JPH07171137A - Fingerprint reading device - Google Patents

Abstract

PURPOSE:To output a clear fingerprint image. CONSTITUTION:A fingerprint reading unit 60 lights the input end surface 2 of a FOP 1 by an infrared LED 61, and detects a fingerprint image outputted to an output end surface 3 by a CCD 63. In a controlling computer 65, the detection of the fingerprint image by the CCD 63 is started when the top end of a finger is sensed by a touch sensor 62 and a prescribed pressing force is sensed by a pressure sensor 64.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fingerprint reader using a fiber optic plate.

[0002]

2. Description of the Related Art A fiber optic plate 100 (hereinafter referred to as "FOP") as shown in FIG. 19 has been conventionally known (US Pat. No. 3,906,520). This FOP1
Reference numeral 00 denotes a bundle of a large number of optical fibers 101, and an input end face 102 that is inclined and cut with respect to the optical axis is formed at one end of the optical fiber 101 to increase the contact area with a finger. The end surface 102 is formed as a curved surface having a viewing angle φ. When the finger 103 is brought into close contact with the input end face 102 and light is applied from the light source 105, the concavo-convex pattern of the close contact portion is projected on the output end face 104 on the opposite side. As a result, the fingerprint image can be read.

[0003]

The fingerprint reading device shown in FIG. 20 employs a system in which projection light for detecting a fingerprint is made incident from the output end face 104 side. Therefore, the FOP 100 and the fingerprint reading unit are adopted. It is necessary to secure a space for receiving the incident light between the optical system and the optical system, and there is a drawback that the entire system becomes large and the configuration becomes complicated.

Further, in addition to the fingerprint image (reflected light) generated by the incident light, extra light also enters from the input end face 102, which lowers the contrast of the detected fingerprint. Further, since the input end face 102 has a curved structure, there is a problem that the influence of scattered light is particularly remarkable.

The present invention has been made to solve the above problems, and an object thereof is to make the entire apparatus compact and to prevent unnecessary light such as background light from being output from the output end face. The purpose of the present invention is to provide a fingerprint reading device capable of clearly outputting an image of the close contact portion.

[0006]

A fingerprint reading device according to the present invention uses a fiber optic plate having an input end face and an output end face to which a finger is brought into contact, and illuminates the input end face at a position opposite to the input end face. Illuminating means for emitting light is arranged, and output image detecting means for detecting an image output from the output end surface is arranged on the output end surface. Further, it comprises a control means for controlling the operation of the illumination means and the output image detection means. Furthermore, this fiber optic plate is provided with a plurality of cores that propagate the light incident from the input end face, a clad that covers the outer peripheral portion of each core, and a light absorber that covers the outer peripheral portion of the clad. The angle of inclination of the input end face with respect to the optical axis is set to an angle at which light incident on the core from the air does not undergo total internal reflection at the interface with the cladding.

On the other hand, the fingerprint reading apparatus further includes a contact detecting means for detecting that the finger touches the position where the tip of the finger should reach when the finger is brought into close contact with the predetermined position of the input end face. It can be provided.

Further, pressure detecting means for detecting the pressing force with which the finger presses the fiber optic plate may be provided on one end surface of the fiber optic plate.

When the contact detecting means and the pressure detecting means are provided in this way, the contact detecting means detects the finger in the control means, and when the detection result of the pressure detecting means reaches a predetermined value. It is also possible to perform control so that the image obtained from the output end face is detected by the output image detecting means.

[0010]

When the inclination angle of the input end face of the fiber optic plate is set to such a condition, a part of the light propagating through the air and entering the core from the input end face leaks from the core to the clad and is absorbed by the absorber. Absorbed by. Therefore, unnecessary light such as background light is gradually attenuated in the process of propagating through the core,
There is almost no output from the output end face. On the other hand, when the surface of the object is brought into close contact with the input end face, the light transmitted through this close contact portion enters the core, but this incident light meets the condition of total reflection at the interface with the cladding. There will also be light incident at an angle. That is, only the light incident from the close contact portion is output from the output end face.

Further, the contact detecting means detects that the finger is set at a position where the fingerprint can be accurately read, and the pressure detecting means detects that the finger presses the input end face with a predetermined pressure. To be done. That is, by using each of these detection means, it is possible to always set the finger at the same position and press it with the same pressure.

[0012]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a fiber optic plate (hereinafter referred to as F
1 shows the appearance of 1). The FOP 1 is used in a fingerprint reading device described later, and is integrally formed in a state in which a plurality of optical fibers are bundled. FOP
1 has an input end face 2 inclined with respect to the optical axis of the fiber, and an opposite end has an output end face 3 formed substantially perpendicular to the optical axis.

As shown in FIG. 2, the FOP 1 comprises a core 5 for propagating incident light, a clad 6 for covering the outer peripheral portion thereof, and an absorber 7 provided so as to cover the outer peripheral portion of each clad 6. It consists of types. By providing the absorber 7 at this position, the light leaked from the core 5 and the cladding 6
Since the light incident on is absorbed, the adjacent optical fibers are in a state of being optically insulated by the absorber 7. The core 5, the clad 6 and the absorber 7
Are formed of the materials shown in FIG. 4, respectively. As a result, the core 5 has a refractive index of 1.621 and the cladding 6 has a refractive index of 1.519. Further, as an example of the size of the FOP 1, each dimension is shown in FIG.

By forming the FOP 1 with the optical fiber in which the outer peripheral portion of the clad 6 is covered with the absorber in this way, the light incident on each core 5 leaks from the core 5 and enters another adjacent core 5. Incident is avoided, occurrence of crosstalk between adjacent fibers can be prevented, and the S / N ratio of the output image is improved. This action is independent of the inclination angle of the input end face, and no matter how acute the inclination angle of the input end face is, the light incident on each core is propagated through each core and output from the output end face. It is what is done. Also, F
In OP1, by setting the inclination angle of the input end face 2 (the inclination angle with respect to the optical axis of the optical fiber) to a specific value, excellent actions and effects as described later are exhibited.

FIG. 3 shows a vertical section of the FOP 1. In the figure,
n ₀ is the refractive index of the core, n ₁ is the refractive index of the cladding, and n is the refractive index of air. FOP1 of this embodiment
In the above, the inclination angle α of the input end face 2 is defined so that the light receiving angle becomes 0 °. That is, the inclination angle α is set to such an angle that total reflection does not occur at the boundary surface between the core 5 and the cladding 6 no matter what angle the light enters from the air into the core 5. .

This inclination angle α can be obtained from the following equation.

N ₀ sin β = n ₁ sin 90 ° (condition of total reflection) (1) n ₀ sin γ = n sin 90 ° (condition of light receiving angle 0 °) (2) α + (90 ° + γ) + (90 ° −β) = 180 ° (3) In this case, from FIG. 4, n ₀ = 1.621, n ₁ = 1.519, n
= 1, so α = 31.54 °. Therefore, when the inclination angle α in FIG.
The light propagating through the air and incident from the input end face 2 does not undergo total reflection at the interface between the core and the clad, regardless of the angle of incidence.

Therefore, the light incident on the FOP from the input end face 2 partially leaks from the core to the cladding and is absorbed by the absorber in the process of repeating refraction and propagating, and then gradually attenuates and disappears. In this way, when the inclination angle of the input end face 2 is set to such an angle, the light propagating through the air and entering the FOP 1 from the input end face 2 is hardly output from the output end face 3.

On the other hand, as shown in FIG. 5, in this state, when a specific object, for example, the surface of the finger 10 is brought into close contact with the input end face 2, the close contact with the input end face 2 due to the unevenness of the fingerprint. A non-contact portion 12 that forms a gap between the portion 11 and the input end surface 2 is formed. In the close contact portion 11, the input end surface 2 and the surface of the finger 10 are in close contact with each other, and the refractive index of the finger surface is higher than the refractive index of air. Therefore, the input end face 2
The relationship between the incident angle of the light incident on and the condition for total reflection at the interface with the cladding changes from that before contact,
At the interface with the clad, some light enters at an angle that satisfies the condition of total reflection. For example, it is assumed that light is emitted from behind the finger 10 and the transmitted light reaches point A (FIG. 5). Of the light entering the FOP 1 from point A, as shown in the figure, the light entering in the range of 40.68 ° satisfies the condition of total reflection at the boundary surface between the core 5 and the clad 6 ((2) (From the equation), this incident light is repeatedly totally reflected at the boundary surface with the cladding and is output from the output end face 3 side. Light that has entered beyond this angle range is attenuated and disappears in the process of repeated propagation of refraction.

On the other hand, in the non-contact portion 12, a void portion 13 as shown in the drawing is formed, and air is present therein. That is, there is no difference from the state before the finger 10 is brought into close contact. Therefore, although the light enters the core 5 from the non-adhesive portion 12 of the input end face 2, no matter what angle the light enters, the condition of total reflection at the interface with the cladding is still not satisfied, and the core 5 It decays and disappears as it propagates inside.

Therefore, when detecting the surface image of the object in this way, only the light incident from the convex portion of the object surface that is in close contact with the input end surface 2 is output from the output end surface 3 and enters from the concave portion of the surface. Light is attenuated and disappears in the propagation process.
Therefore, unnecessary light such as background light is removed, and only the image of the portion in close contact with the input end face is transmitted and output.

The example explained above is NA (numerical aperture).
= 0.55, and Table 1 shows the tilt angles α with respect to other major NAs.

[0024]

[Table 1]

Further, the shape of the input end face 2 of the FOP 1 may be set as shown in FIG. The shape in FIG. 7 shows a cross section of the input end face 2 taken along the line 11 ′, and the arrow y in the drawing shows the optical axis of each fiber forming the FOP 1 (FIG. 6). FIG. 7A shows the input end face 2 having a planar shape as shown in FIG.
In (e), the input end surface 2 is concave, and the contact surface with the finger is large. In addition, in FIGS. 7F and 7G, the input end face 2 is formed in a slanted shape so that the image of the portion pressed by the input end face 2 is enlarged and output as compared with FIG. You can

Here, a specific configuration of a fingerprint reading device equipped with such a FOP 1 will be shown.

FIG. 8 shows a fingerprint reading device,
It is composed of the above-mentioned FOP 1, CCD 20, computer 21, and the like. The input end face 2 of the FOP 1 is formed so as to be inclined with respect to the optical axis, and the inclination angle θ is set to be equal to or smaller than the inclination angle α obtained by the equations (1) to (3) described above. A finger 22 is pressed against this surface to be in close contact therewith, and light is emitted from a light source 23 provided behind or on the side surface side. When they are brought into close contact with each other in this manner, the uneven pattern (fingerprint image) of the close contact portion is transmitted to the output end face 3, this image data is given to the CCD 20, and the signal thereof is subjected to image processing in the computer 21. .

FIG. 9 shows another configuration example. In this example, the lens 30 is arranged on the output end face 3 side of the FOP 1,
The image output to the output end face 3 through the lens 30 is read by the line sensor 31, and the signal is processed by the computer 32.

FIG. 10 shows another fingerprint reading device. The fingerprint reader 50 has a main body 51 having a substantially ellipsoidal shape, and when reading a fingerprint, as shown in FIG. 11, the main body 51 is held with one hand so that the fingertip is inside the opening 52. To insert. An LED array 66 for display is provided on the front surface of the main body 51, and various displays are performed for the user by the color of light emitted from the LEDs. A sound source may be provided adjacent to the LED array 66 to notify the user by sound. In addition, inside the main body 51, as shown in FIG.
A fingerprint reading unit 60 is provided.

FIG. 13 shows the fingerprint reading unit 60 taken out. This unit 60 uses the FOP 1 described above, and its input end face 2 is formed into a semi-cylindrical curved surface as shown in FIG. 15 in order to enhance the contact property with the finger and increase the contact area. . Also in this case, the inclination angle θ of the input end face with respect to the optical axis is set to be equal to or less than the above-described inclination angle α.

Further, an infrared LED 61 for illumination is arranged on the opposite side of the input end face 2 to emit illumination light when a finger is set. The emission wavelength λ of the infrared LED 61
Is set to 600 nm <λ <900 nm in consideration of the transparency of the human body and the absorptivity of the clad in FOP1. That is, with light having a wavelength shorter than 600 nm, the transmittance of the finger is extremely reduced, and with light having a wavelength longer than 900 nm, the absorption characteristics of the cladding (light absorber) are deteriorated, and This is because the optical insulation is deteriorated.

On the other hand, a touch sensor 62 having a living body confirmation function is provided on the output end face 3 side of the extension of the input end face 2, and when a finger is set at a prescribed position on the input end face 2, The tips of the are in contact with each other. As the touch sensor, various sensors such as electricity, pyroelectricity, temperature, magnetism and blood flow can be used.

A CCD 63 is provided at a portion where the fingerprint image is output on the output end face 3 side, and the output image is detected as image data.

A pressure sensor 64 is provided on the rear side of the FOP 1.
And a mechanism for sampling a fingerprint image when the input end face 2 of the FOP 1 is pressed with the pad of the finger and the input end face 2 is pressed with a predetermined pressing force or more. Has become. By providing the pressure sensor 64 and the touch sensor 62, it is possible to sample the fingerprint image input at the same position and the same pressure.

Further, on the back side of the pressure sensor 64,
A control computer 65 for controlling various operations at the time of reading a fingerprint is arranged, and is integrally configured as a whole. As shown in the block diagram of FIG. 14, the control computer 65 includes a touch sensor control unit 65a that controls the detection operation of the touch sensor 62, an infrared LED control unit 65b that controls emission of the infrared LED 61, and a pressure sensor 6.
The pressure collation unit 65c that collates the pressure level detected in 4 with a specified value, the image signal control unit 65d that controls the image signal detected by the CCD 63, and the like, and these also include the LED array 66 for display. Signal display control unit 6
5e is jurisdictionally controlled.

Next, the operation of the fingerprint reading device 50 will be described with reference to the schematic diagrams shown in FIGS. 16 and 17 and the flowchart of FIG. First, on the display LED array 66, a display indicating that a fingerprint can be read or a prompt for inserting a finger is displayed. Therefore,
As shown in FIG. 11, the main body 51 of the fingerprint reading device 50 is held with one hand, and the fingertip is inserted into the opening 52, and the finger is placed along the input end face 2 of the FOP 1 (see FIG. 16, # 100). ). At this time, the tip of the finger touches the touch sensor 6
Insert your finger until you touch 2. Control computer 65
Then, by detecting the detection result provided from the touch sensor 62 having a living body confirmation function, that is, detecting that any object touches the touch sensor and the sensed temperature is 35 to 38 degrees, It is a mechanism for determining that the touch sensor 62 is touched. Then, when it is detected that the finger touches the touch sensor 62 in this way (“Yes” in # 102), the control computer 65 turns off the LED array 66 for display, and at the same time, for lighting. Infrared LED 61 is turned on, CCD 63
The control to turn on the power source is performed (# 103). In addition,
If it is not detected by the touch sensor 62, it is determined that the insertion of the finger is insufficient, and the LE is instructed to reset the finger.
It is displayed by the D array 66 (# 104). In this way, when displaying and notifying the user, at any stage of operation, a mechanism for notifying with synthetic voice or electronic sound may be adopted.

Next, the control computer 65 uses the LED
The array 66 is turned on, and the user is urged to press the input end face 2 of the FOP 1 with a finger (# 105). This pressing force is detected by the pressure sensor 64, and when a certain pressure (10 g / cm ^{2 in} this example) is reached (“Yes” at # 106), the image of the fingerprint output from the output end face 3 of the FOP 1 Is detected by the CCD 63 (see FIG. 17). That is, the control computer 65 causes the image signal control section 65d to capture the image signal detected by the CCD 63 and execute sampling (# 107).

The sampled image signal is transmitted to the external fingerprint collation device 70 (FIG. 14), and the fingerprint collation device 70 collates the fingerprint. As a result, when the fingerprint collation is successful (“Yes” at # 108), the LED array 6
6 is turned on, and the user is notified that fingerprint collation is completed (# 109). Then, if it is determined that the fingerprint is a suitable fingerprint as a result of this collation, a signal indicating that fact is output, and the processing operation of this fingerprint reader is completed (#
110). When the fingerprint cannot be collated in # 108 (“No” in # 108), the LED array 66 is displayed to prompt the user to reset the finger (# 104), and the reading operation is repeated.

By constructing the fingerprint reading device in this way, unlike the prior art, a fingerprint image is output using the transmitted light from the finger. Therefore, as in the prior art shown in FIG. It is not necessary to secure a space for receiving illumination light between the FOP 1 and the output end face 3 of the FOP 1,
It is possible to bring the 63 and the output end face 3 of the FOP 1 into close contact with each other. Further, since only the light from the contact portion between the input end face 2 of the FOP 1 and the finger is output through the inside of the FOP, there is no influence of incidence of diffused reflection light that is likely to occur due to the curved input end face 2. Furthermore, since the wavelength of the illumination light that is the incident light is a wavelength that takes into consideration the transparency of the human body and the light absorption of the clad, it suppresses the attenuation of light in the human body and maintains the optical insulation characteristics during FOP. While efficiently CC the fingerprint image
Can be transmitted to D63. As a result, the LED can be used efficiently even with a small amount of light, so that the device can be downsized.
It is possible to realize low power consumption.

In the fingerprint reading unit shown in FIGS. 12 and 13, an example of the structure for detecting the fingerprint of one finger is shown. However, as shown by the dotted line in FIG. 13, other than the control computer 65 and the LED array 66. FO
By arranging adjacent to P1, it is possible to read fingerprints of a plurality of fingers at a time.

[0041]

According to the fingerprint reading apparatus of the present invention, the inclination angle of the input end face of the fiber optical plate is
Since the angle of the light entering the core from the air does not cause total internal reflection at the interface with the cladding, only the light entering from the surface of the finger that is in close contact with the input end face is output from the output end face. It is possible to obtain a clear fingerprint image.

Further, by providing the contact detection means and the pressure detection means, it becomes possible to always set the fingerprint and the finger to be read at the same position, and always press them with the same pressure. As a result, the fingerprint image pressed at the same position and with the same pressing force can be sampled, and the reproducibility of the input fingerprint image can be improved.

[Brief description of drawings]

FIG. 1 is a perspective view showing a fiber optic plate used in an embodiment of the present invention.

FIG. 2 is a partial cross-sectional view of a fiber optic plate.

FIG. 3 is a partial vertical cross-sectional view of a fiber optical plate.

[Fig. 4] Weight percentage of each material composition of core, clad, and absorber
2 is a table showing the refractive indexes of the core and the clad, as shown in FIG.

FIG. 5 is a vertical cross-sectional view of the fiber optic plate showing a partially enlarged state in which a finger surface is brought into close contact with the input end surface of the fiber optic plate.

FIG. 6 is a schematic view showing a side surface of a fiber optical plate.

FIG. 7 shows the fiber optic plate of FIG.
It is a figure which shows the cross section cut | disconnected by the 1'line, and FIGS. (a)-(g) is sectional drawing which illustrates the shape of an input end surface.

FIG. 8 is a schematic configuration diagram showing a fingerprint reading device provided with a fiber optical plate.

FIG. 9 is a diagram schematically showing another device configuration including a fiber optical plate.

FIG. 10 is a perspective view showing the external appearance of another fingerprint reading device including a fiber optical plate.

11 is a perspective view showing a state in which one hand is set on the fingerprint reading device shown in FIG.

12 is a perspective view showing a fingerprint reading unit provided in the fingerprint reading device of FIG.

13 is a perspective view showing the configuration of the fingerprint reading unit of FIG.

14 is a block diagram schematically showing the configuration of the fingerprint reading device of FIG.

FIG. 15 is a side view showing a fiber optical plate constituting the fingerprint reading unit of FIG.

16 is a schematic diagram showing a state in which a finger is set on the fiber optical plate of FIG.

FIG. 17 is an explanatory diagram showing a state in which a fingerprint image is output on the output end surface of the fiber optical plate.

18 is a flowchart showing the processing operation of the fingerprint reading device of FIG.

FIG. 19 is a perspective view showing a conventional fiber optic plate.

FIG. 20 is a perspective view showing a configuration of a conventional fingerprint reading device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Fiber optical plate, 2 ... Input end face, 3 ... Output end face, 5 ... Core, 6 ... Clad, 7 ... Absorber (light absorber), 50 ... Fingerprint reader, 51 ... Main body, 60 ... Fingerprint reader unit, 61 ... Infrared LED, 62 ... Touch sensor, 63 ... CCD, 64 ... Pressure sensor, 65 ... Control computer.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication location G06T 1/00 (72) Inventor Toshihiko Hino 1126 Hamamatsu City, Hamamatsu City, Shizuoka Prefecture 1 Hamamatsu Photonics Co., Ltd. Company (72) Inventor Toshiaki Kawai 1 1126 Nomachi, Hamamatsu City, Shizuoka Prefecture Hamamatsu Photonics Co., Ltd.

Claims (4)

[Claims] 1. A fiber optic plate having an input end face to be brought into contact with a finger, and an output end face from which light incident from the input end face is output; and an illuminating light provided on the input end face so as to face the input end face. Illuminating means for emitting light, output image detecting means provided on the output end face of the fiber optic plate for detecting an image output from the output end face, and control means for controlling the operation of the illuminating means and output image detecting means. And, the fiber optical plate, a plurality of cores that propagate the light incident from the input end face,
A cladding that covers the outer peripheral portion of each core, and a light absorber that covers the outer peripheral portion of the clad and absorbs light incident on this portion, and the inclination angle of the input end surface with respect to the optical axis of the core is A fingerprint reader, wherein the light incident on the core from inside is set at an angle such that total reflection does not occur at the interface with the clad. 2. When the finger is brought into close contact with a predetermined position of the input end face, a contact detection unit is further provided for detecting that the finger is in contact with a position where the tip of the finger should reach. The fingerprint reading device according to claim 1. 3. The fingerprint reader according to claim 2, further comprising pressure detecting means for detecting a pressing force with which the finger presses the fiber optical plate, on one end surface of the fiber optical plate. 4. The control means outputs the image obtained from the output end face when the contact detection means detects the finger and the detection result of the pressure detection means reaches a predetermined value. 4. The fingerprint reading device according to claim 3, wherein control is performed by the image detecting means.