JPH04277874A - Fingerprint input device - Google Patents

Abstract

PURPOSE:To prevent an erroneous input caused by an artificially prepared fingerprint picture and to obtain the fingerprint input device with high reliability by judging whether an inputted picture is the fingerprint of a three-dimensionally uneven organ or not. CONSTITUTION:An image pickup means 31 is equipped with the first and second turn-on positions of light sources 11 and 12 and light sources 13 and 14 which are faced each other with an objective finger to be photographed between. At this first turn-on position, the light sources 11 and 12 are turned on and the first fingerprint picture is photographed. At the second turn-on position, the light sources 13 and 14 are turned on, and the second fingerprint picture is photographed and stored in a storing means 33. Thus, based on the first and second fingerprint pictures stored in the storing means 33, a solid discriminating means discriminates whether the objective finger to be photographed is a solid or not. Therefore, since it can be distinguished whether the inputted picture is the organ or the artificial object such as a picture or the like, the reliability of a fingerprint recognizing means is improved.

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 verification or verification identification.

0002

2. Description of the Related Art Conventionally, as a fingerprint input device used for fingerprint verification, a method has been considered in which the fingerprint surface is directly input as a two-dimensional image in a non-contact manner. This includes a finger guide that guides the finger on which a fingerprint pattern is to be input to a predetermined position, and an opening window in the finger guide that corresponds to the assumed position of the fingerprint surface, and is arranged to focus on the assumed position of the fingerprint surface. In a fingerprint input device equipped with a two-dimensional image sensor and a light source that illuminates the assumed position of the fingerprint surface, inserting a finger along a finger guide, and activating an imaging switch with the top of the finger's head using the inserted finger; Activate the two-dimensional image sensor and light source,
This is a method that directly images the fingerprint surface.

0003

[Problem to be Solved by the Invention] When inputting a fingerprint image using the above-mentioned fingerprint input device, for example, even if a photograph of a finger print is pasted on the finger and input into the input device,
Since the fingerprint is input in the same way as a biological fingerprint, there is a problem in that the reliability of the fingerprint verification device decreases.

[0004] Therefore, an object of the present invention is to prevent erroneous input due to artificially created fingerprint images and improve reliability by determining whether or not the input image is a three-dimensionally uneven fingerprint of a biological body. The purpose of the present invention is to provide a high quality fingerprint input device.

[0005]

[Means for Solving the Problems] A first feature of the fingerprint input device according to the present invention for achieving the above-mentioned object is that the first lighting position of the light source and the first lighting position of the light sources are opposite to each other with the target finger to be photographed sandwiched therebetween. a first fingerprint image taken with the light source turned on at the first lighting position; and a second fingerprint image taken with the light source turned on at the second lighting position; and a three-dimensional object determining means for determining whether or not the target finger to be photographed is a three-dimensional object based on the first fingerprint image and the second fingerprint image stored in the storage means. The point is to be prepared.

Furthermore, a second fingerprint input device according to the present invention
is characterized by a first lighting position and a second lighting position of the light sources facing each other with the target finger to be photographed in between, and a third lighting position and a fourth lighting position of the light sources facing each other with the target finger in between.
a first fingerprint image photographed with the light source turned on at the first lighting position and the second fingerprint image;
a second fingerprint image taken with the light source turned on at the lighting position, a third fingerprint image taken with the light source turned on at the third lighting position, and a third fingerprint image taken with the light source turned on at the fourth lighting position. a fourth fingerprint image stored in the storage means; an accumulation d1 of the square difference of each pixel between the first fingerprint image and the second fingerprint image stored in the storage means; an accumulation d2 of the square difference of each pixel between the third fingerprint image and the fourth fingerprint image, and the sum d of the accumulation d1 and the accumulation d2;
1+d2, and if the cumulative value d1 is larger than a first predetermined value, or if the cumulative value d2 is larger than a second predetermined value, or if the sum d1+d2 is larger than a third predetermined value, the object to be photographed is determined. The present invention is provided with a three-dimensional object discriminating means for determining that a finger is a three-dimensional object.

[0007]

[Operation] In the fingerprint input device having the first feature,
The photographing means has a first lighting position and a second lighting position of a light source that face each other with the finger to be photographed interposed therebetween. This first
Turn on the light source at the lighting position and take a first fingerprint image,
Further, the light source is turned on at the second lighting position, and a second fingerprint image is taken and stored in the storage means. Based on the first fingerprint image and the second fingerprint image stored in the storage means, the three-dimensional object determining means determines whether or not the target finger to be photographed is a three-dimensional object.

[0008] In the fingerprint input device having the second feature, the photographing means is arranged at the first lighting position and the second lighting position of the light sources, which are opposite to each other with the finger to be photographed in between, and to each other with the finger to be photographed in between. The third lighting position and the fourth lighting position of the opposing light sources
It has a lighting position. The light source is turned on at the first lighting position to take a first fingerprint image, the light source is turned on at the second lighting position to take a second fingerprint image, and the light source is turned on at the third lighting position. to take a third fingerprint image, and then take a fourth fingerprint image.
The light source is turned on at the lighting position, and a fourth fingerprint image is photographed and stored in the storage means. The cumulative sum d1 of the square of the difference between each pixel between the first fingerprint image and the second fingerprint image stored in the storage means, and the square of the difference between each pixel between the third fingerprint image and the fourth fingerprint image. and the sum d1+d2 of the cumulative d1 and the cumulative d2, and if the cumulative d1 is larger than the first predetermined value, or if the cumulative d2 is larger than the second predetermined value, or if the sum d1+d2 is the third predetermined value, If it is larger than a predetermined value, it is determined that the finger to be photographed is a three-dimensional object.

[0009]

[Embodiments] Examples of the invention will be described below. Figure 1(a)
, (b) show an embodiment of claim 1 of the present invention. FIG. 4(a) is a plan view, and FIG. 2(b) is a side view. In this embodiment, two pairs of lighting devices are used. The fingerprint input device configured as shown in FIG. 1 includes a pair of lamps 11 and 12 that illuminate the fingerprint surface from opposing positions across the central axis of the imaging system, and is arranged in a direction perpendicular to the lamps 11 and 12. A pair of lamps 13 and 14 illuminate the fingerprint surface from opposing positions across the central axis of the photographing system, a CCD 15 for taking a fingerprint image, and a lens 16 for focusing on the expected position of the fingerprint. , lens 16 and CCD 15
and a support stand 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) that captures a fingerprint image.
), a storage device 33 that stores the fingerprint image captured by the imaging device, a lighting device 34 (including the lamps 11 to 14) that sequentially turns on the lamps that illuminate the fingerprint surface, and controls the entire system. It consists of a central control device 32. Here, the input image has a resolution of 512 pixels vertically and 512 pixels horizontally, and is sized to just fit the part up to the first joint of the finger. 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. 3 and 4. less than,
The input operation will be explained in detail. First, the central controller 32 detects a signal indicating the start of image input, operates the lamp lighting device 34, and lights the lamp 11 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 sent to the central control device 32.
is transferred to a specific memory area of the storage device 33 (this will be referred to as memory 1) and stored therein. 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 captured by the imaging device 31.
Photographed by. Image data in the imaging device 31 is transferred to a specific memory area (this will be referred to as memory 2) of the storage device 33 via the central control device 32 and stored therein. The lamp lighting device 34 detects that the transfer has been completed,
Turn off the lamp 12. Next, the shading of the image in memory 1 is removed according to the following equation.

0012

[Math 1]

Here, p(x, y) is the gray value of the pixel at the position (x, y) before shading removal, p1(x
, y) is the gray value of the pixel at the position (x, y) after shading is removed, and N=16. Similarly,
Remove shading from the image in memory 2. Let p2 (x, y) be the gray value of the pixel at the position (x, y) after shading is removed. In the area 61 shown in FIG. 5, the cumulative sum d1 of the square difference of each pixel between the images in memory 1 and memory 2 is determined according to the following equation.

[0014]

[Math 2]

In FIG. 5, w=512, h=512,
dw=50, dh=50, sw1=50, sw2=50
, sh1=50, sh2=50. If d1>Q
If 1, the input fingerprint image is a biological one, so
The image data stored in the memory 1 and the memory 2 is outputted from an external output terminal to a feature extraction unit or the like of a normal fingerprint verification device via the central control unit 32. If d1≦Q
If it is 1, proceed to the next process.

The principle of determining whether an input image is of a living body or not will be described in detail below. As shown in Figure 6(a), a fingerprint image with shading (the figure is
A cross-sectional view of something printed on a flat surface) is shown in the lamp 11.
(In the figure, when illuminated from the upper left direction)
Figure 6(b) shows the shading value of the pixel after shading removal stored in memory 1, and the shading stored in memory 2 when illuminated with lamp 12 (in the figure, illumination is from the upper right direction). The grayscale values of the pixels after removal are shown in FIG. 6(c). In the case of something printed on a flat surface, the density distribution of the printed content (in this case, the fingerprint ridge pattern) will not change depending on the direction of illumination, so the image stored in the memory will not change depending on the direction of illumination. The difference between them is small (Fig. 6(d)).

As shown in FIG. 6(e), when a three-dimensionally uneven fingerprint (the figure is a diagram schematically depicting a cross section of the fingerprint) is illuminated with the lamp 11 (in the figure, the upper left direction Figure 6(f) shows the pixel density values after shading removed that are stored in memory 1 when the lamp was illuminated from the lamp 12 (in the figure, when the lamp was illuminated from the upper right). (Figure 6 (g) shows the stored grayscale values of pixels after removing shading) In the case of three-dimensionally uneven objects, the brightest illuminated position differs depending on the direction of illumination. If we take the difference between the images stored in the memory with different values, a component corresponding to the positional shift remains. Therefore, it is possible to distinguish whether the input image is a flat image printed on a flat surface or a three-dimensionally uneven image, that is, a biological image.

If d1≦Q1, the lamp lighting device 3
4 turns on the lamp 13 to illuminate the fingerprint surface. Next, a fingerprint image is captured by the imaging device 31. Image data in the imaging device 31 is transferred to a specific memory area (this will be referred to as memory 3) of the storage device 33 via the central control device 32 and stored therein. 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. Image data in the imaging device 31 is transferred to a specific memory area (this will be referred to as memory 4) of the storage device 33 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 p3 (x, y) be the gray value of the pixel at the position (x, y) after shading is removed. 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 is removed is p4
Let it be (x, y). In the area 62 shown in FIG.
2 is calculated according to the following formula.

[0020]

[Math 3]

[0021] If d2>Q2 or d1+d2>Q1
If 2, the input fingerprint image is a biological one, so
The image data stored in the memory 3 and the memory 4 is outputted from an external output terminal to a feature extraction unit or the like of a normal fingerprint verification device via the central control unit 32. In any other case, there is a high possibility that the inputted item was printed on a flat surface, so a reject process is performed.

FIG. 7 shows an outline of the threshold values for determining whether or not a fingerprint is a biological fingerprint. In the figure, the shaded area is an area recognized as a biological fingerprint. The values of Q1, Q2, and Q12 are determined through experiments. The processing procedure shown here is an example, and for example, the process of S809 is executed after the process of S804, the process of S810 is executed after the process of S808, and the process of S821 is executed after the process of S816. It is also conceivable to execute the process in S822 after the process in S820. In addition, when d1>Q1 in S812 and the input fingerprint image is found to be that of a biological body, the processing in S813 to S822 is also performed, and the image data stored in memories 1 to 4 is output to the outside. It is also possible to do so.

In order to improve the accuracy of the determination, instead of the process in S811, the shading is removed from the image obtained by taking the square of the difference between the images in memory 1 and memory 2, and the area 61 of this image is A process is performed in which the cumulative value obtained is set as d1, and the same determination is made thereafter. Also, instead of the process in S824, the shading is removed from the image obtained by taking the square of the difference between the images in the memory 3 and the memory 4, and the accumulation in the area 62 of this image is set as d2. The same determination is made thereafter.

FIG. 8 shows another embodiment of the invention. FIG. 4(a) is a plan view, and FIG. 2(b) is a side view. In this example, the number of times the fingerprint image is captured when the illumination device is at a specific rotation angle is 4 times, that is, the rotation angle is 0°, 90°,
°, 180°, and 270°. The fingerprint input device configured in this way includes a lamp 2 that illuminates the fingerprint surface.
1, a support rod 22 that supports the lamp 21, and a support rod 22
A shaft 24 that fixes the shaft 24, a drive device 23 that rotates the shaft 24 clockwise, a lens 26 that focuses on the expected fingerprint position, a CCD 25 that takes a fingerprint image, and a cylinder 27 that supports the lens 26 and the CCD 25. Equipped with.

FIG. 9 shows the connection state of each component. An imaging device 41 (CCD 25, lens 26) that captures a fingerprint image.
), a storage device 43 that stores the fingerprint image captured by the imaging device 41, a lamp lighting device 44 (including the lamp 21) that lights a lamp to illuminate the fingerprint surface, and a central axis of the imaging system. A drive device 45 (
(including a support rod 22, a drive device 23, and a shaft 24), and a central control device 42 that controls the entire system.

The input operation is shown in FIGS. 10 and 11. The input operation will be described in detail below. First, the central controller 42 detects a signal indicating the start of image input, operates the lamp lighting device 44, lights up the lamp 21, and illuminates the fingerprint surface.At the same time, the drive device 45 rotates the shaft. ,
Rotate around the central axis of the lamp photography system. It is assumed that once the drive device starts rotating, it 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 direction of the tip of the finger as 0°.

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

Next, when the rotation angle reaches 180°, a fingerprint image is captured by the imaging device 41. The image data in the imaging device 41 is sent via the central control device 42.
The data is transferred to and stored in a specific memory area of the storage device 43 (this will be referred to as memory 2). Next, the rotation angle is 27
When the angle reaches 0°, a fingerprint image is captured by the imaging device 41. Image data in the imaging device 41 is transferred to a specific memory area (this will be referred to as memory 4) of the storage device 43 via the central control device 42 and stored therein. The lamp lighting device 44 detects the completion of this transfer and turns off the lamp 21. Further, the drive device 45 also stops. Thereafter, as in the first embodiment described above, shading is removed from the image in memory 1 and shading is removed from the image in memory 2, and each pixel between the images in memory 1 and memory 2 is Find the cumulative sum d1 of the squared difference.

If d1>Q1, the input fingerprint image is that of a living body, so the image data stored in memory 1 and memory 2 is transferred via the central controller 42.
It is output from the external output terminal to the feature extraction unit of the fingerprint matching device. If d1≦Q1, shading is removed from the image in memory 3 and shading is removed from the image in memory 4, and in the area shown in FIG. seek.

If d2>Q2 or d1+d2>Q1
If 2, the input fingerprint image is a biological one, so
The image data stored in the memory 3 and the memory 4 is outputted from an external output terminal to a feature extraction unit or the like of a normal fingerprint verification device via the central control device 42. In any other case, there is a high possibility that the inputted item was printed on a flat surface, so a reject process is performed.

The processing procedure shown here is an example; for example, if the shading removal processing can be executed at high speed and can be completed while the rotation angle of the drive device advances by 90 degrees, S905 and During the process of S906, S91
7 is executed, and S is executed between S908 and S909.
If the process of S921 is executed, the process of S918 is executed between the processes of S911 and S912, and the process of S922 is executed between the processes of S914 and S915, the overall process can be performed at high speed without wasting time. Can be done.

[0032] Furthermore, when d1>Q1 in S920 and it is determined that the input fingerprint image is that of a living body, the image data stored in memory 3 and memory 4 may also be output to the outside. .

In order to improve the accuracy of the determination, instead of the process in S919, the shading is removed from the image obtained by taking the square of the difference between the images in memory 1 and memory 2, and the area 61 of this image is A process is performed in which the cumulative value obtained is set as d1, and the same determination is made thereafter. Also, instead of the process in S923, the shading is removed from the image obtained by taking the square of the difference between the images in the memory 3 and the memory 4, and the accumulation in the area 62 of this image is set as d2. The same determination is made thereafter.

[0034]

[Effects of the Invention] According to the method of the present invention, it is possible to distinguish whether an input fingerprint image is a biological image or a fake image such as a photograph. Therefore, the reliability of the fingerprint recognition device is improved.

[Brief explanation of the drawing]

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

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

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

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

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

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

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

[Explanation of symbols]

11, 12, 13, 14 lamp 15 CCD 16 Lens 17 tube 18 Support stand 31 Imaging device 32 Central control unit 33 Storage device 34 Lamp lighting device

Claims (2)

[Claims] 1. Photographing means having a first lighting position and a second lighting position of a light source facing each other with a target finger to be photographed in between; storage means for storing a first fingerprint image and a second fingerprint image photographed with a light source turned on at the second lighting position; and a first fingerprint image and a second fingerprint image stored in the storage means. 1. A fingerprint input device comprising: a three-dimensional object determining means for determining whether or not a finger to be photographed is a three-dimensional object based on the following. 2. A first lighting position and a second lighting position of the light sources facing each other across the finger to be photographed, and a lighting position and a fourth lighting position of the light sources facing each other with the finger to be photographed sandwiched therebetween. a first fingerprint image taken with the light source turned on at the first lighting position; a second fingerprint image taken with the light source turned on at the second lighting position; and the third fingerprint image taken with the light source turned on at the second lighting position. a storage means for storing a third fingerprint image taken with the light source turned on at the lighting position and a fourth fingerprint image taken with the light source turned on at the fourth lighting position; the cumulative sum d1 of the square of the difference between each pixel between the first fingerprint image and the second fingerprint image, and the difference between each pixel between the third fingerprint image and the fourth fingerprint image stored in the storage means; The sum d1+ of the squared cumulative d2 and the cumulative d1 and the cumulative d2
d2, and if the cumulative value d1 is larger than a first predetermined value, or if the cumulative value d2 is larger than a second predetermined value, or if the sum d1+d2 is larger than a third predetermined value, the object to be photographed is determined. A fingerprint input device comprising a three-dimensional object discriminating means for determining that a finger is a three-dimensional object.