JPH0516621B2 - - Google Patents

Description

TECHNICAL FIELD The present invention relates to a figure center position determining apparatus, and more particularly to a figure center position determining apparatus for determining the figure center position of a curved figure pattern such as a fingerprint.

Prior Art 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.'' Various devices have been proposed that perform identity verification with fingerprints stored in registered files.

In such a fingerprint verification device, a finger placed on a finger placement surface of a glass prism is detected from the back side of the placement surface using the optical boundary conditions of the glass to connect to a light source.
It has a fingerprint input device that generates a photoelectrically converted image of a fingerprint pattern using an imaging device such as an ITV, and is disclosed in, for example, Japanese Patent Laid-Open No. 54-69300 and Japanese Patent Application Laid-open No. 54-85600.

In such a device, the input fingerprint is identified by comparing the characteristics of the input fingerprint pattern with one of the fingerprint pattern characteristic information in a plurality of files stored in advance in the storage means. The individual is identified by determining the identity of the person. Therefore, it is necessary to accurately collect the image pattern of the input fingerprint pattern in order to ensure accuracy in feature extraction and matching processing. When the center line of the image pattern matches the scanning line, almost the entire fingerprint pattern is collected, and the number of feature points obtained on the pattern increases, and matching based on the features in the registered file is performed. This is desirable because it provides improved performance. If these two center lines match, the entire fingerprint pattern will be detected by scanning and converted into an electrical signal; if both center lines deviate, part of the fingerprint pattern will not be scanned, resulting in a complete fingerprint. This makes pattern detection difficult.

Therefore, there is a need for a device that automatically determines the center position of the fingerprint pattern. Conventional examples include those disclosed in Japanese Patent Publication No. 58-55548 and Japanese Patent Publication No. 58-55549, but the configuration is extremely complicated. It's summery.

OBJECTS OF THE INVENTION An object of the present invention is to provide a simple graphic center position determination device that can automatically determine the center line position of a linear graphic pattern such as a fingerprint, which is composed of a plurality of curved lines.

Composition of the Invention The figure center position determining device according to the present invention is a device for determining the center line position of a line figure consisting of a plurality of curves in which curves are sequentially arranged outside one curve, and is an apparatus for determining the center line position of a line figure having a line figure. an input unit that optically scans the line pattern to quantize the line pattern; a means for detecting each direction of the curve and its directional distribution on each scanning line obtained by scanning the line pattern; and means for determining the center line position of the graphic.

Examples Examples of the present invention will be described below with reference to the drawings.

FIG. 1 and FIG. 2 are diagrams explaining an embodiment of the present invention. When scanning a fingerprint pattern as shown in Fig. 1 in a direction perpendicular to the longitudinal direction of the pattern (horizontal scanning line directions indicated by a and b), signals from each scanning line a and b are used. When the directions (angles formed with the scanning line) of the ridges of the respective fingerprints and their directional distributions are determined, it can be seen that the results are as shown in FIGS. 2a and 2b. Here, it is assumed that the direction is determined as shown in FIG. 3c.

What can be seen from this is that in the case of FIG. 1, the more frequently the direction of the ridge line is perpendicular to the scanning line, the closer it is to the center line of the figure. Therefore, by measuring the direction of the ridge and its distribution for each scanning line and making a determination based on the correlation, it becomes possible to determine the position of the pattern center line. As a method of measuring this ridge direction, for example, 3
A detection mask consisting of nine windows 11 to 33 arranged in a ×3 matrix is prepared, and eight neighboring pixels centered around a black pixel on each horizontal scanning line are applied onto this detection mask. The direction of the ridge can be determined by examining the gray levels of nine pixels in the mask. For example, if a black level signal indicating a ridge is obtained by the detectors 13, 22, and 31 as shown in a, the ridge is tilted by +45° with respect to the scanning line, and the detector 12 and 31 as shown in b , 22, 32, if a black level signal is obtained, it means that the signal is perpendicular to the horizontal line.

Based on this fact, the block shown in FIG. 4 is obtained. In the figure, 1 is an input unit that optically scans and inputs a fingerprint pattern and converts it into a quantized signal;
2 is a keyboard for inputting an ID number (personal identification number), and 3 is a control unit for controlling this input unit 1 and other devices. The input fingerprint is scanned by the input unit 1, converted into an electrical signal, digitized, and stored in the temporary pattern memory 4. The file 6 is accessed by the ID number input from the keyboard 2, but characteristic information of a plurality of fingerprints is stored in advance in this file 6, and the fingerprint characteristic information specified by the ID number is read out. The data is then derived to the collation unit 5. Therefore, the fingerprint characteristics of the pattern stored in the memory 4 are extracted in the verification section 5 and compared with the information from the file 6.

Here, each component in the embodiment can be easily constructed by a person skilled in the art, and the details thereof will be omitted. Also, a known method can be used for the verification method.

With this configuration, the ridge direction and its directional distribution as shown in FIG. 2 are successively detected for each scanning line using a detection mask as shown in FIG. 3. Therefore, the center line of the figure can be detected, but although it is not particularly shown in the figure, it is detected whether or not the detected center line of the figure matches the center scanning line. If so, it is also possible to request the user to reprint his or her fingerprint again using known visual or auditory means until the two center lines substantially coincide.

In the above, the 3×3 matrix detection mask shown in FIG. 3 is used, but if a larger matrix, for example 5×5, is used, the direction detection accuracy will be further improved. Furthermore, the example of direction detection is not limited to this example.

Effects of the Invention According to the present invention, it is possible to automatically determine the center line position of a linear figure with a simple configuration, and therefore the center position of the line figure to be detected can be controlled to be set at the scanning center. This has the advantage that the entire graphic pattern can be obtained accurately.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between graphic patterns and scanning lines for explaining an embodiment of the present invention, and FIG. 2 is a diagram showing the ridge direction and its directional distribution obtained by each scanning line in the image pattern of FIG. 1. FIG. 3 is a diagram showing an example of a mask for detecting the direction of ridges and eight directions, and FIG. 4 is a block diagram of an embodiment of the present invention. Explanation of symbols of main parts, 1... Input section, 3...
Control unit, 7... Direction detection unit, 8... Center line determination unit.

Claims (1)

[Claims] 1 A device for determining the center line position of a line figure consisting of a plurality of curves in which curves are sequentially arranged outside one curve, which optically scans an object having a line figure to determine the line figure. an input unit for quantizing, a direction detection unit for detecting each direction of the curve and its directional distribution on each scanning line while scanning the line figure, and a center for determining the center line position of the line figure based on the detection result. A figure center position determining device comprising: a determining section.