JP2002049913A - Device and method for authenticating fingerprint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fingerprint authenticating device which does not bring about an increase in cost and whose mounting form is not restricted. SOLUTION: The photosensor area of an optical image sensor 2 has an effective image area where scattered light from the inner part of a finger 1 is converted into an image signal and a black reference area that does not react to light. The black reference area may be connected to a silicon substrate to be a matrix of the image sensor 2 by a thermal conductive film and is formed by providing an optical light shielding film on silicon dioxide covering a photosensor area. A black reference area reading means 3 reads dark currents of a photodiode (constituting the optical image sensor 2) before and after the finger 1 is placed on the image sensor 2, and a dark current comparing means 4 compares both current signals. A fingerprint collating means 5 fetches the image signal of the effective image area when a difference that is equal to or more than a prescribed value is detected in the image signal, and performs comparison by collating with a fingerprint database 8. A fingerprint deciding means 6 decides the finger 1 to be genuine only when the difference being equal to or more than the prescribed value is recognized as a result of comparing the image signal with the database 8 and also when characteristics coincide as a result of collating with the database 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fingerprint authentication device, and more particularly to a fingerprint authentication device and a fingerprint authentication method using an optical image sensor.

[0002]

2. Description of the Related Art In a modern information society, personal authentication is an urgent issue. This is because, in exchange for the convenience provided by computerization, there is a risk of leakage of privacy information and unauthorized intrusion into confidential organizations. As a countermeasure, for example, when using a cash card at a bank, a password must be entered, and when entering a computer room, a credential card must be read and a password must be entered. However, the number of personally owned cards is so large today that it is also called the card universal age, and management of such cards is troublesome. There is also a risk that the password or password may be forgotten, leaked or decrypted by others.

It has long been known to use fingerprints as a powerful means of personal authentication in place of passwords and passwords. Fingerprints can be sophisticated identification information of the human body and need not be memorized by the person. When a fingerprint is input to an image sensor, a general fingerprint collation device
The image processing of the fingerprint is performed by the recognition unit, and a feature point of the fingerprint called a minutiae is detected. Further, the similarity between the inputted fingerprint and the fingerprint on the database registered in advance is calculated from the minutiae. The similarity is represented by a numerical value called a score, and the higher the score, the higher the similarity between the input fingerprint and the fingerprint on the database. When the score exceeds a certain threshold value, it is recognized that the inputted fingerprint and the fingerprint registered in the database are the same.

However, such a fingerprint authentication apparatus cannot distinguish between a fingerprint of a living body and a replica (a replica of a fingerprint created in a non-living body). For this reason, for example, even if a photograph or the like obtained by elaborating a fingerprint of a living body is input, the fingerprint may be recognized as a living body fingerprint.

[0005] In order to eliminate such adverse effects, many proposals have been made for a long time. For example, as an example, laser light from a laser diode is transmitted through a finger to irradiate the light, and the output light has noise of speckle light. Japanese Patent Application No. 63-1 which determines whether a finger used for input of a fingerprint input device is a living body or a counterfeit product depending on whether or not the fingerprint is included.
No. 54962 (conventional example 1).

Another promising example is disclosed in JP-A-10-240942.
This is described as a “biological recognition device” in Japanese Patent Application Laid-Open Publication No. 2000-214873 (conventional example 2). In this device, as shown in FIG. 13, a fingerprint collator performs fingerprint input by sliding a finger 101 on a finger rest unit 102 during fingerprint collation. At that time, finger 1
01 and the biopotential deriving units 103-1 and 103-2 and the biopotential grounding unit 105. Finger 101
, The myoelectric potential fluctuates, and an electric signal responsive thereto is derived from the biopotential deriving units 103-1 and 103-2 and the biopotential grounding unit 105 and sent to the biosignal amplifying unit 106. The biological signal amplifying unit 106 amplifies and outputs the difference between the electric signals derived from the biopotential deriving units 103-1 and 103-2, using the potential of the biopotential grounding unit 105 as the ground potential. When the finger 101 is slid, the signal becomes a signal unique to a living body. However, when a fraudulent person slides a replica instead of the finger 101, the signal does not fluctuate. Part 108
Identifies a living body or not.

[0007]

However, in the above-mentioned prior art 1, since the light source for illuminating the finger is limited to an expensive laser diode for irradiating coherent light because of the necessity of using speckle light, There is a disadvantage that the device manufacturing cost is relatively high.

Further, in the prior art 2, since it is necessary to provide a biopotential deriving unit and a biopotential grounding unit in addition to the image sensor, there is a first problem that the cost is increased.

In addition, since the biopotential deriving unit is on the sensor surface, there is a second problem that the image capturing area is narrowed and it is necessary to take measures against electrostatic destruction of the biopotential deriving unit.

[0010] Furthermore, since it is necessary to slide a finger for the fingerprint collator in addition to the fingerprint identification, it is necessary to secure a space for sliding, which imposes restrictions on the mounting form of the device. There is a problem.

A first object of the present invention is to provide a biometric identification device having a simple configuration that does not increase the cost.

A second object of the present invention is to provide a compact biometric identification device which does not require any restrictions on the mounting form of the device.

[0013]

According to a first aspect of the present invention, there is provided a fingerprint authentication apparatus including an optical image sensor for converting scattered light from the inside of a finger into an image signal when a finger to be inspected is placed thereon. In order to determine the authenticity of the optical image sensor, a difference in temperature characteristics between before and after placing a finger on a photodiode constituting the optical image sensor is utilized.

According to a second aspect of the present invention, there is provided a fingerprint authentication apparatus comprising: an effective pixel area for converting scattered light from the inside of a finger to an image signal; An optical image sensor (2) having a photosensor area (62) consisting of a black reference area (64) that is insensitive to light.
A black reference area reading means (3) for reading the dark current of the black reference area (64) before and after the finger (1) is placed on the optical image sensor (2); and a dark current comparing means ( 4) and a fingerprint for reading the image signal from the effective pixel area (61), extracting the feature of the fingerprint, and comparing it with the fingerprint database (8) when the difference of the dark current is equal to or more than a predetermined value as a result of the comparison. Matching means (4); and fingerprint determining means (6) for determining the authenticity of the finger (1) based on the comparison result in the dark current comparing means (4) and the matching result in the fingerprint matching means (5). Features.

According to a third aspect of the present invention, there is provided a fingerprint authentication apparatus comprising: an effective pixel area (61) for converting scattered light from inside the finger (11) into an image signal when the finger (11) to be inspected is placed; An optical image sensor (1) having a photosensor area (62) consisting of a black reference area (64) that is insensitive to light.
2), a fingerprint database (18) storing the characteristics of the fingerprint and the characteristics of the process of changing the dark current due to the temperature change of the photodiode, and black before and after the finger (11) is placed on the optical image sensor (12). A black reference area reading means (13) for reading the dark current in the reference area, a dark current comparing means (14) for comparing the two dark currents, and if a difference of a predetermined value or more is detected in the dark current as a result of the comparison, A dark current change feature extraction means (19) for extracting a feature of a dark current change process accompanying a temperature change before and after placing a finger, and an image signal from an effective pixel area (61) are read to extract a feature of a fingerprint. The characteristics of the current change process and the characteristics of the fingerprint are stored in the fingerprint database (18).
And fingerprint identification means (16) for determining the authenticity of the finger (11) based on the result of the identification.

The difference in the temperature characteristics, the difference of the dark current of a predetermined value or more, or the characteristic of the dark current change process may be determined by the temperature difference before and after the finger placement or the difference in the dark current amplitude. The determination may be made based on the difference between the temperature gradient or the dark current gradient before and after the placement.

The optical image sensor (60) includes a photosensor region (62) composed of a group of photodiodes formed on a silicon substrate (66), a silicon dioxide film (65) covering the photosensor region, An optical light shielding film (63) that covers the periphery of the silicon dioxide film (65) and forms a black reference region (64) that does not react to light in a photosensor region (62) immediately below the periphery. Further, the optical light shielding film (73) is connected to the silicon substrate (76),
A heat conductive film (77) for transmitting the temperature of the placed finger to the silicon substrate (76) may be provided. Note that the heat conductive film (87) may be provided over the entire surface of the optical light shielding film (83). Further, the heat conductive film and the optical light shielding film may be integrated to form a light shielding heat conductive film (99).

According to the present invention, an optical device having an effective pixel region for converting scattered light from the inside of the finger into an image signal when a finger to be inspected is placed and a photosensor region comprising a black reference region which does not react to scattered light. Use an image sensor.
When the finger is placed on the optical image sensor, the dark currents in the black reference area before and after the finger are read, and the two dark currents are compared.
When a difference equal to or more than a predetermined value is detected in the dark current based on the result, the image signal from the effective pixel area is read to extract the feature of the fingerprint and collate with the fingerprint database. Then, the authenticity of the finger is determined based on the comparison result of the dark current and the fingerprint collation result.

The fingerprint characteristics and the characteristics of the process of changing the dark current accompanying the temperature change of the photodiode may be stored in the fingerprint database. In this case,
The dark current in the black reference area before and after the finger is placed on the optical image sensor is read and compared, and when a difference of a predetermined value or more in the dark current is detected as a result of the comparison, the dark current is accompanied by a temperature change before and after the finger placement. The feature of the dark current change process is extracted. Then, the image signal from the effective pixel area is read, the characteristics of the fingerprint are extracted, and the characteristics of the process of changing the dark current and the characteristics of the fingerprint are collated with the fingerprint database.

According to the present invention, the difference in temperature characteristics between before and after the placement of the finger of the photodiode constituting the optical image sensor is used to judge the authenticity of the finger. It is possible to provide a biometric identification device with a simple configuration that does not require invitation.

Further, the subject does not need to move the finger to determine whether or not the finger is a living body, so that a living body identification device having no restrictions on the mounting form can be provided.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A fingerprint authentication device according to the present invention includes an optical image sensor for converting scattered light from the inside of a finger into an image signal when a finger to be inspected is placed, and judges the authenticity of the finger. However, a difference in temperature characteristic between before and after placing a photodiode on a photodiode constituting an optical image sensor is used.

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a view showing a first embodiment of the present invention, in which an optical image sensor 2 for converting a fingerprint of a placed finger 1 into an image signal and a black image for reading a black reference area of the optical image sensor 2 are shown. Reference area reading means 3 and dark current comparing means 4 for comparing the reverse bias current (referred to as dark current) of the photodiode before and after the finger 1 is placed on the optical image sensor 2.
, Fingerprint matching means 5, fingerprint determination means 6, memory 7
And a fingerprint database 8. The means for registering fingerprint information in the fingerprint database 8 is not shown. Also, the method for registering fingerprint information is not different from the conventional method, and therefore the description is omitted.

In this embodiment, the finger 1 is illuminated by a light source (not shown), and scattered light from the inside of the finger 1 is received by the optical image sensor 2 which is in close contact with the finger 1. When the finger 1 is irradiated with light, scattered light having relatively high brightness is detected from the ridge portion of the fingerprint (the convex portion of the fingerprint) due to the contact with the optical image sensor 2, and the valley portion of the fingerprint (the fingerprint of the fingerprint) is detected. The scattered light having relatively low luminance is detected from the concave portion) by the influence of the gap generated between the optical image sensor 2 and the concave portion. Optical image sensor 2
Recognizes the fingerprint of the finger 1 based on the difference in luminance. Therefore, optical components such as a lens, a prism, and a fiber are not required, and unlike the conventional fingerprint authentication device using speckle light, there is no need to consider the wavelength of the light source. As a result, it is possible to use an optical image sensor 2 such as a two-dimensional CCD or a CMOS sensor having a matrix composed of ordinary photodiodes, which is advantageous in reducing the manufacturing cost of the device.

FIG. 3 shows the substrate temperature and dark current of the optical image sensor 20 when the finger 10 is not in contact with the optical image sensor 20, and FIG. 4 shows the case where the finger 10 is in contact with the optical image sensor 20. Shows substrate temperature and dark current. As is clear from comparison between FIG. 3 and FIG. 4, dark current when the finger 10 is in contact with the optical image sensor 20 (FIG. 4)
Is larger than the dark current when there is no contact (FIG. 3). This is due to the ambient temperature versus output voltage characteristics of the optical image sensor 20 illustrated in FIG. As is apparent from FIG. 5, the logarithm of the dark current increases in proportion to the temperature. Therefore, when the finger 10 comes into contact with the optical image sensor 20, the temperature of the finger becomes
0, increasing the substrate temperature and increasing the dark current. Conversely, when the temperature of the optical image sensor 20 is higher than the temperature of the finger 10, the substrate temperature is lowered and the dark current is reduced.

In the optical image sensor 2, as shown in FIG. 6, a black reference region 64 shielded from light by an optical light shielding film 63 is provided in a photo sensor region 62. In the black reference area 64, a dark current continues to flow even when the optical image sensor 2 is irradiated with light. Black reference area reading means 3
Reads the dark current in the black reference area of the optical image sensor 2 when the finger 1 is not in contact with the optical image sensor 2 and when the finger 1 is not in contact with the optical image sensor 2. The dark current is stored in the memory 7 as a dark current reference signal.

Upon receiving the fingerprint authentication message, the dark current comparison means 4 causes the subject to contact the finger 1 with the optical image sensor 2.
Is compared with the dark current reference signal stored in the memory 7.

The fingerprint collation means 5 includes the optical image sensor 2
Of the effective pixel area (a part of the photosensor area not covered by the optical light-shielding film), extract the minutiae of the fingerprint image therefrom, and extract the fingerprint stored in the fingerprint database 8. Fingerprint authentication of the finger 1 is performed by comparing with the image.

The fingerprint judging means 6 authenticates the finger 1 based on the comparison result of the dark current comparing means 4 and the collation result of the fingerprint collating means 5. That is, only when the dark current has a difference equal to or greater than a predetermined value and the fingerprint feature points match,
The fingerprint of the finger 1 is authenticated as a real fingerprint of the subject.

Referring to FIG. 6, FIG. 6A is a plan view of the first embodiment of the optical image sensor 2, and FIG. 6B is a sectional view. In the optical image sensor 60, a photosensor region 62 is formed on a silicon (Si) substrate 66, and the photosensor region 62 is protected by a silicon dioxide (SiO2) film 65. The silicon dioxide film 6 is formed on the silicon dioxide film 65 so that the effective pixel region 61 becomes like a window.
5 is covered with an optical light shielding film 63. As a result, the portion immediately below the optical light shielding film 63 in the photosensor region 62 becomes the black reference region 64 and does not react to the irradiated light.
Note that the finger 1 is placed on the silicon dioxide film 6 on the effective pixel area 61.
5 and the optical light-shielding film 63, and the temperature of the finger 1 is transmitted to the effective pixel area 61 and the black reference area 64 with the same heat conduction distance.

The conductive performance is better than that of the silicon dioxide film.
For example, a heat conductive film 77 made of a metal film is provided in FIG.
5 is a second embodiment of the optical image sensor 2 shown in FIG. The optical image sensor 70 is formed on the right side of the optical light shielding film 73 surrounding the periphery of the effective pixel area 71, and reaches the silicon substrate 76 through the optical light shielding film 73 and the silicon dioxide film 75. Therefore, the temperature of the finger 1 placed on the right optical light shielding film 73 can be efficiently transmitted to the silicon substrate 76.

FIG. 8 shows a third embodiment of the optical image sensor 2 in which the above-mentioned idea has been thoroughly implemented. The optical image sensor 80 has a structure in which a heat conductive film 87 is stretched over the entire area of an optical light shielding film 83 surrounding the periphery of an effective pixel area 81. From the heat conductive film 87 to the Si substrate 8
The bridge to 6 is sufficient at one point on the right when considering the effect.

FIG. 9 shows a fourth embodiment of the optical image sensor 2 in which the optical light shielding film 83 and the heat conductive film 87 in FIG. 8 are integrally formed. This optical image sensor 90
Is the same as that of the optical image sensor 80, but has a simple configuration.

Next, the fingerprint authentication processing in the present embodiment shown in FIG. 1 will be described with reference to the flowchart shown in FIG.

In FIG. 1, an optical image sensor 2 is guided to an analog / digital converter via an amplifier, and an image signal from a photodiode is converted into a digital signal. The converted digital signal is processed by a computer as shown in FIG. Each means of FIG. 1 constitutes this computer. The optical image sensor 2 may be any of those shown in FIGS. 6 to 9, but FIG. 6 will be used in the following description.

Initially, while the subject is not placing the finger 1 on the optical image sensor 2, the temperature of the silicon (Si) substrate 66 is as shown in FIG. The reason why the temperature is wavy in FIG. 3B is based on the natural change of the ambient temperature. However, the temperature is kept within a certain temperature range, and a large temperature change does not occur. Therefore, the dark current at this time changes at a constant current value as shown in FIG. 3C, and no large current change occurs. The black base area reading means 3 reads the black reference area 64 (Step S1 in FIG. 10). The read dark current is digitally converted and stored in the memory 7 of the computer as a dark current reference signal (step S2).

Next, when an authentication request message is displayed on the display of the computer (step S3), the subject to be tested puts the subject to be tested, that is, his / her living finger 1 on the optical image sensor 2. Then, it is placed over the effective pixel area 61 and the optical light-shielding film 63 and is brought into close contact therewith. At this time, the temperature of the finger 1 is transmitted to the black reference region 64, and the temperature of the black reference region 64 rises due to the temperature characteristics shown in FIG. FIG.
3B shows that a temperature change (gradient) 31 and a temperature difference 32 occur before and after the contact of the finger 1 from the time 30 of the finger 1 contact. As a result, the dark current is detected as a current change (gradient) 41 and a current difference 42 as shown in FIG. The black base area reading means 3 reads the black reference area 64
(Step S4).

The dark current comparing means 4 compares the dark current signal (after digital conversion) with the dark current reference signal stored in the memory 7 in step S2 (step S5). The comparison is made with the current difference 42. As a result, if a difference equal to or larger than the predetermined value of the dark current is not detected (step S6), the fingerprint determination unit 6 checks whether the number of readings has reached the limited number of times (step S7). Returning to S4, the reading of the black reference area 64 is continued. This means that even if the authentication request message is displayed, the subject
Is not necessarily placed on the optical image sensor 2, so that the determination is made by the dark current comparison means 4 for a predetermined period (step S6).
There is something to wait for.

When the difference of the dark current equal to or more than the predetermined value is not detected by the predetermined number of readings of the black reference area 64 (step S4) (steps S6 and S7), the fingerprint judging means 6 determines that the finger 1 is a replica. Judgment (Step S
8).

On the other hand, if a difference of the dark current equal to or more than the predetermined value is detected in step S6, the fingerprint collating means 5 fetches an image signal (this is fingerprint image information) from the effective pixel area 61 (step S9), After the conversion, the fingerprint feature points are extracted (step S10) and compared with the fingerprint data in the fingerprint database 8 (step S12). As a result, if the fingerprint feature points match, the fingerprint determination unit 6 determines the test subject as a valid registrant (step S13), and if not, determines the test subject as an unauthorized person (step S13).
14). It should be noted that the fingerprint database 8 is a well-known one that stores the characteristic points of the fingerprint.

As described above, in this embodiment, the finger 1 is determined by determining whether or not the finger 1 is a living body (steps S6 and S7) and determining whether or not the fingerprint itself matches (step S11). Is authentic or not, that is, authenticity is determined.

Next, a second embodiment of the present invention will be described.

FIG. 2 is a view showing a second embodiment, in which an optical image sensor 12 converts a fingerprint of a placed finger 11 into a current signal, and a black reference area readout of the optical image sensor 12 reads out a black reference area. Means 13; dark current comparing means 14 for comparing the dark current of the photodiode before and after the finger 11 is placed on the optical image sensor 12;
5, a fingerprint determining means 16, a memory 17, a fingerprint database 18, and a dark current change characteristic extracting means 19 for storing a change process of the dark current accompanying a temperature change and extracting the characteristic. The means for registering fingerprint information in the fingerprint database 18 is not shown.

Also in this embodiment, as in the first embodiment, the fingerprint of the finger 11 placed on the optical image sensor 12 is determined by the difference in luminance of the scattered light from the ridge and the valley of the fingerprint. Perform authentication. As means for this, the dark current characteristics shown in FIGS. 3, 4 and 5 are used, and the optical image sensor 12 shown in FIGS. 6 to 9 can be used in the same manner. Further, dark current and fingerprint image information read from the optical image sensor 12 are converted from analog to digital, and the processing according to the flowcharts shown in FIGS. 11 and 12 is also performed by the computer. The feature of the second embodiment resides in the data content of the fingerprint database 18 and the dark current change feature extracting means 19, and accordingly, the fingerprint determining means 16 also differs from the fingerprint determining means 6 in FIG.

In the first embodiment, the biological recognition (step S
6, S7) and fingerprint authentication (step S11) are performed separately. In the second embodiment, both are integrated. For this purpose, in the fingerprint database 18, the dark current change characteristic extracting means 19 stores the dark current change process accompanying the temperature change in the memory 1.
7 and extract its features to obtain a fingerprint database 18.
It was decided to store in. The fingerprint judging means 16 compares the fingerprint feature from the finger 11 and the feature of the dark current change process with the fingerprint feature and the feature of the dark current change process stored in the fingerprint database 18 so that the finger 11 can determine the registrant. Or unauthorized person.

FIG. 11 is a flowchart showing a process for storing a fingerprint in the fingerprint database 18 in the second embodiment.

The black base region reading means 13 indicates that the registrant
Is read on the optical image sensor 2 while the black reference area 64 is read (step T1 in FIG. 11). The read dark current is digitally converted and stored in the memory 17 of the computer as a dark current reference signal (step T).
2).

Next, an authentication request message is displayed on the display of the computer (step T 3), so that the registrant effectively puts the registered object, that is, his / her live finger 11 on the optical image sensor 12. It is placed over the pixel region 61 and the optical light shielding film 63 and is brought into close contact therewith. The black base area reading means 13 reads the black reference area 64 (Step T4).

The dark current comparing means 14 compares the dark current signal (after digital conversion) with the dark current reference signal stored in the memory 17 in step T2 (step T5). The comparison is made with the current difference 42. As a result of the comparison, in order to wait for the registrant to place the finger 11 on the optical image sensor 12, the process is continued until a difference of a dark current equal to or more than a predetermined value is detected (steps T6 and T4).

When a difference of the dark current equal to or more than the predetermined value is detected in Step T6, the dark current change characteristic extracting means 19 temporarily stores the dark current change process accompanying the temperature change in the memory 17 after digital conversion (Step T7). . Next, the dark current change feature extraction means 19 extracts the feature of the dark current change process stored in the memory 17 (step T8), and the fingerprint registration means
(Not shown). The fingerprint registration means (not shown) takes in the current of the effective pixel area 61 (step T9), extracts a fingerprint feature point after digital conversion (step T10), and combines the feature of the dark current change process with the fingerprint feature point. After the classification (step T11), the fingerprint database 18 is used as authentication information.
(Step T12).

Next, the fingerprint authentication process in the embodiment shown in FIG. 2 will be described with reference to the flowchart shown in FIG.

In FIG. 2, the optical image sensor 12 is guided to an analog / digital converter via an amplifier,
The image signal from the photodiode is converted to a digital signal. The converted digital signal is processed by a computer as shown in FIG. Each means in FIG. 2 constitutes this computer. In addition,
Although the optical image sensor 12 may be any of those shown in FIGS. 6 to 9, FIG. 6 will be used in the following description.

Initially, while the subject is not placing the finger 11 on the optical image sensor 12, the silicon substrate 66
Are as shown in FIG. 3 (B). FIG.
The reason why the temperature undulates in (B) is based on the spontaneous change of the ambient temperature. However, the temperature is kept within a certain temperature range, and no large temperature change occurs. Therefore, the dark current at this time changes at a constant current value as shown in FIG. 3C, and no large current change occurs. The black base area reading means 3 reads the black reference area 64 (Step U1 in FIG. 12). The read dark current is digitally converted and stored in the memory 17 of the computer as a dark current reference signal (step U2).

Next, an authentication request message is displayed on the display of the computer (step U3), and the subject to be examined, that is, his / her living finger 11
Is placed on the optical image sensor 12 over the effective pixel area 61 and the optical light shielding film 63 and is brought into close contact therewith. At this time, the temperature of the finger 11 is transmitted to the black reference region 64, and the temperature of the black reference region 64 rises due to the temperature characteristics shown in FIG. In FIG. 4 (B), the finger 11 comes in contact with the finger 11 from the time of contact 30.
This indicates that a temperature change (gradient) 31 and a temperature difference 32 occur before and after the contact. As a result, the dark current is detected as a current change (gradient) 41 and a current difference 42 as shown in FIG. The black base area reading means 13 reads the black reference area 64 (Step U4).

The dark current comparison means 14 compares the dark current signal (after digital conversion) with the reference signal stored in the memory 17 in step U2 (step U5). The comparison is
The current difference 42 is used. As a result, the process is continued until a difference equal to or more than the predetermined value of the dark current is detected (steps U6 and U6).
4). This is because the subject does not necessarily immediately put the finger 11 on the optical image sensor 12 even if the authentication request message is displayed, and is to wait for the finger 11. As in the first embodiment, If the difference between the dark current signals is not detected within the predetermined number of times, it is not determined that the replica is a replica (steps S6, S7, S8). The authentication of the fingerprint is entrusted to the fingerprint determination unit 16 based on the result of the comparison by the fingerprint authentication unit 15.

When a difference of the dark current equal to or more than the predetermined value is detected in step U6, the dark current change feature extracting means 19 temporarily stores the dark current change process accompanying the temperature change in the memory 17 after digital conversion (step T7). . Next, the dark current change feature extracting means 19 extracts the feature of the dark current change process stored in the memory 17 and passes it to the fingerprint matching means 15 (step U8). The fingerprint collation means 15 includes an effective pixel area 61
(Step U9), and the feature of the fingerprint is extracted (step U10). Then, the transferred characteristics of the dark current change process and the characteristics of the fingerprint are stored in the fingerprint data database 1.
8 (step U11). Finally, based on the comparison result, the fingerprint determination unit 16 determines that the subject is a registrant (step U12) if they match, and that the subject is an unauthorized person (step U13) if they do not match.

[0058]

According to the present invention, the difference in temperature characteristics between before and after placing a photodiode on an optical image sensor is used to judge the authenticity of a finger. The first effect of being able to provide a biometric identification device having a simple configuration without inviting can be obtained. .

Since the subject does not need to move the finger to determine whether or not the finger is a living body, a second advantage is provided in that a living body identification device having no restrictions on the mounting form can be provided. be able to.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of a fingerprint authentication device of the present invention.

FIG. 2 is a block diagram showing a second embodiment of the fingerprint authentication device according to the present invention;

FIG. 3 is a diagram illustrating a substrate temperature and a dark current characteristic of the optical image sensor when a finger is not in contact with the substrate;

FIG. 4 is a view showing the substrate temperature and dark current characteristics of an optical image sensor when a finger is in contact with the substrate;

FIG. 5 is a diagram showing output characteristics of a photodiode at dark time.

FIG. 6 is a diagram showing a first embodiment of the optical image sensor according to the present invention.

FIG. 7 is a diagram showing a second embodiment of the optical image sensor according to the present invention.

FIG. 8 is a diagram showing a third embodiment of the optical image sensor according to the present invention.

FIG. 9 is a diagram showing a fourth embodiment of the optical image sensor according to the present invention.

FIG. 10 is a flowchart showing a fingerprint authentication process in the first embodiment of the fingerprint authentication device of the present invention;

FIG. 11 is a flowchart showing fingerprint information registration processing in a second embodiment of the fingerprint authentication device of the present invention.

FIG. 12 is a flowchart showing a fingerprint authentication process in a second embodiment of the fingerprint authentication device of the present invention.

FIG. 13 is a block diagram showing an example of the related art.

[Explanation of symbols]

 1, 1, 10, 11 finger 2, 12, 20 optical image sensor 3, 13 black reference area reading means 4, 14 dark current comparing means 5, 15 fingerprint collating means 6, 16 fingerprint determining means 7, 17 memory 8, 18 fingerprint Database 19 Dark current change feature extraction means 30, 40 Finger contact 31 Temperature change 32 Temperature difference 41 Current change 42 Current difference 61, 71, 81, 91 Effective pixel area 62, 72, 82, 92 Photo sensor area 63, 73, 83 optical light shielding film 64, 74, 84, 94 black reference region 65, 75, 85, 95 silicon dioxide (SiO2) film 66, 76, 86, 96 silicon (Si) substrate 77, 87, 97 heat conductive film 78, 88,98 Substrate contact part 99 Light-shielding heat conductive film

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04L 9/00 673A

Claims (11)

[Claims] An optical image sensor for converting scattered light from the inside of the finger into an image signal when a finger to be inspected is placed thereon, wherein the optical image sensor is used to determine the authenticity of the finger. A fingerprint authentication apparatus characterized in that a difference in temperature characteristics between before and after the finger placement of a constituent photodiode is used. 2. An optical image having an effective pixel area for converting scattered light from inside the finger into an image signal when a finger to be inspected is placed and a photo sensor area comprising a black reference area which does not react to the scattered light. A black reference area reading unit that reads a dark current of the black reference area before and after the finger is placed on the optical image sensor; a dark current comparison unit that compares the two dark currents; and a dark current based on a result of the comparison. When a difference equal to or more than a predetermined value is detected, the image signal from the effective pixel area is read to extract the characteristics of the fingerprint and collate with a fingerprint database. A fingerprint authentication device comprising: a fingerprint determination unit that determines the authenticity of the finger based on a result of the comparison by the comparison unit. 3. An optical image having an effective pixel area for converting scattered light from the inside of the finger into an image signal when a finger to be inspected is placed and a photo sensor area comprising a black reference area which does not react to the scattered light. A sensor, a fingerprint database storing characteristics of a fingerprint and characteristics of a process of changing a dark current due to a temperature change of the photodiode, and reading a dark current of the black reference region before and after the finger is placed on an optical image sensor. A black reference area readout unit; a dark current comparison unit that compares the two dark currents; if a difference of a predetermined value or more in the dark current is detected based on the comparison result, the darkness caused by a temperature change before and after the finger placement is detected. A dark current change feature extracting means for extracting a feature of the current change process; reading an image signal from the effective pixel area to extract a feature of the fingerprint; A fingerprint collating means for collating the features of fine the fingerprint and the fingerprint database, the fingerprint authentication device is characterized in that a fingerprint determining means for determining the authenticity of the finger by collating results. 4. The method according to claim 1, wherein the difference in the temperature characteristic, the difference of the dark current of a predetermined value or more, or the characteristic of the dark current change process is determined based on a temperature difference before and after the finger placement or a difference in dark current amplitude. 4. The fingerprint authentication device according to claim 1, wherein: 5. The method according to claim 1, wherein the difference in the temperature characteristic, the difference of the dark current of a predetermined value or more, or the characteristic of the dark current changing process is determined by a difference in a temperature gradient or a dark current gradient before and after placing the finger. 4. The fingerprint authentication device according to claim 1, wherein: 6. The optical image sensor, comprising: a photosensor region including a photodiode group formed on a silicon substrate; a silicon dioxide film covering the photosensor region; and a periphery on the silicon dioxide film. 6. The fingerprint authentication device according to claim 1, further comprising: an optical light shielding film that forms a black reference region that does not react to the light in the photosensor region immediately below the periphery. 7. The fingerprint according to claim 6, wherein the optical light-shielding film is connected to the silicon substrate, and a heat conductive film is provided for transmitting the temperature of the placed finger to the silicon substrate. Authentication device. 8. The fingerprint authentication device according to claim 7, wherein the heat conductive film is provided over the entire surface of the optical light shielding film. 9. The optical image sensor includes: a photosensor region including a photodiode group formed on a silicon substrate; a silicon dioxide film covering the photosensor region; and a periphery on the silicon dioxide film. A light-shielding thermally conductive film that forms a black reference region that does not respond to the light in the photosensor region immediately below the periphery and that transmits the temperature of the placed finger to the silicon substrate. The fingerprint authentication device according to claim 1. 10. An optical system comprising: an effective pixel area for converting a scattered light from the inside of the finger into an image signal when a finger to be inspected is placed; and a photosensor area including a black reference area which does not react to the scattered light. A fingerprint authentication method using an image sensor, comprising: a step of reading dark current in the black reference area before and after the finger is placed on the optical image sensor; a step of comparing the two dark currents; and a result of the comparison. A step of reading an image signal from the effective pixel area when a difference of a dark current equal to or more than a predetermined value is detected, extracting a feature of the fingerprint and comparing it with a fingerprint database, and comparing the comparison result in the dark current comparing means with the fingerprint A step of judging the authenticity of the finger based on a result of the collation by the collation means. 11. An optical system comprising: an effective pixel area for converting a scattered light from the inside of the finger into an image signal when a finger to be inspected is placed; and a photosensor area including a black reference area which does not react to the scattered light. A fingerprint authentication method using an image sensor, comprising: a step of storing characteristics of a fingerprint and characteristics of a process of changing a dark current due to a temperature change of the photodiode in a fingerprint database; and placing the finger on an optical image sensor. Reading a dark current of the black reference region before and after the black reference region; comparing the two dark currents; and detecting a difference of a predetermined value or more in the dark current based on a result of the comparison. Extracting a characteristic of a dark current change process accompanying the change; reading an image signal from the effective pixel area to extract a characteristic of a fingerprint; Fingerprint wherein a step of collating the features with the fingerprint database, to have a procedure for determining the authenticity of the finger by collating results.