Touch panel device
The touch panel device addresses false detections by adjusting baseline values based on capacitance and temperature changes, ensuring accurate position detection without complicating the configuration.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- ALPS ALPINE CO LTD
- Filing Date
- 2022-06-27
- Publication Date
- 2026-05-25
AI Technical Summary
Existing touch panels face false detections during rapid temperature changes due to variations in capacitance, which require a separate proximity detection unit, complicating the configuration.
A touch panel device with a capacitive touch panel having electrodes, capacitance measurement, baseline value setting, position detection, and baseline value correction means that adjusts the baseline value based on capacitance changes and temperature, allowing for a simplified configuration without determining the presence of an indicator.
Prevents false detections during rapid temperature changes by individually adjusting the baseline value for each electrode pair, improving position detection accuracy and simplifying the device configuration.
Smart Images
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Abstract
Description
Technical Field
[0004] ,
[0005] ,
[0001] The present invention relates to a touch panel device for detecting a contact position of an indicator.
Background Art
[0002] Conventionally, there has been known a touch panel that detects the presence or absence of touch of an object such as a finger based on whether the difference between the Raw value, which is the measurement value of a capacitance sensor, and the baseline value is greater than or equal to a threshold value (see, for example, Patent Document 1). This touch panel is provided with a baseline value update unit that updates the baseline value so as to follow the Raw value of the capacitance in order to correct the variation in the capacitance of the capacitance sensor due to temperature changes. Even when the capacitance of the capacitance sensor changes with temperature changes, by changing the baseline value so as to follow this change, false detection in a state where no object is touching is prevented.
Prior Art Documents
Patent Documents
[0003]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0004] Even when updating the baseline value so as to follow the change in capacitance due to temperature changes as in the touch panel disclosed in Patent Document 1 described above, it is necessary to detect a change in capacitance due to the approach of an object. That is, the baseline value needs to change slowly with respect to the approach of an object and change quickly with respect to temperature changes. In the touch panel of Patent Document 1 described above, by detecting the presence or absence of approach of an object using a proximity detection unit, the way the baseline value changes is changed. However, this method has a problem that a separate proximity detection unit is required, leading to a complication of the configuration.
[0005] Generally, a capacitive sensor consists of a sensor conductor and a ground layer, with an OCA (Optical Clear Adhesive) or polarizing layer placed between them. Furthermore, wiring is drawn out adjacent to these layers, so even when the object is not close, the capacitance of the capacitive sensor will not be the same at every location. For this reason, calibration is performed to set a baseline value that matches these non-uniform capacitances.
[0006] However, when a capacitive sensor has different capacitances depending on the location, the degree to which the capacitance changes with temperature will vary. Specifically, the larger the capacitance of the capacitive sensor, the greater the change in capacitance with temperature changes. Therefore, in locations where the capacitance of the capacitive sensor is partially large, if the ambient temperature changes rapidly, the raw value may increase and exceed the baseline value even though no object is actually approaching, leading to a problem of false detection.
[0007] This invention was created in view of the above points, and its purpose is to provide a touch panel device that can prevent false detections during rapid temperature changes caused by variations in capacitance without complicating the configuration. [Means for solving the problem]
[0008] To solve the above-mentioned problems, the present invention provides a touch panel device comprising: a capacitive touch panel having a plurality of electrodes arranged in intersecting directions; a capacitance measuring means for measuring the capacitance between intersecting pairs of electrodes for each electrode pair; a baseline value setting means that, when the indicator is not in contact, sets the capacitance for each electrode pair measured by the capacitance measuring means as a reference capacitance and sets it as a baseline value used for comparing capacitances to detect whether or not the indicator is in contact, prior to detecting the contact position of the indicator; a position detection means for detecting the contact position of the indicator by comparing the capacitance for each electrode pair measured by the capacitance measuring means with the corresponding baseline value; and the contact position of the indicator Non The system includes a baseline value correction means that adjusts the baseline value in accordance with the change in the capacitance of each electrode pair measured by the capacitance measuring means at the time of detection when the capacitance changes over time, and the baseline value correction means adjusts the baseline value. as a period Time X and / or The variation at time X, which is the period for changing the baseline value The upper limit Y is set for each electrode pair according to the reference capacitance of each electrode pair.
[0009] When there are variations in the capacitance of each electrode pair within the touch panel, the baseline value can be changed for each capacitance, thereby preventing false detections during rapid temperature changes caused by these variations. Furthermore, since it is not necessary to determine the presence or absence of an indicator (the object to be detected) when changing the baseline value, the configuration for this determination is unnecessary, allowing for a simplified configuration.
[0010] Furthermore, it is desirable that the baseline value correction means described above sets time X to a small value and / or upper limit Y to a large value when the reference capacitance of each electrode pair is large, and sets time X to a large value and / or upper limit Y to a small value when the reference capacitance of each electrode pair is small. This makes it possible to individually set time X and upper limit Y according to the capacitance of each electrode pair, thereby creating a baseline value suitable for preventing false detections.
[0011] Furthermore, it is desirable that the baseline value correction means described above sets time X and upper limit Y so that when the capacitance of each electrode pair increases in response to the approach of an indicator to the touch panel, the increase in the baseline value corresponding to each electrode pair does not keep pace with this increase in capacitance. This makes it possible to set a baseline value suitable for preventing false detection for each electrode pair with variations in capacitance, thereby improving the accuracy of position detection when an indicator approaches.
[0012] Furthermore, it is desirable to further include a temperature detection means for detecting the ambient temperature around the touch panel, and for the baseline value correction means to change time X and / or upper limit Y when the amount of change in the temperature detected by the temperature detection means over a certain period of time exceeds a predetermined value. This ensures that false detections can be reliably prevented in environments with rapid temperature changes.
[0013] Furthermore, it is desirable that the baseline value correction means described above changes the time X for each electrode pair, which is the period for changing the baseline value, to (A / a)·X, when A is the average capacitance of each electrode pair and a is the individual capacitance of each electrode pair. Alternatively, it is desirable that the baseline value correction means described above changes the upper limit Y for each time X that changes the baseline value to (a / A)·Y, when A is the average capacitance of each electrode pair and a is the individual capacitance of each electrode pair. By specifically changing the time X and the upper limit Y for each electrode pair in this way, false detections in all electrode pairs can be prevented. [Brief explanation of the drawing]
[0014] [Figure 1] This diagram shows the configuration of a touch panel device according to one embodiment. [Figure 2] This figure shows specific examples of the first and second transparent electrodes included in the touch panel. [Figure 3] This figure shows the relationship between temperature changes and raw and baseline values. [Figure 4] This is an explanatory diagram illustrating the operation of correcting the baseline value in normal correction mode. [Figure 5] It is a diagram showing the relationship between the temperature change corresponding to different capacitances and the Raw value. [Figure 6] It is an explanatory diagram when variably setting the update frequency X of the baseline value. [Figure 7] It is an explanatory diagram when variably setting the upper limit value Y at the time of updating the baseline value.
Embodiment for Carrying Out the Invention
[0015] Hereinafter, a touch panel device according to an embodiment to which the present invention is applied will be described with reference to the drawings.
[0016] FIG. 1 is a diagram showing the configuration of a touch panel device according to an embodiment. This touch panel device 100 is, for example, arranged so as to overlap the display screen of a display device, and is for detecting the position on the screen indicated by an indicator such as a finger, and includes a touch panel 110. The touch panel 110 has a position detection area that covers the entire display screen of the display device, and includes a plurality of first transparent electrodes 110A extending along the X-axis direction (horizontal direction) of this position detection area, and a plurality of second transparent electrodes 110B extending along the Y-axis direction (vertical direction).
[0017]
[0018] FIG. 2 is a diagram showing a specific example of the first and second transparent electrodes 110A and 110B included in the touch panel 110. In the example shown in FIG. 2, the first transparent electrode 110A extending in the X-axis direction has a shape in which a plurality of square electrodes arranged such that one diagonal is parallel to the X-axis are arranged along the X-axis and connected to each other. Similarly, the second transparent electrode 110B extending in the Y-axis direction has a shape in which a plurality of square electrodes arranged such that one diagonal is parallel to the Y-axis are arranged along the Y-axis and connected to each other. As shown in FIG. 2, by arranging the connecting portions connecting adjacent square electrodes so as to cross each other, the entire display screen is covered with the square electrodes of the first and second transparent electrodes 110A and 110B. These first and second transparent electrodes 110A and 110B are formed using, for example, an ITO (Indium Tin Oxide) film.
[0019] Also, the touch panel device 100 shown in FIG. 1 includes a capacitance measurement unit 120, switches (SW) 130 and 132, a position detection unit 140, a baseline value setting unit 150, a baseline value storage unit 152, a baseline value correction unit 160, and a temperature sensor (T) 162.
[0020] The capacitance measurement unit 120 measures the capacitance between the first transparent electrode 110A and the second transparent electrode 110B provided on the touch panel 110 while changing their combinations. The change of this combination is performed by switching the switch 130 that selectively connects a plurality of first transparent electrodes 110A and the switch 132 that selectively connects a plurality of second transparent electrodes
[0021] 110B.
[0021] The position detection unit 140 detects the position indicated by a user's finger or other indicator based on the change in the detected capacitance value (Raw value) between the first transparent electrode 110A and the second transparent electrode 110B, which is measured by the capacitance measurement unit 120. In general terms, when the Raw value increases significantly among the Raw values measured while changing the combination of the first transparent electrode 110A and the second transparent electrode 110B, the position where the first transparent electrode 110A and the second transparent electrode 110B intersect in this combination is identified as the position indicated by the indicator.
[0022] The baseline value setting unit 150 performs a calibration operation prior to the position detection operation by the position detection unit 140. With no indicator object in contact with the touch panel 110, it acquires the reference capacitance of the touch panel 110 (capacitance for each combination of the first transparent electrode 110A and the second transparent electrode 110B) measured by the capacitance measurement unit 120 as the baseline value, which is used as the reference for position detection. The position detection unit 140 can determine whether or not the raw value has changed and to what extent by comparing this baseline value with the raw value. The baseline value acquired by the baseline value setting unit 150 is stored in the baseline value storage unit 152.
[0023] The baseline value correction unit 160 appropriately corrects the baseline value stored in the baseline value storage unit 152. For example, it monitors the temperature around the touch panel device 100 detected by the temperature sensor 162, and corrects the baseline value in normal correction mode when the amount of temperature change is below a predetermined value, and in rapid temperature change correction mode when it exceeds the predetermined temperature.
[0024] The capacitance measurement unit 120 described above corresponds to the capacitance measurement means, the baseline value setting unit 150 corresponds to the baseline value setting means, the position detection unit 140 corresponds to the position detection means, the baseline value correction unit 160 corresponds to the baseline value correction means, and the temperature sensor 162 corresponds to the temperature detection means.
[0025] The touch panel device 100 of this embodiment has the above configuration, and its operation, particularly the baseline value correction operation, will now be described.
[0026] (Normal correction mode) First, we will explain the baseline value correction operation in normal correction mode.
[0027] Figure 3 shows the relationship between temperature change and the Raw value and baseline value. In the example shown in Figure 3, the ambient temperature Ta of the touch panel device 100 gradually decreases from 85°C to -40°C. In such a case, even if the indicator is not in contact with the touch panel 110, the Raw value increases to follow the temperature change. The baseline value correction unit 160 performs a correction operation to change the baseline value B in accordance with the increase in the Raw value.
[0028] Figure 4 is an explanatory diagram of the operation for correcting the baseline value in normal correction mode. In Figure 4, X is the update frequency (fixed value), which is the update time interval that changes the baseline value. Y is the amount of change, which is the upper limit (fixed value) that changes the baseline value B. Thus, when the Raw value increases, the baseline value B, which is the reference for position detection, also increases, and the interval of this increase is X, so the baseline value B is changed in a step-like manner each time X time passes. Moreover, the upper limit of the amount of change is Y, and if the increase in the Raw value exceeds Y after time X has passed, a correction operation is performed to increase the baseline value B by Y at that point. Also, if the increase in the Raw value is less than or equal to Y after time X has passed, a correction operation is performed to increase the baseline value B by the amount of this increase in the Raw value.
[0029] When the temperature change is gradual, the baseline value B is modified by this correction operation. In this state, when an object touches the touch panel 110, the Raw value corresponding to the contact position rises sharply. However, since the baseline value B remains fixed until the next update, the change in capacitance, which is the difference between the Raw value and this baseline value B, becomes large, and when it exceeds a predetermined threshold, the position corresponding to this Raw value is detected as the contact position.
[0030] (Temperature change correction mode) The touch panel 110 has sensor conductors (first and second transparent electrodes 110A and 110B) and a ground layer stacked on top of each other, with OCA (Optical Clear Adhesive) and a polarizing layer placed between them. Furthermore, wiring is drawn out adjacent to these layers, so even when the indicator is not nearby, the capacitance of the touch panel 110 will not be the same at each location. For this reason, the baseline value setting unit 150 performs calibration to set the baseline value to match these non-uniform capacitances.
[0031] However, the degree of change in the Raw value in response to temperature changes is determined by the magnitude of the capacitance at each location on the touch panel 110 and is not constant. Figure 5 is a diagram showing the relationship between temperature changes and Raw values corresponding to different capacitances. In the example shown in Figure 5, the ambient temperature Ta of the touch panel device 100 decreases from 85°C to -40°C, similar to the example shown in Figure 3. Raw1, Raw2, and Raw3 each show the detected capacitance values for small, medium, and large capacitances, respectively. As shown in Figure 5, when the capacitance at the detection location is large, the Raw value also increases, and the amount of change in the Raw value that follows the temperature change also increases. As mentioned above, the variability of the Raw value before the temperature change itself can be dealt with by appropriately setting the baseline value through calibration.
[0032] In contrast, when a rapid temperature change occurs, the degree of change in the raw value differs depending on the magnitude of the capacitance, making it difficult to set a fixed update frequency X and an upper limit Y for the change in the baseline value (Figure 4).
[0033] For example, if the update frequency X and upper limit Y are set to match Raw3, which has the largest capacitance, it becomes possible to correct the baseline value to track Raw2 and Raw1, which have smaller capacitances. However, when an object touches the touch panel 110 and Raw3, which corresponds to the smallest capacitance, rises, the baseline value also rises at the same time, which may prevent the detection of contact with the object.
[0034] On the other hand, if the update frequency X and upper limit Y are set to match Raw1, which has the smallest capacitance, then during a sudden temperature change, Raw3, which has the largest capacitance, will rise in a state that deviates from the baseline value, even though the indicator is not in contact, resulting in false detection of the indicator.
[0035] In the touch panel device 100 of this embodiment, the update frequency X and upper limit Y are not fixed values, but are set variably according to the magnitude of the capacitance measured during calibration.
[0036] (Specific example of changing the update frequency X) Let a be the capacitance at each position of the touch panel 110 measured during calibration, and let A be their average value. When X0 is the update frequency of the baseline value at a position with the same capacitance as this average value A, the update frequency X of the baseline value at other positions with capacitance a is set to X0(A / a).
[0037] Figure 6 is an explanatory diagram for when the baseline value update frequency X is set to be variable. Figure 6(A) shows the baseline value correction operation corresponding to the baseline value update frequency X1 at a location with a capacitance a1 greater than the average value A. Figure 6(B) shows the baseline value correction operation corresponding to the baseline value update frequency X2 at a location with a capacitance a2 less than the average value A.
[0038] When the capacitance a1 is large, the amount of change in capacitance in response to a rapid temperature change is also large. Therefore, in order to keep up with this large change, the baseline value update frequency X1 (=X0(A / a1)) becomes smaller (shorter), as shown in Figure 6(A).
[0039] On the other hand, when the capacitance a2 is small, the amount of change in capacitance in response to a rapid temperature change is small, so the baseline value update frequency X2 (=X0(A / a2)) becomes larger (longer) in order to follow this small change, as shown in Figure 6(B).
[0040] (Specific examples of changing the upper limit Y) Let a be the capacitance measured at each position of the touch panel 110 during calibration, and let A be their average value. When Y0 is set as the upper limit for updating the baseline value at a position with the same capacitance as this average value A, the upper limit Y for updating the baseline value at other positions with capacitance a is set to Y0(a / A).
[0041] Figure 7 is an explanatory diagram for when the upper limit Y is variably set when updating the baseline value. Figure 7(A) shows the baseline value correction operation corresponding to the upper limit Y1 when updating the baseline value at a location with a capacitance a1 greater than the average value A. Figure 7(B) shows the baseline value correction operation corresponding to the upper limit Y2 when updating the baseline value at a location with a capacitance a2 less than the average value A.
[0042] When the capacitance a1 is large, the change in capacitance in response to a rapid temperature change is also large. Therefore, in order to keep up with this large change, the upper limit Y1 (=Y0(a1 / A)) when updating the baseline value becomes large, as shown in Figure 7(A).
[0043] On the other hand, when the capacitance a2 is small, the amount of change in capacitance in response to a rapid temperature change is small. Therefore, in order to follow this small change, the upper limit Y2 (=Y0(a2 / A)) when updating the baseline value becomes small, as shown in Figure 7(B).
[0044] Thus, in the touch panel device 100 of this embodiment, if there is variation in the capacitance of each electrode pair in the touch panel 110, the baseline value can be changed for each capacitance, making it possible to prevent false detections during rapid temperature changes caused by this variation. Furthermore, since it is not necessary to determine the presence or absence of an indicator when changing the baseline value, a configuration for this determination is unnecessary, and the configuration can be simplified.
[0045] Furthermore, when the reference capacitance (capacitance during calibration) of each electrode pair of the touch panel 110 is large, the time (update frequency) X is set to a small value or the upper limit Y of the baseline value during updates is set to a large value. Conversely, when the reference capacitance of each electrode pair is small, the time X is set to a large value or the upper limit Y is set to a small value. This makes it possible to individually set the update frequency X and upper limit Y according to the capacitance of each electrode pair, thereby creating a baseline value suitable for preventing false detections. In addition, by setting a baseline value suitable for preventing false detections for each electrode pair with variations in capacitance, it becomes possible to improve the position detection accuracy when an indicator object approaches.
[0046] Furthermore, by changing the update frequency X or upper limit Y when the amount of change in ambient temperature Ta over a certain period of time exceeds a predetermined value, false detections can be reliably prevented in environments with drastic temperature changes.
[0047] It should be noted that the present invention is not limited to the embodiments described above, and various modifications can be made within the scope of the gist of the invention. For example, in the embodiments described above, either the baseline value update frequency X or the upper limit value Y at the time of update was set to be variable, but these values may be set to be variable simultaneously.
[0048] Furthermore, in the embodiments described above, a transparent touch panel device mounted on top of the screen of a display device was assumed, and therefore the case in which transparent electrodes are formed on the touch panel 110 was considered. However, the present invention may also be applied to non-transparent touch panel devices such as tablets used on a desk. [Industrial applicability]
[0049] As described above, according to the present invention, when there is variation in the capacitance of each electrode pair in the touch panel, the baseline value can be changed for each capacitance, thereby preventing false detection during rapid temperature changes caused by this variation. Furthermore, since it is not necessary to determine whether or not an indicator is present when changing the baseline value, a configuration for this determination is unnecessary, and the configuration can be simplified. [Explanation of symbols]
[0050] 100 Touch panel devices 110 Touch Panel 110A First transparent electrode 110B Second transparent electrode 120 Capacitance measurement section 130, 132 Switch (SW) 140 Position detection unit 150 Baseline value setting section 152 Baseline value storage unit 160 Baseline value correction unit 162 Temperature sensor (T)
Claims
1. A capacitive touch panel having multiple electrodes arranged in directions that intersect each other, A capacitance measuring means for measuring the capacitance between a pair of intersecting electrodes for each electrode pair, When the indicator is not in contact, the capacitance of each electrode pair measured by the capacitance measuring means is used as the reference capacitance, and a baseline value setting means is set prior to detecting the contact position of the indicator as a baseline value used for comparing capacitances to detect whether or not the indicator is in contact. A position detection means detects the contact position of an indicator by comparing the capacitance of each electrode pair measured by the capacitance measuring means with the corresponding baseline value. When the capacitance of each electrode pair measured by the capacitance measuring means changes over time when the contact position of the indicator is not detected, a baseline value correction means adjusts the baseline value in accordance with this change. A touch panel device comprising the above, wherein the baseline value correction means sets a time X as the period for changing the baseline value and / or an upper limit Y of the variation for each time X as the period for changing the baseline value, for each electrode pair according to the reference capacitance of each electrode pair.
2. The touch panel device according to claim 1, characterized in that the baseline value correction means sets the time X to a small value and / or the upper limit Y to a large value when the reference capacitance of each electrode pair is large, and sets the time X to a large value and / or the upper limit Y to a small value when the reference capacitance of each electrode pair is small.
3. The touch panel device according to claim 1, characterized in that the baseline value correction means sets the time X and the upper limit Y such that when the capacitance of each electrode pair increases in response to the approach of an indicator to the touch panel, the increase in the baseline value corresponding to each electrode pair does not keep up with the increase in capacitance.
4. The system further includes a temperature detection means for detecting the ambient temperature of the touch panel, The touch panel device according to claim 1, characterized in that the baseline value correction means changes the time X and / or the upper limit Y when the amount of change in the temperature detected by the temperature detection means over a certain period of time exceeds a predetermined value.
5. The touch panel device according to claim 1, characterized in that the baseline value correction means changes the time X for each electrode pair, which is the period for changing the baseline value, to (A / a)・X, where A is the average value of the capacitance of each electrode pair and a is the individual capacitance of each electrode pair.
6. The touch panel device according to claim 1, characterized in that the baseline value correction means changes the upper limit Y for each time X that causes the baseline value to vary to (a / A)・Y, where A is the average value of the capacitance of each electrode pair and a is the individual capacitance of each electrode pair.