Proximity detection device

Abstract

To provide a proximity detection device with a detection distance for detecting an object separated to some extent from an operation surface.SOLUTION: A proximity detection device includes: a proximity detection unit that has a piezoelectric body and first and second electrodes disposed in contact with the piezoelectric body to detect proximity of an object; a signal applying unit that causes the proximity detection unit to perform capacitance detection and ultrasonic transmission and / or ultrasonic reception by applying a plurality of signals of different frequencies to at least one of the first and second electrodes; and a charge measurement unit connected to at least one of the first and second electrodes to measure electric charge.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a proximity detection device. [Background technology]

[0002] Conventionally, there has been a touch panel with a pressure detection function that includes a sensor unit that includes an electrostatic sensor and a piezoelectric sensor that is laminated on the back surface of the electrostatic sensor or that shares some of the constituent layers with the electrostatic sensor; a capacitance detection circuit that is connected to the electrostatic sensor in the sensor unit and that detects the presence or absence of a touch and the touch position from a change in electrostatic capacitance and sends an electrical signal to a host; a charge amplifier that is connected to the piezoelectric sensor in the sensor unit and that converts the charge signal into a voltage signal; a sample and hold circuit that is connected to the charge amplifier and that sends the output of the charge amplifier when the capacitance detection circuit deactivates the electrostatic sensor and that holds and sends the output of the charge amplifier immediately before the capacitance detection circuit changes from deactivating to activating the electrostatic sensor; and an AD converter that is connected to the sample and hold circuit and that digitally converts the output of the sample and hold circuit and sends it to the host (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-194791 Summary of the Invention [Problem to be solved by the invention]

[0004] However, while a touch panel with a pressure detection function can detect the presence or absence of a touch on the touch surface and the touch position, it cannot detect an object such as a hand that is some distance away from the touch surface. In other words, the distance at which an object can be detected in the direction away from the operation surface such as the touch surface is limited.

[0005] Therefore, an object of the present invention is to provide a proximity detector having a detection distance that allows detection of an object that is some distance away from the operation surface. [Means for solving the problem]

[0006] A proximity detection device according to an embodiment of the present invention is characterized by comprising: a proximity detection unit having a piezoelectric body, a first electrode and a second electrode arranged to contact the piezoelectric body and detecting the proximity of an object; a signal application unit that applies signals of multiple different frequencies to at least one of the first electrode and the second electrode to cause the proximity detection unit to detect capacitance and transmit and / or receive ultrasonic waves; and a charge measurement unit that is connected to at least one of the first electrode and the second electrode and measures electric charge. [Effects of the Invention]

[0007] It is possible to provide a proximity detector having a detection distance that allows detection of an object that is some distance away from the operation surface. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating an example of a proximity detection device 100 according to an embodiment. [Figure 2] 2 is a diagram showing an example of the configuration of a cross section taken along the arrow AA in FIG. 1. FIG. [Figure 3] FIG. 10 is a flowchart illustrating an example of processing executed by an MPU 150. [Figure 4A] FIG. 10 is a diagram showing a modified example of an intersection 110A. [Figure 4B] FIG. 10 is a diagram showing a modified example of an intersection 110A. [Figure 4C] FIG. 10 is a diagram showing a modified example of an intersection 110A. [Figure 4D] FIG. 10 is a diagram showing a modified example of an intersection 110A. [Figure 5A] FIG. 10 is a diagram showing a modified example of an intersection 110A. [Figure 5B] FIG. 10 is a diagram showing a modified example of an intersection 110A. [Figure 5C]FIG. 10 is a diagram showing a modified example of an intersection 110A. [Figure 5D] FIG. 10 is a diagram showing a modified example of an intersection 110A. [Figure 6A] FIG. 10 is a diagram showing a modified example of an intersection 110A. [Figure 6B] FIG. 10 is a diagram showing a modified example of an intersection 110A. [Figure 7A] FIG. 10 is a diagram showing a modified example of an intersection 110A. [Figure 7B] FIG. 10 is a diagram showing a modified example of an intersection 110A. [Figure 7C] FIG. 10 is a diagram showing a modified example of an intersection 110A. [Figure 8] FIG. 10 is a diagram illustrating an example of a proximity detection device 100M according to a modified example of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment to which the proximity detection device of the present invention is applied will be described.

[0010] <Embodiment> FIG. 1 is a diagram illustrating an example of a proximity detection device 100 according to an embodiment. FIG. 2 is a diagram illustrating an example of the configuration of a cross section taken along the line AA in FIG. 1. In the following description, an XYZ coordinate system is defined. The direction parallel to the X axis (X direction), the direction parallel to the Y axis (Y direction), and the direction parallel to the Z axis (Z direction) are perpendicular to one another. For ease of explanation, the −Z direction may be referred to as the lower side or bottom, and the +Z direction may be referred to as the upper side or top, but this does not represent a universal vertical relationship. A planar view refers to a view from the XY plane. In the following description, the length, width, thickness, etc. of each part may be exaggerated to make the configuration easier to understand.

[0011] The proximity detection device 100 includes a proximity detection unit 110, a MUX (multiplexer) 120, a transmission circuit 130, a reception circuit 140, a timer 145, and an MPU (micro processing unit) 150. The MUX 120, the transmission circuit 130, and the MPU 150 are examples of a signal application unit. The signal application unit applies signals of a plurality of different frequencies to at least one of the first electrode 111 and the second electrode 112, causing the proximity detection unit 110 to perform capacitance detection and ultrasonic wave transmission and / or ultrasonic wave reception.

[0012] The proximity detection device 100 has an operation surface 100A. The operation surface 100A is a surface that serves as a reference surface when the proximity detection device 100 detects the proximity of an object, and is, for example, the surface of a panel such as a housing of an electronic device that includes the proximity detection device 100. The electronic device may be, for example, any electronic device that includes a touch panel, and examples include a smartphone or a tablet computer. The proximity detection unit 110 is located on the back side of the operation surface 100A, and the operation surface 100A is located on the front side of the proximity detection unit 110. Here, a case will be described in which the object is the hand of a user of the electronic device that includes the proximity detection device 100.

[0013] The proximity detection device 100 detects the proximity of a user's hand to the operation surface 100A. Here, proximity refers to the hand approaching the operation surface 100A without touching it, or the hand touching the operation surface 100A.

[0014] The proximity detection device 100 detects the amount of charge corresponding to the capacitance between the hand and the proximity detection unit 110, and calculates the position of the target hand by performing profile and image detection based on the amount of charge. Calculating the position of the hand based on capacitance means being able to calculate the position of the hand when it is in contact with (touching) the operation surface 100A and the position of the hand when it is not in contact with the operation surface 100A but is very close to it. The position of the hand calculated based on capacitance can be expressed three-dimensionally.

[0015] Furthermore, the proximity detection device 100 transmits ultrasonic waves from multiple points on the proximity detection unit 110 toward the hand, and calculates the distances from the operation surface 100A to multiple points on the hand based on the round-trip time it takes for the reflected waves to be received. That is, the proximity detection unit 110 transmits ultrasonic waves and then receives the reflected waves. The proximity detection device 100 can further calculate the distribution of hand positions from the calculated distances.

[0016] The range in which a change in capacitance due to the proximity of a hand can be detected is limited in the direction away from the operation surface 100A. Furthermore, calculating the position of the hand based on the round-trip time of ultrasonic waves has the drawback of being difficult when the hand is too close to the operation surface 100A. Therefore, the proximity detection device 100 calculates the distance to the hand using ultrasonic waves when the distance from the operation surface 100A to the hand is longer than a predetermined distance, and calculates the distance to the hand using capacitance when the distance from the operation surface 100A to the hand is equal to or shorter than the predetermined distance. To determine whether the distance from the operation surface 100A to the hand is longer than the predetermined distance, for example, multiple distances from the operation surface 100A to multiple points on the hand are calculated based on the round-trip time of ultrasonic waves, and the determination is made based on whether the average of the multiple distances is longer than the predetermined distance. For example, the predetermined distance is between 3 cm and 10 cm. Alternatively, instead of the average of the multiple distances, the determination may be made based on whether the minimum value of the multiple distances is longer than the predetermined distance, or whether the distance at a certain point is longer than the predetermined distance.

[0017] Furthermore, when a user's hand approaches the operation surface 100A, the proximity detection device 100 can calculate a two-dimensional profile representing the two-dimensional distribution of the hand shape or a three-dimensional image representing the three-dimensional distribution of the hand shape. Such a two-dimensional profile or three-dimensional image of the hand shape can be obtained based on the distances from the operation surface 100A to multiple points on the hand, which can be calculated based on the round-trip time between transmitting ultrasonic waves from multiple points on the proximity detection unit 110 and receiving reflected waves.

[0018] The two-dimensional hand shape profile represents a two-dimensional distribution of hand positions determined from the distribution of distances in the Z direction from operation surface 100A to multiple hand positions on the XZ plane at a certain Y coordinate or on the YZ plane at a certain X coordinate. Also, the three-dimensional hand shape image represents a three-dimensional distribution of hand positions determined from the distribution of distances in the Z direction from operation surface 100A to multiple hand positions.

[0019] Furthermore, the proximity detection device 100 uses a common detection unit to detect the distance to the hand using ultrasound and to detect the position of the hand using capacitance, and uses a MUX 120, a transmission circuit 130, a reception circuit 140, a timer 145, and an MPU 150 as the common detection unit.

[0020] <Proximity detection unit 110> The proximity detection unit 110 has a piezoelectric body and a first electrode and a second electrode provided to be in contact with the piezoelectric body, and detects the proximity of an object. Note that the piezoelectric body in this application refers to a substance having piezoelectricity, and for example, an electret having piezoelectricity is also included in the piezoelectric body. In this embodiment, the proximity detection unit 110 has a first electrode 111, a second electrode 112, a piezoelectric body 113, and a substrate 114, and detects the proximity of an object, that is, a hand. The first electrode 111 is a linear electrode (electrode wire) extending in the X direction, and multiple first electrodes 111 are arranged at equal intervals in the Y direction. The X direction is an example of a first direction, and the Y direction is an example of a second direction. The second electrode 112 is a linear electrode (electrode wire) extending in the Y direction, and multiple second electrodes 112 are arranged at equal intervals in the X direction. The first electrode 111 and the second electrode 112 intersect in a plan view with a gap in the Z direction, and at an intersection 110A where they intersect in a plan view, a piezoelectric body 113 is provided between the first electrode 111 and the second electrode 112. In other words, the first electrode 111 and the second electrode 112 are provided so as to be in contact with the piezoelectric body 113, and the first electrode 111 and the second electrode 112 are configured so as to sandwich the piezoelectric body 113 therebetween.

[0021] The first electrode 111 and the second electrode 112 are used to detect both the distance to the hand using ultrasound and the position of the hand using capacitance. The piezoelectric element 113 is used to detect the distance to the hand using ultrasound. In other words, the proximity detector 110 also has the function of detecting ultrasound, as the electrodes for capacitance detection double as the electrodes for the piezoelectric element.

[0022] Intersections 110A where first electrodes 111 and second electrodes 112 intersect in a plan view are arranged in a matrix pattern as shown in Fig. 1. Since substrates 114 are provided above first electrodes 111 and below second electrodes 112, the cross-sectional configuration of intersections 110A has a structure in which substrate 114, second electrodes 112, piezoelectric bodies 113, first electrodes 111, and substrate 114 are layered from bottom to top as shown in Fig. 2.

[0023] The first electrode 111 and the second electrode 112 may be linear electrodes made of a metal such as copper or aluminum. For example, a substrate 114 having a plurality of first electrodes 111 formed on one surface and a substrate 114 having a plurality of second electrodes 112 formed on the other surface may be prepared, and the two substrates 114 may be bonded together with a piezoelectric body 113 sandwiched between them at an intersection 110A, thereby producing the proximity detector 110. At the intersection 110A, the piezoelectric body 113 is disposed between the first electrode 111 and the second electrode 112, but the first electrode 111 and the second electrode 112 may be insulated from each other by an insulating layer or the like outside the intersection 110A.

[0024] The piezoelectric bodies 113 are provided to generate ultrasonic vibrations. Ultrasonic waves are used because they can easily measure the distance to a hand located directly above each piezoelectric body 113 by emitting highly directional ultrasonic waves directly above (in the +Z direction) each piezoelectric body 113. As the piezoelectric body 113, for example, an element that generates distortion when a voltage is applied, such as a piezoelectric element, can be used. At the intersection 110A, a first electrode 111 and a second electrode 112 are provided above and below the piezoelectric body 113. Therefore, by applying an ultrasonic AC signal between the first electrode 111 and the second electrode 112, the piezoelectric body 113 can be resonated, and ultrasonic waves can be transmitted directly above the piezoelectric body 113.

[0025] The AC signal for ultrasonic waves is an example of a second frequency signal for transmitting ultrasonic waves, and may have any frequency that can resonate the piezoelectric body 113 arranged between the first electrode 111 and the second electrode 112. The frequency of the AC signal for ultrasonic waves is, for example, several tens of kHz to several hundreds of kHz, and the piezoelectric body 113 vibrates at a frequency equal to the frequency of the AC signal. By applying the AC signal for ultrasonic waves between the first electrode 111 and the second electrode 112, the piezoelectric body 113 can be resonated to generate ultrasonic waves of a desired frequency.

[0026] An electret having piezoelectricity may be used instead of the piezoelectric body 113. In this case, the electret can generate ultrasonic waves in the same way as the piezoelectric body 113 by sandwiching it between the first electrode 111 and the second electrode 112 and applying an AC signal for ultrasonic waves.

[0027] The substrate 114 may be a flexible or rigid wiring substrate, an insulating sheet, or the like. The proximity detection unit 110 may be transparent to visible light. In this case, the first electrode 111 and the second electrode 112 may be made of a transparent conductive material such as ITO (Indium Tin Oxide), a transparent piezoelectric body 113 may be used, and the two substrates 114 may be transparent substrates.

[0028] <mux120> The MUX 120 is connected to the first electrode 111 and the second electrode 112 via wiring, and is also connected to the transmitting circuit 130 and the receiving circuit 140. The MUX 120 selects one or more first electrodes 111 from the plurality of first electrodes 111, and selects one or more second electrodes 112 from the plurality of second electrodes 112, thereby switching the first electrodes 111 and second electrodes 112 connected to the transmitting circuit 130 and the receiving circuit 140 in a time series manner. The switching of the selection of the first electrodes 111 and the second electrodes 112 by the MUX 120 is performed by the MPU 150.

[0029] <Transmitting circuit 130> When detecting the distance to the hand using ultrasound, the transmission circuit 130 is controlled by the MPU 150 to output an ultrasonic AC signal between each of the first electrodes 111 and each of the second electrodes 112 via the MUX 120, and also outputs an AC signal to the timer 145. When detecting a position using capacitance, the transmission circuit 130 is controlled by the MPU 150 to output an AC signal of a frequency for capacitance detection to either of the first electrodes 111 or each of the second electrodes 112 via the MUX 120. Since detection of the distance to the hand using ultrasound and position detection using capacitance are performed separately, for example, in a time-division manner, the transmission circuit 130 selectively applies the AC signal for ultrasound or the AC signal of a frequency for capacitance detection to either of the first electrodes 111 or each of the second electrodes 112.

[0030] The AC signal with a frequency for detecting capacitance is an example of a first frequency signal for detecting capacitance, and the AC signal for ultrasonic waves is an example of a second frequency signal for transmitting ultrasonic waves. The frequency of the AC signal with a frequency for detecting capacitance may be, for example, several tens of kHz to several hundreds of kHz, similar to the AC signal for ultrasonic waves, as long as it is deviated from the resonance frequency of the piezoelectric body 113. This is to prevent the piezoelectric body 113 from resonating when position detection based on capacitance is performed.

[0031] <Receiving circuit 140> The charge measurement unit is connected to at least one of the first electrode 111 and the second electrode 112 and measures the charge. In this embodiment, the receiving circuit 140 corresponds to the charge measurement unit. When detecting the distance to the hand using ultrasound, the receiving circuit 140 is controlled by the MPU 150 to acquire waveforms generated by the charges of the first electrodes 111 and the second electrodes 112 via the MUX 120 and output the waveforms to the timer 145. When detecting the position using capacitance, the receiving circuit 140 is controlled by the MPU 150 to detect the amount of charge corresponding to the capacitance of the first electrodes 111 and the second electrodes 112 via the MUX 120 and output the amount of charge to the MPU 150.

[0032] <Timer 145> When detecting the distance to the hand using ultrasonic waves, timer 145 is controlled by MPU 150 to measure the time difference between the waveform of the AC signal input from transmission circuit 130 and the waveform input from reception circuit 140 for each first electrode 111 and each second electrode 112 as the round-trip time of the ultrasonic waves. Timer 145 outputs the round-trip time measured for each first electrode 111 and each second electrode 112 to MPU 150.

[0033] <mpu150> The MPU 150 has a main control unit 151, a calculation unit 152, and a memory 153. The MPU 150 is realized by a computer including a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), an input / output interface, an internal bus, etc. The main control unit 151 and the calculation unit 152 are functional blocks representing the functions of a program executed by the MPU 150. The memory 153 is a functional representation of the memory of the MPU 150.

[0034] The main control unit 151 is a processing unit that controls the processing of the MPU 150, and executes processing other than the processing executed by the calculation unit 152, for example.

[0035] The calculation unit 152 calculates the distance between the target (e.g., a hand) and the proximity detection unit 110. The MPU 150 switches the selection of the first electrode 111 and the second electrode 112 by the MUX 120 between detecting the distance to the hand using ultrasonic waves and detecting the position using capacitance. Since the MPU 150 is connected to the first electrode 111 and the second electrode 112 selected by the MUX 120, the calculation unit 152 is connected to the first electrode 111 and the second electrode 112 selected by the MUX 120 via the transmission circuit 130 or the reception circuit 140.

[0036] The signal application unit selectively applies a first frequency signal for capacitance detection and a second frequency signal for ultrasonic wave transmission. The calculation unit 152 obtains a result of capacitance detection and / or ultrasonic wave detection based on the signal selected by the signal application unit and the charge measured by the receiving circuit 140 (charge measurement unit), and calculates the distance between the object and the proximity detection unit 110 based on the obtained result. Specifically, when the signal application unit selects the first frequency signal, the calculation unit 152 obtains a result of capacitance detection based on the amount of charge measured by the receiving circuit 140, and calculates the distance between the object and the proximity detection unit 110 based on the obtained result. Furthermore, when the signal application unit selects the second frequency signal, the calculation unit 152 calculates the distance between the object and the proximity detection unit 110 based on the time from ultrasonic wave transmission to ultrasonic wave reception based on the charge measured by the receiving circuit 140. In other words, the calculation unit 152 can be said to be a common calculation unit that can determine the results of both capacitance detection and ultrasonic detection using the amount of charge of the first electrode 111 and / or the second electrode 112 measured by the charge measurement unit (receiving circuit 140).

[0037] Furthermore, the signal application unit selects the second frequency signal to cause the proximity detection unit 110 to transmit and / or receive ultrasonic waves, and when the distance between the object and the proximity detection unit 110 calculated by the calculation unit 152 becomes equal to or shorter than a predetermined distance, selects the first frequency signal to cause the proximity detection unit 110 to detect capacitance. Specifically, as an example, the MPU 150 controls the transmission circuit 130 to output an ultrasonic AC signal between each of the first electrodes 111 and each of the second electrodes 112 while chronologically switching the selection of the first electrodes 111 and the second electrodes 112 by the MUX 120, and acquires a round-trip time from the timer 145. Then, the calculation unit 152 calculates the distance from the operation surface 100A directly above each intersection 110A to each part of the hand, and when, for example, the average value of all the distances is longer than a predetermined distance, the signal application unit causes the proximity detection unit 110 to transmit and receive ultrasonic waves, thereby calculating the distance to the hand using ultrasonic waves. Furthermore, when the average value of all distances is equal to or less than the predetermined distance, the signal application unit causes the proximity detection unit 110 to detect capacitance, thereby calculating the position of the object based on capacitance. Note that it is not necessarily necessary to make the determination based on the average value of all distances; the determination may be based on the minimum value of all distances, or it may be determined whether the distance is equal to or less than the predetermined distance based on the distance between the object and the proximity detection unit 110 at a certain point. Furthermore, in this embodiment, the timer 145 is provided separately from the MPU 150, but the MPU 150 itself may have a function of measuring time, in which case the timer 145 is not necessary.

[0038] When detecting the distance to the hand using ultrasound, the MPU 150 switches the selection of the first electrode 111 and the second electrode 112 by the MUX 120 in a time-series manner, controls the transmitting circuit 130 to output an ultrasonic AC signal between each of the first electrodes 111 and each of the second electrodes 112, and causes the receiving circuit 140 to acquire the waveform generated by the electric charge, thereby acquiring the round-trip time from the timer 145.

[0039] The calculation unit 152 calculates the distance from the operation surface 100A to the point where the ultrasonic wave is reflected, based on the round-trip time and the speed of sound. The point where the ultrasonic wave is reflected is the part of the hand located directly above the piezoelectric body 113 at the intersection 110A of the first electrode 111 and the second electrode 112 selected by the MUX 120.

[0040] Furthermore, the calculation unit 152 may further detect a two-dimensional profile of the hand shape or a three-dimensional image of the hand shape based on the calculated distance. Specifically, the calculation unit 152 detects a two-dimensional profile or a three-dimensional image of the hand, which is the target object, based on the amount of charge measured by the receiving circuit 140 (charge measurement unit) and / or the time from ultrasonic wave transmission to ultrasonic wave reception. By detecting the two-dimensional profile or the three-dimensional image, the shape of the hand can be determined and the movement of the user's hand can be detected.

[0041] When performing position detection using capacitance, the MPU 150 switches the selection of the first electrode 111 and the second electrode 112 by the MUX 120 in a time-series manner, controls the transmitting circuit 130 to output an AC signal of a frequency for capacitance detection between each first electrode 111 and each second electrode 112, and controls the receiving circuit 140 to detect the capacitance obtained from the charge between each first electrode 111 and each second electrode 112.

[0042] Note that changing the detection method depending on whether the distance is equal to or greater than a predetermined distance is just one example, and MPU 150 may alternate between detecting the distance to the hand using ultrasonic waves and detecting the position using capacitance in a time-division manner. In this case, the signal application unit switches between the first frequency signal and the second frequency signal in a time-division manner. By executing two types of detection methods in a time-division manner, it is possible to always detect the distance to the hand using ultrasonic waves and detect the position of the hand using capacitance, regardless of the distance from operation surface 100A to the hand.

[0043] The memory 153 stores programs, data necessary for the main control unit 151 and the calculation unit 152 to perform the above-described processes, the round-trip time input from the timer 145 to the MPU 150, the distance calculated by the calculation unit 152, the capacitance, data representing the two-dimensional profile or three-dimensional image of the hand shape, and the like.

[0044] <Processes executed by the MPU 150> FIG. 3 is a diagram showing a flowchart representing an example of the processes executed by the MPU 150.

[0045] When the calculation unit 152 starts the process, it calculates the distance to the hand by ultrasonic waves (step S1). The calculation unit 152 calculates the distance from the operation surface 100A directly above each intersection 110A to each part of the hand. The process of step S1 is executed to determine whether to perform detection of the distance to the hand by ultrasonic waves or position detection by capacitance.

[0046] The MPU 150 determines whether the average value of all the distances is longer than a predetermined distance (step S2).

[0047] When the MPU 150 determines that the average value of all the distances is longer than the predetermined distance (S2: YES), it detects the distance to the hand by ultrasonic waves (step S3). This is because the position of the hand is too far to be detected by capacitance, and thus it is calculated based on the round-trip time of ultrasonic waves. Note that the details of the detection of the distance to the hand by ultrasonic waves have been described above, and thus are omitted here.

[0048] The calculation unit 152 detects the two-dimensional profile or three-dimensional image of the hand shape based on the distance obtained in step S2 (step S4). Thereby, the two-dimensional profile or three-dimensional image of the hand approaching the operation surface 100A is obtained.

[0049] After completing the process of step S4, the MPU 150 determines whether to end the series of processes (step S5). The MPU 150 determines in step S5 that the series of processes is to end when, for example, the power of the electronic device incorporating the proximity detection device 100 is turned off.

[0050] If the MPU 150 determines that the series of processes is not to be completed (S5: NO), the flow returns to step S1 in order to continue the process depending on the subsequent hand position.

[0051] Furthermore, if the MPU 150 determines in step S2 that the average value of all distances is not longer than the predetermined distance (S2: NO), it performs position detection using capacitance (step S6). This is because the hand position is too close to be determined using the round-trip time of ultrasonic waves, and is instead determined using capacitance. After completing the processing of step S6, the MPU 150 advances the flow to step S5.

[0052] As described above, proximity detection device 100 provides piezoelectric body 113 at intersection 110A between first electrode 111 and second electrode 112, and when the position of the hand is within a predetermined distance, detects the position using capacitance obtained from the charges of first electrode 111 and second electrode 112, and when the position of the hand is longer than the predetermined distance, calculates the distance to the hand based on the round-trip time of ultrasonic waves transmitted by driving piezoelectric body 113. Detection of the distance to the hand using ultrasonic waves makes it possible to detect distances farther than can be achieved by position detection using capacitance.

[0053] Therefore, it is possible to provide a proximity detector 100 having a detection distance that allows detection of an object that is at a certain distance from the operation surface 100A.

[0054] The proximity detection device 100 also uses a common detection unit for detecting the distance to the hand using ultrasound and detecting the hand position using capacitance. The common detection unit includes the MUX 120, the transmission circuit 130, the reception circuit 140, the timer 145, and the MPU 150. In particular, the reception circuit 140 functions as a charge measurement unit, enabling charge detection, which is required for both capacitance detection and ultrasound detection, to be performed in a single configuration. This allows the detection of the distance to the hand using ultrasound and the detection of the hand position using capacitance to be performed using the same circuit, making it possible to determine the hand position near the operation surface 100A based on capacitance and the hand position at a certain distance from the operation surface 100A using ultrasound, with a simple configuration. Furthermore, by using the same detection unit to detect the distance to the hand using ultrasound and the hand position using capacitance, the detection accuracy of the two different detection methods can be matched. This solves the problem of the device configuration becoming complex and large when the detection of the distance to the hand using ultrasound and the detection of the hand position using capacitance are performed using separate detection units.

[0055] Furthermore, since the proximity detection unit 110 is configured such that the first electrode 111 and the second electrode 112 sandwich the piezoelectric body 113 therebetween, an AC signal can be easily applied to the piezoelectric body 113 using the first electrode 111 and the second electrode 112 for capacitance detection. The proximity detection unit 110 may also be configured such that the first electrode 111 and the second electrode 112 sandwich an electret having piezoelectricity therebetween. Furthermore, since the MUX 120, the transmission circuit 130, the reception circuit 140, and the MPU 150 connected to the first electrode 111 and the second electrode 112 are used for capacitance detection, the proximity detection device 100 capable of ultrasonic detection can be realized simply by adding the timer 145 and modifying the program executed by the MPU 150. This is a solution to the problem that the device configuration becomes complex and large when the detection of the distance to the hand using ultrasonic waves and the detection of the hand position using capacitance are performed using separate proximity detection units.

[0056] Furthermore, since the proximity detection unit 110 transmits ultrasonic waves and then receives them using reflected waves, there is no need to provide separate proximity detection units for transmission and reception; a single proximity detection unit 110 can transmit and receive ultrasonic waves, enabling transmission and reception of ultrasonic waves to be achieved with a simple configuration.

[0057] The signal application unit selectively applies a first frequency signal for capacitance detection and a second frequency signal for ultrasonic wave transmission. In this embodiment, the MPU 150, MUX 120, and transmission circuit 130, which correspond to the signal application unit, selectively apply an AC signal for capacitance detection and an AC signal for ultrasonic wave transmission. The calculation unit 152 obtains the results of capacitance detection and / or ultrasonic wave detection based on the signal selected by the signal application unit (MPU 150, MUX 120, and transmission circuit 130) and the measured charge, and calculates the distance between the hand, which is the target object, and the proximity detection unit 110 based on the obtained results. Therefore, a simple configuration can be realized in which one MUX 120, one transmission circuit 130, and one reception circuit 140 can be used for both capacitance detection and ultrasonic wave detection.

[0058] In addition, the signal application unit (MPU 150, MUX 120 and transmission circuit 130) selects an AC signal for ultrasonic transmission and causes the proximity detection unit 110 to transmit and receive ultrasonic waves, and when the distance between the object and the proximity detection unit 110 calculated by the calculation unit 152 becomes less than a predetermined distance, it selects an AC signal for capacitance detection and causes the proximity detection unit 110 to perform capacitance detection, thereby realizing a simple configuration in which one proximity detection unit 110, one MUX 120, one transmission circuit 130 and one reception circuit 140 can be used for both capacitance detection and ultrasonic detection.

[0059] The device further includes a timer 145 that measures the time (round trip time) from when the transmitting circuit 130 applies the second frequency signal until the electric charge based on the AC signal for transmitting ultrasonic waves reflected by the object is measured by the receiving circuit 140, and the calculation unit 152 calculates the distance between the object and the proximity detection unit 110 based on the time measured by the timer 145, so that the distance to the object, which is the hand, can be easily detected based on the round trip time of the ultrasonic waves.

[0060] In addition, the transmission circuit 130 and the reception circuit 140 can also switch between an AC signal for capacitance detection and an AC signal for ultrasonic detection by time division, thereby realizing a simple configuration in which one transmission circuit 130 and one reception circuit 140 can be used for both capacitance detection and ultrasonic detection by time division.

[0061] As described above, the proximity detection unit 110 is only required to include one piezoelectric element 113, and one first electrode 111 and one second electrode 112 provided to be in contact with the piezoelectric element 113, and therefore does not necessarily require a plurality of first electrodes 111 and a plurality of second electrodes 112 as shown in Fig. 1. However, since distance data at a plurality of points is required to detect a two-dimensional profile or a three-dimensional image of an object, the proximity detection unit 110 may include a plurality of first electrodes 111 and a plurality of second electrodes 112 as shown in Fig. 1. In this case, the device includes a plurality of first electrodes 111, one or more piezoelectric bodies 113, and a plurality of second electrodes 112, and each of the one or more piezoelectric bodies 113 is provided between at least one of the plurality of first electrodes 111 and at least one of the plurality of second electrodes 112, so that the distance to the hand, which is the object, can be measured by transmitting and receiving ultrasonic waves between the one or more piezoelectric bodies 113 provided between the plurality of first electrodes 111 and the plurality of second electrodes 112. Here, the case where there is one piezoelectric body 113 refers to the case where, for example, a sheet layer of piezoelectric body 113 is provided over the entire surface between the layer on which first electrode 111 is provided and the layer on which second electrode 112 is provided.

[0062] The first electrodes 111 extend in the X direction and are arranged in a plurality of rows in the Y direction intersecting the X direction. The second electrodes 112 extend in the Y direction and are arranged in a plurality of rows in the X direction. The piezoelectric bodies 113 are sandwiched between the first electrodes 111 and the second electrodes 112 at intersections 110A where the first electrodes 111 and the second electrodes 112 intersect. Therefore, by utilizing the first electrodes 111 and the second electrodes 112 for capacitance detection, it is possible to easily apply an AC signal for transmitting ultrasonic waves to the piezoelectric bodies 113 and easily detect reflected waves. Note that capacitance detection may be performed by self-capacitance detection or mutual capacitance detection. Furthermore, the first electrodes 111 and the second electrodes 112 do not necessarily need to intersect. For example, a configuration in which a large number of first electrodes 111 and second electrodes 112, each sandwiching a piezoelectric body 113 therebetween, are arranged on a plane may be used.

[0063] Furthermore, since the calculation unit 152 detects a two-dimensional profile or three-dimensional image of the object based on the measured amount of charge, it is possible to provide a proximity detection device 100 that can easily grasp the shape and movement of a hand, which is an object near the operation surface 100A. That is, the proximity detection device 100 uses both capacitance detection and ultrasonic detection to perform detailed image detection of the object, and by performing capacitance detection in an area close to the touch and ultrasonic detection in an area somewhat further away, it is possible to detect the object over a wide range of distances.

[0064] Although the above describes a configuration in which the proximity detection unit 110 has a plurality of first electrodes 111, a plurality of second electrodes 112, and one or more piezoelectric bodies 113, the proximity detection unit 110 may have, as a minimum configuration, one first electrode 111, one second electrode 112, and one piezoelectric body 113. The number of first electrodes 111 and the number of second electrodes 112 do not have to be equal.

[0065] Furthermore, although the above describes a configuration in which a piezoelectric body 113 is provided at each of the intersections 110A between the plurality of first electrodes 111 and the plurality of second electrodes 112, the intersections 110A at which the piezoelectric body 113 is provided may be a portion of all the intersections 110A. For example, the piezoelectric body 113 may be provided at every other intersection 110A in the X direction and / or Y direction. The number of piezoelectric bodies 113 is related to the detection of the hand position in ultrasonic detection, the resolution of the two-dimensional profile, and the three-dimensional image, and may therefore be set appropriately depending on the application of the proximity detection device 100, etc.

[0066] That is, each of the one or more piezoelectric bodies 113 may be provided between at least one of the plurality of first electrodes 111 and at least one of the plurality of second electrodes 112.

[0067] <Modification of Intersection 110A> 4A to 7C are diagrams showing modified examples of the intersection 110A. 4A to 7C show a configuration corresponding to a cross section (a cross section taken along the line AA in FIG. 1) corresponding to the cross section of the intersection 110A shown in FIG. 2. The intersection 110A shown in FIG. 2 may be modified to have any of the configurations shown in FIGS. 4A to 7C.

[0068] Intersection 110A in Fig. 4A has first electrode 111, second electrode 112, piezoelectric body 113, and substrate 114. Intersection 110A in Fig. 4A has a configuration in which substrate 114, which is the uppermost part of intersection 110A shown in Fig. 2, is omitted. For example, piezoelectric body 113 and first electrode 111 may be provided overlapping one another on substrate 114 having second electrode 112 formed on one surface thereof.

[0069] Intersection 110A in FIG. 4B has first electrode 111, second electrode 112, piezoelectric body 113, and two substrates 114, and has a configuration in which piezoelectric body 113 in intersection 110A shown in FIG. 2 is made thinner.

[0070] Intersection 110A in FIG. 4C has first electrode 111, second electrode 112, piezoelectric body 113, and two substrates 114, and has a configuration in which first electrode 111 and second electrode 112 of intersection 110A shown in FIG. 2 are made thinner.

[0071] Intersection 110A in FIG. 4D has first electrode 111, second electrode 112, piezoelectric body 113, and two substrates 114, and has a configuration in which piezoelectric body 113 of intersection 110A shown in FIG. 2 is divided into two.

[0072] Intersection 110A in Fig. 5A has first electrode 111, second electrode 112, piezoelectric body 113, and two substrates 114, and the cross section shown in Fig. 5A has a configuration in which first electrode 111 of intersection 110A shown in Fig. 2 is divided into two. First electrode 111 may be divided into two, or, for example, first electrode 111 may have a spiral shape in a plan view.

[0073] Intersection 110A in FIG. 5B has first electrode 111, second electrode 112, piezoelectric body 113, and two substrates 114, and has a configuration in which piezoelectric body 113 shown in FIG. 5A is divided into two.

[0074] 5C includes a first electrode 111, a second electrode 112, a piezoelectric body 113, two substrates 114, and a shield electrode 115. The shield electrode 115 is an example of a third electrode for shielding. In the intersection 110A shown in FIG. 5C, the second electrode 112 is disposed on the piezoelectric body 113 together with the first electrode 111, the shield electrode 115 is formed on the lower substrate 114, and the piezoelectric body 113 is disposed on the shield electrode 115. The shield electrode 115 is provided on the opposite side of the first electrode 111 and the second electrode 112 from the side on which the operation surface 100A, which is approached by a hand as an object, is located.

[0075] The first electrode 111 and the second electrode 112 are electrodes patterned into a diamond shape in plan view, and in FIG. 5C, the bridge portion where the first electrode 111 and the second electrode 112 straddle each other is omitted.

[0076] The shield electrode 115 is provided to shield the first electrode 111 and the second electrode 112 on the operation surface 100A from noise and to suppress parasitic capacitance with the ground. An AC voltage may be applied to the shield electrode 115, or the shield electrode 115 may be connected to the ground. When an AC voltage is applied, the signal application unit applies a third frequency signal to the third electrode (shield electrode 115). When performing capacitance detection, the signal application unit can make the frequency of the third frequency signal the same as the frequency of the first frequency signal, thereby allowing the shield electrode 115 to function as an active shield. For example, the shield electrode 115 is formed of a metal foil made of copper or aluminum, or a conductive film made of a transparent conductive material such as an ITO film. The shield electrode 115 is a single electrode provided over the entire proximity detection unit 110 in a plan view. An AC voltage is applied to the shield electrode 115 when detecting the position of a hand using capacitance.

[0077] 5D has a configuration in which the piezoelectric body 113 of the intersection 110A shown in FIG. 5C is divided into a first electrode 111 and a second electrode 112. For example, the first electrode 111 may transmit an ultrasonic wave, and the second electrode 112 may receive the ultrasonic wave.

[0078] The intersection 110A shown in Fig. 6A has a configuration in which the piezoelectric body 113 below the second electrode 112 is removed from the intersection 110A shown in Fig. 5D. The intersection 110A shown in Fig. 6B has a configuration in which the first electrode 111 and the second electrode 112 of the intersection 110A shown in Fig. 6A are made thinner.

[0079] The intersection 110A shown in FIG. 7A includes a first electrode 111, a second electrode 112, a piezoelectric body 113, three substrates 114, a shield electrode 115, and an OCA (Optical Clear Adhesive) 116. The intersection 110A shown in FIG. 7A has a configuration in which the shield electrode 115, the OCA 116, the substrate 114, the second electrode 112, the piezoelectric body 113, the first electrode 111, and the substrate 114 are stacked on top of the bottom substrate 114. In other words, the intersection 110A shown in FIG. 7A has a configuration in which a third substrate 114 having a shield electrode 115 on one surface is attached with the OCA 116 below the substrate 114 below the intersection 110A shown in FIG. 2. As with the intersection 110A shown in FIG. 5C, an AC voltage may be applied to the shield electrode 115 when detecting the position of a hand using capacitance.

[0080] The intersection 110A shown in Fig. 7B has a configuration in which the uppermost substrate 114 of the intersection 110A shown in Fig. 7A has been removed. In other words, the intersection 110A shown in Fig. 7B has a configuration in which a third substrate 114 having a shield electrode 115 on one surface is attached below the intersection 110A shown in Fig. 4A using an OCA 116.

[0081] 7C has a configuration in which the substrate 114 below the second electrode 112 of the intersection 110A shown in Fig. 7A has been removed, and the substrate 114 provided with the shield electrode 115 has been inverted upside down. The substrate 114 provided with the shield electrode 115 can be inverted upside down from that shown in Fig. 7A, with the shield electrode 115 facing downward, and then adhered to the bottom of the second electrode 112 by the OCA 116.

[0082] <Proximity detection device 100M according to a modified embodiment> Fig. 8 is a diagram showing an example of a proximity detection device 100M according to a modified example of the embodiment. The proximity detection device 100M includes a proximity detection unit 110M instead of the proximity detection unit 110 shown in Fig. 1. Other configurations are similar to those of the proximity detection device 100 shown in Fig. 1. Here, differences will be described.

[0083] Instead of the configuration of providing a piezoelectric element 113 at every intersection 110A between the first electrode 111 and the second electrode 112 as in the proximity detection unit 110 of Figure 1, the proximity detection unit 110M has a configuration in which a piezoelectric element 113A used for transmitting ultrasonic waves and a piezoelectric element 113B used for receiving ultrasonic waves are arranged between the first electrode 111 and the second electrode 112 at intersections 110B1 and 110B2, respectively.

[0084] The intersections 110B1 and 110B2 are arranged so as to include mutually different first electrodes 111 for every other one of the plurality of first electrodes 111. Furthermore, the intersections 110B1 and 110B2 are arranged so as to include mutually different first electrodes 111 for every other one of the plurality of second electrodes 112.

[0085] The intersecting portion 110B1 and the intersecting portion 110B2 are positioned so as to be not adjacent to each other in the X direction and the Y direction in a plan view, but are disposed diagonally. The piezoelectric body 113A used for transmitting ultrasonic waves and the piezoelectric body 113B used for receiving ultrasonic waves have the same configuration as the piezoelectric body 113 of the proximity detection device 100.

[0086] In the proximity detection device 100M having such a configuration, when transmitting ultrasonic waves, the first electrode 111 and the second electrode 112 included in the intersection 110B1 are selected by the MUX 120, and an AC signal for ultrasonic waves is applied to the piezoelectric body 113A.

[0087] Furthermore, when receiving ultrasound, the first electrode 111 and the second electrode 112 included in the intersection 110B2 are selected by the MUX 120, and the waveform generated by the charges of the first electrode 111 and the second electrode 112 is acquired by the receiving circuit 140.

[0088] The method of detecting a position by capacitance in the proximity detection device 100M is the same as the method of detecting a position by capacitance in the proximity detection device 100.

[0089] By separating the piezoelectric element 113A used for transmitting ultrasonic waves from the piezoelectric element 113B used for receiving ultrasonic waves, as in the proximity detection device 100M of the modified embodiment, the switching control of MUX 120 and the control of waveform acquisition in the receiving circuit 140 when detecting the distance to the hand using ultrasonic waves are simplified, and there is an advantage in that the separation of the transmitting and receiving functions makes it easier to improve the performance of the device.

[0090] The above describes a proximity detection device according to an exemplary embodiment of the present invention, but the present invention is not limited to the specifically disclosed embodiment, and various modifications and variations are possible without departing from the scope of the claims.

[0091] The international application that is the original application of this application claims priority based on Japanese Patent Application No. 2021-077787, filed on April 30, 2021, the entire contents of which are incorporated herein by reference. [Explanation of symbols]

[0092] 100, 100M proximity detector 110, 110M proximity detection unit 110A, 110B1, 110B2 intersection 111 1st electrode 112 2nd electrode 113 Piezoelectric 115 Shield electrode 120 MUX 130 Transmitting circuit 140 Receiver Circuit 145 Timer 150 MPU 152 Calculation Unit

Claims

1. A proximity detection device that detects the proximity of an object, a plurality of first electrodes; One or more piezoelectric bodies; a plurality of second electrodes; Equipped with A proximity detection device, characterized in that each of the one or more piezoelectric bodies is provided between at least one of the plurality of first electrodes and at least one of the plurality of second electrodes.

2. the first electrodes extend in a first direction and are arranged in a second direction intersecting the first direction; the second electrodes extend in the second direction and are arranged in a plurality in the first direction; The proximity detector according to claim 1 , wherein the piezoelectric body is provided so as to be sandwiched between the first electrode and the second electrode at a location where the first electrode and the second electrode intersect.

3. 3. The proximity detection device according to claim 1, further comprising a third electrode provided on the side opposite to the side where the object approaches with respect to the first electrode and the second electrode.

4. 4. The proximity detector according to claim 3, wherein the third electrode is connected to ground.

5. 3. The proximity detector according to claim 1, wherein the first electrode and the second electrode are provided so as to be in contact with the piezoelectric body.

6. 3. The proximity detector according to claim 1, wherein the piezoelectric body is an electret having piezoelectric properties.

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