Touch sensor, touch detection method, and display device

Abstract

To provide a touch sensor capable of improving the resolution of touch detection, and a display device.SOLUTION: In a display device comprising a display controller 1, a display panel 2, and a touch sensor, the touch sensor is arranged in a matrix across a first direction and a second direction crossing the first direction. The touch sensor includes a plurality of sensor elements 50, which can transmit and receive ultrasonic waves, and a plurality of wirings RL1 to RL5 and TL1 to TL5 connected to the plurality of sensor elements 50. At least one of the plurality of wirings RL1 to RL5 and TL1 to TL5 is shared by the plurality of sensor elements 50.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a touch sensor, a touch detection method, and a display device.

Background Art

[0002] In recent years, display devices that can be operated by touching a display with a finger, a pen, or the like have become widely popular. Such a display device includes a sensor (touch sensor) that detects contact with the display. Various configurations such as a capacitance method, a conductive film method, an optical method, and an ultrasonic method are adopted for the touch sensor. Among these methods, the ultrasonic touch sensor has an advantage that it can detect a touch without degrading the transmittance of the panel.

[0003] Patent Document 1 discloses an ultrasonic touch sensor including a piezoelectric element that emits ultrasonic waves and a sensor element that detects the reflected ultrasonic waves. The touch sensor described in Patent Document 1 detects the ultrasonic waves reflected by an object and detects the contact of the object.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, when the number of piezoelectric elements and sensor elements increases, the number of wirings also increases, and the circuit configuration becomes complicated. Furthermore, the high-density mounting of the piezoelectric elements and sensor elements is hindered, and it may be difficult to improve the resolution of touch detection.

[0006] An object of the present invention is to provide a touch sensor and a display device capable of improving the resolution of touch detection.

Means for Solving the Problems

[0007] According to one aspect of the present invention, there is provided a touch sensor including a plurality of sensor elements arranged in a matrix over a first direction and a second direction intersecting the first direction and capable of transmitting and receiving ultrasonic waves, and a plurality of wirings connected to the plurality of sensor elements, wherein at least one of the plurality of wirings is shared by the plurality of sensor elements.

[0008] According to another aspect of the present invention, there is provided a touch sensor including M×N sensor elements each having a vibration element that emits ultrasonic waves and a detection element that detects ultrasonic waves, M transmission wirings each extending in a first direction and connected to the N vibration elements, and N reception wirings each extending in a second direction intersecting the first direction and connected to the M detection elements.

[0009] According to another aspect of the present invention, there is provided a touch detection method including emitting ultrasonic waves from a plurality of sensor elements arranged in a matrix over a first direction and a second direction intersecting the first direction, and receiving ultrasonic waves in the plurality of sensor elements, wherein the plurality of sensor elements are connected to a plurality of wirings, and at least one of the plurality of wirings is shared by the plurality of sensor elements.

Effect of the Invention

[0010] According to the present invention, it is possible to provide a touch sensor and a display device capable of improving the resolution of touch detection.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Embodiments for Carrying Out the Invention

[0012] Hereinafter, embodiments according to the present invention will be described in detail with reference to the drawings. Elements having the same functions throughout the drawings are denoted by the same reference numerals, and redundant descriptions may be omitted or simplified.

[0013] [First Embodiment] FIG. 1 is a block diagram of a display device according to the present invention. The display device according to this embodiment can be a television display, a computer display, a smartphone, a tablet computer, a signage, a flexible display, or the like. The display device includes a display controller 1, a display panel 2, and a touch sensor. The touch sensor includes a touch controller 3, a transmission circuit 4, a touch panel 5, and a reception circuit 6. The touch panel 5 includes a plurality of sensor elements 50, and each sensor element 50 includes a vibration element 51 and a detection element 52.

[0014] The display panel 2 can be a liquid crystal display, an organic EL (EL: Electro-Luminescence) panel, etc. The display panel 2 includes a plurality of pixels (not shown) arranged in a matrix. The display panel 2 displays an image based on the image signal RGB, the main clock signal MCLK, the horizontal synchronization signal Hsync, and the vertical synchronization signal Vsync supplied from the display controller 1.

[0015] The display controller 1 includes a clock circuit, a voltage generation circuit, etc. The display controller 1 outputs the image signal RGB, the main clock signal MCLK, the horizontal synchronization signal Hsync, the vertical synchronization signal Vsync, etc. to the display panel 2.

[0016] The touch panel 5 is provided to face the display panel 2. The touch panel 5 may be provided on the display surface of the display panel 2 or on the back surface of the display surface of the display panel 2. Here, the horizontal direction of the touch panel 5 is defined as the X direction (row direction), the vertical direction of the touch panel 5 is defined as the Y direction (column direction), and the vertical direction with respect to the operation surface of the touch panel 5 is defined as the Z direction.

[0017] The sensor element 50 includes a vibration element 51 and a detection element 52, and is arranged in an m-row and n-column matrix in the touch panel 5. FIG. 1 shows, as an example, 25 sensor elements 50 arranged in a 5-row and 5-column matrix.

[0018] The vibration element 51 vibrates in response to an applied signal and emits ultrasonic waves toward the operation surface of the touch panel 5. By changing the frequency of the signal applied to the vibration element 51, the frequency of the ultrasonic waves can be changed.

[0019] The detection element 52 is arranged at a position close to the vibration element 51 in the sensor element 50. The ultrasonic waves emitted from the vibration element 51 are reflected by the operation surface of the touch panel 5 or an object and detected by the detection element 52. The detection element 52 vibrates by detecting ultrasonic waves and outputs a signal corresponding to the vibration.

[0020] Among the plurality of receiving wirings RL1 to RL5, any one of the receiving wirings is shared by the plurality of sensor elements 50. Also, among the plurality of transmitting wirings TL1 to TL5, any one of the transmitting wirings is shared by the plurality of sensor elements 50. Thereby, the display device in the present embodiment can reduce the number of wirings connected to the sensor elements 50 as compared with the case where wirings are individually provided for the plurality of sensor elements 50.

[0021] The transmission circuit 4 is connected to the plurality of vibrating elements 51 of the touch panel 5 via the plurality of transmission wirings TL1 to TL5. The transmission circuit 4 transmits a drive signal to the plurality of vibrating elements 51 of the touch panel 5 via the plurality of transmission wirings TL1 to TL5.

[0022] The reception circuit 6 is connected to the detection elements 52 of the touch panel 5 via the plurality of reception wirings RL1 to RL5. The reception circuit 6 outputs the detection signals of the plurality of detection elements 52 to the touch controller 3 via the plurality of reception wirings RL1 to RL5.

[0023] The touch controller 3 supplies a drive signal for driving the sensor element 50 to the transmission circuit 4. Also, the touch controller 3 receives the detection signal output from the sensor element 50 via the reception circuit 6. The touch controller 3 detects the contact between the object and the touch panel 5 based on the detection signal output from the sensor element 50.

[0024] FIG. 2 is a cross-sectional view of the display device in the present embodiment, and is a cross-sectional view of the display panel 2 along the line I-I' in FIG. 1. As shown in FIG. 2, the display device includes a display panel 2 and a touch panel 5 provided above the display panel 2. The display panel 2 includes a substrate 21, a transistor 22, a buffer layer 23, an anode electrode 24, a bank layer 25, an organic light-emitting layer 26, a cathode electrode 27, an insulating layer 28, and a sealing layer 29.

[0025] The substrate 21 is made of a rigid material such as glass. Also, the substrate 21 may be a flexible substrate that can expand and contract. When the substrate 21 is a flexible substrate, the substrate 21 is made of a plastic such as polyimide or polyester.

[0026] The buffer layer 23 is provided on the substrate 21. The buffer layer 23 can be made of an inorganic insulating material such as silicon oxide (SiOx) or silicon nitride (SiNx). The buffer layer 23 has a function of protecting the transistor 22 from impurities such as moisture or oxygen that penetrate from the outside. The buffer layer 23 has a contact hole for connecting the transistor 22 and the anode electrode 24.

[0027] The transistor 22 is embedded inside the buffer layer 23. The transistor 22 is provided on the substrate 21. The transistor 22 is a thin film transistor (TFT: Thin Film Transistor). The transistor 22 is made of a material such as polysilicon or amorphous silicon. The transistor 22 constitutes the circuit of the pixel included in the display panel 2.

[0028] The bank layer 25 is provided on the buffer layer 23. The bank layer 25 can be made of an inorganic insulating material such as silicon oxide (SiOx) or silicon nitride (SiNx). The bank layer 25 has a contact hole for connecting the anode electrode 24 and the organic light emitting layer 26.

[0029] The anode electrode 24 is embedded inside the bank layer 25. The anode electrode 24 is provided on the buffer layer 23. When the display device is of the bottom emission type that emits light from the substrate (-Y direction), the anode electrode 24 can be composed of an opaque electrode such as silver (Ag), gold (Au), or aluminum (Al). When the display device is of the top emission type that emits light from the opposite side of the substrate (Y direction), the anode electrode 24 can be composed of a transparent electrode such as indium tin oxide (ITO) or fluorine-doped tin oxide (FTO). The anode electrode 24 is connected to the transistor 22 through the contact hole of the buffer layer 23.

[0030] The organic light-emitting layer 26 is provided on the bank layer 25. The organic light-emitting layer 26 can be an organic light-emitting element (OLED). The organic light-emitting layer 26 is connected to the anode electrode 24 through the contact hole of the bank layer 25.

[0031] The cathode electrode 27 is provided on the organic light-emitting layer 26. When the display device is of the bottom emission type that emits light from the substrate (-Y direction), the cathode electrode 27 can be composed of an opaque electrode such as silver (Ag), gold (Au), or aluminum (Al). When the display device is of the top emission type that emits light from the opposite side of the substrate (Y direction), the cathode electrode 27 can be composed of a transparent electrode such as indium tin oxide (ITO) or fluorine-doped tin oxide (FTO).

[0032] The insulating layer 28 is provided on the cathode electrode 27. The insulating layer 28 may be composed of an inorganic insulating material such as silicon oxide (SiOx) or silicon nitride (SiNx), or may be composed of an insulating organic substance. The insulating layer 28 has a function of insulating the cathode electrode 27 from the outside.

[0033] The sealing layer 29 is provided on the insulating layer 28. The sealing layer may be composed of an inorganic insulating material such as silicon oxide (SiOx) or silicon nitride (SiNx), or may be composed of an insulating organic substance or the like. The sealing layer 29 has a function of preventing impurities such as moisture or oxygen that penetrate from the outside.

[0034] FIG. 3 is a cross-sectional view of the display device in the present embodiment and is a cross-sectional view of the touch panel 5 along the line I-I' in FIG. 1. As shown in FIG. 3, the touch panel 5 is provided above the display panel 2. The touch panel 5 includes a vibration element 51, a detection element 52, an insulating layer 53, an insulating layer 54, and an insulating layer 55. Further, the vibration element 51 includes an electrode 511, a dielectric 512, and an electrode 513, and the detection element 52 includes an electrode 521, a dielectric 522, and an electrode 523.

[0035] The insulating layer 53 is provided above the display panel 2. The insulating layer 53 may be composed of an inorganic insulating material such as silicon oxide (SiOx) or silicon nitride (SiNx), or may be composed of an insulating organic substance or the like. The insulating layer 53 has a contact hole for connecting the electrode 511 and the dielectric 512.

[0036] The electrode 511 is embedded in the lower surface of the insulating layer 53. The electrode 511 extends in the X direction and is shared with the electrode 511 of other vibration elements 51 in the X direction. The electrode 511 is provided on the upper surface of the insulating layer 53 through the contact hole of the insulating layer 53. The electrode 511 may be composed of a transparent electrode such as indium tin oxide or fluorine-doped tin oxide. The electrode 521 is embedded in the upper surface of the insulating layer 53. The electrode 521 is provided between the portions of the electrode 511 provided on the upper surface of the insulating layer 53. The electrode 521 may be composed of the same material as the electrode 511.

[0037] The insulating layer 54 is provided on the insulating layer 53. The insulating layer 54 may be composed of the same material as the insulating layer 53. The insulating layer 54 has a contact hole for connecting the dielectric 522 and the electrode 523.

[0038] The dielectric 512 is embedded in the lower surface of the insulating layer 54. The lower surface of the dielectric 512 is connected to the electrode 511 provided on the upper surface of the insulating layer 53. The dielectric 512 can be composed of materials such as dielectric elastomer, ceramic, barium titanate, lead zirconate titanate, zinc oxide, etc. The electrode 513 is embedded in the insulating layer 54. The electrode 513 is connected to the upper surface of the dielectric 512. The electrode 513 can be composed of the same material as the electrode 511. The dielectric 522 is embedded in the lower surface of the insulating layer 54. The lower surface of the dielectric 522 is connected to the electrode 521 provided on the upper surface of the insulating layer 53. The dielectric 522 can be composed of the same material as the dielectric 512.

[0039] The insulating layer 55 is provided on the insulating layer 54. The insulating layer 55 can be composed of the same material as the insulating layer 53. The electrode 523 is embedded in the lower surface of the insulating layer 55. The electrode 523 extends in the X direction and is shared with the electrode 521 of the other detection element 52 in the X direction. The electrode 523 is connected to the upper surface of the dielectric 522 through the contact hole of the insulating layer 54. The electrode 523 can be composed of the same material as the electrode 511.

[0040] The electrode 513 is connected to the transmission circuit 4 via one of the plurality of transmission wirings TL1 to TL5 together with the electrode 513 of the other vibration element 51 arranged in the Y direction. The electrode 511 is connected to the transmission circuit 4 via a wiring (not shown). The electrodes 511 and 513 receive drive signals from the transmission circuit 4.

[0041] When a drive signal is transmitted to electrodes 511 and 513, an electrostatic force is generated between electrode 511 and electrode 513. As electrodes 511 and 513 are attracted by the electrostatic force, dielectric 512 contracts in the Z direction. As a result, vibration element 51 contracts in the Z direction. When the drive signal is no longer applied to electrodes 511 and 513, the electrostatic force generated between electrodes 511 and 513 disappears. As electrodes 511 and 513, which are attracted by the electrostatic force, move away from each other, dielectric 512 expands in the Z direction. As a result, vibration element 51 expands in the Z direction. That is, in response to the drive signal transmitted to electrodes 511 and 513, vibration element 51 contracts and expands, and vibration element 51 can emit ultrasonic waves to touch panel 5.

[0042] When ultrasonic waves are applied to dielectric 522, a detection signal corresponding to the vibration of dielectric 522 can be generated between electrodes 521 and 523. Therefore, based on the detection signal output from detection element 52, it becomes possible to detect the ultrasonic waves emitted by vibration element 51.

[0043] Electrode 523 is connected to receiving circuit 6 via any one of a plurality of receiving wirings RL1 to RL5 together with electrode 523 of another detection element 52 arranged in the X direction. Electrode 521 is connected to receiving circuit 6 via a wiring (not shown).

[0044] FIG. 4 is a block diagram of the display device according to the present embodiment, showing touch controller 3, transmission circuit 4, touch panel 5, and receiving circuit 6. Touch controller 3 includes a CPU 301 (Central Processing Unit), a ROM (Read Only Memory) 302, a RAM (Random Access Memory) 303, a storage device 304, a communication I / F 305, and a bus 306. Each part of touch controller 3 is connected to each other via bus 306.

[0045] The CPU 301 is a processor that performs a predetermined calculation according to a program stored in the ROM 303, the storage device 304, etc., and also has a function of controlling each part of the touch controller 3. The CPU 301 loads and executes the program stored in the ROM 303, the storage device 304, etc. into the RAM 302. The RAM 302 is composed of a volatile storage medium and provides a temporary memory area necessary for the operation of the CPU 301. The ROM 303 is composed of a non-volatile storage medium and stores necessary information such as the operation program of the CPU 301. The storage device 304 is composed of a non-volatile storage medium such as a flash memory or a hard disk. The communication I / F 305 is a communication interface for wireless communication or wired communication and is a module for communicating with other devices.

[0046] The transmission circuit 4 includes a DA converter 401 and a multiplexer 402. The DA converter 401 converts the digital signal output from the CPU 301 into a drive signal of a predetermined frequency. The drive signal is output to the multiplexer 402. The multiplexer 402 includes an input node and a plurality of output nodes. The multiplexer 402 also includes a control node (not shown). The drive signal from the DA converter 401 is input to the input node. The control signal from the CPU 301 is input to the control node. The multiplexer 402 can select an output node based on the control signal of the CPU 301. The transmission wirings TL1 to TL5 are connected to the output nodes. The drive signal of a predetermined frequency is sequentially output to the vibration element 51 via the transmission wirings TL1 to TL5.

[0047] The receiving circuit 6 includes a multiplexer 601, an amplifier circuit 602, and an AD converter 603. The multiplexer 601 includes a plurality of input nodes and an output node. The multiplexer 601 also includes a control node (not shown). The receiving wirings RL1 to RL5 are connected to the input nodes. Detection signals are input from the detection element 52 to the input nodes via the receiving wirings RL1 to RL5. A control signal from the CPU 301 is input to the control node, and according to the control signal, the detection signals of the receiving wirings RL1 to RL5 are sequentially output from the output node. The amplifier circuit 602 includes a differential amplifier circuit and amplifies the voltage of the weak detection signal output from the detection element 52. The AD converter 603 includes a comparison circuit and a reference voltage generation circuit and converts the detection signal into a digital signal. The AD converter 603 outputs the digital signal to the CPU 301 via the bus 306.

[0048] FIG. 5 is a timing chart showing the operation of the display device in the present embodiment. To simplify the explanation, it is assumed that the touch panel 5 has three transmission wirings TL1 to TL3, three receiving wirings Rl to RL3, and nine (3×3) sensor elements 50.

[0049] At time t1, the transmission circuit 4 switches the multiplexer 402 and selects the transmission wiring TL1 as the output node. From time t1 to t2, the transmission circuit 4 outputs drive signals to the three vibrating elements 51 via the transmission wiring TL1. The three vibrating elements 51 vibrate according to the drive signals and emit ultrasonic waves toward the operation surface of the touch panel 5. Each of the ultrasonic waves emitted by the three vibrating elements 51 is reflected by the operation surface or the object of the touch panel 5 and reaches each of the nine detection elements 52. The paths of the ultrasonic waves from the vibrating elements 51 to the detection elements 52 are different for each of the nine detection elements 52. Therefore, the detection signals output from the nine detection elements 52 can also be different from each other.

[0050] At times t2 to t3, the receiving circuit 6 switches the multiplexer 601 and selects the receiving wiring RL1 as the input node. Here, since three detection elements 52 are connected to the receiving wiring RL1, three detection signals are superimposed and output to the receiving wiring RL1. The receiving circuit 6 receives the detection signal on the receiving wiring RL1, and the touch controller 3 holds the detection signal after AD conversion in the storage device 304.

[0051] At times t3 to t4, the transmitting circuit 4 outputs a drive signal to the three vibrating elements 51 via the transmitting wiring TL1. At times t4 to t5, the receiving circuit 6 selects the receiving wiring RL2 and receives the detection signal on the receiving wiring RL2. The touch controller 3 holds the detection signal after AD conversion in the storage device 304.

[0052] At times t5 to t6, the transmitting circuit 4 further outputs a drive signal to the three vibrating elements 51 via the transmitting wiring TL1. At times t6 to t7, the receiving circuit 6 selects the receiving wiring RL3 and receives the detection signal on the receiving wiring RL3. After AD conversion, it is held in the storage device 304.

[0053] At time t7, the transmitting circuit 4 switches the output node of the multiplexer 402 from the transmitting wiring TL1 to the transmitting wiring TL2. The transmitting circuit 4 outputs a drive signal to the vibrating element 51 three times via the transmitting wiring TL2 (times t7 to t8, t9 to t10, t11 to t12). The receiving circuit 6 sequentially selects the receiving wirings RL1 to RL3 by the multiplexer 601 and receives the detection signals on the respective receiving wirings RL1 to RL3 (times t8 to t9, t10 to t11, t12 to t13). The touch controller 3 AD-converts the received detection signal and holds it in the storage device 304.

[0054] Similarly, at time t13, the transmission circuit 4 switches the output node of the multiplexer 402 from the transmission wiring TL2 to the transmission wiring TL3. The transmission circuit 4 outputs a drive signal to the vibration element 51 three times via the transmission wiring TL3 (times t13 to t14, t15 to t16, t17 to t18). The reception circuit 6 sequentially selects the reception wirings RL1 to RL3 by the multiplexer 601 and receives the detection signals on each of the reception wirings RL1 to RL3 (times t14 to t15, t16 to t17, t18 to t19). The received detection signals are AD-converted and then held in the storage device 304.

[0055] As described above, the touch controller 3 can acquire 3×3 = 9 detection signals corresponding to the combinations of the transmission wirings TL1 to TL3 and the reception wirings RL1 to RL3.

[0056] Hereinafter, a method for specifying the contact position between the object and the touch panel 5 will be described with reference to FIG. 5. The change in the waveform of the detection signal increases as the transmission distance of the ultrasonic wave from the vibration element 51 that emits the ultrasonic wave to the detection element 52 that detects the ultrasonic wave becomes shorter. For example, it is assumed that the object contacts at a position corresponding to the sensor element 50 connected to the reception wiring RL1 and the transmission wiring TL2. When the vibration element 51 in the sensor element 50 connected to the transmission wiring TL2 emits ultrasonic waves and the detection element 52 connected to the reception wiring RL1 detects the ultrasonic waves, the transmission distance of the ultrasonic waves becomes the shortest. Therefore, among the nine detection signals corresponding to the combinations of the transmission wirings TL1 to TL3 and the reception wirings R1 to RL3, the change in the waveform of the detection signal is the largest in the detection signal corresponding to the reception wiring R1 and the transmission wiring TL2. The touch controller 3 can specify the contact position of the object by determining the detection signal with the largest change in waveform.

[0057] Note that the method for determining the contact position of the object is not limited to the method of determining the detection signal with the maximum waveform change. For example, by determining the detection signal whose waveform change is greater than a predetermined threshold value, the touch controller 3 can specify the contact position of the object. Thereby, even when the object contacts the touch panel 5 at a plurality of positions, the touch controller 3 can specify the contact position.

[0058] The change in the waveform of the detection signal described above can be determined by various methods. Hereinafter, a method for determining the change in the waveform of the detection signal will be described with reference to FIG. 6.

[0059] FIGS. 6(a) to 6(d) show detection signals in the display device according to the present embodiment. In FIGS. 6(a) to 6(d), the signal component A represents the reflected wave from the touch panel 5, and the signal component B represents the reflected wave from the object. Note that in FIG. 6(a), the waveform of the ultrasonic frequency and the waveform of the envelope are shown together, but in FIGS. 6(b) to 6(d), the waveform of the ultrasonic frequency is omitted, and the waveform of the envelope is shown as the detection signal.

[0060] FIG. 6(a) shows a determination method based on the time difference of the detection signal. The ultrasonic waves emitted from the vibration element 51 are emitted in various directions and are repeatedly reflected within the touch panel 5. Therefore, the detection signal may include a plurality of signal components based on higher-order reflected waves in addition to the primary reflected wave. Here, when the object contacts the touch panel 5, the ultrasonic waves from the vibration element 51 are reflected not only by the touch panel 5 but also by the object. Therefore, the detection signal includes the signal component B of the reflected wave from the object. Here, by determining whether the time difference Δt between the signal component A and the signal component B is within a known range, the change in the detection signal can be detected. That is, when the time difference Δt is within the known range, the touch controller 3 can determine the contact of the object.

[0061] FIG. 6(b) shows a determination method based on the voltage difference of the detection signal. When contacting the touch panel 5, the detection signal may include, in addition to the signal component A, a signal component B based on the reflected wave in the object. The touch controller 3 can determine the contact of the object by determining whether the voltage difference ΔV between the peak voltage Va of the signal component A and the peak voltage Vb of the signal component B is within a known range.

[0062] FIG. 6(c) shows a determination method based on the time width of the detection signal. The time width of the detection signal can be detected, for example, as the time of the detection signal exceeding a predetermined threshold voltage Vth. The change in the detection signal may be detected by determining whether the difference between the time width ta of the signal component A and the time width tb of the signal component B is within a known range.

[0063] FIG. 6(d) shows a determination method based on the frequency spectrum of the detection signal. In FIG. 6(d), the horizontal axis represents the frequency and the vertical axis represents the sound pressure. The frequency spectrum can be calculated by, for example, performing a Fourier transform on the detection signal. The frequency of the ultrasonic wave emitted from the vibration element 51 changes by passing through a dielectric or the like in the touch panel 5. Therefore, the frequency of the detection signal changes based on the transmission distance, the transmission medium, and the like. As shown in FIG. 6(d), spectrum A represents the reflected wave in the touch panel 5, and spectrum B represents the reflected wave in the object. The touch controller 3 can detect the contact between the object and the touch panel 5 from the peak frequency of the spectrum of the detection signal.

[0064] The touch controller 3 can detect the contact between the object and the touch panel 5 based on the change in the waveform of the detection signal after AD conversion using the above-described determination method.

[0065] According to this embodiment, the plurality of sensor elements 50 share any one of the plurality of receiving wirings. Also, the plurality of sensor elements 50 share any one of the plurality of transmitting wirings. Thereby, compared with the case where wirings are individually provided for the plurality of sensor elements 50, the number of wirings connected to the sensor elements 50 can be reduced, and the circuit configuration can be simplified. Furthermore, since the sensor elements 50 can be mounted at high density, it becomes possible to improve the resolution of touch detection.

[0066] [Second Embodiment] Subsequently, the display device according to the second embodiment will be described. The display device according to this embodiment is different from the first embodiment in that ultrasonic waves of different frequencies are used. Hereinafter, the description will focus on the configuration different from the first embodiment.

[0067] FIG. 7 is a block diagram of the display device in this embodiment, showing a touch controller 3, a transmission circuit 4, a touch panel 5, and a reception circuit 6. The transmission circuit 4 includes a plurality of DA converters 401. Each of the plurality of DA converters 401 is provided for each vibration element 51. The CPU 301 outputs different digital signals for each DA converter 401, and each of the DA converters 401 can generate drive signals of different frequencies. With such a configuration, it is possible to simultaneously output a plurality of drive signals of different frequencies to the transmission wirings TL1 to TL5. The reception circuit 6 sequentially selects the reception wirings RL1 to RL5 via the multiplexer 601 as in the first embodiment, and receives the detection signal.

[0068] FIG. 8 is a timing chart showing the operation of the display device in this embodiment. Similar to FIG. 5, it is assumed that the touch panel 5 has three transmission wirings TL1 to TL3, three reception wirings Rl to RL3, and nine (3×3) sensor elements 50.

[0069] At times t1 to t2, the receiving circuit 6 switches the multiplexer 601 and selects the receiving wiring RL1 as the input node. The transmitting circuit 4 simultaneously outputs drive signals to the plurality of transmitting wirings TL1 to TL3. That is, the transmitting circuit 4 outputs a drive signal of frequency f1 to the transmitting wiring TL1, a drive signal of frequency f2 to the transmitting wiring TL2, and a drive signal of frequency f3 to the transmitting wiring TL3. Thereby, ultrasonic waves of different frequencies f1, f2, and f3 are simultaneously emitted.

[0070] At times t2 to t3, the receiving circuit 6 selects the receiving wiring RL1 and receives the detection signals of the three detection elements 52 via the receiving wiring RL1. The detection signal of the receiving wiring RL1 includes signal components of frequencies f1, f2, and f3. Thereby, the receiving circuit 6 can receive a detection signal including signal components of the three frequencies f1, f2, and f3.

[0071] At times t3 to t5, the transmitting circuit 4 simultaneously outputs drive signals to the plurality of transmitting wirings TL1 to TL3. The receiving circuit 6 selects the receiving wiring RL2 and receives the detection signal in the receiving wiring RL2.

[0072] At times t5 to t7, the transmitting circuit 4 simultaneously outputs drive signals to the plurality of transmitting wirings TL1 to TL3. The receiving circuit 6 selects the receiving wiring RL3 and receives the detection signal in the receiving wiring RL3.

[0073] Also in this embodiment, based on the time change of each of a plurality of detection signals, the contact position between the object and the touch panel 5 can be specified. That is, the change in the waveform of the detection signal increases as the transmission distance of the ultrasonic wave from the vibration element 51 that emits the ultrasonic wave to the detection element 52 that detects the ultrasonic wave becomes shorter. The touch controller 3 can specify the contact position of the object by determining the detection signal with the maximum change in waveform. In particular, in this embodiment, since the detection signal includes a plurality of frequency components corresponding to a plurality of transmission wirings (drive signals), it is possible to easily determine which transmission wiring the frequency component that has changed in the detection signal corresponds to. For this reason, it is possible to specify the contact position in a short time.

[0074] Also in this embodiment, the method for determining the contact position of the object is not limited to the method of determining the detection signal with the maximum change in the detection signal. For example, the contact position of the object can be specified based on the frequency change of the signal components included in the detection signal. Hereinafter, a method for specifying the contact position will be described with reference to FIG. 9.

[0075] FIGS. 9(a) and 9(b) show the detection signals in the display device according to this embodiment, and show the spectra obtained by Fourier-transforming the detection signals. In FIGS. 9(a) and 9(b), the horizontal axis represents the frequency, and the vertical axis represents the sound pressure.

[0076] FIG. 9(a) shows the spectrum when there is no contact between the object and the touch panel 5. As described above, the detection signal includes signal components having the frequencies f1, f2, and f3 of the drive signal. For this reason, the peak frequencies of the spectrum have the frequencies f1, f2, and f3. Note that when the ultrasonic wave emitted from the vibration element 51 propagates and reflects on the touch panel 5, the frequency of the ultrasonic wave can be displaced. For this reason, the peak frequencies of the spectrum may include a predetermined error with respect to the frequencies f1, f2, and f3 of the drive signal.

[0077] FIG. 9(b) shows the spectrum when there is contact between the object and the touch panel 5. When the object contacts the touch panel 5, the ultrasonic wave is reflected by the touch panel 5 and also reflected by the object. Due to the change in the transmission distance of the ultrasonic wave, the ultrasonic wave reflected by the object has a different frequency from the ultrasonic wave reflected by the touch panel 5. The sound pressure at frequency f2 decreases, and a peak appears at frequency f2a near frequency f2. The touch controller 3 can detect the contact between the object and the touch panel 5 from the peak frequency of the spectrum of the detection signal.

[0078] The change in the peak frequency of the spectrum of the detection signal also occurs not only at frequency f2 but also at frequencies f1 and f3. In FIG. 9(b), the change in the spectrum at frequency f2 is larger than the change in the spectrum at frequencies f1 and f3. Therefore, among the signal components of the detection signal, the signal component based on the ultrasonic wave emitted from the vibration element 51 in the sensor element 50 connected to the transmission wiring TL2 changes the most significantly. The touch controller 3 determines that the object is in contact at the position corresponding to the transmission wiring TL2 by determining the signal component of the detection signal with the largest change in waveform. The touch controller 3 identifies the contact position of the object by determining the detection signal with the largest spectrum change at frequency f2 among the detection signals corresponding to the reception wirings RL1 to RL3.

[0079] Also in this embodiment, the touch controller 3 can identify the contact position of the object by comparing the detection signals corresponding to the reception wirings RL1 to RL3.

[0080] Also in this embodiment, the plurality of sensor elements 50 share any one of the plurality of reception wirings. Further, the plurality of sensor elements 50 share any one of the plurality of transmission wirings. Thereby, the circuit configuration can be simplified, the sensor elements 50 can be mounted at high density, and the resolution of touch detection can be improved. Also, in this embodiment, the transmission circuit 4 simultaneously transmits a plurality of drive signals having different frequencies to the plurality of transmission wirings. Thereby, the time required to specify the contact position can be shortened as compared with the first embodiment in which the drive signals are sequentially transmitted to the plurality of transmission wirings.

[0081] [Third Embodiment] Next, the display device in this embodiment will be described. The display device in this embodiment is different from the first embodiment in that it detects a touch and specifies a contact position by creating a learning model generated in advance by machine learning. Hereinafter, the description will focus on the configuration different from the first embodiment.

[0082] FIG. 10 is a flowchart of the display device according to this embodiment, showing the generation process of the learning model. The machine learning in this embodiment is supervised learning using teacher data, and the detection signals acquired from the plurality of sensor elements 50 are used as teacher data. The touch controller 3 acquires the teacher data (step S101). The touch controller 3 executes machine learning based on the teacher data (step S102). The touch controller 3 generates a learned model by repeatedly executing machine learning. The generated learning model is stored in the database of the display device (step S103).

[0083] FIG. 11 is a flowchart of the display device according to this embodiment, showing the calculation process of the learning model.

[0084] First, the touch controller 3 receives detection signals from the multiple sensor elements 50 (step S201). The touch controller 3 calculates a feature amount of each of the multiple detection signals (step S202). The feature amount of the detection signal may be a time difference, a voltage difference, a time width, or a peak frequency of a spectrum of the detection signal. Next, the touch controller 3 detects contact between an object and the touch panel 5 from the feature amount of the detection signal based on the trained model, and identifies the contact position between the object and the touch panel 5 (step S203).

[0085] As described above, according to this embodiment, by using a learning model that associates the feature amount of the detection signal with the touch of the object, it is possible to detect the touch of the object with the touch panel 5 and identify the touch position. The feature amount of the detection signal also changes depending on the transmission path of the ultrasonic waves from the vibration element 51 that emits the ultrasonic waves to the detection element 52 that detects the ultrasonic waves. Therefore, depending on the transmission path of the ultrasonic waves, it may be difficult to distinguish between a change in the feature amount of the detection signal due to the touch of the object and a change in the detection signal due to the transmission of the ultrasonic waves. In this embodiment, by using a learning model that associates the feature amount of the detection signal with the touch of the object, it may be possible to improve the accuracy of touch detection of the display device.

[0086] It should be noted that the above-described embodiments are merely illustrative examples of the implementation of the present invention, and the technical scope of the present invention should not be construed as being limited thereby. In other words, the present invention can be implemented in various forms without departing from its technical concept or main features. [Explanation of symbols]

[0087] 1 Display Controller 2 Display Panel 3. Touch Controller 4. Transmitting Circuit 5. Touch Panel 6 Receiving circuit 50 Sensor element 51 Detector element 52 Vibration element

Claims

1. A plurality of sensor elements arranged in a matrix over a first direction and a second direction intersecting the first direction, and capable of transmitting and receiving ultrasonic waves; A plurality of wirings connected to the plurality of sensor elements, A touch sensor, wherein at least one of the plurality of wirings is shared by the plurality of sensor elements.

2. Each of the plurality of sensor elements includes a vibration element that emits ultrasonic waves in response to a drive signal, The plurality of wirings extend in the first direction and include a plurality of transmission wirings connected to the plurality of vibration elements, The touch sensor according to claim 1, wherein the transmission wiring is shared by the plurality of sensor elements arranged in the first direction.

3. Each of the plurality of sensor elements includes a detection element that detects ultrasonic waves and outputs a detection signal, The plurality of wirings extend in the second direction and include a plurality of reception wirings connected to the plurality of detection elements, The touch sensor according to claim 2, wherein the reception wiring is shared by the plurality of sensor elements arranged in the second direction.

4. The touch sensor according to claim 3, further comprising a control unit that transmits the drive signal to the plurality of vibration elements via the plurality of transmission wirings and receives the detection signal from the plurality of detection elements via the plurality of reception wirings.

5. The touch sensor according to claim 4, wherein the control unit sequentially transmits the drive signals having the same frequency to each of the plurality of transmission wirings, and detects a touch based on the detection signals in each of the plurality of reception wirings.

6. The touch sensor according to claim 5, wherein the control unit detects a touch based on a change in the detection signal.

7. The touch sensor according to claim 5, wherein the control unit detects a touch based on a time difference between a plurality of signal components included in the detection signal.

8. The touch sensor according to claim 5, wherein the control unit detects a touch based on a voltage difference between peaks of a plurality of signal components included in the detection signal.

9. The touch sensor according to claim 5, wherein the control unit detects a touch based on a time width of a plurality of signal components included in the detection signal.

10. The touch sensor according to claim 5, wherein the control unit detects a touch based on a frequency change of a plurality of signal components included in the detection signal.

11. The touch sensor according to claim 4, wherein the control unit simultaneously transmits a plurality of the drive signals having different frequencies to the plurality of transmission wirings, and detects a touch based on the detection signals in each of the plurality of reception wirings.

12. The touch sensor according to claim 10, wherein the control unit detects a touch based on a change in a plurality of frequency components included in the detection signal.

13. The touch sensor according to claim 10, wherein the control unit detects a touch based on a peak value of a frequency spectrum of the detection signal.

14. The touch sensor according to claim 12, wherein the control unit specifies a touch position based on a value of the detection signal having the largest change among the plurality of detection signals.

15. The touch sensor according to claim 12, wherein the control unit specifies a plurality of touch positions based on changes in each of the plurality of detection signals.

16. The touch sensor according to claim 4, wherein the control unit includes a learning model that inputs data representing a feature amount of the detection signal and outputs data representing a touch position.

17. The touch sensor according to claim 16, wherein the feature amount includes at least one of a time difference between a plurality of signal components included in the detection signal, a voltage difference between peaks of the plurality of signal components, a time width of the plurality of signal components, and a frequency change of the plurality of signal components.

18. The control unit further includes a selection unit that selects a reception wiring connected to the control unit among the plurality of reception wirings, The touch sensor according to claim 4, wherein the selection unit sequentially selects reception wirings connected to the control unit.

19. M×N sensor elements each having a vibration element that emits ultrasonic waves and a detection element that detects ultrasonic waves, M transmission wirings that extend in a first direction and are each connected to the N vibration elements, A touch sensor comprising: N reception wirings that extend in a second direction intersecting the first direction and are each connected to the M detection elements.

20. The touch sensor according to claim 19, further comprising a control unit that transmits a drive signal to the vibration element via the transmission wiring and receives a detection signal from the detection element via the reception wiring.

21. The control unit sequentially selects the M transmission wirings, transmits the drive signals of the same frequency to the selected transmission wiring, sequentially selects the N reception wirings, and receives the detection signal via the selected reception wiring. The touch sensor according to claim 19 is characterized in that.

22. The control unit simultaneously transmits M drive signals of different frequencies to the M transmission wirings, sequentially selects the N reception wirings, and receives the detection signal via the selected reception wiring. The touch sensor according to claim 19 is characterized in that.

23. A touch panel including the touch sensor according to claim 1 or 19, A display device comprising a display panel provided opposite to the touch panel.

24. Emitting ultrasonic waves from a plurality of sensor elements arranged in a matrix over a first direction and a second direction intersecting the first direction; Receiving ultrasonic waves in a plurality of the sensor elements, The plurality of sensor elements are connected to a plurality of wirings, A touch detection method, characterized in that at least one of the plurality of wirings is shared by the plurality of sensor elements.

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