JP2003323605A - Fingerprint reader - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fingerprint reader capable of realizing efficient fingerprint reading while enlarging the readable region of a fingerprint image. <P>SOLUTION: A light wave emitted by a light emitting part 11 is made incident from a side face 23 of a waveguide body 12, and repeatedly alternately and fully reflected between a first reflection face 21 and a second reflection face 22 in the waveguide body 12, and guided to the other side face 23. A plurality of regions irradiated with the light wave are formed at the first reflection face 21 side, and decided as readable regions. The light wave passing through the waveguide body 12 is transmitted to a light receiving part 13, and read as a fingerprint image. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fingerprint reader for reading a fingerprint and subjecting it to a predetermined process.

[0002]

2. Description of the Related Art In recent years, personal authentication technology based on so-called biometrics has attracted attention. Among them, fingerprint authentication is expected to be used in many situations because the psychological burden on the authenticated side is small. Conventionally, as a device for reading a fingerprint for fingerprint authentication, FIG.
As shown in (a), there is a device including a transparent triangular prism 1, a light source 2, and a two-dimensional image sensor 3. A light wave (a part of it) emitted from the light source 2 is totally reflected inside the reading surface R of the transparent triangular prism 1 and reaches the two-dimensional image sensor 3.

When the finger surface is placed on the reading surface R of the transparent triangular prism 1, the convex portion of the fingerprint comes into contact with the reading surface R and the concave portion does not come into contact with the reading surface R. (FIG. 17B). In a general glass material or the like, the portion where the finger is in contact with the reading surface R does not satisfy the total reflection condition, and the light wave is absorbed without being reflected in the portion. Therefore, the image formed by the light waves reaching the two-dimensional image sensor 3 becomes an image that is dark along the convex portions of the fingerprint (FIG. 18).

The image read by the two-dimensional image sensor 3 is output to an authentication device (not shown) as electrical image data. The authentication device stores a plurality of fingerprint image data to be authenticated in association with predetermined information, compares each fingerprint image data with the input image data,
If there is fingerprint image data that matches the input image data, information associated with the fingerprint image data is used to execute a predetermined process such as opening and closing a door.

[0005]

However, in the above conventional fingerprint reading device, the area of the fingerprint reading surface R is small and the degree of freedom of the finger contact position is low. Therefore, it cannot be applied to the case where the processing is different depending on where the finger is placed, and the usage scene is limited. Therefore, it suffices to increase the area of the reading surface, but in that case, the reading area of the two-dimensional image sensor is increased, and the size of the obtained image data is increased.
There is a problem in efficiency.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a fingerprint reading device capable of efficiently realizing fingerprint reading while enlarging a fingerprint readable area.

[0007]

SUMMARY OF THE INVENTION The present invention for solving the above-mentioned problems of the prior art is such that the reflection state of light inside the finger surface is in contact with the surface of the finger and is not in contact. A different first reflection surface and a second reflection surface formed so as to face the first reflection surface are included, and a light wave is generated while alternately reflecting between the first reflection surface and the second reflection surface. A waveguide for propagating and a light receiving unit for receiving the light wave that has passed through the waveguide, and on the propagation path of the light wave in the waveguide, on the first reflecting surface irradiated by the light wave. A plurality of areas are defined as respective reading areas, and a fingerprint of a finger touching any one of the reading areas is read by the light receiving unit. Here, the waveguide can be, for example, a transparent polyhedron, and in this case, the light wave passes through the waveguide while repeating total reflection between the first reflecting surface and the second reflecting surface. This light wave irradiates a predetermined area of the first reflecting surface, and the irradiated portion is defined as a readable area. That is, each area associated with a plurality of total reflections becomes a readable area, and fingerprints can be read at a plurality of locations. It should be noted that it is possible to set the areas so that they are adjacent to each other.

Here, since the path lengths between the reading areas and the light receiving portion are different from each other, the size of the focused or read fingerprint image is different for each reading area. Therefore, a means for correcting this may be provided. Examples of such means include a means for moving the light receiving portion itself, a lens system for correcting an image formed on the light receiving portion, and a means for selecting one of propagation paths having different path lengths.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION [Basic Configuration] A first embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, the fingerprint reading device according to the present embodiment is configured to include a light emitting unit 11, a waveguide 12, a light receiving unit 13, and an image processing unit 14. The light emitting unit 11 is an LED (light emitting diode) or the like and emits a light wave. This light wave does not have to be beam-shaped like a laser. The waveguide 12 is
It has a first reflecting surface 21, a second reflecting surface 22, and a side surface 23 that are opposed to each other. Of the side surfaces 23, the surface on the light emitting portion 11 side (incident surface) and the surface on the light receiving portion 13 side are the same. In order to prevent total reflection of the light wave, the normal line and the optical axis of the light wave are cut so as to coincide with each other. Therefore, the cross section cut along the path of the light wave of the waveguide 12 is substantially (reverse) as shown in FIG.
It has a trapezoidal shape. The waveguide 12 is made of, for example, glass or the like, and guides the light waves incident between the first reflection surface 21 and the second reflection surface 22 to the light receiving unit 13 side while alternately totally reflecting them.
At this time, on the first reflecting surface of the waveguide, as shown in FIG. 3, along the path of the light wave, the regions (A to D) irradiated by the light wave are arranged at regular intervals. Becomes When a finger touches any position of the areas A to D of the first reflecting surface 21, there is a portion along the convex portion of the fingerprint where the condition for total reflection is not satisfied, and the light wave is not totally reflected at that portion. In addition, the total reflection condition is satisfied in the concave portion of the fingerprint, and the light wave is totally reflected in that portion. As a result, a light wave that reflects the fingerprint image is guided to the light receiving unit 13. Figure 2
In the figure, among the light waves that meet the total reflection condition and are incident at an angle at which they are totally reflected by the first reflection surface 21 and the second reflection surface 22, those that reach the light receiving unit 13 are illustrated.

The light receiving portion 13 is a two-dimensional image sensor, receives the light wave guided by the waveguide 12 and passes through the inside of the waveguide 12, and converts the image received on the light receiving surface into an electrical signal. And outputs it to the image processing unit 14. Image processing unit 14
Generates image data from the electric signal input from the light receiving unit 13 and performs a predetermined process such as collation of the image data.

That is, according to the present embodiment, the light wave emitted by the light emitting section 11 is alternately reflected and guided a plurality of times between the first reflecting surface and the second reflecting surface. By this, a plurality of areas are illuminated on the first reflecting surface, and when a finger is placed on any of the illuminated areas, a part of the light waves will arrive at the light receiving unit 13 reflecting the image of the fingerprint. This area is defined as a readable area of the fingerprint image. As described above, according to the present embodiment, it is possible to increase the degree of freedom of the contact position of the finger and expand the usage scene.

[Size / Focus Correction] In this way, if the image of the fingerprint can be captured regardless of the position of the finger placed in FIGS. 3A to 3D, for example, the position is farthest from the light receiving unit 13. The path difference between when the finger is placed at the position D in FIG. 3 and when the finger is placed at the position C in FIG. 3 is the distance between the first reflecting surface 21 and the second reflecting surface 22. The value of t is 2t / cos θ (where θ is the angle formed by the normal line of the first reflecting surface 21 and the path of the light wave). Therefore, if the fingerprint size and the focus are adjusted to match the case where the finger is initially placed at the position D in FIG. 3, when the finger is placed at the position C in FIG. Is preferably separated from the waveguide 12 by 2t · n / cos θ along the optical axis (path direction) of the light wave. Here, n is the refractive index of the waveguide 12. Therefore, the light receiving unit 13 is housed in the container 31 as shown in FIG. 4 so that the light receiving unit 13 is moved along the optical axis direction, and the container 31 is fixed to the rod 33 driven by the linear actuator 32. By body 31
The light receiving unit 13 is movable along the optical axis. In addition to this mechanism, any mechanism may be used as long as it moves the light receiving unit 13 in the linear direction.

Fingerprint Authentication Process It should be noted here that it is not always necessary to know at which position A to D the finger is actually placed. That is, regardless of the actual position, fingerprint authentication processing (image data collation processing) is performed on the image data a to d obtained by moving the light receiving unit 13 assuming that a finger is placed at each position A to D. This is because it is possible to determine that the authentication has succeeded if the collation is achieved with any of the image data.

Correction using the optical system The size / focus correction is performed by the light receiving unit 13 as described above.
Not only move the position of the
It is also possible to realize the correction by providing a (refractive) optical system (lens system) including a zoom lens between and and changing the zoom ratio in this optical system.

Correction Using Reflective Optical System Further, as a structure for correcting size and focus, as shown in FIG. 5, a first movable mirror 41 and a first reflecting surface 21 are provided.
A reflective optical system including a plurality of fixed mirrors 42a, 42b provided corresponding to the number of upper readable areas and a second movable mirror 43 may be used. First movable mirror 41
Is for rotating the reflecting surface around a predetermined axis, and guides the light wave that has passed through the waveguide 12 to one of the plurality of fixed mirrors 42. The second movable mirror 43 is similar to the first movable mirror, and guides the light wave reflected and guided from one of the fixed mirrors 42 to the light receiving unit 13. The fixed mirrors 42 may be arranged substantially parallel to each other as shown in FIG. 5, and are arranged such that the total distance (path length) to the movable mirrors 41 and 43 is shifted by 2t · n / cos θ. It

Therefore, for example, the finger is the first movable mirror 41 and the second movable mirror 43 for each of A to D in FIG.
3 is adjusted so that the light wave is guided through the fixed mirror 42a when the finger is placed at the position A in FIG. 3, and when the finger is placed at the position B in FIG.
The path in the catoptric system is determined such that the light wave is guided through b.

Correction Using Image Data Further, regarding size correction, size correction may be realized by executing enlargement / reduction processing on image data in the image processing unit 14 by a widely known method.

[Multiple Series of Light Waves] Up to this point, the case where there is only one light emitting section 11 serving as a light source and the path of light waves is only one series has been described. By doing so, as shown in FIG. 6, it is possible to arrange the read storage areas in a matrix. In this case, each light receiving section 13 is provided with a corresponding light receiving section 13 for each series of light waves that have passed through the waveguide 12.
Although the image of the fingerprint may be received at 3, the fixed mirror group 51 and the movable mirror 52 are used to selectively select one of the series of light waves as shown in FIG. 1
You may make it lead to 3.

Further, of the side surfaces 23 of the waveguide 12, two adjacent side surfaces 23 are used as the incident surface of the light wave, so that FIG.
It is also possible to arrange the readable areas in concentric circles, as shown in FIG. In this case, it is also preferable to dispose the movable mirror 55 near the center of the concentric circle and guide the light wave that has passed through the waveguide 12 to the light receiving unit 13 side while driving the movable mirror 55 so as to rotate along the angular direction of the concentric circle.

Also in these cases, the size of the image,
In order to correct the focus, it is preferable to move the light receiving unit 13, use a refraction optical system, use a reflection optical system, or perform image data correction.

[Continuous Readable Area] Further, as shown in FIG. 9A corresponding to FIG. 2, parallel rays are incident on the incident surface of the light wave over the entire width in the height direction. By adjusting the light wave from the light emitting unit 11 using a slit or the like, the readable areas can be adjacent to each other to generate a continuous readable area. In FIG. 9A, the case where the angle formed by the incident surface and the first reflection surface 21 is set to 45 degrees is described as an example, but the angle is not limited to this angle, and the angle is θ degrees. In this case (in this case, if the light wave is incident along the normal to the incident surface, the reflection angle is θ), as shown in FIG. 9B, 2t in the height direction from the side on the second reflecting surface 22 side. × sin
A width of θ or more (where t is the first reflecting surface 21 and the second reflecting surface 2
A parallel light beam having a distance of 2) may be incident.
By doing so, the light wave incident from the end portion on the second reflection surface 22 side irradiates the first reflection surface 21 and the first reflection surface 2
When the light wave incident from the end of the parallel light beam closer to 1 is once reflected by the first reflection surface 21, further reflected by the second reflection surface 22, and returned to the first reflection surface 21, the first reflection Surface 2
The point where 1 is irradiated coincides (point P), so that the readable area becomes continuous. The parallel rays may be obtained using a refractive optical system and a point light source.

In this case, the readable areas can be arranged in a plane as shown in FIG. 10 by using a plurality of series of light waves.

Divided fingerprint image When the readable area is made continuous in this way, the degree of freedom can be given to the position where the finger is placed, but when the finger is placed over a plurality of readable areas, the image of the fingerprint is obtained. May be divided and read. Therefore, the image processing unit 14 generates combined image data by combining at least two pieces of image data corresponding to each reading area, and acquires fingerprint image data based on the combined image data. Specifically, when a light wave of one series is used and a finger is placed across the readable areas A and B of FIG. 3, the image data obtained by the image processing unit 14 is as shown in FIG. As shown. That is, the fingerprint is divided into left and right at the boundary line of the readable area, the left side appears on the right side of the image data, and the right side of the fingerprint appears on the left side of the image data. Therefore, the image processing unit 14 copies the image data and joins them together to generate composite image data (FIG. 11B).

In reality, the readable areas A and B are out of size and focus, so that one of the left and right images is slightly blurred. When performing the correction as described above, for example, the respective image data Ia to Id corrected in accordance with the four readable areas A to D, respectively.
For Ia and Ib, Ib and Ic, and Ic and Id are combined to generate combined image data. The composite image data generated in this way is used for processing such as image data matching.

Further, this processing is the same when a plurality of series of light waves are used. When the area of the readable area is set to cover the area of the finger surface to be read,
No matter where the finger is placed, if continuous 2x2 readable areas are connected to generate synthetic image data,
A fingerprint image is obtained (FIG. 11 (c)). In this case, it is also preferable that the fingerprint image portion of the composite image data is extracted by applying a predetermined image processing technique and then a process such as image matching is performed.

[Detection of Finger Position] If the position where the finger is placed on the waveguide 12 is detected and subjected to the above-described correction processing or the like, more accurate correction and generation of composite image data can be performed. I can help. Therefore, as a detecting means for detecting the position where the finger touches, for example, as shown in FIG. 12, the detecting means is provided outside the first reflecting surface 21 along the outer circumference for a half circumference.
A light projecting group 61 that projects light in parallel to the surface of the reflecting surface 21, and a light receiving group that faces the light projecting group 61 and is provided over a half circumference of the outer circumference of the first reflecting surface 21 and receives light from each light projecting unit. And 62. As a result, the position of the finger is detected by the position where the light from the projector is blocked.

Further, as shown in FIG. 13, the first reflecting surface 21
A plurality of series of light waves traveling in the first axis (X axis) direction of
When a fingerprint image is acquired in a matrix using a plurality of series of light waves traveling in a second axis (Y axis) direction substantially orthogonal to the X axis direction, the fingerprint image of the plurality of series of light waves in the X axis direction is obtained. It is also possible to detect the position touched by the finger on the basis of the information indicating which sequence is obtained and the information indicating which sequence is obtained in the Y-axis direction from which the fingerprint image is obtained. it can. That is, in FIG. 13, if the finger is in contact with the readable area P, the series X1 traveling in the X-axis direction.
And a series Y1 traveling in the Y-axis direction, a fingerprint image is obtained, and the position P where the finger actually contacts can be detected as the intersection.

Utilization of Detected Finger Position The information on the finger position thus detected can be applied to correction processing and used for positioning control of the light receiving section 13 and the like. Further, when the composite image data is generated, it can be used to determine which readable area of the image data should be combined.

[Combination with Display] In the present embodiment, the first reflecting surface 21 and the second reflecting surface 22.
Means that the light wave traveling in the normal direction is substantially transmitted, so that the second reflection surface 2 is provided outside the second reflection surface 22.
By disposing a liquid crystal display, a CRT, or the like facing the second side, a message or the like can be displayed to the user, and the present invention can be applied to applications such as presenting options as shown in FIG.

[Configuration Utilizing Surface Light Source] Next, a fingerprint reading device according to a second embodiment of the present invention will be described.
As shown in FIG. 15A and a sectional view taken along line AA of FIG. 15B, the fingerprint reading device of the present embodiment has a surface light emitting unit 15, a waveguide 12, and a light receiving unit 13. And the image processing unit 14. The same components as those in the first embodiment are designated by the same reference numerals and detailed description thereof will be omitted.

The surface emitting section 15 is arranged outside the second reflecting surface 22 of the waveguide 12, and causes the waveguide 12 to propagate the light wave traveling in the normal direction of the second reflecting surface 22 to the waveguide 12. Incident through. In addition, it is also preferable that the light shielding plate is stretched around except the surface on the side of the light receiving portion 13 so that light does not enter from the side surface 23 side. In this case, when a finger touches the outer surface of the first reflecting surface 21 of the waveguide 12, as shown in FIG. 16A, scattered light that scatters inside the first reflecting surface 21 is generated at the convex portion of the fingerprint. . In addition, the light wave is directly transmitted to the concave portion of the fingerprint through the first reflecting surface 21 and travels to the outside. In this embodiment, the scattered light is received to obtain a fingerprint image. That is, as shown in FIG. 16B, a part of the scattered light is guided to the light receiving unit 13 side while being totally reflected between the first and second reflecting surfaces 21 and 22. Since the fingerprint image obtained in this way looks at the light waves scattered by the convex portions of the fingerprint, the lightness and darkness are reversed from those shown in FIG.

Here, the number of surface emitting portions 15 does not necessarily have to be one. For example, a plurality of surface emitting portions 15 each having an area equivalent to the readable area may be arranged. In this case, one of the plurality of surface light emitting units 15 is selectively turned on sequentially, so that the finger touches the position of the surface emitting unit 15 that is turned on when the fingerprint image is obtained by the light receiving unit 13. You can also find out where you are doing. Here, the surface emitting unit 15 may be a display.

Further, also in the present embodiment, the correction processing in the first embodiment may be performed. When a plurality of surface emitting parts 15 are arranged, each surface emitting part 1
Adjacent 5 can define a continuous readable area,
In this case, it is also preferable to combine the image data to generate the composite image data.

[0034]

According to the present invention, a small number of light emitting portions and light receiving portions can be used to make a plurality of fingerprint readable regions, and efficient fingerprint reading can be realized.

[Brief description of drawings]

FIG. 1 is a diagram showing an outline of a fingerprint reading device according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing paths of light waves in the fingerprint reading device according to the first embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a state of a readable area.

FIG. 4 is a diagram illustrating a configuration example for correcting a fingerprint image.

FIG. 5 is a diagram illustrating another configuration example for correcting a fingerprint image.

FIG. 6 is an explanatory diagram showing an outline of a path when light waves are made into a plurality of series.

FIG. 7 is a diagram illustrating a configuration example in which one light receiving unit receives a plurality of series of light waves.

FIG. 8 is an explanatory diagram showing another example of a path when light waves are made into a plurality of series.

FIG. 9 is an explanatory diagram showing an incident path of a light wave when the readable area is made continuous.

FIG. 10 is an explanatory diagram showing an outline when the readable area is made continuous.

FIG. 11 is an explanatory diagram showing an example of a fingerprint image when a finger is placed over continuous reading areas and an example of synthesizing them to obtain a fingerprint image.

FIG. 12 is an explanatory diagram illustrating an example of a configuration for detecting the position of a finger.

FIG. 13 is an explanatory diagram illustrating another example of a configuration for detecting the position of a finger.

FIG. 14 is an explanatory diagram illustrating an example of content displayed on a display.

FIG. 15 is a diagram showing an outline of a fingerprint reading device according to a second embodiment of the present invention.

FIG. 16 is an explanatory diagram showing paths of light waves in the fingerprint reading device according to the second embodiment of the present invention.

FIG. 17 is a diagram showing an outline of a conventional fingerprint reading device.

FIG. 18 is an explanatory diagram illustrating an example of a general fingerprint image.

[Explanation of symbols]

1 transparent triangular prism, 2 light source, 3 two-dimensional image sensor, 11 light emitting part, 12 waveguide, 13 light receiving part, 14
Image processing unit, 15 surface emitting unit, 21 first reflecting surface, 22
2nd reflective surface, 23 side surface, 31 container, 32 linear actuator, 33 rod, 35 optical system, 41
First movable mirror, 42 fixed mirror, 43 second movable mirror, 51 fixed mirror group, 52, 55 movable mirror,
61 light emitter group, 62 light receiver group.

Continued front page    (72) Inventor Koji Okano             1836 Otani, Omiya, Kuki City, Saitama Prefecture             This signal Kuki office F term (reference) 5B047 AA25 AB02 BA02 BB01 BC05                       BC09 BC11 BC14 CA04 CB22                       DC09                 5B057 BA02 BA12 BA15 BA17 CA12                       CA16 CB13 CB16 CE08

Claims (9)

[Claims] 1. A first reflecting surface, which has a different reflection state of light inside when a finger surface is in contact with the surface and a state where the finger surface is not in contact with the surface, and is formed so as to face the first reflecting surface. A waveguide including a second reflecting surface, which propagates a light wave while alternately reflecting between the first reflecting surface and the second reflecting surface, and a light receiving device for receiving the light wave passing through the waveguide And a plurality of regions on the first reflecting surface, which are irradiated by the light waves, are defined as reading regions on the propagation path of the light waves in the waveguide, and contact any one of the reading regions. A fingerprint reading device, wherein a fingerprint of a finger to be read is read by the light receiving unit. 2. The fingerprint reading device according to claim 1, further comprising a correction unit that corrects the image of the fingerprint to be read. 3. The fingerprint reading device according to claim 2, wherein the correction unit moves the light receiving unit along an optical axis of the light wave.
Alternatively, a lens system provided between the waveguide and the light receiving unit,
Alternatively, a means for propagating the light wave between the waveguide and the light receiving part, which means for propagating the light wave through any one of a plurality of propagation paths having mutually different propagation path lengths, or read by the light receiving part A fingerprint reading device, comprising: a unit configured to generate image data based on the obtained image and correct the image of the fingerprint by performing image processing on the image data. 4. The fingerprint reading device according to claim 1, wherein the light wave is incident so that the light wave propagates through a plurality of paths in the waveguide. A means provided between the waveguide and the light receiving portion, and selectively guiding any one of the light waves that have passed through the waveguide through the plurality of paths to the light receiving portion. A fingerprint reading device characterized by: 5. The fingerprint reading device according to claim 1, wherein the propagation path is set so that the plurality of reading areas are adjacent to each other. Fingerprint reader. 6. The fingerprint reading device according to claim 5, wherein, for each of the plurality of reading areas, a unit that generates image data based on the image read by the light receiving unit, and an image corresponding to each reading area. Means for generating composite image data in which at least two of the data are combined, and based on the composite image data, data of a fingerprint image of a finger touching the plurality of reading areas is acquired. Fingerprint reader. 7. The fingerprint reading device according to claim 1, further comprising a detection unit that detects a position where a finger contacts on the waveguide, and the detection unit. A fingerprint reading device, wherein the information on the position detected by the means is subjected to a predetermined process. 8. The fingerprint reading device according to claim 1, wherein the first reflecting surface and the second reflecting surface of the waveguide are incident on each surface from a substantially vertical direction. Is a transparent body that transmits light, and the reflection is made by total reflection on each surface, and is visible from the outside of the first reflection surface via the waveguide on the outer surface side of the second reflection surface. A fingerprint reader comprising a display means arranged. 9. The fingerprint reading device according to claim 1, wherein the first reflecting surface and the second reflecting surface of the waveguide are incident on each surface from a substantially vertical direction. Is a transparent body that transmits light, the reflection is performed by total reflection on each surface, and a surface light source disposed on the outer surface side of the second reflection surface, and an incident angle of a light wave incident on the waveguide body. And a means for limiting the light source, the light wave emitted from the surface light source reaching the light receiving portion through the waveguide to read a fingerprint image of a finger in contact with the outer surface of the first reflecting surface. A fingerprint reading device characterized by: