Terminal device and full-screen fingerprint recognition method

Abstract

A terminal device and a full-screen fingerprint recognition method are provided to realize fingerprint recognition at any position of the screen. The terminal device includes: a screen, a plurality of ultrasonic transducers and a processor, wherein the plurality of ultrasonic transducers are respectively coupled to the edge of the lower surface of the cover plate of the screen, and the plurality of ultrasonic transducers are also respectively coupled to the processor. The ultrasonic transducer is used to generate a first surface acoustic wave under the control of the processor; and, under the control of the processor, receive a second surface wave and output an electrical signal corresponding to the second surface acoustic wave to the processor, wherein the second surface acoustic wave is generated after the first surface acoustic wave propagates from the lower surface of the cover plate to the upper surface of the cover plate and is scattered by a finger pressing on the upper surface of the cover plate of the screen; the processor is used to generate a fingerprint image according to the electrical signal corresponding to the second surface acoustic wave.

Description

Technical Field

[0001] The present application relates to the field of sensor technology, and in particular to a terminal device and a full-screen fingerprint recognition method. Background Art

[0002] With the continuous development of electronic information technology, terminal devices such as smart phones and tablet computers have become essential tools for people's work and life. Since fingerprints have lifelong validity, uniqueness and convenience, terminal devices usually verify the user's identity information by fingerprint recognition, thereby ensuring the security of the information stored in the terminal device.

[0003] At present, the fingerprint recognition module in the terminal device is generally set in the non-display area of ​​the terminal device, such as the home button of the terminal device. The recognition area is narrow and requires additional space, which will inevitably limit the screen-to-body ratio of the terminal device and is not conducive to the realization of full-screen terminal devices. Therefore, it is urgent to propose an effective full-screen fingerprint recognition solution to realize fingerprint recognition at any position of the screen without affecting the screen-to-body ratio. Summary of the invention

[0004] The present application provides a terminal device and a full-screen fingerprint recognition method to realize fingerprint recognition at any position of the screen.

[0005] In a first aspect, the present application provides a terminal device, comprising: a screen, a plurality of ultrasonic transducers and a processor, wherein the plurality of ultrasonic transducers are respectively coupled to the edges of the lower surface of the cover plate of the screen, and the plurality of ultrasonic transducers are also respectively coupled to the processor, and the surface corresponding to the connection between the lower surface of the cover plate of the screen and the side surface of the cover plate is a first curved surface, and the surface corresponding to the connection between the upper surface of the cover plate and the side surface of the cover plate is a second curved surface.

[0006] The ultrasonic transducer is used to generate a first surface acoustic wave under the control of the processor, and the first surface acoustic wave propagates from the lower surface of the cover plate to the upper surface of the cover plate through the first curved surface and the second curved surface. The ultrasonic transducer is also used to receive a second surface wave under the control of the processor, and output an electrical signal corresponding to the second surface acoustic wave to the processor, wherein the second surface acoustic wave is generated after the first surface acoustic wave is scattered by a finger pressing on the upper surface of the cover plate of the screen, and the second surface acoustic wave propagates from the upper surface of the cover plate to the lower surface of the cover plate through the second curved surface and the first curved surface.

[0007] The processor is used to control part or all of the multiple ultrasonic transducers to generate the first surface acoustic wave when it is determined that fingerprint recognition is required; and control part or all of the multiple ultrasonic transducers to receive the second surface acoustic wave, and generate a fingerprint image according to the electrical signal corresponding to the second surface acoustic wave.

[0008] Through the above scheme, when the processor in the terminal device determines that fingerprint identification is required, it controls the ultrasonic transducer distributed at the edge of the lower surface of the cover plate of the terminal device screen to generate a surface acoustic wave that can cover the upper surface of the cover plate, and uses the ultrasonic transducer to receive the surface acoustic wave scattered by the fingerprint on the finger at any position on the upper surface of the cover plate to generate a fingerprint image, and then the fingerprint image can be used for fingerprint identification. Since the wavelength of the surface acoustic wave generated by the ultrasonic transducer on the cover plate surface of the screen is short, the spatial resolution of the fingerprint image generated by the processor can be improved (including the lateral (direction perpendicular to the propagation direction of the surface acoustic wave) resolution and the longitudinal (direction parallel to the propagation direction of the surface acoustic wave) resolution), and the surface acoustic wave attenuation is small, which is conducive to expanding the fingerprint detection range of the terminal device. In addition, since the dispersion of the surface acoustic wave is small, the longitudinal resolution of the fingerprint image generated by the processor can be further improved.

[0009] Moreover, compared with the existing fingerprint recognition solutions based on ultrasonic body waves, this solution has low manufacturing tolerance requirements for the first curved surface and the second curved surface used to transmit surface acoustic waves between the upper and lower surfaces of the screen cover in the terminal device, and the feasibility of mass production of the terminal device is relatively high.

[0010] Further, the first surface acoustic wave propagates along the lower surface of the cover plate of the screen to the first curved surface, propagates through the first curved surface to the side of the cover plate of the screen (the first surface acoustic wave makes a first turn), propagates along the side of the cover plate of the screen to the second curved surface, propagates through the second curved surface to the upper surface of the cover plate of the screen (the first surface acoustic wave makes a second turn). When the first surface acoustic wave encounters a finger pressed on the upper surface of the cover plate of the screen during propagation on the upper surface of the cover plate of the screen, the second surface acoustic wave is scattered by the ridges of the fingerprint on the finger surface, and the second surface acoustic wave propagates along the upper surface of the cover plate of the screen to the second curved surface, propagates through the second curved surface to the side of the cover plate of the screen (the second surface acoustic wave makes a first turn), propagates along the side of the cover plate of the screen to the first curved surface, propagates through the first curved surface to the lower surface of the cover plate of the screen (the second surface acoustic wave makes a second turn), and is received by the ultrasonic transducer arranged on the lower surface of the cover plate of the screen.

[0011] In one possible embodiment, multiple ultrasonic transducers can be linearly arrayed on the edge of any side of the lower surface of the cover plate of the screen, or linearly arrayed on the edges of any two orthogonal sides of the lower surface of the cover plate of the screen, or linearly arrayed on the edges of any two parallel sides of the lower surface of the cover plate of the screen, or linearly arrayed on the edges of all sides of the lower surface of the cover plate of the screen.

[0012] In one possible implementation, when the processor generates a fingerprint image based on the electrical signal corresponding to the second surface acoustic wave, it can specifically use an ultrasonic imaging algorithm such as a beamforming algorithm (such as a total focusing algorithm TFM or a synthetic aperture focusing SAFT algorithm, etc.), a tomography algorithm (such as a diffraction tomography DT algorithm), or a super-resolution imaging algorithm (such as a time reversal multi-signal classification TR-MUSIC algorithm) to generate the fingerprint image.

[0013] In one possible implementation, on the propagation path of the first surface acoustic wave, the curvature radius R1 of the first curved surface and the curvature radius R2 of the second curved surface are greater than or equal to the wavelength of the first surface acoustic wave; on the propagation path of the second surface acoustic wave, the curvature radius R1 of the first curved surface and the curvature radius R2 of the second curved surface are greater than or equal to the wavelength of the second surface acoustic wave, wherein the wavelength of the first surface acoustic wave is equal to the wavelength of the second surface acoustic wave, so as to ensure that the first surface acoustic wave can propagate from the lower surface of the cover plate of the screen to the fingerprint pressing point on the upper surface of the cover plate, and that the second surface acoustic wave generated by the scattering of the first surface acoustic wave by the fingerprint is propagated from the upper surface of the cover plate to the lower surface of the cover plate to be received by the ultrasonic transducer without causing large sound field loss and waveform conversion.

[0014] Furthermore, the radius of curvature of the first curved surface may be the same as or different from the radius of curvature of the second curved surface. The first curved surface and the second curved surface may be smooth curved surfaces to reduce the loss of the first surface acoustic wave and the second surface acoustic wave, improve the signal-to-noise ratio of the first surface acoustic wave and the second surface acoustic wave, and thus improve the sensitivity of fingerprint detection.

[0015] In a possible implementation, when the cover of the screen is a glass cover with a thickness of 0.5 mm to 1 mm (at this time, the wavelength λ of the first surface acoustic wave is 0.1 mm to 0.3 mm), the curvature radius of the first curved surface is 0.3 mm to 0.7 mm, and the curvature radius of the second curved surface is 0.3 mm to 0.7 mm.

[0016] In a possible implementation, the ultrasonic transducer may be an oblique-incidence surface acoustic wave transducer, which has the advantages of simple structure, high conversion efficiency and low cost, and thus can reduce the cost of terminal equipment and improve the accuracy of fingerprint detection. The oblique-incidence surface acoustic wave transducer includes a piezoelectric element and a wedge; the piezoelectric element is used to generate longitudinal waves in the wedge, and the wedge is used to convert the longitudinal waves into surface acoustic waves at the interface between the wedge and the cover plate.

[0017] In a possible implementation, when the cross section of the wedge is a right triangle, the incident angle θ of the wedge satisfies the following formula:

[0018] θ≈arcsin(C L1 / C R2 )

[0019] Among them, C L1 is the velocity of longitudinal waves, C R2 is the velocity of the first surface wave.

[0020] In a possible implementation, the ultrasonic transducer may also be an interdigital transducer, which includes a piezoelectric element and interdigital electrodes. The interdigital transducer has a compact structure, which is conducive to miniaturization and integrated design, thereby reducing the size of the terminal device.

[0021] In one possible implementation, the finger width and spacing of the interdigital electrodes in the interdigital transducer are both λ / 4, where λ is the wavelength of the first surface acoustic wave, so that the first surface acoustic wave generated by each interdigital electrode in the interdigital transducer exciting the piezoelectric element is superimposed in phase, thereby increasing the intensity of the first surface acoustic wave generated by the interdigital transducer.

[0022] In a possible implementation, since the cover of the screen is transparent, in order not to affect the normal display and aesthetic appearance of the terminal device, a shielding material is provided on the area on the lower surface of the cover for arranging the multiple ultrasonic transducers, wherein the shielding material is used to shield the multiple ultrasonic transducers coupled on the lower surface of the cover, and the acoustic impedance of the shielding material matches the acoustic impedance of the cover, so as to reduce the influence of the shielding material on the first surface wave generated by the acoustic transducer. The shielding material may be ink.

[0023] In a possible implementation, a plurality of ultrasonic transducers are linearly arrayed at the edge of the lower surface of the cover plate, and the distance between two adjacent ultrasonic transducers is determined according to the resolution of the fingerprint image.

[0024] In one possible implementation, the terminal device further includes a signal processing circuit for generating an excitation signal under the control of a processor, the excitation signal being used to excite some or all of the plurality of ultrasonic transducers to generate a first surface acoustic wave; and amplifying an electrical signal corresponding to the second surface acoustic wave; the processor is further used to: when it is determined that fingerprint recognition is required, control the signal processing circuit to generate an excitation signal; and generate a fingerprint image based on the electrical signal corresponding to the amplified second surface acoustic wave.

[0025] In one possible implementation, in order to further improve the imaging accuracy of the fingerprint image, the processor may preprocess the digital signal obtained by the signal processing circuit before generating the fingerprint image based on the electrical signal corresponding to the second surface acoustic wave, such as filtering and noise reduction, so as to improve the signal-to-noise ratio of the digital signal, thereby improving the imaging accuracy of the fingerprint image.

[0026] In a possible implementation, the processor is further configured to: match the generated fingerprint image with a pre-stored fingerprint image, and process a request for triggering the fingerprint recognition application according to the matching result.

[0027] Further, when the generated fingerprint image successfully matches the pre-stored fingerprint image, the processor responds to the request of the application that triggers fingerprint recognition; when the generated fingerprint image fails to match the pre-stored fingerprint image, the processor rejects the request of the application that triggers fingerprint recognition.

[0028] In the second aspect, the present application provides a full-screen fingerprint recognition method, which is applied to the terminal device described in any possible implementation of the first aspect. The method includes the following steps: when it is determined that fingerprint recognition is required, control some or all of the multiple ultrasonic transducers in the terminal device to generate a first surface acoustic wave, wherein the first surface acoustic wave propagates from the lower surface of the cover plate to the upper surface of the cover plate through the first curved surface and the second curved surface; control some or all of the multiple ultrasonic transducers to receive a second surface acoustic wave, wherein the second surface acoustic wave is generated after the first surface acoustic wave is scattered by the finger pressing the upper surface of the cover plate, and the second surface acoustic wave propagates from the upper surface of the cover plate to the lower surface of the cover plate through the second curved surface and the first curved surface; generate a fingerprint image according to the electrical signal corresponding to the second surface acoustic wave.

[0029] Through the above method, when the terminal device determines that fingerprint recognition is required, it controls the ultrasonic transducer distributed at the edge of the lower surface of the cover plate of the terminal device's screen to generate a surface acoustic wave that can cover the upper surface of the cover plate, and uses the ultrasonic transducer to receive the surface acoustic wave scattered by the fingerprint on the finger at any position on the upper surface of the cover plate to generate a fingerprint image, and then the fingerprint image can be used for fingerprint recognition. Since the wavelength of the surface acoustic wave generated by the ultrasonic transducer on the surface of the screen cover plate is short, the above method can improve the spatial resolution of the fingerprint image, and the surface acoustic wave attenuation is small, which is conducive to expanding the fingerprint detection range of the terminal device. In addition, since the dispersion of the surface acoustic wave is small, the above method can further improve the longitudinal resolution of the fingerprint image.

[0030] Compared with the existing fingerprint recognition solutions based on ultrasonic body waves, this method has low manufacturing tolerance requirements for the first curved surface and the second curved surface in the terminal device for transmitting surface acoustic waves between the upper and lower surfaces of the screen cover, and is more feasible for mass production of terminal devices.

[0031] In one possible implementation, the terminal device can specifically control some or all of the multiple ultrasonic transducers to generate a first surface acoustic wave by the following method: generating an excitation signal, and using the excitation signal to excite some or all of the multiple ultrasonic transducers to generate a first surface acoustic wave.

[0032] In a possible implementation, in order to increase the energy of the first surface acoustic wave and thereby improve the accuracy of fingerprint recognition, after the terminal device generates an excitation signal, before using the excitation signal to excite some or all of the multiple ultrasonic transducers, the excitation signal can be amplified, and the amplified excitation signal can be used to excite some or all of the multiple ultrasonic transducers.

[0033] In one possible implementation, before generating a fingerprint image based on the electrical signal corresponding to the second surface acoustic wave, the terminal device may also preprocess the electrical signal corresponding to the second surface acoustic wave, such as filtering, to improve the signal-to-noise ratio of the electrical signal corresponding to the second surface acoustic wave, thereby improving the accuracy of the fingerprint image.

[0034] In one possible implementation, when the terminal device 100 generates a fingerprint image based on the second surface acoustic wave, it can specifically use an ultrasonic imaging algorithm such as a beamforming algorithm (such as a TFM algorithm or a SAFT algorithm, etc.), a tomography algorithm (such as a DT algorithm), or a super-resolution imaging algorithm (such as a TR-MUSIC algorithm) to generate the fingerprint image.

[0035] In a possible implementation, the terminal device may also match the generated fingerprint image with a pre-stored fingerprint image, and process the request of the application that triggers fingerprint recognition according to the matching result. Furthermore, when the generated fingerprint image successfully matches the pre-stored fingerprint image, the terminal device responds to the request of the application that triggers fingerprint recognition; when the generated fingerprint image fails to match the pre-stored fingerprint image, the terminal device rejects the request of the application that triggers fingerprint recognition. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1a One of the structural schematic diagrams of a terminal device provided in an embodiment of the present application;

[0037] Figure 1b A second structural diagram of a terminal device provided in an embodiment of the present application;

[0038] Figure 2 A schematic structural diagram of an oblique-incidence surface acoustic wave transducer provided in an embodiment of the present application;

[0039] Figure 3 A schematic structural diagram of an oblique-incidence surface acoustic wave transducer array provided in an embodiment of the present application;

[0040] Figure 4 A schematic diagram of the structure of an interdigital transducer provided in an embodiment of the present application;

[0041] Figure 5 A schematic diagram of the propagation of a surface acoustic wave in a cover plate of a screen provided in an embodiment of the present application;

[0042] Figure 6a A schematic diagram of the reflective surface acoustic wave transceiver process provided in an embodiment of the present application;

[0043] Figure 6b A schematic diagram of the transmission surface acoustic wave receiving and transmitting process provided in an embodiment of the present application;

[0044] Figure 7 A third structural diagram of a terminal device provided in an embodiment of the present application;

[0045] Figure 8 A fourth structural diagram of a terminal device provided in an embodiment of the present application;

[0046] Figure 9a A fifth structural diagram of a terminal device provided in an embodiment of the present application;

[0047] Figure 9b A sixth structural diagram of a terminal device provided in an embodiment of the present application;

[0048] Fig.10A seventh structural diagram of a terminal device provided in an embodiment of the present application;

[0049] Fig.11 A schematic diagram of a fingerprint recognition method provided in an embodiment of the present application. DETAILED DESCRIPTION

[0050] With the rise of full-screen phones, full-screen fingerprint recognition has also become a major trend in the development of current terminal devices. At present, full-screen fingerprint recognition technology mainly faces the following technical challenges: 1. Display problem, the fingerprint recognition sensor is integrated with the screen module, and the display function of the screen cannot be affected; 2. Cost problem, the fingerprint detection area is expanded from a fixed area to the entire screen, and the cost of the existing screen module and fingerprint recognition module cannot be increased too much; 3. Penetration problem, the screen has a complex stacking structure, and the fingerprint signal on the screen surface needs to penetrate the screen to be clearly imaged.

[0051] Fingerprint recognition technology mainly includes capacitive fingerprint recognition technology, optical fingerprint recognition technology and ultrasonic fingerprint recognition technology according to different recognition principles. Among them, capacitive fingerprint recognition technology uses the fingerprint recognition sensor and the subcutaneous electrolyte of the finger to form an electric field. The ups and downs of the fingerprint will cause the voltage difference of the electric field to change, thereby realizing fingerprint recognition. However, the electric field attenuation is severe and cannot penetrate the cover glass of the screen of about 700um. At the same time, capacitive fingerprint recognition technology needs to add a transparent electrode detection layer under the cover glass, which will produce moiré fringes and affect the display of the screen, and thus cannot meet the requirements of full-screen fingerprint recognition.

[0052] Optical fingerprint recognition technology mainly uses the principle of light reflection to image the light scattered by the fingerprint on the surface of the finger through the image sensor to obtain the fingerprint image. Therefore, it is necessary to add an optical imaging system and image sensor under the screen, which leads to a significant increase in cost and thickness of the fingerprint recognition module. In addition, optical fingerprint recognition technology usually uses the light emitted by the screen module itself as the light source, and the light divergence angle emitted by the screen module is large. After the light scattered by the fingerprint reaches the optical imaging system, the light energy utilization rate is very low. In addition, the screen has a low light transmittance, making it difficult for the light intensity reaching the image sensor to meet the fingerprint recognition requirements, and thus cannot meet the requirements of full-screen fingerprint recognition.

[0053] Ultrasonic fingerprint recognition technology uses ultrasonic waves of a specific frequency emitted by the fingerprint recognition module to create a fingerprint pattern based on the ultrasonic waves scattered by the fingerprint. Compared with capacitive fingerprint recognition technology and optical fingerprint recognition technology, ultrasonic fingerprint recognition technology has unique advantages such as strong penetration and high accuracy. It can penetrate the glass cover of the screen and is not affected by possible dirt on the fingers, such as sweat or hand cream, providing users with a good fingerprint recognition experience. In summary, ultrasonic fingerprint recognition technology is a highly feasible solution for achieving full-screen fingerprint recognition.

[0054] The ultrasonic waves used in ultrasonic fingerprint recognition technology mainly include ultrasonic body waves and ultrasonic plate waves. When using ultrasonic body waves for fingerprint recognition, it is necessary to reasonably design the structure of the ultrasonic waveguide so that the reflection boundary of the ultrasonic waveguide can control the ultrasonic body wave to cover the entire area for fingerprint recognition. However, this method generally requires extremely high manufacturing tolerances for the ultrasonic waveguide structure and has low feasibility for mass production. Ultrasonic plate waves have very complex multi-modal and dispersion characteristics, and it is necessary to select a suitable mode selection and perform mode control. At present, there are also some solutions in the prior art for in-screen fingerprint recognition by arranging ultrasonic transducers at the edge of the screen, but they cannot excite ultrasonic guided waves with a single mode and good propagation characteristics, resulting in a low signal-to-noise ratio of the ultrasonic scattering signal received by the ultrasonic transducer, which in turn leads to the inability to correctly reconstruct the fingerprint image, or the power consumption and cost of the ultrasonic transducer used are high, and the feasibility of large-scale application in terminal equipment is low. Therefore, the problem that needs to be solved in the full-screen fingerprint recognition solution based on ultrasonic fingerprint recognition technology is: how to select a suitable ultrasonic mode and a corresponding ultrasonic transducer.

[0055] In order to solve the above problems, the present application provides a terminal device and a full-screen fingerprint recognition method, which realizes full-screen fingerprint recognition through ultrasonic fingerprint recognition technology. The method and the terminal device are based on the same concept. Since the principles of solving the problem by the method and the terminal device are similar, the implementation of the method and the terminal device can refer to each other, and the repeated parts will not be repeated.

[0056] In order to realize full-screen fingerprint recognition, the embodiments of the present application mainly improve the fingerprint recognition method of the terminal device, and the terminal device can be a mobile phone, tablet computer, laptop computer or smart watch and other devices with fingerprint recognition function. However, it should be understood that the terminal device provided in the embodiments of the present application is a complete terminal device and also has the structure of the known terminal device. Only the components of the terminal device related to the fingerprint recognition of the terminal device are described here, and other components are not described in detail.

[0057] In addition, it should be understood that, in the description of this application, "plurality" refers to two or more; words such as "first" and "second" are only used for the purpose of distinguishing the description, and cannot be understood as indicating or implying relative importance, nor can they be understood as indicating or implying order.

[0058] like Figure 1a As shown, the present application provides a terminal device 100, which includes: a screen 110, a plurality of ultrasonic transducers 120 and a processor 130. Generally, the screen 110 is divided into three layers from the outside to the inside, namely a cover plate, a touch sensor layer and a display layer, wherein the cover plate is mainly used to protect the touch sensor layer and the display layer on the inner side of the cover plate, and the commonly used cover plate is a glass cover plate; the touch sensor layer is mainly used to detect touch operations, which are mainly divided into resistive and capacitive types; the display layer is used to display images, and common display screens include liquid crystal display (LCD) screens, active-matrix organic light-emitting diode (AMOLED) screens and organic light-emitting diode (OLED) screens.

[0059] In the terminal device 100, multiple ultrasonic transducers 120 are respectively coupled to the edge of the lower surface of the cover plate of the screen 110, and the multiple ultrasonic transducers 120 are also respectively coupled to the processor 130. The surface corresponding to the connection between the lower surface of the cover plate of the screen 110 and the side surface of the cover plate is a first curved surface, and the surface corresponding to the connection between the upper surface of the cover plate and the side surface of the cover plate is a second curved surface. It can be understood that the specific sizes of the first curved surface and the second curved surface can be determined in combination with actual conditions (such as in combination with factors such as appearance and process), and the present application does not limit it. Among them, the upper surface of the cover plate of the screen 110 is the touch surface of the screen 110, and the lower surface of the cover plate of the screen 110 is the reverse side corresponding to the upper surface of the cover plate of the screen 110. The following is in combination with Figure 1a The above components constituting the terminal device 100 are specifically introduced:

[0060] The ultrasonic transducer 120 is used to generate a first surface acoustic wave under the control of the processor 130, the first surface acoustic wave propagates from the lower surface of the cover plate to the upper surface of the cover plate through the first curved surface and the second curved surface; and, under the control of the processor 130, receive a second surface acoustic wave and output an electrical signal corresponding to the second surface acoustic wave, wherein the second surface acoustic wave is generated after the first surface acoustic wave is scattered by the finger pressing on the upper surface of the cover plate of the screen 110, and the second surface acoustic wave propagates from the upper surface of the cover plate to the lower surface of the cover plate through the second curved surface and the first curved surface. The lines formed by the concave and convex skin on the epidermis of the finger pulp are called ridges, and the lines formed by the concave skin are called valleys. That is to say, when the user's finger touches the screen, the ridges in the fingerprint actually touch the screen, so the second surface acoustic wave is generated by the scattering of the first surface acoustic wave by the ridges of the fingerprint on the finger.

[0061] The processor 130 is used to control part or all of the multiple ultrasonic transducers 120 to generate the first surface acoustic wave when it is determined that fingerprint recognition is required; and control part or all of the multiple ultrasonic transducers 120 to receive the second surface acoustic wave, and generate a fingerprint image according to the electrical signal corresponding to the second surface acoustic wave.

[0062] At this time, if Figure 1b As shown, the processor 130 may specifically include a fingerprint control module 131 and a fingerprint imaging module 132, wherein the fingerprint control module 131 is used to control part or all of the multiple ultrasonic transducers 120 to generate the first surface acoustic wave, and control part or all of the multiple ultrasonic transducers 120 to receive the second surface acoustic wave when it is determined that fingerprint recognition is required; the fingerprint imaging module 132 is used to generate a fingerprint image according to the electrical signal corresponding to the second surface acoustic wave. The fingerprint control module 131 and the fingerprint imaging module 132 can be implemented by software, that is, the processor 130 can implement the functions of the fingerprint control module 131 and the fingerprint imaging module 132 by calling the code instructions stored in the memory (not shown in the figure) in the terminal device 100.

[0063] The first surface acoustic wave propagates along the lower surface of the cover plate of the screen 110 to the first curved surface, propagates through the first curved surface to the side of the cover plate of the screen 110 (the first surface acoustic wave makes a first turn), propagates along the side of the cover plate of the screen 110 to the second curved surface, propagates through the second curved surface to the upper surface of the cover plate of the screen 110 (the first surface acoustic wave makes a second turn). When the first surface acoustic wave encounters a finger pressed on the upper surface of the cover plate of the screen 110 during propagation on the upper surface of the cover plate of the screen 110, the second surface acoustic wave is scattered by the ridges of the fingerprint on the finger surface, and the second surface acoustic wave propagates along the upper surface of the cover plate of the screen 110 to the second curved surface, propagates through the second curved surface to the side of the cover plate of the screen 110 (the second surface acoustic wave makes a first turn), propagates along the side of the cover plate of the screen 110 to the first curved surface, propagates through the first curved surface to the lower surface of the cover plate of the screen 110 (the second surface acoustic wave makes a second turn), and is received by the ultrasonic transducer arranged on the lower surface of the cover plate of the screen 110.

[0064] It should be noted that the first curved surface, the side surface of the cover plate, and the second curved surface can actually be a whole; or, the first curved surface and the lower surface of the cover plate are a whole, and the second curved surface and the upper surface of the cover plate are a whole; or, the lower surface of the cover plate, the first curved surface, and the side surface are a whole. The embodiments of the present application do not strictly distinguish their specific positions, and those skilled in the art can design them according to actual conditions. In addition, the present application does not limit the shape of the side surface of the cover plate of the screen 110, and the side surface of the cover plate can be a curved surface or a flat surface.

[0065] When the processor 130 generates a fingerprint image according to the electrical signal corresponding to the second surface acoustic wave, it can specifically use an ultrasonic imaging algorithm such as a beamforming algorithm (such as a total focusing method (TFM) or a synthetic aperture focusing technique (SAFT) algorithm, etc.), a tomography algorithm (such as a diffraction tomography (DT) algorithm), or a super-resolution imaging algorithm (such as a time-reversal multiple signal classification (TR-MUSIC) algorithm) to generate the fingerprint image.

[0066] The multiple ultrasonic transducers 120 in the terminal device 100 can be linearly arrayed at the edge of the lower surface of the cover plate of the screen 110. The distance between two adjacent ultrasonic transducers 120 is determined according to the resolution of the fingerprint image generated by the processor 130. The smaller the distance between two adjacent ultrasonic transducers 120, the higher the resolution of the fingerprint image. In a specific implementation, the distance between two adjacent ultrasonic transducers 120 in the linear array composed of multiple ultrasonic transducers 120 can be 0.2-0.5 mm. At this time, the number of ultrasonic transducers 120 is determined according to the size of the cover plate and the distance between two adjacent ultrasonic transducers 120.

[0067] Specifically, a plurality of ultrasonic transducers 120 may be linearly arrayed at the edge of any side of the lower surface of the cover plate of the screen 110, or linearly arrayed at the edges of any two orthogonal sides of the lower surface of the cover plate of the screen 110, or linearly arrayed at the edges of any two parallel sides of the lower surface of the cover plate of the screen 110, or linearly arrayed at the edges of all sides of the lower surface of the cover plate of the screen 110. In order to ensure the aesthetics of the screen 110, the ultrasonic transducer 120 is arranged as close as possible to the edge of the lower surface of the cover plate of the screen 110. The width of the lower surface edge of the cover plate of the screen 110 occupied by the ultrasonic transducer 120 is usually no more than 3 mm.

[0068] It should be noted that the embodiment of the present application does not limit the array method of multiple ultrasonic transducers 120 on the lower surface of the cover plate of the screen 110. The above-mentioned array method of multiple ultrasonic transducers 120 is only for illustration and does not constitute a limitation on the present application. Any array method that can realize full-screen fingerprint ultrasonic detection is applicable to the present application.

[0069] In one possible implementation, Figure 2As shown, the ultrasonic transducer 120 may be an oblique-incidence surface acoustic wave transducer, which has the advantages of simple structure, high conversion efficiency and low cost. Specifically, the oblique-incidence surface acoustic wave transducer includes a piezoelectric element and a wedge, wherein the piezoelectric element is used to generate longitudinal waves in the wedge, and the wedge is used to convert the longitudinal waves generated by the piezoelectric element into surface acoustic waves at the interface between the wedge and the cover plate of the screen 110. The material of the piezoelectric element may be lithium niobate, lead zirconate titanate, aluminum nitride or polyvinylidene fluoride (PVDF), etc., and the material of the wedge may be polymethyl methacrylate (PMMA), acrylonitrile butadiene styrene (ABS) plastic, synthetic foam plastic, polystyrene, polysulfone or epoxy resin, etc. Piezoelectric elements can be manufactured using traditional piezoelectric ceramic technology or piezoelectric micro-electro-mechanical system (MEMS) technology. The piezoelectric ceramic technology uses sintering, scribing and other processes. The electrodes of the piezoelectric elements are silver or gold, and a sintering or sputtering process is used. The piezoelectric MEMS process can use a gel sol process or a sputtering process.

[0070] Wherein, in the scenario where the cross section of the wedge is a right triangle, the incident angle θ of the wedge satisfies the following formula:

[0071] θ≈arcsin(C L1 / C R2 )

[0072] C L1 is the velocity of the longitudinal wave generated by the piezoelectric element, C R2 is the velocity of the first surface wave. The incident angle θ of the wedge and the length l of the piezoelectric element are determined trx Later, the right-angle side l of the wedge can be determined by the following formula ra The length of the hypotenuse l hpt Length and height h of the wedge:

[0073]

[0074] l hpt = l trx tanθ

[0075] h=l trx sinθ

[0076] An array of multiple oblique-incidence surface acoustic wave transducers can be formed by multiple piezoelectric element arrays on a larger wedge, such as Figure 3As shown, it can also be composed of multiple oblique-incidence surface acoustic wave transducers consisting of a single piezoelectric element and a single wedge.

[0077] In another possible implementation, Figure 4 As shown, the ultrasonic transducer 120 can be an interdigital transducer, which includes a piezoelectric element and an interdigital electrode. The interdigital transducer has a compact structure, which is conducive to miniaturization and integrated design, thereby reducing the size of the terminal device. Among them, the finger width and spacing of the interdigital electrodes of the interdigital transducer are both λ / 4, λ is the wavelength of the first surface acoustic wave, so that each interdigital electrode in the interdigital transducer excites the piezoelectric element to generate a first surface acoustic wave that is superimposed in phase, thereby increasing the intensity of the first surface acoustic wave generated by the interdigital transducer. In a specific implementation, the length of the interdigital transducer can be 0.2 to 2 mm, the width can be 0.1 to 1 mm, and the thickness can be 0.05 to 0.5 mm. The material of the piezoelectric element in the interdigital transducer can be lithium niobate or lead zirconate titanate, etc.

[0078] Since the cover of the screen 110 is transparent, in order not to affect the normal display and aesthetic appearance of the terminal device 100, a shielding material is provided on the area of ​​the lower surface of the cover of the screen 110 where the multiple ultrasonic transducers 120 are provided, wherein the shielding material is used to shield the multiple ultrasonic transducers 120, and the acoustic impedance of the shielding material matches the acoustic impedance of the cover to reduce the influence of the shielding material on the first surface wave generated by the acoustic transducer 120. The shielding material may be ink.

[0079] In a specific implementation, on the propagation path of the first surface acoustic wave, the curvature radius R1 of the first curved surface and the curvature radius R2 of the second curved surface are greater than or equal to the wavelength of the first surface acoustic wave; on the propagation path of the second surface acoustic wave, the curvature radius R1 of the first curved surface and the curvature radius R2 of the second curved surface are greater than or equal to the wavelength of the second surface acoustic wave, wherein the wavelength of the first surface acoustic wave is equal to the wavelength of the second surface acoustic wave, so as to ensure that the first surface acoustic wave can be propagated from the lower surface of the cover plate of the screen 110 to the fingerprint pressing position on the upper surface of the cover plate, and the second surface acoustic wave generated by the scattering of the first surface acoustic wave by the fingerprint is propagated from the upper surface of the cover plate to the lower surface of the cover plate and received by the ultrasonic transducer 120, without causing large sound field loss and wave type conversion. The curvature radius of the first curved surface can be the same as or different from the curvature radius of the second curved surface. The first curved surface and the second curved surface can be smooth surfaces to reduce the loss of the first surface acoustic wave and the second surface acoustic wave, improve the signal-to-noise ratio of the first surface acoustic wave and the second surface acoustic wave, and further improve the sensitivity of fingerprint detection.

[0080] For example, Figure 5As shown, when multiple ultrasonic transducers 120 adopt a reflective transceiver mode, since multiple ultrasonic transducers 120 are arranged on the lower surface of the cover plate of the screen 110, the first surface acoustic wave can propagate along the lower surface of the cover plate to the first curved surface like the left side, the curvature radius R1 of the first curved surface is greater than or equal to the wavelength of the first surface acoustic wave, and after passing through the first curved surface, the first surface acoustic wave propagates upward along the side of the cover plate, and the first surface acoustic wave makes a first turn, and the first surface acoustic wave propagates along the side of the cover plate to the second curved surface, the curvature radius R2 of the second curved surface is greater than or equal to the wavelength of the first surface acoustic wave, and after passing through the second curved surface, the first surface acoustic wave propagates to the right along the upper surface of the cover plate, and the first surface acoustic wave makes a second turn. When the first surface acoustic wave propagates to the finger pressing on the cover plate, the second surface acoustic wave is generated by scattering of the fingerprint on the finger. The second surface acoustic wave is similar to the first surface acoustic wave, and propagates along the same propagation path as the first surface acoustic wave, passes through the second curved surface and makes two turns on the second curved surface, propagates to the lower surface of the cover plate, and is received by the ultrasonic transducer 120.

[0081] Further, when the cover of the screen 110 is a glass cover with a thickness of 0.5 mm to 1 mm (at this time, the wavelength λ of the first surface acoustic wave is 0.1 mm to 0.3 mm), the curvature radius of the first curved surface is 0.3 mm to 0.7 mm, and the curvature radius of the second curved surface is 0.3 mm to 0.7 mm.

[0082] Specifically, the processor 130 controls part or all of the plurality of ultrasonic transducers 120 to generate a first surface acoustic wave, and controls part or all of the plurality of ultrasonic transducers 120 to receive a second surface acoustic wave. The processor 130 may use the following method: Figure 6a The reflective transceiver mode shown controls part or all of the multiple ultrasonic transducers 120 to transmit and receive surface acoustic waves. In this case, the ultrasonic transducer 120 used to generate the first surface acoustic wave is the same as the ultrasonic transducer 120 used to receive the second surface acoustic wave. In the scenario where the multiple ultrasonic transducers 120 are coupled to at least two parallel edges of the lower surface of the cover plate of the screen 110, the processor 130 can also use the following method: Figure 6b The transmission transceiver mode shown controls part or all of the multiple ultrasonic transducers 120 to transmit and receive surface acoustic waves. At this time, the ultrasonic transducer 120 for generating the first surface acoustic wave and the ultrasonic transducer 120 for receiving the second surface acoustic wave are respectively located on two parallel edges of the lower surface of the cover plate of the screen 110.

[0083] It should be noted that Figures 2 to 5 , Figure 6a as well as Figure 6b The cover plate of the screen 110 shown in FIG. 1 is a cross-sectional view of the cover plate in the thickness direction.

[0084] Furthermore, the processor 130 adopts Figure 6a The reflective transceiver shown in the figure controls part or all of the ultrasonic transducers in the plurality of ultrasonic transducers 120 to transmit and receive surface acoustic waves, or adopts the reflective transceiver as shown in the figure. Figure 6b When the transmission transmission and reception mode shown in the figure controls part or all of the multiple ultrasonic transducers 120 to transmit and receive surface acoustic waves, the processor 130 can control the multiple ultrasonic transducers 120 to operate in a single-transmit and single-receive mode (that is, the processor 130 can excite one ultrasonic transducer 120 among the multiple ultrasonic transducers 120 to generate a first surface acoustic wave each time according to a set rule, and control one ultrasonic transducer 120 among the multiple ultrasonic transducers 120 to receive a second surface acoustic wave), a single-transmit and multiple-receive mode (that is, the processor 130 can control the multiple ultrasonic transducers 120 to operate in a single-transmit and single-receive mode according to a set rule, and control one ultrasonic transducer 120 among the multiple ultrasonic transducers 120 to receive a second surface acoustic wave. According to the set rules, one ultrasonic transducer 120 among the multiple ultrasonic transducers 120 can be stimulated each time to generate the first surface acoustic wave, and multiple ultrasonic transducers 120 among the multiple ultrasonic transducers 120 can be controlled to receive the second surface acoustic wave) or a multi-transmit multi-receive mode (that is, the processor 130 can, according to the set rules, stimulate multiple ultrasonic transducers 120 among the multiple ultrasonic transducers 120 each time to generate the first surface acoustic wave, and control multiple ultrasonic transducers 120 among the multiple ultrasonic transducers 120 to receive the second surface acoustic wave), etc.

[0085] Furthermore, if Figure 7 As shown, the terminal device 100 also includes a signal processing circuit 140, which is coupled to the processor 130 and the plurality of ultrasonic transducers 120, respectively, and is used to generate an excitation signal under the control of the processor 130, and the excitation signal is used to excite part or all of the plurality of ultrasonic transducers 120 to generate a first surface acoustic wave; and amplify the electrical signal corresponding to the second surface acoustic wave; the processor 130 is also used to: when it is determined that fingerprint recognition is required, control the signal processing circuit 140 to generate an excitation signal; and generate a fingerprint image according to the electrical signal corresponding to the amplified second surface acoustic wave. Among them, the signal processing circuit 140 can be implemented by an application specific integrated circuit (ASIC).

[0086] like Figure 8As shown, the signal processing circuit 140 may specifically include a signal generating circuit 141, a power amplifier circuit 142 and a preamplifier circuit 143. The signal generating circuit 141 is used to generate an excitation signal for exciting the ultrasonic transducer 120 under the control of the processor 130. The power amplifier circuit 142 is used to amplify the excitation signal generated by the signal generating circuit 141. The preamplifier circuit 143 is used to amplify the electrical signal corresponding to the second surface acoustic wave to improve the imaging accuracy of the fingerprint image. Further, the signal processing circuit 140 may also include a signal acquisition circuit 144, which is used to convert the amplified electrical signal corresponding to the second surface acoustic wave into a digital signal for processing by the processor 130.

[0087] In order to further improve the imaging accuracy of the fingerprint image, the processor 130 may pre-process the digital signal obtained by the signal processing circuit 140 before generating the fingerprint image according to the electrical signal corresponding to the second surface acoustic wave, such as filtering and noise reduction, so as to improve the signal-to-noise ratio of the digital signal, thereby improving the imaging accuracy of the fingerprint image. Figure 9a As shown, the processor 130 includes, in addition to the fingerprint control module 131 and the fingerprint imaging module 132, a signal preprocessing module 133, which is used to preprocess the digital signal obtained by the signal processing circuit 140 before the fingerprint imaging module 132 generates a fingerprint image according to the electrical signal corresponding to the second surface acoustic wave, and generate a fingerprint image according to the processed digital signal. Among them, the signal preprocessing module 133 can be implemented by software, that is, the processor 130 can implement the function of the signal preprocessing module 133 by calling the code instructions stored in the memory (not shown in the figure) in the terminal device 100, and the implementation method is simple and flexible.

[0088] Or, if Figure 9b As shown, the signal processing circuit 140 may further include a signal preprocessing circuit 145, which performs preprocessing such as filtering and noise reduction on the electrical signal corresponding to the amplified second surface acoustic wave output by the preamplifier circuit 143, so as to improve the quality of the electrical signal corresponding to the second surface acoustic wave, thereby improving the accuracy of the fingerprint image generated by the processor 130. In other words, the function of the above-mentioned signal preprocessing module 133 can also be implemented by a hardware circuit.

[0089] Further, after the processor 130 generates the fingerprint image according to the electrical signal corresponding to the second surface acoustic wave, it is also used to: match the generated fingerprint image with the pre-stored fingerprint image, and process the request of the application that triggers fingerprint recognition according to the matching result. Specifically, when the generated fingerprint image successfully matches the pre-stored fingerprint image, the processor 130 responds to the request of the application that triggers fingerprint recognition; when the generated fingerprint image fails to match the pre-stored fingerprint image, the processor 130 rejects the request of the application that triggers fingerprint recognition. For example, the application that triggers fingerprint recognition is a lock screen application. When the generated fingerprint image successfully matches the pre-stored fingerprint image, the processor 130 responds to the request of the lock screen application and performs an unlocking operation. When the generated fingerprint image fails to match the pre-stored fingerprint image, the processor 130 rejects the request of the lock screen application and does not perform an unlocking operation. For example, the application that triggers fingerprint recognition is a secure payment application. When the generated fingerprint image successfully matches the pre-stored fingerprint image, the processor 130 responds to the request of the payment application and performs a payment operation. When the generated fingerprint image fails to match the pre-stored fingerprint image, the processor 130 rejects the request of the payment application and does not perform a payment operation.

[0090] At this time, if Fig.10 As shown, the processor 130 includes, in addition to the fingerprint control module 131 and the fingerprint imaging module 132, a fingerprint matching module 134 and a fingerprint application module 135, wherein the fingerprint matching module 134 is used to match the generated fingerprint image with the pre-stored fingerprint image to obtain a matching result; the fingerprint application module 135 is used to process the application request that triggers fingerprint recognition according to the matching result. In a specific implementation, the fingerprint matching module 134 and the fingerprint application module 135 can be implemented by software, that is, the processor 130 can implement the functions of the fingerprint matching module 134 and the fingerprint application module 135 by calling the code instructions stored in the memory (not shown in the figure) in the terminal device 100.

[0091] In addition, when the generated fingerprint image fails to match the pre-stored fingerprint image, the processor 130 may also feed back a prompt message indicating the request failure to the application that triggered the fingerprint recognition.

[0092] Through the above scheme, when the processor 130 in the terminal device 100 determines that fingerprint identification is required, it controls the ultrasonic transducer 120 distributed at the edge of the lower surface of the cover plate of the screen 110 of the terminal device 100 to generate a surface acoustic wave that can cover the upper surface of the cover plate, and uses the surface acoustic wave scattered by the fingerprint on the finger at any position on the upper surface of the cover plate received by the ultrasonic transducer 120 to generate a fingerprint image, and then the fingerprint image can be used for fingerprint identification. Since the wavelength of the surface acoustic wave generated by the ultrasonic transducer 120 on the cover plate surface of the screen 110 is short, the spatial resolution (including the lateral (direction perpendicular to the propagation direction of the surface acoustic wave) resolution and the longitudinal (direction parallel to the propagation direction of the surface acoustic wave) resolution) of the fingerprint image generated by the processor 130 can be improved, and the surface acoustic wave attenuation is small, which is conducive to expanding the fingerprint detection range of the terminal device 100. In addition, since the dispersion of the surface acoustic wave is small, the longitudinal resolution of the fingerprint image generated by the processor 130 can be further improved.

[0093] Moreover, compared with the existing fingerprint recognition solutions based on ultrasonic body waves, the embodiment of the present application has low manufacturing tolerance requirements for the first curved surface and the second curved surface in the terminal device 100 for realizing the transmission of surface acoustic waves between the upper and lower surfaces of the cover plate of the screen 110, and the feasibility of mass production of the terminal device 100 is relatively high.

[0094] The present application also provides a full-screen fingerprint recognition method, which is applied to a terminal device 100, such as Fig.11 As shown, the full-screen fingerprint recognition method mainly includes the following steps:

[0095] S1101: When it is determined that fingerprint recognition is required, control some or all of the plurality of ultrasonic transducers 120 to generate a first surface acoustic wave, wherein the first surface acoustic wave propagates from the lower surface of the cover plate to the upper surface of the cover plate through the first curved surface and the second curved surface.

[0096] Specifically, the first surface acoustic wave propagates along the lower surface of the cover plate of the screen 110 to the first curved surface, propagates to the side surface of the cover plate of the screen 110 through the first curved surface (the first surface acoustic wave makes a first turn), propagates along the side surface of the cover plate of the screen 110 to the second curved surface, and propagates to the upper surface of the cover plate of the screen through the second curved surface (the first surface acoustic wave makes a second turn).

[0097] S1102: Control some or all of the multiple ultrasonic transducers 120 to receive a second surface wave, wherein the second surface acoustic wave is generated after the first surface acoustic wave is scattered by the finger pressing the upper surface of the cover plate, and the second surface acoustic wave propagates from the upper surface of the cover plate to the lower surface of the cover plate through the second curved surface and the first curved surface.

[0098] Specifically, the second surface acoustic wave propagates along the upper surface of the cover plate of the screen 110 to the second curved surface, propagates to the side surface of the cover plate of the screen 110 through the second curved surface (the second surface acoustic wave makes a first turn), propagates along the side surface of the cover plate of the screen 110 to the first curved surface, propagates to the lower surface of the cover plate of the screen 110 through the first curved surface (the second surface acoustic wave makes a second turn), and is received by the ultrasonic transducer arranged on the lower surface of the cover plate of the screen 110.

[0099] S1103: Generate a fingerprint image according to the electrical signal corresponding to the second surface acoustic wave. The fingerprint image is an image of the fingerprint on the finger pressing the upper surface of the cover.

[0100] In step S1101, the terminal device 100 can specifically control part or all of the multiple ultrasonic transducers 120 to generate a first surface acoustic wave by the following method: generating an excitation signal, and using the excitation signal to excite part or all of the multiple ultrasonic transducers to generate the first surface acoustic wave. Further, in order to increase the energy of the first surface acoustic wave and thus improve the accuracy of fingerprint recognition, after the terminal device 100 generates the excitation signal, before using the excitation signal to excite part or all of the multiple ultrasonic transducers, the excitation signal can also be amplified, and the amplified excitation signal can be used to excite part or all of the multiple ultrasonic transducers.

[0101] In step S1101 and step S1102, the terminal device 100 controls part or all of the plurality of ultrasonic transducers to generate a first surface acoustic wave, and controls part or all of the plurality of ultrasonic transducers 120 to receive a second surface acoustic wave. The terminal device may use the following method: Figure 6a The reflective transceiver mode shown controls part or all of the multiple ultrasonic transducers 120 to transmit and receive surface acoustic waves. At this time, the ultrasonic transducer 120 used to generate the first surface acoustic wave is the same as the ultrasonic transducer 120 used to receive the second surface acoustic wave. In the scenario where the multiple ultrasonic transducers 120 are combined on at least two parallel edges of the lower surface of the cover plate of the screen 110, the terminal device 100 can also adopt the following method: Figure 6b The transmission transceiver mode shown controls part or all of the multiple ultrasonic transducers 120 to transmit and receive surface acoustic waves. At this time, the ultrasonic transducer 120 for generating the first surface acoustic wave and the ultrasonic transducer 120 for receiving the second surface acoustic wave are respectively located on two parallel edges of the lower surface of the cover plate of the screen 110.

[0102] Furthermore, the terminal device 100 adopts Figure 6aThe reflective transceiver shown in the figure controls part or all of the ultrasonic transducers in the plurality of ultrasonic transducers 120 to transmit and receive surface acoustic waves, or adopts the reflective transceiver as shown in the figure. Figure 6b When the transmission transmission and reception mode shown controls part or all of the multiple ultrasonic transducers 120 to transmit and receive surface acoustic waves, the terminal device 100 can control the multiple ultrasonic transducers 120 to operate in a single-transmit single-receive mode (i.e., the terminal device 100 can excite one ultrasonic transducer among the multiple ultrasonic transducers 120 to generate a first surface acoustic wave each time according to a set rule, and control one ultrasonic transducer among the multiple ultrasonic transducers 120 to receive a second surface acoustic wave), a single-transmit multiple-receive mode (i.e., the terminal device 100 can excite one ultrasonic transducer among the multiple ultrasonic transducers to generate a first surface acoustic wave each time according to a set rule, and control multiple ultrasonic transducers among the multiple ultrasonic transducers to receive a second surface acoustic wave), or a multiple-transmit multiple-receive mode (i.e., the terminal device 100 can excite multiple ultrasonic transducers among the multiple ultrasonic transducers 120 to generate a first surface acoustic wave each time according to a set rule, and control multiple ultrasonic transducers among the multiple ultrasonic transducers 120 to receive a second surface acoustic wave), etc.

[0103] In order to further improve the imaging accuracy of the fingerprint image, before executing step S1103, the terminal device 100 may also pre-process the electrical signal corresponding to the second surface acoustic wave, such as filtering, to improve the signal-to-noise ratio of the electrical signal corresponding to the second surface acoustic wave. In step S1103, when the terminal device 100 generates a fingerprint image based on the second surface acoustic wave, it may specifically use an ultrasonic imaging algorithm such as a beamforming algorithm (such as a TFM algorithm or a SAFT algorithm), a tomography algorithm (such as a DT algorithm), or a super-resolution imaging algorithm (such as a TR-MUSIC algorithm) to generate the fingerprint image.

[0104] After executing step S1103, the terminal device 100 can also match the generated fingerprint image with the pre-stored fingerprint image, and process the request of the application that triggers fingerprint recognition according to the matching result. Specifically, when the generated fingerprint image successfully matches the pre-stored fingerprint image, the terminal device 100 responds to the request of the application that triggers fingerprint recognition; when the generated fingerprint image fails to match the pre-stored fingerprint image, the terminal device 100 rejects the request of the application that triggers fingerprint recognition. For example, the application that triggers fingerprint recognition is a lock screen application. When the generated fingerprint image successfully matches the pre-stored fingerprint image, the terminal device 100 responds to the request of the lock screen application and performs an unlocking operation. When the generated fingerprint image fails to match the pre-stored fingerprint image, the terminal device 100 rejects the request of the lock screen application and does not perform an unlocking operation. For example, the application that triggers fingerprint recognition is a secure payment application. When the generated fingerprint image successfully matches the pre-stored fingerprint image, the terminal device 100 responds to the request of the payment application and performs a payment operation. When the generated fingerprint image fails to match the pre-stored fingerprint image, the terminal device 100 rejects the request of the payment application and does not perform a payment operation.

[0105] In addition, when the generated fingerprint image fails to match the pre-stored fingerprint image, the terminal device 100 may also feed back a prompt message indicating the request failure to the application that triggered the fingerprint recognition.

[0106] Through the above method, when the terminal device 100 determines that fingerprint identification is required, the terminal device 100 controls the ultrasonic transducer 120 distributed at the edge of the lower surface of the cover plate of the screen 110 of the terminal device 100 to generate a surface acoustic wave that can cover the upper surface of the cover plate, and uses the ultrasonic transducer 120 to receive the surface acoustic wave scattered by the fingerprint on the finger at any position on the upper surface of the cover plate to generate a fingerprint image, and then the fingerprint image can be used for fingerprint identification. Since the wavelength of the surface acoustic wave generated by the ultrasonic transducer 120 on the surface of the cover plate of the screen 110 is short, the above method can improve the spatial resolution of the fingerprint image, and the surface acoustic wave attenuation is small, which is conducive to expanding the fingerprint detection range of the terminal device 100. In addition, since the dispersion of the surface acoustic wave is small, the above method can further improve the longitudinal resolution of the fingerprint image.

[0107] Compared with the existing fingerprint recognition solutions based on ultrasonic body waves, the embodiment of the present application has low manufacturing tolerance requirements for the first curved surface and the second curved surface in the terminal device 100 for realizing the transmission of surface acoustic waves between the upper and lower surfaces of the cover plate of the screen, and the feasibility of mass production of the terminal device 100 is relatively high.

[0108] The present application is described with reference to the flowchart and / or block diagram of the method, device (system) and computer program product according to the embodiment of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, and the combination of the process and / or box in the flowchart and / or block diagram can be realized by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device produce a device for realizing the function specified in one process or multiple processes in the flowchart and / or one box or multiple boxes in the block diagram.

[0109] These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer-readable memory produce a manufactured product including an instruction device that implements the functions specified in one or more processes in the flowchart and / or one or more boxes in the block diagram.

[0110] These computer program instructions may also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, whereby the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in one or more processes in the flowchart and / or one or more boxes in the block diagram.

[0111] Obviously, those skilled in the art can make various changes and modifications to the embodiments of the present application without departing from the spirit and scope of the embodiments of the present application. Thus, if these modifications and variations of the embodiments of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims

1. A terminal device, characterized in that: include: A screen, a plurality of ultrasonic transducers and a processor, wherein the plurality of ultrasonic transducers are respectively coupled to the edge of the lower surface of the cover plate of the screen, and the plurality of ultrasonic transducers are also respectively coupled to the processor; a surface corresponding to the connection between the lower surface of the cover plate and the side surface of the cover plate is a first curved surface, and a surface corresponding to the connection between the upper surface of the cover plate and the side surface of the cover plate is a second curved surface; The ultrasonic transducer is used to generate a first surface acoustic wave under the control of the processor, and the first surface acoustic wave propagates from the lower surface of the cover plate to the upper surface of the cover plate through the first curved surface and the second curved surface; The ultrasonic transducer is further used to receive a second surface acoustic wave under the control of the processor, and output an electrical signal corresponding to the second surface acoustic wave to the processor, wherein the second surface acoustic wave is generated after the first surface acoustic wave is scattered by a finger pressing the upper surface of the cover plate, and the second surface acoustic wave propagates from the upper surface of the cover plate to the lower surface of the cover plate through the second curved surface and the first curved surface; The processor is used for controlling part or all of the plurality of ultrasonic transducers to generate the first surface acoustic wave when it is determined that fingerprint recognition is required; The processor is further configured to control some or all of the plurality of ultrasonic transducers to receive the second surface acoustic wave, and generate a fingerprint image according to an electrical signal corresponding to the second surface acoustic wave; Wherein, on the propagation path of the first surface acoustic wave, the radius of curvature of the first curved surface and the radius of curvature of the second curved surface are greater than or equal to the wavelength of the first surface acoustic wave; on the propagation path of the second surface acoustic wave, the radius of curvature of the first curved surface and the radius of curvature of the second curved surface are greater than or equal to the wavelength of the second surface acoustic wave; wherein the wavelength of the first surface acoustic wave is equal to the wavelength of the second surface acoustic wave.

2. The terminal device according to claim 1, characterized in that: When the cover plate is a glass cover plate with a thickness of 0.5 mm to 1 mm, the curvature radius of the first curved surface is 0.3 mm to 0.7 mm, and the curvature radius of the second curved surface is 0.3 mm to 0.7 mm.

3. The terminal device according to claim 1 or 2, characterized in that: The ultrasonic transducer is an oblique-incidence surface acoustic wave transducer, and the oblique-incidence surface acoustic wave transducer includes a piezoelectric element and a wedge; The piezoelectric element is used to generate longitudinal waves in the wedge block, and the wedge block is used to convert the longitudinal waves into surface acoustic waves at the interface between the wedge block and the cover plate.

4. The terminal device according to claim 3, characterized in that: The cross section of the wedge is a right triangle, and the incident angle θ of the wedge satisfies the following formula: in, is the velocity of the longitudinal wave, is the wave velocity of the first surface acoustic wave.

5. The terminal device according to claim 1 or 2, characterized in that: The ultrasonic transducer is an interdigital transducer, and the interdigital transducer comprises a piezoelectric element and interdigital electrodes.

6. The terminal device according to claim 5, characterized in that: The finger width and the spacing of the interdigitated electrodes are both λ / 4, where λ is the wavelength of the first surface acoustic wave.

7. The terminal device according to any one of claims 1, 2, 4 and 6, characterized in that: A shielding material is disposed on an area of ​​the lower surface of the cover plate for arranging the plurality of ultrasonic transducers, wherein the shielding material is used to shield the plurality of ultrasonic transducers, and an acoustic impedance of the shielding material matches an acoustic impedance of the cover plate.

8. The terminal device according to any one of claims 1, 2, 4 and 6, characterized in that: The plurality of ultrasonic transducers are linearly arrayed at the edge of the lower surface of the cover plate, and the distance between two adjacent ultrasonic transducers is determined according to the resolution of the fingerprint image.

9. The terminal device according to any one of claims 1, 2, 4 and 6, characterized in that: It also includes a signal processing circuit, which is used to generate an excitation signal under the control of the processor, wherein the excitation signal is used to excite part or all of the plurality of ultrasonic transducers to generate the first surface acoustic wave; and amplify the electrical signal corresponding to the second surface acoustic wave; The processor is further configured to: when it is determined that fingerprint identification is required, control the signal processing circuit to generate the excitation signal; and generate the fingerprint image according to the amplified electrical signal corresponding to the second surface acoustic wave.

10. The terminal device according to any one of claims 1, 2, 4 and 6, characterized in that: The processor is further configured to: The generated fingerprint image is matched with a pre-stored fingerprint image, and a request for an application that triggers fingerprint recognition is processed according to the matching result.

11. A fingerprint recognition method, characterized in that: Applied to the terminal device according to any one of claims 1 to 10, the method comprises: When it is determined that fingerprint recognition is required, controlling part or all of the plurality of ultrasonic transducers to generate a first surface acoustic wave, wherein the first surface acoustic wave propagates from the lower surface of the cover plate to the upper surface of the cover plate through the first curved surface and the second curved surface; controlling part or all of the plurality of ultrasonic transducers to receive a second surface acoustic wave, wherein the second surface acoustic wave is generated after the first surface acoustic wave is scattered by a finger pressing the upper surface of the cover plate, and the second surface acoustic wave propagates from the upper surface of the cover plate to the lower surface of the cover plate through the second curved surface and the first curved surface; generating a fingerprint image according to the electrical signal corresponding to the second surface acoustic wave; Wherein, on the propagation path of the first surface acoustic wave, the radius of curvature of the first curved surface and the radius of curvature of the second curved surface are greater than or equal to the wavelength of the first surface acoustic wave; on the propagation path of the second surface acoustic wave, the radius of curvature of the first curved surface and the radius of curvature of the second curved surface are greater than or equal to the wavelength of the second surface acoustic wave; wherein the wavelength of the first surface acoustic wave is equal to the wavelength of the second surface acoustic wave.

Images