JPH057749B2 - - 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 for verifying the identity of 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, whether or not the input fingerprint can be identified is determined 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 a storage procedure. The individual is identified by determining the identity of the person. Therefore, it is necessary to accurately capture the image pattern of the input fingerprint pattern in order to ensure accuracy in feature extraction and verification processing. In particular, if the center line of the image pattern coincides with the central scanning line of the image scanning section of the photoelectric conversion section, then almost the entire fingerprint pattern will be collected, and it will be possible to obtain the image on this pattern. This is desirable because it increases the number of feature points and improves the performance of matching based on the features in the registration file. 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 and the complete fingerprint pattern will be completed. This makes 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 Publications No. 58-55548 and No. 58-55549, but the configuration is extremely complicated. It is becoming.

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

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 graph meter 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 graph meter that has a line figure. An input unit that optically scans an object and quantizes the line figure, and obtains run length information, which is a series of approximately constant density according to the curve on each scanning line obtained by scanning the line figure, and quantizes the line figure. It is characterized by having a run length detection unit that calculates each run length length and its frequency of appearance for each scanning line based on run length information, and a center line determination unit that determines the center line position of the line graph meter based on the calculation result. shall be.

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

FIGS. 1 and 2 are diagrams for explaining an embodiment of the present invention, and the direction a to perpendicular to the longitudinal direction of the fingerprint pattern (indicated by diagonal lines) as shown in FIG. When performing pattern scanning in the horizontal scanning line direction shown in c), each scanning line a to c
The length of the run of the light and dark (in this case, black) levels obtained by each signal and the frequency of their appearance are calculated as follows.
It can be seen that the results are as shown in FIGS. 2a to 2c.

Note that the fingerprint ridge portion is black (hatched) and the background portion is white.

What can be seen from this is that in the case of the fingerprint pattern shown in Figure 1, the shorter the run length, that is, the scan line in which the black level of this smaller length appears more frequently, the closer the scan line is to the center line position of the pattern. ing. Therefore, by measuring and determining the length of a run, which is a series of black level signals, and its appearance frequency for each scanning line, it becomes possible to determine the position of the pattern center line.

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

On the other hand, run length information from the scanning line obtained by the input section 1 is detected by the run length detection section 7. This information is the length of a run that is a series of black levels, that is, the appearance frequency of the run length, and is stored in the memory 8 for each search. These pieces of run length information are compared on a scanning line by scan line basis to determine the center line. Then, the figure center coincidence determination unit 1 determines whether or not the center scanning line among the scanning lines matches the center line determined by the comparison unit 9.
0, and if they do not match, the control unit 2
The system feeds back a discrepancy signal to the user and requests the user to reprint the fingerprint using a visual method or a known visual method. Here, each component can be easily constructed by a person skilled in the art, so the detailed description thereof will be omitted. Furthermore, a known method will be used for the verification method.

FIG. 4 is a flowchart explaining the operation of the device shown in FIG. 3. When an ID number is input and a fingerprint is affixed, image scanning is started and run length information is detected for each scanning line. . From this information, the run length value and appearance frequency are respectively detected,
Based on this detection result, the scanning center line (the center line of the input fingerprint) is determined as described above. Then, it is determined whether or not the determined scanning center line matches or does not match the figure center line of the reference registered fingerprint.
An example of this determination method is to detect a match between the run length values and frequency of appearance of both. If there is a mismatch, the user is requested to stamp again and the same process is executed again. In this way, when the figure center line and the scanning center line approximately match,
Only at this point does the fingerprint verification process begin.

Note that a known method is used to determine whether or not a fingerprint has been imprinted by processing an input image using a photodiode or the like.

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

[Brief explanation of drawings]

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 run length of a run obtained by each scanning line in the image pattern of FIG. 1 and its appearance. FIG. 3 is a block diagram of an embodiment of the present invention, and FIG. 4 is a flowchart showing the operation of the blocks in FIG. 3. Explanation of symbols of main parts, 1... Input section, 3...
Control unit, 7... Run length detection unit, 8... Run length information storage unit, 9... Run length information comparison unit, 10... Graphic center 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, the apparatus determining the center line position of a line figure by optically scanning an object having a line figure. an input unit that quantizes the line pattern, obtains run length information that is a series of approximately constant density according to the curve on each scan line while scanning the line figure, and calculates each run length length and its appearance frequency using this run length information. A figure center position determination device comprising: a run length detection unit that calculates a run length for each scanning line; and a center position determination unit that determines a center line position of the line figure based on the calculation result.