DE102015107474A1 - Method for determining an individual sharpness of an image of an iris and method for person examination - Google Patents

Abstract

The application describes a method for determining an individual sharpness of an image of an iris, comprising: taking an image of an eye; and storing the image in an image memory; having in the image memory: finding a pupil of the eye; Determining at least two scan areas, each located partially in the pupil and partially external to the pupil, each scan area being contiguous in its own right; Determining a reference sample area having a maximum reference contrast which is greater than the contrast of each other sample area; Storing the location of the reference scan area and the maximum reference contrast; Taking a further picture of the eye while varying a focus; Storing the further picture in the picture memory; Determining the current contrast in the reference scan area; Comparing whether the current contrast is greater than a previous contrast; and performing the steps until the current contrast is the highest achievable. Furthermore, the application relates to a method for checking persons and to a method for determining a digitized image recording of an iris in a data processing device.

Description

The invention relates to technologies in the context of determining an individual sharpness of an image of an iris, as well as the use.

background

It is known to make a determination of the person's iris in the context of biometrics, in particular for person identification. Iris determination can also be used in animals. Digitized images of the iris are analyzed by means of electronic data processing in order to carry out the determination. For the digital image analysis, the aim is to have as good as possible processable image recordings, wherein the image quality is influenced in particular by the sharpness of the image recording, which depends on the focus setting of the image recording device. The sharpness of the image is a measure of the distinctiveness of details in the image capture. There is therefore an attempt to obtain the sharpest possible image recordings of the eye for the iris determination, which required a necessary focus adjustment of the image recording device.

In the document EP 1 171 996 B1 a method for determining focus in an image recording device is disclosed. On the digitized images, which in particular can also show an iris image, a convolution with a special convolution kernel is applied to the pixels, which corresponds to the application of a high-pass filter. In this way, the proportion of high frequencies of the image recording compared to lower frequencies should be emphasized, since the high frequencies are particularly suitable to deduce from this a measure of the sharpness of the recorded images and thus the focus setting of the image pickup device.

Summary

The object of the invention is to provide a method for determining a digitized image recording of an iris in a data processing device and uses for this, in which iris images can be evaluated in a simple and efficient manner with the least possible expenditure of time. According to another aspect, the person examination should be made more efficient.

As a solution, a method for determining an individual sharpness of an image of an iris according to independent claim 1 is provided. Furthermore, a method for personal verification is provided according to claim. Furthermore, a method for determining a digitized image recording of an iris in a data processing device according to the independent claim 3 is provided. Claims 9 and 10 relate to uses of the method. Embodiments are the subject of dependent claims.

• a) Aufnehmen eines Bildes eines Auges; und
• b) Speichern des Bildes in einem Bildspeicher; im Bildspeicher aufweisend:
• c) Auffinden einer Pupille des Auges;
• d) Bestimmen von wenigstens zwei Abtastbereichen, die jeweils teilweise in der Pupille und teilweise außerhalb der Pupille angeordnet sind, wobei jeder Abtastbereich für sich genommen zusammenhängend ist;
• e) Ermitteln eines Referenz-Abtastbereiches, der einen maximalen Referenz-Kontrast aufweist, welcher größer ist als der Kontrast jedes anderen Abtastbereiches;
• f) Speichern der Lage des Referenz-Abtastbereiches und des maximalen Referenz-Kontrastes;
• g) Aufnehmen eines weiteren Bildes des Auges unter Variation einer Scharfstellung;
• h) Speichern des weiteren Bildes im Bildspeicher;
• i) Ermitteln des aktuellen Kontrastes im Referenz-Abtastbereich;
• j) Vergleichen, ob der aktuelle Kontrast größer ist als ein vorangegangener Kontrast; und
• k) Durchführen der Schritte g) bis i) solange, bis der aktuelle Kontrast der größtmöglich erzielbare ist.

In one aspect, a method is provided for determining an individual sharpness of an image of an iris. The method comprises the following steps:

• a) taking a picture of an eye; and
• b) storing the image in a frame buffer; in image memory having:
• c) finding a pupil of the eye;
• d) determining at least two scan areas, each located partially in the pupil and partially outside the pupil, each scan area being contiguous in its own right;
• e) determining a reference sample area having a maximum reference contrast which is greater than the contrast of each other sample area;
• f) storing the location of the reference scan area and the maximum reference contrast;
• g) taking a further image of the eye while varying a focus;
• h) storing the further image in the image memory;
• i) determining the current contrast in the reference scan area;
• j) comparing whether the current contrast is greater than a previous contrast; and
• k) performing steps g) to i) until the current contrast is the highest achievable.

• A) Erfassen eines Individualbildes einer Individualiris, insbesondere mittels eines Verfahrens zum Bestimmen einer individuellen Schärfe eines Bildes, sowie wenigstens eines weiteren biometrischen Individualmerkmals einer Person und Bilden eines kombinierten Biometriedatensatzes aus dem Individualbild und dem weiteren biometrischen Individualmerkmal;
• B) Erstellen einer Datenbank mit einer Mehrzahl von kombinierten Biometriedatensätzen;
• C) Klassifizieren der kombinierten Biometriedatensätze in der Datenbank, um so klassifizierte kombinierte Biometriedatensätze zu erhalten, jeweils bestehend aus einem klassifizierten Bild und einem klassifizierten weiteren biometrischen Merkmal; und
• D) bei Erfassen eines Messbildes einer Iris einer Person mittels des Verfahrens zum Bestimmen einer individuellen Schärfe eines Bildes einer Iris: E) Vergleichen des Messbildes mit den Bildern der klassifizierten kombinierten Biometriedatensätze und, darauf beruhend, Auffinden eines Best-Match-Biometriedatensatzes; F) Ermitteln des klassifizierten weiteren biometrischen Merkmals des Best-Match-Biometriedatensatzes; G) Vergleichen des Weiteren biometrischen Merkmals der Person mit dem klassifizierten weiteren biometrischen Merkmal des Best-Match-Biometriedatensatzes; und H) Ausgabe eines Warnhinweises, wenn das weitere biometrische Merkmal der Person von dem klassifizierten weiteren biometrischen Merkmal des Best-Match-Biometriedatensatzes in einem vorbestimmten Maße abweicht.

In another aspect, a method of personal verification is proposed. The method comprises the following steps:

• A) acquiring an individual image of an individual iris, in particular by means of a method for determining an individual sharpness of an image, and at least one further biometric individual feature of a person and forming a combined biometric data set from the individual image and the further biometric individual feature;
• B) creating a database with a plurality of combined biometric datasets;
• C) classifying the combined biometric data sets in the database so as to obtain classified combined biometric data sets each consisting of a classified image and a classified further biometric feature; and
• D) when acquiring a measurement image of an iris of a person by means of the method for determining an individual sharpness of an image of an iris: E) comparing the measurement image with the images of the classified combined Biometric datasets and, based thereon, finding a best match biometric dataset; F) determining the classified further biometric feature of the best match biometric dataset; G) comparing the further biometric feature of the person with the classified further biometric feature of the best match biometric data set; and H) issuing a warning if the further biometric characteristic of the subject deviates from the classified further biometric feature of the best match biometric dataset by a predetermined amount.

In the method for determining an individual sharpness of an image of an iris and / or in the method for person verification, alternatively or additionally to the contrast, a contrast increase (image contrast increase) can be determined for the scanning regions and used as a measure of the image sharpness.

In another aspect, there is provided a method of determining a digitized image capture of an iris in a data processing device. The data processing device is set up by means of a software application for digital image processing. The method provides an iris image in digitized form. The iris image is an image of an eye showing at least the area of the iris and the pupil of the eye. An image portion or section of the iris image (scan area) is selected, which shows a transition section with a pupil area and an iris area adjacent thereto. An image contrast increase is determined for a transition between the pupil area and the adjacent iris area in the transition section. From the image contrast increase, or briefly contrast increase, a sharpness measure for the iris image is determined.

From an analysis of the contrast properties of the iris image in the area of the transition between a pupil area and an adjacent iris area, a sharpening dimension of the iris image is thus determined according to the various aspects, which indicates a measure of the focus setting of the image recording device used for image recording.

The image contrast increase can be a local contrast increase, which, when applying contrast values above a local dimension for the pixels in the minimum case, characterizes the increase in the contrast over a few pixels, for example at least three pixels. For example, the values representing a measure of the brightness of the pixels may be plotted as y-values, where x-values each represent a pixel or channel of the image capture device, for example, equidistant-spaced points. When comparing the thus determined gradient / increase of the contrast for different images of the same transition section or scanning region, the curves to be compared can be steeper or flatter, which indicates different contrast increases in the examined region.

Also, a local group of pixels may be included in determining the local contrast increase or local contrast, wherein one or more pixels are to be associated with the pupil region and one or more pixels are adjacent to the adjacent iris region.

The pixels can lie on a straight line, which intersects the border area between the pupil area and the adjacent iris area.

In an embodiment, it may be provided that the sharpness dimension is determined as being proportional to the ascertained image contrast increase between pupil area and adjacent iris area.

The method can be used in connection with a biometric determination of an iris or in an iris image recording device.

When determining the sharpness dimension for digital pixels of the transition, FFT values (FFT - Fast Fourier Transformation) can be determined or determined between the pupil region and the adjacent iris region by means of fast Fourier transformation.

When determining the amount of sharpness, the FFT values of an algebraic operation can be summarized accordingly. The FFT values along a transition between the pupil area and the iris area may be added in one embodiment. The contrast increase in the transition region may correspond to the difference of the FFT values of the pixels on both sides of the transition between the pupil region and the iris region. Additionally or alternatively, the slope of the curve of the FFT values in the transition region can be determined. The measure of the sharpness of the iris image may be proportional to the difference and / or increase. Proportionality with respect to the sum of the FFT values may also be provided for the sharpness measure.

In determining the image contrast increase, an edge may be determined in the course of pixel values associated with the pixels.

• – ein weiterer Bildabschnitt des Irisbildes ausgewählt wird, welcher entlang des Umfangs der Pupille einen anderen Übergangsabschnitt mit einem Pupillenbereich und einem hieran grenzenden Irisbereich zeigt,
• – ein weiterer Bildkontrastanstieg für den weiteren Übergang zwischen dem Pupillenbereich und dem hieran grenzenden Irisbereich in dem Übergangsabschnitt bestimmt wird und
• – der Bildkontrastanstieg und / oder weiterer Bildkontrastanstieg ausgewählt werden, um hieraus ein jeweiliges Schärfemaß für das Irisbild zu bestimmen.

It can also be provided that

• A further image section of the iris image is selected which shows, along the circumference of the pupil, another transition section with a pupil region and an iris region adjacent thereto,
• A further image contrast increase is determined for the further transition between the pupil region and the adjacent iris region in the transition section, and
• The image contrast increase and / or further image contrast increase are selected in order to determine therefrom a respective focal length for the iris image.

In this way, the contrast increase can be determined for different image sections which are arranged along the circumference of the pupil. In this case, the determination of the image contrast increase may be provided for adjacent and / or spaced transition sections along the circumference of the pupil. Starting from the respectively determined image contrast increase then a sharpness measure can be derived. In this way it can be provided in one embodiment to determine a transition section along the circumference of the pupil, which is then used for further analysis, in particular the determination of a sharpness measure for the iris image. In an embodiment it can be provided that, starting from the determination of the transition section between a pupil area and an adjacent iris area for which the greatest increase in contrast has been determined, a more extensive image analysis is carried out.

The contrast determination for several transition sections along the circumference of the pupil can be performed for one or more iris images, all of which show the same iris. Thereafter, it may be provided to select one of the transition sections for the sharpness measurement. The focus can in turn be determined for one and the same transition section along the circumference of the pupil for several iris images, so that ultimately an iris image with the best or highest sharpening measure can be determined. This iris image can then be supplied for example to further image processing or processing, for example for an iris determination in the context of biometry.

• – ein weiteres Irisbild in digitalisierter Form bereitgestellt wird, welches dieselbe Iris wie das Irisbild zeigt,
• – ein Bildabschnitt des weiteren Irisbildes ausgewählt wird, welcher entlang des Umfangs der Pupille den gleichen Übergangsabschnitt mit dem Pupillenbereich und dem hieran grenzenden Irisbereich zeigt,
• – ein Bildkontrastanstieg für den Übergang zwischen dem Pupillenbereich und dem hieran grenzenden Irisbereich in dem Übergangsabschnitt des weiteren Irisbildes bestimmt wird und
• – ein Schärfemaß für das andere Irisbild aus dem Bildkontrastanstieg bestimmt wird.

In one embodiment, it may be provided that

• A further iris image is provided in digitized form, which shows the same iris as the iris image,
• An image section of the further iris image is selected, which shows the same transition section with the pupil region and the adjacent iris region along the circumference of the pupil,
• An image contrast increase for the transition between the pupil area and the adjacent iris area in the transition section of the further iris image is determined, and
• - A sharpness measure for the other iris image is determined from the image contrast increase.

For each of the plurality of iris images, a specific measure of the image sharpness can be compared in order to select an iris image suitable for further image processing or processing from the set of iris images examined.

The illustrated embodiments may be provided individually or in any combination in conjunction with the alternative method embodiments.

Description of exemplary embodiments

In the following, further embodiments will be explained with reference to figures of a drawing. Hereby show:

1 3 is a schematic representation of an arrangement for recording and evaluating digital image recordings showing at least the area with the iris and the pupil from an eye to be determined;

2 a schematic representation of an iris with pupil,

3 a flow chart for a method for determining iris images in digital form,

4 a graphical representation of a normalized intensity for pixels along an image pick-up line,

5 a graphical representation of the image intensity over a series of pixels in a transition section between a pupil area and an iris area for iris images with different image sharpness,

6 a graphic representation of FFT values for the curves 5 and

7 a graphical representation of accumulated FFT values for iris images with different sharpness.

1 shows a schematic representation of an arrangement with an image pickup device 1 , which is designed as a digital camera, for example. The image capture device 1 is opposite to an eye 2 arranged by means of the Image recording device 1 Digital images should be taken that cover at least the area of the iris with the pupil of the eye 2 demonstrate. The image capture device 1 is functional with a data processing device 3 coupled with the aid of a software application installed thereon for processing and processing of the image recording device 1 recorded digital images is set up.

It can be provided that in the data processing device 3 in response to a performed image analysis control signals are generated, which control the image pickup device 2 serve, for example for controlling a triggering time for the image recording and / or positioning of the image pickup device 1 in relation to the eye 2 , what in 1 is shown schematically by means of an arrow A. Alternatively or additionally, it may be provided that audible and / or visual information is output to the user so that the latter has his eye 2 in relation to the image recording device 1 relocated. This may also be dependent on image processing in the data processing device 3 to be controlled.

Alternatively or additionally, optical components, for example lenses and / or a lens, in the image recording device can be used to adjust the focus for the image recordings 2 be set in response to control signals for image acquisition, the control signals being the result of an image analysis in the data processing device 3 could be. Thus, by means of the data processing device 3 determine a measure of the sharpness of the recorded images, then from the comparison of the sharpness measure for multiple images, a focus control signal to the image pickup device 2 to give and / or select one of the examined images for further image analysis, for example for a biometric analysis for person recognition or verification. Data processing device 3 and image capture device 2 can also be integrated in a common housing.

The arrangement shown can be used, for example, for person identification in the context of a biometric method.

2 shows a schematic representation of a portion of an iris image with pupil 20 and iris 21 , In the image analysis, one or more local transitions 22 between the pupil 20 and iris 21 be evaluated to a respective local contrast increase between the image area of the pupil 20 and the adjacent image area for the iris 21 to determine. A circumferential border area 23 between the pupil 20 and iris 21 can be partially or completely captured in the image analysis by the local transition 22 along the border area 23 is moved.

With reference to 3 In the following, a method for determining one or more iris images in digitized form is explained. In one step 30 is using the image capture device 2 taken an iris image and for an image analysis in the data processing device 3 provided. With the help of on the data processing device 3 for the image analysis implemented software application is in step 31 an image section (scanning region) is selected which has a transition or transition section between a pupil region 20 and an iris area 21 (see. 2 ).

In 4 is an example of a normalized measured intensity for pixels of the iris image along a line B in the image display 4 (see also 2 ). The intensity decreases in a middle range 40 which of the pupil 20 equivalent. In the area 41 decreases the intensity in the transition to the area of the iris 21 steeply too.

5 shows this transition in detail. Curve 50 corresponds to the course of the measured curve in 4 , Furthermore, a curve 51 shown, in which the steepness of the curve in the increase is significantly lower, which corresponds to a different contrast increase. The curve 51 shows the course for the same local transition between pupil 20 and iris 21 in a so-called Blurr image, which for comparison purposes from the measured values (see. 4 ) was derived. The lower image sharpness in the area between the pupil area 20 and iris area 21 leads to the changed curve increase, whereby the actual contrast (brightness difference) is the same here.

In step 32 Then, a fast Fourier transform is applied to the digital images to produce FFT values for the in 5 To determine curves shown. The result of this operation is in 6 shown where the bend 60 and 61 the FFT values for the curves 50 and 51 demonstrate.

In the image analysis in the data processing device 3 Then, based on the determined contrast increase, a measure of the sharpness of the analyzed iris images is determined (step 33 ). For example, in this case, the steepness in the transition region between the pupil 20 and iris area 21 be used.

Alternatively or additionally, the FFT values for the curves in 6 be summed up. The result of this operation shows 7 in the form of values 70 and 71 for the two curves 60 and 61 , In 7 are two more results 72 , ..., 74 entered. For these, the Blurr radius extended, whereby a further decreasing image sharpness was simulated.

The method described above can be used to determine in a sequence of iris images, which were taken for one and the same iris, the image acquisition with the best image sharpness, resulting in a best focus adjustment of the image recording device 1 in relation to the eye 2 equivalent. The iris image selected in this case can then be used for further image analysis, for example for iris biometry, which, for example, also in the data processing device 3 can be executed.

The described method, with all the steps or parts thereof, can also be used for the process of image acquisition by means of the image recording device 2 to control, for example, that in an initial measurement phase, multiple iris images for different distances between the eye 2 and the image pickup device 1 be recorded in order to determine in this way a preferred distance between the measuring device and the measuring object (eye), in order to make the actual iris image recording. The iris image recorded in this case can then be analyzed, for example for the purpose of an iris biometry. Thus, an improved method for personal identification by means of iris biometry is provided in various ways.

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

QUOTES INCLUDE IN THE DESCRIPTION

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

Cited patent literature

• EP 1171996 B1 [0003]

Claims (10)

A method of determining an individual sharpness of an image of an iris, comprising: a) taking a picture of an eye; and b) storing the image in a frame buffer; in image memory having: c) finding a pupil of the eye; d) determining at least two scan areas, each located partially in the pupil and partially outside the pupil, each scan area being contiguous in its own right; e) determining a reference sample area having a maximum reference contrast which is greater than the contrast of each other sample area; f) storing the location of the reference scan area and the maximum reference contrast; g) taking a further image of the eye while varying a focus; h) storing the further image in the image memory; i) determining the current contrast in the reference scan area; j) comparing whether the current contrast is greater than a previous contrast; and k) performing steps g) to i) until the current contrast is the highest achievable. Method for checking persons, comprising: A) detecting an individual image of an individual iris with the method according to claim 1 and at least one further biometric individual feature of a person and forming a combined biometric data set from the individual image and the further biometric individual feature; B) creating a database with a plurality of combined biometric datasets; C) classifying the combined biometric data sets in the database so as to obtain classified combined biometric data sets each consisting of a classified image and a classified further biometric feature; and D) when acquiring a measurement image of an iris of a person with the method according to claim 1: E) comparing the measurement image with the images of the classified combined biometric data sets and, based thereon, finding a best match biometric data set; F) determining the classified further biometric feature of the best match biometric dataset; G) comparing the further biometric feature of the person with the classified further biometric feature of the best match biometric data set; and H) issuing a warning if the person's further biometric feature deviates from the classified further biometric feature of the best-match biometric dataset by a predetermined amount. A method for determining a digitized image capture of an iris in a data processing device that is implemented by means of a software application for digital image processing, the method comprising the following steps: Providing an iris image in digitized form, Selecting an image section of the iris image which shows a transition section with a pupil region and an iris region adjacent thereto, Determining an image contrast increase for a transition between the pupil area and the adjacent iris area in the transition section and - Determining a sharpness measure for the iris image from the image contrast increase. Method according to Claim 3, characterized in that FFT values are determined by means of fast Fourier transformation when determining the sharpness dimension for digital pixels of the transition between the pupil region and the adjacent iris region. A method according to claim 4, characterized in that the FFT values of an algebraic operation are combined accordingly when determining the sharpness measure. Method according to at least one of claims 3 to 5, characterized in that, when determining the image contrast increase, an edge is determined in the course of pixel values associated with the pixels. Method according to at least one of claims 3 to 6, characterized in that - a further image section of the iris image is selected, which along the circumference of the pupil shows another transition section with a pupil region and an iris region adjacent thereto, - a further image contrast increase for the further transition is determined between the pupil area and the adjacent iris area in the transition section and - the image contrast increase and / or further image contrast increase are selected in order to determine therefrom a respective degree of sharpening for the iris image. Method according to at least one of claims 3 to 7, characterized in that - a further iris image is provided in digitized form, which shows the same iris as the iris image, - an image section of the further iris image is selected which along the circumference of the pupil the same transition section showing the pupil area and the adjacent iris area, An image contrast increase for the transition between the pupil area and the adjacent iris area in the transition section of the further iris image is determined and a degree of sharpening for the other iris image is determined from the image contrast increase. Use of a method according to at least one of claims 3 to 8 in a biometric determination of an iris. Use of a method according to at least one of claims 3 to 8 in an iris image recording device.

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