JPH01314383A - Contact type fingerprint detecting device - Google Patents

Abstract

PURPOSE:To always obtain a fingerprint image extending over a wide area and being distinct by deciding whether the maximum distance between two points in which the luminance of the fingerprint image exceeds a threshold value exceeds the threshold value or not, and using the fingerprint image which has been obtained after it has been decided that the distance exceeds the threshold value, for a collation processing or a registration processing. CONSTITUTION:The title device is provided with a means for deciding whether the maximum distance W between two points in which the luminance of a fingerprint exceeds a threshold value S0 exceeds a threshold value W0 or not, and the fingerprint image which has been obtained after it has been decided that this distance W exceeds the threshold value W0 is used in a collation processing or a registration processing. The fingerprint image which has been obtained after it has been decided that this distance W exceeds the threshold value W0 is a fingerprint image obtained at the time when perspiration of a finger becomes moderate and its contact with a light guiding member has become close. In such a way, a fingerprint image extending over a wide area and being distinct can always be obtained.

Description

[Detailed Description of the Invention] [Table of Contents] ll! Key industrial fields of application Conventional technology (Fig. 5.6) Problems to be solved by the invention Examples of means and actions for solving the problems (Figs. 1 to 4) Effects of the extended invention [11! [Required] Finger light guide: Regarding the contact type fingerprint detection device that optically converts the state of contact with the 1S material into a fingerprint image, the purpose is to always obtain a clear fingerprint image over a wide area, and the brightness of the fingerprint image is Maximum distance W between two points with threshold value 80 or more
comprises means for determining whether or not is greater than or equal to a threshold value W6;
The fingerprint image obtained after it is determined that the distance fm w h < w o or more is used in the verification process or the registration process.

[Industrial Field of Application] The present invention relates to a contact type fingerprint detection device that optically converts the contact state of a finger to a light guide member into a fingerprint image.

[Prior Art] In recent years, as computers have been introduced into a wide range of social systems, people concerned have been paying attention to system security. It has been used until now as a means of verifying identity when entering a computer room or using a terminal! Many questions have been raised about D-cards and passwords from the perspective of ensuring security. Fingerprints, on the other hand, are considered the most viable means of identifying individuals because they are unique to everyone and remain unchanged throughout life, and much research and development has been conducted on simple personal identification systems using fingerprints. It is being said.

Contact-type fingerprint detection devices utilize the fact that when a finger is pressed against a light guide plate (for example, glass), the reflectance and transmittance of light change at the contact area, and the light source is applied to the interface between the finger and the light guide plate. The light is incident from the light guide plate side or the finger side, and the light that is reflected at the boundary surface or transmitted through the boundary surface and totally reflected inside the light guide plate is guided to the image sensor to detect a fingerprint image. It has become.

In order to reliably register and verify fingerprint images, it is necessary to obtain clear fingerprint images over a wide area. Therefore, it is desirable that the fingers sweat appropriately and are in close contact with the light guide plate.

[Problem to be solved by the invention] However, there are individual differences in sweating, and even within the same person, the degree of sweating varies depending on the psychological state at the time. People who are relatively active in sweating, as shown in Figure 5,
The brightness S of the fingerprint image exceeds the binarization threshold S0 over a wide range, but for people who sweat relatively slowly, as shown in FIG. 6, the range in which the brightness S of the fingerprint image exceeds the threshold S0 is narrow; In some cases, only an unclear and narrow fingerprint image is obtained.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, it is an object of the present invention to provide a contact-type fingerprint detection device that can always obtain a clear and wide fingerprint image regardless of individual differences in sweating.

[Means for Solving Problems] In order to achieve this object, the present invention provides a contact fingerprint detection device that optically converts the contact state of a finger to a light guide member into a fingerprint image. The fingerprint image is provided with means for determining whether the maximum roughness #tW between two points with brightness b (threshold value S0 or more) is greater than or equal to the threshold value W0, and is obtained after this distance W is determined to be greater than or equal to the threshold value W0. is used in verification processing or registration processing.

[Operation] Therefore, a fingerprint image is obtained when the finger sweats on the light guide member to a certain degree and the finger is in close contact with the light guide member, and a clear fingerprint image covering a wide area is always obtained.

[Example] (1) One example An embodiment of the present invention will be described based on the drawings.

FIG. 2 shows the configuration of a contact type fingerprint detection device.

The light guide plate 10 is, for example, rectangular glass. − of the light guide plate 10
A laser light source 12 is disposed below 7371 with its radiation surface facing upward. Further, a phase type hologram 14 for diffraction is adhered to the other end surface of the light guide plate 10.

When the laser light emitted from the laser light source 12 is irradiated to the interface between the light guide plate IO and the finger 16 with the finger 16 pressed against the four-light plate IO above the laser light source 12, the light guide plate 10 of the finger 16 is irradiated with the laser light emitted from the laser light source 12. The laser beam is mainly reflected at the close contact part of the laser beam, and a part of it undergoes total internal reflection repeatedly, resulting in a light emission of 1 gram! 4 and is diffracted downward and led out.

A two-dimensional image sensor 20 is disposed below the hologram 14 via an imaging lens 18, and a fingerprint image is captured on the image sensor 2.
The image is formed on the imaging plane of 0.

The image sensor 20 is scanned by a drive pulse from the driver 22, and pixel signals are sequentially extracted from the image sensor 20.
This is amplified by the amplifier 24 to become the luminance S, and then converted to 26° by the binarization circuit 26. The binarization threshold is So.

The microcomputer 28 reads the binarized data for each pixel based on the synchronization signal supplied from the Drino (22) and writes the fingerprint image in its frame memory. Depending on the mode, this read fingerprint image is registered in the registration memory 32, or is compared with the fingerprint image registered in the registration memory 32, and the results of the processing are displayed on the display 34.

Next, the processing procedure in the microcomputer 28 will be explained based on FIG. 2, taking the introductory matching process as an example.

(50) When the finger 16 is not pressed on the light guide plate IO or is lightly pressed on the light guide plate IO, the brightness S is s < S a, and the output value of the binarization circuit 26 is It is always °0°.

(52) In this case, the display 34 displays "Please press your finger."

When the finger 16 is pressed against the light guide plate 10 with a certain degree of force, as shown in FIG. 3, the brightness data of the fingerprint image changes to -;'
l< becomes S≧50, and (54) the maximum distance W between two points (distance between two points a3 and b1) where S≧80 is measured. This measurement may be performed only on the center line of the image, or may be performed on a plurality of lines (including all lines).

(56) If W < W, that is, the light guide plate I
If the contact between O and the finger 16 is insufficient or sweating is inappropriate, (58) the display 34 will display "Please continue to press the finger".

As shown in Figure 4, the maximum type MW (2
When the distance #l) between points λ2 and b1 becomes W≧W0, that is, when the contact of the finger 16 with the light guide plate 10 and the sweating become appropriate, (60) Read After preprocessing the fingerprint image, it is compared with the fingerprint image registered in the registration memory 32.

(62) If a matching fingerprint image is found, (64) the entry name and entry time are recorded, and the display 34 displays "Please enter".

(66) If you cannot find a matching fingerprint image (f
, for example, outputs an alarm.

(2) Expansion Note that the present invention includes various other modifications.

For example, multiple threshold values W6, Wo (W + < Wo
), and when the maximum distance W is W WI, the red lamp is lit, when W1≦W<W o, the yellow lamp is lit, and when W≧W0, the blue lamp is lit. It may be configured such that when the light is turned on, a fingerprint image for registration or verification is read.

Alternatively, the maximum distance W may be displayed with a digital level meter, and the display color etc. may be changed before and after the threshold value.

Alternatively, a configuration may be adopted in which audio guidance is provided depending on the largest type 1w.

In addition, the vertical threshold WOI and the horizontal threshold W of the fingerprint image,
, and the fingerprint image for registration or verification is read when the maximum gravity MW strongly exceeds the threshold value in both directions.

Furthermore, the threshold value may be changed depending on the size of the finger, for example, depending on the distance between the ridges of the detected fingerprint image.

[Effect of the Invention 1] In the contact type fingerprint detection device according to the present invention, there is provided a means for determining whether the maximum MW between two points where the brightness of the fingerprint image is equal to or greater than the threshold value ip't So is equal to or greater than the threshold value Wl1. The fingerprint image obtained after this distance MW is determined to be equal to or greater than the threshold value W0 shows that the finger sweat has become moderate and the light guide 1'4
Since the fingerprint image is obtained when the fingerprint is in close contact with the material, it has the excellent effect of always being able to obtain a clear fingerprint image over a wide area, which contributes to improving the reliability of fingerprint verification. big.

[Brief explanation of the drawing]

1 to 4 relate to one embodiment of the present invention, in which FIG. 1 is a block diagram showing the hardware configuration of a contact fingerprint detection device, FIG. 2 is a flowchart showing the processing procedure of the microcomputer 28, and FIG. 3 and 4 are diagrams showing the 8 degree distribution on the X-line of the fingerprint image. FIG. 5 and FIG. 6 are diagrams for explaining conventional problems. In the figure, lO: light guide plate 12: laser light source! 4: Hologram 16 two fingers! 8: Imaging lens 20: Image pickup element 22: Driver 24: Amplifier 26: Binarization circuit 28: Microcomputer 30: Mode setter 32: Registration memory 34: Display Hardware configuration of the contact fingerprint detection device Fig. 1 Processing procedure of the microcomputer 28 Figure 2 Pancreatic intensity distribution on one line of the fingerprint image Figure 3 Luminance distribution on one line of the fingerprint image Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] In a contact fingerprint detection device that optically converts the state of contact of a finger to a light guide member (10) into a fingerprint image, the maximum brightness between two points at which the brightness of the fingerprint image is equal to or higher than a threshold value S_0 is provided. The distance W is the threshold value W_
A contact-type fingerprint detection device, comprising means for determining whether the distance W is greater than or equal to 0, and a fingerprint image obtained after the distance W is determined to be greater than or equal to W_0 is used in a verification process or a registration process.