JP4622631B2 - Contact position coordinate detection method and apparatus - Google Patents

Description

  The present invention relates to a contact position coordinate detection method and apparatus capable of accurately detecting a contact position when, for example, a fingertip or the like is contacted on a touch panel having a conductive layer.

In recent years, a user interface using a touch panel has attracted attention. As user interfaces using such a touch panel, various types of user interfaces have been developed in the past, and it is necessary to accurately detect the coordinates of the position on the touch panel touched by the user.
FIG. 5 is a circuit diagram showing a configuration of a conventional contact position coordinate detection apparatus that detects coordinates of a contact position when a contact is made with a fingertip or the like on the touch panel by a capacitance detection method. The touch position coordinate detection apparatus includes a touch panel 101 including a detection circuit that detects a current flowing through a capacitance C of a human body when touching an insulating layer on the surface of the touch panel having a resistive film, and the detected current value. A calculation circuit for calculating the coordinates of the touch position on the touch panel.
6A and 6B are structural views showing the configuration of the touch panel 101, where FIG. 6A is a plan view of the touch panel 101, and FIG. 6B is a cross-sectional structural view showing an AA ′ cross section in FIG. is there. As shown in FIGS. 6A and 6B, the touch panel 101 includes a conductive layer 202 provided on an insulating substrate 201, an insulating layer 204 provided on the conductive layer 202, and electrodes 102 at four corners of the conductive layer 202. , 103, 104, 105 are attached.

As shown in FIG. 5, the detection circuit includes a current detection resistor circuit 106, differential effective value detection circuits 107, 108, 109, and 110, and a reference signal source 121 that outputs an AC reference signal. The calculation circuit for coordinate calculation includes addition circuits 111, 113, 114, an X-axis coordinate calculation circuit 112, and a Y-axis coordinate calculation circuit 115.
The current detection resistor circuit 106 corresponds to the capacitance C of the human body touching the insulating layer on the surface of the touch panel and the impedance of the conductive layer 202 between the electrodes 102, 103, 104, 105 and the contact position on the touch panel surface. Current detecting resistor R for detecting currents flowing to the electrodes 102, 103, 104, and 105 of the touch panel 101, respectively. The current detection resistor R generates voltage drop amounts at both ends corresponding to the currents flowing to the electrodes 102, 103, 104, and 105, respectively.
The differential effective value detection circuit 107 amplifies and detects the difference in voltage drop output from both ends of the current detection resistor R according to the current flowing to the electrode 102 of the touch panel 101, and detects the effective value of the current. Is a circuit that outputs a DC voltage Va according to the above.
The differential effective value detection circuit 108 amplifies and detects the difference in voltage drop output from both ends of the current detection resistor R in accordance with the current flowing to the electrode 103 of the touch panel 101, and detects the effective value of the current. Is a circuit that outputs a DC voltage Vd in accordance with.
The differential effective value detection circuit 109 amplifies and detects the difference in voltage drop output from both ends of the current detection resistor R according to the current flowing to the electrode 104 of the touch panel 101, and detects the effective value of the current. Is a circuit that outputs a DC voltage Vc according to the above.
The differential effective value detection circuit 110 amplifies and detects the difference in voltage drop output from both ends of the current detection resistor R in accordance with the current flowing to the electrode 105 of the touch panel 101, and detects the effective value of the current. Is a circuit that outputs a DC voltage Vb in accordance with.
The reference signal source 121 supplies the AC reference signal to the electrodes 102, 103, 104, and 105 of the touch panel 101 through the current detection resistors R.

The adder circuit 111 of the calculation circuit for coordinate calculation is a circuit that adds the output of the differential effective value detection circuit 107 and the output of the differential effective value detection circuit 108. The addition circuit 113 is a circuit that adds the output of the differential effective value detection circuit 107, the output of the differential effective value detection circuit 108, the output of the differential effective value detection circuit 109, and the output of the differential effective value detection circuit 110. is there. The adder circuit 114 is a circuit that adds the output of the differential effective value detection circuit 108 and the output of the differential effective value detection circuit 109.
Based on the addition result of the addition circuit 111 and the addition result of the addition circuit 113, the X-axis coordinate calculation circuit 112 calculates a coordinate calculation in the X-axis direction of the position at which the touch on the touch panel 101 is made with a predetermined calculation formula “( This is a circuit that uses “Va + Vd) / (Va + Vb + Vc + Vd)”. The Y-axis coordinate calculation circuit 115 calculates the coordinate in the Y-axis direction of the position where the touch is made on the touch panel 101 based on the addition result of the addition circuit 113 and the addition result of the addition circuit 114, according to a predetermined calculation formula “( Vc + Vd) / (Va + Vb + Vc + Vd) ".

Next, the operation will be described.
In this contact position coordinate detection apparatus, an AC reference signal is supplied from the reference signal source 121 to the electrodes 102, 103, 104, and 105 attached to the four corners, and the electrodes 102, 103, 104, and 105 provide an insulating layer on the touch panel surface. An alternating current flows through the capacitance C of the human body through the fingertip touched by the touch panel 101, and the path 102, 103, 104, 105 of the touch panel 101 → the human body → the reference signal source 121 of the detection circuit → the touch panel 101. A current loop is formed. At this time, the AC current flowing from the electrodes 102, 103, 104, and 105 through the capacitance C of the human body is biased according to the position where the insulating layer on the touch panel surface is contacted. From the bias of the alternating current, the coordinate of the position where the touch on the surface of the touch panel is contacted by the coordinate calculation arithmetic circuit is obtained by the predetermined arithmetic expression. When no contact is made with the insulating layer on the touch panel surface, the current loop is not formed, and the alternating current does not flow. However, since the alternating current to be detected is a minute current of about several μamperes, the amplification degree of the amplification circuit used in the differential effective value detection circuits 107, 108, 109, 110 is converted into a voltage amplification degree. A value of about 70 dB to 85 dB is required.
As a device for detecting a position where contact is made on such a touch panel, there is a coordinate detection device that detects a position where a touch panel having a resistive film is contacted using a pulse signal (Patent Document 1).
JP 2004-246657 A

A contact position coordinate detection apparatus according to the present invention is configured to detect a touch panel output signal output from a plurality of electrodes provided at predetermined positions of an insulated conductive layer constituting a touch panel by a detection circuit including an error amplifier and an amplitude detection circuit. amplification was detected, on the basis of the touch panel output signal the detected, in the contact position coordinate detecting device for detecting the position coordinates when the contact on the touch panel is performed, constituting the detection circuit by a single detector And an initial offset error detection means for detecting an initial offset error in the detection circuit for detecting the touch panel and the touch panel output signal when the touch panel is not touched, and the initial offset error detection means. An initial offset error holding means for holding an initial offset error; Holding said detection circuit for detecting a touch panel output signal, temperature drift offset error caused by the temperature drift of the initial offset error detecting means and said initial offset error holding unit, and detecting by means of inputting the same signal to the error amplifier, and Cyclic means for performing cyclic detection of touch panel output signals output from the plurality of electrodes using the detection circuit, and the touch panel output signal detected cyclically by the cyclic means for holding the initial offset error Compensation means for offset compensation based on the initial offset error held by the means and the temperature drift offset error held by the cyclic means, and the touch panel based on the touch panel output signal offset-compensated by the compensation means Contact was made up Characterized by comprising a calculating means for calculating a Kino the position coordinates.

  The present invention has been made in view of such circumstances, and avoids a decrease in contact position detection accuracy when contact is made on the touch panel, and can detect the contact position with high accuracy. It is an object to provide a method and apparatus.

In order to achieve the above object, a contact position coordinate detection method according to the present invention includes a touch panel output signal output from a plurality of electrodes provided at predetermined positions of an insulated conductive layer constituting a touch panel, an error amplifier and an amplitude. In a contact position coordinate detection method that amplifies and detects by a detection circuit including a detection circuit and detects a position coordinate when contact is made on the touch panel based on the detected touch panel output signal, the detection circuit is simply An initial offset error detection unit configured to detect an initial offset error in the detection circuit configured to detect an output signal of the touch panel and the touch panel when the touch panel is not in contact with the detection circuit. Procedure and the initial offset detected in the initial offset error detection procedure. An initial offset error holding procedure to hold the door error by the initial offset error holding means, said detection circuit for detecting the touch panel output signal, the temperature drift offset due to temperature drift of the initial offset error detecting means and said initial offset error holding means Cyclic means performs detection and holding of an error by inputting the same signal to the error amplifier and cyclic detection of a touch panel output signal output from the plurality of electrodes using the detection circuit, and the detection The touch panel output signal is compensated by the compensation means based on the initial offset error held by the initial offset error holding procedure and the held temperature drift offset error, and the offset compensated by the compensation procedure Based on touch panel output signal Characterized in that an arithmetic procedure for calculating the position coordinates when the contact on the touch panel is performed by the operation means.

  The contact position coordinate detection apparatus according to the present invention includes a detection circuit that amplifies a touch panel output signal by a single detection circuit, and amplifies the touch panel and the touch panel output signal when no touch is made on the touch panel. An initial offset error detecting means for detecting an initial offset error in the detection circuit; an initial offset error holding means for holding an initial offset error detected by the initial offset error detecting means; and the detection circuit for amplifying the touch panel output signal. Cyclic means for cyclically detecting and amplifying the temperature drift offset error accompanying the temperature drift of the processing circuit including and detecting and amplifying the touch panel output signal output from the plurality of electrodes using the detection circuit; Cyclically detected by cyclic means Compensating means for offset compensation based on the initial offset error held by the initial offset error holding means and the temperature drift offset error held cyclically by the cyclic means, the width of the touch panel output signal, And calculating means for calculating position coordinates when contact is made on the touch panel based on the touch panel output signal compensated for offset by the compensating means.

According to the present invention, a detection circuit including an error amplifier and an amplitude detection circuit that amplifies and detects a touch panel output signal is configured by a single detection circuit, and the stored initial offset error signal and temperature drift offset error signal are also included. In addition, since offset compensation is performed on the touch panel output signal output from each electrode of the touch panel, an initial offset error caused by variations in electrical characteristics and adjustment between the touch panel and the detection circuit is given to the touch panel output signal. Derived from errors occurring in the calculation results of position coordinates derived from adverse effects, and the detection circuit, initial offset error detection means, initial offset error holding means, and cyclic means itself temperature drift offset error generated due to temperature drift A contact has been made on the touch panel The effect of providing a contact position coordinate detection method and apparatus capable of effectively reducing errors occurring in the calculation results of the position coordinates, avoiding a decrease in contact position detection accuracy on the touch panel, and detecting the contact position with high accuracy. is there.

In addition, since the detection circuit including the error amplifier and the amplitude detection circuit that amplifies and detects the touch panel output signal output from each electrode of the touch panel is configured by a single detection circuit, the touch panel output signal is detected between channels. It is no longer necessary to maintain equality of circuit characteristics, and it is possible to effectively reduce errors that occur in the calculation results of position coordinates when touching on the touch panel due to variations in circuit characteristics between detection channels. There is an effect that it is possible to provide a contact position coordinate detection method and apparatus capable of avoiding a decrease in detection accuracy of the contact position on the touch panel and detecting the contact position with high accuracy.

  A detection circuit that amplifies a touch panel output signal for the purpose of providing a contact position coordinate detection method capable of detecting a contact position with high accuracy while avoiding a decrease in detection accuracy of a contact position when contact is made on the touch panel. An initial offset error is detected in the touch panel and the detection circuit that amplifies the touch panel output signal when the touch panel is not in contact with the touch panel when the touch panel is not touched, and the detected initial offset error is retained. Detecting and holding a temperature drift offset error accompanying a temperature drift of a processing circuit including the detection circuit for amplifying the touch panel output signal, and detecting and amplifying the touch panel output signal output from the plurality of electrodes. The touch panel output signal detected and amplified is cyclically performed using Offset compensation is performed based on the retained initial offset error and the retained temperature drift offset error, and a position coordinate when contact is made on the touch panel is calculated based on the compensated touch panel output signal. That was realized.

  In addition, the detection of amplifying the touch panel output signal is aimed at providing a contact position coordinate detection device capable of detecting the contact position with high accuracy while avoiding a decrease in the detection accuracy of the contact position when contact is made on the touch panel. An initial offset error detecting means detects an initial offset error in the detection circuit that amplifies the touch panel and the touch panel output signal when the touch panel is not in contact with the touch panel when the circuit is configured by a single detection circuit; Detecting and holding a temperature drift offset error accompanying a temperature drift of a processing circuit including the detection circuit that holds the initial offset error detected by the initial offset error detection means by an initial offset error holding means and amplifies the touch panel output signal; And touch output from the plurality of electrodes The output signal is cyclically detected by the cyclic means using the detection circuit, and the touch panel output signal cyclically detected and amplified by the cyclic means is held by the initial offset error holding means. On the touch panel based on the touch panel output signal compensated for offset by the compensation means based on the initial offset error and the temperature drift offset error held cyclically by the cyclic means, and offset compensated by the compensation means. This was realized by calculating the position coordinates when contact was made with the calculation means.

FIG. 1 is a circuit diagram showing the configuration of the contact position coordinate detection apparatus according to the first embodiment. This touch position coordinate detection device includes a touch panel 1 including a detection circuit 51 that detects a current flowing through a capacitance C of a human body when the touch panel surface having a resistance film is touched with, for example, a fingertip. The offset compensation circuit 52 for automatically correcting the initial offset and temperature drift, which are the features of the conventional contact position coordinate detection device, and which is a problem in the conventional contact position coordinate detection device, and for avoiding the occurrence of an offset between channels. And a coordinate calculation calculation circuit 53 for calculating the coordinates of the position when the touch panel is touched from the detected current value.
FIG. 2 is a structural diagram showing the configuration of the touch panel 1 in the contact position coordinate detection apparatus of the first embodiment. FIG. 2 (a) is a plan view of the touch panel 1, and FIG. 2 (b) is a diagram in FIG. It is a sectional structure figure showing an AA 'section. As shown in FIGS. 2A and 2B, the touch panel 1 includes a conductive layer 12 on an insulating substrate 11, an insulating layer 14 on the conductive layer 12, and electrodes 2 at the four corners of the conductive layer 12. , 3, 4 and 5 are attached.

  As shown in FIG. 1, the detection circuit 51 includes a current detection resistor circuit 6 and a touch panel corresponding to a minute alternating current that flows to the electrodes 2, 3, 4, and 5 of the touch panel 1 when touching the touch panel 1. A cyclic switch circuit 8 that switches an output signal and an AC reference signal output from the reference signal source 121, an error amplifier 9 that amplifies the touch panel output signal, and an amplitude detection circuit 10 that detects the output of the error amplifier 9. I have.

  The current detection resistor circuit 6 includes the capacitance C of the human body when touching the insulating layer 14 on the surface of the touch panel 1 and the conductive layer between the electrodes 2, 3, 4, 5 and the contact position on the touch panel surface. 12 has a current detection resistor R for detecting currents flowing to the electrodes 2, 3, 4 and 5 of the touch panel 1 in accordance with the impedance of the touch panel 1. The reference signal source 121 supplies the AC reference signal to the electrodes 102, 103, 104, and 105 of the touch panel 101 via the current detection resistors R. For this reason, the current detection resistor R is connected to the electrodes 2 and 3. , 4 and 5, a voltage drop amount corresponding to the current flowing to each of them is generated at both ends as a touch panel output signal.

In the cyclic switch circuit 8, the conduction state and non-conduction between the fixed contact terminals K1, K2, K3, K4, and K5 and the movable contact terminal K0 based on a control signal output from a sequential control circuit 29 described later. The state is switched. An AC reference signal from the reference signal source 121 is supplied to the fixed contact terminal K 1 of the cyclic switch circuit 8. In addition, a touch panel output signal Va corresponding to the current flowing to the electrode 2 of the touch panel 1 is supplied to the fixed contact terminal K2. In addition, a touch panel output signal Vb corresponding to the current flowing to the electrode 3 of the touch panel 1 is supplied to the fixed contact terminal K3. The fixed contact terminal K4 is supplied with a touch panel output signal Vc corresponding to the current flowing to the electrode 4 of the touch panel 1. The fixed contact terminal K5 is supplied with a touch panel output signal Vd corresponding to the current flowing to the electrode 5 of the touch panel 1.
The error amplifier 9 includes an analog arithmetic circuit 9A and an analog amplifier 9B, and when the touch panel 1 is touched with an offset error signal used to compensate for various errors that cause a decrease in detection accuracy of the position touched with the touch panel 1. Is a circuit that amplifies and outputs a touch panel output signal corresponding to a minute alternating current flowing through each of the electrodes 2, 3, 4 and 5.

  The analog arithmetic circuit 9A is an electrode when the touch panel 1 is touched based on a voltage drop amount of the current detection resistor R during a period in which the movable contact terminal K0 of the cyclic switch circuit 8 is in conduction with the fixed contact terminal K2. 2 touch panel output signals are analog-calculated and output to the analog amplifier 9B. Further, the touch panel output signal of the electrode 3 when touching the touch panel 1 based on the voltage drop amount of the current detection resistor R during the period in which the movable contact terminal K0 of the cyclic switch circuit 8 is in conduction with the fixed contact terminal K3. Is calculated and output to the analog amplifier 9B. Further, the touch panel output signal of the electrode 4 when the touch panel 1 is touched based on the voltage drop amount of the current detection resistor R during the period in which the movable contact terminal K0 of the cyclic switch circuit 8 is in conduction with the fixed contact terminal K4. Is calculated and output to the analog amplifier 9B. Further, the touch panel output signal of the electrode 5 when touching the touch panel 1 based on the voltage drop amount of the current detection resistor R during the period in which the movable contact terminal K0 of the cyclic switch circuit 8 is in conduction with the fixed contact terminal K5. Is calculated and output to the analog amplifier 9B.

Further, the analog arithmetic circuit 9A does not touch the touch panel 1 based on the voltage drop amount of the current detection resistor R during the period in which the movable contact terminal K0 of the cyclic switch circuit 8 is in conduction with the fixed contact terminal K2. The offset error signal for the current electrode 2 is analog-calculated and output to the analog amplifier 9B. Further, the offset of the electrode 3 when the touch panel 1 is not touched based on the voltage drop amount of the current detection resistor R during the period in which the movable contact terminal K0 of the cyclic switch circuit 8 is in conduction with the fixed contact terminal K3. The error signal is analog-calculated and output to the analog amplifier 9B. Further, the offset of the electrode 4 when the touch panel 1 is not touched based on the voltage drop amount of the current detection resistor R during the period in which the movable contact terminal K0 of the cyclic switch circuit 8 is in conduction with the fixed contact terminal K4. The error signal is analog-calculated and output to the analog amplifier 9B. Further, the offset of the electrode 5 when the touch panel 1 is not touched based on the voltage drop amount of the current detection resistor R during the period in which the movable contact terminal K0 of the cyclic switch circuit 8 is in conduction with the fixed contact terminal K5. The error signal is analog-calculated and output to the analog amplifier 9B.
The analog amplifier 9B amplifies and outputs the output of the analog arithmetic circuit 9A.

  Further, during the period in which the movable contact terminal K0 of the cyclic switch circuit 8 is in conduction with the fixed contact terminal K1, only the AC reference signal is input to the analog arithmetic circuit 9A. Is an output accompanying the temperature drift in the analog arithmetic circuit 9A and analog amplifier 9B, which is output from the error amplifier 9 as a temperature drift offset error signal accompanying the temperature drift. It is used for offset compensation as a temperature drift offset error signal for compensating for the accompanying offset. The temperature drift offset error signal includes an offset including a displacement due to a stray, an error of the error amplifier 9 itself, an error of the amplitude detection circuit 10, an error of the cyclic switch circuit 31, sample hold circuits 32 a, 32 b, 32 c, This is mainly due to temperature drift including errors in 32d and 32e.

  The amplitude detection circuit 10 is a circuit that detects the DC level of the touch panel output signal, the offset error signal, and the temperature drift offset error signal output from the error amplifier 9.

  The offset compensation circuit 52 switches the output of the offset compensation / noise filter circuit 20, the A / D / D / A converters 21, 23, 25, 27, the sequential control circuit 29, and the offset compensation / noise filter circuit 20. A sample-and-hold unit 32 having a cyclic switch circuit 31, sample-and-hold circuits 32a, 32b, 32c, 32d, and 32e, and capacitors 41, 42, 43, and 43e of the sample-and-hold circuits 32a, 32b, 32c, 32d, and 32e, 44, 45.

  The A / D / D / A converters 21, 23, 25, and 27 are provided with an A / D conversion function, a D / A conversion function, and a re-correction operation signal that triggers a re-correction operation when the power is turned on. Output from the amplitude detection circuit 10 converted to digital data by the A / D conversion function (the electrodes 2, 3, 4, and 5 output from the error amplifier 9 when not touching the touch panel 1) And a latch circuit for holding a digital value of the offset error signal.

  The offset compensation / noise filter circuit 20 is a circuit that performs offset compensation including an adder / subtracter and a noise filter. In the offset compensation / noise filter circuit 20, the offset error signal held in the latch circuits of the A / D / D / A converters 21, 23, 25, 27 and the capacitor 45 of the sample hold circuit 32e are held. Based on the detected temperature drift offset error signal, the amplitude detection circuit 10 performs offset compensation on the touch panel output signal detected and output as a DC level.

The sequential control circuit 29 brings the movable contact terminal C0 and the fixed contact terminal C1 of the cyclic switch circuit 8 into a conductive state at a timing when a recorrection operation signal serving as a trigger for power-on and recorrection is given. Thereafter, a control signal for causing the cyclic switch circuit 8 to perform one cyclic operation is output. At this time, a control signal for holding the offset error signal output from the amplitude detection circuit 10 in the latch circuits of the A / D / D / A converters 21, 23, 25, 27 is output. In addition, the touch panel output signal held in the sample hold circuits 32a, 32b, 32c, and 32d is reset to an initial value, and the temperature drift offset error output via the fixed contact terminal C1 of the cyclic switch circuit 31 is reset. A control signal for holding the signal in the capacitor 45 of the sample and hold circuit 32e is output to the sample and hold unit 32.
After the power-on and re-correction operation signal that is a trigger for the re-correction operation is given, the cyclic switch circuit 8 and the cyclic switch circuit 31 are synchronized and the conductive state between the movable contact terminal and the fixed contact terminal is established. And a control signal for switching the non-conduction state.

  The cyclic switch circuit 31 is connected to the movable contact terminal C0 and the fixed contact on the basis of the control signal output from the sequential control circuit 29 after being supplied with a recorrection operation signal that triggers power-on and recorrection operation. The conduction state and non-conduction state between the terminals C1, C2, C3, C4, and C5 are switched, and the conduction state and the non-conduction state are switched in synchronization with the cyclic switch circuit 8. That is, in the period in which the movable contact terminal C0 and the fixed contact terminal C1 of the cyclic switch circuit 31 are switched to the conductive state, the movable contact terminal K0 and the fixed contact terminal K1 are also in the conductive state in the cyclic switch circuit 8. It has been switched. Further, during the period in which the movable contact terminal C0 and the fixed contact terminal C2 of the cyclic switch circuit 31 are switched to the conductive state, the movable contact terminal K0 and the fixed contact terminal K2 are also conductive in the cyclic switch circuit 8. Similarly, during the period in which the movable contact terminal C0 and the fixed contact terminal C3 are switched to the conductive state, the movable contact terminal K0 and the fixed contact terminal K3 are also in the conductive state in the cyclic switch circuit 8. In the period in which the movable contact terminal C0 and the fixed contact terminal C4 are switched to the conductive state, the movable contact terminal K0 and the fixed contact terminal K4 are also in the conductive state in the cyclic switch circuit 8, and the movable contact terminal C0 and In the period in which the fixed contact terminal C5 is switched to the conductive state, the movable contact terminal K0 and the fixed contact terminal K are also used in the cyclic switch circuit 8. Door is switched to a conducting state.

As a result, the initial value of the temperature drift offset error signal at this time is first held in the sample and hold circuit 32e when the power is turned on and during the period when the recorrection operation signal serving as a trigger for the recorrection operation is given. The error signal is held in the latch circuits of the A / D / D / A converters 21, 23, 25, 27.
That is, during the period in which the movable contact terminal C0 and the fixed contact terminal C1 of the cyclic switch circuit 31 are switched to the conductive state, the movable contact terminal K0 and the fixed contact terminal K1 are also conductive in the cyclic switch circuit 8. The temperature drift offset error signal that has been switched and compensates for the offset due to the temperature drift is held in the capacitor 45 of the sample hold circuit 32e. This temperature drift offset error signal is generated every time the cyclic switch circuits 8 and 31 perform one cyclic operation when the power is turned on and after a recorrection operation signal serving as a trigger for the recorrection operation is given. Updated to the sample hold circuit 32e.

  As a result, when the touch panel 1 is touched after turning on the power and after a period when the re-correction operation signal serving as a trigger for the re-correction operation has elapsed, the touch panel output signal for calculating the position coordinates is offset-compensated and the sample hold It is held in the capacitors 41, 42, 43, 44 of the unit 32, and a position detection output in the X coordinate direction and the Y coordinate direction is obtained by the coordinate calculation arithmetic circuit 53. The adder circuit 33 of the calculation circuit 53 for coordinate calculation is a circuit that adds the touch panel output signals held by the sample hold circuits 32a, 32b, 32c, and 32d. The adder circuit 34 is a circuit that adds the touch panel output signal held by the sample hold circuit 32a and the touch panel output signal held by the sample hold circuit 32c. The adder circuit 36 is a circuit that adds the touch panel output signal held by the sample hold circuit 32c and the touch panel output signal held by the sample hold circuit 32d. The X-axis coordinate calculation circuit 35 touches the touch panel 1 based on the touch panel output signals Va, Vb, Vc, and Vd that are offset compensated based on the addition result of the addition circuit 34 and the addition result of the addition circuit 33. In this circuit, the coordinates of the contact position in the X-axis direction are calculated using a predetermined arithmetic expression “(Va + Vd) / (Va + Vb + Vc + Vd)”. Based on the addition result of the addition circuit 33 and the addition result of the addition circuit 36, the Y-axis coordinate calculation circuit 37 calculates the coordinate in the Y-axis direction of the contact position when touching the touch panel 1 according to a predetermined equation “(Vc + Vd). ) / (Va + Vb + Vc + Vd) ".

Next, the operation will be described.
FIG. 3 is a timing chart showing the operation of each part of the contact position coordinate detection apparatus according to the first embodiment. FIG. 4 is a flowchart showing a contact position coordinate detection method applied to the contact position coordinate detection apparatus of the first embodiment.
The operation of the contact position coordinate detection method according to the first embodiment will be described below with reference to the block diagram of the contact position coordinate detection apparatus shown in FIG. 1, the timing chart of FIG. 3, and the flowchart of FIG. As shown in the flowchart of FIG. 4, when an initial reset pulse is generated when the power is turned on, an initial reset of each unit is performed for a reset period defined by the initial reset pulse (step S1, step S2). This reset period is a period in which the reset 2 signal shown in FIG. 3 (d) is output triggered by the reset 1 signal shown in FIG. 3 (b), or the CAL TM signal shown in FIG. 3 (m) is “High”. This is the period Tr in which the level is “. With this initial reset, the cyclic switch circuit 8 is initially set in a state where the fixed contact terminal K2 and the movable contact terminal K0 are conductive, and in the cyclic switch circuit 31, the fixed contact terminal C2 and the movable contact terminal C0 are conductive. Initially set to
When the reset period elapses, first, an initial value of a temperature drift offset error signal corresponding to the temperature at the time of activation of the contact position coordinate detection device is detected (step S3). Then, the detected initial value of the temperature drift offset error signal is held in the capacitor 45 of the sample hold circuit 32e (step S4). Next, an offset error signal corresponding to the electrodes 2, 3, 4 and 5 of the touch panel 1 is detected (step S5), and the respective latches of the corresponding A / D / D / A converters 21, 23, 25 and 27 are detected. It holds in the circuit (step S6). The processes of step S3, step S4, step S5, and step S6 are performed during a period To shown in the timing chart of FIG. For this reason, the sequential control circuit 29 outputs a control signal for performing the processing of step S3 and step S4 in the period To at the timing shown in FIG. 3 (j), detects the initial value of the temperature drift offset error signal, The detected initial value of the temperature drift offset error signal is held in the capacitor 45 of the sample hold circuit 32e. Further, at the timing shown in FIGS. 3 (k) and 3 (l), a control signal for performing the processing of step S5 and step S6 in the period To is output, an offset error signal is detected, and the detected offset error signal is converted to A / The D / D / A converters 21, 23, 25 and 27 hold the latch circuits.

Subsequently, the sequential control circuit 29 synchronizes the cyclic switch circuits 8 and 31 while updating the temperature drift offset error signal held in the capacitor 45 of the sample and hold circuit 32e unless a power-off or recorrection operation signal is detected. Thus, the touch panel output signal is detected by cyclically switching between the conductive state and the non-conductive state between the movable contact terminal and the fixed contact terminal (step S7, step S11, step S12, step S13, step S14).
When contact is made with respect to the touch panel 1 in this state, the touch panel output signals output from the electrodes 2, 3, 4 and 5 are cycled by the cyclic switch circuits 8 and 31 at the timing shown in FIG. (Step S7), and the offset error signal held in the latch circuits of the A / D / D / A converters 21, 23, 25, 27 and the temperature drift offset error signal held in the capacitor 45 are used. Then, the offset compensation / noise filter circuit 20 performs offset compensation on each detected touch panel output signal (step S8). In this case, the offset compensation using the offset error signal held in each latch circuit is, for example, if the value of the held offset error signal is + Δ, -Δ is added as a correction amount to the touch panel output signal, and If the value of the offset error signal is −Δ, offset compensation is performed with a correction amount of an opposite sign, such as adding + Δ as a correction amount to the touch panel output. Further, in this case, the offset compensation using the temperature drift offset error signal, for example, obtains the difference between the value of the temperature drift offset error signal held last time and the value of the temperature drift offset error signal held this time. If + Δ, -Δ is added as a correction amount to the touch panel output, and if the difference amount is -Δ, + Δ is added as a correction amount to the touch panel output. Compensate.
The offset-compensated touch panel output signals are held by the corresponding sample-and-hold circuit capacitors in the next cyclic cycle of the cyclic switch circuit 31 (step S9). The coordinate calculation arithmetic circuit 53 uses the touch panel output signals held in the respective sample and hold circuits to determine the coordinates in the X-axis direction of the contact position when touching the touch panel 1 as a predetermined arithmetic expression “(Va + Vd) / ( (Va + Vb + Vc + Vd) ”and the coordinates in the Y-axis direction are calculated using a predetermined arithmetic expression“ (Vc + Vd) / (Va + Vb + Vc + Vd) ”(step S10).

  As described above, according to the first embodiment, the temperature drift offset error signal that is constantly updated cyclically, and the offset error signal that is held only when the power is turned on or when the recorrection operation signal is given. Originally, in order to perform offset compensation for the touch panel output signals output from the electrodes 2, 3, 4 and 5 of the touch panel 1, the electrical characteristics and adjustment variations of the touch panel 1, the error amplifier 9, and the amplitude detection circuit 10 are varied. An error that occurs in the calculation result of the calculation circuit 53 for coordinate calculation derived from an adverse effect of the initial offset on the touch panel output signal due to the initial offset, an error of the error amplifier 9 itself that occurs mainly due to temperature drift, and amplitude detection The offset including the error of the circuit 10, the error of the cyclic switch circuit 31, the sample and hold circuits 32a, 32b, 32c, 2d, there is an effect capable of providing a contact position coordinate detection method and apparatus can effectively reduce errors occurring in the calculation results of the coordinate calculation operation circuit 53 that derives from the error in 32e.

  Further, since the touch panel output signal output from each electrode 2, 3, 4, 5 of the touch panel 1 is cyclically switched by the cyclic switch circuit 8 and input, the error amplifier 9 and the amplitude detection circuit 10 are Since only one system is required, the error amplifier 9 and the amplitude detection circuit 10 of this one system can be used in common for the touch panel output signals output from the electrodes 2, 3, 4, and 5. Compared to the conventional method in which a detection circuit is provided for each touch panel output signal output from each electrode 2, 3, 4 and 5, it is no longer necessary to maintain equality of circuit characteristics between channels for detecting each touch panel output signal. Detection of contact position coordinates that can effectively reduce an error that the calculation result of the calculation circuit 53 for coordinate calculation is included due to variations in circuit characteristics between detection channels There is an effect capable of providing a legal and devices.

It is a circuit diagram which shows the structure of the contact position coordinate detection apparatus of Example 1 of this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is a structural diagram which shows the structure of the touch panel 1 in the contact position coordinate detection apparatus of Example 1 of this invention. It is a timing chart which shows operation | movement of each part of the contact position coordinate detection apparatus of Example 1 of this invention. It is a flowchart which shows the contact position coordinate detection method applied to the contact position coordinate detection apparatus of Example 1 of this invention. It is a circuit diagram which shows the structure of the conventional contact position coordinate detection apparatus. It is structural drawing which shows the structure of the touch panel in the conventional contact position coordinate detection apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Touch panel, 2, 3, 4, 5 ... Electrode, 8 ... Cyclic switch circuit (initial offset error detection means, cyclic means), 9 ... Error amplifier, 10 ... Amplitude detection circuit,
20... Offset compensation / noise filter circuit (offset cancellation circuit) 21, 23, 25, 27... A / D / D / A converter (initial offset error holding means) 29 .. Sequential control circuit (initial offset error) Detection means), 31... Cyclic switch circuit (cyclic means), 32 e... Sample hold circuit (cyclic means), 51... Detection circuit, 52... Offset compensation circuit (compensation means), 53. Calculation calculation circuit (calculation means).

Claims (8)

A touch panel output signal output from a plurality of electrodes provided at a predetermined position of the insulated conductive layer constituting the touch panel amplifies detected by the detection circuit includes an error amplifier and an amplitude detection circuit, the detected touch panel output signal In the contact position coordinate detection method for detecting the position coordinates when contact is made on the touch panel based on
The detection circuit is constituted by a single detection circuit,
An initial offset error detection procedure for detecting an initial offset error in the detection circuit for detecting the touch panel and the touch panel output signal when the touch panel is not touched by an initial offset error detection means ;
An initial offset error holding procedure for holding an initial offset error detected by the initial offset error detection procedure by an initial offset error holding means ;
Detecting and holding the temperature drift offset error associated with the temperature drift of the detection circuit for detecting the touch panel output signal, the initial offset error detecting means and the initial offset error holding means by inputting the same signal to the error amplifier ; And cyclic detection of the touch panel output signal output from the plurality of electrodes by the cyclic means using the detection circuit, and the initial offset error in which the detected touch panel output signal is held in the initial offset error holding procedure And a compensation procedure for offset compensation by a compensation means based on the held temperature drift offset error,
An arithmetic procedure for calculating the position coordinates when the touch is made on the touch panel based on the touch panel output signal offset-compensated in the compensation procedure,
A contact position coordinate detection method comprising:   The compensation procedure is the same as the initial offset error held by the initial offset error holding procedure and the cycle in which the touch panel output signal was detected and amplified by cyclically detecting and amplifying the touch panel output signal using the detection circuit. The contact position coordinate detection method according to claim 1, wherein offset compensation is performed based on the temperature drift offset error held in the period. In the compensation procedure, the touch panel output signal detected using the detection circuit is a common offset cancel based on the initial offset error held in the initial offset error holding procedure and the held temperature drift offset error. 2. The contact position coordinate detection method according to claim 1, wherein offset compensation is performed by a circuit. The cyclic means uses the detection circuit to detect and hold the temperature drift offset error accompanying the temperature drift of the detection circuit, the initial offset error detection means, the initial offset error holding means, and the cyclic means itself. The contact position coordinate detection method according to claim 1. A touch panel output signal output from a plurality of electrodes provided at a predetermined position of the insulated conductive layer constituting the touch panel amplifies detected by the detection circuit includes an error amplifier and an amplitude detection circuit, the detected touch panel output signal Based on the above, in the contact position coordinate detection apparatus for detecting the position coordinates when contact is made on the touch panel,
The detection circuit is constituted by a single detection circuit,
An initial offset error detecting means for detecting an initial offset error in the detection circuit for detecting the touch panel and the touch panel output signal when the touch panel is not in contact; and
Initial offset error holding means for holding the initial offset error detected by the initial offset error detection means;
Detecting and holding the temperature drift offset error associated with the temperature drift of the detection circuit for detecting the touch panel output signal, the initial offset error detecting means and the initial offset error holding means by inputting the same signal to the error amplifier ; And cyclic means for performing cyclic detection of touch panel output signals output from the plurality of electrodes using the detection circuit,
The touch panel output signal detected cyclically by the cyclic means is based on the initial offset error held by the initial offset error holding means and the temperature drift offset error held cyclically by the cyclic means. Compensation means for offset compensation;
A computing means for computing the position coordinates when contact is made on the touch panel based on the touch panel output signal offset-compensated by the compensating means;
A contact position coordinate detection apparatus comprising: Said compensating means, said touch panel output signal detected cyclically using the detection circuit, wherein the initial offset error holding initial offset error held by means, same period as that detected the touch panel output signal 6. The contact position coordinate detection apparatus according to claim 5, wherein offset compensation is performed based on the temperature drift offset error held in step (a). The compensation means, based on the initial offset error held by the initial offset error holding means and the held temperature drift offset error, the touch panel output signal detected by the cyclic means using the detection circuit. 6. The contact position coordinate detection apparatus according to claim 5, wherein offset compensation is performed by a common offset cancel circuit. The cyclic means uses the detection circuit to detect and hold the temperature drift offset error accompanying the temperature drift of the detection circuit, the initial offset error detection means, the initial offset error holding means, and the cyclic means itself. The contact position coordinate detection apparatus according to claim 5.

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