JP2001184507A - Device for authenticating individual - Google Patents

Abstract

PROBLEM TO BE SOLVED: To acquire a finger image with high reproducibility and to improve the accuracy or individual authentication by the vein pattern of a finger based on suitable image processing and collating processing. SOLUTION: The finger image of an objecting person is acquired by a handle- shaped data acquiring part 2 and fetched through an input device 4 into an arithmetic unit 5. Concerning the finger image, directional filtering processing to become integration-like processing in the long-axis direction of a finger, which is the main running direction of a blood vessel, and to become differentiation-like processing in the orthogonal short-axis direction is applied and authentication is performed by comparing the image with the Registered finger image data of that person himself registered in a storage device 6. Thus, by making the objecting person grasp the handle-shaped data acquiring part having a curvature, the image data of plural fingers can be acquired with high reproducibility, further, a non-uniform background is removed from the finger image by directional filtering processing, an image intensifying a blood vessel image usable for the arithmetic of authentication can be provided and high- accuracy individual authentication is enabled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a personal authentication apparatus using a signature, a personal identification number or the like as an authentication means.

[0002]

2. Description of the Related Art Up to now, when using a credit card, depositing or withdrawing a bank account, a signature, a personal identification number, and the like are used as means for authenticating a person. As a new technology, the iris is beginning to be used for authentication.

[0003]

In performing personal authentication using a finger vein pattern, it is necessary to remove the background when acquiring an image of the finger vein pattern using transmitted light. The background to be considered here is a spatially intermediate frequency component in which the transmittance changes slowly in the long axis direction of the finger due to the high transmittance of light at the joints. Exists as a component of In the short-axis direction of the finger, blood vessels are spatially present as relatively high-frequency components, so in image processing using a filter with no directivity that is widely used in image processing,
It is not possible to obtain an image that emphasizes the running of blood vessels.

Further, it is necessary to obtain finger images with good reproducibility for the same person, and for individual fingers having different light characteristics, the light amount and focus of the light source are appropriately set.
It is necessary to capture an image.

[0005]

In order to remove the background from the finger image, the problem is solved by designing the filter for processing the image to have a direction. The direction from the base of the finger toward the distal end is defined as the long axis direction, and the direction perpendicular to the direction is defined as the short axis direction. Integral processing is performed in the major axis direction, which is the main running direction of the blood vessel, and processing is performed using a filter designed to perform differential processing in the minor axis direction, which is almost orthogonal to the blood vessel. . In a filter that does not have directionality, for example, a filter that performs differential processing on both the long axis and the short axis, blood vessels traveling in the long axis direction are also fragmented, and blood vessel images that can be used for authentication calculation processing are emphasized. I can't get an image.

In order to acquire a finger image with good reproducibility, it is necessary that no two-dimensional rotation or spatial rotation be applied to the finger during imaging. Therefore, the present invention includes means for acquiring an image with good reproducibility by utilizing the fact that the shape of a hand is almost uniquely determined when a plurality of fingers hold a door handle or the like. In order to control the rotation of the flat finger,
Using a data acquisition unit that has a curvature such as the shape of the door handle, restricting the finger mobility to translation by holding the data neck acquisition unit with multiple fingers and capturing images in order to suppress spatial finger rotation It is possible to This eliminates the need to perform data processing corresponding to the rotation of the finger, so that the load on data processing can be reduced and a finger image can be acquired with good reproducibility.

In order to separate artificial light or natural light such as light from a fluorescent lamp existing in an indoor environment from light from a light source, separation or modulation is performed in a wavelength range. For example, in the case of a fluorescent lamp having a wavelength range of about 400 to 800 nm, the wavelength of the transmitted light of the interference filter for imaging is selected at 800 nm or more so as not to overlap the wavelength range of the light source of the fluorescent lamp. Separation is possible. In the case of the modulation, for example, an environment light as a background can be removed by capturing an image at each timing of turning on and off the light source light and obtaining a difference between the images.

Further, by providing means for adjusting the light amount and focus of the light source to separate the artificial light from the light from the light source, a clearer blood vessel pattern image can be obtained.

[0009]

FIG. 1 is a block diagram showing a personal authentication apparatus according to an embodiment of the present invention. 1 is the hand of the person to be authenticated. In order to acquire a finger vein pattern with good reproducibility, a data acquisition unit 2 having a door handle shape is provided. Simultaneous acquisition of data for multiple fingers using the door handle shape data acquisition unit 2 that has a curvature enables to suppress planar rotation and spatial rotation of the fingers and to acquire images with good reproducibility. Becomes Vein pattern acquisition unit 2 for finger in handle shape
An image pickup device for picking up the transmitted light from the light source unit 3 is incorporated in the inside. The light source light reaches the image sensor after passing through the finger, and the video signal output therefrom is input to the input device 4.

In order to separate artificial light or natural light such as fluorescent light existing in an indoor environment from light from the light source 3,
Separation or modulation in the wavelength range is performed. For example, 400-800
In the case of fluorescent lamps with a wavelength range of about nm, separation can be achieved by selecting the wavelength of transmitted light of the interference filter for imaging at 800 nm or more so as not to overlap the wavelength range of the light source of the fluorescent lamp. is there. In the case of the modulation, for example, an environment light as a background can be removed by capturing an image at each timing of turning on and off the light source light and obtaining a difference between the images.

The input device 4 converts the signal from analog to digital, and the arithmetic unit 5 performs a filtering process.
Then, a process of collation with the finger image data of the individual stored in the storage device 6 is performed.

Next, the processing in the arithmetic unit 5 will be described. In the present embodiment, the finger image is processed by a filter for enhancing the blood vessel pattern of the finger, and the authentication is performed by the arithmetic processing of the entire image information without extracting the feature points of the image. To describe filtering in more detail, a direction from the base of each finger of the acquired image toward the tip is defined as a long axis direction, and a direction orthogonal to the long axis direction is defined as a short axis direction. Integral processing is performed in the major axis direction, which is the main running direction of the blood vessel, and processing is performed using a filter designed to perform differential processing in the minor axis direction, which is almost orthogonal to the blood vessel. . For example, using the filter kernel shown in FIG. 2, weighted integration can be performed on the acquired finger image data in two dimensions to obtain an enhanced blood vessel image. The image is
A process of inverting the brightness and lowering the outside of the finger to 0 with the brightness value is performed.

FIG. 3 shows a detailed procedure of a process of collating with an authorized person data registration image after the above-described filtering and unnecessary portion removal operation processing. First, in step 31, a sum of products of matrix elements is calculated based on a two-dimensional matrix composed of pixel values of each pixel of the image between the registered image and the acquired image obtained by performing the above processing, and Performs two-dimensional convolution integration, shifting one element at a time in the vertical and horizontal directions. Next, in step 32, the maximum value (A) of the two-dimensional Laplacian is obtained in order to evaluate the amount of change of the sum of products on the two-dimensional plane. t Next, the same image, for example, between the acquired images, is subjected to the same convolution operation as in 31 above, and the maximum value (B) of the two-dimensional Laplacian is obtained as in 32 above. In step 34, the value of the maximum value (A) is normalized by the value of the maximum value (B) to obtain an evaluation value for collation. That is, this collation utilizes the fact that when two identical images overlap each other, a steep peak is generated in the sum of the products when the two images overlap, but this peak is not generated between different images. Since the distribution of the brightness values is different for each image, the calculated numerical value is based on the numerical value calculated by the operation performed between the same images over two stages,
It is normalizing. The finally obtained evaluation value is between 0 and 1. A threshold value is set to, for example, 0.4, and discrimination between a person and another person, that is, personal authentication can be performed based on whether or not the obtained evaluation value exceeds the threshold value.

FIG. 4 shows an overall flow chart of authentication in this embodiment. In step 20, the image of the finger vein pattern obtained in step 10 is filtered by a filter designed to have a non-uniform background to enhance the blood vessel pattern, and to remove unnecessary parts. Performs arithmetic processing. Next, in step 30, collation with the registration data of the person to be authenticated is performed. The verification procedure is as follows:
This is as described in the description of FIG. If the evaluation value obtained as a result of the collation processing is equal to or smaller than the set threshold, non-permission information is issued in step 40, and if it exceeds the threshold, permission information is issued in step 50. When the permission information is issued, the registration data is updated with the obtained information.

[0015]

According to the present invention, by using a filter designed with directivity, an inhomogeneous background can be appropriately removed from a finger image, and a blood vessel image that can be used for authentication calculation can be enhanced. Further, by adding a two-stage normalization process to the authentication calculation process, it becomes possible to separate the user and the other person from a threshold set between 0 and 1. In addition, an image of the vein pattern of the finger to be authenticated can be obtained more clearly and with good reproducibility.

[Brief description of the drawings]

FIG. 1 is a block diagram of a personal authentication device according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of a filter kernel used in the embodiment.

FIG. 3 is a flowchart illustrating a procedure of a calculation process on a finger image in the embodiment.

FIG. 4 is a flowchart illustrating an authentication procedure according to an embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Hand of a to-be-authenticated person, 2 ... Vein pattern acquisition part, 3 ... Light source part, 4 ... Input device, 5 ... Calculation device, 6 ... Storage device.

Continuing on the front page (72) Inventor Etsuji Yamamoto 1-280 Higashi Koigakubo, Kokubunji-shi, Tokyo Inside the Hitachi, Ltd.Central Research Laboratories (72) Inventor Kenichi Kawabata 1-280 Higashi Koigakubo, Kokubunji-shi, Tokyo Inside the Hitachi Research Laboratory Central F term (reference) 2G059 AA05 BB12 CC16 CC20 EE01 FF01 GG00 GG07 JJ03 KK04 MM01 MM05 MM09 MM10 NN01 4C038 VA07 VB13 VC01 VC02 5B043 AA09 BA03 DA05 EA18 GA01

Claims (6)

[Claims] 1. A light source unit, means for imaging transmitted light through a living body, an optical filter having a light transmission characteristic of an arbitrary wavelength width, a configuration in which the degree of freedom of rotation of a finger to be authenticated is reduced, and reproducibility of position is ensured. A personal authentication device comprising: acquired data acquisition means; storage means for each person's registration data; and arithmetic means for processing the acquired image and collating it with the registration data. 2. The method according to claim 1, wherein, when acquiring an image of a finger vein pattern, a gradual change in the longitudinal direction of the finger based on the optical characteristics of the human finger that the light transmission is high at the joints. When performing image processing to remove background due to changes in transmittance and enhance blood vessel running, the direction of the long axis direction of the finger is integrated and the short axis is differentiated. A personal authentication device having a designed image processing means. 3. A data acquisition method according to claim 1, wherein the degree of freedom of rotation of the finger to be authenticated is reduced, the curvature is formed to ensure the reproducibility of the position, and a plurality of finger data are acquired. Personal authentication device having means. 4. In a process of an arithmetic process at the time of authentication, by performing a two-stage normalization process, it is possible to separate an image of a person and an image of another person by a threshold value set between 0 and 1. The personal authentication device according to claim 1, further comprising: 5. The light intensity of a light source for obtaining a blood vessel pattern more clearly on an individual finger having different light transmittance,
The personal identification device according to claim 1, further comprising an aperture adjustment unit. 6. The personal authentication apparatus according to claim 1, further comprising means for separating artificial light and natural light existing in the surrounding environment from light emitted from the light source.