JP2763830B2 - Fingerprint input device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fingerprint input device used for fingerprint collation or collation identification.

[0002]

2. Description of the Related Art Conventionally, as a fingerprint input device used for fingerprint collation, a method of directly inputting a fingerprint surface as a two-dimensional image in a non-contact state has been considered. This is because a finger guide for guiding a finger to input a fingerprint pattern to a predetermined position, an opening window is provided on the finger guide corresponding to the assumed fingerprint surface position, and the finger guide is arranged in focus on the assumed fingerprint surface position. In the fingerprint input device equipped with a light source that illuminates the assumed two-dimensional image sensor and the fingerprint surface, a finger is inserted along a finger guide, and the inserted finger is actuated by an imaging switch at the top of the finger, Activate the two-dimensional image sensor and light source,
This is a method of directly imaging the fingerprint surface.

[0003]

In the case of inputting a fingerprint image with the above fingerprint input device, for example, even when a photograph of a finger is pasted on a finger and input to the input device,
Since the input is performed in the same manner as a fingerprint of a living body, there has been a problem that the reliability of the fingerprint collation device is reduced.

Accordingly, an object of the present invention is to determine whether or not an input image is a fingerprint of a living body having three-dimensional irregularities, thereby preventing an erroneous input by an artificially created fingerprint image and improving reliability. It is to provide a fingerprint input device with high reliability.

[0005]

A first feature of a fingerprint input device according to the present invention for achieving the above object is that a first lighting position of a light source and a first lighting position of a light source opposed to each other with a finger to be imaged interposed therebetween. A first fingerprint image photographed by lighting the light source at the first lighting position, and a second fingerprint image photographed by lighting the light source at the second lighting position. And a three-dimensional object determining means for determining whether the subject finger is a three-dimensional object based on the first fingerprint image and the second fingerprint image stored in the storing means. The point is to prepare.

Further, a second fingerprint input device according to the present invention
Are characterized by a first lighting position and a second lighting position of a light source opposed to each other across the subject finger, and a third lighting position and a fourth lighting position of a light source opposed to each other across the subject finger.
A first fingerprint image photographed by turning on a light source at the first lighting position;
A second fingerprint image photographed by turning on the light source at the lighting position, a third fingerprint image photographed by lighting the light source at the third lighting position, and photographing by lighting the light source at the fourth lighting position Storage means for storing the obtained fourth fingerprint image, cumulative d1 of the square of the difference of each pixel between the first fingerprint image and the second fingerprint image stored in the storage means, and storage in the storage means Of the square of the difference between each pixel of the third fingerprint image and the fourth fingerprint image, and the sum d of the cumulative d1 and the cumulative d2
1 + d2, the object to be captured is determined when the cumulative d1 is greater than a first predetermined value, when the cumulative d2 is greater than a second predetermined value, or when the sum d1 + d2 is greater than a third predetermined value. It is characterized in that a three-dimensional object discriminating means for discriminating that the finger is a three-dimensional object is provided.

[0007]

In the fingerprint input device having the first feature,
The photographing means has a first lighting position and a second lighting position of the light source facing each other across the subject finger. This first
The light source is turned on at the lighting position of to take a first fingerprint image,
Further, the light source is turned on at the second lighting position, and a second fingerprint image is photographed and stored in the storage means. Based on the first fingerprint image and the second fingerprint image stored in the storage means in this way, the three-dimensional object determination means determines whether the subject finger is a three-dimensional object.

[0008] In the fingerprint input device having the second feature, the photographing means includes a first lighting position and a second lighting position of the light source opposed to each other across the subject finger, and the light source and the light source facing each other across the subject finger. The third lighting position of the opposing light source and the fourth lighting position
Lighting position. The light source is turned on at this first lighting position to take a first fingerprint image, the light source is turned on at a second lighting position to take a second fingerprint image, and the light source is turned on at a third lighting position. To take a third fingerprint image,
The light source is turned on at the lighting position of, and a fourth fingerprint image is photographed and stored in the storage means. The cumulative d1 of the square of the difference between each pixel between the first fingerprint image and the second fingerprint image thus stored in the storage means, and the square of the difference between each pixel between the third fingerprint image and the fourth fingerprint image. Is obtained, and the sum d1 + d2 of the accumulation d1 and the accumulation d2 is obtained. When the accumulation d1 is larger than the first predetermined value, when the accumulation d2 is larger than the second predetermined value, or when the sum d1 + d2 is the third If it is larger than the predetermined value, it is determined that the subject finger is a three-dimensional object.

[0009]

Embodiments of the present invention will be described below. FIG.
(A) and (b) show an embodiment of claim 1 of the present invention. 2A is a plan view, and FIG. 1B is a side view. In this embodiment, two pairs of two lighting devices are used. The fingerprint input device configured as shown in FIG. 1 is provided with a pair of two lamps 11 and 12 for illuminating a fingerprint surface from a position opposed to each other with a center axis of a photographing system interposed therebetween and in a direction intersecting at right angles thereto. And a pair of two lamps 13 and 14 for illuminating the fingerprint surface from opposite positions with the center axis of the imaging system interposed therebetween.
A CCD 15 for taking a fingerprint image, a lens 16 for focusing on an assumed fingerprint position, lenses 16 and C
It includes a tube 17 that supports the CD 15 and a support base 18 that supports the lamps 11 to 14 and the tube 17.

FIG. 2 shows the connection state of each component. An imaging device 31 (CCD 15, lens 16) for taking a fingerprint image
), A storage device 33 for storing a fingerprint image captured by the imaging device, a lighting device 34 (including lamps 11 to 14) for sequentially lighting lamps for illuminating the fingerprint surface, and controls the overall control. And a central control unit 32. Here, it is assumed that the input image has a resolution of 512 pixels vertically and 512 pixels horizontally, and has such a size that the portion up to the first joint of the finger can be just entered.
The distance between the lamp and the imaging system is 1 cm, and the distance between the lamp and the assumed fingerprint surface is 1 cm.

The input operation is shown in FIGS. less than,
The input operation will be described in detail. First, the central control device 32 detects a signal indicating the start of image input, operates the lamp lighting device 34, turns on the lamp 11, and illuminates the fingerprint surface. Next, a fingerprint image is captured by the imaging device 31. The image data in the imaging device 31 is stored in the central controller 3
2, the data is transferred to and stored in a specific memory area of the storage device 33 (hereinafter referred to as a memory 1). The lamp lighting device 34 detects that the transfer is completed, and turns off the lamp 11. Next, the lamp lighting device 34 turns on the lamp 12 to illuminate the fingerprint surface. Next, the fingerprint image is displayed on the imaging device 3.
Captured at 1. The image data in the imaging device 31 is
The data is transferred to and stored in a specific memory area of the storage device 33 (hereinafter referred to as the memory 2) via the central control device 32. The lamp lighting device 34 detects that the transfer is completed, and turns off the lamp 12. Next, the shading of the image in the memory 1 is removed according to the following equation.

[0012]

(Equation 1)

Here, p (x, y) is the gray value of the pixel at the position (x, y) before shading removal,
₁ (x, y) is the position (x, y) after shading removal
, And N = 16. Similarly, the shading of the image in the memory 2 is removed. Let the gray value of the pixel at the position (x, y) after shading removal be p ₂ (x, y). In the area 61 shown in FIG. 5, the cumulative d ₁ of the square of the difference between each pixel between the images in the memory 1 and the memory 2 is obtained according to the following equation.

[0014]

(Equation 2)

In FIG. 5, w = 512, h = 512,
dw = 50, dh = 50, sw ₁ = 50, sw ₂ = 50,
sh ₁ = 50, is a sh ₂ = 50. If d ₁ > Q ₁ , since the input fingerprint image is of a living body, the image data stored in the memory 1 and the memory 2 is transferred from the external output terminal via the central control device 32 to the normal output terminal. It is output to the feature extraction unit and the like of the fingerprint matching device. If d ₁ ≦ Q ₁ , the process proceeds to the next process.

Here, the principle of determining whether an input image is of a living body or not is described in detail below.
As shown in FIG. 6A, a fingerprint image with shading (the figure is
A cross-sectional view of what is printed on a flat surface)
(When illuminated from the upper left direction in the figure)
FIG. 6B shows the shading value of the pixel after shading removal stored in the memory 1 of FIG. 6 and the shading stored in the memory 2 when illuminated by the lamp 12 (in the figure, when illuminated from the upper right direction). FIG. 6C shows the gray value of the pixel after the removal. In the case of something printed on a flat surface, depending on the direction of illumination, the printed content (in this case,
The difference between the images stored in the memory is small (FIG. 6 (d)) because there is no change in the density distribution with respect to the position of the fingerprint ridge pattern).

As shown in FIG. 6 (e), a fingerprint having three-dimensional irregularities (the figure schematically shows a cross section of the fingerprint)
FIG. 6F shows the gray value of the pixel after shading removal stored in the memory 1 when illuminated by the lamp 11 (in the figure, when illuminated from the upper left direction).
(When illuminated from the upper right direction in the figure)
The gray value of the pixel after shading removal stored in the memory 2 is shown in FIG. 6 (g). In the case of a three-dimensional unevenness, the brightest illuminated position differs depending on the illuminating direction. Then, when the difference between the images stored in the memory in which the illumination direction is changed is taken, a component corresponding to the displacement remains. Therefore, it is possible to distinguish whether the input image is printed on a flat surface or three-dimensionally uneven, that is, a living body.

If d ₁ ≦ Q ₁ , the lamp lighting device 34
Turns on the lamp 13 to illuminate the fingerprint surface. Next, a fingerprint image is captured by the imaging device 31. The image data in the imaging device 31 is transferred to and stored in a specific memory area of the storage device 33 (this is referred to as a memory 3) via the central control device 32. The lamp lighting device 34 detects that the transfer is completed, and turns off the lamp 13. Next, the lamp lighting device 34 turns on the lamp 14 to illuminate the fingerprint surface. Next, a fingerprint image is captured by the imaging device 31. The image data in the imaging device 31 is transferred to a specific memory area of the storage device 33 (this is referred to as a memory 4) via the central control device 32 and stored therein. The lamp lighting device 34 detects a signal indicating that the transfer has been completed, and turns off the lamp 14.

Next, the shading of the image in the memory 3 is removed. Let the gray value of the pixel at the position (x, y) after shading removal be p ₃ (x, y). Next, the shading of the image in the memory 4 is removed. The gray value of the pixel at the position (x, y) after shading removal is p ₄
(X, y). In an area 62 shown in FIG. 5, the accumulation d of the square of the difference of each pixel between the images in the memories 3 and 4 is obtained.
₂ is obtained according to the following equation.

[0020]

(Equation 3)

If d ₂ > Q ₂ or d ₁ + d ₂ > Q ₁₂ , since the input fingerprint image is of a living body, the image data stored in the memory 3 and the memory 4 is stored in the central controller. Via the external output terminal 32, the data is output to a feature extracting unit or the like of an ordinary fingerprint matching device. In other cases, it is highly probable that the input is printed on a flat surface, so that rejection processing is performed.

FIG. 7 shows an outline of a threshold for determining whether or not a fingerprint is a living body. In the figure, a hatched portion is a region recognized as a fingerprint of a living body. The values of Q ₁ , Q ₂ , and Q ₁₂ are determined through experiments. The processing procedure shown here is an example. For example, the processing of S809 is executed after the processing of S804, the processing of S810 is executed after the processing of S808, and the processing of S821 is executed after the processing of S816. Run and S
It is also conceivable to execute the process of S822 following the process of 820. Further, when the d _1> Q _1, and the input fingerprint image has been found to be of biological in S812, S8
It is also conceivable that the processing of 13 to S822 is also performed, and the image data stored in the memories 1 to 4 is output to the outside.

In order to increase the accuracy of the determination, the shading removal is performed on the image obtained by taking the square of the difference between the images in the memory 1 and the memory 2 instead of the processing in S811. A process for setting the accumulated value to d ₁ is performed, and the same determination is made thereafter. Also, instead of the processing in S824, the shading removal is performed on an image obtained by taking the square of the difference between the images in the memories 3 and 4, and the accumulation of the image in the area 62 is set to d _2. And the same determination is made hereinafter.

FIG. 8 shows another embodiment of the present invention.
2A is a plan view, and FIG. 1B is a side view. In this embodiment, the number of times that the illuminating device takes a fingerprint image at a specific rotation angle is four times, that is, the rotation angle is 0 °, 90 °.
°, 180 °, and 270 °. The thus configured fingerprint input device includes a lamp 2 for illuminating a fingerprint surface.
1, a support rod 22 for supporting the lamp 21, and a support rod 22
24, a driving device 23 for rotating the shaft 24 clockwise, a lens 26 for focusing on an assumed fingerprint position, a CCD 25 for capturing a fingerprint image, and a cylinder 27 for supporting the lens 26 and the CCD 25. And

FIG. 9 shows the connection state of each component. An imaging device 41 (CCD 25, lens 26) for taking a fingerprint image
), A storage device 43 for storing a fingerprint image captured by the imaging device 41, a lamp lighting device 44 (including the lamp 21) for lighting a lamp illuminating the fingerprint surface, and a central axis of the imaging system. Drive 45 for rotating the lamp in the center
(Including the support rod 22, the driving device 23, and the shaft 24) and a central control device 42 for controlling the entire system.

The input operation is shown in FIG. 10 and FIG. Hereinafter, the input operation will be described in detail. First, the central control device 42 detects a signal indicating the start of image input, and operates the lamp lighting device 44 to turn on the lamp 21 and illuminate the fingerprint surface. At the same time, the driving device 45 rotates the shaft. ,
Rotate around the central axis of the lamp photography system. When the driving device starts rotating, the driving device rotates at a constant speed until it stops. Here, the rotation angle is initially at a position counterclockwise from 0 °, and the angle is measured clockwise with the tip direction of the finger being 0 °.

When the driving device 45 rotates the shaft and the rotation angle becomes 0 °, a fingerprint image is captured by the imaging device 41. The image data in the imaging device 41 is transferred to a specific memory area of the storage device 43 (this is referred to as a memory 1) via the central control device 42 and stored therein. Next, when the rotation angle becomes 90 °, a fingerprint image is captured by the imaging device 41. The image data in the imaging device 41 is transferred to a specific memory area (hereinafter referred to as the memory 3) of the storage device 43 via the central control device 42.
It is memorized.

Next, when the rotation angle becomes 180 °, a fingerprint image is captured by the imaging device 41. The image data in the imaging device 41 is transmitted via the central control device 42
The data is transferred to a specific memory area of the storage device 43 (this is referred to as a memory 2) and stored. Next, when the rotation angle is 27
When the angle reaches 0 °, a fingerprint image is captured by the imaging device 41. The image data in the imaging device 41 is transferred to a specific memory area of the storage device 43 (this is referred to as a memory 4) via the central control device 42 and stored therein. The end of this transfer is detected by the lamp lighting device 44, and the lamp 21 is turned off. Further, the driving device 45 also stops. Thereafter, similarly to the above-described first embodiment, the shading removal of the image of the memory 1 and the shading removal of the image of the memory 2 are performed, and in the area 61 shown in FIG. determining cumulative d ₁ of the squares of the difference.

If d ₁ > Q ₁ , since the input fingerprint image is of a living body, the image data stored in the memory 1 and the memory 2 is transmitted to the external output terminal via the central controller 42. Is output to the feature extraction unit of the fingerprint collation device. If d ₁ ≦ Q ₁ , the shading removal of the image in the memory 3 and the shading removal of the image in the memory 4 are performed, and in the area shown in FIG.
Determining cumulative d ₂ of the squares of differences between the pixels between the images.

If d ₂ > Q ₂ or d ₁ + d ₂ > Q ₁₂ , since the input fingerprint image is of a living body, the image data stored in the memory 3 and the memory 4 are stored in the central control unit. Via an external output terminal 42, the data is output to a feature extracting unit or the like of a normal fingerprint matching device. In other cases, it is highly probable that the input is printed on a flat surface, so that rejection processing is performed.

The processing procedure shown here is an example. For example, if the processing of shading removal can be executed at a high speed and the processing can be completed while the rotation angle of the driving device advances by 90 °, the processing in S905 is executed. During the processing of S906, S9
17 is performed, the process of S921 is performed between the processes of S908 and S909, the process of S918 is performed between the processes of S911 and S912, and the process of S922 is performed between the processes of S914 and S915. Then, processing can be performed at high speed without wasting time as a whole.

When d ₁ > Q ₁ in S 920, and it is determined that the input fingerprint image is of a living body, the image data stored in the memories 3 and 4 may be output to the outside. Conceivable.

In order to increase the accuracy of the judgment, the shading removal is performed on the image obtained by taking the square of the difference between the images in the memory 1 and the memory 2 instead of the processing in S919, and the image is stored in the area 61 of this image. A process for setting the accumulated value to d ₁ is performed, and the same determination is made thereafter. Further, instead of the processing in S923, the shading removal is performed on an image obtained by taking the square of the difference between the images in the memories 3 and 4, and the accumulation of the image in the area 62 is set to d _2. And the same determination is made hereinafter.

[0034]

According to the method of the present invention, it is possible to distinguish whether the inputted fingerprint image is a living body or a fake one such as a photograph. Therefore, the reliability of the fingerprint recognition device is improved.

[Brief description of the drawings]

FIG. 1 is a structural diagram of a main part of a fingerprint input device according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of the fingerprint input device according to the first embodiment of the present invention.

FIG. 3 is a diagram illustrating a flow of processing of the fingerprint input device according to the first embodiment of the present invention.

FIG. 4 is a diagram illustrating a flow of processing of the fingerprint input device according to the first embodiment of the present invention.

FIG. 5 is a diagram illustrating an area for calculating the cumulative value of the square of the difference between images.

FIG. 6 is a diagram illustrating the principle of a fingerprint input device according to the present invention.

FIG. 7 is a diagram illustrating an area for determining a fingerprint of a living body.

FIG. 8 is a structural diagram of a fingerprint input device according to a second embodiment of the present invention.

FIG. 9 is a configuration diagram of a fingerprint input device according to a second embodiment of the present invention.

FIG. 10 is a diagram illustrating the flow of processing of the fingerprint input device according to the second embodiment of the present invention.

FIG. 11 is a diagram illustrating the flow of processing of the fingerprint input device according to the second embodiment of the present invention.

[Explanation of symbols]

 11, 12, 13, 14 lamp 15 CCD 16 lens 17 cylinder 18 support base 31 imaging device 32 central control device 33 storage device 34 lamp lighting device

Claims (2)

(57) [Claims] 1. A photographing means having a first lighting position and a second lighting position of a light source opposed to each other with a photographing target finger interposed therebetween, and a photographing device in which the light source is turned on at the first lighting position to photograph. Storage means for storing a first fingerprint image and a second fingerprint image photographed by turning on a light source at the second lighting position; a first fingerprint image and a second fingerprint image stored in the storage means And a three-dimensional object discriminating means for discriminating whether or not the subject finger is a three-dimensional object based on the above. 2. A first lighting position and a second lighting position of a light source opposed to each other across a subject finger, and a third lighting position and a fourth lighting position of a light source opposed to each other across the subject finger. A first fingerprint image photographed by lighting the light source at the first lighting position, and a second fingerprint image photographed by lighting the light source at the second lighting position. Storage means for storing a third fingerprint image captured by lighting the light source at the third lighting position and a fourth fingerprint image captured by lighting the light source at the fourth lighting position; And the accumulated d1 of the square of the difference between each pixel of the first fingerprint image and the second fingerprint image stored in the storage unit, and each pixel of the third fingerprint image and the fourth fingerprint image stored in the storage unit , And the cumulative d1 and the cumulative d
And the sum d1 + d2 is obtained when the accumulated d1 is larger than a first predetermined value, when the accumulated d2 is larger than a second predetermined value, or when the sum d1 + d2 is larger than a third predetermined value. Further comprising a three-dimensional object discriminating means for discriminating that the subject finger is a three-dimensional object.