JPH03218575A - Feature extraction device - Google Patents

Abstract

PURPOSE:To register only the fingerprint of good quality with sufficient number of features effective for collation processing, and to improve collating precision by investigating whether the number of the features extracted from the registered fingerprint is more than a threshold determined beforehand or not. CONSTITUTION:Means 10, 11 to pickup the figerprint picture of a finger placed on a transparent body and output it as two-dimensional quantized data, the means 20 to extract the feature from the quantized data corresponding to every one finger in response to the placement of the finger every time one finger is placed successively on the transparent body, the means 15 to decide whether the features effective for collation are extracted by more than the threshold determined beforehand or not, and the means 20 to control so that the feature of the fingerprint to be inputted next is extracted when the above number of the feature is less than the threshold, and the means 24 to register feature information about the corresponding figerprint together with personal identification information when the above number is more than the threshold are provided. Thus, the fingerprint feature of good quality can be extracted, and in its turn, the characteristic of a collated result can be improved.

Description

[Detailed Description of the Invention] Technical Field The present invention relates to a feature extraction device, and more particularly, to a feature extraction device that extracts a feature file necessary for matching processing in a fingerprint matching system that determines the identity of an input fingerprint and a registered fingerprint based on fingerprint characteristics and performs personal identification. The present invention relates to a feature extraction device for creating features.

Conventional technology Fingerprint matching systems that use fingerprints to identify individuals have extremely high reliability due to the characteristics of fingerprints, which are ``unique for all people'' and ``unchangeable throughout life.'' Devices for automatically comparing a collected fingerprint with registered fingerprints registered in advance have already been proposed, and there are many techniques including Japanese Patent Laid-Open No. 59-778.

On the other hand, with the recent development of the information society, the importance of personal identification is increasing when logging on from a computer, accessing data storage, and managing entrance to important confidential areas. Currently, many of these methods are carried out using code numbers or 11) carts, but these can easily lose their effectiveness due to theft, loss, forgery, etc., and it must be said that their reliability is low. I don't get it.

Against this background, the realization of a personal identification device using fingerprint matching technology is eagerly awaited. In this type of device, when inputting a fingerprint, it is not desirable for operational reasons to apply ink to the fingerprint, press it onto a printing paper, and input the ink fingerprint image, as in the case of criminal investigation. Japanese Patent Laid-Open No. 54-69300 proposes a method of inputting a fingerprint image using optical conditions by pressing a finger on a glass surface without using ink. However, when stamping with a finger on a glass surface, the ridges may coalesce due to uneven stamping pressure, and the difference in height of the unevenness of the ridges is small, resulting in low-quality products with little difference in shading. There is a problem with fingerprints being taken.

As mentioned above, among the fingerprints input as registered fingerprints,
Some low-quality fingerprints are included, and it is generally difficult to extract features from these low-quality fingerprints, resulting in a deterioration of the verification results.

Purpose of the Invention Therefore, the present invention has been made to overcome the drawbacks of the prior art, and its purpose is to effectively extract high-quality fingerprint features and improve the characteristics of the verification results. An object of the present invention is to provide a feature extraction device that achieves this.

Composition of the Invention A feature extraction device that compares an input fingerprint image and a registered fingerprint image and extracts fingerprint pattern features used in checking whether the input fingerprint image matches the registered fingerprint image. , a means for collecting a fingerprint image of a finger placed on the transparent body and outputting it as two-dimensional quantized data, and responding to each finger placed on the transparent body in sequence, a means for extracting features from the quantized data corresponding to each finger; a means for determining whether features effective for the matching have been extracted at or above a predetermined threshold; A feature extraction device is obtained, comprising: means for controlling the extraction of features of a fingerprint inputted to a fingerprint; and means for registering feature information about the fingerprint together with personal identification information if the fingerprint is equal to or greater than the threshold value. .

Example Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention. This embodiment includes a fingerprint image input unit 10 that collects a gray-scale fingerprint image of a finger placed on a transparent body and photoelectrically converts the image, and an A/D converter 11 that converts the photoelectric conversion signal into two-dimensional quantized image data.
and a fingerprint placement inspection unit 1 that detects placement of a finger and outputs a detection signal by converting the density of pixels at predetermined positions in the collected image.
2, an input image collection control unit 13 that performs input image collection control after receiving a detection signal, an image storage unit 14 that stores a two-dimensional image of the collected fingerprint, and the number of extracted features. a feature determination unit 15 that determines whether or not the value is greater than a certain value; a file 24 that stores the extracted features; an input section 23 for inputting information;
It consists of an output section 22 that outputs the feature extraction process and feature determination results, and a feature extraction section 20 that performs feature extraction processing. Note that 23 is an image output section.

Regarding the fingerprint image input unit 10, processing is performed to input a photoelectric conversion image of a fingerprint pattern using an imaging device using optical conditions caused by incident light from a light source with respect to a finger placed on a transparent body. For example, JP-A-54-6
There is a device described in Japanese Patent No. 9300 and is used.

The fingerprint placement inspection unit 12 and the input image collection control unit 13 detect the placement of the finger by changing the density value of a pixel at a predetermined position in the image repeatedly captured by the imaging device, and output a detection signal to the input image. The image is sent to the collection control unit 13, thereby collecting the image input.
There is a device described in Japanese Patent No. 255480, which is used. The two-dimensional quantized image thus obtained is stored in the image storage section 141.

FIG. 2 shows a fingerprint pattern button including feature points (hereinafter referred to as minutiae) in this embodiment, FIG. 3 shows directions of end points and branching points, and FIG. 4 shows a schematic configuration diagram of a minutiae list for each minutiae.

In Figure 2.3.4, the features of the fingerprint are the end points 20l,
Position coordinates of minutiae M+ at branch point 202 (X j
, Yi), the direction Di 204, the four-neighbor Mayusha and the relation (rl, r2, r3, r4) 203, and the minutiae type qi as units, expressed in a list for the minutiae Mi that exists multiple times in one fingerprint. It is something. Detailed definitions and detection methods of these are described in Japanese Patent Application Laid-open No. 138174/1982.
The explanation thereof will be omitted here.

Basically, the verification process is performed based on whether or not the above-mentioned minutiae is present in the fingerprint pattern, and if a certain number or more of minutiae are confirmed on the pattern, the fingerprints are considered to be the same. This verification method is also described in detail in Japanese Unexamined Patent Publication No. 55-138174, and therefore will not be described here.

[Feature determination unit in FIG. 4.

FIG. 5 is a diagram showing the processing flow in this apparatus. The finger placed on the fingerprint image input section 10 is detected by the fingerprint placement detection section 1.
In step 2, the input timing is controlled by examining temporal gradation changes on the image, and the image is stored in the image storage section 14.

Next, it is determined whether or not the capacity of the image storage section 14, for example, the hard disk, is full. If it is full, an input impossible message is displayed on the output section 22.

After the registered finger is input, the above-described feature extraction and feature determination are performed on the fingerprint stored in the image storage unit 14. If registration is possible, it is registered in the file 24.

If registration is not possible, registration will not be performed, and a message asking whether to input the next fingerprint will be displayed on the output unit 22. If the fingerprint is input, the process returns to the first input process; if the fingerprint is not input, all processing ends. do.

After the manualist is stored in file 24,
In response to a command from the central processing unit 17, a storage completion message is displayed on the output unit 22, and then sent to the stored manual list via the input unit 23! A D number is assigned.

In this embodiment, the number of minutiae was used as a criterion for determining whether or not to register in the feature determination unit 15, but various features that occur in the feature extraction process, for example, if the image quality of a local region is low. Even if the number of "unknown areas" is used, the quality of this process remains unchanged.

Effects of the Invention As explained above, the present invention checks whether the number of features extracted from registered fingerprints is greater than or equal to a predetermined threshold, thereby identifying a high This has the effect of registering only high-quality fingerprints and improving matching accuracy.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a schematic diagram of a minutiae in the embodiment of Fig. 1, and Fig. 3 is a schematic diagram of the direction of the end point and branch point in the embodiment of Fig. 1. Figure 4 shows the manualist, Figure 5 shows the first
FIG. 3 is a process flow diagram in the illustrated embodiment. Explanation of symbols of main parts 10... Fingerprint image input section 11... A/D conversion section 12... Fingerprint placement inspection section 13... Input image Collection control unit 14... Image storage unit 15... Feature determination unit 20... Feature extraction unit 24...File

Claims (1)

[Claims] (1) A feature extraction device that compares an input fingerprint image and a registered fingerprint image and extracts fingerprint pattern features used in checking whether the input fingerprint image matches the registered fingerprint image. , a means for collecting a fingerprint image of a finger placed on the transparent body and outputting it as two-dimensional quantized data, and responding to each finger placed on the transparent body in sequence,
means for extracting features from the quantized data corresponding to each finger; means for determining whether features effective for verification have been extracted at or above a predetermined threshold; and if the features are at or below the threshold; 1. A feature extraction device comprising: means for controlling the extraction of features of a fingerprint inputted to the fingerprint; and means for registering feature information about the fingerprint together with personal identification information if the value is equal to or greater than the threshold value.