Ultrasonic detection apparatus and electronic device

Abstract

Provided in the present invention are an ultrasonic detection apparatus and an electronic device. The ultrasonic detection apparatus is disposed below a cover plate of an electronic device, and is used for performing touch detection on the cover plate. The ultrasonic detection apparatus comprises a piezoelectric transducer and a circuit unit, wherein the piezoelectric transducer is used for transmitting a first ultrasonic signal to the cover plate, receiving a first ultrasonic reflected signal formed after the first ultrasonic signal is reflected, converting the first ultrasonic reflected signal into a first electrical signal, and inputting the first electrical signal into the circuit unit; and the circuit unit is used for generating, on the basis of the first electrical signal, a touch detection signal used for indicating a touch state of the cover plate.

Description

[0001] Ultrasonic Detection Device and Electronic Device This application claims priority to an invention application filed on February 8, 2024, with application number "202410177052.X," and entitled "Ultrasonic Detection Device and Electronic Device," the entire contents of which are incorporated herein by reference. Technical Field The present invention relates to the field of touch detection technology, and more particularly to an ultrasonic detection device and electronic device. Background Art Currently, capacitive touch detection devices are commonly used in related art to detect finger touches. For example, the capacitance between a detection electrode and a touch pad in a capacitive touch detection device is detected to determine whether a finger touches the touch pad. However, the detection performance of a capacitive touch detection device is significantly affected by the environment. For example, dust falling on the touch pad can cause a change in the capacitance between the detection electrode and the touch pad. Changes in ambient temperature and humidity can also cause a change in the capacitance between the detection electrode and the touch pad, resulting in poor stability in touch detection by the capacitive touch detection device. SUMMARY In view of this, embodiments of the present application provide an ultrasonic detection device and electronic device that at least partially address the aforementioned issues. According to a first aspect of an embodiment of the present application, an ultrasonic detection device is provided. The ultrasonic detection device is disposed under a cover of an electronic device and is configured to perform touch detection on the cover. The ultrasonic detection device includes: a piezoelectric transducer and a circuit unit. The piezoelectric transducer is configured to transmit a first ultrasonic signal toward the cover, receive a first ultrasonic reflection signal formed by reflection of the first ultrasonic signal, convert the first ultrasonic reflection signal into a first electrical signal, and input the first electrical signal into the circuit unit. The circuit unit is configured to generate a touch detection signal indicating a touch state of the cover based on the first electrical signal. In one possible implementation, the piezoelectric transducer is configured to transmit a second ultrasonic signal toward the cover, receive a second ultrasonic reflection signal formed by the transmission of the second ultrasonic signal, convert the second ultrasonic reflection signal into a second electrical signal, and input the second electrical signal into the circuit unit. The circuit unit is configured to generate a fingerprint recognition signal indicating fingerprint features based on the second electrical signal.In one possible implementation, the piezoelectric transducer includes an electrode array, a piezoelectric layer, and a common electrode, wherein the common electrode and the electrode array are respectively located on both sides of the piezoelectric layer; the common electrode is used to drive the piezoelectric layer to transmit the first ultrasonic signal or the second ultrasonic signal; the piezoelectric layer is used to convert the first ultrasonic reflection signal into the first electrical signal acting on the electrode array after receiving the first ultrasonic reflection signal, and to convert the second ultrasonic reflection signal into the second electrical signal acting on the electrode array after receiving the second ultrasonic reflection signal; wherein, when the piezoelectric layer transmits the first ultrasonic signal or the second ultrasonic signal, the electrode array is grounded, and when the piezoelectric layer receives the first ultrasonic reflection signal or the second ultrasonic reflection signal, the common electrode is grounded. In one possible implementation, the electrode array includes multiple electrodes; the circuit unit includes multiple preprocessing circuits and an output unit; the multiple preprocessing circuits are all connected to the output unit; and different preprocessing circuits are connected to different electrodes; the preprocessing circuit is used to preprocess the first electrical signal to generate a first preprocessing signal, or preprocess the second electrical signal to generate a second preprocessing signal; the output unit is used to generate the touch detection signal based on the first preprocessing signal and output the touch detection signal, or generate the finger level identification signal based on the second preprocessing signal and output the finger level identification signal; when the piezoelectric layer receives the first ultrasonic reflection signal, the preprocessing circuits connected to some of the electrodes included in the electrode array are in an active state, and the preprocessing circuits connected to other electrodes included in the electrode array are in a dormant state; when the piezoelectric layer receives the second ultrasonic reflection signal, the preprocessing circuits connected to all the electrodes included in the electrode array are in an active state. In one possible implementation, the circuit unit is bonded to the electrode array; the common electrode is bonded to the cover plate via an adhesive layer, or the circuit unit is bonded to the cover plate via an adhesive layer. In one possible implementation, if the piezoelectric layer begins transmitting the first ultrasonic signal to the cover plate at a first moment, the piezoelectric layer is configured to receive the first ultrasonic reflection signal after a first time has passed since the first moment, where the first time has a value in the range of (1.8T to 3T); T is the time interval between the piezoelectric layer starting to transmit the ultrasonic signal and the piezoelectric layer starting to receive a target reflection signal, where the target reflection signal is a signal formed by the touch surface of the cover plate reflecting the ultrasonic signal.In one possible implementation, if the piezoelectric layer begins transmitting the second ultrasonic signal to the cover plate at a second moment, the piezoelectric layer is configured to receive the second ultrasonic reflection signal after a second time has elapsed since the second moment; the second time has a value range different from the value range of the first time. In one possible implementation, the second time has a value range of (1.5T to 2T). According to a second aspect of an embodiment of the present application, an electronic device is provided, comprising: a cover plate and an ultrasonic detection device as described above; the cover plate is configured to provide a touch surface configured to receive a touch by a finger; and the ultrasonic detection device is disposed beneath the cover plate to perform touch detection on the cover plate. In one possible implementation, the cover plate is formed of a conductive material or a non-conductive material. In an embodiment of the present application, the ultrasonic detection device includes a piezoelectric transducer and a circuit unit. The piezoelectric transducer can transmit a first ultrasonic signal to the cover plate, receive a first ultrasonic reflection signal formed by reflection of the first ultrasonic signal, convert the first ultrasonic reflection signal into a first electrical signal, and input the first electrical signal into the circuit unit. The circuit unit can generate a touch detection signal indicating the touch status of the cover plate based on the first electrical signal, thereby facilitating the determination of whether a finger is on the cover plate using the touch detection signal. Thus, the embodiment of the present application generates a touch detection signal based on a first ultrasonic reflection signal formed by the reflection of the first ultrasonic signal. Because dust has a very low acoustic impedance, and ultrasonic signals are less affected by temperature and humidity, generating a touch detection signal based on the first ultrasonic reflection signal can reduce the impact of environmental factors such as dust, temperature, and humidity on the touch detection signal, thereby improving the accuracy of detecting a finger touch on the cover plate. BRIEF DESCRIPTION OF THE DRAWINGS To more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art description. Obviously, the drawings described below represent only some of the embodiments described in the embodiments of the present application. Those skilled in the art can also derive other drawings based on these drawings. Figure 1 is a schematic structural diagram of an ultrasonic detection device provided in an alternative embodiment of the present application. Figure 2 is a signal timing diagram provided in an alternative embodiment of the present application. Figure 3 is a layout diagram of an electrode array provided in an alternative embodiment of the present application. Figure 4 is a diagram illustrating the arrangement of some electrodes in an electrode array according to an optional embodiment of the present application. Figure 5 is a diagram illustrating the arrangement of some electrodes in another electrode array according to an optional embodiment of the present application. Figure 6 is a diagram illustrating the arrangement of some electrodes in yet another electrode array according to an optional embodiment of the present application.FIG7 is a schematic diagram of the structure of another ultrasonic detection device provided in an optional embodiment of the present application. FIG8 is a schematic diagram of the overall workflow of an ultrasonic detection device provided in an optional embodiment of the present application. FIG9 is a schematic diagram of the workflow of an ultrasonic detection device in touch detection mode provided in an optional embodiment of the present application. FIG. 1 is a schematic diagram of the workflow of an ultrasonic detection device in touch detection mode provided in an optional embodiment of the present application.

[0002] 100, ultrasonic detection device; 110, piezoelectric transducer; 111, electrode array; 1111, electrode; 112, piezoelectric layer; 113, common electrode; 120, circuit unit; 121, silicon substrate;

[0003] 200, cover plate; 300, adhesive layer. DETAILED DESCRIPTION To help those skilled in the art better understand the technical solutions in the embodiments of this application, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments represent only a portion of the embodiments of this application, and not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of this application should fall within the scope of protection of the embodiments of this application. The terms used in this application are intended solely to describe specific embodiments and are not intended to limit this application. As used in this application and the appended claims, the singular forms "a," "an," "the," and "the" are intended to include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the term "and / or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items. It should be understood that while the terms "first," "second," "third," etc., may be used in this application to describe various information, such information should not be limited to these terms. These terms are used solely to distinguish information of the same type from one another. For example, without departing from the scope of this application, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Depending on the context, the term "if" as used herein may be interpreted as "at the time of," "when," or "in response to a determination." This application provides an ultrasonic detection device and electronic device to address the aforementioned issues existing in the related art. The ultrasonic detection device provided in an embodiment of this application is described in detail below with reference to the accompanying drawings. As shown in FIG1 , an ultrasonic detection device 100 is disposed beneath a cover plate 200 of an electronic device to perform touch detection on the cover plate 200. The ultrasonic detection device 100 includes a piezoelectric transducer 110 and a circuit unit 120. In this embodiment of the application, the electronic device may be a mobile phone, tablet, or other electronic device, and the cover plate 200 of the electronic device may be the cover plate 200 of the fingerprint recognition area on the side of the mobile phone, tablet, or other electronic device. The piezoelectric transducer 110 is used to transmit a first ultrasonic signal to the cover plate 200, and receive a first ultrasonic reflection signal formed by the reflection of the first ultrasonic signal, convert the first ultrasonic reflection signal into a first electrical signal, and input the first electrical signal into the circuit unit 120. oThe piezoelectric transducer 110 may include a piezoelectric material, such as polyvinylidene fluoride (PVDF). The piezoelectric effect of the piezoelectric material is utilized to convert a voltage signal acting on the piezoelectric material into a corresponding ultrasonic signal, or vice versa. The circuit unit 120 is configured to generate a touch detection signal indicating the touch state of the cover plate 200 based on the first electrical signal. The circuit unit 120 may be an integrated circuit in the form of a chip to reduce the space occupied by the circuit unit 120. It should be understood that the touch state of the cover plate 200 includes two states: a finger touching the touch surface of the cover plate 200 and no finger touching the touch surface of the cover plate 200. When no finger is touching the touch surface of the cover plate 200, the touch surface of the cover plate 200 is air. The acoustic impedance of common materials used for the cover plate 200 (e.g., aluminum alloy, plastic, etc.) is generally greater than 1.5 Mrayl, the acoustic impedance of air is approximately 0.00043 Mrayl, and the acoustic impedance of a finger is approximately Z2=1.5 Mrayl. If the acoustic impedance of the cover plate 200 is denoted as Z1, and the acoustic impedance of the object in contact with the touch surface of the cover plate 200 is denoted as Z2, the reflectivity rf of the first ultrasonic signal emitted by the piezoelectric transducer 110 toward the cover plate 200 at the touch surface of the cover plate 200 can be calculated using the following formula.

[0004] Z1 - Z2 rf = -

[0005] Z1 + Z2: When there's no finger touching the cover plate 200, Z2 = 0.00043 Mrayl. At this point, rf is approximately 1, and the first ultrasonic signal is almost entirely reflected back from the touch surface of the cover plate 200 to the piezoelectric transducer 110. When there's a finger touching the cover plate 200, Z2 = 1.5 Mrayl. At this point, rf is significantly less than 1, and only a portion of the first ultrasonic signal is reflected back from the touch surface of the cover plate 200 to the piezoelectric transducer 110. That is, when the first ultrasonic signal is reflected from the touch surface of the cover plate 200, there's significant reflection loss. For example, as shown in FIG2 , the solid line on the V-axis represents the waveform of the first ultrasonic signal over time. The solid line on the R-axis represents the waveform of the first ultrasonic reflection signal over time when the touch surface of the cover plate 200 is untouched, and the dashed line on the R-axis represents the waveform of the first ultrasonic reflection signal over time when the touch surface of the cover plate 200 is touched. As shown in Figure 2, there is a significant difference in the fluctuation amplitude between the first ultrasonic reflection signal obtained when the cover plate 200 is touched and the first ultrasonic reflection signal obtained when the cover plate 200 is not touched. Because the piezoelectric transducer 110 converts the first ultrasonic reflection signal into a first electrical signal, there is also a corresponding difference between the first electrical signal converted from the first ultrasonic reflection signal when the cover plate 200 is touched and the first electrical signal converted from the first ultrasonic reflection signal when the cover plate 200 is not touched. Therefore, a touch detection signal indicating the touch status of the cover plate 200 can be generated based on the first electrical signal. In some optional embodiments, the circuit unit 120 may use the received first electrical signal as the touch detection signal, or may use the processed signal as the touch detection signal after amplifying, differentiating, or performing noise reduction processing on the first electrical signal. All of these are within the scope of the present invention. As shown in Figure 2, in some optional embodiments, the piezoelectric transducer 110 can continuously transmit a first ultrasonic signal multiple times and receive a corresponding first electrical signal from the reflected first ultrasonic signal from each transmission, enabling the circuit unit 120 to generate a touch detection signal corresponding to the multiple transmitted first ultrasonic signals. By superimposing these touch detection signals, touch detection can be performed by integrating the first ultrasonic reflection signals obtained from the multiple transmissions of the first ultrasonic signal, thereby more accurately determining the touch status of the cover plate 200. In this embodiment of the present application, the ultrasonic detection device 100 includes the piezoelectric transducer 110 and the circuit unit 120.The piezoelectric transducer 110 can transmit a first ultrasonic signal toward the cover plate 200 and receive a first ultrasonic reflection signal formed by the reflection of the first ultrasonic signal. After converting the first ultrasonic reflection signal into a first electrical signal, the first electrical signal is input into the circuit unit 120. Based on the first electrical signal, the circuit unit 120 can generate a touch detection signal indicating the touch state of the cover plate 200, thereby facilitating the determination of whether a finger is present on the cover plate 200. Specifically, embodiments of the present application can generate a touch detection signal based on the first ultrasonic reflection signal formed by the reflection of the first ultrasonic signal. Because dust has a very low acoustic impedance and ultrasonic signals are less affected by temperature and humidity, generating a touch detection signal based on the first ultrasonic reflection signal can reduce the impact of environmental factors such as dust, temperature, and humidity on the touch detection signal, significantly improving the stability of touch detection. In some optional embodiments, the piezoelectric transducer 110 is configured to transmit a second ultrasonic signal toward the cover plate 200 and receive a second ultrasonic reflection signal generated by the transmitted second ultrasonic signal. After converting the second ultrasonic reflection signal into a second electrical signal, the second electrical signal is input into the circuit unit 120. The circuit unit 120 is configured to generate a fingerprint recognition signal indicating the fingerprint-level characteristics based on the second electrical signal. Because fingerprints have uneven surfaces, when a finger presses on the touch surface of the cover plate 200, the protruding portions of the fingerprint may align with the touch surface, while the concave portions of the fingerprint form a gap between the touch surface and the fingerprint. When the second ultrasonic signal acts on the touch surface, the second ultrasonic reflection signal reflected by the fingerprint-aligned and gapped portions of the fingerprint on the touch surface has different intensities, resulting in different corresponding second electrical signals. Based on this, a fingerprint recognition signal indicating the fingerprint characteristics can be generated based on the second electrical signal. Subsequently, the fingerprint recognition signal is processed accordingly to obtain a corresponding finger-level image. The specific implementation of the above process can be referred to in related art and will not be further described here. In this embodiment of the present application, multiple second ultrasonic signals are emitted, and finger-level identification signals corresponding to the multiple transmitted second ultrasonic signals are generated. Based on the fingerprint identification signals corresponding to the multiple transmitted second ultrasonic signals, multiple finger-level images can be obtained. By superimposing the multiple fingerprint images, a clearer fingerprint image can be obtained, thereby improving the accuracy of finger-level identification. Existing under-screen ultrasonic fingerprint recognition solutions typically require touch detection using a related capacitive touch detection device first, and then ultrasonic fingerprint recognition is performed after a finger touch is detected on the screen.Although existing under-screen ultrasonic fingerprint recognition solutions can perform both touch detection and fingerprint recognition, they still have some drawbacks. For example, the corresponding circuit structure is relatively complex and occupies a large space. Due to the limitations of capacitance detection, this solution is difficult to apply to metal touch surfaces. However, the ultrasonic detection device 100 provided in the embodiments of the present application can at least partially overcome these shortcomings of existing under-screen ultrasonic fingerprint recognition solutions. In this embodiment of the present application, a piezoelectric transducer 110 can transmit a second ultrasonic signal to the cover plate 200, receive a second ultrasonic reflection signal generated by the transmitted second ultrasonic signal, convert the second ultrasonic reflection signal into a second electrical signal, and input the second electrical signal into the circuit unit 120. Circuit unit 120 generates a finger-level recognition signal indicating finger-level features based on the second electrical signal, thereby enabling fingerprint recognition using the fingerprint recognition signal. This allows both touch detection and fingerprint recognition to be performed via the piezoelectric transducer 110, improving the utilization of the piezoelectric transducer 110 and eliminating the need for separate sensors for touch detection and fingerprint recognition. This reduces the complexity of the associated circuit structure and reduces the space occupied. Furthermore, because the acoustic impedance of metal materials such as aluminum alloy and stainless steel is much greater than that of air, the touch surface of the cover plate 200 in the embodiment of the present application can be made of metal materials such as aluminum alloy and stainless steel. This means that the ultrasonic detection device 100 in the embodiment of the present application has high applicability. As shown in FIG1 , in some optional embodiments, the piezoelectric transducer 110 includes an electrode array 111, a piezoelectric layer 112, and a common electrode 113. The common electrode 113 and the electrode array 111 are respectively located on either side of the piezoelectric layer 112. The common electrode 113 is used to drive the piezoelectric layer 112 to transmit the first ultrasonic signal or the second ultrasonic signal. In the embodiment of the present application, a high-voltage pulse can be received by the common electrode 113 and applied to the piezoelectric layer 112, thereby driving the piezoelectric layer 112 to emit a first ultrasonic signal or a second ultrasonic signal. It should be understood that the same high-voltage pulse can drive the piezoelectric layer 112 to emit the same first ultrasonic signal and second ultrasonic signal, while different high-voltage pulses can drive the piezoelectric layer 112 to emit different first and second ultrasonic signals. Upon receiving a first ultrasonic reflection signal, the piezoelectric layer 112 is configured to convert the first ultrasonic reflection signal into a first electrical signal that acts on the electrode array 111. Upon receiving a second ultrasonic reflection signal, the piezoelectric layer 112 is configured to convert the second ultrasonic reflection signal into a second electrical signal that acts on the electrode array 111.As shown in Figures 1 and 3, the electrode array 111 can be an array composed of multiple electrodes 1111 arranged in an array, and can typically be disposed on the silicon substrate 121 of the chip. When the piezoelectric layer 112 transmits the first ultrasonic signal or the second ultrasonic signal, the electrode array 111 is grounded. When the piezoelectric layer 112 receives the first ultrasonic reflection signal or the second ultrasonic reflection signal, the common electrode 113 is grounded. In the embodiment of the present application, grounding the electrode array 111 when the piezoelectric layer 112 transmits the first ultrasonic signal or the second ultrasonic signal facilitates the formation of a high voltage between the common electrode 113 and the electrode array 111, increasing the intensity of the transmitted ultrasonic wave and enhancing the sensitivity of the piezoelectric transducer 110. Furthermore, a consistent voltage is formed between the common electrode 113 and all electrodes in the electrode array 111, so that the piezoelectric layer 112 between the common electrode 113 and each electrode in the electrode array 111 can generate a consistent first ultrasonic signal or second ultrasonic signal, thereby avoiding the generation of clutter and improving the accuracy of touch detection or fingerprint recognition. Furthermore, by grounding the common electrode 113 when the piezoelectric layer 112 receives the first ultrasonic reflection signal or the second ultrasonic reflection signal, the voltage at the common electrode 113 can be prevented from adversely affecting the first or second electrical signal acting on the electrode array 111, thereby ensuring the effectiveness of touch detection or fingerprint recognition. In some optional embodiments, the electrode array 111 includes multiple electrodes. The circuit unit includes multiple preprocessing circuits and an output unit. The multiple preprocessing circuits are all connected to the output unit; different preprocessing circuits are connected to different electrodes. The preprocessing circuit is configured to preprocess the first electrical signal to generate a first preprocessed signal, or to preprocess the second electrical signal to generate a second preprocessed signal. Exemplarily, the preprocessing performed by the preprocessing circuit on the first or second electrical signal may include operations such as detecting signal amplitude and noise reduction, thereby reducing the processing workload of the output unit. The output unit is configured to generate a touch detection signal based on the first preprocessed signal and output the touch detection signal, or to generate a fingerprint recognition signal based on the second preprocessed signal and output the fingerprint recognition signal. It should be understood that in the implementation of this application, the preprocessing circuit and the output unit cooperate to perform preprocessing and subsequent processing on the first electrical signal or the second electrical signal. This application does not limit the division of labor between the preprocessing circuit and the output unit. When the piezoelectric layer 112 receives the first ultrasonic reflection signal, the preprocessing circuit connected to some of the electrodes 1111 included in the electrode array 111 is in an active state, while the preprocessing circuit connected to other electrodes 1111 included in the electrode array 111 is in a dormant state.When the preprocessing circuit is in a dormant state, it no longer performs the corresponding preprocessing work, thereby saving corresponding power consumption. For example, Figures 4-6 illustrate some of the electrodes 1111 of the electrode array 111. When the piezoelectric layer 112 receives the first ultrasonic reflection signal, only the preprocessing circuits connected to some of the electrodes 1111 shown in Figures 4, 5, or 6 can be put into an active state, while the preprocessing circuits connected to the remaining electrodes 1111 are put into a dormant state. By putting some of the preprocessing circuits into a dormant state, the power consumption of preprocessing can be reduced, and the output unit only needs to process the first preprocessed electrical signals generated by some of the preprocessing circuits, thereby simultaneously reducing the power consumption of the output unit. In some optional embodiments, when the piezoelectric layer 112 receives the second ultrasonic reflection signal, the preprocessing circuits connected to all of the electrodes included in the electrode array 111 are all put into an active state. As described above, after the second ultrasonic reflection signal is converted into a second electrical signal, the circuit unit 120 can generate a finger level identification signal indicating the finger level characteristics based on the second electrical signal. Therefore, when the piezoelectric layer 112 receives the second ultrasonic reflection signal, the preprocessing circuit connected to all electrodes included in the electrode array 111 is in an operational state. This allows the output unit to receive the second preprocessed signal generated based on the second electrical signals at all electrodes in the electrode array 111. This allows more fingerprint detection signals to be generated based on the larger number of second electrical signals, facilitating the extraction of sufficient finger-level features from the generated fingerprint detection signals and improving fingerprint recognition accuracy. As shown in FIG1 or FIG7 , in some optional embodiments, the circuit unit 120 is laminated to the electrode array 111. For example, the electrode array 111 can be directly disposed on the silicon substrate 121 of the circuit unit 120. Furthermore, the common electrode 113 can be laminated to the cover plate 200 via the adhesive layer 300, or the circuit unit 120 can be laminated to the cover plate 200 via the adhesive layer 300. In the embodiment of the present application, after the circuit unit 120 is bonded to the electrode array 111, both the common electrode 113 and the cover plate 200 can be bonded via the adhesive layer 300, and the circuit unit 120 can also be bonded to the cover plate 200 via the adhesive layer 300. This provides a flexible structural arrangement and facilitates integration of the ultrasonic detection device 100 with electronic devices. As shown in FIG2 , in some optional embodiments, if the piezoelectric layer 112 begins transmitting a first ultrasonic signal toward the cover plate 200 at a first time ti, the piezoelectric layer 112 is configured to receive the first ultrasonic reflection signal after a first time Xi has elapsed since the first time (i.e., time t2 in the figure).As a feasible implementation, the value range of the first time Xi can be set based on the abscissa range where the amplitude difference between the dashed waveform and the solid waveform on the R-axis in FIG2 is large. This ensures that there is a significant difference between the first ultrasonic reflection signal received by the piezoelectric layer 112 when a finger touches the surface and when a finger does not touch the surface. In some optional embodiments, the value range of the first time Xi is (1.8T, 3T), meaning that the first time Xi can be set within a range greater than 1.8T and less than 3T. For example, the first time Xi can be set to 1.9T, 2.2T, 2.5T, or 2.8T. T represents the time interval between the piezoelectric layer 112 starting to transmit the ultrasonic signal and the piezoelectric layer 112 starting to receive the target reflection signal. The target reflection signal is the signal generated by the touch surface of the cover plate 200 reflecting the ultrasonic signal. Referring to Figure 1 or Figure 7 , if the piezoelectric layer 112 transmits an ultrasonic signal toward the cover plate 200, the ultrasonic signal will be partially reflected by the interface between the adhesive layer 300 and the cover plate 200 when it propagates to the interface, resulting in a reflected signal that reaches the piezoelectric layer 112 earlier. As the ultrasonic signal continues to propagate from the interface between the wrapping layer 300 and the cover plate 200 to the touch surface of the cover plate 200, it will again be reflected by the touch surface of the cover plate 200, resulting in a reflected signal that reaches the piezoelectric layer 112 later, i.e., the target reflected signal. In this embodiment of the present application, the first time has a value range of (1.8T to 3T), enabling the ultrasonic detection device to generate a touch detection signal based on the first ultrasonic reflection signal formed by the first ultrasonic signal reflected by the touch surface of the cover plate 200. This ensures that the touch detection signal accurately indicates the touch status of the cover plate 200, thereby improving touch detection accuracy. In some optional embodiments, if the piezoelectric layer 112 begins emitting a second ultrasonic signal toward the cover plate 200 at a second moment, the piezoelectric layer 112 is configured to receive a second ultrasonic reflection signal after a second time has elapsed since the second moment; the second time has a different value range than the first time. Embodiments of the present application can perform fingerprint imaging based on fingerprint recognition signals to facilitate fingerprint recognition. The second time's value range can be determined based on the imaging effect of the fingerprint recognition signal corresponding to the second ultrasonic reflection signal. In other words, the first time can be calibrated based on the imaging effect of the fingerprint recognition signal. As a feasible implementation, multiple second times can be set during the continuous process of emitting multiple second ultrasonic signals and generating corresponding fingerprint recognition signals to obtain fingerprint images corresponding to each second time.By superimposing the finger-level images corresponding to each second time, a more complete fingerprint image can be obtained, thereby improving fingerprint recognition accuracy. The difference between multiple second times should not be too large to avoid missing some fingerprint features. The difference between two adjacent second times can be set to be less than or equal to 1 / 4 of the period of the second ultrasonic signal. For example, the difference between two adjacent second times can be set to be 1 / 5 of the period of the second ultrasonic signal, or 1 / 6 of the period of the second ultrasonic signal. In the embodiments of the present application, using a second time with a value range different from that of the first time can free the second time from the restrictions of the first time value range, facilitating the setting of the time for receiving the second ultrasonic reflection signal for fingerprint recognition, thereby ensuring fingerprint recognition accuracy. In some optional embodiments, the second time has a value range of (1.5T, 2T), meaning that the second time can take a value within a range greater than 1.5T and less than 2T. For example, the second time can be set to 1.6T, 1.7T, 1.8T, or 1.9T. In this embodiment of the present application, the second time has a value range of (1.5T, 2T). This allows the ultrasonic detection device to generate a finger-level identification signal based on the second ultrasonic reflection signal formed by the touch surface of the cover plate 200 reflecting the second ultrasonic signal. This ensures that the finger-level identification signal can more clearly indicate the finger-level characteristics of the finger when the cover plate 200 is touched, thereby improving the accuracy of finger-level identification. The following describes the process of using the ultrasonic detection device for touch detection and fingerprint identification using a feasible embodiment. In this embodiment of the present application, the touch screen of the electronic device can serve as the cover plate, and the ultrasonic detection device is located below the touch screen. As shown in Figure 8, when the touch screen is in the off state, the ultrasonic detection device is in touch detection mode, used to detect whether a finger touches the display screen. If a finger touch is detected, the ultrasonic detection device can send a signal indicating the presence of a finger touch to the control unit, waking up the control unit in the ultrasonic detection device that controls its operating mode. Based on the touch notification, the control unit controls the ultrasonic detection device to switch from touch detection mode to fingerprint identification mode. If no finger touch is detected, the ultrasonic detection device remains in touch detection mode. As shown in FIG9 , in touch detection mode, the ultrasonic detection device can continuously transmit a first ultrasonic signal to the touch screen via a piezoelectric transducer and receive the first ultrasonic reflection signal, thereby generating a touch detection signal indicating the touch status of the touch screen. The ultrasonic detection device can be provided with a corresponding detection module that determines the touch status of the touch screen indicated by the touch detection signal, thereby detecting whether a finger touches the touch screen. The principle of determining the touch status of the touch screen indicated by the touch detection signal can be found in the above embodiments and will not be further elaborated here.If a finger touch is detected, the detection module can output a signal indicating the presence of a finger touch. If no finger touch is detected, the piezoelectric transducer can repeat the process of receiving the first ultrasonic reflection signal to continue detecting whether a finger touch is present. In fingerprint recognition mode, the ultrasonic detection device can cause the piezoelectric transducer to transmit a second ultrasonic signal to the touch screen and receive the second ultrasonic reflection signal to generate a fingerprint recognition signal. After generating the fingerprint recognition signal, the CPU in the electronic device can be activated to perform finger-level recognition based on the finger-level recognition signal. The specific process of performing fingerprint recognition based on the fingerprint recognition signal can be referenced in related art and will not be described in detail here. In embodiments of the present application, before performing fingerprint recognition, the ultrasonic detection device can be placed in touch detection mode to detect whether a finger touches the touch screen. Based on the touch detection results, whether to enable fingerprint recognition mode is determined. In touch detection mode, part of the preprocessing circuit in the piezoelectric transducer can be placed in a dormant state, thereby reducing power consumption and avoiding energy waste caused by only enabling the finger-level recognition mode. Embodiments of the present application also provide an electronic device comprising a cover 200 and the ultrasonic detection device 100 of any of the above embodiments. The cover plate 200 provides a touch surface for receiving finger touches. The ultrasonic detection device 100 is disposed beneath the cover plate 200 to detect touches on the cover plate 200. The electronic device provided in the embodiments of this application is based on the same inventive concept as the aforementioned embodiments of the ultrasonic detection device 100 and can achieve the same effects. The specific implementation of the electronic device can be found in the description of the aforementioned embodiments of the ultrasonic detection device 100 and will not be repeated here. In some optional embodiments, the cover plate 200 of the electronic device can be formed of either a conductive material or a non-conductive material. In related art, when using capacitive touch detection devices to detect finger touches, the finger's touch surface is typically required to be non-conductive. Therefore, when used to detect touches on electronic device covers, the electronic device covers are typically made of non-conductive materials. In contrast, in the embodiments of this application, the cover plate 200 of the electronic device can be formed of either a conductive material or a non-conductive material, reducing material restrictions for the cover plate 200 and providing greater freedom in electronic device cover design. It should be noted that, according to implementation needs, the various components / steps described in the embodiments of the present application can be split into more components / steps, or two or more components / steps or partial operations of components / steps can be combined into new components / steps to achieve the purpose of the embodiments of the present application.Those skilled in the art will appreciate that the various exemplary units and method steps described in conjunction with the embodiments disclosed herein can be implemented using electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed using hardware or software depends on the specific application and design constraints of the technical solution. Professionals skilled in the art may use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of the embodiments of this application. The above embodiments are intended only to illustrate the embodiments of this application and are not intended to limit them. Persons skilled in the relevant technical fields may make various changes and modifications without departing from the spirit and scope of the embodiments of this application. Therefore, all equivalent technical solutions are also within the scope of the embodiments of this application, and the scope of patent protection for the embodiments of this application shall be defined by the claims.

Claims

Claims 1. An ultrasonic detection device, characterized in that: The ultrasonic detection device is disposed below a cover of an electronic device and is configured to perform touch detection on the cover. The ultrasonic detection device includes: a piezoelectric transducer and a circuit unit; the piezoelectric transducer is configured to transmit a first ultrasonic signal toward the cover, receive a first ultrasonic reflection signal formed by reflection of the first ultrasonic signal, convert the first ultrasonic reflection signal into a first electrical signal, and input the first electrical signal into the circuit unit; and the circuit unit is configured to generate a touch detection signal indicating a touch status of the cover based on the first electrical signal.

2. The device according to claim 1, characterized in that: The piezoelectric transducer is configured to transmit a second ultrasonic signal toward the cover plate, receive a second ultrasonic reflection signal generated by the second ultrasonic signal, convert the second ultrasonic reflection signal into a second electrical signal, and input the second electrical signal into the circuit unit; the circuit unit is configured to generate a fingerprint recognition signal indicating fingerprint features based on the second electrical signal.

3. The device according to claim 2, characterized in that: The piezoelectric transducer includes an electrode array, a piezoelectric layer, and a common electrode, wherein the common electrode and the electrode array are respectively located on either side of the piezoelectric layer; the common electrode is used to drive the piezoelectric layer to transmit the first ultrasonic signal or the second ultrasonic signal; the piezoelectric layer is used to, upon receiving the first ultrasonic reflection signal, convert the first ultrasonic reflection signal into the first electrical signal acting on the electrode array, and upon receiving the second ultrasonic reflection signal, convert the second ultrasonic reflection signal into the second electrical signal acting on the electrode array; When the piezoelectric layer transmits the first ultrasonic signal or the second ultrasonic signal, the electrode array is grounded; when the piezoelectric layer receives the first ultrasonic reflection signal or the second ultrasonic reflection signal, the common electrode is grounded.

4. The device according to claim 3, characterized in that The electrode array includes a plurality of electrodes; the circuit unit includes a plurality of pre-processing circuits and an output unit; the plurality of pre-processing circuits are all connected to the output unit; and different pre-processing circuits are connected to different electrodes; The preprocessing circuit is used to preprocess the first electrical signal to generate a first preprocessing signal, or to preprocess the second electrical signal to generate a second preprocessing signal; the output unit is used to generate the touch detection signal according to the first preprocessing signal and output the touch detection signal, or to generate the fingerprint recognition signal according to the second preprocessing signal and output the fingerprint recognition signal; when the piezoelectric layer receives the first ultrasonic reflection signal, the preprocessing circuit connected to some of the electrodes included in the electrode array is in an active state, and the preprocessing circuit connected to other electrodes included in the electrode array is in a dormant state; when the piezoelectric layer receives the second ultrasonic reflection signal, the preprocessing circuits connected to all the electrodes included in the electrode array are in an active state.

5. The device according to claim 3, characterized in that The circuit unit is bonded to the electrode array; the common electrode is used to be bonded to the cover plate via an adhesive layer, or the circuit unit is bonded to the cover plate via an adhesive layer.

6. The device according to claim 3, characterized in that If the piezoelectric layer starts transmitting the first ultrasonic signal to the cover at the first moment, the piezoelectric layer is used to receive the first ultrasonic reflection signal after a first time from the first moment, and the value range of the first time is (1.8T, 3T); T is the time interval between when the piezoelectric layer starts to transmit the ultrasonic signal and when the piezoelectric layer starts to receive the target reflection signal. The target reflection signal is a signal formed when the touch surface of the cover reflects the ultrasonic signal.

7. The device according to claim 6, characterized in that If the piezoelectric layer starts to transmit the second ultrasonic signal to the cover plate at a second moment, the piezoelectric layer is configured to receive the second ultrasonic reflection signal after a second time has passed since the second moment; The value range of the second time is different from the value range of the first time.

8. The device according to claim 7, characterized in that The value range of the second time is (1.5T, 2T).

9. An electronic device, characterized in that: include: A cover plate and an ultrasonic detection device according to any one of claims 1 to 8; the cover plate is used to provide a touch surface, and the touch surface is used to receive a touch of a finger; The ultrasonic detection device is disposed below the cover plate and is used to perform touch detection on the cover plate.

10. The electronic device according to claim 9, wherein The cover plate is formed of a conductive material or a non-conductive material.

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