JP2000030034A - Fingerprint picture inputting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an economical and thin fingerprint picture inputting device capable obtaining a picture of rugged pattern such as a finger print of a comparatively large range with a high resolution and contrast. SOLUTION: This device is provided with a linear light source 1, a first light guiding plate 2A transmitting light emitted from the light source 1 while repeating total reflection, a first light branching plate 3A being in close contact with one surface 2a of the plate 2A and provided with a defractive index varying means at a previously fixed interval, a second light guiding plate 2B being in close contact with the other surface 2b of the plate 3A and guiding light while repeating total reflection, a second light branching plate 3A being in close contact with the other surface 2c of the plate 2B and provided with a defractive index varying means at a previously fixed interval, a photodetective element 52 photodetecting light emitted from the other end face 2e of the plate 2B and a control circuit 6 processing information from the element 52 to read fingerprint picture information by bringing a finger into contact with the other surface 2d of the plate 3B.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fingerprint image input device, and more particularly to a fingerprint image input device capable of obtaining a thin and clear fingerprint image.

[0002]

2. Description of the Related Art Attention has been focused on biometric information having the highest security as a personal identification technique used for access control and cash services. Until now, information on fingerprints and other uneven surfaces has been input by applying ink and stamping it once on paper, and then inputting it using an image sensor, or using glass and air using an optical element such as a prism. There is a method of immediately obtaining a concavo-convex pattern by irradiating a light beam at an angle equal to or greater than the critical angle to the interface. The present invention relates to an apparatus for immediately detecting information on an uneven surface using the latter optical element.

FIG. 11 shows an example of input means using a prism according to the prior art, and is a principle diagram of a system called a total reflection method. In FIG. 11, a fingerprint (irregular pattern) on the surface of the finger 9 is brought into contact with the oblique side of the prism 81, and when the irradiation light from the light source 1 is incident on the oblique side at a critical angle or more, the incident light at the convex 92 of the fingerprint Are scattered, and are totally reflected at the interface with the air at the concave portion 91 and are incident on the detector 55 such as an image sensor, so that an uneven pattern such as a fingerprint can be detected.
However, due to the leakage light due to multiple reflection, the scattered light from the concave portion 91 also reaches the detector 55, and there is a problem that the contrast of the concavo-convex pattern is reduced.

As a means for solving such a problem, Japanese Patent Publication No.
1-49997 "Uneven surface information detection device" is disclosed. Figure
In 12, the light source 1 irradiates the corresponding uneven surface with the uneven surface such as a fingerprint pressed against the transparent flat plate 82, and the light reflected by the convex portion 92 of the uneven surface and the light reflected by the concave portion 91 are emitted. Then, the subsequent light paths are completely different. That is, the light scattered by the concave portion 91 enters the transparent flat plate 82, is refracted, and then exits the transparent flat plate 82 again. At this time, according to Snell's law, all light is emitted from the transparent flat plate 82 in parallel with the angle of incidence on the transparent flat plate 82. On the other hand, the light scattered by the convex portion 92 emits a component smaller than the critical angle to the lower part of the transparent flat plate 82, but the light having a critical angle or more is an interface between the transparent flat plate 82 and the air (transparent flat plate /
The total reflection is repeated at the air interface) and propagates through the transparent flat plate 82. That is, the transparent flat plate / air interface below the transparent flat plate 82 functions as a filter that discriminates information on the concave portions 91 and information on the convex portions 92. Therefore, since all the light scattered by the concave portions 91 is emitted from the transparent flat plate 82, the light beam propagating in the transparent flat plate 82 is information only from the convex portions 92. Good concavo-convex pattern information can be obtained.

When the light which has been totally reflected and propagated in the transparent flat plate 82 reaches the position of the optical element 53, the condition of total reflection is broken, and the light enters the optical element 53 at the interface with the optical element 53. Outgoing light to the outside. Then, the external detector 55 can detect the pattern information only from the convex portions 92. In order to extract the light that has been repeatedly subjected to total reflection in the transparent flat plate 82 to the outside, it is sufficient if the condition for total reflection is broken.
For example, a hologram or a prism 54 shown in FIG.

[0006]

As described above, in a state where the uneven surface such as a fingerprint is pressed against the transparent flat plate, the light is irradiated onto the uneven surface by the light source, and the light having a critical angle or more scattered by the convex portion is transparent. In the related art in which total reflection is repeated at an interface between a flat plate and air and propagated and detected in the transparent flat plate, the transparent flat plate / air interface below the transparent flat plate discriminates information on concave portions and information on convex portions. Since the light acts as a filter and all the light scattered by the concave portion is emitted from the transparent flat plate, the light propagating in the transparent flat plate is information from only the convex portion, so that uneven pattern information with good contrast can be obtained. However, the light that propagates by being totally reflected in the transparent flat plate from the convex portion is detected by light having a critical angle or more at the transparent flat plate / air interface propagating in the transparent flat plate.

That is, when detecting a concavo-convex pattern such as a fingerprint in a relatively wide range, light having a critical angle or more is detected. Therefore, total reflection is repeated, and the optical path of light having a critical angle or more is detected at a position detected by an optical element. A light dispersion phenomenon occurs due to the difference in length, and information on adjacent protrusions affects each other, deteriorating the contrast of the concavo-convex pattern. Further, in the above-mentioned conventional technology, a laser beam is required as a light source, and a detector for detecting pattern information requires a two-dimensional sensor, for example, an area CCD, which is a factor of cost increase.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to solve the above-mentioned problems and to provide a relatively wide range image of a concavo-convex pattern such as a fingerprint with high resolution and high contrast. Another object of the present invention is to provide an economical and thin fingerprint image input device.

[0009]

In order to achieve the above object, according to the present invention, there is provided a linear light source, a first light guide plate for guiding light emitted from the light source while repeating total reflection, and A first light splitting plate which is in close contact with one surface of the first light guide plate and has a refractive index changing means at a predetermined interval; and which is in close contact with the other surface of the first light splitting plate and repeats total reflection of light. A second light guide plate that guides light while the second light guide plate is in close contact with the other surface of the second light guide plate, the second light branch plate including a refractive index changing unit at a predetermined interval, and the other end surface of the second light guide plate And a control circuit for processing information from the light receiving element.

[0010] With this configuration, fingerprint image information from a finger in contact with the other surface of the second optical branching plate can be read as follows. That is, the first and second optical splitters are:
The refractive index of the light splitting plate at the position designated by the control signal from the control circuit is increased, and the refractive index at other positions is kept small. As a result, at positions other than the position designated by the control signal, the first
Alternatively, the second light guide plate totally reflects light incident at a critical angle or more and propagates through the light guide plate. Then, when the light reaches the position specified by the control signal, the condition of total reflection between the light branch plate and the light guide plate that is in close contact is broken, and the light branches and enters the close light branch plate.

That is, the light emitted from the light source and incident on the first light guide plate travels while repeating total reflection within a range where the refractive index of the first light branch plate is small, and reaches a position (refractive index) designated by the control signal. In (large), the light is incident on the first light splitting plate, and subsequently, this light exits the first light splitting plate and is incident on the second light guide plate. Then, within the range where the refractive index of the second light branching plate is small, this light travels while repeating total reflection in the second light guide plate, and enters the second light branching plate when the refractive index of the second light branching plate is large. Then, this light arrives at the concavo-convex pattern of the fingerprint image of the finger in contact with the other surface of the second light branch plate.

Then, this light is totally reflected in the concave portions of the concave and convex pattern. Since the refractive indexes of the first and second light branching plates are kept small thereafter, the light is repeatedly reflected in the second light guide plate while repeating the total reflection. The light reaches the end face of the second light guide plate, exits the second light guide plate, and is detected by the light receiving element. This light is scattered at the convex portions of the concave / convex pattern and enters the second light guide plate. Of the scattered light, light within the critical angle is dispersed outside via the second light guide plate, the first light branch plate, and the first light guide plate. Light that travels in a certain direction at or above the critical angle is detected by the light receiving element. The light traveling in the opposite direction to the light receiving element
The light is absorbed by the light absorption treatment on the end face of the light guide plate. That is, as for the optical signal received by the light receiving element, an optical signal of strong total reflection is detected in the concave portion of the concave-convex pattern, and a weak optical signal scattered is detected in the convex portion. Can be.

Further, the first light guide plate can be formed by arranging and fusing a plurality of optical fibers in a line, and polishing one surface of this plane smoothly until it reaches the core portion. In addition, the second light guide plate has a plurality of optical fibers arranged in a line and fused, and both surfaces of this plane are polished smoothly until reaching the core portion, and one end surface (the end surface opposite to the light receiving element). ) Can be constituted by performing an absorption treatment.

The first and second optical branching plates are made of a glass substrate, a pair of transparent electrodes arranged on the glass substrate at a predetermined interval and facing each other, and filled between the transparent electrodes. And a liquid crystal. Further, the first and second light branching plates are arranged with a plurality of transparent pipes in a direction orthogonal to the optical fiber, and filled with a transparent gas or liquid having a different refractive index in the pipes,
The filling in the pipe can be sequentially switched by the control signal.

With this configuration, the light emitted from the light source and incident on the first light guide plate travels through the optical fiber to read the concave / convex pattern information at the position designated by the control signal from the control circuit. In the optical fiber, and can be detected by the light receiving element. In other words, it is possible to read the uneven pattern information such as fingerprints with high resolution by the distance between the optical fibers of the light guide plate and the distance between the transparent electrodes or the distance between the transparent pipes that greatly change the refractive index of the light branching plate.

The first and second optical branching plates are provided with transparent electrodes arranged at predetermined intervals on a polished surface of a light guide plate polished smoothly, and a glass substrate opposed to the transparent electrodes. The light guide plate and the light splitting plate can be integrally formed by including the transparent electrode disposed thereon and the liquid crystal filled between the transparent electrodes. Further, the first and second light branching plates can be arranged such that transparent electrodes alternately arranged at predetermined intervals on both surfaces of a pair of auxiliary glass substrates are opposed to each other.

Further, the first and second light splitting plates have a second transparent electrode disposed on a glass substrate, the second transparent electrode is insulated, and the first transparent electrode is disposed at a predetermined interval. And a pair of substrates arranged in opposition to each other,
And a liquid crystal filled between the transparent electrodes. In addition, the first and second optical branching plates are provided with a second transparent electrode disposed on a polished surface of a light guide plate polished smoothly, and the second transparent electrode is insulated and predetermined. A first transparent electrode disposed at an interval, and a second transparent electrode disposed opposite to the first transparent electrode, disposed on a glass substrate, and insulated from the second transparent electrode, and at a predetermined interval. The light guide plate and the light splitting plate can be integrally formed by including the substrate on which the first transparent electrodes are arranged and the liquid crystal filled between the first transparent electrodes.

Further, the pair of transparent electrodes can be arranged in a band at predetermined intervals in a direction orthogonal to the optical fiber. Further, the change in the refractive index of the first and second optical splitters is performed by setting a predetermined constant interval between the first and second optical splitters from one end face to the other end face. Can be changed and swept toward.

The optical fibers constituting the first and second light guide plates can be constructed by fusing optical fibers having a cladding diameter or an outer diameter of about 50 μm. Further, the interval between the strip-shaped transparent electrodes arranged on the first and second light branching plates can be arranged around 50 μm. Further, the interval between the transparent pipes arranged on the first and second light branching plates can be arranged around 50 μm.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a structural view of a principal part of a fingerprint image input device according to one embodiment of the present invention as viewed from the side, FIG. 2 is a plan view of FIG. 1, and FIG. FIG. 4 is a plan view and a cross-sectional view of a light splitting plate as one embodiment, FIG. 5 is a cross-sectional view of a liquid crystal light splitting plate as one embodiment, FIG. 6 is a characteristic diagram of a refractive index, and FIG. FIG. 8 is a cross-sectional view of a liquid crystal type light splitting plate as another embodiment, FIG. 8 is a cross-sectional view of a liquid crystal type light splitting plate as another embodiment, FIG. 9 is a characteristic diagram of a refractive index, and FIG. FIG. 14 is a configuration diagram of a main part of a light splitting plate as an example, and the same members corresponding to FIGS. 11 to 13 are denoted by the same reference numerals.

First, the main configuration of the present invention will be described with reference to FIG. 1 and FIG. In FIG. 1 (FIG. 2), the fingerprint image input apparatus includes a light source 1 for irradiating linearly distributed light, and a light emitted from the light source 1 converted into a parallel beam in a vertical direction by a lens 11, and Light guide plate 2A for guiding light while obliquely entering the light and repeating total reflection, and the first light guide plate
A first light splitting plate 3A provided with a refractive index changing means to be described later at a predetermined interval in close contact with one surface 2a of the 2A; A second light guide plate 2B that guides light while repeating the above, a second light branch plate 3B that is provided in close contact with the other surface 2c of the second light guide plate 2B and that has a refractive index changing means at a predetermined interval, The light guide plate 2B includes a light receiving element 52 that receives light emitted from the other end face 2e of the light guide plate 2B via a lens 51, and a control circuit 6 that processes information from the light receiving element 52.

With this configuration, the fingerprint image information from the finger 9 in contact with the other surface 2d of the second light branching plate 3B can be read as follows. The first optical splitter 3A and the second optical splitter 3B increase the refractive index of the optical splitter at a position (for example, 3-f / 3A, 3-g / 3B) specified by a control signal from the control circuit 6. And other positions (3-1 to 3-k excluding (3-f / 3A, 3-g / 3B))
Is kept small. As a result, the first optical splitter 3A
The first light guide plate 2A, which is in close contact with the light source, totally reflects light incident at a critical angle or more at positions other than the position 3-f specified by the control signal from the control circuit 6, and furthermore, the first and second light branch plates. 3A, 3
The second light guide plate 2B close to B is located at the position specified by the control signal.
At places other than 3-f and 3-g, light incident at a critical angle or more is totally reflected and propagates through the light guide plates (2A, 2B). Then, when the light reaches the position (3-f / 3A, 3-g / 3B) specified by the control signal, the light splitter plate (3A, 3B) and the light guide plate (2A, 2B) that are in close contact with the light splitter plate (3A, 3B). The reflection condition is broken, and the light is branched and incident into the closely spaced light branching plates (3A, 3B).

That is, the light emitted from the light source and incident on the first light guide plate 2A travels while repeating total reflection within the range where the refractive index of the first light branching plate 3A is small, and moves to the position 3 designated by the control signal. At -f (high refractive index), the light is incident on the first light splitting plate 3A, and then this light exits the first light splitting plate 3A and is incident on the second light guide plate 2B. Then, this light travels while repeating total reflection in the second light guide plate 2B within a range where the refractive index of the second light branching plate 3A is small, and the second light branching at the large refractive index of the second light branching plate 3B. Is incident on the plate 3B, and this light is transmitted to the other surface 2d of the second light branching plate 3B.
Arrives at the concavo-convex pattern of the fingerprint image of the finger 9 in contact with.

Then, in the concave portion 91 of the concave / convex pattern, the second
This light is totally reflected at the interface between the other surface 2d of the light splitting plate 3B and the air, and thereafter, since the refractive indexes of the first and second light splitting plates are kept small, the inside of the second light guide plate 2B is The second light guide plate 2B reaches the end face 2e of the second light guide plate 2B while repeating total reflection.
And is condensed by a lens 51 to receive a light receiving element 52, for example,
Detected by a one-dimensional sensor, line CCD, etc. This light is scattered at the convex portion 92 of the concave / convex pattern and enters the second light guide plate 2B. Of the scattered light, light within the critical angle is the second
The light is absorbed or dispersed outside through the light guide plate 2B, the first light branch plate 3A, and the first light guide plate 2A. Above the critical angle, the light receiving element 52
Light traveling in a certain direction is similarly detected by the light receiving element 52. The light traveling in the opposite direction to the light receiving element 52 is absorbed by the light absorbing process on the end face 2f of the second light guide plate 2B. That is, as for the optical signal received by the light receiving element 52, the optical signal of strong total reflection is detected in the concave portion 91 of the concave-convex pattern, and the weak optical signal scattered is detected in the convex portion 92. Can be well identified.

In FIG. 2, light emitted from a linear light source 1 is transmitted through a lens 11 to a plurality of optical fibers (21, 22 to 2).
k) are arranged in a line and obliquely enter the first light guide plate 2A fused from below or above. This light is set so that the light in the first light guide plate 2A is equal to or larger than the critical angle with respect to the surface 2a in close contact with the first light branch plate 3A. As a result, each optical fiber (21,22 ~
The light incident on 2k) travels while repeating total internal reflection in the optical fiber. Then, the position 3-f of the first optical branching plate 3A whose refractive index is set to be large by the signal of the control circuit 6.
The light in each optical fiber (21, 22-2k) passes through the position 3-f of the corresponding first optical branching plate 3A and the corresponding optical fiber (21, 22-2k) of the second light guide plate 2B. At the position 3-g of the second light branching plate 3B, and arrives at the concavo-convex pattern of the fingerprint image of the finger 9 in contact with the other surface 2d of the second light branching plate 3B.

This light is emitted according to the state of the uneven pattern.
As described above, the light again enters the corresponding optical fiber (21, 22 to 2k) as the total reflection light or the scattered light. In particular, since the totally reflected light having strong light is the concave portion 91 on the other surface 2d of the second optical branching plate 3B, the light totally reflected here is directly used as the original optical fiber (2).
1,22〜2k). Since the scattered light is scattered by the convex portion 92, the scattered light travels not only to the original optical fiber (21, 22 to 2k), but also to the direction of other optical fibers in the vicinity. In order to remove this light, it is conceivable to insert a light absorber between the optical fibers when the optical fibers are fused. However, in general, the scattered light itself has a light intensity lower than that of the totally reflected light, so that the uneven pattern information can be sufficiently identified with good contrast. Since the information obtained from the inspection position 3-g of the concavo-convex pattern of the fingerprint image of the finger 9 is obtained for each optical fiber (21, 22 to 2k), the inspection position 3-g is controlled by the control circuit 6. By performing the sweeping with the control signal, the uneven pattern of the fingerprint image of the finger 9 can be inspected with high resolution and sufficient contrast.

[0027]

Embodiment 1 An embodiment of the light guide plates 2A and 2B will be described with reference to FIG.
In FIG. 3, the first light guide plate 2A includes a plurality of optical fibers (2
1,22-2k) are aligned and fused (see FIG. 3 (B)).
One surface 2a (see FIG. 3A) of the fused plane is polished until it reaches the core portion smoothly. The second light guide plate 2B is formed by fusing a plurality of optical fibers (21, 22 to 2k) in a line and fusing both surfaces (2b, 2c).
(See FIG. 3 (C)) is polished until it reaches the core portion smoothly, and the end face 2f (the end face opposite to the light receiving element 52) is subjected to light absorption processing.

With this configuration, the light emitted from the light source 1 and incident on the first light guide plate 2A travels through the optical fibers (21, 22 to 2k) and moves to the position designated by the control signal from the control circuit 6. Of the concave and convex pattern information of the second
The light travels through the optical fibers (21, 22 to 2k) of the light guide plate 2B and can be detected by the light receiving element 52. That is, the distance between the optical fibers (21, 22-2k) of the light guide plates 2A, 2B and the light splitting plate 3 shown in FIG.
The distance between the transparent electrodes 32 (3-1, 3,
3-2 to 3-K) or the interval (4-
1,4-2 to 4-K), it is possible to read uneven pattern information such as fingerprints while maintaining high resolution.

[0029]

[Embodiment 2] Embodiments 2 to 4 of the light splitting plates 3A and 3B having the refractive index changing means will be described with reference to FIGS. In FIG. 4, a sectional view of the light splitting plates 3A and 3B is shown in FIG. 4A, and a front view is shown in FIG. 4B. The first and second optical splitters 3A and 3B
Is disposed on the glass substrate 31 at a predetermined interval (position number) (3-1, 3-2,... 3-f, 3-g, 3-k) on the glass substrate 31 so as to face each other. It comprises a pair of electrodes 32 and a liquid crystal filled between the transparent electrodes 32.

In the example shown, the electrodes 32 are vertically numbered.
(3-1,3-2..3-f, 3-g.3-k), and a knitted fiber array in which a plurality of optical fibers (21, 22-2k) are arranged in a row in the left-right direction. With the light plate, rectangular coordinates can be formed. Although the arrangement of the electrodes 32 is shown perpendicular to the optical axis of the optical fiber, the electrodes 32 may be formed diagonally or in the shape of a square as needed.

FIGS. 5 and 6 are diagrams for explaining the refractive index changing means. FIG. 5 shows a general liquid crystal device. In a state where no voltage is applied between the opposing electrodes 32 of the liquid crystal (FIG. 6A), the liquid crystal molecules are aligned in the horizontal direction, and the refractive index n at this time is as shown in FIG. As shown by the solid line, it is constant in a state where the refractive index is high. In a state where a voltage is applied between the opposing electrodes 32 ((C) in FIG. 6), the electrode 32 to which the voltage is applied is applied.
In between, the alignment state of the liquid crystal molecules changes in the vertical direction and the refractive index n
Becomes smaller (FIG. 6D). Where there is no electrode 32, it changes with some influence of the electric field by the peripheral electrodes 32, but the central portion has a relatively high refractive index n.

In another embodiment, the first and second
The light splitting plates 3A and 3B are light guide plates 2A and 2B
No. (3-a) at predetermined intervals on the polished surfaces (2a, 2c)
A transparent electrode 32 arranged in (1,3-2 ... 3-f, 3-g-3-k);
A transparent electrode 32 disposed on the glass substrate 31 facing the transparent electrode 32, and a liquid crystal filled between the transparent electrodes 32
34, the light guide plates 2A, 2B and the light branch plates 3A, 3B can be integrally formed.

In such a configuration, the glass layers 31 of the light branching plates 3A and 3B which are in close contact with the light guide plates 2A and 2B are different from the above configuration.
Can be omitted. As a result, the thickness of the light branching plates 3A and 3B can be reduced, and light is accordingly reduced.
Leakage of light from an optical fiber to another optical fiber when passing through B can be reduced. FIG. 7 shows an embodiment of the refractive index changing means for realizing such characteristics. In FIG. 7, the light splitting plates 3A and 3B are provided at predetermined intervals (position numbers) (3-1, 3-2) with a slight overlap on both surfaces of the glass substrate 31 and the pair of auxiliary glass substrates 31A alternately. ..3-f, 3-
g ・ 3-k) and the transparent electrodes 32,3
3 and a liquid crystal 34 filled therebetween.

In such a configuration, for example, the electrode position 3-
To increase the refractive index n only at the point f and decrease the refractive index n at other points, apply the voltage to all the electrodes at the other points without applying the voltage only to the electrode at the electrode position 3-f. This can be achieved. That is, the light coming from the light guide plates 2A and 2B is totally reflected at the interface with the liquid crystal and returned to the light guide plates 2A and 2B where the refractive index n of the liquid crystal is small. Also,
Where the refractive index n is high, such as at the electrode position 3-f, the light guide plates 2A, 2A
Light coming from B passes through the liquid crystal and passes through the opposite side of the light splitters 3A and 3B.

[0035]

Embodiment 3 FIG. 8 shows another embodiment of the refractive index changing means. In FIG. 8, the first and second optical splitters 3A and 3B are
A second transparent electrode 35 is disposed on the entire surface of one side of the glass substrate 31,
The first transparent electrodes 35 are insulated, and the first transparent electrodes 32 are arranged opposite to each other at predetermined intervals to form a pair, and a liquid crystal 34 filled between the first transparent electrodes 32 is provided. Can be provided.

In this configuration, as shown in FIG. 9, a voltage is applied between the second transparent electrodes 35 (FIG. 9A).
In this state, since the electric field is applied to the entire area of the liquid crystal 34, the liquid crystal molecule alignment state is in the vertical direction, and the refractive index n at this time has a small value as shown in FIG. 9B. Become. Next, as shown in FIG. 9C, for example, when a reverse voltage is applied only to the electrode 32 at the electrode position 3-f and the electric field at this position is canceled out, the electrode position 3-f is removed. Of the liquid crystal molecules in the horizontal direction, the refractive index n at this time is shown in FIG.
As shown in FIG. In this method, the influence of the position of the electrode 32 on the total reflection of the light guide plates 2A and 2B can be made uniform.

Further, as another embodiment of the refractive index changing means, the first and second light branching plates 3A, 3B are provided on the polished surfaces 2a, 2c of the light guide plates 2A, 2B which are polished smoothly. Second transparent electrode
A first transparent electrode 32 disposed at a predetermined interval is disposed on the second transparent electrode 35 on which the second transparent electrode 35 is insulated.
And the glass substrate 31 which is disposed so as to face the first transparent electrode 32.
A substrate on which a second transparent electrode 35 is disposed, the second transparent electrode 35 is insulated, and the first transparent electrodes 32 are disposed at predetermined intervals; The light guide plate and the light splitting plate can be integrally configured by including the liquid crystal 34 filled in the light guide plate.

In this configuration, the light branching plates 3A, 3B which are in close contact with the light guide plates 2A, 2B are different from the configuration described in FIG.
The glass layer 31 can be omitted. As a result, the thickness of the optical splitters 3A and 3B can be reduced, and the leakage of light from the optical fiber to other optical fibers when light passes through the optical splitters 3A and 3B can be reduced accordingly. be able to.

[0039]

[Embodiment 4] In FIG. 10, first and second optical splitters are shown.
4A and 4B, a plurality of transparent pipes (4-1, 4-2,..., 4-k) are arranged in a direction orthogonal to the optical fibers 21, 22,. -2,... 4-k) can be filled with a transparent gas or liquid having a different refractive index, and the filling in the pipe can be sequentially switched by a control signal.

With this configuration, the light emitted from the light source 1 and incident on the first light guide plate 2A travels in the optical fiber (21 to 2k), and moves to a position designated by a control signal from the control circuit 6, for example, , 4-g is read and travels through the optical fibers (21 to 2k) of the corresponding second light guide plate 2B again and can be detected by the light receiving element 52. That is, the distance between the optical fibers 21 to 2k of the light guide plates 2A and 2B and the light branch plates 4A and 4
The uneven pattern information such as fingerprints can be read with high resolution at the interval of the transparent pipe that greatly changes the refractive index of B.

In FIG. 10, pipes (4-1, 4-2,... 4-k)
The switching control of the transparent gas or liquid filler having a different refractive index in the inside is performed by, for example, controlling the opening and closing of the valve 42 by a control signal from the control circuit 6, blowing air from the air pump 43,
Alternatively, after receiving water from the water pump 44, the corresponding pipe (4-1, 4-2,..., 4-k) is filled with a transparent gas or liquid having a different refractive index. In addition, by returning the water supply system to the water tank 45 through the rectifying valve 46 for backflow prevention,
Water can be circulated and used.

In the filling / switching control, the pipes (4-1, 4-2,..., 4-k) are sequentially and repeatedly controlled. Further, the change in the refractive index of the first and second optical splitters 3A and 3B is performed at a predetermined fixed interval between the first optical splitter 3A and the second optical splitter 3B. It is possible to change and sweep from one end face to the other end face. In the example shown in FIG. 1, the light emitted from the first light splitting plate 3A has an interval in which the light passes through the second light guide plate 2B and is incident on the second light splitting plate 3B without being totally reflected. . This interval is the second light guide plate 2B
And a value set beyond the critical angle at which the light is totally reflected in the light guide plates 2A and 2B.

In one embodiment of the present invention, the optical fibers forming the first and second light guide plates 2A and 2B are formed by fusing optical fibers having a cladding diameter or an outer diameter of about 50 μm. The interval between the strip-shaped transparent electrodes disposed on the first and second light branching plates 3A and 3B is set to about 50 μm. Alternatively, the interval between the transparent pipes arranged on the first and second light branching plates 4A and 4B is arranged around 50 μm. As a result, the fingerprint image of the finger 9 has a resolution of about 50 μm,
That is, 500 DPI can be read, and personal information can be accurately identified.

[0044]

As described above, according to the present invention, a light guide plate formed by arranging a plurality of optical fibers in a line and fusing them,
By using the first light splitting plate having the refractive index changing means at predetermined intervals, the image of the concavo-convex pattern such as a fingerprint in a relatively wide range also has a high resolution of 500 DPI and a high contrast, and is economical. A thin fingerprint image input device can be provided.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a main part of a fingerprint image input device viewed from a side as an embodiment of the present invention;

FIG. 2 is a plan view of FIG. 1;

FIG. 3 is a plan view and a cross-sectional view of a light guide plate.

FIG. 4 is a plan view and a cross-sectional view of a light splitting plate as one embodiment.

FIG. 5 is a cross-sectional view of a liquid crystal type light splitting plate as one embodiment.

FIG. 6 is a characteristic diagram of a refractive index.

FIG. 7 is a sectional view of a liquid crystal type light splitting plate as another embodiment.

FIG. 8 is a sectional view of a liquid crystal type light splitting plate as another embodiment.

FIG. 9 is a characteristic diagram of a refractive index.

FIG. 10 is a configuration diagram of a main part of an optical branching plate as another embodiment.

FIG. 11 is a diagram illustrating the principle of the total reflection method according to the related art.

FIG. 12 is a diagram showing a concavo-convex surface information detection device according to a conventional technique.

FIG. 13 is a diagram showing another uneven surface information detection device according to the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light source 11,51 Lens 2A, 2B Light guide plate 2a, 2b, 2c Polished surface 2d Thickened surface of inspection object 2e, 2f End surface 21 ～ 2n Optical fiber 3A, 3B, 4A, 4B Optical branching plate 31,31A Glass layer 32 , 33 Transparent electrode 34 Liquid crystal 35 2nd transparent electrode 3-1,3-2, ... 3-f, 3-g, ... 3-k Electrode position 41 Transparent pipe 42 Valve 43 Air pump 44 Water pump 45 Water tank 46 Rectifier valve 4-1,4-2, ... 4-f, 4-g, ... 4-k Pipe position 52,55 Receiver 53 Optical element 54,81 Prism 6 Control circuit 82 Transparent flat plate 9 Finger 91 Recess 92 Convex part n Refractive index

Claims (14)

[Claims] 1. A linear light source, a first light guide plate for guiding light emitted from the light source while repeating total reflection, and a predetermined distance in close contact with one surface of the first light guide plate A first light splitting plate having a refractive index changing means, a second light guiding plate which is in close contact with the other surface of the first light splitting plate and guides light while repeating total reflection, and the other of the second light guiding plate A second light branching plate which is provided with a refractive index changing means at a predetermined interval in close contact with the surface of the second light guide plate, a light receiving element for receiving light emitted from the other end face of the second light guide plate, and information from the light receiving element A fingerprint image input device, comprising: a control circuit for processing the image data; and reading a fingerprint image information by contacting a finger with the other surface of the second light splitting plate. 2. The fingerprint image input device according to claim 1, wherein the first light guide plate has a plurality of optical fibers arranged in a line and fused, and one surface of the plane is smoothed until it reaches the core portion. A fingerprint image input device characterized by being polished and formed. 3. The fingerprint image input device according to claim 1, wherein the second light guide plate has a plurality of optical fibers arranged in a line and fused, and both surfaces of this plane are used as a core. A fingerprint image input device, wherein the fingerprint image input device is polished smoothly until it reaches the surface, and one end face (the end face opposite to the light receiving element) is subjected to light absorption processing. 4. The fingerprint image input device according to claim 1, wherein the first and second light splitting plates are a glass substrate and a predetermined one on the glass substrate. A fingerprint image input device, comprising: a pair of transparent electrodes arranged at intervals and facing each other; and a liquid crystal filled between the transparent electrodes. 5. The fingerprint image input device according to claim 1, wherein the first and second light branching plates are provided in advance on a polished surface of a light guide plate polished smoothly. A light guide plate and a light branch comprising a transparent electrode disposed at a predetermined interval, a transparent electrode disposed on a glass substrate facing the transparent electrode, and a liquid crystal filled between the transparent electrodes. A fingerprint image input device, wherein the fingerprint image input device is formed integrally with a plate. 6. The fingerprint image input device according to claim 4, wherein the first and second light splitting plates are arranged at predetermined intervals alternately on both surfaces of a pair of auxiliary glass substrates. A fingerprint image input device, wherein the fingerprint image input device is disposed facing the fingerprint image input device. 7. The fingerprint image input device according to claim 4, wherein the first and second light splitting plates are provided on a glass substrate.
A transparent electrode is arranged, the second transparent electrode is insulated, and the first transparent electrodes are arranged at a predetermined interval. A fingerprint image input device, comprising: a liquid crystal to be filled. 8. The fingerprint image input device according to claim 5, wherein the first and second light splitting plates have a second transparent electrode disposed on a polished surface of a light guide plate polished smoothly. After the second transparent electrode is insulated, a first transparent electrode is disposed at a predetermined interval, and the second transparent electrode is disposed to face the first transparent electrode, and the second transparent electrode is disposed on a glass substrate. A light guide plate and a light splitting plate, comprising: a substrate in which first transparent electrodes are arranged at predetermined intervals after insulating the transparent electrodes; and a liquid crystal filled between the first transparent electrodes. And a fingerprint image input device. 9. The fingerprint image input device according to claim 4, wherein the pair of transparent electrodes are arranged in a band at a predetermined interval in a direction orthogonal to the optical fiber. A fingerprint image input device, characterized in that: 10. The fingerprint image input device according to claim 1, wherein the first and second light branching plates are configured to connect a plurality of transparent pipes in a direction orthogonal to the optical fiber. A fingerprint image input device, comprising: disposing a transparent gas or liquid having a different refractive index in a pipe, and sequentially switching the filler in the pipe according to a control signal. 11. The fingerprint image input device according to claim 1, wherein the change in the refractive index of the first and second light branching plates is the first and second light branching. A fingerprint image input device characterized in that the fingerprint image input device changes and sweeps from one end face to the other end face with a predetermined constant interval between the fingerprint image and the plate. 12. The fingerprint image input device according to claim 2, wherein the optical fibers constituting the first and second light guide plates are formed by melting an optical fiber having a cladding diameter or an outer diameter of about 50 μm. A fingerprint image input device characterized by being worn on. 13. The fingerprint image input device according to claim 4, wherein the interval between the strip-shaped transparent electrodes disposed on the first and second light splitting plates is about 50 μm. A fingerprint image input device, which is arranged. 14. The fingerprint image input device according to claim 10, wherein the interval between the transparent pipes arranged on the first and second light branching plates is arranged around 50 μm. apparatus.