Touch panel, display device, and method for controlling a touch panel

Abstract

The present invention provides a touch panel, a display device, and a method for controlling the touch panel that enable touch detection by a touch sensor with appropriate sensitivity, regardless of the presence or absence of a filter. [Solution] The touch panel includes a touch detection control circuit 22. The touch detection control circuit 22 determines whether a filter is present. If it determines that no filter is present, it amplifies the signal from the touch sensor 15 by an amplification factor G1 to generate an amplified signal Sd1. Based on the amplified signal Sd1, it determines whether or not the touch sensor 15 has been touched by an indicator. If it determines that a filter is present, the touch detection control circuit 22 amplifies the signal from the touch sensor 15 by an amplification factor G2 greater than the amplification factor G1 to generate an amplified signal Sd2. Based on the amplified signal Sd2, it determines whether or not the touch sensor 15 has been touched by an indicator.

Description

Technical Field

[0001] The present disclosure relates to a touch panel, a display device, and a method for controlling a touch panel.

Background Art

[0002] The protection film detection method described in Patent Document 1 obtains the signal change level of a touch screen, and determines that a protection film is attached to the touch screen when the difference between the signal change level of the touch screen and the signal change level of a reference touch screen is less than or equal to a preset threshold value.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When a protection film (filter) is attached to a touch screen (touch panel), a protection film is disposed between an indicator and a touch sensor, so that the distance between the indicator and the touch sensor increases. In this case, there is a problem that the magnitude of the signal from the touch sensor decreases and the sensitivity of touch detection in the touch panel decreases.

[0005] Therefore, the present disclosure has been made to solve the above problems, and an object thereof is to provide a touch panel, a display device, and a method for controlling a touch panel that enable touch detection by a touch sensor with appropriate sensitivity regardless of the presence or absence of a filter.

Means for Solving the Problems

[0006] To solve the above problems, the touch panel according to the first embodiment comprises a touch sensor that forms capacitance with an indicator and a control circuit. The control circuit determines, based on a signal from the touch sensor, whether or not a filter is placed between the touch sensor and the indicator. If it determines that no filter is placed between the touch sensor and the indicator, it amplifies the signal from the touch sensor by a first amplification factor to generate a first amplified signal. Based on the first amplified signal, it determines whether or not the indicator has touched the touch sensor. If it determines that a filter is placed between the touch sensor and the indicator, it amplifies the signal from the touch sensor by a second amplification factor greater than the first amplification factor to generate a second amplified signal. Based on the second amplified signal, it determines whether or not the indicator has touched the touch sensor.

[0007] The display device according to the second embodiment comprises a touch panel according to the first embodiment and a display arranged on top of the touch panel.

[0008] A third embodiment of the touch panel control method is a touch panel control method comprising a touch sensor that forms capacitance with an indicator, wherein, based on a signal from the touch sensor, it is determined whether or not a filter is placed between the touch sensor and the indicator; if it is determined that the filter is not placed between the touch sensor and the indicator, the signal from the touch sensor is amplified by a first amplification factor to generate a first amplified signal; based on the first amplified signal, it is determined whether or not the indicator has touched the touch sensor; if it is determined that the filter is placed between the touch sensor and the indicator, the signal from the touch sensor is amplified by a second amplification factor greater than the first amplified signal to generate a second amplified signal; and based on the second amplified signal, it is determined whether or not the indicator has touched the touch sensor. [Effects of the Invention]

[0009] With the above configuration, touch detection by the touch sensor can be performed with appropriate sensitivity, regardless of whether a filter is used or not. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a schematic perspective view showing the configuration of the information terminal 100 in the first embodiment. [Figure 2] Figure 2 is a schematic perspective view showing the configuration of the information terminal 100 in the first embodiment. [Figure 3] Figure 3 is a schematic cross-sectional view showing the configuration of the information terminal 100 in the first embodiment. [Figure 4] Figure 4 is a schematic cross-sectional view showing the configuration of the information terminal 100 in the first embodiment. [Figure 5] Figure 5 is a block diagram illustrating the configuration of each part of the information terminal 100 according to the first embodiment. [Figure 6] Figure 6 is a schematic diagram showing the structure of the active matrix substrate 1. [Figure 7] Figure 7 is a diagram illustrating the amplified signal when the filter 10a is placed on the touch panel 10 and the amplified signal when the filter 10a is not placed on the touch panel 10. [Figure 8] Figure 8 is a flowchart illustrating the process of determining the amplification factor by the information terminal 100 according to the first embodiment. [Figure 9] Figure 9 is a flowchart illustrating the process of detecting the touch position by the information terminal 100 according to the first embodiment. [Figure 10] Figure 10 is a block diagram showing the configuration of the information terminal 200 according to the second embodiment. [Figure 11] Figure 11 is a flowchart illustrating the operation of the information terminal 200 according to the second embodiment. [Figure 12] Figure 12 is a block diagram showing the configuration of the information terminal 300 according to the third embodiment. [Figure 13]FIG. 13 is a diagram showing an example of display on the touch panel 310 by the display control circuit 325 according to the third embodiment. [Figure 14] FIG. 14 is a diagram for explaining the calibration mode according to the third embodiment. [Figure 15] FIG. 15 is a diagram for explaining the calibration mode according to the third embodiment. [Figure 16] FIG. 16 is a flowchart for explaining the operation of the touch panel according to a modification of the first to third embodiments.

Mode for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present disclosure will be described based on the drawings. Note that the present disclosure is not limited to the following embodiments, and design changes can be appropriately made within the scope that satisfies the configuration of the present disclosure. Also, in the following description, the same parts or parts having the same functions are commonly used with the same reference numerals among different drawings, and the repeated description thereof will be omitted. Further, each configuration described in the embodiments and modifications may be appropriately combined or changed within the scope not departing from the gist of the present disclosure. Also, for the sake of clarity of explanation, in the drawings referred to below, the configuration is shown in a simplified or schematic manner, or some of the constituent members are omitted.

[0012] [First Embodiment] (Overall Configuration of Information Terminal 100) FIG. 1 and FIG. 2 are perspective views schematically showing the configuration of the information terminal 100 in the first embodiment. FIGS. 3 and 4 are cross-sectional views schematically showing the configuration of the information terminal 100 in the first embodiment. The information terminal 100 according to the first embodiment is configured as, for example, a personal computer, a tablet terminal, a smartphone, a smartwatch, or the like. As shown in FIG. 1, the information terminal 100 includes a touch panel 10. Further, as shown in FIG. 2, the information terminal 100 includes a filter 10a. As shown in FIG. 3, the filter 10a is disposed so as to overlap the touch panel 10. The filter 10a is, for example, a privacy filter, and limits the angle at which light from the touch panel 10 passes through the filter 10a. The filter 10a is configured to be detachable from the touch panel 10.

[0013] The touch panel 10 has a function of detecting a touch by an indicator F (see FIG. 3) and a function as a display for displaying an image. For example, the touch panel 10 is an in-cell touch panel. The touch panel 10 includes a touch sensor 15. The touch sensor 15 functions as an electrode (common electrode) in the display, and drives the liquid crystal in the touch panel 10 by generating an electric field between the touch sensor 15 and a pixel electrode 14 (see FIG. 6) disposed opposite to the touch sensor 15. That is, the touch panel 10 and the display are integrally arranged overlapping each other.

[0014] When the filter 10a shown in Figure 3 is placed on the touch panel 10, the distance D1 between the indicator F and the touch sensor 15 is larger than the distance D2 shown in Figure 4 when the filter 10a is not placed on the touch panel 10. Therefore, when the filter 10a is placed on the touch panel 10, the capacitance between the touch sensor 15 and the indicator F is smaller than when the filter 10a is not placed. As a result, the signal from the touch sensor 15 becomes smaller. Therefore, in the touch panel 10 according to the first embodiment, it is determined whether or not the filter 10a is placed between the touch sensor 15 and the indicator F. When the touch panel 10 determines that the filter 10a is not placed between the touch sensor 15 and the indicator F, it amplifies the signal from the touch sensor 15 by an amplification factor G1 to generate an amplified signal Sd1, and determines whether or not the indicator F has touched the touch sensor 15 based on the amplified signal Sd1. Furthermore, if the touch panel 10 determines that a filter 10a is placed between the touch sensor 15 and the indicator F, it amplifies the signal from the touch sensor 15 with an amplification factor G2 that is greater than the amplification factor G1 to generate an amplified signal Sd2, and determines whether or not the indicator F has touched the touch sensor 15 based on the amplified signal Sd2.

[0015] With this configuration, when a filter 10a is placed between the touch sensor 15 and the indicator F, the presence or absence of a touch is determined based on the amplified signal Sd2, which is amplified by the amplification factor G2 from the signal from the touch sensor 15. Therefore, even when a filter 10a is provided on the touch panel 10, the sensitivity of touch detection can be improved. Furthermore, when a filter 10a is not placed between the touch sensor 15 and the indicator F, an amplified signal Sd1 is generated, which is amplified by the amplification factor G1. As a result, the amplified signal Sd1 does not become too large (the signal value does not saturate). This allows touch detection by the touch sensor 15 to be performed with appropriate sensitivity, regardless of whether a filter 10a is present or not.

[0016] (Configuration of each part of the information terminal 100) Figure 5 is a block diagram illustrating the configuration of each part of the information terminal 100 according to the first embodiment. The information terminal 100 comprises an active matrix board 1, a control board 2, and a flexible printed circuit board 3 connecting the active matrix board 1 and the control board 2. Multiple touch sensors 15 are arranged on the active matrix board 1. The multiple touch sensors 15 are arranged, for example, in a matrix. Circuits 17 are also arranged on the active matrix board 1. Circuits 17 are connected to each of the multiple touch sensors 15 via wiring 16.

[0017] The control board 2 includes a timing control circuit 21, a touch detection control circuit 22, a backlight drive circuit 23, and a power supply circuit 24. The timing control circuit 21 is a circuit that controls the operating timing of the touch detection control circuit 22, the gate drive circuit 18, and the source drive circuit 19. The timing control circuit 21 transmits control signals to the touch detection control circuit 22, the gate drive circuit 18, and the source drive circuit 19 so that the period for performing control processing to detect a touch and the period for performing processing to display are time-division multiplexed. Here, the capacitance of the touch sensor 15 changes due to capacitive coupling with the indicator. The touch detection control circuit 22 supplies touch drive signals (pulse signals) to multiple touch sensors 15 during the period for performing processing to detect a touch. The waveform of the pulse signal changes depending on the magnitude of the capacitance of the touch sensor 15. Circuit 17 is an analog front end that converts the signals (analog signals) from the touch sensors 15 into digital signals and removes noise using a noise filter. Then, circuit 17 transmits the noise-removed signals to the touch detection control circuit 22. The touch detection control circuit 22 acquires the difference between the noise-removed signal and the signal for the non-touched state that has been stored in advance (hereinafter referred to as the "detection signal"), amplifies the detection signal, and acquires the amplified signal.

[0018] The backlight driver circuit 23 supplies power to a backlight (not shown) located within the touch panel 10 for at least a portion of the period within one cycle of the vertical synchronization signal, thereby illuminating the backlight. The power supply circuit 24 supplies power from a battery (not shown) to various parts within the touch panel 10.

[0019] Figure 6 is a schematic diagram showing the structure of the active matrix substrate 1. As shown in Figure 6, the active matrix substrate 1 has a plurality of gate lines 11 connected to a gate drive circuit 18 and a plurality of source lines 12 connected to a source drive circuit 19. The plurality of gate lines 11 and the plurality of source lines 12 are arranged to intersect, and pixels are arranged in each region demarcated by the plurality of gate lines 11 and the plurality of source lines 12. The plurality of pixels are arranged in a matrix on the active matrix substrate 1.

[0020] Furthermore, each pixel is provided with a transistor 13 and a pixel electrode 14. The gate electrode of transistor 13 is connected to the gate line 11. The source electrode of transistor 13 is connected to the source line 12. The drain electrode of transistor 13 is connected to the pixel electrode 14.

[0021] When the transistor 13 is turned on by a drive signal (gate signal) supplied from the gate drive circuit 18 via the gate line 11, a source signal supplied from the source drive circuit 19 via the source line 12 is written to (charged) the pixel electrode 14. This creates an electric field between the pixel electrode 14 and the touch sensor 15. A liquid crystal (not shown) is driven by the electric field generated between the pixel electrode 14 and the touch sensor 15, allowing light from the backlight to pass through and display an image on the touch panel 10. In other words, the touch sensor 15 also serves as an electrode (common electrode) for the display. The touch panel 10 is a self-capacitive touch panel. However, it is not limited to this example, and the touch panel 10 may be configured as a mutual-capacitive touch panel.

[0022] (Operation of the information terminal 100 according to the first embodiment) The operation of the information terminal 100 according to the first embodiment will be described with reference to Figures 7 to 9. Figure 7 is a diagram illustrating the amplified signal when a filter 10a is placed on the touch panel 10 and the amplified signal when a filter 10a is not placed on the touch panel 10. Figure 8 is a flowchart illustrating the process of determining the amplification factor by the information terminal 100 according to the first embodiment. Figure 9 is a flowchart illustrating the process of detecting the touch position by the information terminal 100 according to the first embodiment. In the first embodiment, the process of determining the amplification factor shown in Figure 8 is performed by the touch detection control circuit 22.

[0023] When the touch panel 10 is touched by the indicator F without a filter 10a, the detection signal is defined as Sw0. The magnitude of the amplified signal, which is the detection signal Sw0 amplified by the amplification factor G1, is defined as Sc (=Sw0 × G1). Hereafter, this magnitude of the amplified signal will be referred to as the reference value Sc. As shown in Figure 7, the reference value Sc is greater than the threshold Sth used to determine that a touch has occurred. Furthermore, if the magnitude of the signal (amplified signal) from the touch sensor 15 closest to the indicator F among the multiple touch sensors 15 is greater than or equal to the reference value Sc, then not only the signal (amplified signal) from the touch sensor 15 closest to the indicator F, but also the signals (amplified signals) from the multiple touch sensors 15 surrounding that touch sensor 15 will be within the dynamic range. The dynamic range is, for example, in the case of 9-bit (0 to 511) quantization, the range is 5 to 320. This allows for accurate detection of the position touched by the indicator F (hereinafter referred to as "touch position") by calculating the centroid position of the signals (amplified signals) from multiple touch sensors 15 (centroid calculation). The reference value Sc is a value within the dynamic range.

[0024] Here, there are various types of filters 10a, and the user can use the desired filter 10a. Below, we will describe an example in which the first filter 10a is placed on the touch panel 10 and an example in which the second filter 10a is placed on the touch panel 10. When the first filter 10a is placed on the touch panel 10, the detection signal when the touch panel 10 is touched by the indicator F is denoted as Sw1. Also, when the second filter 10a is placed on the touch panel 10, the detection signal when the touch panel 10 is touched by the indicator F is denoted as Sw2. The first filter 10a is thinner than the second filter 10a, and the magnitude of the signal (Sw1 × G1) when the detection signal Sw1 is amplified by the amplification factor G1 is Sc × (1 - β1) (where 0 < β1 < 1). Furthermore, the magnitude of the signal obtained by amplifying the detection signal Sw2 by the amplification factor G1 (=Sw2 × G1) is Sc × (1 - β2) (where 0 < β2 < 1 and β1 < β2).

[0025] When the first filter 10a is placed on the touch panel 10, not only the signal (amplified signal) from the touch sensor 15 closest to the indicator F, but also the signals (amplified signals) from the surrounding touch sensors 15 are within the dynamic range, so it is not necessary to make the amplification factor greater than G1. On the other hand, when the second filter 10a is placed on the touch panel 10, if the amplified signal magnitude is less than or equal to (Sc × (1 - β2)), the signal (amplified signal) from the touch sensor 15 closest to the indicator F exceeds the threshold Sth, but the signals (amplified signals) from the other surrounding touch sensors 15 cannot exceed the threshold Sth, and there is a possibility that they will fall outside the dynamic range. For this reason, when the amplified signal magnitude is less than or equal to Sc × (1 - β2), the accuracy of the calculated touch position decreases.

[0026] (Process to determine the amplification factor) Therefore, in the first embodiment, as shown in Figure 8, the touch panel 10 performs a process to determine the amplification factor. In step S1, an amplified signal Sd1 is obtained by amplifying the detection signal by the amplification factor G1. Then, in step S2, it is determined whether the amplified signal Sd1 is greater than Sc×(1-β2). That is, based on the amplified signal Sd1, it is determined whether a filter 10a (for example, a second filter 10a) that requires a higher amplification factor is placed on the touch panel 10. Note that among the signals (amplified signals Sd1) from the multiple touch sensors 15, the amplified signal Sd1 that is greater than or equal to the threshold Sth is compared with Sc×(1-β2). In step S2, if the amplified signal Sd1 is greater than Sc×(1-β2), the process proceeds to step S3, and if the amplified signal Sd1 is less than or equal to Sc×(1-β2), the process proceeds to step S4. Here, in the first embodiment, if the amplified signal Sd1 is less than or equal to Sc×(1-β2) multiple times in a row, the process proceeds to step S4. For example, if the amplified signal Sd1 is less than or equal to Sc × (1 - β2) for multiple (e.g., 10) consecutive frame periods, the process proceeds to step S4. This prevents incorrect judgments from being made when the amplified signal Sd1 is less than or equal to Sc × (1 - β2) only once due to noise or other factors.

[0027] In step S3, the amplification factor is determined to be G1, and the process returns to step S1. That is, it is determined that there is no filter 10a (a filter that requires a high amplification factor) between the touch sensor 15 and the indicator F. In this case, the presence or absence of a touch by the indicator F on the touch sensor 15 is determined based on the amplified signal Sd1 amplified by the amplification factor G1 (see Figure 9).

[0028] In step S4, the amplification factor is determined to be G3, and the process proceeds to step S5. That is, it is determined that a filter 10a (a filter that requires a high amplification factor) is placed between the touch sensor 15 and the indicator F. In this case, the presence or absence of a touch by the indicator F on the touch sensor 15 is determined based on the amplified signal Sd2, which is amplified by the amplification factor G2 (see Figure 9).

[0029] In step S5, an amplified signal Sd2 is obtained by amplifying the detection signal with an amplification factor G2. Here, if the filter 10a is removed from the touch panel 10, the detection signal becomes large to Sw0. When the detection signal Sw0 is amplified with an amplification factor G2, as shown in Figure 7, the amplified signal Sd2 becomes much larger than the reference value Sc, and the amplified signal Sd2 may become the upper limit of the detectable range (the signal value may saturate). In this case, it may not be possible to calculate the correct position when calculating the touch position (when calculating the centroid).

[0030] Therefore, in the first embodiment, in step S6, it is determined whether the amplified signal Sd2 is greater than Sca. Of the signals (amplified signals Sd2) from the multiple touch sensors 15, the amplified signal Sd2 that is greater than or equal to the threshold Sth is compared with Sca. Sca is a value greater than the reference value Sc, for example, Sca is a value greater than the appropriate dynamic range (for example, in the case of 9 bits, it is a magnitude of about 511). If the amplified signal Sd2 is greater than Sca, the process proceeds to step S7, and the amplification factor is returned to G1. That is, if the amplified signal Sd2 is greater than Sca, it is determined that the filter 10a has been removed, and the amplification factor is returned to G1. This prevents the amplified signal Sd2 from becoming the upper limit of the detectable range (prevents signal saturation), and allows for accurate calculation of the touch position (allows for accurate calculation of the centroid). After step S7, the process returns to step S1. In the first embodiment, if the amplified signal Sd2 is greater than Sca multiple times in a row (for example, for 10 consecutive frames), the process proceeds to step S7 and the amplification factor is returned to G1. This prevents incorrect judgments from being made when the amplified signal Sd2 becomes greater than Sca only once due to noise or the like.

[0031] Furthermore, if the amplified signal Sd2 is less than or equal to Sca, the process proceeds to step S8, where the amplification factor remains at the G2 state. After that, the process returns to step S5.

[0032] (Process to calculate touch position) As shown in Figure 9, in step S11, if the amplification factor determined in the amplification factor determination process is G1, the amplified signal Sd1 is acquired, and if the amplification factor determined in the amplification factor determination process is G2, the amplified signal Sd2 is acquired. Then, a map is generated in which the coordinates of each of the multiple touch sensors 15 are associated with the amplified signal Sd1 of each of the multiple touch sensors 15. Then, in step S12, the centroid position in the map is calculated (centroid calculation), and the calculated centroid position is detected as the touch position. In step S13, a report including the detected touch position is sent to a host controller (control circuit on the information terminal 100 side), which is not shown. After that, the process returns to step S11.

[0033] According to the first embodiment, when a filter 10a is placed between the touch sensor 15 and the indicator F, the presence or absence of a touch is determined based on an amplified signal Sd2, which is amplified by an amplification factor G2 greater than the amplification factor G1. Therefore, even when a filter 10a is provided on the touch panel 10, the sensitivity of touch detection can be improved. Furthermore, when a filter 10a is not placed between the touch sensor 15 and the indicator F, an amplified signal Sd1 is generated by an amplification factor G1, so the amplified signal Sd1 does not become too large (the signal value does not saturate). As a result, touch detection by the touch panel 10 can be performed with appropriate sensitivity regardless of the presence or absence of a filter 10a.

[0034] Here, a configuration can be considered in which the threshold Sth is lowered when a filter 10a is placed between the touch sensor 15 and the indicator F. However, even when the threshold Sth is lowered, if the signals (amplified signals) from the multiple touch sensors 15 surrounding the touch sensor 15 closest to the indicator F fall outside the dynamic range, the number of signals from the touch sensors 15 that can be used for centroid calculation decreases, thus reducing the accuracy of touch position detection. In contrast, according to the first embodiment, when a filter 10a is placed between the touch sensor 15 and the indicator F, the amplification factor is increased from G1 to G2, so that the signals (amplified signals) from the multiple surrounding touch sensors 15 also fall within the dynamic range. As a result, the accuracy of touch position detection can be improved compared to the configuration in which the threshold Sth is lowered.

[0035] [Second Embodiment] Next, the configuration of the information terminal 200 according to the second embodiment will be described with reference to Figures 10 and 11. In the second embodiment, the information terminal 200 is standardly equipped with a filter 10a (see Figure 2), and the user can remove the filter 10a. Components similar to those in the first embodiment will be given the same reference numerals as in the first embodiment, and their description will be omitted.

[0036] Figure 10 is a block diagram showing the configuration of an information terminal 200 according to the second embodiment. As shown in Figure 10, the information terminal 200 according to the second embodiment includes a touch panel 210. The touch panel 210 includes a control board 202 equipped with a touch detection control circuit 222.

[0037] Figure 11 is a flowchart illustrating the operation of the information terminal 200 according to the second embodiment. The operation (control processing) of the information terminal 200 is performed by the touch detection control circuit 222. In the information terminal 200, first, an amplified signal Sd2 is acquired in step S105. The operation of steps S105 to S108 is the same as that of steps S5 to S8, so the explanation is omitted. After step S108, step S101 is executed. The operation of steps S101 to S104 is the same as that of steps S1 to S4, so the explanation is omitted. According to the second embodiment, even when the standard state is that the filter 10a is placed between the touch sensor 15 and the indicator F, it is possible to detect that the filter 10a has been removed, so that touch detection by the touch sensor 15 can be performed with appropriate sensitivity. Other configurations and effects of the second embodiment are the same as those of the first embodiment.

[0038] [Third Embodiment] Next, the configuration of the information terminal 300 according to the third embodiment will be described with reference to Figures 12 to 15. In the third embodiment, the information terminal 300 is configured to start a calibration mode in response to user operation and to correct the amplification ratio based on the signal (amplified signal) from the touch sensor 15 acquired during the execution of the calibration mode. Components similar to those in the first embodiment will be given the same reference numerals as in the first embodiment and their description will be omitted.

[0039] Figure 12 is a block diagram showing the configuration of an information terminal 300 according to the third embodiment. As shown in Figure 12, the information terminal 300 according to the third embodiment includes a touch panel 310. The touch panel 310 includes a control board 302 equipped with a touch detection control circuit 322 and a display control circuit 325.

[0040] Figure 13 shows an example of display on the touch panel 310 by the display control circuit 325 according to the third embodiment. The display control circuit 325 displays a settings screen on the touch panel 310. By performing input operations on the settings screen, the user can configure each device (including the touch panel 310) installed in the information terminal 300. The display control circuit 325 starts a calibration mode in response to the user's operation on the "Touch Panel Adjustment" image (button). Calibration mode means a state in which processing is performed to correct the amplification factor.

[0041] Figures 14 and 15 illustrate the calibration mode according to the third embodiment. As shown in Figure 14, the display control circuit 325 displays marks 301 at multiple locations on the touch panel 310 and displays a message (for example, "Please touch the marks firmly.") in calibration mode. The multiple marks 301 are displayed at positions on the touch panel 310 that are spaced apart from each other. Each of the multiple marks 301 has the same dimensions as one of the touch sensors 15. That is, in a plan view, the vertical and horizontal dimensions of the marks 301 are the same as those of the touch sensor 15. Each of the multiple marks 301 is displayed at a position that overlaps with any one of the multiple touch sensors 15 in a plan view. That is, the marks 301 are displayed at a position that does not shift relative to the touch sensor 15. As a result, the signal from one of the touch sensors 15 becomes dominant among the detection signals, making it easy to compare signal strengths and correct the amplification factor. For example, the multiple marks 301 are displayed near the four corners of the touch panel 310 and in the center of the touch panel 310.

[0042] As shown in Figure 15, the touch detection control circuit 322 amplifies the detection signal Sw12 from the touch sensor 15 corresponding to the coordinates of the mark 301 by an amplification factor G11 and obtains an amplified signal Sd11. It calculates the average value Sd0 of the amplified signals Sd11 from all of the marks 301. The touch detection control circuit 322 then determines the amplification factor G12 such that the average value Sd0 becomes the reference value Sc. That is, the touch detection control circuit 322 determines an amplification factor G12 such that amplification factor G12 = (reference value Sc / detection signal Sw12). Thus, in the third embodiment, when the touch detection control circuit 322 determines that a filter 10a is placed between the touch sensor 15 and the indicator F, it determines a larger amplification factor G12 the larger the difference between the average value Sd0 and the reference value Sc. The touch detection control circuit 322 then detects the touch position using the amplified signal Sd12, which is the detection signal Sw12 amplified by the amplification factor G12. As a result, even if the type of filter 10a is changed, the amplification factor G11 can be corrected to the amplification factor G12, so that touch detection can be performed with appropriate sensitivity. Furthermore, since the amplification factor is corrected based on signals from touch sensors 15 at multiple locations, the amplification factor can be corrected to a value that reflects various touch conditions. The other configurations and effects of the third embodiment are the same as those of the first embodiment.

[0043] [Differentiation] Although embodiments of the invention have been described above, these embodiments are merely examples for carrying out the invention. Therefore, it is possible to carry out the invention by appropriately modifying the embodiments described above without departing from the spirit of the invention, without being limited to the embodiments described above. Modifications of the embodiments described above will be described below.

[0044] (1) In the first to third embodiments described above, examples were shown in which the touch panel (and display device) is provided on an information terminal, but the disclosure is not limited thereto. The touch panel may be placed on a display device other than the information terminal, and the touch panel does not need to have a display function.

[0045] (2) In the first to third embodiments described above, an example was shown in which the filter is configured as a privacy filter, but the disclosure is not limited thereto. For example, the filter may be configured as a protective filter to protect the touch panel from scratches, or as a filter that blocks light of certain wavelengths (blue light cut filter).

[0046] (3) In the first to third embodiments described above, an example was shown in which G1 or G2, which is equal to the amplification factor used when determining the presence or absence of a filter (steps S2, S6, S102, S106), is used, but the disclosure is not limited thereto. The amplification factor when determining the presence or absence of a filter (steps S2, S6, S102, S106) may be set to a value other than G1 or G2.

[0047] (4) In the third embodiment described above, an example was shown in which marks are displayed on the touch panel at multiple positions in calibration mode, but the disclosure is not limited thereto. For example, only one mark may be displayed on the touch panel.

[0048] (5) In the first to third embodiments described above, examples were shown in which the process of determining whether or not a filter is present and the process of determining the amplification factor are performed by the touch detection control circuit, but the disclosure is not limited thereto. For example, these processes may be performed by a control circuit other than the touch detection control circuit (for example, a host controller, or a dedicated calibration circuit provided separately from the touch detection control circuit).

[0049] (6) In the first to third embodiments described above, examples were shown in which the amplified signal and a predetermined value are compared multiple times and the presence or absence of a filter is determined based on the result (determination of the amplification factor), but the disclosure is not limited thereto. For example, the amplified signal and a predetermined value may be compared only once and the presence or absence of a filter is determined based on the result (determination of the amplification factor).

[0050] (7) In the first to third embodiments described above, an example was shown in which the touch panel is configured as an in-cell touch panel, but the disclosure is not limited thereto. For example, it may be configured as an on-cell type touch panel or as an out-cell type touch panel.

[0051] (8) In the first embodiment described above, an example was shown in which the amplified signal Sd1 is compared with only one threshold (Sc(1-β2)), but the disclosure is not limited thereto. That is, the amplified signal Sd1 may be compared with multiple thresholds, and the amplification factor may be determined based on the results. For example, as in the modified touch panel shown in Figure 16, in step S2, if the amplified signal Sd1 is greater than Sc(1-β2), in step S201, the amplified signal Sd1 is compared with Sc(1-β1), and in step S202, the amplification factor may be set to G1 if the amplified signal Sd1 is greater than or equal to Sc(1-β1), and in step S203, the amplification factor may be set to G3, which is greater than G1 and less than G2.

[0052] The above configuration can also be explained as follows:

[0053] The touch panel according to the first configuration comprises a touch sensor that forms capacitance with an indicator and a control circuit, wherein the control circuit determines, based on a signal from the touch sensor, whether or not a filter is placed between the touch sensor and the indicator, and if it determines that the filter is not placed between the touch sensor and the indicator, it amplifies the signal from the touch sensor by a first amplification factor to generate a first amplified signal, and determines, based on the first amplified signal, whether or not the indicator has touched the touch sensor, and if it determines that the filter is placed between the touch sensor and the indicator, it amplifies the signal from the touch sensor by a second amplification factor greater than the first amplification factor to generate a second amplified signal, and determines, based on the second amplified signal, whether or not the indicator has touched the touch sensor (first configuration).

[0054] According to the first configuration described above, when a filter is placed between the touch sensor and the indicator, the presence or absence of a touch is determined based on a second amplified signal, which is amplified by a second amplification factor greater than the first amplification factor, even when a filter is provided on the touch panel. Therefore, the sensitivity of touch detection can be improved. Furthermore, when no filter is placed between the touch sensor and the indicator, a first amplified signal is generated, which is amplified by the first amplification factor, so the first amplified signal does not become too large (the signal value does not saturate). As a result, touch detection by the touch sensor can be performed with appropriate sensitivity, regardless of whether a filter is present or not.

[0055] Here, one might consider a configuration in which a filter is placed between the touch sensor and the indicator to lower the threshold for detecting a touch. However, even if the threshold is lowered, if the signals (amplified signals) from multiple touch sensors surrounding the touch sensor closest to the indicator fall outside the dynamic range, the number of touch sensor signals available for centroid calculation decreases, thus reducing the accuracy of touch position detection. In contrast, with the first configuration, if a filter is placed between the touch sensor and the indicator, the amplification factor is increased, so that the signals (amplified signals) from the surrounding multiple touch sensors also fall within the dynamic range. As a result, the accuracy of touch position detection can be improved compared to the configuration in which the threshold is lowered.

[0056] In the first configuration, the control circuit may be configured to generate a third amplified signal by amplifying the signal from the touch sensor by a third amplification factor, and to determine that the filter is placed between the touch sensor and the indicator when the third amplified signal is greater than or equal to a first threshold which is the threshold for touch detection, and less than or equal to a second threshold which is greater than the first threshold (second configuration).

[0057] In this case, if a filter is placed between the touch sensor and the indicator, the signal from the touch sensor is strong enough to detect a touch (above the first threshold), but not strong enough (below the second threshold). In this case, because the signal from the touch sensor is not strong enough, the accuracy of the touch position calculated by calculating the centroid at multiple locations decreases. In contrast, according to the second configuration described above, even if the signal from the touch sensor (third amplified signal) is above the first threshold, which is the threshold for touch detection, if it falls below the second threshold, it is determined that a filter is placed between the touch sensor and the indicator, thus preventing a decrease in the accuracy of the calculated touch position.

[0058] In the second configuration, the control circuit may be configured to generate a third amplified signal by amplifying the signal from the touch sensor by a third amplification factor, and to determine that the filter is placed between the touch sensor and the indicator when the third amplified signal is greater than or equal to a first threshold which is the threshold for touch detection, and less than or equal to a second threshold which is greater than the first threshold, and to determine that the filter is not placed between the touch sensor and the indicator when the third amplified signal is greater than the second threshold (third configuration).

[0059] According to the third configuration described above, even if the third amplified signal becomes above the first threshold and below the second threshold only once due to noise or the like, it is possible to prevent an incorrect judgment from being made.

[0060] In any one of the first to third configurations, the control circuit may be configured to determine that the filter is placed between the touch sensor and the indicator when the third amplified signal, which is greater than or equal to the first threshold and less than or equal to the second threshold, is acquired a predetermined number of times consecutively, and to determine that the filter is not placed between the touch sensor and the indicator when the third amplified signal, which is greater than or equal to the first threshold and less than or equal to the second threshold, is not acquired a predetermined number of times consecutively (fourth configuration).

[0061] According to the fourth configuration described above, the second amplification factor can be determined according to the amount of change (decrease) in the signal from the touch sensor relative to the reference value. As a result, the second amplification factor can be determined to an appropriate value.

[0062] In the second or third configuration, the control circuit may be configured to determine that the filter has been removed between the touch sensor and the indicator when, after determining that the filter is placed between the touch sensor and the indicator, the second amplified signal becomes greater than a third threshold which is greater than the second threshold (fifth configuration).

[0063] According to the fifth configuration described above, even if the filter is removed between the touch sensor and the indicator, it is possible to detect that the filter is not present.

[0064] In any one of the first to fifth configurations, the control circuit may be configured to amplify the signal from the touch sensor by a fourth amplification factor greater than the first amplification factor to generate a fourth amplified signal, determine that the filter has been removed when the fourth amplified signal becomes greater than the fourth threshold, and determine that the filter is present when the fourth amplified signal becomes less than or equal to the fourth threshold (sixth configuration).

[0065] According to the sixth configuration described above, even when a filter is typically placed between the touch sensor and the indicator, it is possible to detect when the filter has been removed, thereby enabling touch detection by the touch sensor with appropriate sensitivity.

[0066] In any one of the first to sixth configurations, the control circuit may be configured to initiate a calibration mode in response to user operation and to correct the second amplification factor based on the signal from the touch sensor acquired during the execution of the calibration mode (seventh configuration).

[0067] According to the seventh configuration described above, even if the type of filter is changed, the second amplification factor can be corrected, so that touch detection by the touch sensor can be performed with appropriate sensitivity.

[0068] In the eighth configuration, the control circuit may be configured to correct the second amplification factor based on the signals from the touch sensor that are output when the indicator is touched at each of a plurality of distant locations on the touch sensor while the calibration mode is being performed (eighth configuration).

[0069] Here, the touch state (angle and contact area) of the indicator changes depending on the touch position. In contrast, according to the eighth configuration described above, the second amplification factor is corrected based on signals from touch sensors at multiple positions, so the second amplification factor can be corrected to a value that reflects various touch states.

[0070] The display device according to the ninth configuration comprises a touch panel from any one of the first to eighth configurations and a display placed on top of the touch panel (the ninth configuration).

[0071] According to the ninth configuration described above, a display device can be provided that can perform touch detection by a touch sensor with appropriate sensitivity, regardless of whether a filter is present or not.

[0072] The tenth configuration of the touch panel control method is a touch panel control method comprising a touch sensor that forms capacitance with an indicator, wherein, based on a signal from the touch sensor, it is determined whether or not a filter is placed between the touch sensor and the indicator; if it is determined that the filter is not placed between the touch sensor and the indicator, the signal from the touch sensor is amplified by a first amplification factor to generate a first amplified signal; based on the first amplified signal, it is determined whether or not the indicator has touched the touch sensor; if it is determined that the filter is placed between the touch sensor and the indicator, the signal from the touch sensor is amplified by a second amplification factor greater than the first amplification factor to generate a second amplified signal; and based on the second amplified signal, it is determined whether or not the indicator has touched the touch sensor (tenth configuration).

[0073] According to the above-described 10th configuration, it is possible to provide a touch panel control method that enables touch detection by a touch sensor with appropriate sensitivity, regardless of whether a filter is present or not. [Explanation of symbols]

[0074] 1: Active matrix board, 2: Control board, 3: Flexible printed circuit board, 10: Touch panel, 10a: Filter, 11: Gate line, 12: Source line, 13: Transistor, 14: Pixel electrode, 15: Touch sensor, 16: Wiring, 17: Circuit, 18: Gate drive circuit, 19: Source drive circuit, 21: Timing control circuit, 22: Touch detection control circuit, 23: Backlight drive circuit, 24: Power supply circuit, 100: Information terminal, 200: Information terminal, 202: Control board, 210: Touch panel, 222: Touch detection control circuit, 300: Information terminal, 301: Marker, 302: Control board, 310: Touch panel, 322: Touch detection control circuit, 325: Display control circuit

Claims

1. A touch sensor that forms capacitance with an indicator, Equipped with a control circuit, The aforementioned control circuit is Based on the signal from the touch sensor, it is determined whether or not a filter is placed between the touch sensor and the indicator. If it is determined that the filter is not placed between the touch sensor and the indicator, the signal from the touch sensor is amplified by a first amplification factor to generate a first amplified signal, and based on the first amplified signal, it is determined whether or not the indicator has touched the touch sensor. A touch panel that, when it is determined that the filter is placed between the touch sensor and the indicator, amplifies the signal from the touch sensor by a second amplification factor greater than the first amplification factor to generate a second amplified signal, and determines whether or not the indicator has touched the touch sensor based on the second amplified signal.

2. The aforementioned control circuit is The signal from the touch sensor is amplified by a third amplification factor to generate a third amplified signal. When the third amplified signal is greater than or equal to a first threshold, which is the threshold for touch detection, and less than or equal to a second threshold that is greater than the first threshold, it is determined that the filter is placed between the touch sensor and the indicator. The touch panel according to claim 1, wherein if the third amplified signal is greater than the second threshold, it is determined that the filter is not placed between the touch sensor and the indicator.

3. The aforementioned control circuit is When the third amplified signal, which is above the first threshold and below the second threshold, is acquired a predetermined number of times consecutively, it is determined that the filter is placed between the touch sensor and the indicator. The touch panel according to claim 2, wherein if the third amplified signal, which is above the first threshold and below the second threshold, is not acquired a predetermined number of times consecutively, it is determined that the filter is not placed between the touch sensor and the indicator.

4. The touch panel according to any one of claims 1 to 3, wherein the control circuit determines that the filter is placed between the touch sensor and the indicator, and the larger the difference between the signal from the touch sensor and the reference value, the larger the second amplification factor.

5. The touch panel according to claim 2, wherein the control circuit determines that the filter is placed between the touch sensor and the indicator, and then determines that the filter has been removed between the touch sensor and the indicator when the second amplified signal becomes greater than a third threshold which is greater than the second threshold.

6. The aforementioned control circuit is The signal from the touch sensor is amplified by a fourth amplification factor greater than the first amplification factor to generate a fourth amplified signal, and when the fourth amplified signal becomes greater than the fourth threshold, it is determined that the filter has been removed. The touch panel according to claim 1, wherein it is determined that the filter is installed when the fourth amplified signal falls below the fourth threshold.

7. The aforementioned control circuit is The calibration mode is initiated in response to user input. The touch panel according to claim 1, wherein the second amplification factor is determined based on the signal from the touch sensor acquired during the execution of the calibration mode.

8. The touch panel according to claim 7, wherein the control circuit determines the second amplification factor based on the signal from the touch sensor that is output when the indicator is touched at each of a plurality of distant positions on the touch sensor while the calibration mode is being executed.

9. The touch panel described in claim 1, A display device comprising a display positioned on top of the aforementioned touch panel.

10. A method for controlling a touch panel, comprising a touch sensor that forms capacitance with an indicator, Based on the signal from the touch sensor, it is determined whether or not a filter is placed between the touch sensor and the indicator. If it is determined that the filter is not placed between the touch sensor and the indicator, the signal from the touch sensor is amplified by a first amplification factor to generate a first amplified signal, and based on the first amplified signal, it is determined whether or not the indicator has touched the touch sensor. A method for controlling a touch panel, which, when it is determined that the filter is placed between the touch sensor and the indicator, amplifies the signal from the touch sensor by a second amplification factor greater than the first amplification factor to generate a second amplified signal, and determines whether or not the indicator touches the touch sensor based on the second amplified signal.

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