JPH0346875B2 - - Google Patents

Description

TECHNICAL FIELD The present invention relates to a fingerprint image input device, and more particularly to an image input device that optically detects a fingerprint pattern and generates an electrical signal.

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

In such devices, when a fake fingerprint is input, it is necessary to detect it, reject the input of the fake fingerprint, and prevent the verification process from being performed. Conventionally, there are no countermeasures to prevent such fake fingerprint input. is hardly considered. One possible method for inputting such a fake fingerprint is to place a forgery made of rubber or the like, which is engraved in a precise imitation of a fingerprint pattern, on a transparent glass prism.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a fingerprint image input device that prevents unauthorized use by prohibiting input of forged patterns of fingerprint images as described above.

Structure of the Invention A fingerprint image input device according to the present invention places a finger on a placement surface of a transparent body, irradiates the placement surface with light from the side opposite to the finger, and reflects light from the placement surface. A fingerprint input device that detects a fingerprint image pattern using a fingerprint input device, which measures the number of black pixels of an image pattern by reflected light at a predetermined time when a fingerprint is imprinted, and the number of black pixels after a predetermined time has elapsed from this predetermined time. It is characterized by having means for storing, and means for comparing both measured values and detecting whether or not the number of black pixels has increased over time, and by detecting this increase, it is determined whether a fake fingerprint has been input. shall be.

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

When a fake fingerprint is input using a rubber stamp as described above, unlike a human finger, there is no sweating effect, so there is no temporal change in the density of the image obtained with this fake fingerprint. On the other hand, in the case of a human finger, the shading of the image changes over time due to sweating. This is because sweat due to perspiration fills up between the fingers and the prism surface over time, and the incident light from the light source is refracted by this sweat. The present invention utilizes this fact to prevent the input of forged fingerprints, and FIG. 1 shows a schematic block diagram of a fingerprint verification system using a fingerprint image input device according to an embodiment of the present invention.

An image pattern obtained by an input section 1 that optically scans a fingerprint imprinted on a prism surface and converts it into a quantized signal is temporarily stored in an image memory 4. On the other hand, the ID number from the keyboard 2 accesses the file 9, which stores the characteristic information of each person's fingerprint pattern in advance, and the corresponding fingerprint characteristic information is read out based on the ID number and collated. 5. This verification section 5
In this step, the information from the file 9 is compared and verified with the feature information extracted from the fingerprint image pattern stored in the memory.

On the other hand, a black pixel measuring section 6 is provided to detect changes in shading of the input fingerprint image over time. The number of detected black pixels having a certain density or higher is counted. Each measurement value is stored in the black pixel number storage section 7, and these two measurement values are compared in the comparison section 8. Based on the comparison result, it is determined whether or not a forged fingerprint has been input.

Here, each component in the embodiment can be easily accomplished by a person skilled in the art, and the details thereof will be omitted. Furthermore, a known method is used as the verification method.

FIG. 2 is a flowchart for explaining the operation of the block shown in FIG. 1, and shows the flow of forgery input determination based on the presence or absence of a change in shading over time, that is, an increase in the number of black pixels.

When the ID number is input and a fingerprint is affixed, the image is scanned and the measurement of the number of black pixels begins.
The measurement results at this time are stored and a fingerprint verification process is performed in parallel. After this, after a certain period of time, the image is scanned again and the number of black pixels is measured.
The number of black pixels in the previous scan is compared with the number of black pixels in the current scan to determine whether the input is a forged input. If no increase in the number of black pixels is detected, it is determined that a forged fingerprint such as a rubber stamp has been input, and all subsequent verification processing is rejected. If the number of black pixels increases, it is assumed that the input was made by a human finger, and the verification result is output.

Effects of the Invention According to the present invention, it is possible to effectively prevent the input of forged fingerprints, thereby improving the reliability of the system.

[Brief explanation of drawings]

FIG. 1 is a schematic block diagram showing an embodiment of the present invention, and FIG. 2 is a flowchart showing the operation of the blocks in FIG. Explanation of symbols of main parts, 1... Input section, 3...
Control unit, 6... Black pixel measurement unit, 7... Black pixel number storage unit, 8... Black pixel number comparison unit.

Claims (1)

[Claims] 1 Fingerprint image in which a finger is placed on the placement surface of a transparent body, light is irradiated onto this placement surface from the side opposite to the finger, and a fingerprint image pattern is detected using reflected light from this placement surface. The input device includes means for measuring and storing the number of black pixels of the image pattern caused by the reflected light at a predetermined time when a fingerprint is imprinted, and the number of black pixels after a predetermined period of time has elapsed from the predetermined time, and for storing both of the measured values. A fingerprint image input device comprising means for comparing and detecting whether or not the number of black pixels has increased over time, and by detecting this increase, it is determined whether a fake fingerprint has been input.