JPH11267114A - Finger print imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively prevent failure of accidental imaging of a residual finger print image as caused by extraneous light such as sun light incident into a finger carrier surface or the unclearness of a finger print image as caused by the extraneous light passing through a finger even when the residual finger print image exists on the finger carrier surface of a light transmissible body such as prism. SOLUTION: In a finger print imaging apparatus 1 which comprises a prism (light transmissible body) 2 having a finger carrier surface 21, a light source 3 for admitting illumination light into the prism 2 and a finger print imaging part 4 to image reflected light on the finger carrier surface 21, a finger entry/ exit hole 14 to let a finger be placed on the finger carrier surface 21 while a cover 13 is provided to prevent infiltration of light with a specified band into the finger print imaging part 4 passing through the prism 2 from the finger carrier surface 21 by blocking the transmission of at least the light with the specified band. The light source 3 herein used is an emission source with a specified band.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fingerprint imaging device suitable for a fingerprint identification device for identifying an individual,
In particular, the present invention relates to prevention of erroneous identification due to an afterimage fingerprint when external light is incident on a finger mounting surface of a light transmitting body such as a prism, or erroneous identification due to incident external light transmitted through a finger.

[0002]

2. Description of the Related Art In a fingerprint imaging apparatus, the fingerprint side of a finger is pressed against a finger-mounting surface (a slope in a prism) of a light-transmitting member such as a prism, a light-transmitting plate, or a bundle of optical fibers, and is pressed against one of the light-transmitting members (a rectangular surface in a prism). Illumination light is incident from one of the surfaces). In the prism, the incident light is transmitted on the finger contact surface on the finger placement surface, is reflected on the finger non-contact surface, and is emitted as reflected light from the other of the orthogonal surfaces of the prism. In addition, on the contrary,
Depending on the selection of the incident angle, the incident light may be transmitted on the finger non-contact surface and reflected on the finger contact surface. The reflected light is captured by an imaging unit including an imaging lens and a charge-coupled device image sensor (CCD) disposed at a position where a fingerprint image is formed on the lens, and an electric fingerprint image is obtained.

The fingerprint identification device stores the positional relationship of the characteristic points of the fingerprint from the fingerprint image as characteristic data for each individual, compares the data with the fingerprint image of the user, and identifies the individual in real time. Do. It is necessary for the accurate fingerprint identification that the fingerprint image of the user obtained by the fingerprint imaging device be clear and accurate regardless of the state of the finger placement surface of a light transmitting body such as a prism.

However, in a fingerprint imaging apparatus comprising a light source, a light transmitting member such as a prism, and an imaging unit using a CCD, the reflected light of the finger mounting surface of the light transmitting member such as a prism is obtained as fingerprint ridge information. In this method, external light such as sunlight or artificial light enters the finger placement surface. Due to the incidence of this external light, the sebum of the user before being left on the finger placement surface,
In some cases, sweat or the like is irregularly reflected, and a fingerprint image (residual fingerprint image) is observed as if the finger were placed on the finger placement surface. In the case of a system in which the finger placement surface transmits light on the finger contact surface and is totally reflected on the non-finger contact surface, the external light transmitted through the finger despite the finger being placed on the finger placement surface. Conversely, there is also observed a problem that the light enters the light-transmitting body from the finger contact surface, and the portion that should be photographed dark without being totally reflected becomes bright, thereby deteriorating the contrast of the fingerprint image and making the fingerprint image unclear.

[0005]

The fingerprint image remaining on the finger mounting surface of a light-transmitting body such as a prism is converted into a fingerprint image by a fingerprint imaging unit when external light such as sunlight or artificial light enters the finger mounting surface. There is a possibility that an image is captured and a false verification of the fingerprint verification device is caused. Further, the fingerprint image may be blurred by the light transmitted through the finger, and accurate fingerprint collation may not be performed.
SUMMARY OF THE INVENTION It is an object of the present invention to capture a residual fingerprint image when sunlight or artificial light or the like is incident on the finger mounting surface even when a residual fingerprint image exists on a finger mounting surface of a light transmitting body such as a prism. It is an object of the present invention to provide a fingerprint imaging apparatus capable of effectively preventing a trouble that may occur, and reliably preventing a fingerprint image from being blurred by light transmitted through a finger.

[0006]

According to the present invention, there is provided a light-transmitting member having a finger placement surface, a light source for causing illumination light to enter the light-transmitting member, and imaging light reflected by the finger placement surface. A fingerprint imaging device comprising: a finger imaging surface having a finger insertion / exit opening for allowing a finger to be placed on the finger placement surface; A cover is provided to prevent the finger placement surface from passing through the light transmitting body and entering the fingerprint imaging unit,
The light source is a light source of the specific band.

[0007] An optical filter that transmits at least the light of the specific band and blocks light transmitted through the cover may be provided in an optical path from the radiation surface of the light source to the fingerprint imaging unit. A combination of both a light source that emits only light in a specific band and an optical filter that selectively transmits only light in the specific band is most desirable.

[0008]

According to the present invention, the cover selectively transmits light of a specific band, a high-pass filter that transmits only light of a certain wavelength or less, and a low-pass filter that transmits only light of a certain wavelength or more. The filter selectively blocks transmission of at least a specific band of light. That is, of the external light such as sunlight or artificial light, the band light that can be sensed by the fingerprint imaging unit (CCD light receiving surface, etc.) is covered (bandpass filter).
Thus, the light is prevented from entering from the finger mounting surface of a light transmitting body such as a prism.

[0009]

As a result, even if a residual fingerprint image is present on the finger placement surface of a light transmitting body such as a prism, external light such as sunlight or artificial light is incident on the finger placement surface and the residual fingerprint image is formed. It is possible to reliably prevent the trouble of being imaged. Further, even when external light passes through the finger placed on the finger placement surface of the light transmitting body, the cover selectively blocks transmission of light of at least a specific band. Therefore, even in a system in which light is transmitted on the finger contact surface and totally reflected on the finger non-contact surface, it is possible to effectively prevent the fingerprint image from being unclear.

[0010] Since the cover at least blocks the transmission of light of a specific band and transmits other light, the user can perform fingerprint matching while visually recognizing the state of the finger inside the cover from outside. If an opaque material that does not transmit light is used as the cover, external light cannot enter the fingerprint imaging unit from the finger placement surface of the prism, and malfunctions due to residual fingerprint images and fingerprint image Blurring can be prevented and no filter is required. However, in this case, since the user cannot visually recognize the state of his / her finger in the cover, the usability is extremely poor and the practicality is low.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to an embodiment shown in FIGS. Fingerprint imaging device 1 of this embodiment
Has a box-shaped casing 10 and has a vertical wall surface W
Has a structure to be fitted into the recess H provided at The front surface of the casing 10 is a panel 11, and a finger insertion hole 12 is formed in the center of the panel 11. On the front face of the panel 11, a semi-shell-shaped cover 1 that covers the finger insertion hole 12
3 is attached. The lower bottom of the cover 13 is opened to form a finger opening 14.

A prism 2 is fixed as a light transmissive member in the depth of the finger insertion hole 12 of the casing 10, and an inclined surface (hereinafter, referred to as a finger mounting surface) 21 of the prism 2 is inclined forward by 45 degrees. ing. Of the two orthogonal surfaces of the prism 2, the bottom surface set to be substantially horizontal is the incident surface 22 for the illumination light. Of the two surfaces orthogonal to each other of the prism 2, the rear surface set to be substantially vertical has a radiation surface 23 from which a mixed light of the reflected light on the finger placement surface 21 and the incident light from the finger placement surface 21 is emitted. Has become. The finger insertion hole 12 and the finger placement surface 21 communicate with each other through a finger insertion passage surrounded by a curved wall 15.

An illumination light source 3 is mounted below the entrance surface 22 in the casing 10. The light source 3 for illumination is
Light emitting diode 3 mounted to illuminate above
1 and a diffusion plate 32 interposed between the light emitting diode 31 and the incident surface 22 for diffusing the light emitted from the light emitting diode 31 to make it uniform.

Behind the radiation surface 23 in the casing 10, the fingerprint imaging unit 4 is attached. Fingerprint imaging unit 4
Is a lens 41 and a charge-coupled device image sensor (hereinafter, referred to as a sensor) disposed at a position where a fingerprint image is formed by the lens 41.
42). Emission surface 23 and lens 4
1, a band-pass filter 5 is provided.

The cover 13 transmits the light of the band B shown in FIG. 4A out of the external light A (sunlight or artificial light) shown in FIG. 3 and the band C shown in FIG. (Specific band) light is absorbed or reflected to prevent transmission. Note that the light in the band C where the cover 13 blocks the transmission substantially coincides with the band of the light emitted by the illumination light source 3 (band C shown in FIG. 4). This is because the light emission band of the illumination light source, which is an effective feature of the CCD light reception, is not allowed to enter from the outside.

Thus, the light emitted from the radiation surface 23 of the prism 2 to the fingerprint imaging unit 4 is a mixed light of the band B (the light transmitted through the cover 13) and the band C (the light emitted from the light source 3). The wavelength characteristic shown in (a) is obtained. The band-pass filter 5 is an optical band-pass filter shown in (c) of FIG. 4, and the mixed light (a) passes through the band-pass filter 5 to become light D having a wavelength characteristic shown in (b) of FIG. CCD4
2 is incident.

FIG. 5A shows the finger mounting surface 2 of the prism 2.
1 shows a residual fingerprint image taken by a fingerprint imaging device of the present invention, with an oil-based residual fingerprint image attached to 1. FIG. 5B shows a residual fingerprint image captured by a conventional fingerprint imaging device without the cover 13 and the bandpass filter 5 under the same conditions. In the fingerprint imaging apparatus of the present invention, it can be seen that the residual fingerprint image is almost completely erased and photographed by the fingerprint imaging unit.

FIG. 6 is a schematic diagram showing a main part of the fingerprint imaging apparatus according to the second embodiment. In this embodiment, a plate glass 6 is used as a light transmitting body. Light emitted from the light emitting diode 31 to the finger placement surface 61 is transmitted on the fingerprint (finger) non-contact surface, partially reflected on the fingerprint (finger) contact surface, and is repeatedly totally reflected in the glass sheet 6. The light passes through the band-pass filter 5 from the radiation surface 63 on which the optical element 62 is stretched, and enters a fingerprint imaging unit (not shown).

FIG. 7 is a schematic diagram showing a main part of a fingerprint imaging apparatus according to the third embodiment. In this embodiment, a bundle 7 of optical fibers 71 is used as a light transmitting body. The bundle 7 of the optical fibers 71 has a finger mounting surface 72 orthogonal to the axis at the upper end surface, and a tapered portion 73 whose diameter gradually decreases downward at the lower portion.

FIG. 8 is a schematic view showing a main part of a fingerprint imaging apparatus according to a fourth embodiment. In this embodiment, the finger placing surface 82 is formed by obliquely polishing the upper end surface of a bundle 8 of optical fibers 81 as a light transmitting body. As shown in FIGS. 6 to 8, various types of light transmitting bodies other than prisms that can form a finger placement surface that can utilize total reflection can be used.

In the above-described embodiment, the cover 13 is formed of a material that blocks transmission of only light of the specific band C, and emits light from the light source (light emitting diode 31) or light that passes through the band-pass filter 5 to the specific band C. Although the case where the light is used has been described, the present invention may be the following combinations. B) The light emitted from the light source (light emitting diode 31) or the light passing through the band-pass filter 5 is red light (or light having a longer wavelength), and the cover 13 is a high-pass filter that transmits light having a shorter wavelength than the red light. Form. B) Light emitted from the light source (light emitting diode 31) or light passing through the band-pass filter 5 is converted into blue light (or light having a short wavelength), and the cover 13 is a low-pass filter that transmits light having a longer wavelength than the blue light. Form.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a fingerprint imaging device.

FIG. 2 is a front view of the fingerprint imaging device.

FIG. 3 is an enlarged view of a main part of FIG. 1;

FIG. 4 is a characteristic graph of bands of transmitted light of a cover and a filter.

FIG. 5 is an imaging diagram of a residual fingerprint image by the fingerprint imaging device.

FIG. 6 is a schematic view of a main part of a fingerprint imaging apparatus according to a second embodiment.

FIG. 7 is a schematic diagram of a main part of a fingerprint imaging apparatus according to a third embodiment.

FIG. 8 is a schematic diagram of a main part of a fingerprint imaging device according to a fourth embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fingerprint imaging device 2 Prism (light-transmitting body) 3 Light source for illumination 4 Fingerprint image pick-up part 5 Optical filter 6 Plate glass (light-transmitting body) 7 Bundle of optical fibers (light-transmitting body) 12 Finger insertion hole 13 Cover 14 Finger entry / exit 21 Finger placement surface 22 Incident surface 23 Emissive surface 31 Light emitting diode 32 Diffusion plate (light diffusion plate) 41 Lens (imaging lens) 42 CCD (charge coupled device image sensor) C band (specific band)

Claims (7)

[Claims] 1. A fingerprint comprising: a light-transmitting member having a finger placement surface; a light source for causing illumination light to enter the light-transmitting member; and a fingerprint imaging section for imaging reflected light from the finger placement surface. In the image pickup apparatus, the finger placement surface has a finger access port for allowing placement of a finger, and at least a specific band of light is prevented from transmitting light of the specific band so that the light of the specific band is transmitted from the finger placement surface to the finger placement surface. A fingerprint imaging apparatus, comprising: a cover for preventing the light from passing through a light transmitting body and entering the fingerprint imaging unit; and the illumination light is light of the specific band. 2. The fingerprint imaging device according to claim 1, wherein the light source is formed of a light emitting diode that emits light of the specific band, and the fingerprint imaging unit is disposed at an imaging lens and a position where a fingerprint image is formed on the lens. A fingerprint imaging device comprising a charge coupled device image sensor. 3. A fingerprint comprising: a light-transmitting member having a finger placement surface; a light source for causing illumination light to enter the light-transmitting member; and a fingerprint imaging section for imaging reflected light from the finger placement surface. In the image pickup apparatus, the finger placement surface has a finger access port for allowing placement of a finger, and at least a specific band of light is blocked from transmitting the light of the specific band and the light of the specific band is transmitted from the finger placement surface. A cover is provided to prevent the light from passing through the light transmitting body and entering the fingerprint imaging unit, and at least the light of the specific band is transmitted through the optical path from the light transmitting body to the fingerprint imaging unit and transmitted through the cover. A fingerprint image pickup device, comprising an optical filter for preventing transmission of light from being emitted. 4. The fingerprint imaging device according to claim 3, wherein the light source is formed of a light emitting diode that emits light of the specific band, and the fingerprint imaging unit is provided at an imaging lens and a position where a fingerprint image is formed on the lens. A fingerprint imaging device, comprising: a charge-coupled device image sensor disposed therein, wherein the optical filter is disposed between the translucent member and the imaging lens. 5. The fingerprint imaging device according to claim 2, wherein a light diffusion plate is provided between the light emitting diode and the light transmitting body. 6. The fingerprint imaging device according to claim 1, wherein the light-transmitting member is a prism. 7. The fingerprint imaging apparatus according to claim 1, wherein said cover has a semi-cannonball shape, and a finger slot is provided at the bottom of said cover. apparatus.