WO2011116761A1

WO2011116761A1 - Method for detecting biometric features

Info

Publication number: WO2011116761A1
Application number: PCT/DE2011/075007
Authority: WO
Inventors: Markus Dilger; Frank Neudel; Jürg ABDERHALDEN
Original assignee: Tst Biometrics Holding Ag
Priority date: 2010-03-24
Filing date: 2011-01-21
Publication date: 2011-09-29
Also published as: DE102010016109A1

Abstract

The invention relates to a method for detecting biometric features of a body part (4) to be examined, in particular of a finger having finger lines, wherein the body part (4) is illuminated with a light of a first wavelength and/or polarization and with a light (11) of a second wavelength and/or polarization different from the first wavelength and/or polarization, said light of a second wavelength and/or polarization having a pattern, and wherein the light of the first wavelength and/or polarization reflected by the body part (4) is detected in order to determine biometric features as a biometric image (15) of the body part (4) based on the detected light of the first wavelength and/or polarization, and wherein at the same time the light of the second wavelength and/or polarization reflected by the body part (4) is detected in order to determine a three-dimensional shape of the body part (4) as a geometric image (14) of the body part (4) based on the detected light of the second wavelength and/or polarization by evaluating the distortion of the pattern, and wherein the biometric image (15) is mapped to the geometric image (14) in order to obtain a three-dimensional distribution of the biometric features on the body part (4).

Description

Method for detecting biometric features

The invention is formed by a method for detecting biometric features in a body part to be examined, in particular a finger with finger lines, wherein the body part with a light of a first wavelength and / or polarization and with a light of a second wavelength deviating from the first wavelength and / or polarization having a pattern is illuminated, and wherein the light of the first wavelength and / or polarization reflected by the body part is detected to be detected by the detected light of the first wavelength and / or

Polarization biometric features as a Biometriebild of the body part to determine, and at the same time the light reflected by the body part of the second wavelength and / or polarization is detected, based on the detected light of the second wavelength and / or polarization with an evaluation of the distortion of the pattern to determine a three-dimensional shape of the body part as a geometry image of the body part, and in which the biomass image is imaged onto the geometry image to a

to obtain three-dimensional distribution of biometric features on the body part. Three-dimensional recordings of finger surfaces allow for higher biometric recognition performance over fingerprint scanners, because the amount of pressure, unknown over time, on the surface of a two-dimensional scanner results in finger deformation and reduces the recognition performance of the system or requires higher tolerances in the evaluation software , which is at the expense of the power of separation between the fingers of different persons. For this reason, various approaches to the measurement of fingertips have been studied. In US 5963664 and DE

10153808 describes methods in which by

Mirror arrangements are recorded multiple views of fingertips. DE 10315923 describes a method in which several views are taken by sequential illumination from different directions. These views are taken either with multi-camera systems as described in US 7606395 or by sub-images in a camera. A disadvantage of the conventional methods is that the use of mirrors requires either extremely precise positioning of the mirrors, which leads to increased manufacturing costs, or a software offset of the mirror offset. This overlay is in low-detail fields of the

Views elaborate and prone to failure. The use of multiple camera units leads to an additional cost of electronic and optical components, thereby increasing the manufacturing cost of the

Increase overall system. In principle, camera systems which use a transit time method to determine distances (3D-TOF

Camera systems) are used to determine the geometry of the body part. US 20020097896 discloses a structured illumination as a dot matrix at a triangulation angle to the camera, by means of which displacement a statement about the topology of the body part can be made. An extension of this functionality is achieved through the use of patterns of different frequencies, interfering with structures of equal frequency on the

measuring surface of the body part can be avoided. A disadvantage of the sequential image recording, however, is that the user must hold the finger during recording stationary or a software-side correction of the position is necessary.

The invention is therefore based on the object to provide a method with which biometric information can be better captured and processed. This object is achieved in a method for detecting biometric

Characteristics in a body part to be examined, in particular in a finger with finger lines solved by the body part with a light of a first wavelength and / or polarization and with a light of a second wavelength deviating from the second wavelength and / or

Polarization having a pattern is illuminated, and by detecting the light of the first wavelength and / or polarization reflected by the body part to determine biometric characteristics as a bio-mode image of the body part from the detected light of the first wavelength and / or polarization; and simultaneously detecting the second wavelength and / or polarization light reflected from the body part to determine from the detected second wavelength light and / or polarization

Polarization with an evaluation of the distortion of the pattern, a three-dimensional shape of the body part as a Geometriebild of the

Determine body part, and by the biometriebildbild on the

Geometry image is mapped to obtain a three-dimensional distribution of biometric features on the body part. The

different optical properties of the striking on the finger Lights are either through the optical filters or through the

generated different optical properties of the light sources. The filters are preferably color filters which transmit only light of different wavelengths or linear polarizers which are arranged perpendicular to one another. The separation of the two information takes place in the recording unit by the filters associated optical elements

(Color camera or polarizer elements in front of the pixels). The advantage of this procedure is that by mapping the biomimetic image to the geometry image, the biometric features are better determined three-dimensionally. In addition, the simultaneous detection of a spatial displacement of the images to each other is avoided.

In this method, the light of the first wavelength and / or polarization and the light of the second wavelength and / or polarization are preferably detected with a color camera or a polarization-selective camera whose color channels separate the first wavelength and the second wavelength, whereby the device for carrying out the

Procedure can be made simpler.

It has proved to be advantageous in the method when sinusoidal structures have been impressed on the light of the second wavelength and / or polarization. By means of the illumination with the sinusoidal structure, an improved determination of the geometry is possible in comparison to a fringe pattern. Preferably, the light of the second

Wavelength and / or polarization are measured using fast Fourier transforms and / or phase locked loops, since sinusoidal patterns can be measured with a sufficiently high number of periods via fast Fourier transforms or phase locked loops, with a low resolution in the maxima and minima of the sine can be compensated by interpolation. Important for the functioning of the based on the structured illumination measuring Geometriebildes is that the topological properties of the body part to be examined in the frequency can be clearly separated. The frequency of

Lighting must therefore differ from the frequency of the finger lines, which also generates an approximated sinusoidal information in the frequency domain.

Furthermore, the first wavelength and / or the second wavelength may be in the range of 400 nm to 580 nm. Preferably, in the method, the light of the second wavelength is under a

Triangulation angle is projected onto an entire surface of the body part to be examined.

Furthermore, in the method, a distance-dependent

Magnification can be compensated on an image surface of the body part to be examined, whereby a telecentric recording can be obtained.

Particularly preferred is based on the detected light of the first

Wavelength and / or polarization and the detected light of the second wavelength and / or polarization calculated from the circumference unrolled image of the body part.

In this method, it has proved to be advantageous if an image of the deformed body part is calculated with definable parameters, in particular contact pressure and / or elasticity of the body part and / or diameter of the body part. It has proven to be favorable if the predetermined parameters based on the Geometriebildes be determined. Preferably, the method compares the circumferentially unrolled image of the body part or the image of the deformed body part to two-dimensional impressions of the body part stored in a database, thereby enabling matching with biometric features data sets transmitted by contact based scanners

Ink prints or forensic images have been obtained.

Alternatively and / or additionally, in the method, the thus determined three-dimensional distribution of the biometric features on the body part can be compared with data sets of biometric features stored in a database which have been detected according to the invention.

In the following the invention is illustrated in the drawing

Embodiments explained in more detail; show it:

Fig. 1 is a schematic representation of a first device, the

2 is a schematic representation of a second device which is suitable for carrying out the method according to the invention,

Fig. 3 and a diagram for the method of detecting biometric

Features and

Fig. 4 is a schematic representation of the distance determination

1 and 2 show schematic representations of a first device and a second device, which are used to carry out the

inventive method are suitable. A finger 4 to be examined is illuminated in a region 6 to be detected biometrically via a first light source 3 with a light of a first wavelength. The Light source 3 may have one light-emitting diode or a plurality of light-emitting diodes of the same color. The reflected light from the region 6 is detected by a camera 1, wherein z. B. a lens 2 is arranged in front of the camera 1. As shown in FIG. 1, the finger 4 can also rest on a support 5. Alternatively, as shown in FIG. 2, the finger 5 can be freely held over the camera 1 to avoid deformations of the finger 4. The area to be detected biometrically 6 will continue under a

Triangulation angle 7 is illuminated via a second light source 8 with a light of a second wavelength, which differs from the first wavelength. Via an absorption pattern 9, a pattern is impressed on the light of the second wavelength, wherein in the beam path a

Projection optics 10 may be arranged. For better separation of the color channels, an optical or a plurality of optical filters 16 may be arranged in front of the first light source 3 and / or the second light source 8. It should be noted that different polarizations and a polarization-sensitive camera can be used instead of different wavelengths and a color-selective camera.

Fig. 3 shows a scheme for the inventive method for

Acquisition of biometric features. The finger 4 to be examined is illuminated with the light 11 of a second wavelength, which may have been impressed on a sinusoidal pattern. An ensuing one

Phase shift 12 and modeling the frequency of the pattern gives depth information 13 for a topographic survey of the finger 4 and its position in space so that a geometry image 14 can be determined while determining a biomimetic image 15 with the light of the first wavelength. The absolute determination of the position of the biometric object in space can, as in FIG. 4, be seen by objects visible in the image at the edge of the image with known depth information and there observed position of the projection pattern 14 on the object are determined (case 13A) or with a defined pattern artifact and their detection and measurement of the shift in the image relative to a reference position of the artifact with a flat object in the zero plane in the image (3B). In the case 13A, in particular, the underside of the support 5 is suitable, whereby it must be ensured that the

Projection pattern 14 can be tracked steadily from the edge to the object 4 to be measured. With the imaging of the biomimetic image 15 on the geometry image 14, a data set with the biometric information on the surface of the finger 4 can be determined three-dimensionally precisely. In addition to translations and / or rotations of this three-dimensional

Dataset can be generated more images to biometric evaluations.

1) For example, an optically corrected image can be generated, which compensates the distance-dependent magnification on the body part to be measured, whereby a telecentric image 17 is obtained.

2) Furthermore, a circumferential unrolled image 18 can be generated, which compensates for the shortened by the plan view representation of the planes whose surface normal is not parallel to the optical axis. This eliminates biometric comparisons between one and the same body part, the rotation-related differences.

3) In addition, due to a simulated deformation of the

examining body part are generated an image, the z. B. the pressing on a flat surface with a predetermined contact pressure, so that can be used for the comparison of data sets of contact-based scanners, ink prints or forensic Pictures have been obtained. The parameters for the simulated

Deformations can both empirical, such. B. from the elasticity of the finger, or from the three-dimensional record such. B. from the radius of the finger can be obtained. For those out of the simulation

resulting image can be different contact pressures or

Geometries of the surfaces are used, so that in each case a two-dimensional image of an impression of uneven objects can be generated, as is desirable for forensics.

4) In addition, a combination of the imaging methods 2) and 3) can also be performed so that data records corresponding to a rolled forensic finger with deformations generated by contact pressure can be obtained.

With regard to the determination of the distances of the body part (4) from the camera, either the defect in the pattern can be defined and subsequently detected in the image, or an object of known distance also illuminated with the pattern and imaged in the image, while the body part (4) Object is present.

The method of detecting a biometric feature is not limited to the detection of finger lines, but may be applied to other parts of the body to be examined (such as the iris).

LIST OF REFERENCE NUMBERS

1 digital camera

2 lens

3 first light source

4 fingers

5 edition

6 biometrically detectable area

7 triangulation angle

8 second light source

9 absorption patterns

10 projection optics

1 1 light with sinusoidal pattern

12 phase shift

13 depth information

14 geometry image

15 Biomedical image

16 optical filters

17 telecentric picture

18 figure unfolded from the circumference

Claims

claims:

Method for detecting biometric features in a zu

examining body part (4), in particular a finger with finger lines, in which:

the body part (4) is illuminated with a light of a first wavelength and / or polarization and with a light (1 1) of a second wavelength deviating from the first wavelength and / or polarization having a pattern,

the light of the first wavelength and / or polarization reflected by the body part (4) is detected in order to determine biometric features as a biomimetic image (15) of the body part (4) on the basis of the detected light of the first wavelength and / or polarization,

- At the same time from the body part (4) reflected light of the second wavelength and / or polarization is detected to a basis of the detected light of the second wavelength and / or polarization with an evaluation of the distortion of the pattern, a three-dimensional shape of the body part (4) as a Determine geometry image (14) of the body part (4), and

- The Biometriebild (15) is imaged on the Geometriebild (14) to obtain a three-dimensional distribution of the biometric features on the body part (4).

A method according to claim 1, characterized in that the light of the first wavelength and / or polarization and the light (1 1) of the second wavelength and / or polarization with a color camera (1) or a polarization-selective camera are detected whose color channels the first wavelength and separate the second wavelength.

3. The method according to claim 1 or 2, characterized in that the

Light (1 1) of the second wavelength sinusoidal structures have been impressed.

4. The method according to any one of claims 1 to 3, characterized in that the first wavelength and / or the second wavelength are in the range of 400 nm to 580 nm.

5. The method according to any one of claims 1 to 4, characterized in that the light of the second wavelength and / or polarization is measured with fast Fourier transforms and / or phase locked loops.

6. The method according to any one of claims 1 to 5, characterized in that the light of the second wavelength and / or polarization at a triangulation angle (7) on an entire surface of the

Part of the body (4) is projected.

7. The method according to any one of claims 1 to 6, characterized in that a distance-dependent magnification on an image surface of the body part (4) is compensated.

8. The method according to any one of claims 1 to 7, characterized in that on the basis of the detected light of the first wavelength and / or polarization and the detected light of the second wavelength and / or polarization of an unrolled image (18) of the body part (4) is calculated.

9. The method according to any one of claims 1 to 8, characterized in that with definable parameters, in particular contact pressure and / or elasticity of the body part (4) and / or diameter of the body part (4), an image of the deformed body part is calculated.

10. The method according to claim 9, characterized in that the

predetermined parameters are determined based on the Geometriebildes (14).

1 1. Method according to one of claims 8 to 10, characterized

characterized in that the image (18) of the

Body part (4) and / or the image of the deformed body part (4) are compared with stored in a database two-dimensional impressions of the body part.

12. The method according to any one of claims 1 to 1 1, characterized

characterized in that the determined three-dimensional distribution of the biometric features on the body part (4) is compared with data sets of biometric features stored in a database.

13. The method according to any one of claims 1 to 12, characterized

characterized in that for determining the absolute distances of the body part (4) from the camera in the pattern generates a defined defect and this is detected in the image.

14. The method according to any one of claims 1 to 13, characterized

characterized in that for determining the absolute distances of the Part of the body (4) is illuminated by the camera an image visible object visible distances with the pattern, while the body part (4) abuts the object.