JPS59103175A - Fingerprint collator - Google Patents

Abstract

PURPOSE:To attain the automatic and high-speed collation of a fingerprint by using an optical system to extract the feature of a minor region of a fingerprint picture which is obtained by scanning a laser beam. CONSTITUTION:First, a laser beam L is irradiated from a laser light source 1 to the optional minor region of a finger 6 press-fixed to a prism 5. A fingerprint picture containing a dark rising line part is sent to a Fourier conversion lens 7 from the prism 5. The result of Fourier conversion is converted into a digital signal by a control circuit 9 via a detector 8 and stored. The feature quantity is calculated by a calculating circuit 10 from the information of the circuit 9. This feature quantity is matched with the fingerprint features, etc. of an external memory 12, and an access is given to an output signal control circuit 15 to have an operation in accordance with the propriety of said matching. These proc esses for input control, matching and output control are carried out by a CPU13 via a common bus 14.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fingerprint verification device using an optical system.

Conventionally, devices that perform Fourier transformation as in the present invention have been put into practical use as devices that perform fingerprint verification using an optical system. This device uses lasers, lenses, etc. to first perform full-screen Fourier transform on an input fingerprint image to create a hologram of it, and then superimposes a hologram of the fingerprint image in a file obtained using the same procedure to create a hologram. Fingerprint verification is performed by performing Fourier transformation and finding the optical correlation.

The conventional device described above performs fingerprint verification using full-screen Fourier transform, and although it is capable of roughly classifying the shape of fingerprints, it is not suitable for detailed identification. In other words, it is suitable for extracting fingerprints that are similar in shape to the input fingerprint from among a huge number of files, but it is suitable for one-to-one high-precision matching, such as for ID card assistance. Not suitable for applications that require Additionally, the need to process the input sample into a film is a major impediment to automated fingerprint verification.

This invention has been made in view of the above points, and is characterized by having a mechanism for extracting features of a small region of a fingerprint image obtained by scanning a laser beam. The present invention aims to realize a fingerprint verification device suitable for increasing the accuracy of fingerprint verification, miniaturizing the device, and automating verification.

This invention will be explained below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention, in which 1 is a laser light source (LD), 2 is a laser beam focusing lens, 3 is a holographic scanner, and 4 is for operating the holographic scanner 3. Motor, 5 is a prism, 6 is a finger, T is a Fourier transform lens, 8 is an image sensor (CC
9 is a detector signal input control circuit, 10 is a feature amount calculation circuit, 11 is a memory, 12 is an external memory (for storing personal feature amounts), and 13 is a CPU.

14 is a common bus, 15 is an output signal control circuit, and 1 is a laser beam control circuit.

The apparatus of the embodiment of FIG. 1 operates on the following principle.

First, laser light source 1. Laser beam focusing lens 2° holographic scanner 3. The laser beam control circuit 16 irradiates the laser beam L onto an arbitrary small region of the surface where the finger 6 is pressed against the prism 5. The timing of this irradiation and the irradiation area are shown in Figures 2 (a) and (b).
Shown below.

As shown in FIG. 2(a)K, the crimping surface 17 of the fingerprint image is scanned while sequentially moving for each irradiation area 1B. However, the motor 4 that rotates the holographic scanner 3 rotates at a constant rate. As shown in FIG. 2(b), the irradiation timing is as follows: the Fourier transform lens 7, the detector 8. After the feature amount calculation by the feature amount calculation circuit 10 is completed, the process proceeds to irradiation of the small area A2. Second
T in figure (b) is a small area AI l A2 +...Afi
, and 19 is the laser beam irradiation time.

The portion irradiated with the laser beam L is sent to the Fourier transform lens 7 as a fingerprint image with darkened ridges based on the principle of total reflection of the prism 5. The result of Fourier transformation by the Fourier transformation lens 7 is taken into a detector 8 such as a COD processor, converted into a digital signal by the input control circuit 9 of this detector 8, and stored. Next, the feature amount calculation circuit 10 calculates the feature amount necessary for verification from the information of the input control circuit 9. The above is the process of extracting small areas of a fingerprint image.

Next, a method of comparing the characteristic amount with the individual characteristic amount existing in the external memory 12 using this characteristic symptom will be explained.

The feature quantity calculation circuit 10 performs matching of the extracted feature quantity and the fingerprint feature with the external memory 12, and the output signal control circuit 15 is accessed seven times to perform an operation depending on whether or not matching is possible. For example, in an entrance/exit management system, the coil corresponds to the opening/closing operation of a door.

The above input control, matching, and output control processing is performed by the CP
U13 performs the communication via the common bus 14.

As for the prism 5, as shown in FIG. 3, if a coating 20 is applied to one side of the prism 5 to block the incidence of light and the detector 8 and the laser beam L are on the same side, fingerprints can be easily detected. Passage path of light from contact portion 22 and non-contact portion 21 to prism 5 1. Due to the difference in I can get an image, but
The mechanism becomes more or less complicated. Other principles are similar.

Next, an example of processing for the Fourier transform plane taken into the processing system by the detector 8 and the input control circuit 9 will be described.

Figure 4 shows detector 8. The data on the Fourier transform plane taken into the processing system by the input control circuit 9 is expressed in shading. 23 in FIG. 4 is the first peak which is the largest peak at wave number 0, and 24 in FIG. 4 is the second peak which is the next largest peak. The original fingerprint image from which the Fourier transform plane of FIG. 4 is obtained has a shape as shown in FIG. 5, but due to the nature of Fourier transform, A straight line 25 connecting these lines is approximately normal to the ridge line 26 of the fingerprint image shown in FIG. That is, by having a mechanism for recognizing the positions of the first beak 23 and the second beak 24 on the Fourier transform surface, the directionality of the original fingerprint image small area can be calculated. The positions of the first beak 23 and the second beak 24 are
By using a CCD image sensor as the detector 8, it can be easily realized as a digital circuit.

As mentioned above, it is possible to extract the directionality of a fingerprint image small area by using the first beak 23 and the second beak 24 on the Fourier transform surface, but some fingerprint image small areas have clear directionality. , some are unclear, so a means is needed to assist in extracting the most dominant direction using only the first beak 23 and second beak 24.

An example of this is the following.

The Fourier transform surface has the first peak 23 as shown in FIG.
It is symmetrical about the center. Therefore, as shown in FIG.
2 of the vectors from the second beak 24 to each point in the region 28 for a region 28 on one side of the Fourier transform plane delimited by a straight line 25 connecting the beaks 24 and a perpendicular straight line 21.
Squared K.

The degree of periodicity is evaluated by the sum of the products multiplied by the size of the point. That is, P=Σfr(ri ro)” ・・・・・・・・・
(1) Tatami ro is a vector from the first beak 23 to the second beak 24, and rl is a vector from the first beak 23 to each point in the region 28. 1 is a parameter that defines each point within the region 28, and defines only the points within the region shown at 29 in FIG. Although this area 21C is determined empirically, it is effective to make it approximately a rectangular area in order to make it suitable for digital processing. The larger the value of P determined by Equation 11, the more non-periodic the fingerprint image small area becomes, and the smaller the value, the more pronounced the mono-periodicity becomes. Alternatively, by implementing and adding it using a simple hardware 7, it can be used as a feature amount of the fingerprint image small area together with the previous IC4 solid directionality.

As described above in detail, the fingerprint verification device of the present invention achieves high-speed verification because it uses an optical system to collect a fingerprint image and extract characteristics of a small region of the fingerprint image.

Can be automated. Furthermore, since the Fourier transform of a small region of a fingerprint image is used as a feature, it is less susceptible to noise and requires less preprocessing. In addition, by changing the diameter of the laser beam, it becomes possible to extract a wider range of features (various features), and to achieve higher accuracy in matching.Furthermore, according to the present invention, there is an advantage that the scale of the matching device can be reduced to a large size.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing one embodiment of the present invention, and FIG. 2 (a
), (Time chart 1' - showing the plan view and timing of the area on the prism surface where the laser beam is irradiated)
, FIG. 3 is a diagram of a prism input system part for increasing the SN ratio showing another embodiment of the present invention, and FIG. 4 is a diagram expressing the data of the Fourier transform plane taken in from the detector in shading.
FIG. 5 is a diagram showing the original picture 'f resulting in the Fourier transform surface of FIG. 2, and FIG. 6 is a diagram showing the adaptation area of equation (1). In the figure, 1 is a laser light source, 2 is a laser beam convergence lens, and 3
is a holographic ink scanner, 4 is a motor, 5 is a prism, 6 is a finger, D is a Fourier transform lens, 8 is a detector, 9 is an input control circuit, 10 is a feature calculation circuit, 11 is memory, 12 is external memory, 13 is a CPU, 14 is a common bus, 15 is an output signal control circuit, 16 is a laser beam control circuit, 1T is a crimping surface, 18 is an irradiation area, 19 is a laser beam irradiation time, 20 is a coat, 21 is a non-contact part, 22 is the contact part. Figure 1 et al. 11 1Z -1″D Figure 2

Claims (2)

[Claims] (1) a laser light source, a holographic ink scanner that scans the laser beam from the laser light source, an optical system that extracts a fingerprint image of a small area irradiated with the laser beam;
A fingerprint characterized by comprising an optical system that Fourier transforms reflected light from the fingerprint, an image sensor that converts the Fourier transformed optical image into an electrical signal, and a circuit that calculates feature amounts from the image sensor signal. Verification device. (2) The fingerprint identification device according to claim (1), wherein the laser beam scanning by the holographic ink scanner is performed intermittently nine times every time the optical image is converted into an electrical signal.