CN110543864A - Sensor and fake finger identification method - Google Patents
Sensor and fake finger identification method Download PDFInfo
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- CN110543864A CN110543864A CN201910841904.XA CN201910841904A CN110543864A CN 110543864 A CN110543864 A CN 110543864A CN 201910841904 A CN201910841904 A CN 201910841904A CN 110543864 A CN110543864 A CN 110543864A
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- finger
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06V—IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING
- G06V40/00—Recognition of biometric, human-related or animal-related patterns in image or video data
- G06V40/10—Human or animal bodies, e.g. vehicle occupants or pedestrians; Body parts, e.g. hands
- G06V40/12—Fingerprints or palmprints
- G06V40/1382—Detecting the live character of the finger, i.e. distinguishing from a fake or cadaver finger
Abstract
The invention provides a sensor and a fake finger identification method. The sensor includes a sensing unit and a processing unit. The sensing unit is used for sequentially obtaining first finger sensing data and second finger sensing data of the finger. The processing unit is coupled with the sensing unit. The processing unit is used for calculating a first physical quantity of the first finger sensing data and calculating a second physical quantity of the second finger sensing data. The processing unit calculates an absolute value of a difference between the first physical quantity and the second physical quantity. And when the processing unit judges that the absolute value is greater than the threshold value, the processing unit identifies the finger as a real finger. When the processing unit judges that the absolute value is smaller than or equal to the threshold value, the processing unit identifies the finger as a fake finger.
Description
Technical Field
The present invention relates to a sensing technology, and more particularly, to a sensor and a method for identifying a fake finger.
Background
In recent years, fingerprint sensing technology is widely applied to various electronic devices or terminal devices to provide various identity login or identity authentication functions. Generally, a user can press a finger on a fingerprint sensor to make the fingerprint sensor obtain a fingerprint image. The electronic device or the terminal equipment can obtain the fingerprint characteristics or the palm print characteristics by the fingerprint image for subsequent identification or verification operation. However, since the fake finger may also be designed to include a fingerprint, the fake finger may also pass identification or verification. Therefore, how to make fingerprint sensing have anti-counterfeiting effect is one of the currently important research directions in the field.
Disclosure of Invention
In view of the above, the present invention provides a sensor and a method for identifying a fake finger, which can effectively determine whether a sensed finger has a blood flow variation corresponding to a heartbeat, so as to effectively determine whether the sensed finger is a fake finger.
according to an embodiment of the present invention, a sensor of the present invention includes a sensing unit and a processing unit. The sensing unit is used for sequentially obtaining first finger sensing data and second finger sensing data of the finger. The processing unit is coupled with the sensing unit. The processing unit is used for calculating a first physical quantity of the first finger sensing data and calculating a second physical quantity of the second finger sensing data. The processing unit calculates an absolute value of a difference between the first physical quantity and the second physical quantity. And when the processing unit judges that the absolute value is greater than the threshold value, the processing unit identifies the finger as a real finger. When the processing unit judges that the absolute value is smaller than or equal to the threshold value, the processing unit identifies the finger as a fake finger.
according to the embodiment of the invention, the fake finger identification method comprises the following steps: sequentially obtaining first finger sensing data and second finger sensing data of the finger; calculating a first physical quantity of the first finger sensing data and calculating a second physical quantity of the second finger sensing data; calculating an absolute value of a difference between the first physical quantity and the second physical quantity; and when the absolute value is judged to be larger than a threshold value, identifying the finger as a real finger, and when the absolute value is judged to be smaller than or equal to the threshold value, identifying the finger as a fake finger.
Based on the above, the sensor and the method for identifying the fake finger of the present invention can perform specific calculation according to two physical quantities of the two finger sensing results to identify whether the sensed finger is a real finger or a fake finger.
In order to make the aforementioned and other features and advantages of the invention more comprehensible, embodiments accompanied with figures are described in detail below.
drawings
The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and together with the description serve to explain the principles of the invention.
FIG. 1 is a block diagram of a sensor according to an embodiment of the present invention;
FIG. 2 is a diagram illustrating a time-series variation of physical quantities according to an embodiment of the present invention;
Fig. 3 is a flowchart illustrating a fake finger identification method according to an embodiment of the invention.
Description of the reference numerals
100: a sensor;
110: a sensing unit;
120: a processing unit;
200: an electrocardiogram signal;
l1: a first physical quantity;
L2: a second physical quantity;
S310 to S370: a step of;
t1, t 2: the time point.
Detailed Description
Reference will now be made in detail to exemplary embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings and the description to refer to the same or like parts.
FIG. 1 is a block schematic diagram of a sensor according to an embodiment of the invention. Referring to fig. 1, the sensor 100 includes a sensing unit 110 and a processing unit 120. The sensing unit 110 is coupled to the processing unit 120. In the present embodiment, the sensor 100 may be an Optical (Optical) sensor or a capacitive (capacitance) sensor. The sensor 100 may be modularized and integrated into an electronic device, such as a Personal Computer (PC), an Access control device (Access control device), a Tablet PC (Tablet PC), or a Mobile phone (Mobile phone), and the invention is not limited thereto. In an embodiment, the sensor 100 may be a fingerprint sensor, and the sensing data of the finger obtained by the sensing unit 110 may be calculated by the internal processing unit 120, and then the result of the sensed finger identification may be directly output. In one embodiment, the sensor 100 can also provide the finger sensing data obtained by the sensing unit 110 to other back-end processing circuits of the electronic device for calculation and generation of the recognition result. After the sensor 100 recognizes the sensed finger as a real finger, the sensor 100 may continue to perform fingerprint sensing.
In the present embodiment, since the real finger has the blood flow variation, some physical characteristics of the real finger are also affected by the blood flow variation synchronously to have the corresponding physical quantity variation. In contrast, since the artificial finger does not have a change in blood flow, the artificial finger does not have any change in physical quantity corresponding to the change in blood flow. That is, the sensing unit 100 of the embodiment can obtain two finger sensing data of the finger at different times, and determine whether the finger has a physical quantity change that can respond to the blood flow change by analyzing the physical quantity difference between the two finger sensing data, thereby identifying the authenticity of the finger.
Fig. 2 is a time-series diagram of physical quantities according to an embodiment of the present invention. Therefore, referring to fig. 1 and 2, the curve 200 shown in fig. 2 reflects the physical quantity change of a real finger. In the present embodiment, the sensing unit 110 sequentially obtains the first finger sensing data and the second finger sensing data of the sensed finger at time t1 and time t2, respectively, and provides the finger sensing data to the processing unit 120. In one embodiment, the time t1 and the time t2 are separated by a time interval greater than 50 milliseconds, for example, but the invention is not limited thereto. Therefore, comparing with the curve 200 of fig. 2, the processing unit 120 can calculate the first finger sensing data to obtain the first physical quantity L1 and calculate the second finger sensing data to obtain the second physical quantity L2. And, the processing unit 120 further calculates an absolute value of a difference between the first physical quantity L1 and the second physical quantity L2. Then, the processing unit 120 determines whether the absolute value is greater than a threshold value to identify the sensed finger as a real finger or a fake finger.
In other words, in the curve 200 of the physical quantity change belonging to the real finger, two physical quantities corresponding to two arbitrary points separated by a time interval on the curve 200 should have a considerable difference in physical quantity in most cases. Therefore, the sensor 100 of the present embodiment can effectively identify the finger as a real finger or a fake finger by determining whether the difference between the first physical quantity L1 and the second physical quantity L2 obtained for the same finger at different times is enough to determine that the finger has a physical quantity change corresponding to the blood flow change. Further, it is to be noted that, since the physical quantity change of the real finger is synchronized with the blood flow change of the real finger, and the blood flow change corresponds to the heartbeat change, the curve change of the curve 200 shown in fig. 2 actually coincides with the Electrocardiogram (ECG) change of the subject.
In an embodiment, the threshold value may be a predetermined multiple times the standard deviation σ of the physical quantity, and the predetermined multiple may be 3, but the invention is not limited thereto. That is, in one embodiment, the processing unit 120 may perform the calculation as the following procedure (1) to identify the finger as a real finger or a fake finger according to whether the absolute value of the difference between the first physical quantity L1 and the second physical quantity L2 is greater than three times the standard deviation σ of the physical quantity. In addition, in another embodiment, the standard deviation σ of the physical quantity may be a standard deviation of a plurality of physical quantities obtained by the sensing unit 110 sensing the calibration box a plurality of times in advance, but the invention is not limited thereto.
Equation (1) of | L1-L2| > 3 ×. sigma … … … … … … …
Taking the Sensor 100 as an optical Sensor, the sensing unit 110 may be, for example, a complementary metal oxide semiconductor Image Sensor (CIS) and includes an Image sensing array (Image sensing array). Since the dermis of the real finger has a plurality of capillaries therein, the light reflected by the real finger attached to the sensing surface of the optical sensor to the optical sensor will have a brightness variation corresponding to the blood flow variation as the blood flow varies. In other words, the overall average brightness of the finger images obtained by the sensing unit 110 sensing the real finger changes with the blood flow, so that in an exemplary embodiment of the present invention, the sensing unit 110 can sequentially obtain the first finger image and the second finger image of the sensed finger. The processing unit 120 can calculate a first overall average luminance of a plurality of pixels of the first finger image and a second overall average luminance of a plurality of pixels of the second finger image. The processing unit 120 calculates an absolute value of a difference between the first overall average luminance and the second overall average luminance, and determines whether the absolute value is greater than a threshold value, wherein the threshold value is a preset multiple times a standard deviation of the overall average luminance. The predetermined multiple may be set to 3, but the invention is not limited thereto. Moreover, the sensing unit 110 can capture a plurality of reference images to the calibration box in advance, so as to calculate the global average brightness standard deviation according to a plurality of global average brightness of the plurality of reference images through the processing unit 120. Therefore, in this example embodiment, the sensor 100 can effectively identify the finger as a real finger or a fake finger by determining whether the difference between the two overall average brightness of two finger images obtained for the same finger at different times is sufficient to correspondingly reflect that the finger image of the finger has brightness variation corresponding to the variation in blood flow.
taking the sensor 100 as a Capacitive sensor, the sensing unit 110 may include a Capacitive sensing array (Capacitive sensing array). Since the dermis of the real finger has a plurality of capillaries therein, the real finger attached to the sensing surface of the capacitive sensor will have a conductivity change corresponding to the blood flow change as the blood flow changes. In other words, since the overall average conductivity of the capacitance sensing array of the sensing unit 110 in the process of sensing the real finger changes correspondingly with the blood flow of the real finger, in another exemplary embodiment of the invention, the sensing unit 110 may sense the finger twice consecutively and sequentially provide the sensing results to the processing unit 120. In detail, when the sensing unit 110 senses the finger for the first time, the processing unit 120 calculates an overall capacitance value variation of the plurality of capacitance units of the capacitance sensing array during the first sensing process to calculate the first overall average conductivity. Then, when the sensing unit 110 senses the finger for the second time, the processing unit 120 calculates the overall capacitance value variation of the plurality of capacitance units of the capacitance sensing array during the second sensing process to calculate the second overall average conductivity. The processing unit 120 calculates an absolute value of a difference between the first global average conductivity and the second global average conductivity, and determines whether the absolute value is greater than a threshold value, wherein the threshold value is a predetermined multiple times a standard deviation of the global average conductivity. The predetermined multiple may be set to 3, but the invention is not limited thereto. Moreover, the sensing unit 110 may sense the calibration box multiple times in advance, and calculate the global average conductivity standard deviation according to multiple global average conductivities of multiple sensing results through the processing unit 120. Thus, in this alternative exemplary embodiment, the sensor 100 can effectively identify a finger as a real finger or a fake finger by determining whether the difference between the two overall average conductivities of the capacitance sensor arrays obtained by sensing the same finger at different times is sufficient to correspondingly reflect that the finger has a conductivity change corresponding to the change in the blood flow.
fig. 3 is a flowchart of a fake finger recognition method according to an embodiment of the invention. The method for identifying a fake finger of the present embodiment can be applied to the sensor 100 shown in fig. 1, and can be described by combining the physical quantity variation shown in fig. 2. Referring to fig. 1 to 3, in step S310, the sensor 100 determines whether a finger is placed on the sensing region of the sensing unit 110. If not, the sensor 100 re-executes step S310. When the sensor 100 detects that a finger is placed on the sensing area of the sensing unit 110, the sensor 100 further determines whether the sensing area of the sensor 100 is completely covered by the finger in step S320. If yes, the sensor 100 continues to perform step S330. If not, the sensor 100 re-executes step S310.
It should be noted that the fake-finger identification method of the present embodiment can avoid the sensing of the false touch through the step S320, but the invention is not limited thereto. In one embodiment, in step S320, the sensor 100 may also determine whether the fingerprint feature of the fingerprint image obtained from the current pressing result of the finger is sufficient to avoid determining the finger with insufficient fingerprint feature. For example, the sensing unit 110 may pre-fetch a fingerprint image of a finger, and then the processing unit 120 determines whether the fingerprint image has a sufficient number of fingerprint features, or the processing unit 120 determines whether the fingerprint image satisfies a predetermined image condition, so as to determine whether the sensor 100 re-executes step S310 or continues to execute step S330.
in step S330, the sensing unit 110 sequentially obtains first finger sensing data and second finger sensing data of the sensed finger. The first finger sensing data and the second finger sensing data may be, for example, finger images provided by the image sensing array or sensing results provided by the capacitance sensing array. In step S340, the processing unit 120 of the sensor 100 calculates a first physical quantity L1 of the first finger sensing data and a second physical quantity L2 of the second finger sensing data. Next, in step S350, the processing unit 120 calculates an absolute value of a difference between the first physical quantity L1 and the second physical quantity L2, and determines whether the absolute value is greater than a threshold value. If the absolute value is greater than the threshold value, the sensor 100 identifies the sensed finger as a real finger in S360. Otherwise, if the absolute value is less than or equal to the threshold value, the sensor 100 identifies the finger as a fake finger in step S370. Therefore, the method for identifying a fake finger of the present embodiment can effectively identify the sensed finger as a real finger or a fake finger.
In summary, the sensor and the method for identifying the fake finger of the present invention can continuously sense two physical quantities of the finger at different time points, and determine whether the sensed finger has a blood flow change according to a difference result between the two physical quantities, thereby effectively identifying whether the sensed finger is a real finger or a fake finger.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (14)
1. A sensor, comprising:
a sensing unit for sequentially obtaining first finger sensing data and second finger sensing data of a finger; and
A processing unit coupled to the sensing unit for calculating a first physical quantity of the first finger sensing data, calculating a second physical quantity of the second finger sensing data, and calculating an absolute value of a difference between the first physical quantity and the second physical quantity,
Wherein when the processing unit determines that the absolute value is greater than a threshold value, the processing unit identifies the finger as a true finger, and when the processing unit determines that the absolute value is less than or equal to the threshold value, the processing unit identifies the finger as a fake finger.
2. The sensor of claim 1, wherein the sensor is an optical sensor and the sensing unit comprises an image sensing array,
The sensing unit is used for sequentially obtaining a first finger image and a second finger image of the finger, and the first physical quantity is a first overall average brightness of the first finger image and the second physical quantity is a second overall average brightness of the second finger image.
3. the sensor of claim 1, wherein the sensor is a capacitive sensor and the sensing unit comprises a capacitive sensing array,
The sensing unit is used for sequentially sensing the fingers, and the first physical quantity is a first overall average conductivity of the capacitance sensing array when the fingers are sensed for the first time, and the second physical quantity is a second overall average conductivity of the capacitance sensing array when the fingers are sensed for the second time.
4. the sensor of claim 1, wherein the threshold value is a predetermined multiple times a standard deviation of the physical quantity.
5. The sensor of claim 4, wherein the predetermined multiple is 3.
6. the sensor of claim 4, wherein the standard deviation of the physical quantity is determined according to a plurality of reference physical quantities of a plurality of reference sensing data, and the plurality of reference sensing data are generated by the sensing unit continuously retrieving the calibration box.
7. The sensor of claim 1, wherein the sensing unit is configured to acquire the first finger sensing data and the second finger sensing data at intervals of time, and wherein the intervals of time are greater than 50 milliseconds.
8. a fake finger identification method is characterized by comprising the following steps:
Sequentially obtaining first finger sensing data and second finger sensing data of the finger;
calculating a first physical quantity of the first finger sensing data and calculating a second physical quantity of the second finger sensing data;
Calculating an absolute value of a difference between the first physical quantity and the second physical quantity; and
And when the absolute value is judged to be larger than a threshold value, identifying the finger as a real finger, and when the absolute value is judged to be smaller than or equal to the threshold value, identifying the finger as a fake finger.
9. The method of claim 8, wherein the first and second finger sensing data are first and second finger images obtained by an image sensor array of an optical sensor, and the first physical quantity is a first global average luminance of the first finger image and the second physical quantity is a second global average luminance of the second finger image.
10. the method as claimed in claim 8, wherein the two finger sensing data are obtained by sequentially sensing the fingers through a capacitance sensing array of a capacitive sensor, and the first physical quantity is a first global average conductivity of the capacitance sensing array when the fingers are sensed for a first time, and the second physical quantity is a second global average conductivity of the capacitance sensing array when the fingers are sensed for a second time.
11. the method as claimed in claim 8, wherein the threshold is a predetermined multiple times a standard deviation of the physical quantity.
12. The sensor of claim 11, wherein the predetermined multiple is 3.
13. The method according to claim 11, wherein the standard deviation of the physical quantity is determined according to a plurality of reference physical quantities of a plurality of reference sensing data, and the plurality of reference sensing data are generated by the sensing unit continuously retrieving the calibration box.
14. The method of claim 8, wherein the first and second finger sensing data are obtained at intervals of time greater than 50 ms.
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| Application Number | Priority Date | Filing Date | Title |
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| US201862773205P | 2018-11-30 | 2018-11-30 | |
| US62/773,205 | 2018-11-30 |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112464866A (en) * | 2020-06-15 | 2021-03-09 | 神盾股份有限公司 | Fingerprint sensing device and fingerprint sensing method |
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| US6175641B1 (en) * | 1995-10-06 | 2001-01-16 | Dermo Corporation, Ltd. | Detector for recognizing the living character of a finger in a fingerprint recognizing apparatus |
| CN104978575A (en) * | 2015-05-12 | 2015-10-14 | 友达光电股份有限公司 | Fingerprint identification system and operation method thereof |
| CN106778674A (en) * | 2016-12-30 | 2017-05-31 | 珠海市魅族科技有限公司 | Fingerprint identification device and fingerprint identification method |
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| US6175641B1 (en) * | 1995-10-06 | 2001-01-16 | Dermo Corporation, Ltd. | Detector for recognizing the living character of a finger in a fingerprint recognizing apparatus |
| CN104978575A (en) * | 2015-05-12 | 2015-10-14 | 友达光电股份有限公司 | Fingerprint identification system and operation method thereof |
| CN106778674A (en) * | 2016-12-30 | 2017-05-31 | 珠海市魅族科技有限公司 | Fingerprint identification device and fingerprint identification method |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN112464866A (en) * | 2020-06-15 | 2021-03-09 | 神盾股份有限公司 | Fingerprint sensing device and fingerprint sensing method |
| TWI766474B (en) * | 2020-06-15 | 2022-06-01 | 神盾股份有限公司 | Fingerprint sensing device and fingerprint sensing method |
| CN112464866B (en) * | 2020-06-15 | 2024-02-27 | 神盾股份有限公司 | Fingerprint sensing device and fingerprint sensing method |
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Application publication date: 20191206 |