MOBILE IMAGE PROCESSING DEVICE FOR CAPTURING AN IMAGE OF A DOCUMENT

Description

[0001] The present disclosure relates to the field of document recognition.

[0002] The patent application DE 10 2011 121 566 A1 discloses a method for assisting a user in verifying the authenticity of a banknote.

[0003] The patent application DE 10 2018 102 015 A1 discloses a method for verifying the authenticity and / or integrity of a security document with a printed security feature.

[0004] Modern documents, such as identification documents, driver's licenses, vehicle registration documents, banknotes, or other official certificates, are typically equipped with optically detectable security features that allow for document authentication. These security features are optically detected and evaluated for document authentication purposes. Currently, however, such verifications are mostly only possible at fixed locations using complex detection devices, which are generally only available to a limited group of users.

[0005] It is therefore the object of the present invention to create a document presentation concept that, in particular, enables the highlighting of security features of the document.

[0006] This problem is solved by the features of the independent claims. Advantageous embodiments are the subject of the dependent claims, the description, and the accompanying figures.

[0007] The present disclosure is based on the finding that a security feature, which is arranged on or incorporated into a document, can be designed such that, when illuminated by a light source, in particular a white LED, the security feature can be at least partially detected by an image capture device, in particular a camera. The detected security feature can be highlighted in an image in such a way that a viewer of the image can detect the security feature. In particular, the detected security feature can be colored and / or overlaid. The highlighted security feature can also signal the authenticity of the document to the viewer. Furthermore, highlighting the security feature can provide an enhanced image in the sense of an "augmented reality" view.

[0008] According to a first aspect, the disclosure relates to a mobile image processing device for capturing an image of a document. The document has a security feature in a local document area, which comprises a wavelength-converting pigment. The mobile image processing device includes a light-generating device configured to illuminate the security feature with light of a first wavelength in order to excite the security feature to emit light of a second wavelength.

[0009] Furthermore, the mobile image processing device comprises an image acquisition device for capturing an image of the document, wherein the image acquisition device is further configured to capture the light emitted by the security feature in response to the illumination light in order to obtain an image of the security feature. The mobile image processing device further comprises a processor configured to capture the local document area in the image of the document; and an image display configured to display the image of the document and an image of the security feature superimposed on the local document area.

[0010] The mobile image processing device can be, in particular, a handheld telephone (smartphone), a mobile document processing device for capturing, in particular scanning, documents, or an augmented reality device, in particular augmented reality glasses, for overlaying the document with virtual content.

[0011] The document can be one of the following, with or without electronic components: an identity document such as a national identity card, passport, access control card, authorization card, company ID card, or credit card; a tax stamp or ticket; a birth certificate; a driver's license or vehicle registration document; a banknote, check, postage stamp; or another means of payment, such as a debit or credit card. The document can be single- or multi-layered and / or paper- and / or plastic-based. The document can be constructed from plastic-based films that are joined together to form a card body by gluing and / or laminating, with the films preferably having similar material properties.

[0012] The light-generating device can, in particular, comprise a light source configured to illuminate a detection area of ​​the image-capturing device. Specifically, the light-generating device can comprise a broad-spectrum light source that emits light in a sub-range of the wavelength range from 450 nm to 700 nm. In one embodiment, the light-generating device comprises a light-emitting diode (LED) that emits white light. Furthermore, the light-generating device can be configured to emit ultraviolet light and / or infrared light.

[0013] The light-generating device and, in particular, a light source included therein may be arranged next to the image-capturing device in order to achieve the highest possible brightness of the light reflected and / or emitted by the document and / or the security feature in response to the illumination by the light-generating device.

[0014] Responding to illumination by the lighting device, the security feature can be stimulated to emit light. In particular, the security feature can exhibit wavelength conversion properties, which can be realized, for example, through the use of a silicate compound such as silicate phosphorus. The light emitted by the security feature can have a wavelength that differs from the wavelength of the light absorbed by the security feature. The image can thus contain information about a wavelength spectrum emitted by the security feature when illuminated.

[0015] A security feature exhibiting wavelength conversion properties can, for example, comprise silicate pigments, particularly silicate phosphor pigments, silicate, sulfide, nitride, YAG, TAG, and thiogallate phosphor pigments, which are added to a printing ink. Such a security feature can, in response to excitation with blue light of approximately 400 nm wavelength, emit a color-shifted light spectrum that may include, for example, green, yellow, orange, and / or red light. Therefore, an LED whose light emission spectrum includes at least blue light in a wavelength range between 390 nm and 470 nm can be used to excite such a security feature.

[0016] The image acquisition device can, in particular, be a camera that captures the light reflected and / or emitted by the document and / or the security feature using an image sensor, in particular a CCD or CMOS sensor, and provides it as a pixel matrix, in particular with a number of color values ​​per pixel. The image acquisition device can further be configured to capture the document at a resolution above a predetermined resolution limit in order to achieve a sufficiently high-resolution image of the document and / or the security feature. The resolution limit can, in particular, be 75 ppi, preferably 150 ppi, and more preferably 300 ppi.

[0017] The processor can be configured to execute a program to highlight the security feature in the illustration. The program can be stored in an executable or compileable form in memory accessible to the processor. However, the processor can also be hardwired and thus configured in hardware to perform the detection and / or highlighting of the security feature in the illustration. This hardwiring can be implemented, for example, using an application-specific integrated circuit.

[0018] The detection of the security feature by the processor can be implemented, for example, using a pattern recognition program, where the processor is configured to recognize a regularity implemented in the security feature. Furthermore, the processor can be configured to recognize the security feature by comparing it with a plurality of images or security feature characteristics stored in memory and / or to determine the similarity of the depicted security feature to an expected representation of the security feature.

[0019] The image display can be a screen, in particular a liquid crystal display or OLED screen, configured to display the image and / or the superimposed image. Furthermore, the processor can be configured to select a portion of the image that includes the security feature and to use this portion to generate an expanded portion of the image with the security feature highlighted, and to provide this expanded portion to the image display. Similarly, the image display can be configured to display the expanded portion of the image to provide an enlarged representation of the highlighted security feature.

[0020] The processor can further be configured to determine the relative orientation of the document to the image capture device, in particular the image recording plane, based on the image. The processor can be configured to detect the relative orientation using edge detection and, based on this relative orientation, to determine a likely location and / or position of the security feature.

[0021] Furthermore, the processor can be configured to geometrically transform the image to generate an extended image that depicts the document and / or security feature free of perspective distortion. This geometric transformation may include distortion to achieve a particularly rectangular representation of the document in the extended image.

[0022] The superimposed image of the security feature can, for example, be a realistic representation of the security feature, depicting it true to life. In particular, the processor can be configured to take the illumination of the actual security feature into account when superimposing it with the realistic representation, in order to adjust the superimposition according to the expected light emission of the actual security feature under the given illumination. This allows, for example, a realistic representation of the superimposed security feature in the image.

[0023] Furthermore, the superimposed image of the security feature can be a schematic representation of the security feature, which, for example, highlights relevant features, in particular pigment zones of the security feature, in order to show or highlight recognition-relevant features of the security feature to a user.

[0024] According to the invention, the processor is configured to detect the security feature and, upon detection of the security feature in the local document area based on the image, insert a notification into the image. This notification is designed to alert a user of the mobile image processing device to the detection of the security feature. This offers the advantage, for example, of relieving the user of the burden of identifying the security feature, or at least making it easier. In particular, the probability of false positive and / or false negative verifications of the document can be reduced. Furthermore, document verification can be accelerated because the detection of the security feature is carried out by the mobile image processing device, and the user only needs to perceive the processed information to determine the presence of the security feature.

[0025] The indicator may be, in particular, a pictogram, a text element, and / or a graphic element, which is specifically designed to provide the viewer with visually perceptible confirmation that the security feature has been detected. Specifically, the indicator may include the text "TRUE" and / or, in the event that the security feature has not been detected, "FALSE".

[0026] According to the invention, the processor is configured to identify the document based on the detected security feature and / or the image of the document. Furthermore, the processor is configured to provide the viewer with identification information indicating the document's identification based on the document's identification. This offers the advantage, for example, that the document may be unknown to the viewer, yet it can still be detected and / or verified. Furthermore, document identification using the mobile image processing device is possible when identification by the viewer without the device is limited. In particular, document identification using the illumination provided by the light-generating device can be independent of ambient lighting.

[0027] Furthermore, the mobile image processing device may have an acoustic user interface and / or a haptic user interface, wherein the acoustic user interface may include a microphone and / or a loudspeaker and is configured to output the identification information by means of an acoustic signal. Furthermore, the haptic user interface may be configured to output the identification information haptically, in particular by means of a vibration signal. The mobile image processing device may have an electronic user interface configured to provide the identification information as an electronic message, in particular within a network.

[0028] In one embodiment, the processor is configured to distort a feature image relative to a perspectively distorted representation of the security feature, the local document area, and / or the document in the representation, in order to generate a feature image adapted to the perspective representation of the security feature, the local document area, and / or the document in the representation. The processor is further configured to superimpose the adapted feature image congruently with the security feature in the representation in order to highlight the security feature for a viewer. This achieves the advantage that a congruent representation of the feature image within the representation can be realized. For example, the feature image embedded in the representation can appear to a viewer of the representation as a highlighted, originally captured security feature.

[0029] In particular, the viewer of the image may be led to believe that the image adjustments made by the processor are identical to a real highlighting of the security feature on the document. Furthermore, perspective distortion can be used to combine real image content with virtual image content to create an augmented reality image.

[0030] In one embodiment, the image acquisition device is configured to capture light emitted by the security feature and / or the document, responding to illumination by the light-generating device, at a predetermined frame rate in order to obtain a plurality of images of the document with the security feature. The processor is configured to capture the local document area in the first image of the document within a time interval between a first image and a second image of the plurality of images, and the image display is configured to display the first image of the document with an image of the security feature superimposed on the local document area within the same time interval.

[0031] Furthermore, the image display can be configured to show continuously updated images. In particular, if there is relative movement between the image capture device and the document, and a corresponding adjustment of the superimposed image of the security feature, the viewer may be led to believe that the superimposed image of the security feature is connected to the originally depicted security feature, or that the security feature is perspectively extended by the superimposed image.

[0032] Furthermore, the advantage of accelerated document verification can be achieved, since it is not necessary to create a still image capture, but the overlay can be integrated into a continuously displayed series of images without a perceptible delay.

[0033] In one embodiment, the processor is configured to detect a screen printing element, which has an effect pigment, an organic or inorganic color pigment and / or a fluorescent printing element, as the security feature.

[0034] In one embodiment, the processor is configured to detect the security feature based on a partial feature area of ​​the security feature in the illustration, wherein the partial feature area represents a part of the security feature and is larger than a predetermined minimum feature area with respect to a display area that encompasses the entire security feature. This achieves the particular advantage that the security feature is only superimposed once a minimum feature area has been detected. Furthermore, in the case of a continuous display of the superimposition, if the visible partial feature area in the illustration falls below a further minimum feature area, the superimposition of the security feature can be prevented.In particular, the minimum feature sub-area can be larger than the further minimum feature sub-area in order to reduce the switching frequency between a mapping with superposition and a mapping without superposition.

[0035] Furthermore, the minimum feature sub-area can be chosen such that, by superimposing the security feature, a predetermined minimum probability of valid detection of the security feature is achieved. Accordingly, the advantage can be realized that an observer of the superimposed security feature can conclude, without further steps, that the document has been correctly identified and / or verified.

[0036] In one embodiment, the processor is configured to compare the detected security feature with a reference image of the security feature in order to verify the document based on the result of this comparison. The respective security feature can, in particular, be uniquely assigned to a document and / or a group of documents. Accordingly, the advantage can be achieved that the document, or at least the group of documents, can be detected and verified by identifying the security feature. Furthermore, the processor can be configured to detect other features of the document, in particular characters, images, color, and / or text blocks, in order to uniquely detect and verify the document based on at least one of these additional features in combination with the security feature.For example, the processor can be trained to distinguish between multiple banknotes with different values ​​based on the monetary values ​​shown in writing on the document and to verify each banknote using a common security feature.

[0037] In one embodiment, the processor is configured to insert a further indication into the image, in particular to overlay the image with the further indication, which contains information about the result of the security feature comparison, in order to indicate to the user whether the document has been successfully verified. In particular, the indication regarding the detection of the security feature and the further indication regarding the verification of the document can be linked and / or integrated into each other. For example, detection can be implemented by means of a pictogram and / or a text display, with verification being implemented by means of a predetermined color and / or a color change of the pictogram or the text display, respectively.

[0038] In one embodiment, the processor is configured to identify the security feature based on the image and to identify the document based on the identified security feature. This achieves the advantage of enabling document identification and detection of the security feature. In particular, the document can be identified solely on the basis of the security feature. Furthermore, additional information optically detectable from the image of the document can be used for document identification. The processor can be configured to identify the security feature based on the wavelength-converting pigment, the shape of the security feature, and / or the position of the security feature on the document. In particular, the processor can be configured to detect a positional deviation from an expected relative position of the security feature on the document.A positional deviation above a limit value and / or a shape deviation of the security feature from an expected shape may prevent verification of the document using the security feature.

[0039] In one embodiment, the image acquisition device is configured to provide the image in the form of a pixel matrix consisting of pixels with color values, and the processor is configured to generate a feature image in the form of a color adjustment of pixels representing the security feature in the image. The color-adjusted pixels are used to replace and / or superimpose the original pixels and create an enhanced image, with the image display configured to show the enhanced image. This offers the particular advantage of displaying the security feature in a color that contrasts with and / or highlights it in relation to the rest of the document. In particular, this can increase the contrast of the security feature with respect to the rest of the document. Furthermore, by means of a false-color display, the security feature can be shown in a color that differs from the originally captured color.For example, a custom color for overlaying the security feature can be set via a user interface.

[0040] Furthermore, the processor can be configured to overlay a document area surrounding the security feature in addition to the security feature itself, in order to facilitate the location of the security feature in the image, particularly at a reduced image scale. The processor can, in particular, be configured to overlay the security feature and / or the surrounding document area with a feature image of the security feature, wherein the feature image may be larger than the feature image originally depicted in the image.

[0041] In one embodiment, the processor is configured to detect pattern pixels in the pixel matrix that exhibit regularity, repetition, similarity, and / or regularities, and to detect the security feature based on these pattern pixels. In particular, the processor can be configured to detect the security feature using pattern recognition, in order to supplement or replace direct detection using the wavelength-converting pigment. The processor can also be configured to compare detected regularities and / or patterns with known or expected patterns in order to uniquely identify the security feature based on this comparison.

[0042] In one embodiment, the processor is configured to adjust the color values ​​of the pattern pixels in order to highlight the security feature represented by the pattern pixels in the extended image.

[0043] In one embodiment, the processor is configured to geometrically transform the image to generate a plane-parallel representation of the document depicted in the image to a display plane. This offers the advantage of correcting perspective distortions of the document, particularly to achieve a rectangular representation of the document in the image. This allows, for example, the proportions of document components, especially text elements and the security feature, to be transformed into an undistorted representation.

[0044] According to a second aspect, the disclosure relates to a method for capturing an image of a document, wherein the document has a security feature in a local document area which includes a wavelength-converting pigment. The method comprises illuminating the security feature with illumination light of a first wavelength by means of a light-generating device in order to excite the security feature to emit light of a second wavelength, and capturing the light emitted by the security feature in response to the illumination light by means of an image-capturing device in order to obtain an image of the security feature.

[0045] Furthermore, the method includes capturing the local document area in the image of the document using a processor, and displaying the image of the document and an image of the security feature superimposed on the local document area using an image display.

[0046] Further examples are explained with reference to the accompanying figure. It shows: Fig. 1 a mobile image processing device in one embodiment.

[0047] Fig. 1Figure 1 shows a schematic perspective view of a mobile image processing device 100 for capturing an image 117 of a document 101, wherein the document 101 has a security feature 105 with a wavelength-converting pigment 107 in a local document area 103. The mobile image processing device 100 comprises a light-generating device 109, which is configured to illuminate the security feature 105 with illumination light of a first wavelength in order to excite the security feature 105 to emit light of a second wavelength, and an image-capturing device 111 for capturing an image 117 of the document 101, wherein the image-capturing device 111 is configured to capture the light emitted by the security feature 105 in response to the illumination light in order to obtain an image 117 of the security feature 105.Furthermore, the mobile image processing device 100 comprises a processor 113, which is configured to capture the local document area 103 in the figure 117 of the document 101, and an image display 115, which is configured to display the figure 117 of the document 101 and a figure 117 of the security feature 105 superimposed on the local document area 103.

[0048] The light-generating device 109 and / or image acquisition device 111 can be arranged on a first side of the mobile image processing device 100. Furthermore, the image display 115 can be arranged on a second side of the device, opposite the first side. The image display 115 can, in particular, be aligned parallel to an image sensor of the image acquisition device 111 in order to display the image 117 on the image display 115 in a way that corresponds perspectively to the image captured by the image acquisition device 111.

[0049] In particular, the display of Figure 117 on the image display 115 can be implemented in such a way that a viewer of the image display 115 has the impression of looking through the mobile image processing device 100 at the document 101, whereby the highlighting of the security feature 105 is implemented in such a way that the viewer is given the impression that the corresponding marking of the security feature 105 is attached to the actual security feature 105 on the document 101. Accordingly, based on the illumination provided by the lighting device 111 and the correspondingly acquired color values, an overlay can be adjusted to reduce any color difference and / or contrast difference of the overlay in relation to the other parts of the document shown.

[0050] Furthermore, the processor 113 can be configured to adapt the overlay of the security feature 105 to the resulting new position of the security feature 105 during a relative movement between document 101 and image capture device 111, wherein a latency time between sensing the new position of the security feature 105 and displaying the overlay is below a user perception threshold in order to achieve a representation of the overlay that adheres to the document 101.

[0051] The processor 113 can further be trained to detect the security feature 105 and, upon detection of the security feature 105 in the local document area 103 based on Figure 117, insert a note 119 into Figure 117, which is trained to notify a user of the mobile image processing device 100 of the detection of the security feature 105.

[0052] Furthermore, the processor 113 is configured to identify the document 101 based on the detected security feature 105 and the image 117 of the document 101. The processor 113 is further configured to provide the viewer with identification information, indicated by the message 119, based on the identification of the document 101. Additionally, if identification is not possible, a corresponding warning message can be displayed.

[0053] The processor 113 is configured to distort a feature image with respect to a perspectively distorted representation of the security feature 105, the local document area 103, and / or the document 101 in Figure 117, in order to generate a feature image adapted to the perspective representation of the security feature 105, the local document area 103, and / or the document 101 in Figure 117. The processor 113 is further configured to superimpose the adapted feature image onto the security feature 105 in Figure 117 so that it is congruent with the security feature 105 in Figure 117, in order to highlight the security feature 105 for a viewer.

[0054] The image acquisition device 111 is configured to capture light emitted by the security feature 105 and the document 101, responding to illumination by means of the light-generating device 109, at a predetermined frame rate in order to obtain a plurality of images of the document 101 with the security feature 105. The processor 113 is configured to capture the local document area 103 in the first image of the document 101 within a time interval between a first image and a second image of the plurality of images, and the image display 115 is configured to display the first image of the document 101 with an image of the security feature 105 superimposed on the local document area 103 within the time interval between the first image and the second image.

[0055] Furthermore, the processor 113 is designed to detect a screen printing element which has an effect pigment, an organic or inorganic color pigment and / or a fluorescent printing element as the security feature 105.

[0056] Furthermore, the processor 113 is configured to detect the security feature 105 based on a feature sub-area of ​​the security feature 105 in Figure 117, wherein the feature sub-area represents a part of the security feature 105 and is larger than a predetermined minimum feature sub-area with respect to a representation area that captures the entire security feature 105.

[0057] The detected security feature 105 can be compared with a reference image of security feature 105 by processor 113 in order to verify document 101 based on the result of the comparison. Furthermore, processor 113 is configured to overlay image 117 with an additional indicator containing information about the result of the security feature comparison, thus indicating to the user whether document 101 has been successfully verified. Based on the identified security feature 105, document 101 can be identified by processor 113.

[0058] The image acquisition device 111 is further configured to provide the image 117 in the form of a pixel matrix of pixels with color values, wherein the processor 113 is configured to generate a feature image in the form of a color adjustment of pixels that depict the security feature 105 in the image 117, in order to replace the original pixels with the color-adjusted pixels and to generate an extended image, wherein the image display 115 is configured to display the extended image.

[0059] Processor 113 is further configured to detect pattern pixels in the pixel matrix that exhibit regularity, repetition, similarity, and / or regularities, and to detect the security feature 105 based on these pattern pixels. Furthermore, processor 113 can adjust the color values ​​of the pattern pixels to highlight the security feature 105, which is represented by the pattern pixels, in the extended image.

[0060] Furthermore, the processor 113 is configured to geometrically transform the figure 117 in order to generate a plane-parallel representation of the document 101 depicted in the figure 117 to a display plane of the image display 115. In particular, any curvature of the document 101, an oblique view of the document 101, and / or a wavy, bent, and / or folded shape of the document 101 can be eliminated by means of the transformation in order to achieve a representation of the document 101 without distortion artifacts. Reference symbol list

[0061] 100 Mobile image processing device 101 Document 103 Local document area 105 Security feature 107 Wavelength-converting pigment 109 Light-generating device 111 Image acquisition device 113 Processor 115 Image display 117 Illustration 119 Note

Claims

1. Mobile image processing apparatus (100) for capturing an image (117) of a document (101), wherein the document (101) comprises a security feature (105) in a local document area (103), wherein the security feature (105) comprises a wavelength-converting pigment (107), the mobile image processing apparatus (100) comprising: a light-generating device (109), which is configured to illuminate the security feature (105) with illumination light of a first wavelength of light in order to excite the security feature (105) to emit light of a second wavelength; an image capture device (111) for capturing an image (117) of the document (101), wherein the image capture device (111) is further configured to capture the light emitted by the security feature (105) in response to the illumination light in order to obtain an image (117) of the security feature (105); a processor (113), which is configured to capture the local document area (103) in the image (117) of the document (101); and an image display (115), which is configured to display the image (117) of the document (101) and an image of the security feature (105) superimposed on the local document area (103), wherein the processor (113) is configured to detect the security feature (105) and, upon detection of the security feature (105) in the local document area (103) based on the image (117), to insert an indicator (119) into the image (117), the indicator (119) being adapted to indicate to a user of the mobile image processing apparatus (100) the detecting of the security feature (105), characterized in that the processor (113) is configured to identify the document (101) on the basis of the captured security feature (105) and / or the image (117) of the document (101), and wherein the processor (113) is further configured to provide the user with identification information on the basis of the identification of the document (101) by means of the indicator (119), which identification information indicates the identification of the document (101).

2. Mobile image processing apparatus (100) according to one of the preceding claims, wherein the processor (113) is configured to distort a feature image with respect to a perspectively distorted image of the security feature (105), the local document area (103) and / or the document (101) in the image (117) in order to generate a feature image adapted to the perspective image of the security feature (105), the local document area (103) and / or the document (101) in the image (117), wherein the processor (113) is further configured to superimpose the adapted feature image congruently with the security feature (105) in the image (117) in order to highlight the security feature (105) for a user.

3. Mobile image processing apparatus (100) according to one of the preceding claims, wherein the image capture device (111) is configured to capture light emitted by the security feature (105) and the document (101) at a predetermined frame rate in response to illumination by means of the light-generating device (109) in order to obtain a plurality of images of the document (101) with the security feature (105), wherein the processor (113) is configured to capture the local document area (103) in the first image of the document (101) within a time interval between a first image and a second image of the plurality of images, and the image display (115) is configured to display the first image of the document (101) with an image of the security feature (105) superimposed on the local document area (103) within the time interval between the first image and the second image.

4. Mobile image processing apparatus (100) according to one of the preceding claims, wherein the processor (113) is configured to detect a screen printing element comprising an effect pigment, an organic or inorganic color pigment and / or a fluorescent printing element as the security feature (105).

5. Mobile image processing apparatus (100) according to one of the preceding claims, wherein the processor (113) is configured to detect the security feature (105) by means of a feature sub-area of the security feature (105) in the image (117), wherein the feature sub-area represents a part of the security feature (105) and is larger than a predetermined minimum feature sub-area with respect to an image area which captures the entire security feature (105).

6. Mobile image processing apparatus (100) according to one of the preceding claims, wherein the processor (113) is configured to compare the detected security feature (105) with a reference image of the security feature (105) in order to verify the document (101) based on the result of the comparison of the security feature (105) with the reference image.

7. Mobile image processing apparatus (100) according to claim 6, wherein the processor (113) is configured to insert a further indication into the image (117) which comprises information about the result of the security feature comparison in order to indicate to the user whether the document (101) has been successfully verified.

8. Mobile image processing apparatus (100) according to one of the preceding claims, wherein the processor (113) is configured to identify the security feature (105) on the basis of the image (117) and to identify the document (101) on the basis of the identified security feature (105).

9. Mobile image processing apparatus (100) according to one of the preceding claims, wherein the image capture device (111) is configured to provide the image (117) in the form of a pixel matrix of pixels with color values, and wherein the processor (113) is configured to generate a feature image in the form of a color adjustment of pixels that depict the security feature (105) in the image (117) in order to replace the original pixels with the color-adjusted pixels and to generate an extended image, wherein the image display (115) is configured to display the extended image.

10. Mobile image processing apparatus (100) according to claim 9, wherein the processor (113) is configured to detect pattern pixels in the pixel matrix which exhibit regularity, repetition, similarity and / or regularities and to detect the security feature (105) on the basis of the pattern pixels.

11. Mobile image processing apparatus (100) according to claim 9 or 10, wherein the processor (113) is configured to adjust the color values of the pattern pixels in order to highlight the security feature (105) represented by the pattern pixels in the enhanced image.

12. Mobile image processing apparatus (100) according to one of the preceding claims, wherein the processor (113) is configured to geometrically transform the image (117) in order to generate a plane-parallel image of the document (101) depicted in the image (117) to a display plane of the image display (115).

13. Method for capturing an image (117) of a document (101), wherein the document (101) comprises a security feature (105) in a local document area (103), wherein the security feature (105) comprises a wavelength-converting pigment (107), the method comprising: illuminating the security feature (105) with illumination light of a first wavelength by a light-generating device (109) in order to excite the security feature (105) to emit light of a second wavelength; capturing the light emitted by the security feature (105) in response to the illumination light by an image capture device (111) in order to obtain an image (117) of the security feature (105); capturing the local document area (103) in the image (117) of the document (101) by a processor (113); displaying the image (117) of the document (101) and an image (117) of the security feature (105) superimposed on the local document area (103) by an image display (115); detecting the security feature (105) and inserting an indicator (119) into the image (117), the indicator (119) being adapted to indicate to a user of the mobile image processing apparatus (100) the detecting of the security feature (105), by capturing the security feature (105) in the local document area (103) based on the image (117) using the processor (113); identifying the document (101) based on the captured security feature (105) and / or the image (117) of the document (101); and characterized in providing the user with identification information by means of the indicator (119) on the basis of the identification of the document (101), which identification information indicates the identification of the document (101).