Electrostatic coordinate input device and electrostatic coordinate calculation method

Abstract

The present invention provides an electrostatic coordinate input device and an electrostatic coordinate calculation method. When two fingers of an operator simultaneously perform proximity operations on an operation surface, the detection accuracy of the proximity positions of the two fingers is improved. The electrostatic coordinate input device comprises: a finger detection unit that detects the proximity positions of the operator's fingers relative to the operation surface by an electrostatic capacitance method; and a correction unit that corrects the two proximity positions in a direction of increasing the distance between the two proximity positions when the finger detection unit detects two proximity positions corresponding to the two fingers.

Description

Technical Field

[0001] The invention relates to an electrostatic coordinate input device and an electrostatic coordinate calculation method. Background Art

[0002] In the past, in an electrostatic coordinate input device that detects the approach position of a finger by electrostatic capacitance, a technique was used in which the coordinates of the peak of a quadratic curve of the coordinates of a detection electrode through which the change in electrostatic capacitance reaches a maximum value and the coordinates of the detection electrode adjacent to the detection electrode are complementarily calculated as the coordinates of the approach position of the finger (for example, refer to the following patent document 1).

[0003] Prior Art Literature

[0004] Patent Literature

[0005] Patent document 1: US8917257B2

[0006] However, in the prior art, especially in products with low resolution (for example, products with a small number of detection electrodes, products that detect fingers leaving the detection electrodes, etc.), when the operator's two fingers simultaneously perform close operation on the operating surface, the changes in electrostatic capacitance caused by each of the two fingers affect each other, so that the coordinates of the two peaks of the quadratic curve change in directions close to each other, and there is a concern that the detection accuracy of the close positions of each of the two fingers will decrease. Summary of the invention

[0007] An electrostatic coordinate input device involved in one embodiment comprises: a finger detection unit that detects the proximity position of an operator's finger relative to an operation surface by electrostatic capacitance; and a correction unit that corrects the two proximity positions in a direction of increasing the distance between the two proximity positions when two proximity positions corresponding to two fingers are detected by the finger detection unit.

[0008] Effects of the Invention

[0009] According to one embodiment, when an operator simultaneously performs proximity operations on an operation surface using two fingers, it is possible to improve the detection accuracy of the proximity positions of the two fingers. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a block diagram showing the structure of an electrostatic coordinate input device according to one embodiment.

[0011] Figure 2 This is a block diagram showing a functional structure of a control device according to one embodiment.

[0012] Figure 3 This is a flowchart showing the procedure of processing by a control device according to one embodiment.

[0013] Figure 4 It is a diagram showing an example of calculation of two proximity positions by a control device (finger detection unit) according to one embodiment.

[0014] Figure 5 This is a diagram showing an example of an error in the amount of change in electrostatic capacitance that may occur in the electrostatic coordinate input device according to one embodiment.

[0015] Figure 6 It is a diagram showing the relationship between the calculated value before correction and the calculated value after correction in each correction method of the control device (correction unit) according to one embodiment.

[0016] Description of Reference Numerals

[0017] 10: Electrostatic coordinate input device

[0018] 10A: Operation surface

[0019] 11: Sensor substrate

[0020] 12: X-axis electrode

[0021] 13: Y-axis electrode

[0022] 14: X-axis side detection unit

[0023] 15: Y-axis side detection unit

[0024] 16: A / D conversion unit

[0025] 17: Storage

[0026] 19: Interface

[0027] 20: Control device

[0028] 21: Electrostatic capacitance calculation department

[0029] 22: Finger detection unit

[0030] 23: Correction Department

[0031] 24: Output

[0032] 30A, 30B: Fingers DETAILED DESCRIPTION

[0033] Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

[0034] Figure 1 1 is a block diagram showing the structure of an electrostatic coordinate input device 10 according to an embodiment. Figure 1The electrostatic coordinate input device 10 shown is a device that allows an operator's finger to approach an operation surface 10A, and is a device that can detect the proximity position of the operator's finger relative to the operation surface 10A by an electrostatic capacitance method (self-capacitance detection method or mutual capacitance detection method).

[0035] like Figure 1 As shown, the electrostatic coordinate input device 10 includes a sensor substrate 11 , an X-axis side detection unit 14 , a Y-axis side detection unit 15 , an A / D converter 16 , a storage unit 17 , a control device 20 , and an interface unit 19 .

[0036] The sensor substrate 11 is provided on the operation surface 10A (see Figure 4 ) is arranged side by side in a matrix on the sensor substrate 11 for detecting the X-axis direction ( Figure 1 The plurality of X-axis electrodes 12 for detecting the electrostatic capacitance in the lateral direction) and the Y-axis direction ( Figure 1 Multiple Y-axis electrodes 13 of electrostatic capacitance (in the longitudinal direction).

[0037] The X-axis side detection unit 14 detects the electrostatic capacitance of each of the plurality of X-axis electrodes 12. In addition, the X-axis side detection unit 14 outputs a detection signal (analog signal) indicating the detected electrostatic capacitance of each of the plurality of X-axis electrodes 12.

[0038] The Y-axis side detection unit 15 detects the electrostatic capacitance of each of the plurality of Y-axis electrodes 13. In addition, the Y-axis side detection unit 15 outputs a detection signal (analog signal) indicating the electrostatic capacitance of each of the plurality of Y-axis electrodes 13 that has been detected.

[0039] The A / D (analog / digital) converter 16 converts the detection signal output from the X-axis side detector 14 and the detection signal output from the Y-axis side detector 15 into digital signals, and supplies them to the control device 20 .

[0040] The storage unit 17 stores various information. Examples of the information stored in the storage unit 17 include the electrostatic capacitance value of each of the plurality of X-axis electrodes 12 detected by the X-axis side detection unit 14, the electrostatic capacitance value of each of the plurality of Y-axis electrodes 13 detected by the Y-axis side detection unit 15, and a program executed by the control device 20.

[0041] The control device 20 detects the proximity position of the finger relative to the operation surface 10A in the X-axis direction based on the change in the electrostatic capacitance of each of the multiple X-axis electrodes 12 determined by the detection signal supplied from the X-axis side detection unit 14 via the A / D conversion unit 16. In addition, the control device 20 detects the proximity position of the finger relative to the operation surface 10A in the Y-axis direction based on the change in the electrostatic capacitance of each of the multiple Y-axis electrodes 13 determined by the detection signal supplied from the Y-axis side detection unit 15 via the A / D conversion unit 16. Then, the control device 20 outputs coordinate information indicating the determined proximity position of the finger. In addition, for details of the functions of the control device 20, use Figure 2 This will be described later.

[0042] The interface unit 19 outputs the coordinate information indicating the proximity position of the finger output from the control device 20 to an external device (not shown). For example, the external device executes a predetermined process corresponding to the coordinates based on the coordinate information indicating the proximity position of the finger output from the interface unit 19 .

[0043] (Functional Structure of Control Device 20)

[0044] Figure 2 2 is a block diagram showing the functional structure of the control device 20 according to one embodiment. Figure 2 As shown, the control device 20 includes an electrostatic capacitance calculation unit 21 , a finger detection unit 22 , a correction unit 23 , and an output unit 24 .

[0045] The electrostatic capacitance calculation unit 21 calculates the amount of change in the electrostatic capacitance of each detection electrode based on the detection signals supplied from the X-axis side detection unit 14 and the Y-axis side detection unit 15 via the A / D conversion unit 16 .

[0046] The finger detection unit 22 detects the approach position of the operator's finger in each of the X-axis direction and the Y-axis direction based on the amount of change in the electrostatic capacitance of each detection electrode detected by the electrostatic capacitance calculation unit 21 .

[0047] In this embodiment, the finger detection unit 22 can detect the proximity position of the operator's finger using a curve approximation calculation method for the X-axis direction and the Y-axis direction. Specifically, the finger detection unit 22 can use the following formula (1) to calculate the vertex of a quadratic curve passing through the peak electrode, the electrode before the peak electrode, and the electrode after the peak electrode, as the proximity position of the operator's finger, by taking the electrode with the largest change in electrostatic capacitance as the peak electrode for the X-axis direction and the Y-axis direction.

[0048] [Formula 1]

[0049]

[0050] In the above formula (1), XQ represents the coordinates of the approach position of the operator's finger. pk represents the change in electrostatic capacitance in the peak electrode. pk-1 represents the change in electrostatic capacitance of the detection electrode before the peak electrode. pk+1 represents the change in electrostatic capacitance of the detection electrode behind the peak electrode. In addition, RESO represents the inter-electrode resolution. In addition, X OFS represents the coordinates of the peak electrode.

[0051] In the present embodiment, when the operator performs a proximity operation with two fingers on operation surface 10A, control device 20 can cause finger detection unit 22 to identify the proximity positions of the operator's two fingers in each of the X-axis direction and the Y-axis direction.

[0052] When the distance between two close positions detected by the finger detection unit 22 is shorter than a given threshold, the correction unit 23 corrects the two close positions in a direction of increasing the distance between the two close positions. In particular, in the present embodiment, when the distance between two close positions detected by the finger detection unit 22 is less than a given threshold, the correction unit 23 corrects the distance between the two close positions to a given distance greater than the distance between the two close positions. For example, when the distance between two close positions detected by the finger detection unit 22 is less than "21 mm" (an example of a "given threshold"), the correction unit 23 corrects the distance between the two close positions to "21 mm" (an example of a "given distance").

[0053] The output unit 24 outputs the coordinate information indicating the proximity position of the operator's finger detected by the finger detection unit 22. Alternatively, the output unit 24 outputs the coordinate information indicating the proximity position of the operator's finger corrected by the correction unit 23.

[0054] In addition, the control device 20 is configured to include a processor (e.g., CPU), a storage medium (e.g., ROM (Read Only Memory), RAM (Random Access Memory), SSD (Solid State Drive), etc.), a communication interface, etc. as a hardware structure. For example, Figure 2 Each functional unit of the control device 20 shown is implemented by executing a program stored in a storage medium by a processor. In addition, at least one of the A / D converter 16 , the storage unit 17 , and the interface unit 19 may be provided in the control device 20 .

[0055] (Steps processed by the control device 20)

[0056] Figure 3 1 is a flowchart showing the procedure of processing of the control device 20 according to one embodiment.

[0057] First, the capacitance calculation unit 21 of the control device 20 calculates the amount of change in capacitance of each detection electrode based on the detection signals supplied from the X-axis detection unit 14 and the Y-axis detection unit 15 via the A / D conversion unit 16 (step S301 ).

[0058] Next, the finger detection unit 22 of the control device 20 determines the finger approach area in the operation surface 10A based on the change in electrostatic capacitance of each detection electrode calculated in step S301 (step S302). For example, the finger detection unit 22 detects an area including a plurality of detection electrodes whose change in electrostatic capacitance is greater than a given threshold as the finger approach area.

[0059] Next, the finger detection unit 22 of the control device 20 compares the changes in electrostatic capacitance of the plurality of detection electrodes included in the finger proximity area determined in step S302 to determine the detection electrode having the maximum value of the change in electrostatic capacitance among the plurality of detection electrodes (step S303).

[0060] Next, the finger detection unit 22 of the control device 20 determines whether two proximity positions are detected (i.e., whether two fingers are detected) based on the detection electrode whose capacitance change amount is determined to be a maximum value in step S303 (step S304). For example, in step S303, when two detection electrodes are determined, the finger detection unit 22 determines that two proximity positions are detected.

[0061] In step S304, when it is determined that two close positions are not detected (step S304: No), that is, when it is determined that one close position is detected, the finger detection unit 22 calculates the coordinates of one close position using the curve approximation calculation method (step S305). Then, the output unit 24 outputs the coordinate information including the one coordinate calculated in step S305 (step S310). Then, the control device 20 ends. Figure 3 A series of processing is shown.

[0062] On the other hand, in step S304 , when it is determined that two proximity positions are detected (step S304 : Yes), the finger detection unit 22 calculates the coordinates of each of the two proximity positions using the curve approximation calculation method (step S306 ).

[0063] Next, the correction unit 23 calculates the distance between the two coordinates calculated in step S306 (step S307 ). Then, the correction unit 23 determines whether the distance calculated in step S307 is smaller than a given threshold value (for example, “21 mm”) (step S308 ).

[0064] In step S308, if it is determined that the distance between the two coordinates is not less than the given threshold value (step S308: No), the output unit 24 outputs the coordinate information including the two coordinates calculated in step S306 (step S310). Then, the control device 20 ends Figure 3 A series of processing is shown.

[0065] On the other hand, in step S308, when it is determined that the distance between the two coordinates is less than the given threshold value (step S308: Yes), the correction unit 23 corrects the two coordinates so that the distance between the two coordinates becomes a given distance (for example, "21 mm") in the direction of expansion (step S309). For example, the correction unit 23 obtains a line segment connecting the two coordinates and the center point of the line segment, and corrects the two coordinates so that the distances from the center point to the two coordinates are equal.

[0066] Then, the output unit 24 outputs the coordinate information including the two coordinates obtained by the correction in step S309 (step S310). Then, the control device 20 ends Figure 3 A series of processing is shown.

[0067] In this embodiment, when two fingers are brought close to each other to a distance of 21 mm or less and rotated, the output is performed as if the fingers were rotated at the same interval (21 mm).

[0068] (Calculation example of two close positions)

[0069] Figure 4 1 is a diagram showing an example of calculation of two proximity positions by the control device 20 (finger detection unit 22) according to one embodiment.

[0070] exist Figure 4 In the example shown, 15 X-axis electrodes 12 (X0 to X14) and 15 Y-axis electrodes 13 (Y0 to Y14) are provided in a matrix on the sensor substrate 11 so as to overlap with the operation surface 10A. Figure 4 In the illustrated example, the operator performs a proximity operation on the operation surface 10A using two fingers 30A and 30B.

[0071] like Figure 4 As shown, in the X-axis direction, peak values ​​of the amount of change in electrostatic capacitance are generated at the X-axis electrode X4 overlapping the finger 30A and the X-axis electrode X10 overlapping the finger 30B.

[0072] For example, the finger detection unit 22 of the control device 20 can use the curve approximation method to calculate the X-axis coordinates of the vertex positions of the quadratic curve passing through the X-axis electrode X4 and the X-axis electrodes X3 and X5 before and after it as the X-axis coordinates of the approaching position of the finger 30A.

[0073] Similarly, the finger detection unit 22 of the control device 20 can use the curve approximation method to calculate the X-axis coordinates of the vertex positions of the quadratic curve passing through the X-axis electrode X10 and the X-axis electrodes X9 and X11 before and after it as the X-axis coordinates of the approaching position of the finger 30B.

[0074] In addition, if Figure 4 As shown, in the Y-axis direction, peak values ​​of the amount of change in electrostatic capacitance are generated at the Y-axis electrode Y10 overlapping the finger 30A and the Y-axis electrode Y4 overlapping the finger 30B.

[0075] For example, the finger detection unit 22 of the control device 20 can use the curve approximation method to calculate the Y-axis coordinate of the vertex position of the quadratic curve passing through the Y-axis electrode Y10 and the Y-axis electrodes Y9 and Y11 before and after it as the Y-axis coordinate of the approach position of the finger 30A.

[0076] Similarly, the finger detection unit 22 of the control device 20 can use the curve approximation method to calculate the Y-axis coordinate of the vertex position of the quadratic curve passing through the Y-axis electrode Y4 and the Y-axis electrodes Y3 and Y5 before and after it as the Y-axis coordinate of the approaching position of the finger 30B.

[0077] (An example of error in capacitance change)

[0078] Figure 5 1 is a diagram showing an example of an error in the amount of change in electrostatic capacitance that may occur in the electrostatic coordinate input device 10 according to one embodiment.

[0079] exist Figure 5 In FIG. 1 , the dotted line indicates the amount of change in the electrostatic capacitance of each detection electrode when each of the two fingers is detected individually when the distance between the two fingers is set to "20 mm". Figure 5 In FIG. 1 , the solid line indicates the change in the electrostatic capacitance of each detection electrode when two fingers are detected simultaneously when the distance between the two fingers is set to “20 mm”. Figure 5 In the graph shown in FIG. 1 , the horizontal axis represents the number and position of the detection electrode, and the vertical axis represents the change in the electrostatic capacitance value. Figure 5 In the graph shown, it is assumed that the interval between electrodes is "5 mm".

[0080] As in Figure 5As shown by the dotted line in FIG. 1 , when two fingers are detected separately, the change in electrostatic capacitance based on one finger does not cause the change in electrostatic capacitance based on the other finger, so the distance between the two peak electrodes is approximately equal to the actual distance between the two fingers ("20 mm"). Figure 5 As shown by the solid line in FIG. 2 , when two fingers are detected at the same time, the change in electrostatic capacitance based on the two fingers is synthesized, so there is a concern that the distance between the two peak electrodes is shorter than the actual distance between the two fingers ("20 mm"). In this case, there is a concern that the distance between the two proximity positions calculated by the finger detection unit 22 is shorter than the actual distance between the two fingers.

[0081] Therefore, when the distance between the two proximity positions calculated by the finger detection unit 22 is less than a given threshold value (e.g., "21 mm"), the control device 20 according to one embodiment corrects the distance between the two proximity positions to a given distance (e.g., "21 mm"). Thus, the control device 20 according to one embodiment can correct the coordinates of each of the two proximity positions so that the distance between the two proximity positions is substantially equal to the actual distance between the two fingers. As a result, when the operator's two fingers perform a proximity operation on the operation surface 10A, the control device 20 according to one embodiment can improve the detection accuracy of the proximity positions of each of the two fingers.

[0082] In the present embodiment, the given distance is set to "21 mm" because, usually, when two adjacent fingers (for example, the index finger and the middle finger) are placed in close proximity, it is difficult to imagine that the distance between the centers of the two fingers will be smaller than "21 mm".

[0083] (Comparative example of correction method)

[0084] Figure 6 1 is a diagram showing the relationship between the calculated value before correction and the calculated value after correction in each correction method of the control device 20 (correction unit 23) according to one embodiment.

[0085] exist Figure 6 In FIG. 1 , the relationship between the calculated value before correction and the calculated value after correction by the first correction method of the correction unit 23 is represented by a solid line. Figure 6 In the graph shown, the horizontal axis represents the calculated value of the distance between the two close positions before correction, and the vertical axis represents the calculated value of the distance between the two close positions after correction.

[0086] exist Figure 6In FIG. 1 , the solid line indicates the relationship between the calculated value before correction and the calculated value after correction by the first correction method of the correction unit 23. The first correction method is a correction method for correcting the distance between two close positions to a given distance greater than the distance between the two close positions when the distance between the two close positions is less than a given threshold. For example, Figure 6 In the figure, as the first correction method, the following example is shown, that is, when the distance between two close positions is less than "21 mm" (an example of a "given threshold value"), the distance between the two close positions is corrected to "21 mm" (an example of a "given distance").

[0087] In addition, Figure 6 In FIG. 1 , the relationship between the calculated value before correction and the calculated value after correction by the second correction method of the correction unit 23 is indicated by a dotted line. The second correction method is a method of correcting the distance between the two close positions so that the longer the distance between the two close positions, the smaller the difference between the distance between the two close positions and the given distance larger than the distance between the two close positions. For example, Figure 6 In the example shown as the second correction method, that is, when the distance between two close positions is less than "21mm" (an example of a "given threshold value"), the distance between the two close positions is corrected so that the longer the distance between the two close positions is, the smaller the difference from "21mm" (an example of a "given distance") becomes. For example, in the second correction method, x can be used as the calculated value before correction, and the corrected calculated value of the distance between the two close positions can be obtained by the formula {x / constant 1+constant 2}. However, this formula is an example, and other formulas can also be used to obtain the corrected calculated value. Constants 1 and 2 can be pre-set to appropriate values ​​through simulation, etc.

[0088] In addition, Figure 6 In the figure, a single-dotted line is used to represent the relationship between the calculated value before correction and the calculated value after correction of the third correction method of the control device 20. The third correction method is a correction method that corrects in the direction of increasing the distance between the two close positions so that the shorter the distance between the two close positions, the larger the correction amount becomes. For example, in the third correction method, X can be used as the calculated value before correction, and the corrected calculated value of the distance between the two close positions can be obtained by the formula {X+constant 3 / (X×constant 4+constant 5)^2}. However, this formula is an example, and other formulas can also be used to obtain the corrected calculated value. Constants 3 to 5 can be pre-set to appropriate values ​​through simulation, etc.

[0089] As a method for correcting the distance between two close positions, the correction unit 23 can use any of the first method, the second method, and the third method. Regardless of which correction method the correction unit 23 uses, it is possible to appropriately correct the distance between the two close positions so that the distance between the two close positions does not become an abnormal value, thereby improving the detection accuracy of each of the two close positions. In particular, when operating with two fingers, the center coordinates of the two positions, the direction (angle) of the line segment connecting the two positions, and the interval between the two positions are important. The present invention can improve the accuracy of the interval between two positions without deteriorating the accuracy of the center coordinates of the two positions and the accuracy of the direction (angle) of the line segment connecting the two positions.

[0090] As mentioned above, although one embodiment of the present invention has been described in detail, the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims.

[0091] For example, in one embodiment, the finger detection unit 22 calculates the coordinates of the two close positions by a curve approximation calculation method based on the position of the detection electrode where the change amount of the electrostatic capacitance value is a maximum value, but the invention is not limited thereto. For example, the finger detection unit 22 may also calculate the coordinates of the two close positions by a centroid calculation method based on the position of the detection electrode where the change amount of the electrostatic capacitance value is a maximum value.

Claims

1. An electrostatic coordinate input device, characterized in that: have: a finger detection unit that detects the proximity position of the operator's finger relative to the operation surface by means of electrostatic capacitance; and a correction unit that corrects the two proximity positions in a direction of increasing the distance between the two proximity positions when the two proximity positions corresponding to the two fingers are detected by the finger detection unit, The correction unit corrects the two close positions in a direction of increasing the distance between the two close positions when the distance between the two close positions is smaller than a given threshold value. When the distance between the two close positions is smaller than a given threshold, the correction unit corrects the distance between the two close positions so that the longer the distance between the two close positions is, the smaller the difference between the distance and a given distance greater than the distance between the two close positions becomes.

2. An electrostatic coordinate input device, characterized in that: have: a finger detection unit that detects the proximity position of the operator's finger relative to the operation surface by means of electrostatic capacitance; and a correction unit that corrects the two proximity positions in a direction of increasing the distance between the two proximity positions when the two proximity positions corresponding to the two fingers are detected by the finger detection unit, The correction unit corrects the two close positions in a direction of increasing the distance between the two close positions so that the correction amount becomes larger as the distance between the two close positions becomes shorter.

3. The electrostatic coordinate input device according to claim 1 or 2, characterized in that: The finger detection unit calculates the coordinates of each of the two proximity positions by a curve approximation method based on the position of the detection electrode where the amount of change in the electrostatic capacitance value reaches a maximum value.

4. The electrostatic coordinate input device according to claim 1 or 2, characterized in that: The finger detection unit calculates the coordinates of each of the two proximity positions by a center of gravity calculation method based on the position of the detection electrode where the amount of change in the electrostatic capacitance value reaches a maximum value.

5. A method for calculating electrostatic coordinates, characterized in that: Include: Finger detection process, detecting the proximity position of the operator's finger relative to the operating surface by electrostatic capacitance; as well as a correction step of correcting the two proximity positions in a direction of increasing the distance between the two proximity positions when the two proximity positions corresponding to the two fingers are detected by the finger detection step, In the correction step, when the distance between the two close positions is smaller than a given threshold, the two close positions are corrected in a direction of increasing the distance between the two close positions. In the correction process, when the distance between the two close positions is smaller than a given threshold, the distance between the two close positions is corrected so that the longer the distance between the two close positions, the smaller the difference between the distance and a given distance greater than the distance between the two close positions becomes.

6. A method for calculating electrostatic coordinates, characterized in that: Include: Finger detection process, detecting the proximity position of the operator's finger relative to the operating surface by electrostatic capacitance; as well as a correction step of correcting the two proximity positions in a direction of increasing the distance between the two proximity positions when the two proximity positions corresponding to the two fingers are detected by the finger detection step, In the correction step, the two close positions are corrected in a direction of increasing the distance between the two close positions so that the correction amount becomes larger as the distance between the two close positions becomes shorter.

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