I_A. After excitation, the luminescent material of the security feature 01 emits electromagnetic radiation, which occurs after the end of the excitation within a decay time in the ms range. The emission I of the luminescent material can be detected using the detector 09 or camera of the image acquisition unit 06_E. Furthermore, the detector 09 detects the ambient radiation I of the sunlight or room light impinging on the security feature 01 and the banknote 02 and reflecting there₀. In the method according to the invention, since the distance d between the security feature 01 and the smartphone 07 can be kept small, the ambient radiation I can be kept small₀Is kept low. Due to the small distance d, which is preferably smaller than the focusing area (focus) of the image recording unit 06, the smartphone 07 is largely shielded from ambient radiation I₀。

Fig. 3 shows a graph of the appearance and decay behavior of a luminescent material used in the security feature 01. In this graph, the emission curve 11 of the security feature 01 excited to emit light is illustrated along the time axis t. Further, a flash excitation curve 12 is plotted along the time axis. If a flash of light is generated by the smartphone 07 (fig. 2), the flash firing curve 12 rises steeply, maintains its level for a short time, and goes out after the flash of light. The luminescent material of the security feature 01 is excited to luminesce by the electromagnetic radiation of the flash, whereby its emission curve 11 rises almost simultaneously with the flash emission curve 12, usually with a decreasing slope. After the flash has extinguished, the emission curve 11 drops significantly more slowly than the flash excitation curve. According to the invention, the decay behavior of the luminescent material is in the range of ms.

The respective images 13 of the security features 01 detected by the detector 09 of the smartphone 07 (fig. 2) are shown below the time axis in fig. 3. The image recording 13 shows the attenuated radiation of the security feature 01 as a pattern that weakens over time. The pattern can be used in a further processing step for the verification of the security document 02. After the radiation has been substantially completely attenuated, the reference image 14b can be detected as the last image of the sequence of images taken. Depending on the evaluation method, an additional reference image 14a can also be taken before the excitation radiation is activated (triggering a flash). For example, additional checks of the security feature may be made by comparing the

reference images

14a and 14b with each other.

Fig. 4 shows in simplified form the principle sequence for verifying the security feature 01 by using the facility illustrated in fig. 3. In a locating step 41, the security document to be authenticated is located such that it can be reliably detected by the image detection unit of the smartphone. In an optional reference ping step 42, the starting image 14a of the security feature is generated before triggering the flash ignition of the smartphone. In a detection step 43, a single flash is triggered by means of the image capture unit and the illumination unit of the smartphone and an image sequence capture or video capture is carried out to record the luminescence signal of the luminescent material used to create the security feature, which is present after the end of the flash excitation and decays in the ms range. Finally, in a radiation analysis step 44, the captured image sequence is compared with the reference picture by the data processing unit. In addition to the calculation of image differences and their analysis, other image processing methods (for example contrast matching and histogram analysis for different color channels) can also be used here to verify in this way the emission characterization of the spectra of the luminescent substances used according to the invention and their proprietary attenuation characterization. Object recognition may be performed in an optional extraction step. The authenticity of the validated security document may be confirmed in the issuing step 45 by comparing the calculated parameters with authenticity parameters of the security feature, which are preferably stored in a data memory of the smartphone. In particular, by verifying security features on the security document, the trustworthiness and integrity of the security document may be confirmed.

List of reference numerals

01 Security feature

02 security document/banknote

03 denomination

04 Lighting Unit

05 -

06 image shooting unit

07 Intelligent mobile phone

08 flash

09 detector/camera

10

11 radiation curve

12 flash excitation curve

13 photo of security feature 01

14a starting image

14b reference image

41-45 method steps

Claims

1. A method for authenticating a luminescent material based security feature by a smartphone, the security feature comprising a luminescent material capable of being excited to emit, the luminescent material having a decay time in the ms range, the method comprising the steps of:

-exciting a luminescent material of the security feature by a lighting unit of the smartphone to cause it to emit;

-detecting radiation by capturing a sequence of images or video with an image detection unit of the smartphone during a predetermined decay time after the end of the excitation;

-evaluating the image sequence or video by means of a data processing unit of the smartphone, wherein the detected radiation during the decay time is compared with stored reference data to verify the authenticity of the security feature.

2. Method according to claim 1, characterized in that, for evaluating the image sequence, the following radiological characterization is known: decay time (τ), wavelength (λ), and/or color shift, and comparing the emission characterization to the reference data.

3. Method according to claim 1 or 2, characterized in that for detecting radiation, an image difference (Δ) between an image taken during the decay time and a reference image detected after the decay of the radiation is generated_1R＝B₁-B_{Reference to}…Δ_nR＝B_n-B_{Reference to}) And then calculating the radiation value as the hue value of different color channels through the RGB histogram, and then determining the decay time of the luminescent material according to the calculated radiation value.

4. A method according to any one of claims 1 to 3, characterized in that the following steps are carried out before the excitation of the luminescent material:

-performing object recognition by means of an image detection unit and a data processing unit of the smartphone to determine the location of the security feature on the security document or to correspond to a predetermined location box displayed within a display of the smartphone and to position the smartphone over the security document according to a location mark of the security document, the location box being arranged over the location mark;

-defining a camera box according to the determined positioning of the security feature, wherein the security feature is arranged in the area of the camera box;

-defining a reference area, which is arranged directly adjacent to the camera frame;

And after the excitation is finished, the detection of the image sequence is carried out in the region of the acquisition frame and in the reference region.

5. Method according to claim 4, characterized in that the image sequence detected within the capture frame is compared with the image sequence detected within the reference region by the data processing unit.

6. Method according to any one of claims 1 to 5, characterized in that the acquisition time is chosen such that the last image of the sequence of images is acquired after the end of the decay time and the security feature is verified as being true only if no radiation of the luminescent material can be detected in the last image.

7. The method according to claim 6, characterized in that the comparison of one or more images of the sequence of images of the positioning box with the last image of the sequence of images by the data processing unit of the smartphone is carried out in the following sub-steps:

-radiation recognition, wherein the image differences of the detected image and the reference image are known, respectively, an RGB histogram is created, the hue values of the different color channels are known, and the decay times of the luminescent material are known; and

-object recognition, wherein a shape analysis of the security feature is performed.

8. The method according to any one of claims 1 to 7, wherein the distance between the security feature and an image detection unit of the smartphone is selected to be smaller than a focus area of the image detection unit during excitation of the luminescent material and during detection of radiation.

9. Method according to one of claims 1 to 8, characterized in that an application (App) is installed on a mobile terminal device, which controls the lighting unit, the image detection unit and the data processing unit for implementing the method.