TW202016704A - Fingerprint identification method and electronic device using the same - Google Patents

Abstract

A fingerprint identification method and an electronic device using the same are provided. The electronic device includes a fingerprint sensor and a processor. The fingerprint sensor is configured to obtain a first fingerprint frame of a finger object. The first fingerprint frame is composed of a plurality of sub-frames, and the plurality of sub-frames each include a plurality of pixel values corresponding to different exposure times. The processor respectively captures a plurality of pixel groups having the same exposure time in the first fingerprint frame, and combines the plurality of pixel groups to generate a plurality of second fingerprint frames respectively corresponding to different exposure times. The processor generates a fingerprint image according to the plurality of second fingerprint frames, and determines whether a plurality of image blocks of the fingerprint image satisfy an image change condition in a time interval to determine that the finger object belongs to a real finger.

Description

Fingerprint identification method and electronic device using the same

The invention relates to a fingerprint identification technology, and in particular to a fingerprint identification method and an electronic device using the same.

With the evolution of fingerprint sensing technology, off-screen fingerprint sensing is one of the important development directions of current fingerprint sensing technology. The off-screen fingerprint sensing can use an optical fingerprint sensing architecture or an ultrasonic fingerprint sensing architecture. Among them, the optical fingerprint sensing architecture is currently widely used in various electronic products. Generally speaking, the optical fingerprint sensing architecture is composed of a panel, a light emitting source, and a photoelectric sensor, to provide illumination light to the finger object pressed on the panel by the light emitting source, and then pass the panel and the finger object Reflect the image light with fingerprint information to the photoelectric sensor. However, when the fake finger is pressed on the panel, the photoelectric sensor can also receive the image light with the fake fingerprint information, which causes the problem of information security. Therefore, how to effectively recognize fingerprint information from real fingers is one of the important topics in the field at present, and the solutions of several embodiments will be proposed below.

The invention provides a fingerprint identification method and an electronic device using the same, which can effectively determine whether a finger object used for fingerprint verification belongs to a real finger.

The electronic device of the present invention includes a fingerprint sensor and a processor. The fingerprint sensor is used to obtain the first fingerprint frame of the finger object. The first fingerprint frame is composed of multiple sub-frames, and the multiple sub-frames each include multiple pixel values corresponding to different exposure times. The processor is coupled to the fingerprint sensor. The processor analyzes the first fingerprint frame. The processor separately captures a plurality of pixel groups with the same exposure time in the first fingerprint frame, and combines the plurality of pixel groups to generate a plurality of second fingerprint frames corresponding to different exposure times, respectively. The processor generates a fingerprint image according to the plurality of second fingerprint frames. The processor determines whether a plurality of image blocks of the fingerprint image satisfy image change conditions in a time interval to determine whether the finger object belongs to a real finger.

The fingerprint identification method of the present invention includes the following steps: obtaining a first fingerprint frame of a finger object, wherein the first fingerprint frame is composed of a plurality of sub-frames, and each of the plurality of sub-frames includes multiple corresponding to different exposure times Pixel values; analyze the first fingerprint frame to separately capture multiple pixel groups with the same exposure time in the first fingerprint frame; combine the multiple pixel groups to generate multiple corresponding to different exposure times A second fingerprint frame; generating a fingerprint image according to the plurality of second fingerprint frames; and determining whether a plurality of image blocks of the fingerprint image satisfy the image change conditions in the time interval to determine whether the finger object belongs to a real finger.

Based on the above, the fingerprint identification method of the present invention and the electronic device using the same can obtain the first fingerprint frame by the fingerprint sensor, and can divide the first fingerprint frame into multiple second fingerprints according to multiple different exposure times A frame, so as to form a fingerprint image with the plurality of second fingerprint frames. Therefore, the electronic device of the present invention can effectively determine whether the finger object used for fingerprint verification belongs to a real finger by analyzing the fingerprint image. In addition, since the electronic device of the present invention only needs to obtain a first fingerprint frame to perform the real finger determination process, the fingerprint identification method and the electronic device using the same of the present invention also have quick identification and can effectively save the electronic The effectiveness of the computing resources of the device.

In order to make the above-mentioned features and advantages of the present invention more obvious and understandable, the embodiments are specifically described below in conjunction with the accompanying drawings for detailed description as follows.

In order to make the content of the present invention easier to understand, the following specific embodiments are taken as examples on which the present invention can indeed be implemented. In addition, wherever possible, elements/components/steps with the same reference numerals in the drawings and embodiments represent the same or similar components.

FIG. 1 is a functional block diagram of an electronic device according to an embodiment of the invention. Referring to FIG. 1, the electronic device 100 includes a processor 110 and a fingerprint sensor 120. The processor 110 is coupled to the fingerprint sensor 120. In this embodiment, the electronic device 100 may be a mobile phone, a tablet, a notebook, a desktop, a variety of portable electronic devices, etc., and the like may provide fingerprints Electronic products with identification functions. In this embodiment, the electronic device 100 can be used to provide a fingerprint recognition function, and has a function of recognizing genuine and fake fingers.

In this embodiment, the processor 110 may be a central processing unit (Central Processing Unit, CPU), or other programmable general-purpose or special-purpose microprocessor (Microprocessor), digital signal processor (Digital Signal Processor) , DSP), programmable controller, application specific integrated circuits (ASIC), programmable logic device (Programmable Logic Device, PLD), other similar processors or a combination of these processor circuits. The processor 110 can perform image processing and analysis on the fingerprint frame (Fingerprint frame) or fingerprint image (Fingerprint image) provided by the fingerprint sensor 120.

In this embodiment, the fingerprint sensor 120 may be an image sensor, which includes, for example, a charge coupled device (Charge Coupled Device, CCD) or a complementary metal oxide semiconductor (Complementary Metal-Oxide Semiconductor, CMOS). The invention is not limited. In addition, the electronic device 100 of this embodiment may further include a memory. The memory can be used to store the frames and images captured by the fingerprint sensor 120, and store related image processing programs that can be used to implement the fingerprint recognition method described in various embodiments of the present invention for the processor 110 to read And execute it.

FIG. 2 is a schematic structural diagram of an electronic device according to the embodiment of FIG. 1. Referring to FIGS. 1 and 2, the electronic device 100 may further include a panel 130 and a light emitting source (not shown). The fingerprint sensor 120 may be an optical fingerprint sensor (Optical fingerprint sensor), and is disposed below the panel 130. In this embodiment, the panel 130 may be a transparent substrate. The panel 130 is arranged along the plane formed by the first direction P1 and the second direction P2, and the front surface of the panel 130 faces the third direction P3. The first direction P1, the second direction P2, and the third direction P3 are perpendicular to each other. In this embodiment, when the finger object F is pressed on the panel 130 for fingerprint recognition, the light emitting source of the electronic device 100 can provide illumination light to the finger object F pressed on the panel 130 to make the finger object F reflect The image with fingerprint information is transmitted to the fingerprint sensor 120.

In this embodiment, the panel 130 may be a Light-Emitting Diode (LED) panel, and the light emission source may be disposed below the panel 130, but the present invention is not limited thereto. In an embodiment, the panel 130 may be an Organic Light-Emitting Diode (OLED) panel, and includes a plurality of pixel units arranged in an array. Therefore, when the finger object F is pressed on the panel 130, at least a part of the plurality of pixel units may serve as a light emission source to provide illumination light to the finger object F.

In this embodiment, if the finger object F is a real finger, when the finger object F is pressed against the panel 130, the blood flow (direction) BF of the microvessels of the skin surface S1 of the finger object F will follow the contact with the panel 130 Spread outward from the center of the finger. On the contrary, if the finger object F is a fake finger, when the finger object F is pressed against the panel 130, the skin surface S1 of the finger object F does not generate an outwardly spreading blood flow BF. Therefore, in order to effectively recognize whether the finger object F is a real finger. In this embodiment, the electronic device 100 will first obtain the first fingerprint frame through the fingerprint sensor 120 and analyze the first fingerprint frame before deciding whether to capture another fingerprint frame for fingerprint verification . This will be described in detail with the embodiments of FIGS. 3 to 6 below.

FIG. 3 is a schematic diagram of a first fingerprint frame according to an embodiment of the invention. Referring to FIGS. 1 to 3, during the pressing process of the finger object F toward the panel 130, the fingerprint sensor 120 may obtain the first fingerprint frame 300 of the finger object F. In this embodiment, the first fingerprint frame 300 is composed of multiple sub-frames 310_1~310_M, where M is a positive integer greater than 0. The sub-frames 310_1~310_M each include multiple pixel values corresponding to different exposure times (or shutter speeds). Taking the sub-frame 310_1 as an example, the sub-frame 310_1 may be composed of 8 pixels 311_1~311_8. The pixel values of the eight pixels 311_1~311_8 respectively correspond to different exposure times. For example, pixel 311_1 has the longest exposure time, and pixel 311_8 has the shortest exposure time. In this embodiment, first, the processor 110 may analyze the first fingerprint frame 300. The processor 110 separately extracts a plurality of pixel values having the same exposure time in the first fingerprint frame 300 to organize into a plurality of pixel groups. Then, the processor 110 further combines these pixel groups to generate 8 second fingerprint frames corresponding to different exposure times, respectively. Finally, in this embodiment, the processor 110 may sequentially arrange (or play) the second fingerprint frames according to the respective exposure time lengths of the second fingerprint frames to generate a fingerprint image. In other words, the processor 110 may combine pixels with the same exposure time in the first fingerprint frame 300 into one frame, and so on, to generate multiple frames with different exposure times. For example, if the first fingerprint frame 300 has 640×480 pixels (resolution), the eight second fingerprint frames may each have 160×240 pixels (resolution). However, it should be noted that the number of sub-frames of the first fingerprint frame and the number of second fingerprint frames of the present invention can be determined according to different fingerprint sensing requirements, and are not limited to those shown in FIG. 3.

4 is a schematic diagram of dividing a plurality of image blocks of a fingerprint image according to an embodiment of the invention. FIG. 5 is a diagram of brightness changes of multiple image blocks according to the embodiment of FIG. 4. Referring to FIGS. 1 to 5, the fingerprint image generated by sequentially arranging (or playing) the second fingerprint frames through the multiple exposure time lengths of the plurality of second fingerprint frames may be like the fingerprint image 400 of FIG. 4. In this embodiment, the fingerprint image 400 can be divided into a plurality of image blocks 410_1~410_8. Specifically, the processor 110 divides the fingerprint image 400 into eight image blocks 410_1 to 410_8. If the finger object F is a real finger, when the processor 110 plays the fingerprint image 400, the respective average brightness values B1~B8 of the eight image blocks 410_1~410_8 will ripple.

In more detail, if the finger object F is a real finger, as shown in FIG. 2, the blood flow BF of the finger object F will diffuse outward from the finger center in a ring-shaped manner. In contrast, since the respective exposure times of the above eight second fingerprint frames are different, for example, the second fingerprint frame with the shortest exposure time has the highest average brightness in the image block 410_1, and the exposure time The second shortest second fingerprint frame has the highest average brightness value in the image block 410_2. By analogy, the second fingerprint frame with the longest exposure time has the highest average brightness value in the image block 410_8. Therefore, in a time interval T, the fingerprint images played by the above eight second fingerprint frames in sequence will display the diffusion result of the blood flow BF corresponding to the finger object F, and display as ripple changes in the image screen The brightness changes. In other words, if the processor 110 determines that the brightness averages B1 to B8 of the image blocks 410_1 to 410_8 of the fingerprint image 400 have a ripple change in the time interval T, the processor 110 determines that the fingerprint image 400 meets the image change condition ( The first stage of anti-counterfeiting).

Therefore, as shown in FIG. 5, if the finger object F belongs to a real finger, when the finger object F is pressed against the panel 130, the blood flow BF of the finger object F diffuses outward from the finger center, so as the exposure time increases Increasing, the average brightness values B1~B8 corresponding to the positions of the blood flow BF spreading from inside to outside on these second fingerprint frames will continue to increase. That is to say, if the processor 110 determines that the brightness averages B1~B8 of the image blocks 410_1~410_8 of the fingerprint image 400 have ripple changes as shown in FIG. 5, the processor 110 can effectively determine whether the finger object F belongs to Real fingers.

6 is a schematic diagram of a third fingerprint frame according to an embodiment of the invention. Referring to FIG. 1, FIG. 2 and FIG. 6, after the processor 110 determines that the finger object belongs to a real finger, the processor 110 may then follow the respective exposure parameters and gain parameters of the plurality of second fingerprint frames And at least one of DC-offset parameters to select one of these second fingerprint frames has the best frame quality. Moreover, the processor 110 can operate the fingerprint sensor 120 according to the exposure time corresponding to the second fingerprint frame with the best frame quality to obtain the third fingerprint frame 600 of the finger object F used for fingerprint verification. In this embodiment, the processor 110 may analyze the third fingerprint frame 600 to determine again whether the finger object F belongs to a real finger (second-stage anti-counterfeiting).

Specifically, since the slope-to-valley slope change of the fingerprint of a real finger has a certain degree of clutter, and the slope-to-valley slope change of the fingerprint of a fake finger has a fixed slope change, so as long as the fingerprint image is judged Whether the fingerprint pattern change has a certain degree of clutter can effectively determine whether the finger object F belongs to a real finger. Therefore, in this embodiment, the processor 110 can arbitrarily select the frame blocks 610_1~610_8 at multiple positions of the third fingerprint frame 600 for analysis. The processor 110 may analyze the respective fingerprint texture changes of the frame blocks 610_1~610_8 in the third fingerprint frame 600 to obtain multiple criteria for the respective fingerprint texture changes of the frame blocks 610_1~610_8 Difference (or random variable (Random Variable, RV)), where the fingerprint texture change refers to the change in the slope from the peak to the valley of the fingerprint. In this embodiment, the processor 110 may determine whether the standard deviations of the frame blocks 610_1 to 610_8 are respectively greater than the first predetermined threshold to determine whether the finger object F is a real finger.

However, in an embodiment, the processor 110 may also add up the standard deviations of the frame blocks 610_1~610_8 to determine the corresponding standard deviations of the frame blocks 610_1~610_8. Whether the sum is greater than the second preset threshold to determine whether the finger object F belongs to a real finger. In addition, it should be noted that the number of frame blocks in the third fingerprint frame of the present invention can be determined according to different fingerprint analysis requirements, and is not limited to that shown in FIG. 6.

7 is a flowchart of a fingerprint identification method according to an embodiment of the invention. Referring to FIGS. 1, 2, and 7, the fingerprint identification method of this embodiment can be applied to at least the electronic device 100 of the embodiments of FIGS. 1 and 2, so that the electronic device 100 can perform the following steps S710-S750. In step S710, the fingerprint sensor 120 may obtain the first fingerprint frame of the finger object F, wherein the first fingerprint frame is composed of a plurality of sub-frames, and each of the sub-frames includes multiple corresponding to different exposure times. Pixel values. In step S720, the processor 110 may analyze the first fingerprint frame to separately capture a plurality of pixel groups with the same exposure time in the first fingerprint frame. In step S730, the processor 110 combines the pixel groups to generate a plurality of second fingerprint frames corresponding to different exposure times. In step S740, the processor 110 generates fingerprint images according to the second fingerprint frames. In step S750, the processor 110 determines whether the plurality of image blocks of the fingerprint image satisfy the image change condition in the time interval to determine whether the finger object F belongs to a real finger. Therefore, the fingerprint identification method of the present invention can effectively determine whether the finger object F used for fingerprint verification belongs to a real finger.

In addition, regarding the device features of the electronic device 100 of this embodiment, as well as other judgment methods or other implementation methods of the fingerprint identification method, reference may also be made to the descriptions of the above embodiments of FIGS. 1 to 6 to obtain sufficient teaching, suggestions, and implementation. Explanation, so I won’t go into details.

In summary, the fingerprint identification method of the present invention and the electronic device using the same can first obtain a first fingerprint frame with multiple pixel values at different exposure times to correspondingly generate multiple second fingerprint frames Then, it can be analyzed whether the fingerprint image composed of these second fingerprint frames meets the preset image change conditions to determine whether the finger object is a real finger (first-stage anti-counterfeiting). When the first stage of anti-counterfeiting passes, the electronic device of the present invention can first determine the appropriate exposure time based on these second fingerprint frames to obtain a third fingerprint frame, and then can analyze multiple frames of the third fingerprint frame Whether the standard deviation of the fingerprint slope change of the block is higher than the preset threshold value, in order to judge whether the finger object is a real finger again (second-stage anti-counterfeiting). When the second stage of anti-counterfeiting passes, the electronic device of the present invention can directly perform fingerprint verification on the third fingerprint frame. Therefore, the fingerprint identification method of the present invention and the electronic device using the same can effectively determine whether the finger object used for fingerprint verification belongs to a real finger, and can quickly identify and effectively save the computing resources of the electronic device to obtain a good picture Like quality fingerprint frame, to facilitate fingerprint verification.

Although the present invention has been disclosed as above with examples, it is not intended to limit the present invention. Any person with ordinary knowledge in the technical field can make some changes and modifications without departing from the spirit and scope of the present invention. The scope of protection of the present invention shall be subject to the scope defined in the appended patent application.

100: Electronic device 110: Processor 120: Fingerprint sensor 130: Panel 300: First fingerprint frame 310_1~310_M: Subframe 311_1~311_8: Pixel 400: Fingerprint image 410_1~410_8: Image block 600: No. Three fingerprint frames 610_1~610_8: frame block BF: blood flow B1~B8: average brightness F: finger objects P1, P2, P3: direction S710~S750: steps

FIG. 1 is a functional block diagram of an electronic device according to an embodiment of the invention. FIG. 2 is a schematic structural diagram of an electronic device according to the embodiment of FIG. 1. FIG. 3 is a schematic diagram of a first fingerprint frame according to an embodiment of the invention. 4 is a schematic diagram of dividing a plurality of image blocks of a fingerprint image according to an embodiment of the invention. FIG. 5 is a diagram of brightness changes of multiple image blocks according to the embodiment of FIG. 4. 6 is a schematic diagram of a third fingerprint frame according to an embodiment of the invention. 7 is a flowchart of a fingerprint identification method according to an embodiment of the invention.

100: electronic device

110: processor

120: Fingerprint sensor

Claims (18)

An electronic device includes: a fingerprint sensor for obtaining a first fingerprint frame of a finger object, wherein the first fingerprint frame is composed of a plurality of sub-frames, and the sub-frames each include a corresponding Multiple pixel values at different exposure times; and a processor coupled to the fingerprint sensor for analyzing the first fingerprint frame, wherein the processor separately captures the same exposure in the first fingerprint frame Multiple pixel groups at a time, and combining the pixel groups to generate multiple second fingerprint frames corresponding to different exposure times, wherein the processor generates a fingerprint image based on the second fingerprint frames, and The processor determines whether a plurality of image blocks of the fingerprint image satisfy an image change condition in a time interval to determine whether the finger object belongs to a real finger. The electronic device as described in item 1 of the patent application range, wherein the processor arranges the second fingerprint frames according to the respective exposure time lengths of the second fingerprint frames to generate the fingerprint image. The electronic device as described in item 1 of the patent application scope, wherein when the processor determines that the average brightness of the image blocks of the fingerprint image has a ripple change in the time interval, the processor determines the The fingerprint image satisfies the image change condition. The electronic device as described in item 1 of the patent application scope, wherein the image blocks are sequentially arranged from the image center of the fingerprint image outwards. The electronic device as described in item 1 of the patent application scope, wherein a first pixel amount of the first fingerprint frame is higher than a plurality of second pixel amounts of the second fingerprint frames. The electronic device as described in item 1 of the patent application range, wherein the processor selects the second fingerprint frames according to at least one of an exposure parameter, a gain parameter, and a DC offset parameter One of the second fingerprint frames, and operating the fingerprint sensor according to the exposure time corresponding to one of the second fingerprint frames to obtain a first of the finger object for a fingerprint verification Three fingerprint frames. The electronic device as described in item 6 of the patent application scope, wherein the processor analyzes the respective fingerprint texture changes of the plurality of frame blocks in the third fingerprint frame to obtain information about each of the frame blocks Multiple standard deviations of other fingerprint patterns, and the processor determines whether the standard deviations are each greater than a first predetermined threshold to determine whether the finger object belongs to the real finger. The electronic device as described in item 7 of the patent application range, wherein the processor determines whether the sum of the standard deviations of the frame blocks is greater than a second predetermined threshold to determine whether the finger object belongs to the real finger . The electronic device as described in item 1 of the patent application scope further includes: a panel; and a light emitting source coupled to the processor for providing an illumination light to the finger object, wherein the light emitting source is disposed at the Below the panel, wherein the fingerprint sensor is an optical fingerprint sensor, and is disposed below the panel, wherein the fingerprint sensor receives an image light having fingerprint information reflected by the finger object. The electronic device as described in item 9 of the patent application range, wherein the panel is an organic light-emitting diode panel, and the organic light-emitting diode panel includes a plurality of pixel units arranged in an array, wherein when the finger object is placed on On the organic light emitting diode panel, at least a part of the pixel units serve as the light emission source to provide the illumination light to the finger object. A fingerprint identification method includes: obtaining a first fingerprint frame of a finger object, wherein the first fingerprint frame is composed of a plurality of sub-frames, and the sub-frames each include multiple corresponding to different exposure times Pixel value; analyze the first fingerprint frame to separately capture a plurality of pixel groups with the same exposure time in the first fingerprint frame; combine the pixel groups to generate a plurality of first corresponding to different exposure times Two fingerprint frames; generating a fingerprint image based on the second fingerprint frames; and determining whether a plurality of image blocks of the fingerprint image satisfy an image change condition in a time interval to determine whether the finger object belongs to a real finger. The fingerprint identification method as described in item 11 of the patent application range, wherein the step of generating the fingerprint image based on the second fingerprint frames includes: arranging the fingerprint images according to respective exposure time lengths of the second fingerprint frames The second fingerprint frame to generate the fingerprint image. The fingerprint identification method as described in item 11 of the patent application scope, wherein the step of determining whether the image blocks of the fingerprint image satisfy the image change condition in the time interval to determine whether the finger object belongs to the real finger includes: When it is determined that the average brightness of the image blocks of the fingerprint image has a ripple change, the processor determines that the fingerprint image satisfies the image change condition. According to the fingerprint identification method described in Item 11 of the patent application range, the image blocks are sequentially arranged from an image center of the fingerprint image outwards. The fingerprint identification method as described in item 11 of the patent application range, wherein a first pixel amount of the first fingerprint frame is higher than a plurality of second pixel amounts of the second fingerprint frames. The fingerprint identification method as described in item 11 of the patent application scope, further includes: selecting the ones according to at least one of an exposure parameter, a gain parameter, and a DC offset parameter of the respective second fingerprint frames One of the second fingerprint frames; and obtaining a third fingerprint frame of the finger object used for a fingerprint verification according to the exposure time corresponding to one of the second fingerprint frames. The fingerprint identification method as described in item 16 of the patent application scope further includes: analyzing the fingerprint pattern changes of the plurality of frame blocks in the third fingerprint frame to obtain information about each of the frame blocks Multiple standard deviations of other fingerprint texture changes; and determining whether the standard deviations are each greater than a first predetermined threshold to determine whether the finger object belongs to the real finger. The fingerprint identification method described in item 17 of the patent application scope further includes: determining whether the sum of the standard deviations of the frame blocks is greater than a second predetermined threshold to determine whether the finger object belongs to the real finger .

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