CN115082975A - Biometric Identification Methods - Google Patents

Abstract

A biological feature identification method is applied to a biological feature identification device. The biometric feature identification method comprises the steps of calculating a gray scale difference value of a first biometric feature image, defining a first voltage difference value according to the gray scale difference value, performing biometric feature sensing to obtain a second voltage difference value, and identifying whether the biometric feature is true according to the first voltage difference value and the second voltage difference value.

Description

Biometric Identification Methods

technical field

The present disclosure relates to a biometric identification method.

Background technique

Most of the current electronic devices have an identity authentication mechanism, and the way of using biometrics for identity recognition is a trend in recent years. A common authentication method is fingerprint recognition because fingerprint recognition is easy to integrate into electronic devices.

An electronic device that uses gray-scale images to identify fingerprints needs to extract multiple gray-scale images and perform image processing for fingerprint identification. However, this method takes a lot of time to extract images and calculate through algorithms, which makes it difficult to improve the efficiency of biometric identification.

In view of this, how to provide a biometric identification method that can solve the above problems is still the goal of research and development in the art.

SUMMARY OF THE INVENTION

A technical aspect of the present disclosure is a biometric identification method applied to a biometric identification device. The biometric identification device includes a light source, a photosensitive element and an integrated circuit.

In one embodiment, the biometric identification method includes calculating a gray level difference value of a first biometric image, defining a first voltage difference value according to the gray level difference value, performing biometric sensing to obtain a second voltage difference value, and A voltage difference value and a second voltage difference value identify whether the biometric feature is true.

In one embodiment, the step of defining the first voltage difference according to the grayscale difference includes performing analog-to-digital conversion on the grayscale difference to define the first voltage difference.

In one embodiment, when the second voltage difference is greater than the first voltage difference, the identification result of the biometric feature is yes.

In one embodiment, the step of calculating the grayscale difference value of the biometrics further includes defining the brightness of the light source as a first brightness; performing biometric sensing to generate a first biometric image; and performing image processing on the first biometric image to calculate the gray level difference of the first biometric image.

In one embodiment, the step of performing biometric sensing to obtain the second voltage difference further includes receiving the light reflected from the biometrics by the photosensitive element to generate optical leakage, and the integrated circuit deriving the second voltage difference according to the optical leakage.

In one embodiment, when the second voltage difference is smaller than the first voltage difference, the biometric identification result is no, and the biometric identification method further includes performing biometric sensing to generate a second biometric image and identifying the first biometric image. Two biometric images perform image processing to derive heart rate values.

In one embodiment, the biometric identification method further includes determining whether the heart rate value is in a heart rate interval.

In one embodiment, when the second voltage difference is smaller than the first voltage difference, the biometric identification result is no, and the biometric identification method further includes defining the brightness of the light source as the second brightness, and the second brightness is greater than the first brightness. a brightness; and performing biometric sensing to obtain a third voltage difference.

In one embodiment, the biometric identification method further includes identifying whether the biometric is true according to the first voltage difference value and the third voltage difference value.

In one embodiment, when the third voltage difference is greater than the first voltage difference, the biometric identification result is yes, and when the third voltage difference is smaller than the first voltage difference, the biometric identification result is no.

In the above-mentioned embodiment, the biometric identification method can convert the gray scale difference into a first voltage difference that can be used to determine whether the biometric is true, and define a second voltage difference according to the light leakage difference generated after the photosensitive element is illuminated. voltage difference. In the first stage of the biometric identification method, the first voltage difference value and the second voltage difference value are used for determination, so the steps of extracting an image and performing image processing by an image processing module can be omitted. In this way, the time for identifying the biometric feature can be shortened. In addition, the manner of defining the first voltage difference by the grayscale difference in the present disclosure is not limited to the fingerprint pattern. The difference in light leakage corresponding to the same gray level difference for different users is the same, so the biometric identification method of the present disclosure is not limited to a single user.

Description of drawings

FIG. 1 is a side view of a biometric identification device according to an embodiment of the present disclosure.

FIG. 2 is a block diagram of the biometric identification device of FIG. 1 .

3A and 3B are schematic diagrams of image processing flow.

FIG. 4 is a circuit diagram of a fingerprint sensing module.

FIG. 5 is a graph showing the relationship between light leakage and bias voltage of the photosensitive element.

6A-6B are flowcharts of a biometric identification method according to an embodiment of the present disclosure.

7A-7B are flowcharts of a biometric identification method according to another embodiment of the present disclosure.

【Symbol Description】

100: Biometric Identification Device

110: Light source

120: Fingerprint sensing module

122: Pixel circuit

1222: Thin Film Transistor Switch

1224: photosensitive element

124: Integrated Circuits

1242: Integrator

1244: scratchpad

1244A: first scratchpad

1244B: Second scratchpad

1244C: The third scratchpad

1246: The first switch

1248: Second switch

130: Protective layer

140: Analog to Digital Converter

150: Image processing module

160: Electronics

170A, 170B: Logic operation unit

180: Interval

190: Grayscale difference

200: finger

300, 400: Biometric Identification Methods

I: Recycle current

A: Sensing area

V _bias : bias voltage

V _ref : reference voltage

V _out : output voltage

V _data : data voltage

C1, C2: Curves

S1～S20: Steps

Detailed ways

Various embodiments of the present invention will be disclosed below with accompanying drawings, and for the sake of clarity, many practical details will be described together in the following description. It should be understood, however, that these practical details should not be used to limit the invention. That is, in some embodiments of the invention, these practical details are unnecessary. In addition, for the purpose of simplifying the drawings, some well-known and conventional structures and elements are shown in a simplified and schematic manner in the drawings. Also, the thicknesses of layers and regions in the drawings may be exaggerated for clarity, and like reference numerals refer to like elements in the description of the drawings.

FIG. 1 is a side view of a biometric identification device 100 according to an embodiment of the present disclosure. The biometric identification device 100 includes a light source 110 , a fingerprint sensing module 120 and a protective layer 130 . The biometric identification device 100 is used for fingerprint identification and heart rate calculation. When the finger 200 is pressed on the sensing area A, the light emitted by the light source 110 is reflected by the finger 200 . The pulse beats periodically so that the image generated by the reflected light received by the fingerprint sensing module 120 has gray scale changes. The heart rate value can be obtained by extracting the grayscale image of the fingerprint and performing image processing on it to calculate the grayscale variation frequency of the image. In the present disclosure, the light source 110 has a single wavelength band, as long as it is a wavelength band that the fingerprint sensing module 120 can absorb.

FIG. 2 is a block diagram of the biometric identification device 100 of FIG. 1 . The biometric identification device 100 includes a fingerprint sensing module 120 , an analog-to-digital converter 140 , an image processing module 150 and an electronic device 160 that are electrically connected to each other.

3A and 3B are schematic diagrams of image processing flow. When performing biometric sensing, the fingerprint sensing module 120 extracts a plurality of fingerprint grayscale images at fixed time intervals within a time period. For example, the fingerprint sensing module 120 can extract a fingerprint grayscale image every 0.1 seconds. The biometric image referred to here is the grayscale image of the fingerprint received by the sensing area A (see FIG. 1 ).

The image processing module 150 can calculate the average grayscale value of a specific area in each fingerprint grayscale image. For example, in the sensing area A pressed by the finger 200, an area with a range of approximately 0.1 inch by 0.1 inch is framed as the image processing range. Because a group of peaks and valleys in an adult fingerprint occupies a width of about 0.45 mm to 0.5 mm. Therefore, the range selected by the box must be at least greater than 0.5 mm by 0.5 mm, but the present disclosure is not limited thereto.

FIG. 3A shows the average grayscale value of 150 fingerprint grayscale images. FIG. 3B shows the average grayscale value of the 150 fingerprint grayscale images processed by the algorithm. FIG. 3B shows that after the high-frequency noise is reduced from the average grayscale value calculated by the image processing module 150 shown in FIG. 3A , the overall average value of the average grayscale value distribution is redefined as zero, and the average grayscale value distribution is obtained through calculation. Oscillation size results. The dashed line in Figure 3B marks the range where the oscillation magnitude is one. In this embodiment, when the oscillation size is greater than 1, it means that the grayscale image of the fingerprint in this interval can be used to detect the heart rate, that is, it means that the grayscale image of the fingerprint is from a living fingerprint.

FIG. 4 is a circuit diagram of the fingerprint sensing module 120 . The fingerprint sensing module 120 includes a pixel circuit 122 and an integrated circuit 124 that are electrically connected to each other. In this embodiment, the pixel circuit 122 includes a thin film transistor (TFT) switch 1222 and a photosensitive element 1224 . The thin film transistor switch 1222 is connected to a photosensitive element 1224, and the photosensitive element 1224 is a photodiode. The integrated circuit 124 includes an integrator 1242 and a register 1244 . The integrator 1242 is electrically connected to the thin film transistor switch 1222 .

Referring to Figure 4. Since the photosensitive element 1224 generates light leakage after being illuminated, the integrated circuit 124 generates a recharge current I. The recycle voltage corresponding to the recycle current I can be temporarily stored in the register 1244 through the integrator 1242 . V _bias is the bias voltage of the positive electrode of the photosensitive element 1224 , V _ref is the reference voltage, and V _out is the output voltage. When the first switch 1246 is turned on, the data voltage V _data can be reset to the reference voltage V _ref . When the second switch 1248 is turned on, the output voltage V _out can be recorded in the register 1244 . It should be understood that the circuit diagram shown in FIG. 4 is only an example, which is not intended to limit the present disclosure.

FIG. 5 is a graph showing the relationship between light leakage and bias voltage of the photosensitive element 1224 . As shown in FIG. 5 , the light leakage generated by the photosensitive element 1224 is different due to the reflected light that changes in brightness and darkness. The curve C1 and the curve C2 represent the relationship between the light leakage and the bias voltage generated by the photosensitive element 1224 when the pulse is diastolic and the pulse is contracting, respectively. The difference between the curve C1 and the curve C2 is the light leakage difference.

Refer to Figure 2. The biometric identification device 100 further includes a first register 1244A, a second register 1244B, a third register 1244C, a logic operation unit 170A, and a logic operation unit 170B. The logic operation unit 170A is configured to determine the difference between the values temporarily stored in the second register 1244B and the third register 1244C, and the logic operation unit 170B then determines the difference between the values temporarily stored in the first register 1244A. difference between values.

In this embodiment, the pulse beats periodically so that the light leakage generated by the photosensitive element 1224 has a difference, so the voltage difference corresponding to the light leakage change can be recorded by the integrated circuit 124 . The analog-to-digital converter 140 can convert the voltage difference value into a corresponding grayscale value, and can also convert the grayscale value into a voltage difference value. The electronic device 160 is a device having the fingerprint sensing module 120 , such as an electronic device with an identity authentication mechanism such as a mobile phone and a tablet.

The biometric identification method of the present disclosure uses the voltage difference as a criterion for identifying whether the fingerprint is real (whether the fingerprint is a living fingerprint), thereby achieving the effect of rapid identification. The detailed steps of the biometric identification method will be described below.

6A-6B are flowcharts of a biometric identification method 300 according to an embodiment of the present disclosure. Referring to FIG. 1 and FIG. 6A simultaneously. In step S1 of the biometric identification method, the brightness of the light source 110 is defined as the first brightness. For example, in this embodiment, the light of the light source 110 is reflected by a standard sheet with a reflectivity of 79%. When the gray-scale image received by the fingerprint sensing module 120 has a gray-scale average value of 180, the brightness of the light source is Defined as the first brightness of the light source 110 . The above-mentioned definition of the first brightness with the grayscale value 180 is only an example, as long as the biometric identification device 100 can clearly identify the grayscale value of the fingerprint grayscale image.

Referring to FIGS. 6A , 3A and 3B simultaneously. In step S2 of the biometric identification method, biometric sensing is performed to generate a biometric image, and image processing is performed on the biometric image to calculate a grayscale difference value of the biometric image. After the aforementioned image processing steps, the gray level difference value can be calculated from the average gray level value shown in FIG. 3A . For example, in the interval 180 shown in FIG. 3A , the gray level difference 190 is calculated to be 1.4. In other words, after calculating the gray-scale image of the fingerprint by the algorithm in this embodiment, it is obtained that the gray-scale difference value of 190 is greater than 1.4, which indicates that the gray-scale image of the fingerprint is from a living fingerprint.

It should be understood that the above detailed steps of image processing are only examples, which are not intended to limit the present invention. Those skilled in the art should be able to make adjustments according to actual needs, as long as the grayscale difference 190 for identifying whether the biometric image is from a living fingerprint can be calculated.

2 and 6A at the same time. In step S3 of the biometric identification method, the analog-to-digital converter 140 performs analog-to-digital conversion on the grayscale difference value 190 to obtain the first voltage difference value. In this embodiment, the first voltage difference can be converted into a gray-scale signal by the analog-to-digital converter 140 . Likewise, when the gray-scale difference 190 is known to be 1.4, the analog-to-digital converter 140 can convert the gray-scale difference 190 into a first voltage difference required for identifying whether the biometric feature is true.

2 and 6A at the same time. In step S4 of the biometric identification method, the first voltage difference is defined as the voltage difference to be generated by the pulse beat. In this step, the first voltage difference obtained by inversion is temporarily stored in the first register 1244A to be defined as the first voltage difference for identifying whether the fingerprint is real.

4 and 6A at the same time. In step S5 of the biometric identification method, biometric sensing is performed. After the light reflected by the fingerprint irradiates the photosensitive element 1224, the photosensitive element 1224 generates light leakage. In this step, the finger 200 is pressed on the sensing area A (see FIG. 1 ). The pulse beat causes the reflected light received by the fingerprint sensing module 120 to show a change in brightness and darkness, and thus causes the photosensitive element 1224 to generate a light leakage change with the pulse beat.

2 and 6A at the same time. In step S6 of the biometric identification method, the integrated circuit 124 temporarily stores back the charging voltage to obtain the second voltage difference. In this step, the integrated circuit 124 generates a recycle voltage corresponding to the difference in light leakage. For example, the rechargeable voltage during pulse diastole can be temporarily stored in the second register 1244B through the integrator 1242 . The rechargeable voltage during pulse systole can be temporarily stored in the third register 1244C through the integrator 1242 . The logic operation unit 170A determines the difference between the recharge voltages temporarily stored in the second register 1244B and the third register 1244C. In this way, the recharge voltage difference value corresponding to the difference in light leakage can be obtained, and the recharge voltage difference value can be defined as the second voltage difference value.

2 and 6A at the same time. In step S7 of the biometric identification method, it is determined whether the second voltage difference is greater than the first voltage difference. The logic operation unit 170B can determine the difference between the first voltage difference and the second voltage difference.

2 and 6A at the same time. In step S8 of the biometric identification method, when the second voltage difference is greater than the first voltage difference, the identification result is yes. Biometrics are determined as living fingerprints. The electronic device 160 can display the recognition result. In some embodiments, the image processing module 150 can selectively perform image processing to calculate the heart rate after steps S1 to S8 are completed, and display the heart rate value through the electronic device 160 .

If the second voltage difference is greater than the first voltage difference, it means that the grayscale difference of the fingerprint grayscale image generated by the pulse beat is greater than the grayscale difference 190 calculated above. However, since the present disclosure converts the gray-scale difference value 190 into the first voltage difference value first, the determination step can omit the time required for image extraction and image processing.

6A and 6B are also referred to. When the second voltage difference is smaller than the first voltage difference, the identification result is no. The biometric feature is determined to be a non-living fingerprint, and the steps in FIG. 6B will be continued to further identify whether the biometric feature is true. In other words, steps S1 to S7 of FIG. 6A are the first-stage identification process, and steps S9 to S14 of FIG. 6B are the second-stage identification process. When the identification result of the first-stage identification process is negative, continuing the second-stage identification process can avoid misjudgments and improve the accuracy of biometric identification.

Referring to Figure 6B. In step S9 of the biometric identification method, biometric sensing is performed again. In this step, the finger 200 is pressed on the sensing area A again (see FIG. 1 ), and the fingerprint sensing module 120 extracts the grayscale image of the fingerprint.

2 and 6B at the same time. In step S10 of the biometric identification method, the image processing module 150 performs image processing on the biometric image. For example, the image processing module 150 extracts 150 fingerprint grayscale images to calculate the average grayscale value.

Referring to Figure 6B. In step S11 of the biometric identification method, an algorithm is used to calculate the gray scale change frequency to obtain a heart rate value.

Referring to FIG. 6B , in step S12 of the biometric identification method, it is determined whether the heart rate value is within a reasonable heart rate interval. For example, in this embodiment, 50 to 120 heart beats per minute is used as a reasonable heart rate range, but this is not intended to limit the present disclosure.

2 and 6B at the same time. As shown in step S13, when the heart rate value is within a reasonable heart rate range, the identification result is yes and the second-stage identification process ends. Biometrics are determined as living fingerprints. The electronic device 160 can display the recognition result. In some embodiments, the electronic device 160 may optionally display the heart rate value after completing the identification step.

2 and 6B at the same time. As shown in step S14, when the heart rate value is outside the reasonable heart rate range, the identification result is no and the second-stage identification process ends. Biometrics are judged as non-living fingerprints. The electronic device 160 displays the recognition result.

As can be seen from the above, the biometric identification method of the present disclosure can convert the gray scale difference into a first voltage difference that can be used to determine whether the biometric is true, and define the difference according to the light leakage and electric leakage generated after the photosensitive element is illuminated. The second voltage difference. In the first stage of the biometric identification method, the first voltage difference value and the second voltage difference value are used for determination, so the steps of extracting an image and performing image processing by the image processing module 150 can be omitted. In this way, the time for identifying the biometric feature can be shortened. In addition, if the first-stage identification result is negative, the second-stage identification process can be performed to avoid misjudgment and improve the accuracy of biometric identification. In the present disclosure, the manner of defining the first voltage difference by the grayscale difference is not limited to the fingerprint pattern. The difference in light leakage corresponding to the same gray level difference for different users is the same, so the biometric identification method of the present disclosure is not limited to a single user.

7A-7B are flowcharts of a biometric identification method 400 according to another embodiment of the present disclosure. Steps S1 to S8 of the biometric identification method 400 are the same as those of the biometric identification method 300 shown in FIG. 6A (ie, the identification process in the first stage is the same), and will not be repeated here. The difference between the biometric identification method 400 and the biometric identification method 300 is that when the second voltage difference is smaller than the first voltage difference, steps S15 to 19 are followed, which is referred to as the third stage identification herein.

Referring to FIG. 1 and referring to FIG. 7B at the same time. In step S15 of the biometric identification method 400, the brightness of the light source 110 is defined as the second brightness. The second brightness is greater than the first brightness in step S1. For example, by reflecting light from a standard sheet with a reflectivity of 79%, the brightness of the light source when the grayscale image received by the fingerprint sensing module 120 has a grayscale value of 200 is defined as the second brightness. In this way, the probability of misjudgment caused by poor fingerprint reflection when the first brightness is used can be avoided. The above-mentioned definition of the second brightness with the grayscale value of 200 is only an example, as long as the second brightness is greater than the first brightness, and the biometric identification device 100 can clearly identify the grayscale value of the fingerprint grayscale image.

Referring to Figure 7B. In step S16 of the biometric identification method 400, biometric sensing is performed again. In this step, the finger 200 is pressed on the sensing area A again (see FIG. 1 ), and the fingerprint sensing module 120 extracts the grayscale image of the fingerprint.

Referring to FIG. 2 and referring to FIG. 7B at the same time. In step S17 of the biometric identification method 400, the integrated circuit 124 temporarily stores back the charging voltage to obtain the third voltage difference. In this step, the integrated circuit 124 generates a recharge voltage corresponding to the light leakage. The rechargeable voltage during the pulse diastole can be temporarily stored in the second register 1244B through the integrator 1242 . The rechargeable voltage during pulse systole can be temporarily stored in the third register 1244C through the integrator 1242 . The logic operation unit 170A determines the difference between the recharge voltages temporarily stored in the second register 1244B and the third register 1244C. In this way, the recharge voltage difference value generated by the light leakage difference can be obtained, and the recharge voltage difference value can be defined as the third voltage difference value.

2 and 7B at the same time. In step S18 of the biometric identification method 400, it is determined whether the third voltage difference is greater than the first voltage difference. The logic operation unit 170B can determine the difference between the first voltage difference and the third voltage difference.

2 and 7B at the same time. In step S19 of the biometric identification method, when the third voltage difference is greater than the first voltage difference, the identification result is yes. Biometrics are determined as living fingerprints. The electronic device 160 can display the recognition result. In some embodiments, the image processing module 150 can selectively perform image processing to calculate the heart rate after completing the identification steps S15 to S19 , and display the heart rate value through the electronic device 160 .

2 and 7B at the same time. In step S20 of the biometric identification method, when the third voltage difference is smaller than the first voltage difference, the identification result is no and the third-stage identification process ends. The electronic device 160 displays the recognition result.

To sum up, the biometric identification method of the present disclosure can convert the gray scale difference into a first voltage difference that can be used to determine whether the biometric is true, and define the difference according to the light leakage difference generated by the photosensitive element after lighting The second voltage difference. In the first-stage identification process of the biometric identification method, the first voltage difference value and the second voltage difference value are used for determination, so the steps of extracting an image and performing image processing by an image processing module can be omitted. In this way, the time for identifying the biometric feature can be shortened. In addition, if the result of the first-stage identification process is negative, the second-stage identification process or the third-stage identification process can be performed to avoid misjudgment and improve the accuracy of biometric identification. In the second-stage identification process, the method of calculating the heart rate can be used for biometric identification, and in the third-stage identification process, a larger light source brightness can be used for biometric identification. In the present disclosure, the manner of defining the first voltage difference by the grayscale difference is not limited to the fingerprint pattern. The difference in light leakage corresponding to the same gray level difference for different users is the same, so the biometric identification method of the present disclosure is not limited to a single user.

Although the present disclosure has been disclosed above in terms of embodiments, it is not intended to limit the present disclosure. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present disclosure. Therefore, the present disclosure The scope of protection shall be subject to the scope defined by the appended claims.

Claims (10)

1. A biological characteristic identification method is applied to a biological characteristic identification device, the biological characteristic identification device comprises a light source, a photosensitive element and an integrated circuit, and the biological characteristic identification method comprises the following steps:

calculating a gray scale difference value of the first biological characteristic image;

defining a first voltage difference value according to the gray scale difference value;

performing biometric sensing to obtain a second voltage difference; and

and identifying whether the biological feature is true according to the first voltage difference value and the second voltage difference value.

2. The method of claim 1, wherein the step of defining the first voltage difference according to the gray-scale difference comprises:

performing analog-to-digital conversion on the gray scale difference value to define the first voltage difference value.

3. The method according to claim 1, wherein the biometric identification result is yes when the second voltage difference is greater than the first voltage difference.

4. The method of claim 1, wherein the step of calculating the gray-scale difference of the biometric feature further comprises:

defining the brightness of the light source as a first brightness;

performing biometric sensing to generate a first biometric image; and

and performing image processing on the first biological characteristic image to calculate the gray-scale difference value of the first biological characteristic image.

5. The method of claim 4, wherein the step of performing biometric sensing to obtain the second voltage difference further comprises:

the light sensing element receives the light reflected by the biological characteristic to generate light leakage; and

the integrated circuit obtains the second voltage difference value according to the light leakage.

6. The method according to claim 4, wherein when the second voltage difference is smaller than the first voltage difference, the biometric identification result is negative, and the method further comprises:

performing biometric sensing to generate a second biometric image

Image processing is performed on the second biometric image to derive a heart rate value.

7. The biometric identification method as in claim 6, further comprising:

and judging whether the heart rate value is in the heart rate interval.

8. The method according to claim 4, wherein when the second voltage difference is smaller than the first voltage difference, the biometric identification result is negative, and the method further comprises:

defining the brightness of the light source as a second brightness, wherein the second brightness is greater than the first brightness; and

performing biometric sensing to obtain a third voltage difference.

9. The biometric method as recited in claim 8, further comprising:

and identifying whether the biological feature is true according to the first voltage difference value and the third voltage difference value.

10. The method according to claim 9, wherein when the third voltage difference is greater than the first voltage difference, the biometric identification result is yes;

when the third voltage difference is smaller than the first voltage difference, the biometric feature identification result is negative.

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