JP3205445B2 - Fingerprint detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of pressing a finger on an optical reference surface formed on a transparent medium, irradiating the optical reference surface with light through the transparent medium, and converting the reflected light or scattered light into light. The present invention relates to a fingerprint detection device that detects a fingerprint of a finger.

At present, personal identification numbers, I
D cards and the like are widely used. However, as the value of information further increases, a sophisticated personal identification method is required. Therefore, methods for performing personal identification from physical characteristics have been developed.

[0003] As a method of identifying an individual with physical characteristics, there are a fingerprint, a voiceprint, a retina and the like. Of these methods, the fingerprint method differs in fingerprint pattern between individuals.

[0004] It does not change for a lifetime. There is no risk of loss. It is difficult to forge.

There is no hassle in use. Retrieval of the pattern is relatively simple. It is the most expected for such reasons.

[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 denotes a transparent medium such as glass or hard plastic having an optical reference surface 2 formed on one surface.

When the finger of the finger 3 is pressed against the optical reference surface 2 of the transparent medium 1, the portion in contact with the optical reference surface 2 is a ridge 4 of the fingerprint, and the ridge 4 between the fingerprint valley 5 and the optical reference surface 2. Has an intervening space.

Here, an optical reference surface 2 is interposed via a transparent medium 1.
6A, the incident light is scattered in all directions at the ridge 4 as shown in FIG. 6A, and the incident light is dispersed at the valley 5 as shown in FIG. The portion is specularly reflected on the optical reference surface 2. In order to increase the ratio of the regular reflection 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. In addition, since the intensity of the scattered light is different between the ridge 4 and the valley 5, the difference is detected to detect the scattered light.
The shape of the fingerprint can be recognized. In this case, the light and darkness is reversed from the case where the regular reflection light is used.

Next, the configuration of a conventional total reflection 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 converting light emitted from the light source 15 into parallel light are provided near the incident surface 13. And the light source 15
And the lens 16 are disposed such that incident light is totally reflected on the optical reference surface 12.

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

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

According to such a configuration, the background and the valley look dark, and the ridges look bright. By the way, the ridge of the fingerprint of the finger has fine irregularities. For this reason, when the finger 19 is pressed against the optical reference surface 12 of the fingerprint detection device, the ridge may appear to be broken at first. However, if the finger is kept pressed strongly against the optical reference surface 12, the fingerprint image gradually becomes clear within 1-2 seconds. This is because the finger 19 sweats and the unevenness of the ridge is filled with the sweat.

[0015]

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

The surface condition of a finger varies from person to person. A moderate amount of sweat fills the unevenness of the ridges and makes the fingerprint image good,
In the case of a wet finger person, there is a problem that a valley portion is filled with sweat due to excessive sweat and a good fingerprint image cannot be obtained.

If a scratch or the like is formed on the optical reference surface 12 for any reason, it is necessary to replace the transparent medium. However, the replacement requires assembly accuracy, and is difficult and expensive. In order to solve the problems described above, a silicone rubber coating is applied 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 an optimal hardness (elasticity). Further, the regeneration when stains and scratches occur requires time and labor. Therefore, the problem still exists.

The present invention has been made in view of the above problems, and its object is to obtain a good fingerprint image regardless of environmental conditions, and even for a dry finger or a wet finger. The present invention is to provide a fingerprint detection device that can be used.

It is another object of the present invention to provide a fingerprint detecting device whose optical reference surface can be easily and inexpensively replaced.

[0021]

According to the first aspect of the present invention, 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 that detects the fingerprint of the finger from reflected light or scattered light, as the transparent medium,
Using 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, the optical reference The surface is the surface of the elastic optical member opposite to the surface facing the hard transparent optical member.

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

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

[0024]

According to the first aspect of the present invention, there is provided a fingerprint detecting apparatus comprising:
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 a dry finger.

Further, the elastic transparent optical member on which the optical reference surface is formed is disposed on the hard transparent optical member via a liquid coupling. Therefore, the replacement of the optical reference surface may be performed by replacing only the elastic transparent optical member or, in some cases, 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, even if it is a wet finger, sweat concentrates on the ridge portion, and a good fingerprint image can be obtained. Can be.

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

[0028]

Next, an embodiment of the present invention will be described with reference to the drawings. It should be noted that the present invention is an improvement of a transparent medium in a fingerprint detection device, and other photographing systems, light sources, and the like are the same, and therefore description thereof is omitted.

First, a transparent medium 20 according to a 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 was formed on the surface of the elastic optical member 22 opposite to the surface facing the hard transparent optical member 21.

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

As for the elastic transparent optical member 22, it is necessary to consider hardness, transparency, chemical resistance, weather resistance, abrasion resistance and the like. Further, in consideration of sweating from a finger, it is desirable to have water repellency. Further, the hardness is desirably 28 to 80 (JIS K6301). In consideration of these conditions, in this embodiment, silicone rubber and fluorine rubber were selected.

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

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

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

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

When the optical reference surface 24 is scratched 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.
Also, the liquid coupling material 23 is placed on the hard transparent optical member 21.
Is not left, a new hard transparent optical member 2
A few drops of the liquid coupling material 23 are dropped on 1, and the elastic transparent optical member 22 is placed. And the elastic transparent optical member 2
2, the air between the hard transparent optical member 21 and the elastic transparent optical member 22 is eliminated, and the liquid coupling 2
Both are optically coupled such that only 2 is present.

Therefore, only the elastic transparent optical member 22 or only the elastic transparent optical member 22 and the liquid coupling material 23 need to be replaced as compared with the conventional replacement of the entire transparent medium, and the replacement operation is simple and inexpensive. It 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 is used.
5 in that a concave portion 32 conforming to the shape of No. 5 is formed.

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

According to such a configuration, 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.

Further, by reducing the thickness of the elastic transparent optical member 40, the range of choice of the material can be expanded. Further, if the sealing between the peripheral edge portion 40a of the elastic transparent optical member 40 and the hard transparent optical member 21 is completely performed, the liquid coupling material 41 can be used even with a liquid that easily evaporates, such as water, alcohol, and ethylene glycol. .

[0042]

As described above, according to the fingerprint detecting apparatus of the present invention, as the transparent medium, a hard transparent optical member, an elastic transparent optical member provided on the hard transparent optical member, and a hard transparent optical member. By using a liquid coupling material filled between the elastic transparent optical members and using the optical reference surface as the surface opposite to the surface of the elastic optical member facing the hard transparent optical member, the environment is low in humidity. Even with a dry finger, a good fingerprint image can be obtained.
The optical reference surface can be easily and inexpensively replaced.

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.
Further, by using silicone oil having a low vapor pressure as the liquid coupling material, the silicone oil does not evaporate and can be reused.

In addition, by forming a concave portion on the transparent elastic optical member corresponding to the shape of the finger to be pressed, the adhesion between the finger and the optical reference surface is improved, so that a good fingerprint image can be obtained. .

[Brief description of the drawings]

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

FIG. 2 is a diagram for explaining the operation in FIG. 1;

FIG. 3 is a sectional view showing a main part of a second embodiment of the present invention.

FIG. 4 is a sectional view showing a main part of a third embodiment of the present invention.

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

FIG. 6 is a view for explaining light reflection at ridges and valleys of the fingerprint in FIG. 5;

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

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

[Explanation of symbols]

 Reference Signs List 20 transparent medium 21 hard transparent optical member 22 elastic transparent optical member 23 liquid coupling material 24 optical reference surface

Claims (5)

(57) [Claims] 1. A finger is pressed against an optical reference surface formed on a transparent medium, the optical reference surface is irradiated with light 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 provided on the hard transparent optical member, and a liquid filled between the hard transparent optical member and the elastic transparent optical member And a coupling member, wherein 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 detection device according to claim 1, wherein the elastic transparent member has water repellency. 3. The fingerprint detection device according to claim 1, wherein the elastic transparent member is made of silicon rubber. 4. The fingerprint detecting device according to claim 1, wherein said liquid coupling material is silicone oil. 5. The fingerprint detection device according to claim 1, wherein a concave portion is formed on the transparent elastic optical member so as to match a shape of a finger to be pressed.