METHOD AND DEVICE FOR DETERMINING A DIGITAL BIOMETRIC PASSPORT IMAGE FOR A SECURITY DOCUMENT AND METHOD FOR PERSONALIZING A SECURITY DOCUMENT

Description

[0001] The invention relates to a method and a device for determining passport photo data representing a digital biometric passport photo for a security document from video image recordings and to a method for personalizing a security document. background

[0002] It is known to identify individuals using biometric facial features. In conjunction with security documents such as ID cards or passports, such biometric facial features can be derived from biometric passport photos on the security document. The biometric passport photo personalizes the security document and allows the individual to be identified, optionally in conjunction with other security elements of the security document.

[0003] To determine passport photo data representing a digital biometric passport photograph of a person, individual images are typically captured using a camera device. If, after an image has been captured, it is determined that one or more criteria for suitability as a biometric passport photograph are not met, one or more additional individual images may be taken.

[0004] Document EP 1 413 972 A1 provides a testing method for digitized images of people, as well as devices for implementing the method. The method is particularly suitable for checking the suitability of a person's image for personal identification. It comprises the steps of segmenting the person's image into a background area and a head or face area, analyzing the head or face area to determine at least one characteristic value, and comparing the at least one characteristic value with at least one predetermined threshold value.

[0005] The documents DE 10 2013 203 433 A1 and US 2016 / 012279 A1 relate to a device for capturing personal data of a person, wherein the personal data comprises a facial image of the person. The device comprises a camera for capturing the facial image of the person, an illumination device, and a semi-transparent mirror. The semi-transparent mirror is arranged between the person and the camera, wherein the semi-transparent mirror is aligned such that, on the side of the semi-transparent mirror facing the person, the beam path of light incident on the semi-transparent mirror is parallel to the beam path of the portion of this light reflected back by the semi-transparent mirror. The illumination device is designed for frontal illumination of the person.The device further comprises a control unit for carrying out image capture by generating light by the illumination device for illuminating the face of the person and, during the illumination, capturing a first image of the face of the person by the camera, capturing a second image of the face of the person by the camera without generating the light, forming a first difference image of the first image and the second image, wherein in the first difference image the face of the person is isolated from the background, wherein the person-specific data comprises the first difference image as the face image.

[0006] Documents US 2013 / 215275 A1 and US 2016 / 154991 A1 describe a biometric and identity registration kiosk for collecting personal data. The device comprises a movable main module and at least one modifiable section removably coupled to the main module. The main module comprises a processor and one or more biometric capture devices coupled to the processor, which may include a facial camera.

[0007] Document US 2019 / 082100 A1 describes a method for capturing a photograph for use in a personal photo identification device. The method includes using a digital image capture system with a digital camera, a computer processor, and memory for storing specifications and requirements for a photographic print to be compliant for use in a user-selected photo identification device, such as a passport for a selected country or jurisdiction. The digital image capture system is used to capture a facial image; facial image processing techniques are used to automatically detect a face and facial feature points on the facial image; the facial image is processed, and a visual indication of compliance is generated; and upon compliance, the photograph is generated based on the compliant facial image. Summary

[0008] The object of the invention is to provide a method and a device for determining passport photo data representing a digital biometric passport photo for a security document, with which the process of generating the passport photo data can be carried out efficiently and with reduced susceptibility to errors. Furthermore, a method for personalizing a security document is to be improved in this context.

[0009] To achieve this object, a method and a device for determining passport photo data representing a digital biometric passport photo for a security document are provided according to independent claims 1 and 14. Furthermore, a method for personalizing a security document is provided according to the co-located claim 12. Embodiments are the subject of dependent subclaims.

[0010] According to one aspect, a method for determining passport photo data representing a digital biometric passport photo for a security document is provided, comprising the following steps: capturing a sequence of portrait images for a person by means of video image recording with a frame rate and a recording resolution for the portrait images using a video image recording device; storing respective portrait image data with the recording resolution and portrait image data with a resolution reduced compared to the recording resolution for the portrait images from the video image recording; and determining passport photo data representing a digital biometric passport photo of the person from the portrait images of the video image recording. Determining the passport photo data comprises the following: selecting first portrait images from the sequence of portrait images;Determining whether the portrait image data associated with each of the first portrait images meets first test criteria regarding suitability for a digital biometric passport photo of the person, wherein the testing is performed for the portrait image data with the reduced resolution; Selecting one of the first portrait images for which the associated portrait image data meets at least a necessary subset of the first test criteria; Determining whether the portrait image data associated with one of the first portrait images meets second test criteria regarding suitability for the digital biometric passport photo of the person, wherein the second test criteria are different from the first test criteria and the testing is performed for the portrait image data with the reduced resolution;and generating the passport photo data using the portrait photo data with the recording resolution associated with one of the first portrait photos, if the portrait photo data with the reduced resolution associated with one of the first portrait photos satisfy at least a necessary subset of the second test criteria;

[0011] According to a further aspect, a device for determining passport image data representing a digital biometric passport image for a security document is provided, comprising a passport image recording device configured for the following: recording a sequence of portrait images for a person by means of video image recording with a frame rate and a recording resolution for the portrait images by means of a video image recording device; storing respective portrait image data with the recording resolution and portrait image data with a resolution reduced compared to the recording resolution for the portrait images from the video image recording; and determining passport image data representing a digital biometric passport image of the person from the portrait images of the video image recording.

[0012] Furthermore, in connection with determining the passport photo data, the device is configured for the following: selecting first portrait images from the sequence of portrait images; determining whether the portrait image data associated with each of the first portrait images satisfy first test criteria with regard to suitability for a digital biometric passport photo of the person, wherein the testing is carried out for the portrait image data with the reduced resolution; selecting one of the first portrait images for which the associated portrait image data satisfy at least a necessary subset of the first test criteria; determining whether the portrait image data associated with one of the first portrait images satisfy second test criteria with regard to suitability for the digital biometric passport photo of the person, wherein the second test criteria are different from the first test criteria and the testing is carried out for the portrait image data with the reduced resolution;and generating the passport photo data using the portrait photo data with the recording resolution associated with one of the first portrait photos, if the portrait photo data with the reduced resolution associated with one of the first portrait photos satisfy at least a necessary subset of the second test criteria;

[0013] According to another aspect, a method for personalizing a security document is provided, comprising the following steps: determining passport photo data representing a digital biometric passport photo; providing the passport photo data in a personalization device; providing a security document; and personalizing the security document, wherein the passport photo data are processed in the personalization device and a representation of the digital biometric passport photo is applied to the security document.

[0014] The proposed technology makes it possible to determine the passport photo data representing a digital biometric passport photo from the video images themselves. This eliminates the need for a (supplementary) individual image recording, as is known in the prior art, if the person can be given instructions via video image prior to the individual image recording, for example, regarding correct head position and alignment, in order to then record individual images using another camera and process them. Thus, a method and a device for determining passport photo data from video images are provided. The video images are recorded using a video image recording device provided with the passport photo recording device and processed using a data processing device to generate the passport photo data.The data processing device can be part of the passport photo recording device or at least partially separate therefrom. During the video image recording, a sequence of portrait or facial images is captured at the frame rate (of the video image stream) at a recording resolution. The portrait image data, each representing the recorded portrait images of the person, is stored in a storage device using first and second portrait image data, wherein the first and second portrait image data represent the associated portrait image at different resolutions, namely the original recording resolution (during the video image recording) and a reduced resolution compared to this. Alternatively, the first portrait image data can also be stored at a reduced resolution compared to the recording resolution, wherein the second portrait image data then has a (further) reduced image resolution compared to this.It may be provided that the portrait image data is stored in a common memory (. "shared memory" ) which can be accessed jointly and in a coordinated manner by several data processing processes.

[0015] The portrait image data with the reduced resolution is analyzed or processed to determine whether the test criteria regarding suitability for a digital biometric passport photo of the person are met. For example, several first and several second test criteria are examined. If the portrait data with the reduced resolution for one of the portrait images fulfills at least a subset of the first and at least a subset of the second test criteria, the passport photo data that represents the digital biometric passport photo for the person is determined from this. When checking for the second test criteria, portrait image data that do not fulfill at least the required subset of the first test criteria are disregarded.

[0016] The required subset of test criteria can be defined depending on the application and stipulates that not all of the respective test criteria must necessarily be met by the examined portrait image data, but only a minimum number. In alternative embodiments, it can be provided that the portrait image data for the first test criteria and / or the second test criteria must meet all of the actually examined test criteria in order to be determined as suitable for the digital biometric passport photo. The required subset of test criteria can specify a minimum number of test criteria that must be met, whereby it is not important which of the test criteria are met. Alternatively, it can be provided that the required subset specifies test criteria of a certain type that must necessarily be met in order to determine suitability for the digital biometric passport photo.If a weighted order is given for the test criteria, it can be provided that the test criteria are checked one after the other according to the weighted order and that the test is aborted when the necessary subset is met, for example a minimum number.

[0017] In one embodiment, the passport photo data can be determined using a data processing process that is implemented at least partially using an FPGA component, wherein the data processing process has access to the storage medium containing the portrait image data at different resolutions. This embodiment can advantageously support the parallelization of data processing processes.

[0018] The recording of a sequence of portrait images for the person using video recording and the storage of the respective portrait image data at the recording resolution and portrait image data with the reduced resolution for the portrait images can be continued at least temporarily while the passport image data is being determined. The process of recording and saving the portrait images recorded during the video recording continues, while the passport image data is being determined in real time from previously recorded portrait images from the video recording. The continuation of the recording of portrait images using video recording can be continuous (continuous) or interrupted while the passport image data is being determined.Data processing processes for storing the portrait image data and for determining the passport photo data are parallelized and can be executed on the same or different data processing components, for example an FPGA module and one or more processors.

[0019] The recording of the sequence of portrait images for the person using video recording can be terminated once the passport photo data has been generated. Once the passport photo data for the person representing or displaying the digital biometric passport photo has been generated, the video recording is automatically terminated, which can occur in response to a corresponding control signal to the video recording device. Until this point, the recording of the portrait images using video recording can continue.

[0020] The portrait images from the video recording can be displayed to the person in real time as a video image output on a display device connected to the passport photo recording device. In this embodiment, the recorded portrait images are shown in real time on the person's display device, parallel to the recording, which then occurs in parallel with the determination of the passport photo data. The person receives a type of feedback about the video recordings and can optionally make changes independently, for example, regarding the head position or the direction of gaze.

[0021] After the passport photo data has been generated, the person's digital biometric passport photo can be displayed on the display device. In this embodiment, the digital biometric passport photo displayed by the passport photo data is brought to the person's attention via the display device. This can be carried out in parallel with the ongoing video image recording and its output via the display device. A separate display window can be used on the display device to bring the person's biometric passport photo to their attention. After the digital biometric passport photo has been displayed on the display device, the passport photo recording device can receive a user input from the person indicating the person's consent to the biometric passport photo. The ongoing video image recording can then be ended.Further processing of the passport photo data can also be started in response to the user input.

[0022] The passport photo data can be transmitted to a personalization device configured to process the passport photo data such that a representation of the digital biometric passport photo is applied to a document body for a security document. The passport photo data can be transmitted to the personalization device in the form of a passport photo data file. The passport photo data can be transmitted to the personalization device after the passport photo data has been generated. Alternatively, it can be provided that the passport photo data is only transmitted to the personalization device after a user input regarding the person's consent to the biometric passport photo has been received.The personalization device serves to personalize the security document by applying a representation of the digital biometric passport photo to it, for example by printing the passport photo and / or storing the passport photo data in a storage element of the security document.

[0023] Furthermore, the method can provide the following: selecting second portrait images from the sequence of portrait images that are different from the first portrait images if it is determined for none of the first portrait images that the associated portrait image data fulfills the necessary subset of the first and the necessary subset of the second test criteria; determining the portrait image data associated with the second portrait images in accordance with determining the portrait image data associated with the first portrait images; and generating the passport image data using portrait image data associated with one of the second portrait images if the portrait image data fulfill at least the necessary subset of the first test criteria and at least the necessary subset of the second test criteria.This process involves selecting additional portrait images from the ongoing video data stream if none of the initial portrait images meets the necessary test criteria for suitability as a digital biometric passport photograph. This process can be repeated multiple times by selecting additional portrait images until at least one of the portrait images meets the necessary test criteria for suitability as a digital biometric passport photograph. Parallel to the (ongoing) recording of the sequence of portrait images using video image recording, previously captured portrait images are checked for their suitability for the digital biometric passport photograph. If the associated portrait image data for at least one of the portrait images meets the required test criteria, the passport photograph data can be determined from this.

[0024] The initial test criteria can include one or more of the following: illumination of the portrait image, background of the portrait image, image contrast, head position, eyes and direction of gaze, headgear, and fit of glasses. The initial test criteria allow the portrait image data to be tested for its biometric suitability, i.e., its suitability for performing biometric facial recognition on the passport photo represented by the portrait image data. For example, such suitability for biometric facial recognition can be determined if at least the following initial test criteria are met: frontal image capture, defined head position in the portrait image, structureless background, neutral facial expression, and sufficient illumination (without reflections or shadows on the face or background).

[0025] From the first portrait images, an unsuitable portrait image can be determined for which the associated portrait image data do not meet the necessary subset of the first test criteria, wherein at least one of the following steps is provided: (i) generating control data in response to the detection of an error, in that one of the first test criteria is not met in the unsuitable portrait image, wherein the control data is configured to control an output to the person via an output device, and wherein a user instruction for correcting the error is output to the person with the output; and (ii) generating further control data in response to the detection of a further error, in that another of the first test criteria is not met in the unsuitable portrait image, wherein the further control data is configuredto change an operating parameter of the video image recording device and / or a lighting device associated with the video image recording device for recording the sequence of portrait images. An error can be detected, for example, if the person in the examined portrait image is wearing a hat, the eyes are closed, the gaze is not directed forward, and / or hair covers one eye. The control data generated upon detection of such an error is configured to output a user notification to the person, be it in visual and / or acoustic form.to prompt the person to correct the error. The additional control data for detecting the further error can, for example, relate to a changed camera setting for the video image recording device and / or a changed setting of the lighting device for better illumination. Intuitive user guidance using the control data can be provided, for example, the output of user instructions via a display device, which, for example, prompts the person to change their direction of view.

[0026] The second test criteria can be used to verify whether the portrait image data represents a digital biometric passport photo that meets the ICAO standard for passport photos for machine-readable security documents. For example, the second test criteria can be used to verify whether the portrait image data meets the following standard: "Technical Report - Portrait Quality (Reference Facial Images for MRTD)"(Version 1.0 from April 2018 or later). This defines standard criteria that portrait or facial image data must meet to be suitable as a digital biometric passport photo for a machine-readable security document.

[0027] The sequence of portrait images can be recorded during video image recording at a frame rate between approximately 10 frames per second and approximately 30 frames per second.

[0028] When applying the representation of the digital biometric passport photo to the security document, a biometric passport photo can be printed and / or the passport photo data can be stored in an electronic storage element of the security document.

[0029] The embodiments explained above in connection with the method for determining passport photo data for a digital biometric passport photo can be provided accordingly in connection with the device for determining passport photo data and / or the method for personalizing a security document. Description of implementation examples

[0030] Further embodiments are explained in more detail below with reference to the figures of a drawing. Herein: Fig. 1 shows a schematic representation of an arrangement for a device for determining passport photo data, which is optionally connected to a personalization device; and Fig. 2 shows a schematic block diagram of a method for determining passport photo data representing a digital biometric passport photo for a security document.

[0031] Fig. 1shows a schematic representation of an arrangement for a device for determining passport photo data representing a digital biometric passport photo for a security document 1. Fig. 2 shows a schematic block diagram of a method for determining passport photo data.

[0032] With the aid of a video image recording device 2, which, for example, is formed with a video camera and, in the example shown, is provided as part of a passport photo recording device 3, portrait or facial images of a person 4 are recorded in step 20 as part of a video image recording. With the aid of a data processing device 5, which is connected to the video image recording device 2, the portrait images contained in the video data stream with a frame rate are stored in a storage device 6 as digital portrait image data (step 21). In this case, portrait image data are stored with a recording resolution that corresponds to the image resolution when the portrait images were recorded during the video image recording. In addition, portrait image data for each portrait image is stored in the storage device with a resolution that is reduced compared to the recording resolution.

[0033] In step 22, first portrait image data are selected from the sequence of portrait images for a process for determining passport image data representing a digital biometric passport image of person 4. For the portrait image data assigned to the first portrait images, it is determined whether they meet initial test criteria regarding suitability for the digital biometric passport image of person 4 (step 23). This test is performed for the portrait image data with the reduced resolution. The initial test criteria can include test criteria from the following group: illumination of the portrait image, background of the portrait image, image contrast, head position, eyes and direction of gaze, headgear, and fit of glasses.

[0034] If it is determined for the portrait image data of at least one of the first portrait images that a predetermined set of first test criteria is met, that one of the first portrait images is selected for further testing with regard to its suitability for the digital biometric passport photo (step 24). As part of the further testing, second test criteria, which are different from the first test criteria, are checked for the portrait image data of the selected portrait image. The test with regard to the second test criteria is also carried out for the portrait image data with the reduced resolution. The second test criteria can be used to check whether the portrait image data is a digital biometric passport photo in accordance with the ICAO standard for passport photos for machine-readable security documents. For example, the standard can be "Technical Report - Portrait Quality (Reference Facial Images for MRTD)" in version 1.0 from April 2018 or a more recent version.

[0035] If it is determined that the examined portrait image data also fulfill at least a necessary subset of the second test criteria, passport image data are generated in step 25 that represent or display the digital biometric passport image for person 4. The passport image data determines image data that enable biometric personal identification based on biometric facial features.

[0036] The passport photo data can then be optionally transmitted in step 26 to a personalization device 7, which is configured to personalize the security document 1. For this purpose, the personalization device 7 can be designed with a printing device by means of which the biometric passport photo is printed on the security document 1. Alternatively or additionally, the passport photo data can be stored in a storage device 8 of the security document 1. This personalized the security document and enables personal identification based on the biometric passport photo.

[0037] While the passport photo data of the digital biometric passport photo is being determined, the recording of the portrait images via video recording can continue, so that new portrait image data is continuously provided, which is used when determining the passport photo data, until it is determined for at least one of the portrait images from the video image recording that the first and second test criteria regarding suitability for the digital biometric passport photo are met. Once the passport photo data has been generated, the video image recording is then terminated.

[0038] If, when checking the portrait image data with regard to the first test criteria, an error is detected which indicates the non-fulfillment of at least one of the first test criteria, control data can then be generated in the passport photo recording device 3 in order to influence the further recording of portrait images by means of video recording, such that improved portrait images are recorded. In one embodiment, it can be provided that the control data is configured to control an output via an output device 9 to the person 4 such that a user instruction for correcting the error is issued to the person 4, which can comprise a visual and / or acoustic instruction to the person, for example a request to remove a head covering and / or a request to open both eyes. Similar user instructions can relate to a correction of the direction of gaze or the covering of one eye by hair on the face of the person 4.The output device 9, which can be formed, for example, with a display, can optionally be integrated into the passport photo recording device 3, for example when formed in a terminal device for capturing personal data for the security document 1. The output device 9 can be designed as an input / output device for receiving user inputs.

[0039] Alternatively or additionally, in response to the detection of an error, control data can be generated which are configured to improve an operating parameter of the video image recording device 2 and / or of an illumination device associated therewith for further portrait images within the scope of the video image recording, for example for improved illumination of the portrait images.

[0040] In this way, the portrait images captured during video capture at the frame rate are optimized in real time in response to the detection of an error. Such optimization processes can be executed until it is determined for at least one of the portrait images that both the first and second test criteria are met, so that the passport photo data can be generated. The detection of errors during the verification of the first test criteria is fed back into the process of capturing the portrait images via video capture in order to ultimately provide suitable portrait image data for the digital biometric passport photo via video capture.

[0041] The features disclosed in the above description, the claims and the drawings may be important for the realization of the various embodiments both individually and in any combination. List of reference symbols

[0042] 1Security document 2Video image recording device 3Passport photo recording device 4Person 5Data processing device 6Storage device 7Personalization device 8Storage device of the security document 1 9Output device 20, .., 26Procedure steps

Claims

1. A method for determining passport image data representing a digital biometric passport image for a security document (1), comprising: - recording a sequence of portrait images for a person (4) by means of video image recording at a frame repetition rate and a recording resolution for the portrait images by means of a video image recording device (2); - storing respective portrait image data with the recording resolution and portrait image data with a reduced resolution compared to the recording resolution for the portrait images from the video image recording; and - determining passport image data representing a digital biometric passport image of the person (4) from the portrait images of the video image recording, comprising: - selecting first portrait images from the sequence of portrait images; - determining whether the portrait image data, which are respectively associated with the first portrait images, satisfy first test criteria with respect to a suitability for a digital biometric passport image of the person (4), wherein the test for the portrait image data is performed with the reduced resolution; - selecting one of the first portrait images for which the associated portrait image data satisfy at least a necessary subset of the first test criteria; - determining whether the portrait image data, which are associated with the one of the first portrait images, satisfy second test criteria with respect to the suitability for the digital biometric passport image of the person (4), wherein the second test criteria are different from the first test criteria and the test for the portrait image data is performed with the reduced resolution; and - generating the passport image data using the portrait image data associated with the one of the first portrait images with the recording resolution if the portrait image data with the reduced resolution, which are associated with the one of the first portrait images, satisfy at least a necessary subset of the second test criteria.

2. The method according to claim 1, characterized in that the recording of the sequence of portrait images for the person (4) by means of video image recording and the recording of respective portrait image data with the recording resolution and portrait image data with the reduced resolution for the portrait images is continued at least temporarily during the determining of the passport image data.

3. The method according to claim 2, characterized in that the recording of the sequence of portrait images for the person (4) by means of video image recording is ended if the passport image data have been generated.

4. The method according to at least one of the preceding claims, characterized in that the portrait images from the video image recording are displayed in real time to the person (4) as a video image output on a display device connected to the video image recording device.

5. The method according to at least one of the preceding claims, characterized in that after the generation of the passport image data the digital biometric passport image of the person (4) is displayed on the display device.

6. The method according to at least one of the preceding claims, characterized in that the passport image data are transmitted to a personalization device (7) configured to process the passport image data such that a representation of the digital biometric passport image is applied to a document body for a security document.

7. The method according to at least one of the preceding claims, characterized in that the following is further provided: - selecting second portrait images from the sequence of portrait images, which are different from the first portrait images, if it is not determined for any of the first portrait images that the associated portrait image data satisfy the necessary subset of the first and the necessary subset of the second test criteria; - determining the portrait image data associated with the second portrait images according to the determination of the portrait image data associated with the first portrait images; and - generating the passport image data using portrait image data which are associated with one of the second portrait images if the portrait image data satisfy at least the necessary subset of the first test criteria and at least the necessary subset of the second test criteria.

8. The method according to at least one of the preceding claims, characterized in that the first test criteria comprise one or more of the following test criteria: illumination of the portrait image, background of the portrait image, image contrast, head position, eyes and viewing direction, head covering and fit of a pair of glasses.

9. The method according to at least one of the preceding claims, characterized in that an unsuitable portrait image is determined from the first portrait images for which the associated portrait image data do not satisfy the necessary subset of the first test criteria, wherein at least one of the following steps is provided thereon: - generating control data in response to the detection of an error, with the result that one of the first test criteria is not satisfied in the case of the unsuitable portrait image, wherein - the control data are configured to control an output via an output device (9) to the person (4), and - with the output a user instruction for correcting the error is output to the person (4); and - generating further control data in response to the detection of a further error, with the result that a further one of the first test criteria is not satisfied in the case of the unsuitable portrait image, wherein the further control data are configured to change an operating parameter of the video image recording device (2) and / or of a lighting device assigned to the video image recording device (2) for recording the sequence of portrait images.

10. The method according to at least one of the preceding claims, characterized in that by means of the second test criteria it is tested whether the portrait image data represent a digital biometric passport image which complies with the ICAO standard for passport images for machine-readable security documents.

11. The method according to at least one of the preceding claims, characterized in that the sequence of portrait images are recorded during the video image recording at a frame repetition rate between approximately 10 images per second and approximately 30 images per second.

12. A method for personalizing a security document, comprising: - determining passport image data representing a digital biometric passport image according to a method according to at least one of the preceding claims; - providing the passport image data in a personalization device (7); - providing a security document (1); and - personalizing the security document (1), wherein the passport image data are processed in the personalization device (7) and a representation of the digital biometric passport image is applied to the security document (1).

13. The method according to claim 12, wherein a biometric passport image is printed on the security document (1) when applying the representation of the digital biometric passport image and / or the passport image data are stored in an electronic memory element (8) of the security document (1).

14. A device for determining passport image data representing a digital biometric passport image for a security document (1), comprising a passport image capturing device (3) configured to: - record a sequence of portrait images for a person (4) by means of video image recording at a frame repetition rate and a recording resolution for the portrait images by means of a video image recording device (2); - store respective portrait image data with the recording resolution and portrait image data with a reduced resolution compared to the recording resolution for the portrait images from the video image recording; and - determine passport image data representing a digital biometric passport image of the person (4) from the portrait images of the video image recording, comprising: - selecting first portrait images from the sequence of portrait images; - determining whether the portrait image data, which are respectively associated with the first portrait images, satisfy first test criteria with respect to a suitability for a digital biometric passport image of the person (4), wherein the test for the portrait image data is performed with the reduced resolution; - selecting one of the first portrait images for which the associated portrait image data satisfy at least a necessary subset of the first test criteria; - determining whether the portrait image data, which are associated with the one of the first portrait images, satisfy second test criteria with respect to the suitability for the digital biometric passport image of the person (4), wherein the second test criteria are different from the first test criteria and the test for the portrait image data is performed with the reduced resolution; and - generating the passport image data using the portrait image data associated with the one of the first portrait images with the recording resolution if the portrait image data with the reduced resolution, which are associated with the one of the first portrait images, satisfy at least a necessary subset of the second test criteria.