JP2017021540A - Detection circuit and touch sensor system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent erroneous detection of an object in a floating state on a touch panel while maintaining the advantages in a mutual capacitance system.SOLUTION: An object which makes a touch on a touch panel 5 is determined whether the object is an object in a ground state or an object in a floating state on the basis of a comparison result between the total of capacitance signals of the capacitances in a predetermined range read out from the touch panel 5 and a predetermined threshold level.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a detection circuit and a touch sensor system for detecting a touch of an object on a mutual capacitive touch panel.

  Conventionally, as a result of considering response speed, detection sensitivity, and coordinate extraction accuracy, a capacitive touch panel is often used in touch sensor systems. The capacitive touch panel is roughly divided into two types, one is a self-capacitance touch panel, and the other is a mutual capacitive touch panel. Since the self-capacitance type touch panel has a drawback that multi-touch detection is difficult, a mutual capacitance type touch panel is used in many touch sensor systems.

  However, there is a problem with the mutual capacitive touch panel. Since this type of touch panel reads the capacitance between the electrodes placed inside it, it can detect capacitance signals with a small parasitic capacitance loaded on the electrodes compared to the self-capacitance method that detects the ground capacitance. Many. Therefore, in the mutual capacitance type touch panel, when an object in a floating state with a small impedance such as a metal or a water droplet comes into contact with the touch panel, the value of the capacitance signal corresponding to this tends to increase. As a result, there may arise a problem that the contact of the floating object with the touch panel is erroneously detected as a touch with a finger or a passive pen.

  In order to improve the convenience of the user when using the touch sensor system, preventing such erroneous detection is one of the problems. As one of the technologies aimed at solving this problem, a touch screen device having both a self-capacitance method and a mutual capacitance method is disclosed in Patent Document 1.

US Patent Publication No. 8,982,097 (issued March 17, 2015)

  However, the touch sensor system of Patent Document 1 has a problem that the implementation cost increases because a configuration for executing two types of detection methods is required. Furthermore, there are a disadvantage that the performance of multi-touch detection, which is an advantage of the mutual capacitance method, and a reaction speed of touch detection are lowered.

  The present invention has been made to solve the above problems. The purpose is to avoid erroneous detection of floating objects on the touch panel while maintaining the advantages of the mutual capacitance method.

  In order to solve the above problems, the detection circuit according to the present invention includes a calculation unit that calculates a sum of capacitance signals of each capacitance within a predetermined range read from a mutual capacitance type touch panel, And a determination unit that determines whether an object that has touched the touch panel is a ground object or a floating object based on a result of comparison with a predetermined threshold.

  According to one aspect of the present invention, there is an effect that erroneous detection of an object in a floating state on a touch panel can be avoided while maintaining the advantage of the mutual capacitance method.

It is a block diagram which shows the principal part structure of the touch sensor system which concerns on Embodiment 1 of this invention. It is a schematic diagram which shows the detail of the mutual capacity | capacitance type touchscreen which concerns on Embodiment 1 of this invention. In Embodiment 1 of this invention, it is a schematic diagram which shows the mode of a touchscreen when the objects of ground states, such as a finger | toe, are contacted. In Embodiment 1 of this invention, it is a schematic diagram which shows the mode of a touchscreen when the objects of floating states, such as a water drop, are contacted. It is a figure which shows the capacity | capacitance distribution of the state in which the object (finger) of the ground state contacted the touch panel in Embodiment 1 of this invention. It is a figure which shows the volume distribution of the state in which the object (water droplet) of the floating state contacted the touch panel in Embodiment 1 of this invention. It is a graph which shows the one-dimensional capacity | capacitance signal in Embodiment 1 of this invention. In Embodiment 3 of the present invention, when objects (finger and passive pen) having different ground states are simultaneously placed on a certain sense line, and both a ground state object and a floating state object are placed on a certain sense line. It is a figure which shows the mode of the touch panel in the case of being touched. It is a flowchart explaining the flow of a process in the touch sensor system which concerns on each embodiment of this invention.

Embodiment 1
1st Embodiment which concerns on this invention is described below based on FIGS.

(Configuration of touch sensor system 1)
FIG. 1 is a block diagram showing a main configuration of a touch sensor system 1 according to Embodiment 1 of the present invention. As shown in this figure, the touch sensor system 1 includes a touch panel 5 and a detection circuit 10. The touch panel 5 has a touch surface that receives a touch with a user's finger or a passive pen used by the user, and the detection circuit 10 detects a touch with the finger or the passive pen on the touch surface.

The touch panel 5 includes a plurality of conductive drive lines DL _{1 to} DL _n (n is an integer of 2 or more) arranged in parallel to each other along a first direction (horizontal direction) in the touch surface, A plurality of conductive sense lines SL _{1 to} SL _m (m is an integer of 2 or more) arranged in parallel with each other along a second direction (vertical direction) orthogonal to the direction, and drive lines DL _{1 to} DL _n And a plurality of capacitances (not shown in FIG. 1) respectively formed at the intersections of the sense lines SL _{1 to} SL _m . In the present embodiment, each capacitance formed on the matrix in the touch panel 5 functions as each sensor for touch detection in the touch sensor system 1.

  As shown in FIG. 1, the detection circuit 10 includes a driver 11, a sense amplifier 12, a timing generator 13, an AD converter 14, a capacitance distribution calculation unit 15, a touch recognition unit 16 (specification unit), and a total value calculation unit 17 (calculation). Part) and an erroneous touch suppression part 18 (determination part).

The driver 11 drives each electrostatic capacitance in the touch panel 5 by applying a voltage to the drive lines DL _{1 to} DL _n in the touch panel 5. The driver 11 can drive each capacitance sequentially or in parallel. During sequential drive, drive signals are sequentially supplied to the drive lines, while during parallel drive, drive signals are simultaneously supplied to all drive lines based on the code sequence.

The sense amplifier 12 reads the voltage corresponding to each electrostatic capacitance driven by the driver 11 through the sense lines SL _{1 to} SL _m . During sequential driving, the sense amplifier 12 reads, from each sense line, a voltage corresponding to the capacitance formed at the intersection of each sense line with the drive line supplied with the drive signal. On the other hand, at the time of parallel driving, a linear sum of all voltages corresponding to all capacitances in each sense line is read from each sense line. Any voltage read from each sense line is output to the AD converter 14.

  The timing generator 13 controls the operation timing of the driver 11, the sense amplifier 12, and the AD converter 14. The timing generator 13 of the present embodiment generates a signal that defines the operation of the driver 11 and outputs the signal to the driver 11, generates a signal that defines the operation of the sense amplifier 12, outputs the signal to the sense amplifier 12, and AD A signal that defines the operation of the converter 14 is generated and output to the AD converter 14.

The AD converter 14 AD-converts the voltage corresponding to each capacitance read through the sense lines SL _{1 to} SL _m and supplies the converted digital data to the capacitance distribution calculation unit 15 as a capacitance signal. .

  The capacitance distribution calculation unit 15 calculates the distribution (capacitance distribution) of each capacitance in the touch panel 5 based on the capacitance signal supplied from the AD converter 14.

  The touch recognition unit 16 determines whether or not there is a touch by an object on the touch panel 5. At that time, the touch recognition unit 16 first sets a predetermined detection region for the capacity distribution supplied from the capacity distribution calculation unit 15. This area has a width corresponding to, for example, 4 × 4 intersections. The touch recognition unit 16 compares each capacitance value corresponding to each intersection included in the detection region with a preset intensity threshold. And it is determined whether the electrostatic capacitance of the intersection more than a predetermined number is higher than an intensity | strength threshold value.

  Furthermore, the touch recognition unit 16 sets a predetermined peripheral region that includes the detection region and is wider than the above-described detection region for the capacitance distribution supplied from the capacitance distribution calculation unit 15. This area has a width corresponding to, for example, 7 × 7 intersections. The touch recognition unit 16 compares each capacitance value corresponding to each intersection included in this peripheral region with a preset peripheral threshold value. And it is determined whether the electrostatic capacitance of the intersection more than a predetermined number is higher than a surrounding threshold value.

  The touch recognition unit 16 determines whether there is a touch of an object with respect to the set detection area based on the two determination results described above. When it is determined that there is a touch, the touch recognition unit 16 calculates the touch coordinates in the detection area and outputs the calculated touch coordinates to the total value calculation unit 17.

  The total value calculation unit 17 calculates the total sum of the capacitances corresponding to the intersections within a predetermined range with reference to the coordinates extracted from the area recognized as touch by the touch recognition unit 16. This total value is used to determine the degree of influence of interference on the drive signal caused by placing a floating object on the touch panel 5.

  The erroneous touch suppression unit 18 compares the total value calculated by the interference signal calculation unit 17 with a preset threshold value, and based on the comparison result, the object that actually touched the coordinates determined to be touched is It is determined whether the object is a grounded object (such as a user's finger or a passive pen) or a floating object (such as a water drop or a metal piece). When it is determined that the object touching the detection area is an object in the ground state, the touch information (touch coordinates, etc.) of the object is output to the host device 2 connected to the touch sensor system 1.

  Based on the touch information supplied from the erroneous touch suppression unit 18, the host device 2 controls application software currently active in the host device 2 so as to execute a predetermined process according to touch coordinates, for example.

(Details of total value calculation)
The calculation of the total value by the total value calculation unit 17 will be described below using a specific example. FIG. 2 is a schematic diagram showing details of the mutual capacitive touch panel 5 according to the first embodiment of the present invention. In order to simplify the description, the case where the touch panel 5 has four drive lines DL _{1 to} DL ₄ and four sense lines SL _{1 to} SL ₄ will be described.

In the example of FIG. 2, capacitances C _{11 to} C ₄₄ are formed at the intersections of the drive lines DL _{1 to} DL ₄ and the sense lines SL _{1 to} SL ₄ . More specifically, capacitances C _{11 to} C ₁₄ are formed at the intersections of the sense lines SL _{1 with} the drive lines DL _{1 to} DL ₄ . Capacitances C _{21 to} C ₂₄ are formed at the intersections of the sense lines SL _{2 with} the drive lines DL _{1 to} DL ₄ . Capacitances C _{31 to} C ₃₄ are formed at the intersections of the sense lines SL _{3 with} the drive lines DL _{1 to} DL ₄ . Capacitances C _{41 to} C ₄₄ are formed at the intersections of the sense lines SL _{4 with} the drive lines DL _{1 to} DL ₄ .

Drive signals are supplied to the drive lines DL _{1 to} DL ₄ , respectively, and capacitances for these are read through the sense lines SL _{1 to} SL ₄ . The mutual capacitive touch sensor system 1 reads the signal change at this time as the value of each of the capacitances C ₁₁ to ₄₄ .

(Ground object contact)
FIG. 3 is a schematic diagram showing a state of the touch panel 5 when a grounded object such as a finger is touched in Embodiment 1 of the present invention. Hereinafter, an example in which a drive signal is supplied to the drive line DL ₂ and this drive signal is read as a capacitance signal from the sense line SL ₂ via the capacitance C ₂₂ will be described.

Unlike the case where nothing is touched on the touch panel 5 as shown in FIG. 2, when a grounded object is touched on the touch panel 5 as shown in FIG. 3, the contact range 31 and the ground 32 on the touch panel 5. A constant coupling capacitance C _gnd is formed between the two. Thus, some of the drive signal supplied to the drive line DL ₂ is flows through the 32-side ground through the coupling capacitor C _gnd, signal to be read through the sense line SL ₂ is reduced by that amount. The detection circuit 10 detects the contact of the object with respect to the contact range 31 by reading the change (decrease) in the signal value.

(Contact with floating object)
FIG. 4 is a schematic diagram showing a state of the touch panel 5 when a floating object such as a water droplet is touched in Embodiment 1 of the present invention. In the following, an example in which drive signals are sequentially supplied to the drive lines DL ₂ and DL ₃ and the respective drive signals are sequentially read as capacitance signals from the sense line SL ₂ via the capacitances C ₂₂ and C _23. explain.

In FIG. 3, the floating object is in contact with the touch panel 5. Since the floating object is not connected to the ground 32, a current path other than the current path via the capacitance C ₂₂ is formed in the contact range 41 of the floating object on the touch panel 5. In the other current path, a certain coupling capacitance is formed between the touch panel 5 and the floating object. Part of the charge of the driving signal supplied to the drive line DL ₂ is charged to the coupling capacitance. Thus, the drive signal applied to the capacitance C ₂₂ is reduced, the value of the capacitance signal read through the sense line SL ₂ is reduced as compared with the case of FIG.

After the value of the capacitance C ₂₂ is read, the electric charge charged in the coupling capacitance formed between the contact area 41 and the object in a floating state of the touch panel 5 is left. In this state, it supplies a drive signal to the drive line DL _3, through the electrostatic capacitance C _23, consider the case of reading the capacitance signal from the sense line SL _2. In this case, the driving signal supplied to the drive line DL _3, charge charged in the coupling capacitance is the sum of between the contact range 41 and the object in a floating state, it is read from the sense line SL ₂ as capacitance signal . As a result, the value of the capacitance C ₂₃ is increased as compared with the case of FIG.

As described above, the signal value of the electrostatic capacitance C ₂₂ is reduced by the charge amount of electric charge, while the signal value in the capacitance C ₂₃ next to it, increased by charging charge amount. Therefore, when these signal values are added together, the decrease amount and the increase amount of the charge charge in each signal value are offset. As a result, the sum of the signal values becomes equal to the sum of the capacitance C ₂₂ and the capacitance C ₂₃ when no object is touched on the touch panel 5 as shown in FIG.

  This principle has been clarified by the inventors of the present invention. The present invention utilizes this principle.

In the above, the case where the touch panel 5 is sequentially driven has been described as an example, but the same principle holds true when the touch panel 5 is driven in parallel. In the case of the parallel drive system, drive signals are simultaneously supplied to the drive lines DL _{1 to} DL ₄ . Thus, the influence by the driving signal supplied to the drive line DL ₃ becomes to appear in the value of the capacitance C _22. However, as in the sequential driving method, the sum of the signal value of the capacitance C _{22 and} the signal value of the capacitance C ₂₃ is static when no object is in contact with the touch panel 5 as shown in FIG. equal to the sum of the signal value of the signal value and the capacitance C ₂₃ of the capacitance C _22.

(Capacity distribution)
Next, a specific example of this embodiment will be described by referring to the capacity distribution created by the capacity distribution calculation unit 15.

  FIG. 5 is a diagram illustrating a capacitance distribution in a state where an object (finger) in a ground state is in contact with the touch panel 5 in Embodiment 1 of the present invention. FIG. 6 is a diagram illustrating a volume distribution in a state where an object (water droplet) in a floating state is in contact with the touch panel 5 in Embodiment 1 of the present invention. 5 and 6, the electrostatic capacitance distribution (capacitance distribution) is shown as a three-dimensional capacitance signal diagram. In the graph 51 of FIG. 5, the capacitance signal values are all positive. On the other hand, in the graph 61 of FIG. 6, the value of the capacitance signal is positive or negative. Based on the three-dimensional capacitance distribution shown in FIG. 5 and FIG. 6, the sum of the capacitance signals at the respective intersections in each sense line is taken and illustrated as the total value of the one-dimensional capacitance signal with the sense line number as the horizontal axis become that way.

  FIG. 7 is a graph showing a one-dimensional capacitance signal in Embodiment 1 of the present invention. In FIG. 7, a dotted line 70 indicates a one-dimensional capacitance signal sum calculated from the capacitance distribution based on the contact of the grounded object (finger) shown in FIG. On the other hand, the solid line 71 indicates a one-dimensional capacitance signal sum calculated from the capacitance distribution based on the contact of the floating object (water droplet) shown in FIG.

  As shown by the solid line 71 in FIG. 7, for the capacitance distribution based on the contact of a grounded object such as a finger, the sum of the signal values of the respective capacitances at the respective intersections on the sense line included in the contact range is obtained. For example, the sum is a large value reflecting the touch of the finger.

  On the other hand, as indicated by a dotted line 70 in FIG. 7, for the capacitance distribution based on a floating object such as a water drop, the sum of the signal values of the respective capacitances at the respective intersections on the sense line included in the contact range is obtained. For example, the capacitance signal value is canceled so as to cancel the interference of the drive signal between the adjacent intersections in the extending direction of the sense line. As a result, the sum corresponding to the contact of the floating object is much smaller than the sum corresponding to the contact of the ground object.

  Based on the difference of the sum, it is possible to distinguish whether the object touched on the touch panel 5 is a grounded object or a floating object. For example, by comparing the calculated sum with a preset threshold, if the sum is equal to or greater than the threshold, it is determined that an object in the ground state is in contact with the touch panel 5, while if the sum is less than the threshold. It is determined that an object in a floating state is in contact with the touch panel 5.

(Improved accuracy)
Next, a specific example of a device for improving the accuracy of determination between an object in a ground state and an object in a floating state will be described below.

As shown in FIG. 3, when an object (such as a finger) whose touch is to be detected extends over a plurality of sense lines, the total sum of capacitances is individually calculated for the plurality of sense lines. For example, when the contact area 31 overlaps the sense lines SL ₂ and SL ₃ as shown in FIG. 3, the sum of the capacitances C ₂₁ , C ₂₂ , C ₂₃ , and C ₂₄ on the sense line SL ₂ (first (Sum), and further, the sum (second sum) of the capacitances C ₃₁ , C ₃₂ , C ₃₃ and C ₃₄ on the sense line SL ₃ is calculated.

  For example, when it is desired to further improve the touch detection accuracy of an object in the ground state, when at least one of the totals calculated from the plurality of sense lines is equal to or greater than a preset reference value, do it. Conversely, when it is desired to improve the false detection avoidance system for floating objects, when all of a plurality of sums are equal to or greater than a preset reference value, the touch of a ground object may be used.

If the range in which the capacitance signal is detected by the contact of the grounded object is known in advance, the range in which the capacitance signal is detected by the contact of the grounded object is selected as the range where the total capacitance on the sense line is taken. It may be limited to. For example, in FIG. 3, the sum of the capacitance C ₂₂ and the capacitance C ₂₃ included in the contact range 31 on the sense line SL ₂ may be taken. Accordingly, it is possible to further improve the determination accuracy when distinguishing between the ground state object and the floating state object.

  As described above, according to the present embodiment, the touch sensor system 1 can accurately discriminate between the capacitive signal caused by the floating object and the capacitive signal caused by the ground object. Thereby, it can prevent beforehand that the contact of the object in the floating state with respect to the touch panel 5 is erroneously detected as a touch by the object in the ground state.

[Embodiment 2]
Embodiment 2 according to the present invention will be described below. Each member common to the above-described embodiment is denoted by the same reference numeral, and detailed description thereof is omitted.

  The touch sensor system 1 can also detect a touch with a passive pen having a small tip diameter other than a finger as an object in a ground state. Generally, in order to read a passive pen with a small diameter, it is necessary to increase the SNR (signal-noise ratio) of the touch sensor system 1. In the present embodiment, in the mutual capacitive touch sensor system 1, parallel drive is used to increase the SNR.

  In the parallel drive method, the drive signal is supplied to all the drive lines simultaneously, and then the capacitance signal read from the sense line is decoded using a signal corresponding to the drive signal. Thereby, a capacitance signal (mutual electrostatic signal) obtained from the capacitance at each intersection in the touch panel 5 is generated.

  In the parallel drive method, since drive signals are simultaneously applied to all drive line lines, in principle, the capacity signals at the respective intersections to be decoded are all not only signals corresponding to the supplied drive signals supplied to the corresponding drive lines, but also all of them. The signal component of each drive signal supplied to the drive line is included. Normally, the influence of the drive line drive signals other than the drive line drive signals corresponding to the intersections on the capacitance signal is small. However, this effect cannot be ignored for reading small capacitive signals generated by passive pens. That is, when a large change occurs in the capacitance at other locations (other intersections) than the desired intersection (capacitance) on the sense line, it is difficult to determine a small capacitance signal generated at the desired intersection.

  The determination method based on the calculation of each sum for a plurality of sense lines described in the first embodiment is difficult to apply to touch with a passive pen. This is because the range in which the passive pen touches the touch panel 5 due to the small diameter is very narrow, and the range in which the capacitance changes due to the touch of the passive pen (the range in which the capacitance signal is detected) becomes very narrow. .

  In order to distinguish contact (touch) with a small-diameter passive pen from contact with a floating object, it is necessary to devise a range in which the sum of the capacitance signals is taken. As described above, in the parallel drive system, the drive signal components of all the drive lines are included in the capacitance signal from each intersection. However, the sum of all the capacitance signals from the intersection on a certain sense line is equal to the sum in an ideal state in which only the capacitance signal based on the drive signal of the corresponding drive line is read through the sense line. This is because there is no signal that affects the capacitance signal read from the sense line other than the drive signal.

  If the calculated sum is not equal to the sum in the ideal state, there is another signal source other than the signal source that supplies the drive signal, which supplies the signal to the sense line, or other than the sense line There is a way to escape charges. The case where there is a charge escape path other than the sense line is a case where an object in the ground state is placed on the touch panel 5. A floating object has no escape route for charges. Therefore, when a floating object is placed on the touch panel 5, the sum of the capacitance signals calculated from a certain sense line is equal to the sum of the ideal states. That is, as a result of taking the sum of the capacitance signals from all the intersections on the sense line, the sum being close to zero means that the grounded object is not placed on the intersection corresponding to the sense line.

  The touch sensor system 1 of the present embodiment distinguishes an object in the ground state from an object in the floating state by using this principle. That is, the erroneous touch suppression unit 18 calculates the sum for determination by adding all the capacitance signals from all the intersections on a certain sense line. When the sum exceeds the threshold value, it is determined that the object in the ground state is touched on the touch panel 5. On the other hand, if the sum is less than the threshold value, it is determined that the object in the floating state is touched on the touch panel 5. Thereby, since a small capacitance signal due to a small interference of the drive signal when a passive pen with a small diameter comes into contact with the touch panel 5 can be taken into account, it is possible to accurately distinguish between the passive pen and the floating object.

[Embodiment 3]
A third embodiment according to the present invention will be described below with reference to FIGS. Each member common to the above-described embodiment is denoted by the same reference numeral, and detailed description thereof is omitted.

  In the present embodiment, when objects (finger and passive pen) having different ground states are placed simultaneously on a certain sense line, and both a ground state object and a floating state object are placed on a certain sense line. In this case, a method for distinguishing these will be described. In order to realize this, further ingenuity is required as compared with the first and second embodiments.

FIG. 8 shows a case where objects having different ground states (finger and passive pen) are placed on a certain sense line at the same time in Embodiment 3 of the present invention, and a ground state object and a floating state object on a certain sense line. It is a figure which shows the mode of the touch panel 5 when both are put. In this figure, the touch panel 5 having the drive lines DL _{1 to} DL ₁₆ and the sense lines SL _{1 to} SL ₁₀ will be described as an example. In the figure, in order to avoid complexity, each capacitance formed at each intersection is not shown.

8, focusing on the sense line SL ₃ and SL _4, on top of both of these fingers 81 and pen 82 is located. In this situation, a higher capacitance signal is read from the contact range of the finger 81, while a lower capacitance signal is read from the contact range of the pen 82.

Here, taking the sum of all the intersections of the capacitance signal on the sense line SL _3, since a high capacitance signal from the intersection of the placed position of the finger 81 is reflected to the sum, the value of the sum becomes extremely large End up. Therefore, when the touch of the pen 82 is determined based on this sum, it can be correctly determined if it is an actual touch by the pen 82. However, in the case where the touch is actually caused by a floating object in a narrow range, the sum is similarly below the threshold value. Since it becomes large, this is erroneously determined to be a touch of the pen 82.

To avoid this, in the present embodiment, when calculating the sum of the capacitance signal on the sense line SL _3, to calculate the sum for the finger 81, and a sum of the pen 82, respectively. At that time, when a predetermined reference value is provided and the sum is calculated for the contact range of the finger 81 where the capacitance signal is larger than this, all intersections within the contact range of the finger 81 (in FIG. Sum the capacitance signal at the intersection. Thereby, the touch of the finger 81 can be accurately determined as in the first embodiment.

On the other hand, when calculating the sum of the pen 82, among all the intersection of capacitance signal on the sense line SL _2, so that, except for large capacity signal than the predetermined reference value. In the example of FIG. 8, the capacitance signals at the intersections for three lines included in the contact range of the finger 81 are not included in the sum, and the sum of the capacitance signals at each other intersection is taken. As a result, since the large capacitance signal derived from the finger 81 is not reflected in the sum for the pen 82, the touch of the pen 82 can be accurately determined as in the second embodiment. Further, on the sense line SL ₂ that the pen 82 is placed, the finger 81 without any floating object that generates a capacitive signal comparable capacity signal generated by the contact of the pen 82 may also be placed. Therefore, in order to cope with this, a range in which a capacitance signal larger than a predetermined reference value is excluded is a predetermined number (for example, three lines) of sense lines based on the coordinates calculated by the touch recognition unit 16. Make it a range. Thereby, it is possible to prevent the floating object from being erroneously detected as the pen 82.

Next, focusing on the sense lines SL _{8 to} SL ₁₀ in FIG. 8, both the floating object 83 and the finger 84 are placed on these lines. Thus, for example, it sums all full intersection capacity signal on the sense line SL _8, the capacitance signal from these both objects are added, the value of the calculated sum is very large. Further, it is necessary to use the sum calculated in this way for the touch determination of the floating object 83 and the finger 84.

  As a result, the finger 84 is accurately determined as a touch by an object in the ground state because the calculated sum is larger than the threshold value. On the other hand, since the sum of the floating object 83 is larger than the threshold value, it is determined that the touch is caused by the grounded object, similarly to the finger 84, and thus erroneous detection occurs.

  In order to prevent this, the sum for the floating object 83 and the sum for the finger 84 are calculated separately. For example, if the capacitance signal from the floating object 83 is as large as the capacitance signal from the finger 84, the total for the floating object 83 is set to a predetermined number (eg, three) drive lines within the contact range of the floating object 83. Calculated as the sum of the minute capacity signals. Similarly, the sum for the finger 84 is calculated as the sum of the capacity signals for a predetermined number (for example, three) of drive lines within the contact range of the finger 84. Thereby, the touch of the floating object 83 and the finger 84 can be accurately determined.

  If both the floating object 83 and the finger 84 are placed within the three drive lines on the touch panel 5, these cannot be clearly distinguished. However, since the distance between the two drive lines is usually about 5 mm, the size of the floating object 83 and the finger 84 can be said to be sufficiently wide in the range of three. That is, the floating object 83 and the finger 84 can be distinguished sufficiently accurately by taking the sum of the capacitance signals in the range of three drive lines.

  As described above, in the present embodiment, a predetermined threshold is provided for the capacitance signal, and the sum of the capacitance signals is calculated in a narrower range for intersections where the capacitance signal is larger than the threshold, while the capacitance signal is larger than the threshold. For intersections where is small, the sum is calculated over a wider range. That is, each capacitance signal that is larger than the threshold is used to calculate the sum for discrimination between the finger and the floating object, while each capacitance signal that is smaller than the threshold is used for the passive pen and the floating object. It is used for calculation in the sum for discrimination. Thus, when objects with different ground states (finger and passive pen) are placed on a sense line at the same time, and when both a ground object and a floating object are placed on a sense line, Can be accurately distinguished.

(Process flow)
A processing flow of the touch sensor system 1 in the present embodiment will be described below with reference to FIG. FIG. 9 is a flowchart for explaining the flow of processing in the touch sensor system 1 according to each embodiment of the present invention.

  As shown in this figure, first, the capacitance distribution calculation unit 15 calculates the capacitance distribution in the touch panel 5 (S1). Next, the touch recognition unit 16 specifies the object that has touched the touch panel as either a finger or a passive pen. At that time, the touch recognition unit calculates the touch coordinates and touch type (finger or passive pen) of the object on the touch panel 5 based on the size of each capacitance signal in the capacitance distribution and the shape of the capacitance distribution (S2).

  Next, the total value calculation unit 17 determines whether or not the calculated touch type is a pen touch (S3). If the determination result in S3 is YES, the total value calculation unit 17 calculates the total sum of the capacitance signals within a preset range corresponding to the passive pen with reference to the pen touch coordinates (S4). On the other hand, if the result of the determination in step S3 is No, the sum total value calculation unit 17 calculates the sum total of capacitance signals within a preset range including finger touch coordinates (S5).

  After S4 or S5, the erroneous touch suppression unit 18 determines whether the calculated sum is equal to or greater than a preset threshold value (S6). If the determination result in step S6 is YES, the erroneous touch suppression unit 18 outputs touch information including touch coordinates and the like to the host device 2 (S7). On the other hand, if the determination result in step S6 is No, the erroneous touch suppression unit 18 does not output touch information to the host device 2 (S8). After S7 or S8, the process shown in FIG. 8 ends.

[Summary]
The detection circuit according to the first aspect of the present invention includes a calculation unit (total value calculation unit 17) that calculates a sum of capacitance signals of respective capacitances within a predetermined range read from a mutual capacitance type touch panel, and the total And a determination unit (erroneous touch suppression unit 18) that determines whether an object that has touched the touch panel is a ground state object or a floating state object based on a comparison result between the threshold value and a predetermined threshold value. It is characterized by being.

  According to the above configuration, when an object in a floating state touches the touch panel, the influence of interference on each capacitance due to the drive signal is canceled by calculating the sum of the capacitance signals within a predetermined range. Therefore, the sum of the capacitance signals when the floating state object touches the touch panel is significantly smaller than the sum of the capacity signals when the ground state object touches the touch panel. Based on this principle, the detection circuit accurately detects that an object in the ground state touches the touch panel if the calculated sum is equal to or greater than the threshold value, while an object in the floating state touches the touch panel if the sum is less than the threshold value. Can be determined.

  As described above, according to the present invention, erroneous detection of an object in a floating state on the touch panel can be avoided while maintaining the advantage of the mutual capacitance method.

  In the detection circuit according to aspect 2 of the present invention, in the aspect 1, the calculation unit calculates a sum of a predetermined number of capacitance signals in the extending direction of the sense line of the touch panel.

  According to said structure, since the influence of the interference of a drive signal can be canceled effectively, the precision of determination can be improved.

  The detection circuit according to aspect 3 of the present invention further includes a specifying unit (touch recognition unit 16) that specifies the object in contact with the touch panel as either a finger or a passive pen in the above aspect 1 or 2. The calculating unit, when calculating the sum, adds the respective capacitances in the predetermined range different according to the specifying result by the specifying unit.

  According to the above configuration, the finger and the passive pen are in a floating state by differentiating the range in which the capacitance signals are combined between a finger having a wide touch range to the touch panel and a narrow passive pen, and the passive pen and the floating state. It is possible to accurately discriminate from any other object.

  In the detection circuit according to aspect 4 of the present invention, in the aspect 3, when the calculation unit specifies that the object in contact with the touch panel is the finger, a range corresponding to the finger on the sense line. The above sum is calculated by summing the capacitance signals of the capacitances.

  According to the above configuration, the sum of the higher capacity signals within the range corresponding to the finger is added to calculate the sum, so it is possible to accurately determine whether the object touching the touch panel is a finger or a floating object Can do.

  In the detection circuit according to aspect 5 of the present invention, in the aspect 4, when the calculation unit specifies that the object in contact with the touch panel is the passive pen, all capacitances on the sense line It is characterized in that the sum is calculated by adding together the capacitance signals.

  According to the above configuration, it is possible to avoid erroneously detecting a passive pen contact that generates a small capacitance signal in a narrow range as a contact of an object in a floating state.

  A touch sensor system according to an aspect 6 of the present invention includes a mutual capacitive touch panel and the detection circuit according to any one of claims 1 to 5.

  According to said structure, the touch sensor system which can avoid the misdetection of the object of the floating state in a touch panel, maintaining the advantage of a mutual capacitance system is realizable.

  The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention. Furthermore, a new technical feature can be formed by combining the technical means disclosed in each embodiment.

DESCRIPTION OF SYMBOLS 1 Touch sensor system 2 Host apparatus 5 Touch panel 10 Detection circuit 11 Driver 12 Sense amplifier 13 Timing generator 14 AD converter 15 Capacity distribution calculation part 16 Touch recognition part 17 Sum total value calculation part 18 False touch suppression part

Claims (6)

A calculation unit that calculates the sum of capacitance signals of each capacitance within a predetermined range read from the mutual capacitance type touch panel;
A determination unit configured to determine whether an object touching the touch panel is a ground state object or a floating state object based on a comparison result between the sum and a predetermined threshold value; Detection circuit.   The detection circuit according to claim 1, wherein the calculation unit calculates a sum of a predetermined number of capacitance signals in the extending direction of the sense line of the touch panel. Further comprising a specifying unit for specifying the object in contact with the touch panel as either a finger or a passive pen;
3. The detection according to claim 1, wherein when calculating the sum, the calculation unit adds the capacitances in the predetermined range that differ according to a specification result by the specification unit. circuit.   When the object that has touched the touch panel is identified as the finger, the calculation unit adds the capacitance signals of the capacitance within the range corresponding to the finger on the sense line, thereby calculating the sum. The detection circuit according to claim 3, wherein:   When the calculation unit determines that the object in contact with the touch panel is the passive pen, the calculation unit calculates the sum by adding the capacitance signals of all the capacitances on the sense line. The detection circuit according to claim 3. A touch sensor system comprising: a mutual capacitive touch panel; and the detection circuit according to claim 1.

Images