Electrostatic input device and input determination method

Abstract

An electrostatic input device and input determination method are provided, capable of distinguishing between a state where one finger is in contact with the electrostatic coordinate input section at an angle relative to it and a state where multiple fingers are in contact with the electrostatic coordinate input section. The electrostatic input device includes: a measurement unit that measures the electrostatic capacitance in multiple coordinates of the electrostatic coordinate input section; a transformation unit that obtains a reference value for the electrostatic capacitance and subtracts the reference value from the electrostatic capacitance to transform it into a difference value corresponding to the distance between the electrostatic coordinate input section and the finger in the multiple coordinates; a first coordinate calculation unit that calculates the centroid coordinates of the contact area based on the difference value with respect to the multiple coordinates; a period determination unit that determines whether the difference value in the coordinates on the circumference of a circle of a given radius centered on the centroid coordinates represents a periodicity of two periods along one circumference of the circle; and an operation determination unit that, if determined by the period determination unit to represent a periodicity of two periods, determines that an input operation performed by two or more fingers has been performed.

Description

Technical Field

[0001] This invention relates to an electrostatic input device and an input determination method. Background Technology

[0002] In capacitive touchpads and touch panels, the change in electrostatic capacitance when a finger or stylus touches the surface is used to detect the finger or stylus. Capacitive touchpads and touch panels can detect fingers and styluses even when there is an insulating plate on the sensor electrodes. However, if the plate on the sensor electrodes is thick, the resolution decreases, and sometimes the area where two fingers or styluses contact the plate is considered as a large distribution area for detection. Previously, a type of touch panel was known that calculates the flatness of the detected distribution area and determines whether it is a single-point or multi-point touch based on the flatness (for example, see Patent Document 1).

[0003] Prior art literature

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2014-186530 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] However, the detected touch area becomes elliptical in both the case of a single finger touching the touch panel / touchpad at an angle relative to it and the case of multiple fingers touching the touch panel / touchpad. Conventional input devices, which determine whether a touch is single-point or multi-point based on the flatness of the touch area, cannot distinguish between the case of a single finger touching the touch panel / touchpad at an angle relative to it and the case of multiple fingers touching the touch panel / touchpad.

[0008] Therefore, the object of the present invention is to provide an electrostatic input device and an input determination method capable of distinguishing between a state in which one finger is in contact with the electrostatic coordinate input section and a state in which multiple fingers are in contact with the electrostatic coordinate input section.

[0009] Methods for solving problems

[0010] An electrostatic input device according to an embodiment of the present invention includes: a measuring unit that measures the electrostatic capacitance in a plurality of coordinates of an electrostatic coordinate input unit; a transformation unit that obtains a reference value of the electrostatic capacitance and subtracts the reference value from the electrostatic capacitance to transform it into a difference value corresponding to the distance between the electrostatic coordinate input unit and a finger in the plurality of coordinates; a first coordinate calculation unit that calculates the centroid coordinates of a contact portion based on the difference value with respect to the plurality of coordinates; a period determination unit that determines whether the difference value in the coordinates on the circumference of a circle of a given radius centered on the centroid coordinates represents a periodicity of two periods along one circumference of the circle; and an operation determination unit that, if determined by the period determination unit to represent a periodicity of two periods, determines that an input operation performed by two or more fingers has been performed.

[0011] Invention Effects

[0012] An electrostatic input device and input determination method are provided that can distinguish between a state in which one finger is in contact with the electrostatic coordinate input section and a state in which multiple fingers are in contact with the electrostatic coordinate input section. Attached Figure Description

[0013] Figure 1 This is a diagram showing the electrostatic input device 100 of Embodiment 1.

[0014] Figure 2 This is a graph showing the relationship between the state of an upright finger F and the measured value of the electrostatic coordinate input unit 110 when the electrostatic coordinate input unit 110 is operated.

[0015] Figure 3 This is a graph showing the relationship between the state of a tilted finger F when operating the electrostatic coordinate input unit 110 and the measured value of the electrostatic coordinate input unit 110.

[0016] Figure 4 This is a graph showing the relationship between the state of the two fingers F and F' when operating the electrostatic coordinate input unit 110 and the measured value of the electrostatic coordinate input unit 110.

[0017] Figure 5 It is a diagram illustrating the planar distribution of the difference values ​​caused by the difference in the positional relationship between the two fingers F and F', as well as the difference in the angular characteristics of the difference values.

[0018] Figure 6 It is a diagram illustrating the planar distribution of the difference values ​​caused by the difference in the positional relationship between the two fingers F and F', as well as the difference in the angular characteristics of the difference values.

[0019] Figure 7 This is a diagram illustrating the coordinates PF1 and PF2 of two fingers F and F'.

[0020] Figure 8 This is a flowchart illustrating the input determination method of Implementation Method 1.

[0021] Figure 9 This is a diagram representing the calibration table.

[0022] Figure 10 This is a diagram showing the electrostatic input device 200 of Embodiment 2.

[0023] Figure 11 This is a graph showing the relationship between the eccentricity e and the measured value of the constant.

[0024] Figure 12 This is a diagram illustrating an example of the center coordinates of two fingers obtained by the approximation processing unit 254 through approximation processing and the coordinate calculation unit 255.

[0025] Figure 13 This is a diagram illustrating an example of the center coordinates of two fingers obtained by the approximation processing unit 254 through approximation processing and the coordinate calculation unit 255.

[0026] Figure 14 This is a diagram illustrating an example of the center coordinates of two fingers obtained by the approximation processing unit 254 through approximation processing and the coordinate calculation unit 255.

[0027] Figure 15 It is a graph showing the relationship between the distance Lm between the center coordinates of the two fingers as measured, and the distances Lc1 and Lc2 between the two points calculated by the coordinate calculation unit 255 as the center coordinates of the two fingers.

[0028] Figure 16 It is a graph showing the relationship between the distance Lm between the center coordinates of the two fingers as measured, and the distances Lc1 and Lc2 between the two points calculated by the coordinate calculation unit 255 as the center coordinates of the two fingers.

[0029] Figure 17 This is a flowchart illustrating the input determination method of Implementation Method 2.

[0030] Figure 18 This is a flowchart illustrating the input determination method of Implementation Method 3.

[0031] Figure 19 This is a flowchart illustrating the input determination method of Implementation Method 4.

[0032] Figure 20 This is a flowchart illustrating the input determination method of Implementation Method 5.

[0033] Figure 21It is a diagram illustrating the planar distribution of the difference values ​​caused by the difference in the positional relationship between the two fingers F and F', as well as the difference in the angular characteristics of the difference values. Detailed Implementation

[0034] The following describes embodiments of the electrostatic input device and input determination method using the present invention.

[0035] <Implementation Method 1>

[0036] Figure 1 This is a diagram showing the electrostatic input device 100 according to Embodiment 1. Hereinafter, the XYZ coordinate system will be defined for explanation. Furthermore, from this perspective, "top view" refers to the XY plane view. The -Z direction is the direction approaching the electrostatic input device. For ease of explanation, the -Z direction side will be referred to as the lower side or lower. The +Z direction is the direction away from the electrostatic input device. For ease of explanation, the +Z direction side will be referred to as the upper side or upper.

[0037] The electrostatic input device 100 includes an electrostatic coordinate input unit 110, a multipexor 120, a drive circuit 130, a detection unit 140, and a control unit 150.

[0038] The electrostatic coordinate input unit 110 has multiple electrodes 111 for detecting position in the X direction and multiple electrodes 112 for detecting position in the Y direction. The multiple electrodes 111 and 112 are formed of a light-transmitting conductive material such as ITO (Indium Tin Oxide) on the upper and lower surfaces of a transparent substrate (not shown). The multiple electrodes 111 are composed of electrodes X0, X1, X2, X3, ..., Xn. Electrodes X0, X1, X2, X3, ..., Xn are arranged at a certain interval along the X direction and extend in the Y direction. The multiple electrodes 112 are composed of electrodes Y0, Y1, Y2, Y3, ..., Yn. Electrodes Y0, Y1, Y2, Y3, ..., Yn are arranged at a certain interval along the Y direction and extend in the X direction. The portion where the multiple electrodes 111 and 112 intersect when viewed from above is indicated as intersection point 113.

[0039] The multiplexer 120 is a switching circuit that connects multiple electrodes 111 (X0, X1, X2, X3, ..., Xn) and multiple electrodes 112 (Y0, Y1, Y2, Y3, ..., Yn) to the drive circuit 130 or the detection unit 140.

[0040] The drive circuit 130 groups multiple electrodes 111 (X0, X1, X2, X3, ..., Xn) and multiple electrodes 112 (Y0, Y1, Y2, Y3, ..., Yn) and outputs drive power sequentially.

[0041] When the detection unit 140 supplies driving power to the plurality of electrodes 111 (X0, X1, X2, X3, ..., Xn) through the driving circuit 130, it measures the current flowing in each electrode (Y0, Y1, Y2, Y3, ..., Yn) of the plurality of electrodes 112 and calculates the electrostatic capacitance at each intersection point 113. The electrostatic capacitance measured by the detection unit 140 at each intersection point 113 is the electrostatic capacitance generated between the electrodes 111 and 112 at each intersection point 113. The electrostatic capacitance generated at each intersection point 113 is affected by a conductor (finger) near each intersection point 113. The electrostatic capacitance values ​​at each intersection 113 are input to the conversion unit 151 of the control unit 150.

[0042] The control unit 150 includes a transformation unit 151, a center of gravity coordinate calculation unit 152, a period determination unit 153, an operation determination unit 154, and a coordinate calculation unit 155.

[0043] When the electrostatic capacitance measured by the detection unit 140 is less than a threshold, the transformation unit 151 calculates the average value of the electrostatic capacitance at each intersection point 113 obtained by the detection unit 140 through multiple measurements in a time sequence. Then, the transformation unit 151 uses the calculated average value as a reference value when the electrostatic coordinate input unit 110 measures the electrostatic capacitance. Furthermore, the transformation unit 151 subtracts the reference value from the measured electrostatic capacitance values ​​measured by the detection unit 140 for each intersection point 113, transforming the value into a difference value (hereinafter referred to as the difference value) corresponding to the electrostatic capacitance between the electrostatic coordinate input unit 110 and the finger at each intersection point 113. The reference value is obtained for each intersection point 113.

[0044] The centroid coordinate calculation unit 152 is an example of the first coordinate calculation unit. The centroid coordinate calculation unit 152 calculates the centroid based on the difference values ​​of each intersection point 113 output by the transformation unit 151. In this invention, the "centroid" is the centroid when the difference values ​​of each intersection point 113 are considered as the mass of that intersection point 113. In other words, the "centroid" of this invention is the center of the distribution of electrostatic capacitance.

[0045] The period determination unit 153 determines whether the difference value at the intersection point 113 of each electrode 111, 112 on the circumference of a circle of a given radius centered on the centroid coordinates calculated by the centroid coordinate calculation unit 152 represents a periodicity of two periods along one circumference of the circle. The term "periodicity of two periods along one circumference" is defined as follows: Figure 4 As shown in (C), the sine wave component with a π [rad] interval is large. Regarding the processing of the period determination unit 153, the following is used... Figures 2 to 4To be discussed later.

[0046] When the operation determination unit 154 determines by the period determination unit 153 that the difference value at each intersection point 113 on the circumference of a circle with a given radius centered on the centroid coordinate calculated by the centroid coordinate calculation unit 152 represents a periodicity of 2 periods, it determines that an input operation performed by multiple fingers has been performed.

[0047] When the operation determination unit 154 determines that an input operation has been performed by multiple fingers, the coordinate calculation unit 155 calculates the center coordinates of each of the multiple fingers. Furthermore, when the operation determination unit 154 determines that an input operation has been performed by a single finger, the coordinate calculation unit 155 outputs the center coordinates of the finger as calculated by the center coordinate calculation unit 152.

[0048] Figures 2 to 4 This is a graph showing the relationship between the state of the finger F when operating the electrostatic coordinate input unit 110 and the measured value of the electrostatic coordinate input unit 110. Figure 2 (A) shows the state of inputting by raising one finger F. Figure 3 (A) shows the state of inputting by tilting one finger F. Figure 4 (A) shows the state of inputting by raising two fingers F and F'.

[0049] also, Figure 2 (B) Figure 3 (B) Figure 4 (B) represents the planar distribution of the difference values ​​at intersection point 113. The planar distribution of the difference values ​​is represented by contour lines (closed curves with solid lines) corresponding to the difference values, and the area FA (hereinafter referred to as the finger area FA) representing the position of the finger F detected by the detection unit 140 and the measurement circle (a circle with a radius r centered on the centroid of the finger area FA) are represented together. The finger area FA is represented by a monotonically varying gradient, with the black part being the part where the finger F contacts the electrostatic coordinate input unit 110. The gray part is the part where the finger F approaches the electrostatic coordinate input unit 110. Furthermore, the measurement circle is a circle centered on the centroid. The diameter of the measurement circle is the average distance between the centers of the two fingers when they are in contact. As an example, the diameter of the measurement circle is 18 mm (radius is 9 mm). Figure 2 (B) Figure 3 (B) Figure 4 In (B), the origin of the XY coordinates is the centroid of the finger region FA. The radius of the measuring circle is not limited to 9 mm. Sufficiently high accuracy can be obtained if the radius of the measuring circle is 8 mm to 10 mm. Furthermore, the measuring circle does not necessarily need to have a fixed radius. For example, the distance from the centroid to the position where the difference value is the largest can also be used.

[0050] also, Figure 2 (C) Figure 3 (C) Figure 4 (C) represents the angular characteristics of the difference value. The horizontal axis represents the angle, and the vertical axis represents the difference value on the measurement circle. The angle represents the position on the measurement circle. Points in the positive interval of the X-axis are set to 0 [rad], and the angle is set counterclockwise. Therefore, the angle of a point in the positive interval of the Y-axis on the measurement circle is π / 2 [rad], the angle of a point in the negative interval of the X-axis is π [rad], and the angle of a point in the negative interval of the Y-axis is 3π / 4 [rad]. Figure 2 (C) Figure 3 (C) Figure 4 The difference value shown in (C) is the difference value from the point 0 [rad] in the measurement circle to each sampling point of π / 18 [rad]. In the case that there is no intersection 113 of the sampling points, the value is obtained by linear approximation based on the difference values ​​at multiple intersection 113 around the sampling points.

[0051] like Figure 2 As shown in (A), in the state of inputting while holding up one finger F, such as Figure 2 As shown in (B), the output of the transformation unit 151 becomes such that the finger region FA above a given threshold is circular, and the contour lines are concentric circles. In this case, as... Figure 2 As shown in (C), the angular characteristics of the difference values ​​become flat. This is because the difference values ​​at each sampling point on the measurement circle are equal.

[0052] In addition, such as Figure 3 As shown in (A), in the state of inputting while tilting one finger F, such as Figure 3 As shown in (B), the output of the transformation unit 151 is such that the finger region FA above a given threshold is elliptical, and the contour lines are also elliptical. The spacing between the contour lines is narrowest on the tip side of finger F and widest on the root side (the side closer to the back of the hand). In this case, the angular characteristic of the difference value is maximized at point PMAX = 1 within one circumference of the measurement circle, therefore... Figure 3 As shown in (C), the periodicity represents one cycle along one circumference of the measuring circle.

[0053] In addition, such as Figure 4 As shown in (A), when performing input with two fingers F and F' raised, such as... Figure 4As shown in (B), the output of the transform unit 151 is that the finger region FA above a given threshold is divided into two circles, and the contour lines are elliptical. The spacing between the contour lines is wider on the X-direction connecting the two fingers F and F' and narrower on the Y-direction, which is π / 2 [rad] different from each other. In this case, the angular characteristic of the difference value is that the difference value is maximized at point PMAX = 2 in one circumference of the measurement circle, therefore, as Figure 4 As shown in (C), the periodicity is represented by two cycles along one circumference of the measuring circle. Since the measuring circle is a circle with the same size as a finger, the centroid of the finger region FA of the two fingers F and F' is located between the two fingers F and F'. Therefore, the center of the two fingers F and F' is located on the measuring circle, thus obtaining point PMAX at two locations, and obtaining the periodicity of two cycles along one circumference of the measuring circle.

[0054] The above, such as Figures 2 to 4 As shown, if the angular characteristics of the difference value are obtained using the measuring circle, it is possible to distinguish, for example... Figure 2 As shown in (A), the state of inputting by raising one finger F, and as shown in (A). Figure 3 As shown in (A), the input state is achieved by tilting one finger F, and as shown in (A). Figure 4 As shown in (A), the state of inputting by raising two fingers F and F'.

[0055] Here, in the Fourier series expansion, if f(x) is a function of period T, then the following relationships (1) to (3) hold.

[0056] [Formula 1]

[0057]

[0058] in

[0059] [Formula 2]

[0060]

[0061] [Formula 3]

[0062]

[0063] Here, x is replaced by θ. Furthermore, the finger region FA (refer to) is distanced from the two fingers F and F'. Figure 4The difference value of the electrostatic coordinate input unit 110 at a fixed distance r from the center of (B) is set as f(θ), and f(θ) is obtained by Fourier series expansion. f(θ) represents the measured circle. Assuming the period T = 2π, n = 2 in equations (1) to (3), f(θ) is approximated by the following equation (4). Among them, the coefficients a0, a2, and b2 in equation (4) are represented by equations (5) to (7) respectively. The coefficients a2 and b2 are used Figure 7 The coefficients are used to determine the positions of the vectors representing the coordinates PF1 and PF2 of the two fingers F and F' (described later).

[0064] [Formula 4]

[0065]

[0066] [Formula 5]

[0067]

[0068] [Formula 6]

[0069]

[0070] [Formula 7]

[0071]

[0072] Here, in Figure 4 Based on, use Figure 5 as well as Figure 6 The differences in the planar distribution of the difference values ​​and the differences in the angular characteristics of the difference values ​​caused by the difference in the positional relationship between the two fingers F and F' are explained. Figure 5 as well as Figure 6 It is a diagram illustrating the planar distribution of the difference values ​​and the differences in the angular characteristics of the difference values ​​caused by the difference in the positional relationship between the two fingers F and F'.

[0073] like Figure 5 As shown in (A), in the state of inputting the operation with the two fingers F and F' separated and upright, such as Figure 5 As shown in (B), the output of the transform unit 151 becomes two circles for the finger region FA above a given threshold, but the contour lines become the major axis ratio Figure 4 The ellipse shown in (B) is an elongated ellipse. In this case, the difference value of the point PMIN, which is assigned the smallest difference value on the measuring circle, is greater than... Figure 4 The case shown in (B) is small, therefore as Figure 5 As shown in (C), the amplitude ratio of the periodicity of the two periods represented in one revolution along the measuring circle is... Figure 4 (C) is large.

[0074] In addition, such as Figure 6 As shown in (A), when the input is performed while the hand is upright at an angle relative to the X-axis with two additional fingers F and F' attached, as shown in (A), Figure 6 As shown in (B), the output of the transformation unit 151 becomes that the finger region FA above a given threshold is two circles, and the major axis of the ellipse of the contour line has an angle θf (θf > 0) relative to the X-axis. In this case, since the point PMAX with the largest difference value has an angular displacement on the measurement circle, therefore... Figure 6 As shown in (C), the periodic phase displacement represents two periods along one revolution of the measuring circle. The angle θf is an angle in the polar coordinate system, which is the angle between the X-axis and the straight line connecting the coordinates PF1 and PF2 of the two fingers F and F'.

[0075] Here, f(θ) representing the measured circle can be expressed by the following equation (8).

[0076] [Formula 8]

[0077]

[0078] Furthermore, if equation (8) is transformed, equation (9) is obtained. In equation (9), A2, sin2θf, and cos2θf are represented by equations (10) to (12). In equation (10), A2 represents the value of the magnitude of the vector obtained from the coefficients a2 and b2 that determine the vector. The coefficients a1 and a2 are the coefficients of the real parts of each term in the Fourier series expansion. The coefficients b1 and b2 are the coefficients of the imaginary parts of each term in the Fourier series expansion. A0, A1, and A2 are the absolute values ​​of multiple complex numbers formed by the real and imaginary parts of each term in the Fourier series expansion.

[0079] [Formula 9]

[0080]

[0081] [Formula 10]

[0082]

[0083] [Formula 11]

[0084]

[0085] [Formula 12]

[0086]

[0087] If θf is obtained according to equations (11) and (12), it can be expressed by the following equation (13).

[0088] [Formula 13]

[0089]

[0090] Furthermore, using the above calculation results, the coordinates of the two fingers F and F' can be determined. Figure 7 This is a diagram illustrating the coordinates PF1 and PF2 of two fingers F and F'. Figure 7 This represents the centroid PC of the measurement circle and the finger region FA, the point PMAX where the difference value is maximized, and the coordinates PF1 and PF2 of the two fingers F and F', but the finger region FA is omitted. Figure 7 In the diagram, the origin of the XY coordinates is the centroid PC of the finger region FA.

[0091] Here, if we define the distance from the centroid PC to the coordinates PF1 and PF2 of the two fingers F and F' as L, then the coordinates PF1 and PF2 are represented by the distance L and the angle θf. The distance L can be obtained by the following equation (14). If we define the vector from the centroid PC of the finger region FA to the coordinates PF1 and PF2 of the fingers F as vectors PF1 and PF2, then the values ​​of the coefficients K1 and K2 are adjusted so that twice the length of vectors PF1 and PF2 is the distance between the two fingers F and F'. Thus, the distance L between the two fingers F and F' can be obtained by the following equation (14) as twice the length of vectors PF1 and PF2.

[0092] [Formula 14]

[0093] L=K1×A2+K2-----(14)

[0094] Therefore, in Figure 4 Based on (C), if it is possible to Figure 5 (C) and Figure 6 The state of (C) and Figure 2 (C) and Figure 3 By distinguishing the states of (C), it is possible to identify the situation in which two fingers F and F' have performed the operation, and then to calculate the coordinates PF1 and PF2 of the two fingers F and F'.

[0095] Figure 8 This is a flowchart illustrating the processing of the input determination method in Embodiment 1. When the processing begins, the centroid coordinate calculation unit 152 calculates the centroid coordinates based on the output of the transformation unit 151 (step S1). The coordinates calculated in step S1 are the centroid coordinates (xMid, yMid) of the finger region FA whose output of the transformation unit 151 is above a given threshold.

[0096] The period determination unit 153 calculates the difference value at each sampling point every π / 18 rad starting from the point 0 [rad] on the measurement circle (step S2). If there is an intersection 113 of electrodes 111 and 112 at the sampling point, the difference value at the sampling point is the difference value at the intersection 113. If there is no intersection 113 at the sampling point, the period determination unit 153 uses a value obtained by linearly approximating the difference values ​​at multiple intersections 113 around the sampling point.

[0097] The period determination unit 153 calculates the coefficients a2 and b2 of the second term of the Fourier series expansion based on the values ​​of the sampling points of the measurement circle (6) and (7) (step S3).

[0098] The period determination unit 153 uses the coefficients a2 and b2 calculated in step S3 to calculate the angle θf according to formula (13) (step S4).

[0099] The operation determination unit 154 determines whether the centroid coordinates (xMid, yMid) calculated in step S1 are within the given range of the center of the electrostatic coordinate input unit 110 (step S5). This is because if the centroid coordinates (xMid, yMid) are not within the given range of the center of the electrostatic coordinate input unit 110, the measurement circle exceeds the range that can be measured by the electrostatic coordinate input unit 110, and the difference value of the sampling point of the measurement circle cannot be obtained.

[0100] When the operation determination unit 154 determines that the centroid coordinates (xMid, yMid) are within a given range of the center of the electrostatic coordinate input unit 110 (S5: Yes), it determines whether the number of difference values ​​detected in the entire electrostatic coordinate input unit 110 that are above a given threshold (the threshold for difference values) is less than or equal to a given number (step S6). If the number of difference values ​​above the given threshold is greater than the given number, the operation is not performed using two fingers. For example, there are cases where the operation is performed using three or more fingers, or where the operation is performed using the palm.

[0101] When the operation determination unit 154 determines that the number of difference values ​​above a given threshold (the threshold for the difference value) is less than a given number (S6: Yes), it determines whether the magnitude of vector A2, determined by coefficients a2 and b2, is greater than the given threshold (the threshold for the magnitude of the vector) (step S7). When operating with two fingers, vector A2 becomes larger than the given threshold. Furthermore, even when operating with one finger, vector A2 will not become 0 due to measurement errors.

[0102] When the operation determination unit 154 determines that the size of the vector is greater than the given threshold (the threshold of the size of the vector) (S7: Yes), it determines that the operation input was performed by two fingers (step S8).

[0103] The coordinate calculation unit 155 calculates the center coordinates of finger F and finger F' from the two coordinates obtained from the centroid coordinates (xMid, yMid), distance L and angle θf (step S9).

[0104] Furthermore, if in step S5 it is determined that the centroid coordinates (xMid, yMid) are not within the given range of the center of the electrostatic coordinate input unit 110 (S5: No), then the operation determination unit 154 determines that an operation input was performed using one finger (step S10). Additionally, if in step S6 the operation determination unit 154 determines that the number of difference values ​​above a given threshold (the threshold for the difference value) is not below a given number (S6: No), and in step S7 the operation determination determines that the vector size is not greater than a given threshold (the threshold for the vector size) (S7: No), then it also determines that an operation input was performed using one finger (step S10).

[0105] The coordinate calculation unit 155 calculates the centroid coordinates (xMid, yMid) calculated in step S1 as the center coordinates of a finger F (step S11). This concludes the series of processes.

[0106] As described above, by determining whether two cycles can be obtained along one circumference of the measurement circle, it is possible to determine whether the operation input was performed by two fingers or by one finger. Therefore, an electrostatic input device 100 and an input determination method can be provided that can distinguish between a state where one finger is in contact with the electrostatic coordinate input section and a state where two or more fingers are in contact with the electrostatic coordinate input section.

[0107] Furthermore, the above explanation describes how to determine that the input was performed by two fingers when the values ​​of coefficients a2 and b2 are both large enough, and the value of A2 is also large enough. However, it can also be done as follows.

[0108] Calculate A0 using the following formula (15). A0 is the DC component of the electrostatic capacitance detected by the detection unit 140, and is represented by a0.

[0109] [Formula 15]

[0110]

[0111] Alternatively, A0 can be calculated such that if the ratio A2 / A0, which represents the magnitude of the vector, to A0, representing the DC component, is large enough (greater than a first given ratio), it is determined that the operation input was performed using two fingers. By using the ratio of A0, representing the DC component, to A2, representing the magnitude of the vector, as described above, more stable determination accuracy can be ensured, taking into account deviations in the sensitivity of the electrostatic input unit 110.

[0112] Furthermore, if the electrodes 111 and 112 of the electrostatic input unit 110 have a large deviation, the detection sensitivity at each intersection point 113 detected by the detection unit 140 will deviate, and the differential value transformed by the conversion unit 151 will also deviate. In such a case, a setting such as Figure 9 The correction table shown can be corrected by the transformation unit 151 by correcting the difference values ​​calculated for each intersection point 113. Figure 9 This is a diagram representing the calibration table. Here, as an example, it shows a calibration table in matrix form, using 64 calibration values ​​arranged when 8 intersection points 113 are arranged in both the X and Y directions. The conversion unit 151 performs calibration by multiplying the difference value calculated by the conversion unit 151 for each intersection point 113 by the calibration value based on the electrostatic capacitance input from the detection unit 140 to the control unit 150, thus enabling the detection of the center coordinates of the finger with higher accuracy.

[0113] <Implementation Method 2>

[0114] Figure 10 This is a diagram showing the electrostatic input device 200 of Embodiment 2.

[0115] The electrostatic input device 200 includes an electrostatic coordinate input unit 110, a multiplexer 120, a drive circuit 130, a detection unit 140, and a control unit 250. The electrostatic input device 200 has a structure in which the control unit 150 of the electrostatic input device 100 of Embodiment 1 is replaced by the control unit 250. Other structures are the same as those of the electrostatic input device 100 of Embodiment 1; therefore, identical structural elements are labeled with the same symbols and repeated descriptions are omitted.

[0116] The control unit 250 includes a transformation unit 151, a centroid coordinate calculation unit 152, a period determination unit 153, an operation determination unit 154, an approximation processing unit 254, and a coordinate calculation unit 255. The transformation unit 151, the centroid coordinate calculation unit 152, the period determination unit 153, and the operation determination unit 154 are the same as those in the control unit 150 of Embodiment 1.

[0117] When the period determination unit 153 determines that the coordinates represent two periods, the approximation processing unit 254 performs approximation processing using an ellipse to approximate the contour of the range where the difference value transformed by the transformation unit 151 exceeds a threshold. Regarding this approximation processing, using... Figures 12 to 14 To be discussed later.

[0118] The coordinate calculation unit 255 is an example of the second coordinate calculation unit. It calculates the coordinates of the two fingers as the center coordinates of the two foci of the ellipse compared to the two foci obtained by the approximation processing unit 254. More specifically, the coordinate calculation unit 255 calculates the coordinates of the two points on the straight line connecting the two foci of the ellipse obtained by the approximation processing unit 254 and the center of the ellipse, taking the coordinates of the two points that are away from the center from the center by a second distance obtained by multiplying the first distance between the foci and the center by a constant less than 1, and calculates them using the following formula (16). Here, the constant used by the coordinate calculation unit 255 is a constant obtained by a quadratic function of the eccentricity of the ellipse. Here, the coordinates of the two foci are set as (X1, Y1) and (X2, Y2), the length of the major axis is set as a, the length of the minor axis is set as b, the center of the ellipse is set as (X0, Y0), and the constant is set as C. The constant C will be described later. θ represents the slope of the ellipse. The calculation takes into account the relationship between the magnitudes of a and b.

[0119] [Formula 16]

[0120]

[0121] The constant C used in equation (16) is provided by a quadratic function represented by equation (17) obtained by approximation processing of the eccentricity e of the ellipse obtained by approximation processing unit 254.

[0122] [Formula 17]

[0123] The constant C = -6.7833 × e 2 +10.447×e-3.3596-----(17)

[0124] The three coefficients of equation (17) vary depending on the shape of the ellipse. Therefore, the three coefficients of equation (17) are values ​​that can vary depending on the type of electrostatic coordinate input unit 110. The three coefficients of equation (17) are values ​​obtained through experiments by setting the distance between the two fingers to 15mm to 20mm.

[0125] When the finger positioning accuracy can be relatively low, a fixed value can be used for the constant. The constant is a value greater than 0 and less than 1. The constant varies depending on the size and material of the electrostatic coordinate input unit 110, for example, it is 0.7.

[0126] Figure 11This is a graph showing the relationship between the eccentricity e and the measured value of the constant C. Equation (17) is a quadratic function representing the quadratic curve obtained by fitting such a relationship between the eccentricity e and the constant C. Figures 12 to 14 The following section describes the positional relationship between the two foci of the ellipse and the center coordinates of the two fingers.

[0127] Figures 12 to 14 This is a diagram illustrating an example of the positional relationship between the ellipse obtained by the approximation processing unit 254 through approximation processing and the center coordinates of the two fingers calculated by the coordinate calculation unit 255. Figure 12 This indicates the result when two fingers are placed parallel to the X-axis on the electrostatic input section 110. Figure 13 This indicates the result when two fingers are placed parallel to the Y-axis on the electrostatic input section 110. Figure 14 This represents the result when two fingers are placed on the electrostatic input unit 110 in a direction of π / 4 [rad] relative to the X-axis and Y-axis. In all cases, the center-to-center distance between the two fingers is 15 mm.

[0128] Figure 12 (A) Figure 13 (A) Figure 14 Figure (A) shows the distribution of the differential values ​​of the electrostatic capacitance calculated based on the output of the converter 151. There are eight electrodes 111 and 112 each, and 64 intersection points 113. Between each intersection point 113, a linearly interpolated value is calculated based on the value at each intersection point 113. The differential values ​​of the electrostatic capacitance are represented by relative values ​​(0-500) with the maximum value set to 500. Figure 12 (A) Figure 13 (A) Figure 14 In (A), the relative values ​​are divided into five stages representing five ranges: 0-99, 100-199, 200-299, 300-399, and 400-500.

[0129] like Figure 12 (A) Figure 13 (A) Figure 14 As shown in (A), the distributions of ellipses that are longer in the X direction, longer in the Y direction, and longer in the π / 4 [rad] direction relative to the X-axis and Y-axis were obtained respectively.

[0130] exist Figure 12 (B) Figure 13 (B) Figure 14In (B), a black-shaded quadrilateral (■) represents a point where the relative value of the difference is 300, and a black-shaded rhombus (◆) represents two points on the straight line connecting the two foci of the ellipse obtained by fitting multiple points with a relative value of 300 to the center of the ellipse, respectively. These points are located at a second distance from the center, obtained by multiplying the first distance between the foci and the center by a constant. The value of 300 is determined by the contour of the area where the fingertip of finger F contacts the electrostatic input section 110. When there are few electrode intersections 113, if two fingers F and F' are raised and contacted with the electrostatic input section 110, the position where the relative value is 300 becomes an ellipse.

[0131] Here, the ellipse obtained by fitting multiple points with a relative difference value of 300 is obtained by approximating the threshold by the approximation processing unit 254 with the threshold set to 300. This approximation processing approximates the contour of the range where the coordinates of the difference value that has been transformed by the transformation unit 151 exceed the threshold (300 in this case) using an ellipse.

[0132] Furthermore, on the straight line connecting the two foci of the ellipse obtained through approximation to the center of the ellipse, there are two points (◆) that are far from the center and have a second distance that can be obtained by multiplying the first distance between the foci and the center by a constant. These two points are calculated by the coordinate calculation unit 255 using formula (16) and are used as the center coordinates of the two fingers.

[0133] In addition, Figure 12 (B) Figure 13 (B) Figure 14 In (B), the black-painted triangle (▲) represents the center coordinates of the two fingers that were actually measured. These coordinates are obtained by measuring the positions of the two simulated fingers positioned on the electrostatic input unit 110.

[0134] like Figure 12 (B) Figure 13 (B) Figure 14 As shown in (B), the two points (◆) that are calculated by the coordinate calculation unit 255 as the center coordinates of the two fingers and are located away from the center from the second distance obtained by multiplying the first distance by a constant are very close to (▲) the center coordinates of the two fingers that are actually measured, and are roughly consistent.

[0135] The coordinate calculation unit 255 calculates the center of the two points (◆) representing the center coordinates of the two fingers as the center position of the center coordinates of the two fingers. The center position of the center coordinates of the two fingers is represented by a black circle (●), which is the center of the two points (◆) representing the center coordinates of the two fingers.

[0136] Figure 15 as well as Figure 16 It is a graph showing the relationship between the distance Lm between the center coordinates of the two fingers as measured, and the distances Lc1 and Lc2 between the two points calculated by the coordinate calculation unit 255 as the center coordinates of the two fingers. Figure 16 Magnification is equivalent to Figure 15 The horizontal axis and a portion of the vertical axis.

[0137] exist Figure 15 (A) and Figure 16 (A) shows the distance Lc1 between two points calculated by the coordinate calculation unit 255 using equation (16) and the constant (0.7). Figure 15 (B) and Figure 16 (B) shows the distance Lc2 between two points calculated by the coordinate calculation unit 255 using constants from equations (16) and (17).

[0138] exist Figure 15 (A), (B) and Figure 16 In (A) and (B), the horizontal axis represents the measured value, and the vertical axis represents the calculated value. Therefore, the higher the calculation accuracy of the coordinate calculation unit 255, the closer the slope of the solid line shown is to the distance of the straight line. If... Figure 15 (A) and Figure 16 (A) and Figure 15 (B) and Figure 16 If compared with (B), then use Figure 15 (B) and Figure 16 The distance Lc2 calculated using the constant of equation (17) shown in (B) is greater than that calculated using... Figure 15 (A) and Figure 16 The distance Lc1 calculated by the constant (0.7) shown in (A) is closer to a straight line, so it can be confirmed that the calculation accuracy of the coordinate calculation unit 255 is improved compared with the case of using the constant (0.7) by using the constant of formula (17).

[0139] Figure 17 This is a flowchart illustrating the input determination method of Implementation Method 2. Figure 17 The flowchart shown will Figure 8 In the embodiment 1 shown, step S9 is replaced by steps S29A and S29B. Here, the differences will be explained.

[0140] In step S8, if the operation determination unit 154 determines that the operation input was performed by two fingers, the approximation processing unit 254 performs approximation processing to determine the coordinates of the ellipse and its foci (step S29A). Here, if the constant C of equation (17) is used in step S29B, the approximation processing unit 254 can determine the eccentricity e in step S29A in addition to the coordinates of the ellipse and its foci. Furthermore, the ellipse is determined by obtaining the formula representing the ellipse on the XY coordinates of the electrostatic input unit 110. The coordinates of the foci and the eccentricity e can be determined simply based on the formula representing the ellipse.

[0141] Next, the coordinate calculation unit 255 calculates the coordinates of two points on the straight line connecting the two foci of the ellipse obtained by the approximation process of the approximation processing unit 254 and the center of the ellipse using equation (16), which is the second distance obtained by multiplying the first distance between the center and the focus by a constant (0.7) or the constant C of equation (17) (step S29B). This completes the series of processes.

[0142] As described above, by determining whether a periodicity of two cycles can be obtained along one circumference of the measurement circle, it is possible to determine whether the operation input was performed by two fingers or by one finger. Then, by approximation, an ellipse representing the distribution of the difference in electrostatic capacitance generated when the two fingers come into contact with the electrostatic input section 110 is obtained, and the center coordinates of the two fingers can be calculated using the constants of Equation (16). The constants used in Equation (16) are either the constants of Equation (16) or the constant (0.7).

[0143] Therefore, an electrostatic input device 200 and an input determination method are provided that can distinguish between a state where one finger is in contact with the electrostatic coordinate input section and a state where two or more fingers are in contact with the electrostatic coordinate input section. Furthermore, an electrostatic input device 200 and an input determination method are provided that can calculate the center coordinates of two fingers with high accuracy.

[0144] <Implementation Method 3>

[0145] Figure 18 This is a flowchart illustrating the input determination method of Implementation Method 3. Figure 18 The flowchart shown is Figure 8 Based on the flowchart of Embodiment 1 shown, the electrostatic input device 100 of Embodiment 1 can be implemented. Here, as the input determination method of Embodiment 3, a first variation of the input determination method of Embodiment 1 will be described. Figure 18 In the middle, to and Figure 8 The steps shown are the same, and the processing is labeled with the same number.

[0146] In embodiment 3, the operation determination unit 154 uses the coordinates of the maximum or minimum value of the difference value of the electrostatic capacitance corresponding to the distance between the electrostatic coordinate input unit 110 and the finger at each intersection 113, which is transformed by the transformation unit 151, as a reference. Based on the difference value in the coordinates on the circumference of a circle with a given radius centered at the centroid coordinates (xMid, yMid), the real part of the Fourier analysis is calculated. If the size of the real part of the Fourier analysis, which is two cycles along one circumference of the circle, is greater than the threshold (a given threshold), it is determined that an input operation performed by two or more fingers has been performed.

[0147] Here, Fourier analysis includes Fourier series expansion, complex Fourier series expansion, and Fourier transform, and any method can be used. The real part of Fourier analysis refers to the real part of the complex Fourier series, the real part of the Fourier transform, and the cosine of the Fourier series.

[0148] When processing begins, the centroid coordinate calculation unit 152 calculates the coordinates of the operation input based on the output of the transformation unit 151 (step S1). The coordinates calculated in step S1 are the centroid coordinates (xMid, yMid) of the finger region FA whose output of the transformation unit 151 is above a given threshold.

[0149] The operation determination unit 154 determines whether the centroid coordinates (xMid, yMid) calculated in step S1 are within the given range of the center of the electrostatic coordinate input unit 110 (step S5). This is because if the centroid coordinates (xMid, yMid) are not within the given range of the center of the electrostatic coordinate input unit 110, the measurement circle exceeds the range that can be measured by the electrostatic coordinate input unit 110, and the difference value of the sampling point of the measurement circle cannot be obtained.

[0150] When the operation determination unit 154 determines that the centroid coordinates (xMid, yMid) are within a given range of the center of the electrostatic coordinate input unit 110 (S5: Yes), it determines whether the number of difference values ​​detected in the entire electrostatic coordinate input unit 110 that are above a given threshold (the threshold for difference values) is less than or equal to a given number (step S6). If the number of difference values ​​above the given threshold is greater than the given number, the operation is not performed using two fingers. For example, there are cases where the operation is performed using three or more fingers, or where the operation is performed using the palm of the hand.

[0151] If the operation determination unit 154 determines that the number of difference values ​​above the given threshold (the threshold for the difference value) is less than the given number (S6: Yes), then the period determination unit 153 calculates the difference value at each sampling point of π / 18 [rad] from the point 0 [rad] of the measurement circle (step S31). Each sampling point is a point 9 mm away from the center of gravity. Each sampling point is located with the X-axis direction set to 0 [rad] from the center of gravity, and rotated π / 18 [rad] from 0 [rad] each time. The coordinates of each sampling point are represented by the following formula (18).

[0152] [Formula 18]

[0153]

[0154] The processing in step S31 is the same as that in step S2 of embodiment 1. If there is an intersection 113 of electrodes 111 and 112 at the sampling point, the difference value at the sampling point is the difference value at the intersection 113. If there is no intersection 113 at the sampling point, the period determination unit 153 uses the value obtained by linear approximation based on the difference values ​​at multiple intersections 113 around the sampling point.

[0155] The operation determination unit 154 determines the coordinates of the maximum value of the difference at the sampling point on the circumference of the measurement circle (step S32).

[0156] The operation determination unit 154 calculates θf based on the coordinates (xMax, yMax) of the maximum difference value at the centroid coordinates and the sampling point (step S33). θf is calculated by the following formula (19).

[0157] [Formula 19]

[0158]

[0159] After the operation determination unit 154 corrects for θf determined in step S33, it performs Fourier analysis to calculate the coefficient a2 of the real part of the second term of the Fourier series. For example, the value on the circumference of the measured circle is... Figure 6 For the values ​​shown in (C), the angle is corrected to an angle plus 7π / 4 rad for the range from 0 to π / 4 rad, and to a value minus π / 4 rad for the range from π / 4 to 2π rad. The result is a correction of... Figure 4The value shown in (c). Using the corrected value, the coefficients a2 of the real part of the Fourier analysis are calculated based on the difference values ​​at the sampling points on the circumference of a circle with a given radius centered at (xMid, yMid) (step S34). Furthermore, since 0 [rad] is the maximum value, the coefficient b2 of the imaginary part of the second term of the Fourier series is approximately 0 as long as the data has two periods in one cycle (2π). Therefore, by correcting the angle of the coordinates of the maximum value of the electrostatic capacitance difference to 0 [rad] before performing Fourier analysis, the periodicity can be determined solely by the coefficients a2 of the real part. Furthermore, even when corrected so that the angle of the coordinates of the minimum value is 0, the coefficients a2 of the real part of the Fourier analysis are calculated to approximately the same value.

[0160] Operation determination unit 154 determines whether the coefficient a2 of the real part of the Fourier analysis that has two periods along one circle is greater than the threshold (given threshold) (step S35).

[0161] When the operation determination unit 154 determines that the coefficient a2 of the real number part is greater than the threshold (the given threshold), the step S36 of calculating the coordinates of the two fingers is entered.

[0162] The coordinate calculation unit 155 calculates two coordinates—the coordinates of the centroid (xMid, yMid), the coefficient a2 of the real part, and the angle θf—as the center coordinates of the fingers F and F' (step S36). Alternatively, the coordinates of the minimum value can be used instead of the coordinates of the maximum value. The two fingers are located in the direction represented by the angles θf+π / 2 and θf-π / 2 (the angles that differ from θf by π / 2) starting from the coordinates of the minimum difference between the centroid coordinates (xMid, yMid) and the electrostatic capacitance. Therefore, it is sufficient to use either the maximum or minimum value of the difference for calculation.

[0163] Furthermore, in step S5, if the operation determination unit 154 determines that the centroid coordinates (xMid, yMid) are not within the given range of the center of the electrostatic coordinate input unit 110 (S5: No), it is considered that the operation input was performed by one finger, and the coordinate calculation unit 155 calculates the centroid coordinates (xMid, yMid) calculated in step S1 as the center coordinates of one finger F (step S11). Additionally, if in step S6 it is determined that the number of differences exceeding a given threshold is greater than a given number (S6: No), it is considered that the operation input was not performed by two fingers, and the coordinate calculation unit 155 calculates the centroid coordinates (xMid, yMid) calculated in step S1 as the center coordinates of one finger F (step S11). Furthermore, if in step S35 it is determined that the magnitude of coefficient a2 is not greater than a threshold (step S35: No), it is considered that the operation input was performed by one finger, and the coordinate calculation unit 155 calculates the centroid coordinates (xMid, yMid) calculated in step S1 as the center coordinates of one finger F (step S11). That concludes the series of processes.

[0164] As described above, using the coordinates of the maximum or minimum difference value of the electrostatic capacitance as a reference, the real part of the Fourier analysis is calculated based on the difference value in the coordinates on the circumference of a circle with a given radius centered at the centroid coordinates (xMid, yMid). If the size of the real part of the Fourier analysis, which has two cycles along one circumference of the circle, is greater than a threshold (a given threshold), it can be determined that an input operation performed by two or more fingers has been performed.

[0165] Therefore, an electrostatic input device and input determination method are provided that can distinguish between a state where one finger is in contact with the electrostatic coordinate input section at an angle relative to it and a state where two or more fingers are in contact with the electrostatic coordinate input section. Furthermore, an electrostatic input device and input determination method are provided that can calculate the center coordinates of two fingers with high accuracy.

[0166] <Implementation Method 4>

[0167] Figure 19 This is a flowchart illustrating the input determination method of Implementation Method 4. Figure 19 The flowchart shown is Figure 8 Based on the flowchart of Embodiment 1 shown, the electrostatic input device 100 of Embodiment 1 can be implemented. Here, as the input determination method of Embodiment 4, a second variation of the input determination method of Embodiment 1 will be described. Figure 19 In the middle, to and Figure 8 as well as Figure 18 The steps shown are the same, and the processing is labeled with the same number.

[0168] In embodiment 4, the operation determination unit 154 calculates the ratio of the maximum to the minimum value of the difference value in the coordinates of the circle of a given radius centered at the centroid coordinates (xMid, yMid). If the ratio is greater than the second given ratio, it is determined that an input operation performed by two or more fingers has been performed.

[0169] Figure 19 Steps S1, S5, S6, S31, and S11 in the process shown are Figure 18 The steps S1, S5, S6, S31, and S11 shown are the same.

[0170] The operation determination unit 154 determines the maximum and minimum values ​​of the difference values ​​in the coordinates of a circle of a given radius centered at the centroid coordinates (xMid, yMid) (step S41).

[0171] The operation determination unit 154 determines whether the ratio of the maximum value to the minimum value of the determined difference (maximum value / minimum value) is greater than a given ratio (second given ratio) (step S42).

[0172] If the ratio of the maximum to the minimum difference value (maximum value / minimum value) is greater than the second given ratio, the operation determination unit 154 determines the coordinates of the maximum (or minimum) difference value at the sampling point in the measurement circle (step S43). The processing in step S43 is related to... Figure 18 The process in step S32 is the same.

[0173] The period determination unit 153 calculates the angle θf based on the coordinates of the centroid coordinates (xMid, yMid) and the coordinates of the maximum difference value at the sampling point (step S44). The processing in step S44 is similar to... Figure 18 The process in step S33 is the same. Here, the angle θf is calculated based on the coordinates of the maximum value of the difference between the centroid coordinates (xMid, yMid) and the electrostatic capacitance. Alternatively, the coordinates of the minimum value can be used instead of the maximum value. The two fingers are positioned in the direction of angles represented by θf+π / 2 and θf-π / 2 (different from θf being π / 2), starting from the coordinates of the minimum difference between the centroid coordinates (xMid, yMid) and the electrostatic capacitance. Therefore, it is sufficient to calculate using either the maximum or minimum value of the difference.

[0174] The operation determination unit 154 calculates the finger interval D based on the maximum and minimum values ​​of the difference at the sampling points (step S45). The finger interval D is determined by adding a given constant to the ratio of the maximum to the minimum difference (maximum value / minimum value). If the ratio of the major axis to the minor axis of the ellipse is large, the finger interval D is large; if the ratio is small, the finger interval D is small.

[0175] The coordinate calculation unit 155 calculates two coordinates obtained from the coordinates of the centroid (xMid, yMid), the finger spacing D, and the angle θf as the center coordinates of the finger F (step S46).

[0176] Furthermore, in step S5, if the operation determination unit 154 determines that the center of gravity coordinates (xMid, yMid) are not within the given range of the center of the electrostatic coordinate input unit 110 (S5: No), since the operation input was performed by one finger, the coordinate calculation unit 155 calculates the center of gravity coordinates (xMid, yMid) calculated in step S1 as the center coordinates of one finger F (step S11). This concludes the series of processes.

[0177] As described above, the ratio of the maximum to the minimum difference value in the coordinates of a circle of a given radius centered at (xMid, yMid) is calculated. If the ratio is greater than a second given ratio, it can be determined that an input operation was performed by two or more fingers.

[0178] Therefore, an electrostatic input device and input determination method are provided that can distinguish between a state where one finger is in contact with the electrostatic coordinate input section at an angle relative to it and a state where two or more fingers are in contact with the electrostatic coordinate input section. Furthermore, an electrostatic input device and input determination method are provided that can calculate the center coordinates of two fingers with high accuracy.

[0179] <Implementation Method 5>

[0180] Figure 20 This is a flowchart illustrating the input determination method of Implementation Method 5. Figure 21 It is a diagram illustrating the planar distribution of the difference values ​​caused by the difference in the positional relationship between the two fingers F and F', as well as the difference in the angular characteristics of the difference values. Figure 20 The flowchart shown is Figure 8 Based on the flowchart of Embodiment 1 shown, the electrostatic input device 100 of Embodiment 1 can be implemented. Here, as the input determination method of Embodiment 5, a third variation of the input determination method of Embodiment 1 will be described. Figure 20 In the middle, to and Figure 8 , Figure 18 as well as Figure 19 The steps shown are the same, and the processing is labeled with the same number.

[0181] In embodiment 4, the operation determination unit 154 calculates the ratio of the maximum to the minimum value of the difference value in the coordinates of the circle of a given radius centered at the centroid coordinates (xMid, yMid). If the ratio is greater than the third given ratio, and the angle between the first line segment connecting the centroid coordinates and the coordinates of the maximum difference value and the second line segment connecting the centroid coordinates and the coordinates of the minimum difference value is greater than π / 4 [rad] and less than 3π / 4 [rad], or greater than 5π / 4 [rad] and less than 7π / 4 [rad], then it is determined that an input operation performed by two or more fingers has been performed.

[0182] Figure 20 The steps S1, S5, S6, S31, S41, S42, S43, S44, S45, S46, and S11 in the process shown are... Figure 19 The S1, S5, S6, S31, S41, S42, S43, S44, S45, S46, and S11 shown are the same.

[0183] In step S42, the operation determination unit 154 determines whether the ratio of the maximum value to the minimum value of the determined difference (maximum value / minimum value) is greater than a given ratio (third given ratio) (step S42). Figure 20 The given ratio (third given ratio) used in step S42 is compared with Figure 19 The value of the given ratio (second given ratio) used in step S42 is different. Figure 19 In the processing shown, if the ratio of the maximum to the minimum difference (maximum / minimum) is greater than a given ratio (a second given ratio), it is determined that an input operation was performed using more than two fingers. Therefore, as... Figure 3 As shown, it is necessary to determine whether it is one tilted finger F or two tilted fingers F, therefore the given ratio (second given ratio) is set to a relatively large value, set to a value greater than... Figure 20 The given ratio (third given ratio) in step S42 is a large value. In contrast, in Figure 20 In the process shown, in addition to the determination process in step S42, there is also the process in step S52, which will be described later. Therefore, the given ratio (the third given ratio) can be a ratio of Figure 19 The smaller value of the given ratio (second given ratio) in step S42.

[0184] In step S43, when the coordinates of the maximum (or minimum) difference value at the sampling point in the measurement circle are determined, the operation determination unit 154 calculates the angle between the line connecting the centroid coordinates to the coordinates of the maximum difference value and the line connecting the centroid coordinates to the coordinates of the minimum difference value (step S51). Figure 21As shown in (A), when the sampling point representing the maximum value is in the π / 4 [rad] direction and the sampling point representing the minimum value is in the 3π / 4 [rad] direction, since their difference is as follows Figure 21 As shown in (A) and (B), the value is π / 2 [rad], therefore it can be determined that there are two fingers.

[0185] The operation determination unit 154 determines whether the angle formed by the first line segment connecting the centroid coordinates to the coordinates of the maximum difference value and the second line segment connecting the centroid coordinates to the coordinates of the minimum difference value is greater than π / 4 [rad] and less than 3π / 4 [rad], or greater than 5π / 4 [rad] and less than 7π / 4 [rad] (step S52).

[0186] When the operation determination unit 154 determines "yes" in step S52, the process proceeds to step S44. Afterwards, with... Figure 19 Similarly, the processes shown are performed in steps S45 and S46.

[0187] As described above, calculate the ratio of the maximum to the minimum difference value in the coordinates of the circle of a given radius centered at (xMid, yMid). If the ratio is greater than the third given ratio, and the angle between the first line segment connecting the centroid coordinates to the coordinates of the maximum difference value and the second line segment connecting the centroid coordinates to the coordinates of the minimum difference value is greater than π / 4 [rad] and less than 3π / 4 [rad], or greater than 5π / 4 [rad] and less than 7π / 4 [rad], then it can be determined that an input operation was performed by two or more fingers.

[0188] Therefore, an electrostatic input device and input determination method are provided that can distinguish between a state where one finger is in contact with the electrostatic coordinate input section at an angle relative to it and a state where two or more fingers are in contact with the electrostatic coordinate input section. Furthermore, an electrostatic input device and input determination method are provided that can calculate the center coordinates of two fingers with high accuracy.

[0189] The electrostatic input device and input determination method of the present invention have been described above according to exemplary embodiments. However, the present invention is not limited to the specific embodiments disclosed, and various modifications and alterations can be made without departing from the scope of the claims.

[0190] Furthermore, this international application claims priority based on Japanese Patent Application No. 2020-140845, filed on August 24, 2020, the entire contents of which are incorporated herein by reference.

[0191] -Explanation of Figure Markers-

[0192] 100, 200 electrostatic input devices

[0193] 110 Electrostatic Coordinate Input Section

[0194] Electrodes 111 and 112

[0195] 113 intersection

[0196] 120 multiplexer

[0197] 130 drive circuit

[0198] 140 Measurement Department

[0199] 150, 250 Control Unit

[0200] 151 Transformer

[0201] 152. Centroid Coordinate Calculation Section

[0202] 153 Periodic Determination Department

[0203] 154 Operation Judgment Department

[0204] 155 and 255 coordinate calculation section

[0205] 254 Approximation Processing Unit.

Claims

1. An electrostatic input device, comprising: The measurement unit measures the electrostatic capacitance in multiple coordinates of the electrostatic coordinate input unit. The transformation unit obtains the reference value of the electrostatic capacitance and subtracts the reference value from the electrostatic capacitance to transform it into a difference value corresponding to the distance between the electrostatic coordinate input unit and the finger in the plurality of coordinates; The first coordinate calculation unit calculates the centroid coordinates of the contact portion based on the difference values ​​of the plurality of coordinates; The period determination unit determines whether the difference value in the coordinates on the circumference of a circle of a given radius centered on the centroid coordinates represents a periodicity of two periods along one circumference of the circle. as well as If the operation determination unit determines that the two cycles represent periodicity, then it determines that an input operation was performed by two or more fingers.

2. The electrostatic input device according to claim 1, wherein, The operation determination unit performs Fourier analysis on the difference value in the coordinates on the circumference of the circle. If the magnitude of the vector that has two periods along one circumference of the circle is greater than a given threshold value for the magnitude of the vector, it is determined that an input operation has been performed by the two or more fingers.

3. The electrostatic input device according to claim 1, wherein, The operation determination unit performs Fourier analysis on the measured values ​​of each electrode on the circumference of the circle. If the ratio of the magnitude of the vector that forms two periods along one circumference of the circle to the DC component is greater than the first given ratio, it is determined that an input operation performed by the two or more fingers has been performed.

4. The electrostatic input device according to claim 2, wherein, The spacing between the fingers is calculated as twice the size of the vector.

5. The electrostatic input device according to any one of claims 2 to 4, wherein, The direction of the vector relative to the given reference direction is calculated as the direction connecting the two fingers.

6. The electrostatic input device according to claim 1, wherein, The operation determination unit uses the coordinates of the maximum or minimum difference value as a reference to calculate the real part obtained by Fourier analysis of the difference value in the coordinates on the circumference of the circle. If the size of the real part of the Fourier analysis that makes two cycles along one circumference of the circle is greater than other given thresholds, it is determined that an input operation performed by the two or more fingers has been performed.

7. The electrostatic input device according to claim 1, wherein, The operation determination unit calculates the ratio of the maximum to the minimum value of the difference value in the coordinates on the circumference of the circle. If the ratio is greater than the second given ratio, it is determined that an input operation has been performed by the two or more fingers.

8. The electrostatic input device according to claim 1, wherein, The operation determination unit calculates the ratio of the maximum to the minimum difference value in the coordinates on the circumference of the circle. If the ratio is greater than a third given ratio, and the angle between the first line segment connecting the centroid coordinate and the coordinate of the maximum value and the second line segment connecting the centroid coordinate and the coordinate of the minimum value is greater than π / 4 [rad] and less than 3π / 4 [rad], or greater than 5π / 4 [rad] and less than 7π / 4 [rad], then it is determined that an input operation performed by two or more fingers has been performed.

9. The electrostatic input device according to any one of claims 1 to 4, wherein, The electrostatic input device further includes: The approximation processing unit, if determined by the period determination unit to represent the periodicity of the two periods, approximates the contour of the range where the coordinates of the difference value exceeding the threshold exist using an ellipse; and The second coordinate calculation unit calculates the center coordinates of the two fingers as the position that is closer to the center of the ellipse than the two foci of the ellipse.

10. The electrostatic input device according to claim 9, wherein, The second coordinate calculation unit calculates the coordinates of two points on the straight line connecting the two foci of the ellipse and the center of the ellipse, which are two points that are separated from the center by a second distance obtained by multiplying the first distance between the foci and the center by a constant less than 1, as the center coordinates of the two fingers.

11. The electrostatic input device according to claim 10, wherein, The constant is a constant obtained as a quadratic function of the eccentricity of the ellipse.

12. The electrostatic input device according to any one of claims 1 to 4, wherein, The transformation unit corrects the difference value by multiplying it by a correction value used to correct the electrostatic capacitance in multiple coordinates of the electrostatic coordinate input unit.

13. An input determination method, wherein a computer performs the following processing: The reference value of the electrostatic capacitance in multiple coordinates of the electrostatic coordinate input unit is obtained, and the reference value is subtracted from the electrostatic capacitance to transform it into a difference value corresponding to the distance between the electrostatic coordinate input unit and the finger in the multiple coordinates; The centroid coordinates of the contact area are calculated based on the difference values ​​of the plurality of coordinates; Determine whether the difference value in the coordinates on the circumference of a circle of a given radius centered on the centroid coordinates represents a periodicity of two cycles along one circumference of the circle. as well as If it is determined to represent the periodicity of the two cycles, it is determined that an input operation was performed using two or more fingers.

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