Biometric image acquisition method and electronic device

Abstract

The present application provides a method for collecting biometric images and an electronic device, the method comprising collecting a first biometric image in a screen-on state; obtaining a collected background image and a noise biometric image in a screen-off state; removing the background image and the noise biometric image from the first biometric image to obtain a second biometric image. The technical solution provided in the above embodiment of the present application can reduce noise on the first biometric image and improve the clarity of the biometric image.

Description

Technical Field

[0001] The present application relates to the field of image acquisition technology, and in particular to a method for acquiring a biometric image and an electronic device. Background Art

[0002] When using the under-screen optical fingerprint sensor, a shading image is usually saved in advance. During use, the pre-saved shading image is used to reduce the noise of the fingerprint image collected in real time.

[0003] The pre-saved background is the screen off / screen on image extracted by the sensor without pressing the finger after the screen and sensor module are assembled.

[0004] This pre-saved shading cannot accurately fit the actual shading when the finger is pressed. It is also impossible to predict the new shading introduced by environmental changes. Therefore, using this shading for denoising may result in unclean image denoising. Summary of the invention

[0005] The embodiment of the present application provides a method for collecting biometric images to reduce noise and obtain clearer images.

[0006] The present application embodiment provides a method for collecting a biometric image, including:

[0007] Collecting a first biometric image in a light-screen state;

[0008] Obtaining the captured background image and the captured noise biometric image in the screen-off state;

[0009] The background image and the noise biometric image are removed from the first biometric image to obtain a second biometric image.

[0010] In one embodiment, before acquiring the captured background image and the captured noise biometric image in the screen-off state, the method further includes:

[0011] Collect background images when the screen is on and off.

[0012] In one embodiment, collecting the first biometric image in the screen-on state includes:

[0013] By lighting up point light sources at different positions, point light source biometric images corresponding to the point light sources at different positions are collected;

[0014] The first biometric characteristic image includes a point light source biometric characteristic image when point light sources at different positions are lit.

[0015] In one embodiment, before acquiring the captured background image and the captured noise biometric image in the screen-off state, the method further includes:

[0016] Capture noisy biometric images with the screen off.

[0017] In one embodiment, the collecting of the noise biometric image in the screen-off state includes:

[0018] Collect regional biometric images corresponding to point light sources at different positions in the screen-off state;

[0019] The noise biometric image includes regional biometric images corresponding to point light sources at different positions in the screen-off state.

[0020] In one embodiment, removing the shading image and the noise biometric image from the first biometric image to obtain the second biometric image includes:

[0021] For point light sources at different positions, remove the background image and the regional biometric image of the area corresponding to the point light source from the point light source biometric image corresponding to the point light source to obtain a unit biometric image corresponding to the point light source;

[0022] The unit biometric characteristic images corresponding to the point light sources at different positions are spliced ​​to obtain the second biometric characteristic image.

[0023] In one embodiment, removing the background image and the regional biometric image of the area corresponding to the point light source from the point light source biometric image corresponding to the point light source includes:

[0024] For each pixel of the point light source biometric image, the grayscale value of the pixel in the point light source biometric image is subtracted from the grayscale value of the pixel in the background image and the grayscale value of the pixel in the regional biometric image.

[0025] The present application also provides an electronic device, the electronic device comprising:

[0026] A screen, configured to emit light to illuminate a target object contacting the screen;

[0027] A sensor module is used to receive the light signal emitted by the screen and reflected by the target object, and convert the light signal into a grayscale value to obtain a first biometric image in a bright screen state;

[0028] The processor is connected to the sensor module and is used to obtain the collected background image and the noise biometric image collected in the screen-off state; and remove the background image and the noise biometric image from the first biometric image to obtain a second biometric image.

[0029] In one embodiment, the screen includes a cover plate and a point light source located below the cover plate.

[0030] In one embodiment, the screen is any one of an OLED panel, a LED panel and an LCD panel.

[0031] The technical solution provided by the above-mentioned embodiments of the present application can obtain a second biometric image with further noise reduction by collecting a background image and a noisy biometric image in a screen-off state in advance, removing the background image and the noisy biometric image from the first biometric image, thereby improving the clarity of the biometric image. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solution of the embodiments of the present application, the drawings required for use in the embodiments of the present application are briefly introduced below.

[0033] Figure 1 is a schematic diagram of the structure of an electronic device provided in an embodiment of the present application;

[0034] Figure 2 It is a flowchart of a method for collecting biometric images provided in an embodiment of the present application;

[0035] Figure 3 is a flowchart of a method for collecting biometric images provided in another embodiment of the present application;

[0036] Figure 4 It is a schematic diagram of the fingerprint image collection process provided in the embodiment of the present application. DETAILED DESCRIPTION

[0037] The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application.

[0038] Similar reference numerals and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings. At the same time, in the description of this application, the terms "first", "second", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0039] Figure 1It is a structural schematic diagram of the electronic device provided in the embodiment of the present application. The electronic device 100 can be a fingerprint identifier, a fingerprint access control, a fingerprint attendance machine, a smart phone, and a tablet computer. The electronic device 100 can be used to execute the biometric image acquisition method provided in the embodiment of the present application, to acquire a first biometric image in the bright screen state; to obtain the acquired background image and the acquired noise biometric image in the off screen state; to remove the background image and the noise biometric image from the first biometric image to obtain a second biometric image. The second biometric image can be considered as a biometric image after noise reduction. The biometric image can be a fingerprint image or a palm print image.

[0040] like Figure 1 As shown, the electronic device 100 includes: a screen 101, a sensor module 102 and a processor 103. The screen 101 is used to emit light to illuminate a target object that contacts the screen 101. The target object may be a finger or a palm. The sensor module 102 may include a photoelectric sensor, a charge amplifier and an analog-to-digital converter that are connected in sequence. The sensor module 102 is used to receive a light signal emitted by the screen and reflected by the target object, and convert the light signal into a grayscale value to obtain a first biometric image in the bright screen state.

[0041] The processor 103 is connected to the sensor module 102, and can receive the first biometric image, and obtain the collected background image and the noise biometric image collected in the screen-off state; remove the background image and the noise biometric image from the first biometric image to obtain the second biometric image.

[0042] The processor 103 can be a gateway, a smart terminal, or a device including a central processing unit (CPU), a graphics processing unit (GPU), or other forms of processing units with data processing capabilities and / or instruction execution capabilities. It can process data of other components in the electronic device 100 and control other components in the electronic device 100 to perform desired functions.

[0043] In one embodiment, the screen 101 may include a cover plate and a point light source located below the cover plate. The number of the point light sources may be multiple.

[0044] In one embodiment, the screen 101 may also be any one of an OLED (Organic Light-Emitting Diode) panel, an LED (Light Emitting Diode) panel and an LCD (Liquid Crystal Display) panel.

[0045] Figure 2FIG. 1 is a flow chart of a method for collecting biometric images provided in an embodiment of the present application. Figure 2 As shown, the method includes the following steps S310-S330.

[0046] Step S310: Capture a first biometric feature image in a light-screen state.

[0047] Among them, the screen-on state and the screen-off state refer to the screen emitting light and not emitting light, respectively. In the screen-on state, the light emitted by the screen can illuminate the fingers or palms touching the screen. The first biometric image refers to a biometric image with noise, and the second biometric image refers to a biometric image after the noise is removed from the first biometric image. To distinguish them, they are respectively referred to as the first biometric image and the second biometric image. The biometric image can be a fingerprint image or a palm print image. The embodiment of the present application takes the fingerprint image as an example for explanation, and the collection of the palm print image can refer to the collection process of the fingerprint image.

[0048] Step S320: Acquire the captured background image and the noise biometric image captured in the screen-off state.

[0049] Among them, the background image refers to the image collected when the screen is on or off when there is no finger or palm pressing. The noise biometric image refers to the fingerprint or palm print image collected when the screen is off due to ambient light. The background image can be collected in advance and stored locally. It is necessary to collect the background image in the screen on and off state in advance, and collect the background image in the screen on and off state without fingerprint pressing. The background image can be collected before S310.

[0050] The noise biometric image may be collected before or after the first biometric image is collected. If the noise biometric image is collected before S310, the first biometric image is collected immediately after the noise biometric image is collected at S310; or the noise biometric image may be collected immediately after S310.

[0051] Step S330: removing the background image and the noise biometric image from the first biometric image to obtain a second biometric image.

[0052] The shading image includes a bright screen shading and an off screen shading, and the bright screen shading and the off screen shading are removed from the first biometric image. Specifically, for each pixel in the first biometric image, the grayscale value of the pixel in the shading image (bright screen shading and off screen shading) can be subtracted from the grayscale value of the pixel in the first biometric image, and then the grayscale value of the pixel in the noise biometric image can be subtracted, and the result is used as the grayscale value of the pixel in the second biometric image.

[0053] For example, assuming that the grayscale value of a certain pixel point P in the first biometric image is M, the grayscale value of this pixel point P in the background image is N, and the grayscale value of this pixel point P in the noise biometric image is L, then the result of M-aN-bL (a, b are magnification coefficients) can be used as the grayscale value of pixel point A in the second biometric image. Similarly, other pixels can also be de-noised in the same way to obtain a second biometric image.

[0054] The technical solution provided by the above-mentioned embodiments of the present application can obtain a second biometric image with further noise reduction by collecting a background image and a noisy biometric image in a screen-off state in advance, removing the background image and the noisy biometric image from the first biometric image, thereby improving the clarity of the biometric image.

[0055] In one embodiment, the above step S310: collecting the first biometric characteristic image in the light-screen state includes: collecting point light source biometric characteristic images corresponding to the point light sources at different positions by lighting the point light sources at different positions. The first biometric characteristic image includes the point light source biometric characteristic images when the point light sources at different positions are lit.

[0056] Among them, a point light source illuminates a certain area, and the point light source biometric image refers to the biometric image collected in the area illuminated by the point light source. The screen may include multiple point light sources, one point light source corresponds to a point light source biometric image, and the splicing of multiple biometric images corresponding to multiple point light sources is the first biometric image. For example, lighting a point light source can only obtain a partial fingerprint image due to the small illumination area, so lighting point light sources at different positions can obtain a complete fingerprint image.

[0057] Taking three point light sources as an example, light up the first point light source alone, collect the point light source biometric image X corresponding to the first point light source, light up the second point light source alone, collect the point light source biometric image Y corresponding to the second point light source, light up the third point light source alone, collect the point light source biometric image Z corresponding to the third point light source, then X, Y, and Z together constitute the first biometric image.

[0058] In one embodiment, collecting a noise biometric image in a screen-off state includes: collecting regional biometric images corresponding to point light sources at different positions in the screen-off state.

[0059] Among them, the screen-off state means that all point light sources are not emitting light. The regional biometric image refers to the area illuminated by a point light source when it is on. When the point light source is off, the biometric image collected in this area is illuminated by the ambient light. Therefore, one point light source corresponds to one regional biometric image. The noise biometric image includes the regional biometric images corresponding to point light sources at different positions in the screen-off state.

[0060] Taking three point light sources as an example, when the screen is off, due to the presence of ambient light, the area corresponding to the first point light source is collected to obtain the regional biometric image x1, the area corresponding to the second point light source is collected to obtain the regional biometric image y1, and the area corresponding to the second point light source is collected to obtain the regional biometric image z1. Then x1, y1, and z1 are spliced ​​together to form a noise biometric image.

[0061] Based on the above embodiments, Figure 3 As shown, the above step S330 specifically includes the following steps S321-S322.

[0062] Step S321: for point light sources at different positions, remove the background image and the regional biometric image of the area corresponding to the point light source from the point light source biometric image corresponding to the point light source to obtain a unit biometric image corresponding to the point light source.

[0063] The unit biometric image refers to an image obtained by removing the background image and the regional biometric image from the point light source biometric image.

[0064] Taking three point light sources as an example, according to the areas illuminated by the point light sources at different positions, the background image can also be divided into three blocks, block 1 corresponding to the first point light source, block 2 corresponding to the second point light source, and block 3 corresponding to the third point light source.

[0065] On the basis of the above embodiment, the first point light source corresponds to the point light source biometric image X and the regional biometric image x1, so the unit biometric image A corresponding to the first point light source is the image obtained by removing the regional biometric image x1 and the block 1 in the background image from the point light source biometric image X. Therefore, the unit biometric image B corresponding to the second point light source is the image obtained by removing the regional biometric image y1 and the block 2 in the background image from the point light source biometric image Y. The unit biometric image C corresponding to the third point light source is the image obtained by removing the regional biometric image z1 and the block 3 in the background image from the point light source biometric image Z.

[0066] In one embodiment, the background image and the regional biometric image of the area corresponding to the point light source are removed from the point light source biometric image corresponding to the point light source. Specifically, the grayscale value of the pixel in the point light source biometric image is subtracted from the grayscale value of the pixel in the background image and the grayscale value of the pixel in the regional biometric image for each pixel point in the point light source biometric image.

[0067] For example, assume that the unit biometric image A is an image obtained by removing the regional biometric image x1 and the block 1 in the background image from the point light source biometric image X. There is a pixel P in the point light source biometric image X with a grayscale value of 200, the grayscale value of the pixel P in the regional biometric image x1 is 50, and the grayscale value of the pixel P in the background image is 20. Then the final grayscale value of the pixel P in the unit biometric image A can be 200-a50-b20 (a, b are magnification coefficients). By calculating the grayscale value of each pixel in turn, the unit biometric image can be obtained.

[0068] Step S322: splicing the unit biometric characteristic images corresponding to the point light sources at different positions to obtain the second biometric characteristic image.

[0069] Taking three point light sources as an example, the first point light source corresponds to unit biometric image A, the second point light source corresponds to unit biometric image B, and the third point light source corresponds to unit biometric image C. The three unit biometric images corresponding to the three point light sources are spliced ​​according to the positions of the point light sources to obtain a complete fingerprint or palm print image, which is called the second biometric image for distinction. Since each unit biometric image has been subjected to noise reduction processing, the spliced ​​second biometric image has higher clarity.

[0070] Figure 4 FIG. 1 is a schematic diagram of a detailed fingerprint image acquisition process provided by an embodiment of the present application. Figure 4 As shown, the following steps are included.

[0071] Step 401, pre-processing stage: the screen and the fingerprint sensor are attached to collect the background image M0;

[0072] Step 402, acquisition phase: acquire the off-screen fingerprint image M1, the first point light source image IMG1, and the second point light source image IMG2. Among them, M1 can be acquired before IMG1, or after IMG1, or after IMG2;

[0073] Step 403, background texture and denoising stage: the image after background texture and denoising is:

[0074] IMG_N1=IMG1–k1*M0'–k2*M1'

[0075] IMG_N2=IMG2–k1*M0”–k2*M1”

[0076] Among them, IMG_N1 is the image of the first point light source image IMG1 after removing the background and denoising, and IMG_N2 is the image of the second point light source image IMG2 after removing the background and denoising. k1, k2 are magnification coefficients, M0' is the area in the background image M0 corresponding to the first point light source image IMG1, and M0" is the area in the background image M0 corresponding to the second point light source image IMG1. M1' is the area in the off-screen fingerprint image M1 corresponding to the first point light source image IMG1; M1" is the area in the off-screen fingerprint image M1 corresponding to the second point light source image IMG2.

[0077] Step 404, IMG_N2 and IMG_N1 are spliced ​​to obtain the final fingerprint image. Adding the collection of the fingerprint image with the screen turned off can be used for noise reduction optimization of the fingerprint image, which can effectively eliminate the noise introduced by environmental changes. This method has less noise and stronger environmental adaptability.

[0078] In several embodiments provided in the present application, the disclosed devices and methods may also be implemented in other ways. The device embodiments described above are merely schematic, for example, the flowcharts and block diagrams in the accompanying drawings show the possible architecture, functions and operations of the devices, methods and computer program products according to the multiple embodiments of the present application. In this regard, each box in the flowchart or block diagram may represent a module, a program segment or a part of a code, and a module, a program segment or a part of a code contains one or more executable instructions for implementing a specified logical function. In some alternative implementations, the functions marked in the box may also occur in an order different from that marked in the accompanying drawings. For example, two consecutive boxes can actually be executed substantially in parallel, and they may sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each box in the block diagram and / or the flowchart, and the combination of boxes in the block diagram and / or the flowchart, can be implemented with a dedicated hardware-based system that performs a specified function or action, or can be implemented with a combination of dedicated hardware and computer instructions.

[0079] In addition, the functional modules in the various embodiments of the present application may be integrated together to form an independent part, or each module may exist separately, or two or more modules may be integrated to form an independent part.

[0080] If the function is implemented in the form of a software function module and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product, which is stored in a storage medium and includes several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the various embodiments of the present application. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, and other media that can store program codes.

Claims

1. A method for collecting biometric images, characterized in that: include: Collecting a first biometric image in a light-screen state; Obtaining the captured background image and the captured noise biometric image in the screen-off state; removing the shading image and the noise biometric image from the first biometric image to obtain a second biometric image; The collecting of the first biometric feature image in the screen-on state includes: By lighting up point light sources at different positions, point light source biometric images corresponding to the point light sources at different positions are collected; Wherein, the first biometric characteristic image includes a point light source biometric characteristic image when point light sources at different positions are lit; Before acquiring the captured background image and the captured noise biometric image in the screen-off state, the method further includes: Collect regional biometric images corresponding to point light sources at different positions in the screen-off state; Wherein, the noise biometric image includes regional biometric images corresponding to point light sources at different positions in the screen-off state; The removing the shading image and the noise biometric image from the first biometric image to obtain a second biometric image includes: For point light sources at different positions, remove the background image and the regional biometric image of the area corresponding to the point light source from the point light source biometric image corresponding to the point light source to obtain a unit biometric image corresponding to the point light source; The unit biometric characteristic images corresponding to the point light sources at different positions are spliced ​​to obtain the second biometric characteristic image.

2. The method according to claim 1, characterized in that Before acquiring the captured background image and the captured noise biometric image in the screen-off state, the method further includes: Collect background images when the screen is on and off.

3. The method according to claim 1, characterized in that The removing of the shading image and the regional biometric image of the area corresponding to the point light source from the point light source biometric image corresponding to the point light source comprises: For each pixel of the point light source biometric image, the grayscale value of the pixel in the point light source biometric image is subtracted from the grayscale value of the pixel in the background image and the grayscale value of the pixel in the regional biometric image.

4. An electronic device, characterized in that: The electronic device comprises: A screen, used to emit light to illuminate a target object contacting the screen, the screen comprising a cover plate and a point light source located below the cover plate; A sensor module is used to receive the light signal emitted by the screen and reflected by the target object, and convert the light signal into a grayscale value to obtain a first biometric image in a bright screen state; A processor connected to the sensor module, configured to obtain a captured background image and a noise biometric image captured in a screen-off state; and remove the background image and the noise biometric image from the first biometric image to obtain a second biometric image; The obtaining of the first biometric feature image in the light-screen state comprises: By lighting up point light sources at different positions, point light source biometric images corresponding to the point light sources at different positions are collected; Wherein, the first biometric characteristic image includes a point light source biometric characteristic image when point light sources at different positions are lit; Before acquiring the captured background image and the noise biometric image captured in the screen-off state, the processor is further configured to: Collect regional biometric images corresponding to point light sources at different positions in the screen-off state; Wherein, the noise biometric image includes regional biometric images corresponding to point light sources at different positions in the screen-off state; The removing the shading image and the noise biometric image from the first biometric image to obtain a second biometric image includes: For point light sources at different positions, remove the background image and the regional biometric image of the area corresponding to the point light source from the point light source biometric image corresponding to the point light source to obtain a unit biometric image corresponding to the point light source; The unit biometric characteristic images corresponding to the point light sources at different positions are spliced ​​to obtain the second biometric characteristic image.

5. The electronic device according to claim 4, characterized in that: The screen is any one of an OLED panel, a LED panel and an LCD panel.

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