KR20080100010A - Apparatus for distinguishing forged fingerprint and method therof - Google Patents

Abstract

An apparatus for determining a forged fingerprint and a method therefor are provided to perform the image processing only for a portion of the whole image of the forged fingerprint. A method for determining a forged fingerprint comprises the following steps of: irradiating light to an object, placed on a fingerprint contact surface, on a prism(S301); obtaining an image of the object formed by the irradiated light(S303); detecting a region corresponding to a ridge from the obtained image(S305); and determining the object as a biological fingerprint when the average intensity of the detected ridge region is smaller than a preset value(S319), while determining the object as a forged fingerprint when the average intensity is larger than the preset value(S321).

Description

Apparatus for Distinguishing Forged Fingerprint and Method therof}

1 is a block diagram of an optical fingerprint recognition device having a fake fingerprint determination device of the present invention,

FIG. 2 is an example of an image obtained using the biopsy light source of FIG. 1, and

3 is a flowchart provided to explain a fake fingerprint determination method according to an embodiment of the present invention.

The present invention relates to a fake fingerprint determination device for fingerprint recognition and a determination method thereof.

The use of user biometric information with invariability and uniqueness for personal authentication using information devices has already been generalized. Among them, fingerprint recognition has become the most noticeable and generalized authentication means compared to other means due to its superior performance compared to a simple structure.

Normal personal authentication is mainly used in areas where security is important, such as access control, e-commerce, financial transactions, security of personal computers (PCs), and office payment systems. The most important thing is to effectively distinguish fingerprints (hereinafter referred to as 'fake fingerprints').

One method of making a fake fingerprint is to contact a fingerprint reader with a liquid or a liquid such as water or oil on a paper or film on which a fingerprint image is printed. A typical fingerprint recognition device recognizes such fake fingerprints and performs false authentication.

Applicant has already applied for a non-contact biometric fingerprint identification method (Domestic Patent Application No. 10-2006-0030377) by using a capacitance to distinguish the imitation fingerprint. However, even with such a method, when the user attaches the imitation finger to a finger, it is easy to distinguish the imitation fingerprint by the imitation fingerprint discrimination technique such as the non-contact biometric fingerprint detection method using the conventionally proposed capacitance. not.

Disclosure of the Invention An object of the present invention is to provide a counterfeit fingerprint judging device capable of discriminating a counterfeit fingerprint and a human biometric fingerprint and a method of determining the same.

In order to achieve the above object, according to the present invention, a fingerprint image determining method for acquiring a fingerprint image of an object in contact with a fingerprint contact surface of a prism and determining whether the object is a biometric fingerprint or an imitation fingerprint is provided on the fingerprint contact surface on the prism. Irradiating light toward the object; Acquiring an image of the object formed by the irradiated light; Detecting an area corresponding to the ridge in the acquired image; And determining the object as a bio fingerprint when the average brightness value of the detected ridge region is smaller than a set value, and determining the object as a fake fingerprint when the detected ridge area is larger than the set value.

According to another embodiment of the present disclosure, the method of determining the imitation fingerprint according to the present invention may replace the object if the number of pixels having a brightness value smaller than a reference brightness value among the pixels of the detected ridge region is larger than a reference number. Determining as a bio fingerprint, and may be determined as a fake fingerprint when small.

The determining may be performed when the number of pixels of the detected ridge area is in a range of about 30% to 70% of the total number of pixels, and the number of pixels of the detected ridge area is in the range. In case of departure, it may be determined that the object is a fake fingerprint.

In addition, the determining may be performed for a portion of the detected ridge region.

According to another embodiment of the present invention, an optical refractor having a fingerprint contact surface to which an object for fingerprint image acquisition and an exit surface to which the image of the fingerprint is emitted, and an internal light source for irradiating fingerprint recognition light with the optical refractor A fingerprint recognition device for acquiring a fingerprint image of the object according to a predetermined optical fingerprint recognition method, including a biometric light source, at least one optical lens, an image sensor, a fake fingerprint determination unit and a light emission control unit.

The biodetermining light source irradiates light onto an object on the fingerprint contact surface from above the optical refractor, and the at least one optical lens is provided adjacent to the exit surface to form an image emitted from the optical refraction machine. Accordingly, the image sensor acquires an image formed on the optical lens.

The imitation fingerprint determination unit detects a region corresponding to the ridge in the image acquired by the image sensor, and if the average brightness value of the detected ridge region is smaller than a set value, determines the object as a bio fingerprint, and when the imitation fingerprint is large Judging by.

When receiving the determination result that the object is a biological fingerprint from the imitation fingerprint determination unit, the light emission control unit turns off the biological determination light source and turns on the internal light source to perform the fingerprint recognition.

Hereinafter, the present invention will be described in detail with reference to the drawings.

1 is a block diagram of an optical fingerprint recognition device having a fake fingerprint determination device of the present invention. Fingerprint recognition device 100 of Figure 1 is implemented to include the imitation fingerprint determination means of the present invention.

Referring to FIG. 1, the fingerprint recognition device 100 may include a prism 110, an internal light source 131 for irradiating a fingerprint recognition light source toward the prism 110, an optical lens 133 for imaging image information of a fingerprint, The image sensor 135, the biological determination light source 150, and the controller 170 are included.

The prism 110 includes a fingerprint contact surface 110a through which the fingerprint is contacted and an emission surface 110b through which light (fingerprint image) reflected or scattered from the fingerprint contact surface 110a is emitted. As shown in FIG. 1, the prism 110 not only has four sides (or trapezoids) in its cross-sectional shape (or a shape other than an optically unused surface), but also has three sides (triangles) in its cross-sectional shape. In addition to the prism, a wider concept of optical refractor can be used.

First, the basic fingerprint recognition process of the optical fingerprint recognition device 100 of FIG. 1 is as follows. When the user touches the finger on the fingerprint contact surface 110a, light emitted from the internal light source 131 passes through the fingerprint contact surface 110a and the emission surface 110b of the prism 110 to form an image on the optical lens 133. It is input to the image sensor 135. In the scattered fingerprint recognition device 100 as shown in FIG. 1, the light emitted from the internal light source 131 is incident on the fingerprint contact surface 110a at an angle smaller than the critical angle for perpendicular or total reflection. The light emitted from the internal light source 131 passes or scatters along the valleys and ridges of the fingerprint in contact with the fingerprint contact surface 110a to form a fingerprint image. The image sensor 135 obtains an image of the fingerprint in contact with the fingerprint contact surface 110a by outputting a digital fingerprint image signal, which is an electrical signal corresponding to the incident fingerprint image.

However, the fingerprint recognition device 100 applied to the present invention is not limited to the scattering equation shown in FIG. 1. Thus, as described above, the prism 110 is not limited in its cross-sectional shape such as trapezoid or triangle, and the position of the internal light source 131 is also provided at various positions according to the fingerprint recognition method and the shape of the prism 110. Can be.

The biological judgment light source 150 is provided above the prism 110 to irradiate predetermined light toward the fingerprint contact surface 110a. Since the object for fingerprint input is in contact with the fingerprint contact surface 110a, the light emitted from the biopsy light source 150 is irradiated toward the object on the fingerprint contact surface 110a, and transmits the object according to the optical characteristics of the object. Incident on the prism 110 or reflected or refracted by the object.

The biodetermination light source 150 preferably uses a light source having a predetermined viewing angle (for example, about 30 °) around the optical axis of the light source.

The controller 170 controls the overall operation of the fingerprint recognition device 100 including acquiring a fingerprint image.

In addition, the controller 170 may include a light emission control unit 171 and a fake fingerprint determination unit 173 to determine whether the fingerprint contacted to the fingerprint contact surface 110a is a biometric fingerprint or a fake fingerprint.

The light emission controller 171 controls the on and off of the internal light source 131 and the biological determination light source 150. When a predetermined object is in contact with the fingerprint contact surface 110a, the light emission control unit 171 first turns on the biological determination light source 150 to cause the imitation fingerprint determination unit 173 to cause the object to be a human finger (that is, a living body). Fingerprint).

When the imitation fingerprint determination unit 173 determines that the object is a finger, the emission control unit 171 turns off the biopsy light source 150 and turns on the internal light source 131 to perform a fingerprint recognition procedure for the bioprint. Be sure to

The fake fingerprint determination unit 173 turns on the biodetection light source 150 and then determines whether the fingerprint contacted to the fingerprint contact surface 110a is a fake fingerprint based on the digital fingerprint image signal input from the image sensor 135. Done. The imitation fingerprint determination unit 173 provides the determination result to the light emission control unit 171 to turn on the internal light source 131 to perform a fingerprint recognition process.

Hereinafter, referring to FIGS. 2 and 3, a method of determining a fake fingerprint by using the biodetection light source 150 will be described. FIG. 2 is an example of an image acquired using the biodetection light source of FIG. 1.

2 (a) is an image obtained by using a biometric fingerprint, (b) is an image obtained by using a fake fingerprint (paper on which the fingerprint image is printed). 2 (a) and 2 (b) are inverted images obtained by the image sensor 135, the dark portions in (a) and (b) are light incident portions.

When the object in contact with the fingerprint contact surface 110a is the user's finger corresponding to the bio fingerprint, the light emitted from the biodetection light source 150 passes through the user's finger. The light transmitted through the finger is refracted by the prism 110 and incident to the image sensor 135.

According to the experiment, the light irradiated with the finger does not penetrate the finger in the same shape, but is different from the valleys and ridges of the fingerprint. Therefore, the image acquired by the image sensor 135 is not an image displayed with the same amount of light over the entire finger, but is an image in which the fingerprint of the finger in contact with the fingerprint contact surface 110a is displayed as shown in FIG.

In FIG. 2A, the dark portion A corresponds to the ridge, the bright portion B corresponds to the valley, and the amount of light incident on the image sensor 135 is actually the dark portion A. It can be seen that the ridges are relatively more than the bones in the bright part (B).

Therefore, the amount of light passing through the finger to the prism 110 is different from the valleys and ridges of the fingerprint to form a fingerprint image, and is obtained by the image sensor 135.

On the contrary, when the object in contact with the fingerprint contact surface 110a is a dummy fingerprint, an image different from that of the bio fingerprint is obtained according to the type of the object forming the dummy fingerprint.

For example, when the imitation fingerprint is made of an opaque material, since the light emitted from the biopsy light source 150 does not pass through the imitation fingerprint, the image sensor 135 does not acquire any image.

When the imitation fingerprint has a relatively small amount of transmission, such as a paper on which a fingerprint image is printed, the total amount of transmission is very small even though the light emitted from the biopsy light source 150 passes through the paper. Therefore, the image acquired by the image sensor 135 will also be a very dark image. FIG. 2 (b) is an inverted image obtained by the image sensor 135 and is a very bright image. Accordingly, it can be seen that the image acquired by the image sensor 135 is an overall dark image, and the light that is actually incident on the image sensor 135 is very small.

As shown in the image attached to FIG. 2, since the image acquired using the biopsy light source 150 appears differently for the biometric fingerprint and the imitation fingerprint, the fingerprint recognition device 100 of the present invention may include an image sensor 135. Based on the image obtained from the image is determined whether the object in contact with the fingerprint contact surface (110a) is a bio fingerprint or a fake fingerprint.

Hereinafter, referring to FIG. 3, a method of determining a fake fingerprint for determining whether an image acquired by using the biodetection light source 150 is a biometric fingerprint or a fake fingerprint is described. The imitation fingerprint determination unit 173 detects the ridge region from the image acquired by the image sensor 135 and determines whether the imitation fingerprint is based on whether the average brightness value of the corresponding ridge region is larger than the set value.

3 is a flowchart provided to explain a fake fingerprint determination method according to an embodiment of the present invention.

When the object is in contact with the fingerprint contact surface 110a, the light emission controller 171 turns on the biodetection light source 150 (S301).

As the image sensor 135 is turned on, the image sensor 135 acquires an image incident through the prism 110 and outputs a digital image signal to the dummy fingerprint determination unit 173 (S303).

When the imitation fingerprint determination unit 173 receives the digital video signal from the image sensor 135, the imitation fingerprint determination unit 173 detects the ridge region from the received video signal. The detection of the ridge region uses an experimentally obtained brightness value (hereinafter referred to as ridge value) to distinguish the ridge region from the bone region. The imitation fingerprint determination unit 173 detects the ridge region by detecting a pixel having a brightness value equal to or higher than the ridge value (S305).

The imitation fingerprint determination unit 173 calculates the number of pixels of the detected ridge region (S307), and determines whether the calculated number of pixels of the ridge region is within a predetermined range. Since the ratio of the ridge region of the biofingerprint to the pixels of the entire image is within a predetermined range (for example, about 50 ± 20%), the imitation fingerprint judgment is determined by determining whether the number of pixels of the calculated ridge region is within the predetermined range. The unit 173 may detect a counterfeit fingerprint having a particularly high transmittance or a counterfeit fingerprint having a particularly low transmittance (S309).

Therefore, as a result of the determination in step S309, the imitation fingerprint determination unit 173 determines that the object contacted with the fingerprint contact surface 110a is a fake fingerprint when the calculated number of pixels of the ridge region is not within the predetermined range (S311).

When the number of pixels of the ridge area calculated as a result of the determination in step S309 is within a predetermined range, the imitation fingerprint determination unit 173 determines the number of pixels (number of darker pixels) whose brightness value of the pixel of the ridge area is smaller than the reference brightness value. To calculate. Here, the imitation fingerprint determination unit 173 may perform this step only on a part of the entire ridge region (S313).

The imitation fingerprint determination unit 173 determines whether the number of pixels calculated in step S303 is greater than the reference number. Referring to FIG. 2, the imitation fingerprint made of paper has a large brightness value. In other words, in the ridge region of the dummy fingerprint of FIG. 2, the number of pixels having a brightness value smaller than the reference brightness value is smaller than the predetermined reference number. The reference number can be determined experimentally (S315).

If the number of pixels calculated in step S303 is greater than the reference number, the fake fingerprint determination unit 173 calculates an average brightness value of the detected ridge region. Here, the imitation fingerprint determination unit 173 may perform this step only for a part of the entire ridge region (S317).

The imitation fingerprint determination unit 173 determines whether the calculated average brightness value is lower than the set value (S319).

The imitation fingerprint determination unit 173 determines that the object in contact with the fingerprint contact surface 110a as the bio fingerprint when the calculated average brightness value is lower than the set value (S321), and when the calculated average brightness value is larger than the set value. Judging by fake fingerprints.

Although the method of determining the imitation fingerprint described above has been described as a series of processes, it may be determined whether the imitation fingerprint is applied individually by applying the steps S309, S315 or SS319.

In addition, the above method is based on the part displayed by darker lines than other areas of the fingerprint image, and the example of FIG. 3 is based on the ridge part of FIG. 2. However, the area indicated by the dark line of the fingerprint image may be a region corresponding to the bone by the inversion of the acquired image or other optical means, and in this case, the method of the present invention may be similarly applied to the region corresponding to the bone. Applicable

The imitation fingerprint determination unit 173 provides the light emission control unit 171 with a result of determining whether an object in contact with the fingerprint contact surface 110a is a bio fingerprint. When the light emission control unit 171 receives the determination result of the bio fingerprint, the biometric light source 150 is turned off and the internal light source 131 is turned on to perform a fingerprint recognition process on the bio fingerprint.

The invention can be implemented in methods, devices and systems. In addition, when the present invention is implemented in computer software, the components of the present invention may be replaced with code segments necessary for performing necessary operations. The program or code segment may be stored in a medium that can be processed by a microprocessor and transmitted as computer data coupled with carrier waves via a transmission medium or communication network.

The media that can be processed by the microprocessor include electronic circuits, semiconductor memory devices, ROMs, flash memory, electrically erasable programmable read-only memory (EEPROM), floppy disks, optical disks, and hard disks. (Hard) Includes the ability to transmit and store information such as disks, fiber optics, wireless networks, and the like. Computer data also includes data that can be transmitted over electrical network channels, optical fibers, electromagnetic fields, wireless networks, and the like.

In addition, although the preferred embodiment of the present invention has been shown and described above, the present invention is not limited to the above-described specific embodiment, the technical field to which the invention belongs without departing from the spirit of the invention claimed in the claims. Of course, various modifications can be made by those skilled in the art, and these modifications should not be individually understood from the technical spirit or the prospect of the present invention.

As described in detail above, the apparatus for judging a fake fingerprint according to the present invention can easily and effectively determine whether it is a fake fingerprint, and is particularly excellent for a fake fingerprint such as a paper on which a fingerprint image is printed.

Since the imitation fingerprint determination method of the present invention can be performed only by image processing on a part of the entire fingerprint image, the imitation fingerprint determination algorithm is simplified and its speed is also increased.

Furthermore, since the imitation fingerprint determination device of the present invention only needs to add a separate light source to the upper side of the existing fingerprint recognition device, the existing fingerprint recognition device can be used as it is, and the configuration of the entire hardware is simple.

Claims (8)

In the imitation fingerprint determination method of acquiring a fingerprint image of an object in contact with the fingerprint contact surface of the prism to determine whether the object is a bio fingerprint or a fake fingerprint, Irradiating light onto the fingerprint contact surface from above the prism; Acquiring an image of the object formed by the irradiated light; Detecting an area corresponding to the ridge in the acquired image; And And determining the object as a biometric fingerprint when the average brightness value of the detected ridge region is smaller than a set value, and determining the object as a fake fingerprint when the detected ridge region is larger than the set value. In the imitation fingerprint determination method of acquiring a fingerprint image of an object in contact with the fingerprint contact surface of the prism to determine whether the object is a bio fingerprint or a fake fingerprint, Irradiating light onto the fingerprint contact surface from above the prism; Acquiring an image of the object formed by the irradiated light; Detecting an area corresponding to the ridge in the acquired image; And And determining the object as a bio fingerprint when the number of pixels having a brightness value smaller than a reference brightness value among the pixels of the ridge region is greater than the reference number, and determining as an imitation fingerprint when the number is smaller than the reference number. How to determine the fake fingerprints. The method according to claim 1 or 2, The determining step is performed when the number of pixels of the detected ridge region is in the range of about 30% to 70% of the total number of pixels, And determining that the object is a dummy fingerprint when the number of pixels of the detected ridge region is out of the range. The method according to claim 1 or 2, And the determining is performed on a portion of the detected ridge region. A predetermined optical fingerprint recognition method including an optical refractor having a fingerprint contact surface to which an object for fingerprint image acquisition is touched and an exit surface at which the image of the fingerprint is emitted, and an internal light source that irradiates the fingerprint recognition light with the optical refractor In the fingerprint recognition device to obtain a fingerprint image of the object according to, A biological judgment light source for irradiating light toward the object on the fingerprint contact surface from above the optical refractor; At least one optical lens provided adjacent to the emission surface to form an image output from the optical refraction device; An image sensor for acquiring an image formed on the optical lens; A fake fingerprint which detects an area corresponding to the ridge in the image obtained by the image sensor, and if the average brightness value of the detected ridge area is smaller than a set value, determines the object as a bio fingerprint, and when it is large, a fake fingerprint. Determination unit; And And a light emission control unit which turns off the internal light source and turns on the internal light source when receiving the determination result that the object is a biofingerprint from the imitation fingerprint determining unit. A predetermined optical fingerprint recognition method including an optical refractor having a fingerprint contact surface to which an object for fingerprint image acquisition is touched and an exit surface at which the image of the fingerprint is emitted, and an internal light source that irradiates the fingerprint recognition light with the optical refractor In the fingerprint recognition device to obtain a fingerprint image of the object according to, A biological judgment light source for irradiating light toward the object on the fingerprint contact surface from above the optical refractor; At least one optical lens provided adjacent to the emission surface to form an image output from the optical refraction device; An image sensor for acquiring an image formed on the optical lens; Detecting the area corresponding to the ridge in the image obtained by the image sensor, and if the number of pixels having a brightness value less than the reference brightness value of the pixels of the detected ridge area is larger than the reference number, the object is determined as a bio fingerprint And, when small, the fake fingerprint judgment unit judged as a fake fingerprint; And And a light emission control unit which turns off the internal light source and turns on the internal light source when receiving the determination result that the object is a biofingerprint from the imitation fingerprint determining unit. The method according to claim 5 or 6, The imitation fingerprint judging unit may determine the object as an imitation fingerprint if the number of pixels of the ridge region detected is less than about 30% or greater than 70% of the total number of pixels before performing the determination. Fingerprint reader. The method according to claim 5 or 6, The fingerprint recognition unit, the fingerprint recognition device, characterized in that for performing a determination on a portion of the detected ridge area.

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