JPH10293844A - Reference frame setting method for fingerprint matching device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To always secure the accurate collation of fingerprints by setting a reference frame based on the center of a finger shape. SOLUTION: When an operator touches his finger on a fingerprint taking surface 11a, the light emitted from a light source 12 enters a prism 11 and then reflected by the fingerprint set on the surface 11a. This reflected light is emitted from the prism 11, transmitted through a lens group 13 and made incident on a photoelectric transducer 14. The image signals which undergone the photoelectric conversion via the element 14 are recorded in a memory 16. The image signals read out of the memory 16 are processed at a fingerprint image processing part 17, and a reference frame is acquired. Thus, the part 17 binarizes the image signals received from the transducer 14 to calculate the center of a finger shape and acquires the reference frame based on the finger shape center. As a result, the reference frame is set in response to the center of the finger shape, i.e., the center of a fingerprint even though the finger putting position is shifted on the surface 11a of the prism 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a surface for contacting a fingerprint, and optically reads an image of the fingerprint in contact with the surface to collate it with fingerprint data registered in advance. The present invention relates to a fingerprint matching device, and more particularly to a method for obtaining a reference frame when reading fingerprint data.

[0002]

2. Description of the Related Art In recent years, information processing technology has been applied to society as a whole, and with the spread of information processing technology, it has become necessary to manage various systems and to ensure safety. At present, in the information processing field, input of personal identification number, magnetic card
It is a common practice to identify each individual using an IC card or the like. In addition, in the personal living environment, applications of these information processing technologies are also attracting attention for ensuring the security of keys of houses and automobiles, keys of lockers, and the like. This is because it is impossible to avoid the dangers of forgetting the personal identification number and losing, stolen, forgery, and the like of the key, the magnetic card, the IC card, and the like using the conventional method. Therefore, as a method for avoiding these dangers, it is advantageous to secure the system management and the security by identifying the individual by fingerprint collation using the unique and invariant fingerprint of the individual. It is.

Conventionally, such a fingerprint matching device is configured as shown in FIG. 5, for example. In FIG. 4, a fingerprint collation device includes a prism 1 having a fingerprint collection surface 1 a, a light source 2 disposed on one side (a lower surface in the illustrated case) of the prism 1, and a prism (a lower surface of FIG. Lens group 3 and CCD arranged on the right side
A fingerprint reading sensor 5 including a photoelectric conversion element (imaging means) 4 such as a charge-coupled device, and an image signal from the photoelectric conversion element 4 are processed into fingerprint image data for collation. And a fingerprint image data processing unit 6 for comparing fingerprint data with reference fingerprint image data registered in advance to perform fingerprint collation.

In the fingerprint collating apparatus having such a configuration, when an operator touches a finger on the fingerprint collecting surface 1a, light emitted from the light source 2 enters the prism 1 and the fingerprint on the fingerprint collecting surface 1a. Reflected by This reflected light exits from the prism 1, passes through the lens group 3, and enters the photoelectric conversion element 4. Then, it is photoelectrically converted by the photoelectric conversion element 4, and is taken in as fingerprint image data for collation by the fingerprint image data processing unit 6. Further, the fingerprint image data processing unit 6 compares the fingerprint image data for collation with the fingerprint image data for reference registered in advance, and performs fingerprint collation.

Here, since only the convex portion of the fingerprint comes into contact with the fingerprint collecting surface 1a, incident light is not totally reflected but irregularly reflected at this convex portion. Therefore, in the photoelectric conversion element 4,
The portion corresponding to the convex portion is identified as a dark portion, and the portion corresponding to the concave portion is identified as a bright portion.

[0006]

However, in such a fingerprint collating apparatus, the fingerprint image data processing section 6
When the image signal from the photoelectric conversion element 4 is captured as fingerprint image data for collation, the tip of the finger is substantially moved along the center line of the screen (extending in the longitudinal direction of the finger) with respect to the read image signal. A search target area (hereinafter, referred to as a “reference frame”) of fingerprint image data is set based on the relative position from the leading end, and an image signal is compared with the fingerprint image data for comparison based on the reference frame. I try to capture as.

[0007] Therefore, when the finger placement on the fingerprint collection surface 1a is displaced in the longitudinal direction of the finger, the reference frame is accurately acquired following the displacement of the finger. However, if the finger placement on the fingerprint collection surface 1a is shifted laterally with respect to the longitudinal direction of the finger, the tip of the finger is shifted from the center line in the longitudinal direction, and this shifted position is searched for as the tip of the finger. Would be. As a result, the center of the collation frame deviates from the center of the fingerprint of the finger, and the fingerprint image data for collation obtained by the fingerprint image data processing unit 6 varies even for the same fingerprint. Become. For this reason, when this variation increases, the fingerprint image data for collation becomes different from the fingerprint image data for reference, and a similar fingerprint is erroneously recognized as the same fingerprint during fingerprint collation. In addition, there is a problem that accurate fingerprint collation cannot be performed, for example, the same fingerprint cannot be recognized as the same fingerprint.

On the other hand, a method of directly calculating the center of gravity of the image signal from the imaging means to obtain the center of the shape of the finger and setting a reference frame based on this center is also conceivable. The signal is generally an image signal of, for example, 256 gradations, and it takes too much time to calculate the center of gravity, and the effect of the fingerprint cannot be removed. There was a problem that the center could not be found.

SUMMARY OF THE INVENTION In view of the above, it is an object of the present invention to provide a reference frame setting method for a fingerprint matching device which ensures that fingerprint matching is performed even if the finger placement position is shifted.

[0010]

According to the present invention, there is provided a first step of binarizing image data by an image pickup means to obtain shape data of a finger to be subjected to fingerprint collation; A fingerprint matching device comprising: a second step of obtaining center data of a finger shape based on data; and a third step of setting a reference frame based on a screen coordinate position based on the center data of the finger shape. Is achieved by the reference frame setting method.

The first step of obtaining the finger shape data is to obtain first mesh data in which gradation is averaged for each m × m dot of the image data, and obtain the first mesh data. May be performed by obtaining the second mesh data by taking the central gradation for every n × n dots.

According to the above configuration, at the time of acquiring the reference frame, the finger shape data is obtained by binarization in the first stage based on the image signal of the image sensor, and in the second stage By detecting the center, in a third stage, a reference frame is set based on the center of the shape of the finger. Therefore, even if the finger placement position on the fingerprint collection surface is deviated from the center line, the reference frame is set based on the center of the finger shape, so that fingerprint image data for accurate collation can be obtained, and the accurate Fingerprint collation will be performed.

The binarization of the image data is performed by converting the first mesh data into one first mesh data in which the gradation is averaged for each m × m (m is a positive integer) dot of the image data. When the center gradation is taken for every n × n (n is a positive integer) dot and the second mesh data is used, the data related to the fingerprint of the image data is removed. Data on the shape of the finger is obtained.
Therefore, an accurate reference frame is set, and more accurate fingerprint collation is performed.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to FIGS. still,
Since the embodiments described below are preferred embodiments of the present invention, various technically preferred limitations are given. However, the scope of the present invention is described in the following description to particularly limit the present invention. However, the present invention is not limited to these embodiments unless otherwise described.

FIG. 1 shows an example of a fingerprint matching apparatus for executing a reference frame setting method according to the present invention. In FIG. 1, a fingerprint collation device 10 includes a prism 11 having a fingerprint collecting surface 11a, a light source 12 disposed on one side of the prism 11, and a lens group 13 disposed on the other side of the prism 11. And CCD (charge coupled device)
A fingerprint reading sensor 15 including a photoelectric conversion element (imaging means) 14, a memory 16 for storing a fingerprint image from the photoelectric conversion element 14, a fingerprint image read from the memory 16, and a fingerprint for collation A fingerprint image data processing unit 17 is provided for comparing the fingerprint image data for collation with the reference fingerprint image data registered in the memory 16 in advance, and performing fingerprint collation.

The fingerprint image data processing section 17 is configured to set a reference frame as follows. First, the fingerprint image data processing unit 17 removes a fingerprint from an image signal in the first stage as follows,
Get data about finger shape. Specifically, FIG.
As shown in (A), the image signal obtained from the photoelectric conversion element 14 is, for example, an image signal composed of a plurality of dots arranged in the x direction and the y direction of 256 gradations. As shown in FIG. 2 (B), the fingerprint image data processing unit 17 averages the gradation of each of the m × m dot unit regions P, where m is a positive integer, as shown in FIG. , One set of first mesh data Dm1. By performing this processing on the entire image signal, the entire image signal is represented by the first mesh data Dm having a smaller number of data.

Subsequently, as shown in FIGS. 3A and 3B, the fingerprint image data processing section 17 sets n to be a positive integer and n × n for the first mesh data Dm.
For each region Q in dot units (for example, 3 × 3 dot units),
Data of each dot (that is, first mesh data Dm1)
And rearranged in the order of low (or high) gradation as shown in FIG. Then, as shown in FIG. 3D, new data of the center dot of this area Q is assigned to the middle data (in this case, the fifth) of the rearranged data, as shown in FIG. That is, it is replaced as the second mesh data Dm2. Then, such replacement with the second mesh data Dm2 is performed for the area Q shifted by one dot. As a result, the data relating to the fingerprint corresponding to the extreme gradation is removed, and the data of the finger shape in the first stage is obtained.

Next, as described above, the fingerprint image data processing unit 17 removes the data relating to the fingerprint, thereby leaving only the shape of the finger.
The average value of the gradation of each dot of the entire image signal is calculated. Then, by comparing the gradation of each dot of the finger shape data with the above-mentioned average value, when the gradation value is higher than the average value, "1"
If it is low, it is set to "0" and binarized. This allows
A certain part of the finger will be represented by "1". Next, the fingerprint image data processing unit obtains the center O of the finger shape as follows. First, the fingerprint image data processing unit 17 sets coordinates in the x direction and the y direction.
Then, the fingerprint image data processing unit 17 adds the coordinate values for all of the binarized data represented by “1” and divides the sum by the number of data. In this way, the average value of the distance is calculated for each of the binarized data in which a certain part of the finger is represented by “1” in the two orthogonal directions. Thus, the center O of the shape of the finger is obtained as shown in FIG. 4C by the average value of the distances in the x direction and the y direction.

Finally, the fingerprint image data processing unit 17 converts the average value in the x direction and the y direction, that is, the center of the shape of the finger, into the coordinate position of the image signal, as shown in FIG. Then, a reference frame 18 of a predetermined size is set based on the center coordinate position.

The fingerprint collating apparatus 10 according to the present embodiment is configured as described above, and operates as follows when performing fingerprint collation. That is, as shown in FIG. 1, when the operator touches the finger on the fingerprint collecting surface 11a, the light source 1
Light emitted from 2 enters the prism 11 and is reflected by a fingerprint on the fingerprint collection surface 11a. This reflected light exits from the prism 11, passes through the lens group 13, and enters the photoelectric conversion element 14. As a result, the image signal photoelectrically converted by the photoelectric conversion element 14 is recorded in the memory 16.
Then, the image signal read from the memory 16 is processed by the fingerprint image data processing unit 16 as described above to obtain a reference frame. Accordingly, the fingerprint image data processing unit 17 reads the image signal from the memory 16 again, takes in the image signal as fingerprint image data for collation based on the reference frame, and records the image signal in the memory 16 in advance. The fingerprint is compared with the reference fingerprint image data.

Here, as described above, the fingerprint image data processing unit 17 binarizes the image signal from the photoelectric conversion element 14 to obtain the center of the finger shape, and based on the center of the finger shape. , To obtain a reference frame. Thus, even if the finger placement position of the prism 11 on the fingerprint collection surface 11a is shifted, a reference frame corresponding to the center of the finger shape, that is, the center of the fingerprint is set, and accurate fingerprint collation is always performed. Will be

Further, the binarization of the image data is performed by forming one first mesh data in which the gradation is averaged for each m × m dot of the image data, and n × n of the first mesh data.
If the center gradation is taken for each dot and the mesh data is used as the second mesh data, the data relating to the fingerprint of the image data is removed, and the data relating to the accurate finger shape is obtained. Therefore, an accurate reference frame is set, and more accurate fingerprint collation is performed.

In the above embodiment, the prism 11 is used as the prism having the fingerprint collecting surface 11a. However, the present invention is not limited to this, and it is obvious that the prism 11 may have another shape. .

[0024]

As described above, according to the present invention, it is possible to provide a reference frame setting method for a fingerprint collation device which ensures that fingerprint collation is performed even if the finger placement position is shifted. .

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration of an embodiment of a fingerprint matching device for executing a fingerprint frame setting method according to the present invention.

FIG. 2 is a schematic diagram illustrating generation of first mesh data in a fingerprint frame obtaining method in the fingerprint matching device of FIG. 1;

FIG. 3 is a schematic diagram showing generation of second mesh data in a fingerprint frame obtaining method in the fingerprint matching device of FIG. 1;

FIG. 4 is a schematic view showing a fingerprint frame obtaining method in the fingerprint matching device of FIG. 1;

FIG. 5 is a schematic diagram showing a configuration of an example of a conventional fingerprint matching device.

[Explanation of symbols]

10: fingerprint collation device, 11: prism, 11a
... Fingerprint sampling surface, 12 ... Light source, 13 ... Lens group, 14 ... Photoelectric conversion element, 15 ... Fingerprint reading sensor, 16 ... Memory, 17 ... Fingerprint image data processing Part, 18 ... reference frame, F ... finger (shape), O ...
-Center of finger shape, Dm1 ... first mesh data, Dm2 ... second mesh data.

Claims (2)

[Claims] 1. A first step of binarizing image data obtained by an imaging unit to obtain finger shape data to be subjected to fingerprint collation, and a step of obtaining center data of a finger shape based on the finger shape data. A reference frame setting method for a fingerprint matching device, comprising: two stages; and a third stage of setting a reference frame based on a screen coordinate position based on the center data of the finger shape. 2. The first step of obtaining the finger shape data is to obtain first mesh data in which gradation is averaged for every m × m dots of the image data. 2. A reference frame setting method for a fingerprint matching device according to claim 1, wherein the method is performed by obtaining a second mesh data by taking a central gradation for each of n × n dots.