JP2000020684A - Fingerprint image input device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a fingerprint image input device which can surely perform living body identification in spite of no change in color information of the fingerprint image. SOLUTION: A finger F, which comes in contact with an inspection surface 12a of a transparent body 12, is irradiated with a probe light L1 having a wavelength of an area in which an absorption coefficient of oxidized hemoglobin is smaller than that of reduced hemoglobin, and a reference light L2 having a wavelength of an area in which the absorption coefficient of the oxidized hemoglobin and that of the reduced hemoglobin are almost identical from a living body identification light source 11. A transmitting light detection means 13 receives a transmission probe light L11 of the probe light L1 which transmits through inside the finger F and outputs an electric signal S2 in accordance with a light intensity of the light L11, and receives transmission reference light L12 transmitting the inside of the finger F and outputs an electrical signal, in accordance with the intensity of the light L12. Through both of the electrical signals S1 and S2 outputted from the transmission light detection means 13, a transmission light intensity ratio of the light intensity of the transmission probe light L11 and the light intensity of the transmission reference light L12 are obtained, and a living body identification means 15 identifies from this transmission light intensity ratio whether or not the finger F touching the inspection surface 12a is a living body.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a fingerprint image input device for inputting a fingerprint image of a finger to a fingerprint collating device or the like.

[0002]

2. Description of the Related Art In recent years, research on personal identification technology has been actively conducted in order to enhance security functions such as access to confidential documents stored in a computer, electronic commerce on a computer network, and entrance / exit to important facilities. ing. Above all, fingerprints have the property of being the same for all and life-long, and are used as important features for realizing personal identification, and fingerprint collation devices and the like have been developed. However, if a so-called replica of a fingerprint of a specific individual who has already been registered is used, security is not ensured. For this reason, it is necessary to identify whether the finger is a human finger, that is, a living body, and this kind of living body identification method has been proposed.

[0005] For example, FIG. 5 is a block diagram showing a configuration of a conventional fingerprint image input device having a biometric identification function disclosed in Japanese Patent Application Laid-Open No. 3-87981. In FIG. 5, 1
Is a light source for irradiating the light F to the finger F, 2 is a transparent body, a lens 2b is provided at one end via a diaphragm 2a, and light from the finger F contacting the detection surface 2c is provided at the other end. A mirror 2d that reflects light in the direction is provided. Reference numeral 3 denotes a color CCD (charge-coupled device, charge-charge device) having a color discriminating function of, for example, a red (R) component, a green (G) component, and a blue (B) component.
An image detector composed of a coupled device detects a fingerprint image of the finger F. Reference numeral 4 denotes an RGB separation circuit, and reference numeral 5 denotes a fingerprint image input processing means, which performs processing such as fingerprint collation using a fingerprint image detected by the image detector 3. Reference numeral 6 denotes a living body identification unit that includes a color misregistration correction circuit 6a and a color identification circuit 6b, and identifies a living body of the finger F.

In the living body identification means 6, a color misregistration correction circuit 6a corrects the color misregistration of the fingerprint image signal of each color (R, G, B), and the color discrimination circuit 6b provides the color misregistration corrected fingerprint image. Supply signal. The color identification circuit 6b compares and identifies the color change between the fingerprint image at the moment when the finger F contacts the inspection surface 2c and the fingerprint image after the finger F is pressed against the inspection surface 2c.
If the finger F is a living body, the fingerprint image at the moment when the finger F contacts the inspection surface 2c is reddish because the pressing force on the inspection surface 2c is small. However, since the fingerprint image after the finger F is pressed against the inspection surface 2c has a large pressing force on the inspection surface 2c, it is detected as a whitish flesh color. In this way, the change of the color information of the fingerprint image is used to determine whether the image is a living body.

[0005]

Since the conventional fingerprint image input device is configured as described above, for example, the color of the surface of the finger F cooled by a low temperature condition becomes whitish before it comes into contact with the inspection surface 2c. In the case of a flesh color, there is no change in color information due to the pressing force, so that there is a problem in that, despite being a living body, it is erroneously identified as not a living body. In addition, when the finger F is lightly touched to the inspection surface 2c, the color information hardly changes.
There is a problem that the identification is incorrect if the body is not a living body.
Furthermore, it is necessary to continuously monitor a certain period of time required to cause a change in the color information of the fingerprint image, and there is a problem that a certain period of time is required for biometric identification.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a fingerprint image input device capable of reliably identifying a living body without changing the color information of the fingerprint image. With the goal. Another object of the present invention is to provide a fingerprint image input device capable of shortening the time for biometric identification.

[0007]

In a fingerprint image input device according to the present invention, a finger which comes into contact with a test surface is irradiated with probe light and reference light, and a living body identification light source is provided inside the finger. An electric signal corresponding to the light intensity of the transmitted probe light and an electric signal corresponding to the light intensity of the transmitted probe light and an electric signal corresponding to the light intensity of the transmitted reference light are received. A finger that is in contact with the inspection surface from the light intensity of the transmission probe light and the light intensity of the transmission reference light corresponding to the two electric signals output from the transmission light detection means And a biometric identification means for identifying whether or not the biometric identification is performed.

In the fingerprint image input apparatus according to the present invention, a transparent body having an inspection surface, a living body identification light source for irradiating a finger contacting the inspection surface with probe light and reference light, and Receiving the transmitted probe light transmitted through the inside of the device, and an electric signal corresponding to the light intensity of the transmitted probe light,
Transmitted light detecting means for receiving the transmitted reference light transmitted through the inside of the finger as the reference light and outputting an electric signal corresponding to the light intensity of the transmitted reference light, and transmitting the electric signal according to both electric signals output from the transmitted light detecting means A living body identification means for determining a transmitted light intensity ratio between the light intensity of the probe light and the light intensity of the transmitted reference light, and identifying from the transmitted light intensity ratio whether the finger contacting the inspection surface is a living body or not. Things.

Further, of the reduced hemoglobin and the oxyhemoglobin contained in the blood of the finger, the probe light has a wavelength in a region where the extinction coefficient of oxyhemoglobin is smaller than the extinction coefficient of reduced hemoglobin, and the reference light is the oxyhemoglobin. The extinction coefficient and the extinction coefficient of reduced hemoglobin have wavelengths in substantially the same region.

[0010] The wavelength of the probe light is around 660 nm.

The transmitted light detecting means includes means for converting only light having the wavelength of the transmitted probe light into an electric signal and outputting the same, and means for converting only light having the wavelength of the transmitted reference light into an electric signal and outputting the same. Things.

Still further, the transmitted light detecting means converts the light having the wavelength of the transmitted probe light into an electric signal and outputs the electric signal;
It has a common means for converting light having the wavelength of the transmitted reference light into an electric signal and outputting the electric signal.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is a block diagram showing the configuration of the fingerprint image input device according to the first embodiment of the present invention. In FIG. 1, reference numeral 11 denotes a light source for identifying a living body, which converts probe light L1 and reference light L2 into, for example, glass,
Irradiation is performed on the finger F in contact with the inspection surface 12a provided on the transparent body 12 such as transparent plastic. Biological identification light source 11
As, for example, a semiconductor laser may be used,
It is not necessary to use light in a state close to coherent light such as laser output light, and the probe light L1 has a wavelength in the range of 600 to 700 nm, for example, about 660 nm, and a wavelength in the range of 800 to 900 nm, for example, 80.
One light emitting diode that irradiates incoherent light with the reference light L2 having a wavelength near 0 nm or a white light source is used.

Reference numeral 13 denotes a transmitted light detecting means. The transmitted probe light L11 and the transmitted reference light L12 emitted from the living body identification light source 11 and transmitted through the finger F are received via a lens 14. The transmitted light detecting means 13 includes, for example, a photoelectric conversion means 13a for transmission probe light such as a photodiode with a band-pass filter, and a photoelectric conversion means 1 for transmission reference light.
3b, and the transmission probe light L11 is photoelectrically converted by the transmission probe light photoelectric conversion unit 13a.
The transmitted reference light L12 is photoelectrically converted by the transmitted reference light photoelectric conversion means 13b to output an electric signal S2 corresponding to the light intensity of the transmitted reference light L12.

Reference numeral 15 denotes a living body identification means,
a and a comparison circuit 15b. In the division circuit 15a,
Transmitted probe light L1 output from transmitted light detection means 13
The electric signal S1 corresponding to the light intensity of the transmitted reference light L12
Then, the transmitted light intensity ratio S3 obtained by dividing by the electric signal S2 corresponding to the light intensity is output to the comparison circuit 15b. Comparison circuit 15
b, the transmitted light intensity ratio S output from the division circuit 15a
3 is compared with a preset upper limit value and lower limit value.
Outputs an identification signal S4 indicating whether or not is a living body.

Reference numeral 16 denotes a fingerprint image light source such as a light-emitting diode, which irradiates a finger F in contact with the inspection surface 12a with light L3. Reference numeral 17 denotes an image detector including a two-dimensional solid-state imaging device such as a color CCD, and the light L3 reflected by the finger F
13 is received via a lens 18 and a fingerprint image of the finger F is detected. The detected fingerprint image of the finger F is captured by the image capturing circuit 19. 20 is a fingerprint matching circuit,
The fingerprint image of the finger F is collated based on the identification signal S4 output from the comparison circuit 15b.

FIG. 2 is an explanatory diagram showing the extinction coefficient at each wavelength of oxyhemoglobin and reduced hemoglobin in human blood. The extinction coefficient is a unit representing light absorption for a certain concentration of a certain substance and a certain optical path length. The sum of the oxyhemoglobin concentration and the reduced hemoglobin concentration is the total hemoglobin concentration. 600 to 700 of probe light L1
At wavelengths in the nm range, for example, around 660 nm, the absorption coefficient of oxyhemoglobin is smaller than the absorption coefficient of reduced hemoglobin. Therefore, the higher the concentration of oxyhemoglobin, the lower the absorption of light, and the transmitted probe light L, which is transmitted light.
It is remarkable that the light intensity of No. 11 increases.

On the other hand, 800 to 90 corresponding to the reference light L2
At a wavelength in the region of 0 nm, for example, near 800 nm, the extinction coefficient of oxyhemoglobin and the extinction coefficient of reduced hemoglobin are substantially the same, so that the light of the transmitted reference light L12, which is transmitted light, regardless of the concentration of oxidized hemoglobin. The intensity is constant. Therefore, the transmitted reference light L12 transmitted through the finger F
It can be seen that the greater the light intensity of the transmission probe light L11 with respect to the light intensity of, the higher the concentration of oxyhemoglobin in the blood in the finger F.

Next, the operation will be described. Irradiated from the living body identification light source 11 to the finger F in contact with the inspection surface 12a,
The transmitted probe light L11 and the transmitted reference light L12 transmitted from the finger F are transmitted through the lens 14 to the transmitted light detecting means 13
Received. The transmission probe light L11 is photoelectrically converted by the transmission probe light photoelectric conversion unit 13a, and outputs an electric signal S1 corresponding to the light intensity of the transmission probe light L11. The transmitted reference light L12 is photoelectrically converted by the transmitted reference light photoelectric conversion means 13b, and outputs an electric signal S2 corresponding to the light intensity of the transmitted reference light L12.

The electric signal S1 and the electric signal S2 output from the transmitted light detecting means 13 are divided by the dividing circuit 15a into the electric signal S1 and the electric signal S2 to obtain a transmitted light intensity ratio S3. Is output to the comparison circuit 15b. The higher the transmitted light intensity ratio S3, the higher the concentration of oxyhemoglobin in the blood contained in the finger F. The transmitted light intensity ratio S3 output from the division circuit 15a is calculated by a comparison circuit 15b.
The comparison is made with a preset upper limit value and lower limit value. When the transmitted light intensity ratio S3 is between the upper limit and the lower limit, it is determined that the finger F is a living body, and when the transmitted light intensity ratio S3 is not between the upper limit and the lower limit, the finger F is And outputs the determination result as the identification signal S4.

On the other hand, the light L3 is radiated from the fingerprint image light source 16 to the finger F in contact with the inspection surface 12a, and the light L13 reflected by the finger F is received by the image detector 17 through the lens 18 so that the finger F The fingerprint image of is detected. The fingerprint image of the finger F captured by the image capturing circuit 19 is collated by the fingerprint collation circuit 20 when the identification signal S4 output by the comparison circuit 15b is a signal that determines that the finger F is a living body. But finger F
Is determined not to be a living body, the fingerprint matching circuit 20 does not perform matching.

As described above, according to the first embodiment of the present invention, the probe light L1 and the reference light L2 are applied to the finger F contacting the inspection surface 12a by the living body identification light source 11, and the transmitted light detecting means The electric signal S1 corresponding to the light intensity of the transmitted probe light L11 in which the probe light has passed through the inside of the finger and the electric signal S2 corresponding to the light intensity of the transmitted reference light L12 in which the reference light has passed through the inside of the finger at 13 The transmitted light intensity ratio S3 between the light intensity of the transmitted probe light and the light intensity of the transmitted reference light is obtained from the two electric signals S1 and S2 output by the living body identification means 15,
Whether the finger touching the test surface is a living body or not is identified based on the transmitted light intensity ratio, so even if there is no change in the color information of the fingerprint image, the living body can be reliably identified as a replica or a living body finger. can do.

Further, of the reduced hemoglobin and the oxyhemoglobin contained in the blood of the finger F, the probe light L1 has a wavelength in a region where the absorption coefficient of the oxyhemoglobin is smaller than that of the reduced hemoglobin, and the reference light L2 Since the extinction coefficient of oxyhemoglobin and the extinction coefficient of reduced hemoglobin are wavelengths in substantially the same region, the transmitted light intensity ratio between the transmitted probe light L11 and the transmitted reference light L12 becomes remarkable, and the fingerprint Even if there is no change in the color information of the image, the living body can be reliably identified whether the finger F is a replica or a living body finger.

The wavelength of the probe light L1 is 660n
m, the light intensity of the transmission probe light L11 becomes remarkably large, the transmission light intensity ratio between the light intensity of the transmission probe light L11 and the light intensity of the transmission reference light L12 becomes more conspicuous, and the color of the fingerprint image becomes higher. Even if there is no change in the information, the living body can be reliably identified whether the finger F is a replica or a living body finger.

Further, the transmitted light detecting means 13 includes a transmitting probe light photoelectric converting means 13a for converting only the light having the wavelength of the transmitted probe light into an electric signal and outputting the electric signal, and an electric signal converting only the light having the wavelength of the transmitted reference light. Since the transmission reference light conversion means 13b for converting the reference light and outputting the same, the finger F can be simultaneously irradiated with the probe light L1 and the reference light L2. For this reason, it is not necessary to continuously monitor a certain amount of time required to cause a change in the color information of the fingerprint image as in the conventional example, and the time for biometric identification can be reduced.

The wavelength of the reference light L2 is 800 to 900.
Although the wavelength in the range of nm is used, the absorption coefficient of oxyhemoglobin and the absorption coefficient of reduced hemoglobin may be substantially the same, and the same effect as described above can be obtained even with other wavelengths, for example, wavelengths in the range of 400 to 530 nm. . The division circuit 15a is obtained by dividing the electric signal S1 corresponding to the light intensity of the transmission probe light L11 output from the transmitted light detection means 13 by the electric signal S2 corresponding to the light intensity of the transmission reference light L12. Although the transmitted light intensity ratio S3 is output to the comparison circuit 15b, the transmitted light intensity difference obtained by calculating the difference between the electric signal S1 and the electric signal S2 is output to the comparison circuit 15b. It works.

Embodiment 2 FIG. FIG. 3 is a block diagram showing a configuration of the fingerprint image input device according to the second embodiment of the present invention. 3, the same reference numerals as those used in FIG. 1 indicate the same or equivalent parts, and a description thereof will be omitted. FIG. 3 differs from FIG. 1 in that a living body identification light source 21 for irradiating probe light L1 and a living body identification light source 22 for irradiating reference light L2 are separate. As the living body identification light source, for example, a semiconductor laser may be used. However, light in a state close to coherent light, such as laser output light, is not necessarily required. For the probe light L1 and the living body identification light source 22, a light emitting diode that emits incoherent light of the reference light L2 having any wavelength of 800 to 900 nm, or a white light source is used. The transmitted light detection means 23 is a single transmitted light photoelectric conversion means 23a such as a photodiode with a band-pass filter, and shares the transmission probe light photoelectric conversion means and the transmitted reference light photoelectric conversion means.

Next, the operation will be described. First, the probe light L1 is emitted from the living body identification light source 21 to the finger F in contact with the inspection surface 12a. At this time, the biological identification light source 2
2 does not irradiate the reference light L2. The transmitted probe light L11 emitted from the living body identification light source 21 to the finger F and transmitted from the finger F is transmitted through the lens 14 to the transmitted light photoelectric conversion unit 2.
3a, the light is photoelectrically converted, and the transmitted probe light L11
And outputs an electric signal S1 corresponding to the light intensity. Next, the finger F that has come into contact with the inspection surface 12a is irradiated with the reference light L2 from the living body identification light source 22. At this time, the living body identification light source 21 does not emit the probe light L1. That is, the light source 2 for biometric identification
1 and the light source 22 for living body identification are irradiated alternately. The transmitted reference light L12 emitted from the living body identification light source 22 to the finger F and transmitted from the finger F is received by the transmitted light photoelectric conversion unit 23a via the lens 14 and photoelectrically converted, and the light of the transmitted reference light L12 is emitted. An electric signal S2 corresponding to the intensity is output.

The electric signals S1 and S2 output from the transmitted light photoelectric conversion means 23a are recorded once,
a, the transmitted light intensity ratio S3 is obtained by dividing the electric signal S1 by the electric signal S2, and this transmitted light intensity ratio S3 is compared with the comparison circuit 15b.
Is output to The higher the transmitted light intensity ratio S3, the higher the concentration of oxyhemoglobin in the blood contained in the finger F. Transmitted light intensity ratio S3 output from division circuit 15a
Is compared with a preset upper limit value and lower limit value in a comparison circuit 15b. When the transmitted light intensity ratio S3 is between the upper limit and the lower limit, it is determined that the finger F is a living body, and when the transmitted light intensity ratio S3 is not between the upper limit and the lower limit, the finger F is And outputs the determination result as the identification signal S4.

According to the second embodiment of the present invention, the probe light L1 and the reference light L2 are applied to the finger F contacting the inspection surface 12a by the living body identification light sources 21 and 22. An electric signal S1 corresponding to the light intensity of the transmitted probe light L11 having the probe light transmitted through the finger and an electric signal S2 corresponding to the light intensity of the transmitted reference light L12 having the reference light transmitted through the finger are output. The transmission light intensity ratio S3 between the light intensity of the transmission probe light and the light intensity of the transmission reference light is determined from the two electric signals S1 and S2 output from the living body identification means 15, and the inspection surface is contacted based on the transmission light intensity ratio. Since it is identified whether the finger is a living body or not, even if the color information of the fingerprint image does not change,
The living body can be reliably identified as a replica or a finger of a living body.

Further, of the reduced hemoglobin and the oxyhemoglobin contained in the blood of the finger F, the probe light L1 is a wavelength in a region where the extinction coefficient of oxyhemoglobin is smaller than the extinction coefficient of reduced hemoglobin, and the reference light L2 is Since the extinction coefficient of oxyhemoglobin and the extinction coefficient of reduced hemoglobin have wavelengths in substantially the same region, the transmission probe light L
The transmitted light intensity ratio between the light intensity of the transmitted reference light L12 and the light intensity of the transmitted reference light L12 becomes remarkable, and even if the color information of the fingerprint image does not change,
The living body can be reliably identified whether the finger F is a replica or a living body finger.

The wavelength of the probe light L1 is 660n
m, the light intensity of the transmission probe light L11 becomes remarkably large, the transmission light intensity ratio between the light intensity of the transmission probe light L11 and the light intensity of the transmission reference light L12 becomes more conspicuous, and the color of the fingerprint image becomes higher. Even if there is no change in the information, the living body can be reliably identified whether the finger F is a replica or a living body finger.

Further, a single photoelectric conversion unit for transmitted light 23a converts the light of the wavelength of the transmission probe light L11 into an electric signal and outputs the electric signal, and a single photoelectric conversion unit for transmission light 23a. Since the transmission reference light photoelectric conversion means for converting light into an electric signal and outputting the same is shared, when the transmission probe light photoelectric conversion means and the transmission reference light photoelectric conversion means are separate, one of them deteriorates due to deterioration. When it changes,
Although an error occurs in the output of the division circuit 15a, in the case of the single transmitted light photoelectric conversion unit 23a, no error occurs in the output of the division circuit 15a even when the sensitivity changes due to deterioration. If the time interval for alternately irradiating the living body identification light source 21 and the living body identification light source 22 is shortened, the time for living body identification can be reduced.

Embodiment 3 FIG. 4 is a block diagram showing a configuration of a fingerprint image input device according to the third embodiment of the present invention. 4, the same reference numerals as those used in FIG. 3 indicate the same or equivalent parts, and a description thereof will be omitted. 4 differs from FIG. 3 in that the image detector 24 detects the fingerprint L of the finger F by receiving the light L13, which is the light L3 reflected by the finger F, through the lens 25. The data is captured by the capture circuit 19. When detecting a fingerprint image, the living body identification light source 21 and the living body identification light source 22 do not emit the probe light L1 and the reference light L2. Further, the image detector 24 is provided with the light source 2 for living body identification.
When the probe light L1 and the reference light L2 are irradiated on the finger F contacting the inspection surface 12a from the light source 1 and the living body identification light source 22, the probe light L1 and the reference light L2 are transmitted through the transmitted probe light L11 transmitted through the finger F. And transmitted reference light L12
Has a function as a transmitted light detection unit that receives light via the lens 25, performs photoelectric conversion, and outputs an electric signal corresponding to the light intensity of the transmitted probe light L11 and the transmitted reference light L12.

Next, the operation will be described. First, the probe light L1 is emitted from the living body identification light source 21 to the finger F in contact with the inspection surface 12a. At this time, the biological identification light source 2
2 does not irradiate the reference light L2. The transmitted probe light L11 emitted from the living body identification light source 21 to the finger F and transmitted from the finger F is received by the image detector 24 via the lens 25 and photoelectrically converted, and is converted according to the light intensity of the transmitted probe light L11. And outputs the generated electric signal S1. Next, the biometric identification light source 2
2 irradiates the finger F in contact with the inspection surface 12a with the reference light L2. At this time, the light source 21 for living body identification is the probe light L1.
Do not irradiate. That is, the light source for living body identification 21 and the light source for living body identification 22 are irradiated alternately. The transmitted reference light L12 emitted from the living body identification light source 22 to the finger F and transmitted from the finger F is transmitted through the lens 25 to the image detector 24.
And outputs the electric signal S2 corresponding to the light intensity of the transmitted reference light L12.

The electric signals S1 and S2 output from the image detector 24 are recorded once, and the electric signal S1 is divided by the electric signal S2 to obtain a transmitted light intensity ratio S3 by a dividing circuit 15a. The ratio S3 is output to the comparison circuit 15b. The higher the transmitted light intensity ratio S3, the higher the concentration of oxyhemoglobin in the blood contained in the finger F. The transmitted light intensity ratio S3 output from the division circuit 15a is compared by a comparison circuit 15b with a preset upper limit value and lower limit value. When the transmitted light intensity ratio S3 is between the upper limit and the lower limit, it is determined that the finger F is a living body, and when the transmitted light intensity ratio S3 is not between the upper limit and the lower limit, the finger F is And outputs the determination result as the identification signal S4.

According to the third embodiment of the present invention, the probe light L1 and the reference light L2 are applied to the finger F contacting the inspection surface 12a with the living body identification light sources 21 and 22, and the transmitted light detection means is used. The electric signal S corresponding to the light intensity of the transmitted probe light L11 in which the probe light has passed through the inside of the finger by the image detector 24.
1 and an electric signal S2 corresponding to the light intensity of the transmitted reference light L12 in which the reference light has passed through the inside of the finger, and the two probed electric signals S1 and S2 output by the living body identification means 15 emit light of the transmitted probe light. The transmitted light intensity ratio S3 between the intensity and the transmitted reference light intensity is determined, and it is determined whether or not the finger touching the inspection surface is a living body based on the transmitted light intensity ratio. Even if there is no change, the living body can be reliably identified as a replica or a living finger.

Further, of the reduced hemoglobin and the oxyhemoglobin contained in the blood of the finger F, the probe light L1 is a wavelength in a region where the extinction coefficient of oxyhemoglobin is smaller than that of the reduced hemoglobin, and the reference light L2 is Since the extinction coefficient of oxyhemoglobin and the extinction coefficient of reduced hemoglobin have wavelengths in substantially the same region, the transmission probe light L
The transmitted light intensity ratio between the light intensity of the transmitted reference light L12 and the light intensity of the transmitted reference light L12 becomes remarkable, and even if the color information of the fingerprint image does not change,
The living body can be reliably identified whether the finger F is a replica or a living body finger.

The wavelength of the probe light L1 is 660n
m, the light intensity of the transmission probe light L11 becomes remarkably large, the transmission light intensity ratio between the light intensity of the transmission probe light L11 and the light intensity of the transmission reference light L12 becomes more remarkable, and the fingerprint image Even if the color information does not change, the living body can be reliably identified whether the finger F is a replica or a living body finger.

Further, the image detector 24 as a single transmitted light detecting means converts the light having the wavelength of the transmitted probe light L11 into an electric signal and outputs the electric signal, and the wavelength of the transmitted reference light L12. The transmission reference light detection means for converting the light into an electric signal and outputting the same is shared, so that when the transmission probe light detection means and the transmission reference light detection means are separate and one of them changes sensitivity due to deterioration, Arithmetic circuit 15
Although an error occurs in the output of a, the division circuit 1 does not operate even when the sensitivity changes due to deterioration in the case of the single image detector 24.
No error occurs in the output of 5a. In addition, the living body identification light source 21
By shortening the time interval for alternately irradiating the living body identification light source 22 with the living body identification light source 22, the living body identification time can be reduced. Further, since the single image detector 24 also has the transmitted light detecting means, the size of the apparatus can be reduced.

[0041]

As described above, according to the fingerprint image input device of the present invention, the finger contacting the inspection surface with the living body identification light source is irradiated with the probe light and the reference light, and the probe is detected by the transmitted light detection means. An electric signal corresponding to the light intensity of the transmitted probe light whose light has passed through the inside of the finger and an electric signal corresponding to the light intensity of the transmitted reference light whose reference light has passed through the inside of the finger are output by the living body identification means. Since the light intensity of the transmission probe light and the light intensity of the transmission reference light according to the two electric signals output from the transmitted light detection means are used to determine whether or not the finger touching the inspection surface is a living body. Even if there is no change in the color information of the fingerprint image, the living body can be reliably identified as a replica or a living finger.

Further, probe light and reference light are applied to the finger contacting the inspection surface with the living body identification light source, and the transmitted light detecting means changes the probe light according to the light intensity of the transmitted probe light transmitted through the inside of the finger. A transmission probe that outputs an electric signal corresponding to the light intensity of the transmitted reference light transmitted through the inside of the finger and the reference light transmitted through the inside of the finger, and outputs the electric signal according to both electric signals output from the transmitted light detection unit by the living body identification unit. The transmitted light intensity ratio between the light intensity of the transmitted light and that of the transmitted reference light is determined, and it is determined from the transmitted light intensity ratio whether or not the finger touching the inspection surface is a living body. Even if there is no change in information, the living body can be reliably identified as a replica or a finger of a living body.

Also, of the reduced hemoglobin and oxyhemoglobin contained in the blood of the finger, the probe light has a wavelength in a region where the extinction coefficient of oxyhemoglobin is smaller than that of reduced hemoglobin, and the reference light is oxyhemoglobin. Since the extinction coefficient and the extinction coefficient of reduced hemoglobin are wavelengths in substantially the same region, the transmitted light intensity ratio between the transmitted probe light intensity and the transmitted reference light intensity becomes remarkable, and the color information of the fingerprint image changes. Even if there is no finger, the living body can be reliably identified as a replica or a living finger.

Since the wavelength of the probe light is around 660 nm, the light intensity of the transmitted probe light is significantly increased, and the transmitted light intensity ratio of the transmitted probe light to the transmitted reference light is increased. Becomes more conspicuous, and even if there is no change in the color information of the fingerprint image, the living body can be reliably identified as a replica or a living finger.

The transmitted light detecting means converts the light of the wavelength of the transmitted probe light into an electric signal and outputs the electric signal. The photoelectric conversion means for the transmitted probe light converts the light of the transmitted reference light only into the electric signal. Since it has the photoelectric conversion means for transmitted reference light to output, the finger can be irradiated with the probe light and the reference light simultaneously. For this reason, it is not necessary to continuously monitor a certain amount of time required to cause a change in the color information of the fingerprint image as in the conventional example, and the time for biometric identification can be reduced.

Still further, a single transmitted light detecting means converts the light having the wavelength of the transmitted probe light into an electric signal and outputs the electric signal, and the light having the wavelength of the transmitted reference light is converted into an electric signal. Since the transmission reference light photoelectric conversion means for converting and outputting is made common, when the transmission probe light photoelectric conversion means and the transmission reference light photoelectric conversion means are separate, one of them changes sensitivity due to deterioration. At this time, an error occurs in the output of the division circuit. However, in the case of a single transmitted light detection unit, no error occurs in the output of the division circuit even when the sensitivity changes due to deterioration.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a fingerprint image input device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing extinction coefficients at respective wavelengths of oxyhemoglobin and reduced hemoglobin in human blood.

FIG. 3 is a block diagram showing a configuration of a fingerprint image input device according to another embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration of a fingerprint image input device according to another embodiment of the present invention.

FIG. 5 is a block diagram showing a configuration of a conventional fingerprint image input device.

[Explanation of symbols]

 11, 21, 22 Light source for biometric identification 12 Transparent body 12a Inspection surface 13, 23, 24 Transmitted light detection means 15 Biometric identification means F Finger L1 Probe light L2 Reference light L11 Transmitted probe light L12 Transmitted reference light

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Teruo Usami 2-3-2 Marunouchi, Chiyoda-ku, Tokyo F-term (reference) 5B043 BA02 5B047 AA25 AA30 BA02 BC04 BC05 BC11

Claims (6)

[Claims] A living body identification light source for irradiating a probe light and a reference light to a finger in contact with an inspection surface; a probe light transmitted through the inside of the finger to receive a transmitted probe light; An electric signal corresponding to the light intensity of the transmitted light, and a transmitted light detecting unit that receives the transmitted reference light, in which the reference light has passed through the inside of the finger, and outputs an electric signal corresponding to the light intensity of the transmitted reference light, and From the light intensity of the transmission probe light and the light intensity of the transmission reference light according to the two electric signals output from the transmitted light detection means, it is determined whether or not the finger touching the inspection surface is a living body. Fingerprint image input device provided with a biometric identification unit that performs the identification. 2. A transparent body having an inspection surface, a living body identification light source for irradiating a finger in contact with the inspection surface with probe light and reference light, and a transmitted probe light in which the probe light has passed through the inside of the finger. And an electric signal corresponding to the light intensity of the transmission probe light, and an electric signal corresponding to the light intensity of the transmission reference light, wherein the reference light receives the transmission reference light transmitted through the inside of the finger. The transmitted light detecting means for outputting, and the transmitted light intensity ratio between the light intensity of the transmitted probe light and the light intensity of the transmitted reference light is obtained from the two electric signals output from the transmitted light detecting means, A fingerprint image input device including a living body identification unit that determines whether a finger contacting the inspection surface is a living body based on the ratio. 3. The probe light of the reduced hemoglobin and the oxyhemoglobin contained in the blood of the finger has a wavelength in a region where the absorption coefficient of the oxyhemoglobin is smaller than the absorption coefficient of the reduced hemoglobin, and the reference light is the reference light. 3. The fingerprint image input device according to claim 1, wherein the extinction coefficient of the oxyhemoglobin and the extinction coefficient of the reduced hemoglobin are substantially the same. 4. The fingerprint image input device according to claim 1, wherein a wavelength of the probe light is around 660 nm. 5. The transmitted light detecting means has means for converting only light having the wavelength of the transmitted probe light into an electric signal and outputting the same, and means for converting only light having the wavelength of the transmitted reference light into an electric signal and outputting the same. The fingerprint image input device according to any one of claims 1 to 3, wherein: 6. The transmitted light detecting means has a common means for converting light having a wavelength of the transmitted probe light into an electric signal and outputting the same, and a means for converting light having a wavelength of the transmitted reference light into an electric signal and outputting the same. The fingerprint image input device according to any one of claims 1 to 3, wherein: