JPH0798754A - Fingerprint detecting device - Google Patents

Abstract

PURPOSE:To obtain a satisfactory fingerprint image by using a hard transparent optical member, an elastic transparent optical member and a liquid coupling material as a transparent medium, and forming the optical reference surface on the face of the opposite side to the face opposed to the hard transparent optical member of the elastic optical member. CONSTITUTION:In a transparent medium 20, an elastic transparent optical member 22 having water repellency is provided on a hard transparent optical member 21, a space between the hard transparent optical member 21 and the hard transparent optical member 22 is filled with a liquid coupling material 23, and the hard transparent optical member 21 and the elastic transparent optical member 22 are coupled optically. Also, the optical reference surface 24 is formed on the face of the opposite side to the face opposed to the hard transparent optical member 21 of the elastic optical member 22. In such a state, by pressing down a finger onto the optical reference surface 24 of this transparent medium 20, the elastic transparent optical member 22 is pushed by a raised line of a fingerprint and deformed, and adhesion of the raised line of the fingerprint and the optical reference surface 24 is improved. Accordingly, even in the case of the environment in which humidity is low and a dry finger, a satisfactory fingerprint image can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method in which a finger is pressed against an optical reference surface formed on a transparent medium to irradiate the optical reference surface with light through the transparent medium, and reflected light or scattered light The present invention relates to a fingerprint detection device that detects a fingerprint of a finger.

Currently, personal identification numbers, I
D cards are widely used. However, as the value of information further increases, sophisticated personal identification methods are required. Therefore, methods for identifying individuals based on physical characteristics have been developed.

Fingerprints, voiceprints, retinas, and the like are available as methods for identifying an individual based on physical characteristics. Among them, the fingerprint method has different fingerprint patterns for each individual.

It does not change for a lifetime. There is no fear of loss. Counterfeiting is difficult.

It is not bothersome to use. It is relatively easy to take out the pattern. Due to the above reasons, it is most expected.

[0006]

2. Description of the Related Art First, the principle of fingerprint detection will be described with reference to FIGS. In FIG. 5, reference numeral 1 is a transparent medium such as glass or hard plastic having an optical reference surface 2 formed on one surface.

When the ball of the finger 3 is pressed against the optical reference surface 2 of the transparent medium 1, the portion that comes into contact with the optical reference surface 2 is the ridge 4 of the fingerprint, which is between the valley 5 of the fingerprint and the optical reference surface 2. There is a space in between.

Here, the optical reference surface 2 is provided through the transparent medium 1.
When the light is irradiated to the ridge 4, the incident light is scattered in all directions at the ridge 4, and at the valley 5 as shown in FIG. The part is specularly reflected by the optical reference surface 2. In order to increase the ratio of the specularly reflected light, the incident light may be totally reflected by the optical reference surface 2.

The shape of the fingerprint can be recognized by detecting the specularly reflected light at the valley 5. Since the intensity of scattered light differs between the ridge 4 and the valley 5, the scattered light is detected by using this difference.
The shape of the fingerprint can be recognized. In this case, the lightness and darkness are reversed from the case of using specularly reflected light.

Next, the structure of a conventional total reflection type fingerprint detecting device will be described with reference to FIG. Reference numeral 11 denotes a prism having a triangular cross section as a transparent medium. One surface of the prism 11 is used as an optical reference surface 12, and the other two surfaces are used as an entrance surface 13 and an exit surface 14.

A light source 15 for irradiating the incident surface 13 with light and a lens 16 for collimating the light emitted from the light source 15 are provided in the vicinity of the incident surface 13. And the light source 15
The lens 16 and the lens 16 are arranged so that the incident light is totally reflected by the optical reference surface 12.

A lens 17 for collecting parallel light emitted from the emission surface 14 and a photographing system 18 such as a CCD camera for detecting the collected light are provided near the emission surface 14. Then, when the ball of the finger 19 is pressed against the optical reference surface 12, the ridges of the fingerprint come into contact with the optical reference surface 12, the incident light is scattered at this portion, and specularly reflected only at the valley portion and only specularly reflected light Exits from the exit surface 14 and goes to the imaging system 18. Therefore,
In the imaging system 18, the background and valleys appear bright and the ridges appear dark.

Next, the structure of a conventional optical path separation type fingerprint detecting device will be described with reference to FIG. The difference between this apparatus and the above-mentioned total reflection type fingerprint detection apparatus is that the imaging system 21 is arranged in a region R where specular reflection light does not enter and only scattered light is captured.

According to this structure, the background and the valleys appear dark and the ridges appear bright. By the way, the ridges of the fingerprint of a finger have fine irregularities. For this reason, when the finger 19 is pressed against the optical reference surface 12 of the fingerprint detecting device, the ridge line may appear to be broken at first. However, if the finger is continuously pressed against the optical reference surface 12, the fingerprint image becomes gradually clear within 1 to 2 seconds. This is because the finger 19 sweats and the unevenness of the ridge is filled by the sweat.

[0015]

However, the fingerprint detecting device having the above structure has the following problems. In a high humidity environment such as in Japan, the conventional fingerprint detection device could obtain a fingerprint relatively easily even if the optical reference surface 12 was glass or hard plastic. However, in a low humidity environment or in the case of a dry finger person, even if the finger 19 is pressed against the optical reference surface 12 for a long time, the finger may not sweat and a good fingerprint image may not be obtained. is there.

The surface condition of the finger varies from person to person. A proper amount of sweat fills the unevenness of the ridges and improves the fingerprint image,
In the case of a person with wet fingers, there is a problem that a good fingerprint image cannot be obtained because the valleys are filled with sweat due to excessive sweat.

If a scratch or the like is formed on the optical reference surface 12 for some reason, the transparent medium needs to be replaced. However, the replacement requires precision in assembly and is difficult and expensive. In order to solve the above problem, silicone rubber coating is performed on the optical reference surface 12.

However, the silicone rubber coating is easily peeled off, and it is difficult to obtain a flat optical reference surface.
Further, since the material is limited, there is a problem that it is difficult to obtain optimum hardness (elasticity). Furthermore, it takes time and labor to regenerate when dirt or scratches occur. Therefore, the problem of is still present.

The present invention has been made in view of the above problems, and an object thereof is to obtain a good fingerprint image regardless of environmental conditions, and also for a person with a dry finger or a person with a wet finger. The present invention provides a fingerprint detecting device.

Another object of the present invention is to provide a fingerprint detecting device in which the optical reference surface can be replaced easily and at low cost.

[0021]

According to a first aspect of the present invention for solving the above-mentioned problems, a finger is pressed against an optical reference surface formed on a transparent medium, and light is applied to the optical reference surface via the transparent medium. In the fingerprint detection device for irradiating, and detecting the fingerprint of the finger from reflected light or scattered light, as the transparent medium,
A hard transparent optical member, an elastic transparent optical member disposed on the hard transparent optical member, the hard transparent optical member, and a liquid coupling material filled between the elastic transparent optical members, and the optical reference The surface is the surface opposite to the surface of the elastic optical member facing the hard transparent optical member.

According to a second aspect of the invention, the elastic transparent member in the first aspect of the invention has water repellency. Claim 3
In the invention described above, the elastic transparent member in the invention of claim 1 or 2 is silicon rubber.

According to a fourth aspect of the invention, the liquid coupling material in the first to third aspects of the invention is silicone oil. According to a fifth aspect of the present invention, a concave portion matching the shape of a finger to be pressed is formed on the transparent elastic optical member according to the first to fourth aspects.

[0024]

According to the fingerprint detecting device of the invention described in claim 1,
An optical reference surface was formed on the elastic transparent optical member. Therefore,
When the finger is strongly pressed against the optical reference surface, the adhesion between the ridge of the fingerprint and the optical reference surface is improved, and a good fingerprint image can be obtained even in an environment with low humidity or dry fingers.

Further, the elastic transparent optical member on which the optical reference surface is formed is arranged on the hard transparent optical member via a liquid coupling. Therefore, the optical reference surface may be exchanged only by the elastic transparent optical member or, if necessary, by including the liquid coupling.

In the fingerprint detecting device according to any one of claims 2 to 4, since the optical reference surface has water repellency, sweat is concentrated on the ridge portion even with a wet finger, and a good fingerprint image can be obtained. You can

Further, in the fingerprint detecting apparatus according to the fifth aspect of the present invention, since the optical reference surface is provided with the concave portion conforming to the shape of the finger, the adhesion between the finger and the optical reference surface is further improved.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described with reference to the drawings. The present invention is an improvement of the transparent medium in the fingerprint detection device, and the other imaging system, the light source, and the like are the same, so the description thereof will be omitted.

First, the transparent medium 20 according to the first embodiment of the present invention will be described with reference to FIG. In the figure, 21 is a hard transparent optical member. An elastic transparent optical member 22 having water repellency is disposed on the hard transparent optical member 21. A liquid coupling material 23 is filled between the hard transparent optical member 21 and the elastic transparent optical member 22, and the hard transparent optical member 21 and the elastic transparent optical member 22 are optically coupled. Then, the optical reference surface 24 is formed on the surface of the elastic optical member 22 opposite to the surface facing the hard transparent optical member 21.

In this embodiment, glass or hard transparent plastic is selected as the hard transparent optical member 21. still,
The term "transparent" used in the present specification means "at least the light wavelength used in the imaging system passes without undergoing frequency transition".

As the elastic transparent optical member 22, it is necessary to consider hardness, transparency, chemical resistance, weather resistance, wear resistance and the like. Further, in consideration of sweating from the finger, it is desirable that it has water repellency. Further, the hardness is preferably 28 to 80 (JIS K6301). In consideration of these various conditions, silicone rubber and fluororubber were selected in this example.

The optical reference surface 24 formed on the elastic transparent optical member 22 must be an optical smooth surface. If a commercially available molded sheet of silicone rubber or fluororubber is used, an optical smooth surface can be easily obtained at low cost.

The liquid coupling material 23 has a viscosity,
Select in consideration of transparency, chemical resistance, weather resistance, etc. Furthermore,
In the case where the elastic transparent optical member 22 is simply placed on the hard transparent optical member 21 as in this embodiment, a liquid having a low vapor pressure and hard to evaporate is selected in order to prevent evaporation of the liquid coupling material 23. Should. Therefore, glycerin and silicone oil were selected in this example.

Next, a description will be given of the case where the finger 25 is pressed on the transparent medium of the fingerprint detecting device shown in FIG. 1 with reference to FIG. When the finger 25 is pressed onto the optical reference surface 24 of the transparent medium 20,
The elastic transparent optical member 22 is pressed and deformed by the fingerprint ridge 26, and the adhesion between the fingerprint ridge 26 and the optical reference surface 24 is improved. Therefore, a good fingerprint image can be obtained even in an environment with low humidity and dry fingers.

Further, since the elastic transparent optical member 22 on which the optical reference surface 24 is formed has water repellency, sweat is concentrated on the ridges 26 even if it is a wet finger, and a good fingerprint image is obtained. Obtainable.

When the optical reference surface 24 is damaged and needs to be replaced, the elastic transparent optical member 22 is peeled off, and when the liquid coupling material 23 remains on the hard transparent optical member 21, The elastic transparent optical member 22 is placed.
Further, the liquid coupling material 23 is formed on the hard transparent optical member 21.
If no remains, a new hard transparent optical member 2
A few drops of the liquid coupling material 23 are dropped on the surface 1 of the elastic transparent optical member 22. Then, the elastic transparent optical member 2
2 is squeezed to remove air between the hard transparent optical member 21 and the elastic transparent optical member 22, and the liquid coupling 2
The two are optically coupled such that only two exist.

Therefore, as compared with the conventional exchange of the entire transparent medium, only the elastic transparent optical member 22 or the elastic transparent optical member 22 and the liquid coupling material 23 may be exchanged, and the exchange operation is simple and inexpensive. Is.

Next, a second embodiment of the present invention will be described with reference to FIG. The difference between this embodiment and the first embodiment is that the finger 2 pressing on the optical reference surface 31 of the elastic transparent optical member 30.
That is, the concave portion 32 having the shape of No. 5 is formed.

According to the above construction, in addition to the effect of the first embodiment, the adhesion between the finger 25 and the optical reference surface 31 is further improved, so that a good fingerprint image can be obtained. next,
A third embodiment of the present invention will be described with reference to FIG. In the present embodiment, the thickness of the elastic transparent optical member 40 is reduced, and the peripheral edge portion 40a fixed to the hard transparent optical member 21 is used.
And a central portion 40b having a space between the hard transparent optical member 21 and the hard transparent optical member 21. Then, the space between the central portion 40b of the elastic transparent optical member 40 and the hard transparent optical member 21 was filled with the liquid coupling material 41.

According to this structure, in addition to the effect of the first embodiment, the elasticity of the optical reference surface 42 is further increased, so that the adhesion between the finger and the optical reference surface 42 is improved.
A good fingerprint image can be obtained.

By reducing the thickness of the elastic transparent optical member 40, the range of choice of materials can be widened. Further, if the peripheral edge portion 40a of the elastic transparent optical member 40 and the hard transparent optical member 21 are completely sealed, the liquid coupling material 41 can be used even with a liquid such as water, alcohol, ethylene glycol or the like that easily evaporates. .

[0042]

As described above, according to the fingerprint detecting device of the present invention, the transparent medium is a hard transparent optical member, an elastic transparent optical member disposed on the hard transparent optical member, and a hard transparent optical member. Therefore, a liquid coupling material filled between the elastic transparent optical members is used, and the optical reference surface is the surface opposite to the surface of the elastic optical member facing the hard transparent optical member. In addition, a good fingerprint image can be obtained even with dry fingers.
The optical reference surface can be easily replaced at low cost.

Further, since the elastic transparent optical member is made of a material having water repellency such as silicon rubber, a good fingerprint image can be obtained even with a wet finger.
Furthermore, since the liquid coupling material is silicone oil having a low vapor pressure, the silicone oil does not evaporate and can be reused.

Further, since the concave portion matching the shape of the finger to be pressed is formed on the transparent elastic optical member, the adhesion between the finger and the optical reference surface is improved, so that a good fingerprint image can be obtained. .

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a main part configuration of a first embodiment of the present invention.

FIG. 2 is a diagram illustrating an operation in FIG.

FIG. 3 is a cross-sectional configuration diagram of a main part of a second embodiment of the present invention.

FIG. 4 is a cross-sectional configuration diagram of main parts of a third embodiment of the present invention.

FIG. 5 is a diagram illustrating the principle of fingerprint detection.

FIG. 6 is a diagram for explaining light reflection at ridges and valleys of the fingerprint in FIG.

FIG. 7 is a configuration diagram of a main part of a conventional total reflection fingerprint detection device.

FIG. 8 is a configuration diagram of a main part of a conventional optical path separation type fingerprint detection device.

[Explanation of symbols]

 20 Transparent Medium 21 Hard Transparent Optical Member 22 Elastic Transparent Optical Member 23 Liquid Coupling Material 24 Optical Reference Surface

Claims (5)

[Claims] 1. A finger is pressed against an optical reference surface formed on a transparent medium, light is applied to the optical reference surface through the transparent medium, and a fingerprint of the finger is detected from reflected light or scattered light. In the fingerprint detection device, as the transparent medium, a hard transparent optical member, an elastic transparent optical member disposed on the hard transparent optical member, the hard transparent optical member, and a liquid filled between the elastic transparent optical members. A fingerprint detecting device, wherein a coupling material is used, and the optical reference surface is a surface opposite to a surface of the elastic optical member facing the hard transparent optical member. 2. The fingerprint detecting device according to claim 1, wherein the elastic transparent member has water repellency. 3. The fingerprint detecting device according to claim 1, wherein the elastic transparent member is silicon rubber. 4. The fingerprint detecting device according to claim 1, wherein the liquid coupling material is silicone oil. 5. The fingerprint detecting device according to claim 1, wherein a concave portion matching the shape of a finger to be pressed is formed on the transparent elastic optical member.