KR20100123812A - Apparatus for distinguishing living body fingerprint and method therof - Google Patents

Abstract

PURPOSE: A fingerprint determining device and a determining method are provided to determine human fingerprint using color change of fingerprint due to pressure change. CONSTITUTION: A light refractor comprises a fingerprint input window which has contacts with fingerprint. An optical lens system(133) makes image coming out from the light refractor. A color image sensor(135) gets a color fingerprint image from the image. A human body recognition unit(153) calculates the color information of the color fingerprint image. In case the color information belongs to the reference color phase range of the human fingerprint, the human body recognition unit decides fingerprint as a human fingerprint.

Description

Apparatus for Distinguishing Living Body Fingerprint and Method therof}

According to the present invention, whether a fingerprint is a biometric fingerprint using a unique color of the biometric fingerprint and a change in the fingerprint color due to a pressure change when the biometric fingerprint contacts the fingerprint input window is obtained. The present invention relates to a biofingerprint judging device capable of judging and a judging method thereof.

Biometric methods are widely used for authentication of individuals due to their uniqueness and high invariability. In this biometric method, fingerprint recognition is convenient and simple to use, making it the oldest and most generalized recognition method compared to other biometric fields.

In fact, fingerprint recognition devices are spreading to various fields that require authentication, such as access control, electronic commerce, financial transactions, security of personal computers (PCs), and office payment systems. However, the fingerprint recognition device has a problem of false authentication by imitation fingerprints despite the convenience, accuracy and economics of authentication. For this reason, various algorithms have been developed to improve and prevent the damage of false authentication by fake fingerprints.

Imitation fingerprints can be made by soaking or soaking transparent liquids, such as water or oil, on printed paper or film, or by using materials with properties similar to skin tissue, such as silicone or rubber. A typical fingerprint recognition device recognizes such a fake fingerprint and performs false authentication.

In addition, when the user attaches the imitation fingerprint to the finger, the user can distinguish the imitation fingerprint by the imitation fingerprint identification technology such as the temperature measurement method, the potential measurement method, the pressure measurement method, the blood flow measurement method, and the sweat gland measurement method. Hard.

An object of the present invention is to determine whether a fingerprint is a biometric fingerprint by using a unique color of the biometric fingerprint and a change in the fingerprint color due to a pressure change when the biometric fingerprint contacts the fingerprint input window. The present invention provides a biometric fingerprint determination device and a method of determining the same.

In accordance with an aspect of the present invention, a method for determining a biofingerprint according to the present invention comprises: obtaining a color fingerprint image of a fingerprint in contact with a fingerprint input window of a prism by irradiating light with a prism, and obtaining color information of the obtained color fingerprint image; And determining whether the calculated color information is within the reference color range of the biometric fingerprint, and determining the fingerprint as the biometric fingerprint if it falls within the reference color range.

Here, when the average of the color information at two or more time points including the first time point and the second time point while the fingerprint is in contact with the fingerprint input window does not fall within the reference color range, the fingerprint is a dummy fingerprint. The method may further include determining.

Here, the reference color range may include two or more colors including a color obtained at one time point including the first and second time points with respect to a biological fingerprint, or the first time point and the second time point with respect to a biological fingerprint. It is preferable that the range includes a predetermined error in the average of the acquired color at the viewpoint.

According to an embodiment of the present disclosure, the calculating of the biometric fingerprint determination method may include calculating the color information at a first point and a second point of time when the fingerprint is in contact with the fingerprint input window. When the color information calculated at the first time point and the second time point falls within the reference color range, respectively, and there is a color change between the first time point and the second time point, the fingerprint may be determined as a biometric fingerprint.

The determining may include calculating color change information about a change in color information calculated at the first time point and a second time point, and the color change information may be applied to a color change of a biometric fingerprint according to a change in contact pressure. Determining the fingerprint as a biometric fingerprint if the reference condition is satisfied.

One of the first time point and the second time point is preferably a time point at which the color fingerprint image is acquired as the fingerprint contacts the fingerprint input window.

,

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중 적어도 하나이다. The reference conditions of the present invention,

,

And

Of at least one.

Here, R (1) and G (1) are the brightness of the red and green components of the color fingerprint image at the first time, respectively, and R (2) and G (2) are the red color of the color fingerprint image at the second time, respectively. And the brightness of the green component, ΔR = R (2) -R (1), ΔG = G (2) -G (1) and ΔB are the blue component at the second and first time points of the color fingerprint image. Brightness is tea.

The color information may be brightness levels of red, green, and blue components, and the color information may be about a ridge portion of the color fingerprint image.

Biometric fingerprint determination apparatus according to another embodiment of the present invention, an optical refractor, a light source, an optical lens system, a color image sensor and a biometric unit.

Here, the optical refractor includes a fingerprint input window to which the fingerprint is in contact. When a light source emits light for acquiring an image of the fingerprint with the optical refractor, the optical lens system forms the image output from the optical refractor. Accordingly, the color image sensor obtains a color fingerprint image from the image formed on the optical lens system.

The biometric unit calculates color information of the color fingerprint image acquired by the color image sensor, and determines the fingerprint as a biometric fingerprint when the color information falls within a reference color range of the biometric fingerprint.

The biometric fingerprint determination method and apparatus according to the present invention can effectively distinguish between the biological fingerprint and the imitation fingerprint, and can distinguish not only the general paper but also the imitation fingerprint of a material such as film, silicone, gelatin, etc., which was difficult to distinguish.

When the biometric fingerprint determination method of the present invention is applied to a conventional fingerprint recognition device, a separate device is not required. The fingerprint recognition device may determine whether a biometric fingerprint is obtained using a fingerprint image acquired for fingerprint recognition or registration, and perform fingerprint authentication based on the determination at one time.

1 is a block diagram of an apparatus for determining a fingerprint according to an embodiment of the present invention;
2 illustrates a fingerprint image obtained from a biometric fingerprint and a dummy fingerprint;
3 is a graph illustrating a color structure of a fingerprint image obtained from a biometric fingerprint and a dummy fingerprint;
4 is a graph illustrating a change in color according to a change in contact pressure of a biometric fingerprint, and
5 is a flowchart provided to explain a method for determining a biometric fingerprint according to an exemplary embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail with reference to the drawings.

The biometric fingerprint determination device of the present invention determines whether the corresponding fingerprint is a fake fingerprint or a biometric fingerprint by using the optically obtained color fingerprint image. The biometric fingerprint determination device of the present invention can be applied to any device that acquires and processes a fingerprint image as well as a fingerprint recognition device.

1 is a block diagram of a biometric fingerprint determination device according to an embodiment of the present invention, the biometric fingerprint determination device 100 is an example implemented in the form of a fingerprint recognition device.

The biometric fingerprint determination apparatus 100 of FIG. 1 may obtain a fingerprint image from a fingerprint (or a finger) of the user and determine whether the corresponding fingerprint is a biometric fingerprint or a fake fingerprint, based on the determination result. Register and / or authenticate users.

The biological fingerprint determination apparatus 100 obtains a fingerprint image according to a so-called optical type using an optical refractor. In addition, the biometric fingerprint determination apparatus 100 is not limited to a so-called scattering or absorption type, but may be applied to any optical fingerprint image acquisition device using light reflected or scattered from a user fingerprint.

The biometric fingerprint determination device 100 of the example shown in FIG. 1 includes a prism 110 having one surface provided as a fingerprint input window 110a, a light source 131 for emitting a fingerprint image acquisition light to the prism 110, and a color image. The sensor 135 includes an optical lens system 133 and a controller 150 for forming a fingerprint image on the color image sensor 135.

The prism 110 includes a fingerprint input window 110a through which the fingerprint is in contact and an emission surface 110b through which light (fingerprint image) reflected or scattered from the fingerprint input window 110a is emitted. As shown in FIG. 1, the prism 110 may have not only a triangular cross-sectional shape (or a shape other than an optically unused surface) but also a four-sided (trapezoid) shape. The concept of photorefractors can be used.

The light source 131 uses white light including three primary colors of light, red, green, and blue. The location of the light source 131 may be provided at various locations according to the fingerprint recognition method and the shape of the prism 110.

The color image sensor 135 converts the light incident through the prism 110 and the optical lens system 133 into a digital color fingerprint image, which is an electrical signal, and outputs it to the controller 150. The color fingerprint image includes color information, brightness, and shape information of the fingerprint.

Light irradiated from the light source 131 toward the incidence surface 110c of the prism 110 is reflected or scattered in the fingerprint input window 110a to which the user's fingerprint is contacted, and is emitted through the emission surface 110b. The image is formed by the lens system 133 and input to the color image sensor 135.

The controller 150 determines whether the fingerprint in contact with the fingerprint input window 110a is a biometric fingerprint or a fake fingerprint based on the color fingerprint image provided from the color image sensor 135 and performs a fingerprint recognition process. To this end, the controller 150 includes a fingerprint recognition unit 151 and a biometric unit 153.

The fingerprint recognition unit 151 recognizes a user's fingerprint according to a predetermined image processing algorithm and an authentication algorithm.

According to an embodiment, the fingerprint recognition unit 151 does not perform a fingerprint recognition process every time, and receives the fingerprint image received from the color image sensor 135 only when receiving the determination result of the biometric fingerprint from the biometric unit 153. The user can be authenticated by extracting the feature points. If the fingerprint in contact with the fingerprint input window 110a is identified as a fake fingerprint, the fingerprint recognition unit 151 may perform a process for rejecting a predetermined recognition.

The biometric unit 153 determines whether the fingerprint in contact with the fingerprint input window 110a is a biometric fingerprint or a counterfeit fingerprint based on the fingerprint image input through the color image sensor 135 and recognizes the result of the fingerprint recognition. Output to the unit 151.

The biometric unit 153 uses points of different colors of light reflected from the biological skin tissue and the imitation fingerprint (first determination). Further, it is determined whether the fingerprint is a biometric based on the color change of the fingerprint image according to the change in the contact pressure which naturally occurs when the user contacts the fingerprint with the fingerprint input window 110a (second determination). These two stages of determination are not necessarily performed all at once, and each of them may be presented as a method for biometric fingerprint determination.

The determination of the biometric unit 153 may use the entire color fingerprint image received from the color image sensor 135, or may target a portion of the color fingerprint image (for example, a predetermined pixel in the center).

The image acquired by reflecting white light from the surface of the biometric fingerprint reflects the color information of the skin surface. When white light having various wavelengths is incident on biological tissues, some wavelengths of light are absorbed into the tissues and some are reflected back by components such as proteins, hemoglobin, melanin, or water in the skin tissues. The color fingerprint image generated by converting the reflected light source has color information according to the property of the biometric fingerprint. Human palms, especially the fingerprints, are mostly light pink. This is because relatively large amounts of capillaries are gathered compared to other parts of the skin, causing the red color of the blood to appear pink through the skin tissue.

In contrast, the dummy fingerprint has color information different from that of the biological fingerprint.

FIG. 2 is a diagram illustrating a fingerprint image obtained from a biometric fingerprint and a dummy fingerprint, and FIG. 3 is a graph illustrating a color structure of a fingerprint image obtained from a biometric fingerprint and a fake fingerprint.

The fingerprint image of FIG. 2 is based on a so-called scattered fingerprint image acquisition method in which the ridge is brighter than the bone, but the original fingerprint image is inverted so that the ridge, the valley and the background of the fingerprint are easily distinguished. Therefore, the background is black to white, and the ridges are dark (not complementary) but dark.

(A) and (b) of FIG. 2 are color fingerprint images obtained from a biometric fingerprint, in which (a) is a low contact pressure state and (b) is a higher contact pressure state. Here, the low contact pressure state and the high contact pressure state represent the degree of intensity of the fingerprint in contact with the fingerprint input window 110a, and it can be seen that the color of the fingerprint image changes according to the change in the contact pressure.

(C), (d), (e), (f), and (g) of FIG. 2 are rubber, paper with fingerprints printed in black and white, paper with fingerprints printed in color, transparent silicone, and fake fingerprints in film form, respectively. Is a video of.

Referring to Figure 2, it can be seen that the color of the biological fingerprint is different from the dummy fingerprint. However, the shape of the ridge is very similar, it can be seen that it is difficult to determine the biometric fingerprint in a method that does not use color information as in the prior art.

The graph of FIG. 3 shows color information of a fingerprint image by a living body (low contact pressure state), film, paper, rubber and transparent silicone. The vertical axis represents the relative magnitude of the brightness of the color.

In the case of biometric fingerprints (ridges), red has the highest proportion, followed by green, and blue has the lowest brightness. It can be seen that the color structure of the dummy fingerprint is different from that of the biological fingerprint. For example, in the case of the transparent silicon having the closest distribution to the living body, the ratios and intensities of red, green, and blue were different. The present invention determines the biometric fingerprint and the fake fingerprint based on this feature.

However, some fake fingerprints may have the same color information as the biometric fingerprint. In this case, the biometric fingerprint determination apparatus 100 of the present invention considers the color change of the biometric fingerprint according to the change of the contact pressure.

When the skin tissue is under pressure, that is, when there is a change in contact pressure that occurs naturally in the process of contacting the biometric fingerprint with the fingerprint input window 110a, the capillaries become narrow and the movement of blood located in the pressured place is performed. The skin color changes from red to yellow. Due to the nature of the area where the fingerprint is located on the finger, capillaries are gathered more than other skin tissues. This change in color due to pressure is a characteristic that is not observed in imitation fingerprints using commonly used paper, film, silicon, rubber, gelatin, and the like.

FIG. 4 is a graph showing the color change according to the change in the contact pressure of the biometric fingerprint. In general, when there is a pressure change in the biometric fingerprint (the ridge portion) in the low contact pressure state, which is a red series, the ratio of red and green becomes similar and blue. As the ratio of the decreases, the overall brightness increases, and it can be seen that the color turns to bright yellow.

Specifically, the difference in brightness of red and green at high contact pressure is smaller than the difference of brightness of red and green at low contact pressure. The unusual color change of the biometric fingerprint can be summarized as in Equations 1 to 4 below.

Here, each variable included in the equation is the brightness of the corresponding color, R (1) is the brightness of the red component in a low contact pressure state, G (1) is the brightness of the green component in a low contact pressure state, B (1) Denotes the brightness of the blue component in a low contact pressure state. R (2) represents the brightness of the red component in a high contact pressure state, G (2) represents the brightness of a green component in a high contact pressure state, and B (2) represents the brightness of a blue component in a high contact pressure state. ΔR = R (2) -R (1), ΔG = G (2) -G (1), and ΔB = B (2) -B (1). ΔR, ΔG, and ΔB are not zero.

R (1), G (1), B (1), R (2), G (2), and B (2) are based on the color of the ridges in the fingerprint. Of course, according to an embodiment, it may be based on the color of a certain area including the ridges and valleys, or may be based on the color of the entire color fingerprint image, in this case, for the condition of Equation 1 to 4 or the biometric fingerprint The reference color may vary.

In the case of counterfeit fingerprints such as paper, film, rubber, silicone, gelatin, even if there is a change in contact pressure, there is no change in color structure such as a biometric fingerprint. The biometric fingerprint determination apparatus 100 of the present invention may distinguish the fake fingerprint and the biometric fingerprint by using the change of the color structure according to the change of the contact pressure. For example, the biometric fingerprint determination apparatus 100 may determine whether the corresponding fingerprint is a dummy fingerprint or a biometric fingerprint based on whether one or two or more conditions of Equation 2 to Equation 4 are satisfied.

The low contact pressure state or the high contact pressure state described above can refer to the state in which the pressure change is started and the state in which the pressure is near the maximum, but can be described as the time concept in which the contact of the fingerprint is performed. have.

In other words, the 'low contact pressure state' or 'high contact pressure state' may correspond to two times (a first time point and a second time point) that are physically spaced and there is a change in the contact pressure. The separation of two time periods is enough time to experimentally confirm that the change in color can be detected. For example, the low contact pressure state may correspond to a time point (first time point) at which the fingerprint image is input from the color image sensor 135, and the high pressure state may be a predetermined time from the time point at which the fingerprint image is input from the color image sensor 135. The elapsed time point (second time point) may correspond.

R (1), G (1), and B (1) in the previous equations are the brightness of the red, green, and blue components at the first time point, and R (2), G (2), and B (2) are This corresponds to the brightness of the red, green, and blue components at the second time point.

According to an embodiment, the biometric fingerprint determination device 100 may check a desired pressure state by providing a separate pressure sensor or a contact sensor around the fingerprint input window 110a or the surroundings thereof.

Hereinafter, with reference to FIG. 5, a preferred embodiment of the biometric fingerprint determination of the biometric fingerprint determination device 100 of the present invention will be described.

5 is a flowchart provided to explain a method for determining a biometric fingerprint according to an exemplary embodiment.

When the fingerprint touches the fingerprint input window 110a, the light emitted from the light source 131 is imaged on the color image sensor 135 through a predetermined optical path, and from the moment the fingerprint touches the fingerprint input window 110a. The color image sensor 135 generates a digital color fingerprint image by the light to be imaged and provides it to the biometric unit 153 (S501 and S503).

The biometric unit 153 calculates color information of the ridge of the color fingerprint image input from the color image sensor 135 and information on the change of the color (hereinafter, 'color change information'). In this case, the calculation of the color information and the color change information may be based on the entire fingerprint image corresponding to the size of the color image sensor 135, or may be based on a part of the entire fingerprint image. The color information may be obtained from a color fingerprint image at an arbitrary time point, or may be obtained by averaging the color information from two or more time points. In addition, the color change information is obtained by measuring a change amount of the color information at an arbitrary first time point and a second time point. The contact pressure state and the high contact pressure state may be examples of the first time point and the second time point (S505).

The biometric unit 153 first determines whether the fingerprint is a biometric fingerprint based on whether the calculated color information is within the reference color range. Here, the reference color range may include a predetermined margin or error based on the color of the biometric fingerprint obtained experimentally at the acquisition reference time of the color information, and FIGS. 2 and 3 are examples. S507).

As a result of the determination in step S507, when the calculated color information does not belong to the reference color range, the biometric recognition unit 153 determines the fingerprint as a fake fingerprint (S509).

As a result of the determination in step S507, when the calculated color information belongs to the reference color range, the biometric recognition unit 153 first determines the corresponding fingerprint as the biometric fingerprint, and then determines whether the calculated color change information satisfies the reference condition. do. Here, the reference condition may correspond to at least one of Equations 1 to 4. However, since Equations 1 to 4 are based on the color of the ridges, Equations 1 to 4 may also be changed when the criterion is modified (S511).

As a result of the determination in step S511, when the calculated color change information satisfies the reference condition, the biometric recognition unit 153 determines that the fingerprint as a biometric fingerprint, and if it does not satisfy the reference condition, determines the fingerprint as a dummy fingerprint ( S513).

In the above-described method, the biometric fingerprint determining apparatus 100 of the present invention may determine whether the fingerprint in contact with the fingerprint input window 110a is a biometric fingerprint. The fingerprint recognition unit 151 may perform the fingerprint authentication procedure only on the biometric fingerprint according to the determination result of the biometric recognition unit 153.

According to an embodiment, as described above, the biometric fingerprint determination apparatus 100 may complete the determination on whether the biometric fingerprint is performed without the second determination by the step S511. In contrast, the determination of the step S511 is performed immediately without the determination of the step S507. It may be performed to determine whether the biometric fingerprint.

Color information and color change information of the step S505 was based on the average color of the ridges of all or part of the color fingerprint image, but is not necessarily limited thereto.

For example, the whole or part of the color fingerprint image may be based on an average color obtained by adding up the ridges and the valleys. In this case, the fingerprint image (the image before the inversion) obtained by the scattering formula may be dark because the bone is dark, and the absorption type may be brighter because the bone is bright, and this part should be considered. In addition, if the image generated by the color image sensor () is inverted, the bone becomes bright again in the scattering equation, the bone becomes dark in the absorption equation, and the color of the ridge is changed from the red color to the violet color. The reference conditions for the reference color range or color change information may be appropriately adjusted.

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.

110: prism 110a: fingerprint input window
110b: exit surface 110c: entrance surface
131: light source 133: optical lens system
135: color image sensor

Claims (12)

Irradiating light with a prism to obtain a color fingerprint image of a fingerprint in contact with the fingerprint input window of the prism;
Calculating color information of the acquired color fingerprint image; And
And determining whether the calculated color information is within the reference color range of the biometric fingerprint, and determining the fingerprint as the biometric fingerprint if it falls within the reference color range.
The method of claim 1,
The calculating may include calculating the color information at a first time point and a second time point while the fingerprint is in contact with the fingerprint input window.
The determining may include determining the fingerprint as a biometric fingerprint when the color information calculated at the first time point and the second time point falls within the reference color range, respectively, and there is a color change between the first time point and the second time point. Biological fingerprint determination method, characterized in that.
The method of claim 2,
Whether there is the color change in the determining step,
Calculating color change information about a change in color information calculated at the first and second time points, and wherein the color change information satisfies a reference condition for color change of a biological fingerprint according to a change in contact pressure. Biometric fingerprint determination method.
The method of claim 3,
The reference condition is,

,

And

At least one of
R (1) and G (1) are the brightness of the red and green components of the color fingerprint image at the first time point, respectively, and R (2) and G (2) are the red and green of the color fingerprint image at the second time point, respectively. ΔR = R (2) -R (1), ΔG = G (2) -G (1), and ΔB are the difference in brightness of the blue component at the second and first time points of the color fingerprint image. Biological fingerprint determination method, characterized in that.
The method according to any one of claims 1 to 4,
The color information, the fingerprint method of claim 1, characterized in that the brightness of the red, green and blue components.
The method according to any one of claims 1 to 4,
And the color information is about a ridge portion of the color fingerprint image.
An optical refractor having a fingerprint input window to which the fingerprint is in contact;
A light source for emitting light for acquiring an image of the fingerprint with the optical refractor;
An optical lens system for forming the image output from the optical refractor;
A color image sensor which acquires a color fingerprint image from an image formed on the optical lens system; And
A biometric fingerprint determination method comprising calculating a color information of a color fingerprint image obtained by the color image sensor and determining the fingerprint as a biometric fingerprint when the color information falls within a reference color range of the biometric fingerprint. Device.
The method of claim 7, wherein
The biometric unit,
Calculating color change information about a change in the color information between the first time point and the second time point between the first time point and the second time point while the fingerprint is in contact with the fingerprint input window; When the color information of the first time point and the second time point respectively belong to the reference color range and the color change information satisfies the reference condition for the color change of the biometric fingerprint according to the change in contact pressure, the fingerprint is determined as the biometric fingerprint. Biometric fingerprint determination device.
The method of claim 8,
The reference condition is,

,

And

At least one of
R (1) and G (1) are the brightness of the red and green components of the color fingerprint image at the first time point, respectively, and R (2) and G (2) are the red and green of the color fingerprint image at the second time point, respectively. ΔR = R (2) -R (1), ΔG = G (2) -G (1), and ΔB are the difference in brightness of the blue component at the second and first time points of the color fingerprint image. Biological fingerprint determination device, characterized in that.
The method of claim 7, wherein
The biometric unit,
When the average of the color information at two or more time points including the first time point and the second time point while the fingerprint is in contact with the fingerprint input window does not fall within the reference color range, the fingerprint is determined as a fake fingerprint. Biological fingerprint determination device, characterized in that.
The method according to any one of claims 7 to 10,
The color information, the biometric fingerprint determination device characterized in that the brightness of the red, green and blue components.
The method according to any one of claims 7 to 10,
And the color information is about a ridge portion of the color fingerprint image.

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