JPH11143626A - Coordinate input device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect a precise input coordinate even if the S/N of a coordinate detection signal is low. SOLUTION: First and second switch means 34 and 35 scan first and second electrodes 31 and 32 without installing an indication means 40 on a coordinate input panel 33. X and Y signal amplification means 37 and 38 amplify X and Y signals and remove AC components. A coordinate operation means 42 sample- holds coordinate detection voltage and A/D convert it. An obtained digital value is stored in a storage means 41 as the digital data string of a noise component. At the time of inputting the coordinate, the digital data string when the indication means 41 exists is similarly obtained. The subtracter of the coordinate operation means 42 subtracts the digital data string of the noise component stored in the storage means 41. The digital data string of coordinate detection voltage which does not contain the noise component is obtained and the precise input coordinate is obtained based on the digital data string.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coordinate input device used for inputting characters, figures and the like to a personal computer, a word processor or the like.

[0002]

2. Description of the Related Art As means for inputting predetermined characters and figures into a personal computer, a word processor, and the like, a coordinate input device capable of inputting characters, figures, or commands by using a pen or a finger has been put into practical use.

As such a coordinate input device, there are tablets of resistance type, electrostatic induction type, electromagnetic induction type and the like.
Further, there is a display-integrated coordinate input device in which an electrode or a driving circuit of a liquid crystal display panel or the like is also used as an electrode or a driving circuit for inputting coordinates. In each of these coordinate input devices, the position on the panel actually pointed with a pen, a finger, or the like does not always match the coordinate detection result, and a coordinate shift occurs. Therefore, the coordinate detection result is corrected to match the actual designated position.

Japanese Patent Laid-Open Publication No. 3-134724 discloses a method of correcting variations in coordinate values due to variations in resistance values of resistors in the above-mentioned resistance-type tablet. As shown in FIG. 10, the coordinate input device disclosed in JP-A-3-134724 drives an X-side resistor 1 and a Y-side resistor 2 with a constant current, and applies a voltage between both ends of each of the resistors 1 and 2. The A / D converter 3 converts the potential difference into a digital value. In this case, the output value of the A / D converter 3 in the state where the switch S1 is turned on is set as the reference value Vr at the time of the maximum resistance and the control unit 4
The control unit 4 divides the output value Vs of the A / D converter 3 at the time of inputting the coordinates by the reference value Vr to obtain the input coordinate value (= 2
56 * Vs / Vr). Thus, the variation in the coordinate detection result due to the variation in the resistance values of the resistors 1 and 2 is corrected in a software manner.

Japanese Patent Application Laid-Open No. 61-265519 discloses a method for correcting a variation in coordinate values due to a variation in internal resistance in the above-mentioned electrostatic tablet using a resistive film. Japanese Patent Application Laid-Open No. 61-265519
As shown in FIG.
This is to correct a coordinate error based on the internal resistance of the analog switch arrays 5 to 8, and to measure a reference voltage value by passing a current through a resistive film as the touch panel 9 through the analog switch arrays 5 to 8 in advance. The data is converted into a digital value by the A / D converter 10. Then, a correction coefficient is calculated based on the digital conversion value. At the time of inputting the coordinates, the coordinates are obtained by a predetermined operation based on the digital conversion value from the A / D converter 10, and the coordinates are corrected by the previously obtained correction coefficient.

A method of correcting variations in coordinate values due to variations in the number of lines or lengths in the X direction or Y direction in the above-mentioned electrostatic induction type tablet is disclosed in Japanese Patent Application Laid-Open No. Sho 60/1985.
No. 5324. This Japanese Unexamined Patent Publication No.
In the pointing position detecting device disclosed in Japanese Patent No. 5324, FIG.
As shown in (1), intersections TCH between a plurality of lines in the X direction and a plurality of lines in the Y direction are arranged in a matrix on the pointing device PN. Then, the intersection TCH is sequentially switched and selected by the analog multiplexer 11, and a designated coordinate is detected by detecting a change in capacitance at the intersection TCH at the designated position as a movement of a resonance peak.
In that case, the electrode capacitance specific to each intersection TCH is:
Since there is variation depending on the number and length of each line, the resonance frequency shifts at the intersection TCH, and the detection sensitivity decreases. Therefore, an impedance correction circuit 12 composed of a group of correction elements C having an appropriate impedance according to each intersection TCH is provided, and the impedance is corrected by selecting the correction element C corresponding to the intersection TCH at the designated position. It is.

A method for correcting the variation in coordinate values in the electromagnetic induction type tablet is disclosed in
18025. This Japanese Unexamined Patent Publication No.
In the coordinate detecting device disclosed in Japanese Patent Publication No. 18025, as shown in FIG.
Exciter (cursor) 17 with tablet 16 arranged
The output is obtained from each of the conductors 15 and 16 corresponding to the position of the cursor 17 due to the electromagnetic coupling with. The designated coordinates are obtained by calculation from these two output values. In that case,
Since the output waveforms from the two conductors 15 and 16 are not ideal sine waves but have a distortion close to a triangular wave or trapezoidal wave, an error occurs in the detected coordinate values. Therefore, the error of the coordinate value due to the distortion of the output waveform is measured in advance and stored as correction data. Then, at the time of inputting the coordinates, the coordinate values are calculated by a predetermined calculation, and then the correction data corresponding to the calculated coordinate values is read to correct the calculated coordinate values.

A method for correcting variations in detected coordinate values due to the shape of end electrodes and propagation delays in the display-integrated coordinate input device is disclosed in Japanese Patent Application Laid-Open No. 5-324174.
No. 6,086,045. Japanese Patent Application Laid-Open No. 5-324174
As shown in FIG. 14, the display-integrated tablet device disclosed in Japanese Patent Application Laid-Open Publication No. H11-143556 combines electrodes X and Y of the display panel 21 and drive circuits 22 and 23 with electrodes for coordinate detection and a drive circuit. Then, a scanning signal is sequentially applied to the Y electrodes, and the designated coordinates are obtained by measuring the timing at which the induced voltage induced on the pen 27 by the electrostatic induction shows the maximum value. In this case, the detected coordinate value deviates from the actual position indicated by the pen 27 due to the shape of the end electrode and the propagation delay. Therefore, the display panel 21
The deviation of the detected coordinate value at each of the above positions is measured, and a correction coefficient and a correction equation are obtained. When the coordinates are input, the detected coordinate value is corrected by the correction processing circuit 28 using the correction coefficient and the correction formula.

[0009]

However, each of the above-mentioned conventional coordinate input devices has the following problems. That is, a method of dividing an output value Vs at the time of inputting coordinates by a coordinate input device by a reference value Vr at the time of maximum resistance in Japanese Patent Application Laid-Open No. 3-134724.
Japanese Patent Application Laid-Open No. 61-18025 discloses a method of correcting a calculated coordinate value when a coordinate is input by a coordinate detecting device using a correction coefficient obtained when the coordinate is not input. Both the method of correcting with the corrected data obtained and the method of correcting the detected coordinate value at the time of inputting the coordinates by the display-integrated tablet device with a correction coefficient and a correction formula prepared in advance in Japanese Patent Application Laid-Open No. Hei 5-324174. The value is calculated, and the calculated coordinate value is corrected.

For this purpose, it is assumed that the output of the detection signal is larger than the level of various distortions and noises so that a coordinate value can be calculated. Therefore, if the S / N ratio cannot be sufficiently obtained because the detection sensitivity is low and the detection signal itself or the amount of change in the detection signal is smaller than the waveform distortion or noise, a correct input coordinate value cannot be obtained. There's a problem.

In the case of Japanese Patent Application Laid-Open No. 60-5324, a method of selecting a correction element C corresponding to an intersection TCH of a designated position by a designated position detecting device and performing impedance correction, it is not possible to increase detection sensitivity. it can. However, an impedance correction circuit 1 composed of a group of correction elements C having an appropriate impedance according to each intersection TCH
2 must be provided, resulting in high cost and extra space.

SUMMARY OF THE INVENTION An object of the present invention is to provide an inexpensive coordinate input device capable of correctly detecting coordinates even when the level of the coordinate detection signal itself is lower than the noise level.

[0013]

Means for Solving the Problems To achieve the above object, the invention according to claim 1 is directed to a first electrode arranged parallel to each other and a first electrode arranged parallel to each other in a direction perpendicular to the first electrode. A coordinate input panel having two electrodes, and indicating means for indicating a position on the coordinate input panel, wherein the first and second electrodes output coordinate signals according to the position of the indicating means; A signal detecting means for detecting coordinate signals output from the first electrode and the second electrode; a signal converting means for converting the coordinate signals detected by the signal detecting means into a digital data sequence; Storage means for storing a digital data string from the signal conversion means when the indication means is not on the panel; and signal conversion when the indication means is present on the coordinate input panel. Means for correcting the digital data stream from the means using the digital data stream stored in the storage means to generate a corrected digital data stream; and the coordinates by the indicating means based on the corrected digital data stream. It is characterized by having a calculating means for calculating the designated coordinates on the input panel.

According to the above arrangement, by storing digital data strings of coordinate signals output from the first electrode and the second electrode without the indicating means on the coordinate input panel in the storage means, On the coordinate input panel, information of a noise component indicating a fixed pattern is held regardless of the presence or absence of the indicating means. Therefore, at the time of detecting the coordinates, for example, the correcting means reads the digital data strings of the coordinate signals output from the first electrode and the second electrode in a state where the indicating means is present on the coordinate input panel, by the correcting means. By subtracting the digital data sequence stored in the above, a digital data sequence of the coordinate signal whose noise component has been corrected can be obtained. Then, based on the corrected digital data string obtained in this way, even when the S / N ratio of the coordinate signal is poor, the designated coordinates on the coordinate input panel by the indicating means are correctly calculated by the calculating means.

According to a second aspect of the present invention, in the coordinate input device according to the first aspect of the present invention, the first and second electrodes are electrostatically coupled to the indicating means so as to correspond to the coupling capacity. The coordinate signal is output.

According to the above arrangement, the coordinates designated by the pointing means on the coordinate input panel are based on the coordinate signals output from the first and second electrodes and corresponding to the coupling capacity with the pointing means. Is calculated.

According to a third aspect of the present invention, in the coordinate input device according to the second aspect of the present invention, the signal detecting means includes a first signal detecting means for detecting a coordinate signal from the first electrode; The second detecting the coordinate signal from the second electrode
An AC applying unit configured to generate and output an AC signal, and a first electrode on the coordinate input panel is sequentially selected from one end and connected to the first signal detecting unit. On the other hand, a first switching means for switching and connecting a first electrode which is not selected to the AC applying means, and a second switching means for sequentially selecting a second electrode on the coordinate input panel from one end side and switching and connecting to the second signal detecting means. A second switching means for switching and connecting a second electrode which is not selected to the AC applying means; and a first / second switching means, a first / second switching means.
Control means for controlling the signal detection means, the signal conversion means, the storage means, the correction means, and the calculation means to detect the designated coordinates on the coordinate input panel by the designating means is provided.

According to the above configuration, according to the coupling capacity between the first and second electrodes and the indicating means generated on the first and second electrodes due to the AC voltage applied to the first and second electrodes by the AC applying means. The first and second electrodes are scanned by the first and second switching means, and the first and second signal detecting means detect the coordinate signals. Thus, based on the coordinate signal output from the first and second electrodes and corresponding to the coupling capacity with the indicating means, even if the S / N ratio of the coordinate signal is poor, the coordinate input panel is displayed on the coordinate input panel. The coordinates indicated by the indicating means are easily and correctly calculated.

According to a fourth aspect of the present invention, in the coordinate input device according to the first aspect of the present invention, the coordinate input panel has pixels arranged in a matrix, and the first and second electrodes are The pixel is connected to a display element constituting the pixel and also serves as an image display panel, and outputs an image signal and a display control signal during a display period in which an image is displayed on the pixel. A panel control means for outputting a detection control signal during a coordinate detection period for detecting the coordinates indicated by the indication means; and a display control signal connected to the first electrode and receiving a control signal from the panel control means. In the case of, the display element is driven based on the image signal from the panel control means, while in the case of the detection control signal, the coordinate signal from the first electrode is converted to the signal detection means. First driving means for sending the
While being connected to the second electrode, receiving a control signal from the panel control means, and in the case of the display control signal, driving the display element based on an image signal from the panel control means, In the case of a detection control signal, a second drive unit that sends a coordinate signal from the second electrode to the signal detection unit is provided, and the signal detection unit, the signal conversion unit, the storage unit, the correction unit, and the calculation unit are It is characterized in that it operates when it receives the detection control signal from the panel control means.

According to the above configuration, according to the display period and the coordinate detection period set by the panel control unit, the first and second drive units perform the display period based on the image signal from the panel control unit during the display period. Thus, the display element is driven to display an image on pixels arranged in a matrix. On the other hand, during the coordinate detection period, the first and second
The drive unit sends coordinate signals from the first and second electrodes to the signal detection unit. And, even if the S / N ratio of the coordinate signal is poor, the signal detection means, the signal conversion means, the storage means, the correction means and the calculation means
The coordinates indicated by the pointing means are correctly calculated.

According to a fifth aspect of the present invention, in the coordinate input device according to the fourth aspect of the present invention, the first and second electrodes are electrostatically coupled to the indicating means so as to correspond to the coupling capacity. The coordinate signal is output.

According to the above arrangement, the coordinates designated by the pointing means on the coordinate input panel are based on the coordinate signals output from the first and second electrodes and corresponding to the coupling capacity with the pointing means. Is calculated.

According to a sixth aspect of the present invention, in the coordinate input device according to the fifth aspect of the present invention, the coordinate input device further includes an AC applying means for generating and outputting an AC signal, and the signal detecting means includes the first electrode. And a second signal detecting means for detecting a coordinate signal from the second electrode. The first driving means receives the detection control signal. In this case, the first electrodes on the coordinate input panel are sequentially selected from one end and the first electrodes are selected.
The first electrode, which is not selected, is connected to the AC applying means while being switched to the signal detecting means, and the second driving means, when receiving the detection control signal, receives the coordinate input signal. The second electrode on the panel is sequentially selected from one end side and is connected to the second signal detecting means for switching, while the second electrode not selected is selectively connected to the AC applying means. .

According to the above configuration, during the coordinate detection period, the instruction generated on the first and second electrodes due to the AC voltage applied to the first and second electrodes by the AC applying means. The first and second electrodes are scanned by the first and second driving means for a coordinate signal corresponding to the coupling capacitance with the means,
It is detected by the first and second signal detection means. Thus, even if the S / N ratio of the coordinate signal is poor, based on the coordinate signal output from the first and second electrodes in accordance with the coupling capacitance with the indicating means, the coordinate input panel can be used. The coordinates indicated by the above-mentioned indicating means are easily and correctly calculated.

According to a seventh aspect of the present invention, in the coordinate input device of the fourth aspect, the panel control means is a system control means for controlling the entire system.

According to the above configuration, the configuration of the system equipped with the coordinate input device is simplified, and the cost is reduced.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.

<First Embodiment> FIG. 1 is a functional block diagram of a coordinate input device according to the present embodiment. The present coordinate input device includes a plurality of first electrodes 3 arranged in parallel with each other.
, And second coordinate electrodes 33 formed of second electrodes 32, 32,... Arranged orthogonal to the first electrode 31 and parallel to each other. Around the coordinate input panel 33, a first switching means 34 composed of a group of analog switches connected to each of the first electrodes 31, 31,... And a connection to each of the second electrodes 32, 32,. And a second switching unit 35 composed of a group of analog switches described above. Hereinafter, the arrangement direction of the first electrodes 31 (extending direction of the second electrodes 32) is referred to as an X direction, and the arrangement direction of the second electrodes 32 (extending direction of the first electrodes 31) is referred to as a Y direction. In response, the first electrode 3
The signal detected at 1 is called an X signal, and the signal detected at the second electrode 32 is called a Y signal.

The AC applying means 36 is connected to the first switching means 3
An AC signal is supplied to the first electrode 31 through the fourth electrode 4. Similarly, an AC signal is supplied to the second electrode 32 via the second switching means 35. Further, an AC signal is supplied to the X signal amplifier 37 and the Y signal amplifier 38. X signal amplification means 3
7 amplifies the X signal received from the first electrode 31 via the first switching means 34 and outputs it to the coordinate calculation means 42.
The Y signal amplifying means 38 is connected to the second
The Y signal received from the electrode 32 is amplified and output to the coordinate calculation means 42. The coordinate calculation means 42 is a part of the X signal amplifying means 3 when the instruction means 40 is present on the coordinate input panel 33.
The designated coordinates on the coordinate input panel 33 by the indicating means 40 are calculated on the basis of the X signal from 7, the Y signal from the Y signal amplifying means 38 and the digital data string stored in the storage means 41. Note that the digital data string stored in the storage means 41 is based on the X signal and the Y signal in a state where the pointing means 40 is not on the coordinate input panel 33.
This is data obtained as described later.

The control means 39 controls the operations of the storage means 41, the coordinate calculation means 42 and the AC applying means 36 to perform a coordinate detection operation. The DC power supply unit 43 supplies a DC power supply voltage to the coordinate calculation unit 42, the storage unit 41, the X signal amplification unit 37, the Y coordinate calculation unit 38, the control unit 39, and the AC application unit 36.

FIG. 2 shows the X signal amplifying means 37 and the Y signal amplifying means 37.
FIG. 3 is a detailed block diagram of a coordinate calculation unit 38. As shown in FIG. 2 (a), the X signal amplifying means 37
An amplifying circuit 45 for amplifying the X signal from the amplifier 4; an AC canceling circuit 46 for removing an AC component from the amplified X signal based on the AC signal; and a band-pass filter (BPF) 47
It is composed of Similarly, the Y signal amplifying means 38 includes an amplifying circuit 48, an AC canceling circuit 49, and a BPF 50, as shown in FIG.

FIG. 3 is a detailed block diagram of the coordinate calculating means 42. The coordinate calculating means 42 selects an X signal from the X signal amplifying means 37 when scanning the first electrode 31, and an analog switch 51 which selects a Y signal from the Y signal amplifying means 38 when scanning the second electrode 32. And a Y-signal, a sample-and-hold circuit 52 for sampling and holding a signal selected by the analog switch 51 at predetermined intervals, an A / D converter 53 for digitally converting the sampled and held voltage value, and a sampling value after A / D conversion A subtractor 54 for sequentially subtracting the time series of the digital data stored in the storage means 41 from the time series described above, an absolute value calculator 55 for calculating the absolute value of the digital value after the subtraction, and comparing the obtained absolute values. The time from the start of scanning of the comparator 56, the first electrode 31 or the second electrode 32 for obtaining the maximum value to the time when the maximum value is obtained Coordinate value x of the position indicated by the pointing means 40 on the basis of Tsu number of clock), and a coordinate calculator 57 for calculating a y.

The coordinate input device having the above configuration operates as follows. 100 V AC by the DC power supply means 43
A predetermined DC voltage is generated from the
6, control means 39, X signal amplifying means 37, Y signal amplifying means 38, coordinate calculating means 42 and storage means 41.

The AC applying means 36 has an oscillation circuit (not shown), and generates a sine wave AC signal (hereinafter referred to as an excitation signal) having a predetermined DC component. Then, the generated excitation signal is supplied to the first switching unit 34, the second switching unit 35,
The signal is supplied to the X signal amplifier 37 and the Y signal amplifier 38.

The control means 39 has a clock generator (not shown), and generates a timing signal by combining clocks from the clock generator. Then, based on the generated timing signal, the operations of the first switching unit 34, the second switching unit 35, the storage unit 41, and the coordinate calculation unit 42 are controlled to perform a series of coordinate detection operations.

Then, the first switching means 34 sequentially selects one or several first electrodes 31 from one end of the plurality of first voltages 31 and selects the selected electrode Xs, which is the selected first electrode. Is connected to the X signal amplifying means 37. on the other hand,
An unselected electrode Xns, which is a first electrode that is not selected, is connected to the AC applying means 36 to apply a predetermined AC voltage Vx. Thus, the first electrode 31 is scanned. Similarly, the second switching means 35 sequentially selects one or several second electrodes 32 from one end side of the plurality of second voltages 32, and outputs the selected electrode Ys which is the selected second electrode to the Y signal. Connect to amplifying means 38. On the other hand, a non-selected electrode Yns, which is a second electrode that is not selected, is connected to the AC applying means 36 to connect a predetermined AC voltage Vy.
Is applied. Thus, the second electrode 32 is scanned.

The X signal amplifying means 37 converts the detection current flowing through the selection electrode Xs received from the first switching means 34 into
After the current is amplified by the amplifier circuit 45, the voltage is amplified to a predetermined voltage. Then, the AC component is removed by the AC cancellation circuit 46 by taking a difference from the AC signal (excitation signal) input from the AC applying means 36. After that, BPF4
7 to obtain an X coordinate detection voltage. The X coordinate detection voltage thus obtained is output to the coordinate calculation means 42. Similarly, the Y signal amplifying unit 38 converts the detected current flowing through the selection electrode Ys received from the second switching unit 35 into an amplifying circuit 48.
And then amplify the voltage to a predetermined voltage. And
The AC component is removed by the AC cancel circuit 49 by taking a difference from the excitation signal from the AC applying means 36.
After that, the Y-coordinate detection voltage is obtained through the BPF 50. The Y-coordinate detection voltage obtained in this manner is used by the coordinate calculation means 4.
2 is output.

Then, based on the timing signal from the control means 39, the X-coordinate detection voltage is selected by the analog switch 51 of the coordinate calculation means 42 when the X-coordinate is detected, while the Y-coordinate detection voltage is selected when the Y coordinate is detected. Is selected. Then, the selected coordinate detection voltage is
The sample and hold circuit 52 performs sample and hold at a predetermined timing T (i) (i = 1, 2,..., N) set in advance. The sampled and held coordinate detection voltage is A / D-converted by the A / D converter 53 to obtain digital data strings Dx (i) and Dy (i). Then, the digital data sequence (correction data at each timing T (i)) stored in the storage means 41 is subtracted by the subtractor 54, and the absolute value of the corrected digital coordinate detection voltage is calculated by the absolute value calculator 55. Dax (i) and Day (i) are calculated. Further, the comparator 42 compares the absolute values Dax (i) and Day (i) at each timing T (i) to determine the maximum value, and the coordinate calculator 57 calculates the maximum value based on the number of clocks up to the maximum value. Coordinate values x and y are calculated.

Here, as will be described in detail later, in the storage means 41, when there is no indication means 40 on the coordinate input panel 33, the first and second switching means 34 and 35, the X and Y signal amplifying means are provided. 37, 38, and digital data strings Dnx (i) and Dny (i) calculated by the coordinate calculation means 42 in the same manner as in the state where the above-mentioned indicating means 40 is present (but without performing the above-mentioned correction). Is stored.

Next, the principle of detecting coordinates in this embodiment will be described. As shown in FIG. 4, a pointing means 40 or a finger (hereinafter referred to as pointing means 40) which is a conductor held in a hand.
) On the coordinate input panel 33, all the first electrodes 31, 31,... And all the second electrodes 3
, And the indicating means 40 are electrostatically coupled. However, the shorter the electrodes 31 and 32 are, the larger the coupling capacity is. Therefore, if the positions of the electrodes 31 and 32 that are most strongly coupled to the indicating means 40 are known, it is understood that the vicinity thereof is the position indicated by the indicating means 40. Then, more current flows as the electrodes 31 and 32 are more strongly coupled to the indicating means 40. Therefore, the first electrode 31 and the second electrode 32 are sequentially scanned from the end to check the electrodes 31 and 32 through which the strongest current flows, and it is determined that the indicating means 40 exists near the electrodes 31 and 32.

FIG. 5 is an equivalent circuit of the coordinate detection system. The power supply circuit 61 has an impedance Zc and is grounded. The excitation signal voltage generation source 62 is
1 connected in series to generate an excitation signal voltage Vsin.
Cp1 is the electrostatic coupling capacitance between the indicating means 40 and the selection electrodes Xs, Ys. Further, Cp2 is the value of the indicating means 40 and the selection electrode X.
Electrostatic coupling capacitance with electrodes other than s and Ys (non-selection electrodes Xns and Yns and non-detection-side electrodes (second electrode 32 when first electrode 31 is selected or first electrode 31 when second electrode 32 is selected)) It is. Numeral 63 denotes a human body model electrostatically coupled to the ground expressed as a lumped constant, and the resistance Rh
And a capacitance Ch in series. In the present embodiment, in the equivalent circuit, by measuring selected electrodes Xs and instruction means 40, the current flowing between the Ys (i.e., the current flowing through the electrostatic coupling capacitance Cp1) to i ₁ by the ammeter 64 , The position of the indicating means 40 is detected.

FIG. 6 is a diagram showing the X-coordinate detection voltage Vsx and the sample-and-hold timing signal at the time of X-coordinate detection, which are input to the sample and hold circuit 52 of the coordinate detection calculation means 42. Here, by scanning the first electrode 31,
An X coordinate detection voltage Vsx having a waveform as shown in FIG. 6A is obtained. The cycle of the X coordinate detection voltage Vsx is the cycle of the excitation signal. Therefore, the above sample hold is shown in FIG.
As shown in (b), if the cycle of the timing T (i) is set as the cycle of the excitation signal and sampling is performed at the peak of the X-coordinate detection voltage Vsx, the digital data string Dx (i) is obtained. It can be obtained with high accuracy.

As described above, the first switching means 34 is constituted by a group of analog switches. When the first electrodes 31 are scanned, each first electrode 31 is connected to the AC applying means 36.
And the X signal amplifying means 37, the switching noise occurs during the operation of the analog switch accompanying the scanning of the first electrode 31. Therefore, the waveform of the actual X coordinate detection voltage Vsx is, as shown in FIG.
The waveform has a noise component Vnoise caused by switching noise as shown in FIG. Therefore, if the X coordinate detection voltage Vsx is small, such as when the amplitude of the excitation signal cannot be made sufficiently large or when the electrostatic coupling between the indicating means 40 and the first electrode 31 is small, the noise component Vno
In many cases, ise becomes large, and the X-coordinate detection voltage Vsx does not take the maximum value at the position where the indicating means 40 is present as it is. Therefore, it is necessary to delete the noise component Vnoise from the X coordinate detection voltage Vsx.

The noise component Vnoise shows a fixed pattern on the coordinate input panel 33 irrespective of the presence or absence of the indicating means 40. Therefore, in the present embodiment, the above-described series of coordinate detection operations is performed in a state where the pointing means 40 is not placed on the coordinate input panel 33. Then, a digital data string Dnx (i) at the sample and hold timing T (i) of the noise component Vnoise on the entire surface of the coordinate input panel 33 is obtained and stored in the storage means 41. At the time of coordinate input, as described above, the digital data at the same timing T (i) is subtracted from the digital data sequence Dx (i) sampled and held at the timing T (i) and A / D converted by the subtractor 54. Row Dnx
(i) is corrected by subtracting the noise component Vnoise from the digital data string Dax (i)
Is obtained.

The X-coordinate detection operation and the Y-coordinate detection operation are performed in a time-division manner.
The Y coordinate detection operation for scanning the electrode 32 is basically the same as the X coordinate detection operation. Therefore, similarly to the above-described correction processing at the time of the X coordinate detection operation, the digital data sequence Dny (i) at the timing T (i) without the instruction means 40 is obtained and stored in the storage means 41, Subtractor 5 from digital data string Dy (i) obtained at the time of input
By subtracting the digital data string Dny (i) by 4, a digital data string of the Y coordinate detection voltage from which the noise component Vnoise has been deleted can be obtained. Thus, good coordinate detection can be realized even when the actual X coordinate detection voltage and the actual Y coordinate detection voltage due to the presence of the indicating means 40 are small.

As described above, in the above-described embodiment, the first switch 31 and the second switch 35 operate the first electrode 31 and the second switch 31 in advance without placing the indicator 40 on the coordinate input panel 33. The electrode 32 is scanned. Then, the X signal and the Y signal from the selection electrodes Xs and Ys are amplified by the X signal amplifying means 37 and the Y signal amplifying means 38 to remove the AC component. After that, the coordinate calculation means 42 samples and holds the X coordinate detection voltage Vsx from the X signal amplification means 37 or the Y coordinate detection voltage Vsy from the Y signal amplification means 38 at timing T (i), and performs A / D conversion. .
The digital values thus obtained are stored as digital data strings Dnx (i) and Dny (i) of the noise component Vnoise in the storage means 4.
1 is stored.

On the other hand, at the time of inputting coordinates, the coordinate input panel 33 is operated by the first switching means 34, the second switching means 35, the X signal amplifying means 37, the Y signal amplifying means 38 and the coordinate calculating means 42 in the same manner as described above. Instruction means 40 above
To obtain digital data strings Dx (i) and Dy (i). Since the noise component Vnoise is superimposed on the digital data strings Dx (i) and Dy (i), the subtractor 54 of the coordinate calculation means 42 calculates the noise component Vnoise stored in the storage means 41. The digital data strings Dnx (i) and Dny (i) are subtracted. In this way, a digital data sequence of the coordinate detection voltage from which the noise component Vnoise has been removed when the pointing means 40 is present on the coordinate input panel 33 is obtained, and the digital data of the coordinate detection voltage not including the noise component Vnoise is obtained. Based on the columns, the correct designated coordinates x, y of the pointing means 40 on the coordinate input panel 33 can be calculated.

That is, in the present embodiment, prior to calculating the input coordinate value, the noise component is directly removed from the coordinate detection voltage itself as the coordinate detection signal. Therefore, the level of the coordinate detection voltage due to the presence of the indicating means 40 is small with respect to the noise and S
Even when the / N ratio is low, correct coordinate detection can be performed. In this case, it is only necessary to provide the storage means 41 in the system memory or the like, so that a high-quality coordinate input device can be provided at low cost.

<Second Embodiment> FIG. 8 is a functional block diagram of a coordinate input device according to the second embodiment. In this coordinate input device, an image display panel (TFT (thin film transistor) liquid crystal panel) is used as the coordinate input panel 71. That is, the display first electrode 72 connected to the source electrodes of the pixel display TFTs arranged in parallel with each other and arranged in a matrix is used as the first electrode for coordinate detection in the first embodiment. Used in the same manner as 31. Similarly,
A second display electrode, which is arranged orthogonal to the first electrode 72 and parallel to each other, and connected to the gate electrode of the TFT.
The electrode 73 is connected to the second electrode for detecting coordinates in the first embodiment.
Used in the same manner as the electrode 32. As described above, in the present embodiment, by using the image display panel as the coordinate input panel 71, the display quality can be improved, the thickness can be reduced, and the cost can be reduced without stacking the coordinate input panel 71 on the image display panel. Is possible.

Further, the first driving means 74 for driving the first electrode 72 at the time of displaying an image is used in the same manner as the first switching means 34 for detecting coordinates in the first embodiment. Similarly, a second driving unit 75 that drives the second electrode 73 during image display
Is used in the same manner as the second switching means 35 for detecting coordinates in the first embodiment. Incidentally, as in the case of the first embodiment, the arrangement direction of the first electrodes 72 (the extending direction of the second electrodes 73).
Is called the X direction, and the arrangement direction of the second electrode 73 (the first electrode 7
2 is referred to as a Y direction.

Further, the X signal amplifying means 76, the Y signal amplifying means 77, the instruction means 78, the storage means 79 and the coordinate calculating means 80 are the X signal amplifying means 37 in the first embodiment.
It has the same configuration as the Y signal amplification means 38, the instruction means 40, the storage means 41, and the coordinate calculation means 42, and operates similarly.

The DC power supply means 81 generates a DC voltage of a predetermined voltage from AC 100 V, and supplies an AC application means 82, a panel control means 83, a control means 84, an X signal amplifying means 76,
Signal amplification means 77, coordinate calculation means 80, and storage means 79
To supply. The control means 84 controls the operation of the entire system in which the present coordinate input device is mounted. This control means 84
Has a clock generator (not shown), and generates a timing signal (control signal) by combining clocks from the clock generator. Then, the panel control unit 83 is controlled based on the generated control signal, so that an image display operation is performed during a display period described later in detail, and a coordinate detection operation is performed during a coordinate detection period. Further, the control signal is sent to the AC application unit 82.

The AC applying means 82 has an oscillation circuit (not shown), and has a sine wave AC signal having a predetermined DC component.
(Excitation signal). Then, the generated excitation signal is transmitted to the first driving unit 74, the second driving unit 75, and the X signal amplifying unit 7.
6 and the Y signal amplifying means 77. Further, the excitation signal is superimposed on the control signal from the control means 84 and transmitted to the panel control means 83. Panel control means 83
Divides one frame into a display period and a coordinate detection period as shown in FIG. In the display period, the first
By driving the driving means 74 and the second driving means 75, the image display panel 71 based on the image signal from the control means 84.
To display the image. On the other hand, during the coordinate detection period, the first
Driving means 74, second driving means 75, X signal amplifying means 76,
The Y signal amplification unit 77, the coordinate calculation unit 80, and the storage unit 79 are driven to perform a series of coordinate detection operations.

In the present embodiment, as described above, since the image display panel is used as the coordinate input panel 71, the voltage that can be applied to the first electrode 72 and the second electrode 73 is limited. This limitation is, for example, a limitation due to electrical characteristics of the first driving unit 74 and the second driving unit 75 or a limitation that does not affect display contents on the coordinate input panel 71. Since the first electrode 72 and the second electrode 73 are also used as electrodes for image display,
It is thinner than the first and second electrodes 31, 32 in the embodiment. Therefore, the first and second electrodes 72 and 73 and the indicating means 7
8, the level of a detection signal, which is a current flowing through the selection electrodes Xs and Ys during coordinate detection, is small.

The first and second driving means 74 and 75 operate as analog switches for selecting the selection electrodes Xs and Ys at the time of detecting coordinates, so that switching noise is generated. Therefore, as in the case of the first embodiment, the X-coordinate detection voltage Vsx and the Y-coordinate detection voltage Vsy include a noise component Vnoise. Then, as described above, the amplitude of the excitation signal cannot be made sufficiently large, and the electrostatic coupling between the first and second electrodes 72 and 73 and the indicating means 78 is small.
In some cases, the X-coordinate detection voltage Vsx and the Y-coordinate detection voltage Vsy exhibit the maximum values at locations other than the location where the indicating means 78 exists.

Therefore, the above-described series of coordinate detection operations is performed in a state where the pointing means 78 is not placed on the coordinate input panel 71, and the noise component Vnoise on the entire surface of the coordinate input panel 71 at the timing T (i) at the timing T (i). The data strings Dnx (i) and Dny (i) are obtained and stored in the storage means 79. At the time of inputting coordinates, the timing T
The same timing T (i) is obtained from the digital data strings Dx (i) and Dy (i) sampled and held in (i) and A / D converted.
The absolute values Dax (i) and Day (i) of the digital data string from which the noise component Vnoise has been deleted are obtained by subtracting the digital data strings Dnx (i) and Dny (i) in the above. Thus, good coordinate detection can be performed even when the S / N ratio of the coordinate detection voltages Vsx and Vsy is poor.

In the second embodiment, the control means 84 and the panel control means 83 are provided separately, but the control means may have the function of the panel control means. In the second embodiment, a TFT liquid crystal panel is used as the image display panel 71. However, the present invention is not limited to the TFT liquid crystal panel. For example, any image display panel having at least orthogonal first and second electrodes, such as a duty-type liquid crystal panel, an EL (electroluminescence) panel, and a plasma display, may be used.

In each of the above embodiments, the first and second switching means 34 and 35 and the first and second
The switching noise by the driving units 74 and 75 is described as an example. However, in practice, noise due to panel-specific noise, variations in circuit components, and variations in circuit adjustment may be superimposed. However, in each of the above embodiments, the digital data strings Dnx (i) and Dny (i) obtained by performing the coordinate detection operation in a state where the pointing means 40 and 78 are not placed on the coordinate input panels 33 and 71 are noise. Since the components are stored in the storage units 41 and 79, noise unique to the coordinate input panel 71, noise due to variations in circuit components, and variation in circuit adjustment are also removed during correction.

[0059]

As is apparent from the above description, the coordinate input device according to the first aspect of the present invention uses the first electrode and the second electrode of the coordinate input panel when the pointing means is not provided on the coordinate input panel. Is detected by the signal detecting means, converted into a digital data string by the signal converting means, and the obtained digital data string is stored in the storage means. Then, the digital data sequence obtained as described above in a state where the indication means is present on the coordinate input panel is corrected by the correction means using the digital data sequence stored in the storage means. Since a digital data string is generated and the designated coordinates by the indicating means are calculated by the calculating means based on the corrected digital data string,
Before the designated coordinate value is calculated, it is possible to obtain a digital data string of the coordinate signal in which a noise component indicating a fixed pattern is corrected on the coordinate input panel regardless of the presence or absence of the indicating means.

Therefore, even if the level of the coordinate signal due to the presence of the pointing means is smaller than the level of the noise component and the S / N ratio is poor, the coordinate input panel on the coordinate input panel by the pointing means can be used. The designated coordinates can be calculated correctly.

The first and second electrodes in the coordinate input device according to the second aspect of the present invention electrostatically couple with the indicating means to output the coordinate signal according to the coupling capacitance. On the basis of the coordinate signal, the designated coordinates on the coordinate input panel by the pointing means can be calculated.

Further, in the coordinate input device according to the third aspect of the present invention, the signal detecting means comprises a first signal detecting means and a second signal detecting means. The switching means sequentially selects the first and second electrodes on the coordinate input panel from one end side and switches and connects the first and second electrodes to the first and second signal detecting means. Means for switching connection, the first and second signal detection means, the signal conversion means, the storage means,
The correction means and the calculation means detect the designated coordinates on the coordinate input panel by the designation means, so that the coordinate signals output from the first and second electrodes in accordance with the coupling capacity with the designation means are generated. Based on this, even when the S / N ratio of the coordinate signal is poor, the coordinates designated by the pointing means on the coordinate input panel can be easily and correctly calculated.

The coordinate input panel in the coordinate input device according to the fourth aspect of the present invention also serves as an image display panel. When the control signal from the panel control means is a display control signal, the first and second coordinate input panels are used. The second driving means drives the display elements constituting each pixel on the image display panel based on the image signal from the panel control means. On the other hand, when the control signal is a detection control signal, The coordinate signal from the second electrode is sent to the signal detection means, and the signal detection means, signal conversion means, storage means, correction means and calculation means obtain the indicated coordinates on the coordinate input panel by the indication means. The coordinates designated by the designation means on the coordinate input panel also serving as the image display panel can be detected.

In this case, before calculating the designated coordinate value, a digital data string of the coordinate signal in which the noise component has been corrected can be obtained.
Even when the / N ratio is poor, the coordinates indicated by the indicating means can be correctly calculated.

The first and second electrodes in the coordinate input device according to the fifth aspect of the present invention electrostatically couple with the indicating means and output the coordinate signal according to the coupling capacitance. During the coordinate detection period, based on the coordinate signal,
The coordinates designated by the designating means on the coordinate input panel can be calculated.

In the coordinate input device according to the present invention, the signal detecting means comprises a first signal detecting means and a second signal detecting means, and the first and second driving means are provided during the coordinate detecting period. By means, the first and second electrodes on the coordinate input panel are sequentially selected from one end and connected to the first and second signal detection means, while the unselected first and second electrodes are connected to the AC application means. Since the connection is made, based on the coordinate signal output from the first and second electrodes according to the coupling capacity with the indicating means, even if the S / N ratio of the coordinate signal is poor, the image The coordinates designated by the designation means on the coordinate input panel also serving as the display panel can be easily and correctly calculated.

Further, since the panel control means in the coordinate input device of the invention according to claim 7 is a system control means for controlling the entire system, the configuration of the system equipped with the coordinate input device can be simplified. Cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a functional block diagram of a coordinate input device according to the present invention.

FIG. 2 is a detailed block diagram of an X signal amplifier and a Y signal amplifier in FIG.

FIG. 3 is a detailed block diagram of a coordinate calculation unit in FIG. 1;

FIG. 4 is an explanatory diagram of electrostatic coupling between first and second electrodes and an indicator in FIG. 1;

FIG. 5 is an equivalent circuit diagram of a coordinate detection system in the coordinate input device shown in FIG.

6 is a diagram showing an X coordinate detection voltage and a sample and hold timing signal input to the sample and hold circuit in FIG. 3;

FIG. 7 is a diagram illustrating a waveform of an actual X coordinate detection voltage on which a noise component is superimposed and a waveform of a noise component.

FIG. 8 is a functional block diagram of a coordinate input device different from FIG.

FIG. 9 is an explanatory diagram of a display period and a coordinate detection period.

FIG. 10 is an explanatory diagram of correction of variation in coordinate values due to variation in resistance values of resistors in a resistance-type tablet.

FIG. 11 is an explanatory diagram of correction of coordinate value variation due to variation in internal resistance value in the resistance type tablet.

FIG. 12 is an explanatory diagram of correction of variation in coordinate values due to variation in the number and length of lines in an electrostatic induction tablet.

FIG. 13 is an explanatory diagram of correction of variation in coordinate values in the electromagnetic induction type tablet.

FIG. 14 is an explanatory diagram of correction of variation in detected coordinate values due to an end electrode shape, a propagation delay, and the like in the display-integrated coordinate input device.

[Explanation of symbols]

31, 72: first electrode, 32, 73: second electrode
Electrodes, 33, 71: coordinate input panel, 34: first
Switching means, 35 ... second switching means, 36,
82 ... AC applying means, 37,76 ... X signal amplifying means,
38,77 ... Y signal amplifying means, 39,84 ... control means, 40,78 ... instruction means, 41,79 ...
Storage means, 42,80 ... coordinate calculation means, 5
4: Subtraction means 74: First driving means 75: Second driving means 83: Panel control means

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor ▲ Taka ▼ Kengo Hama 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Sharp Corporation

Claims (7)

[Claims] A first electrode arranged in parallel with each other and a second electrode arranged in parallel with each other in a direction orthogonal to the first electrode.
A coordinate input panel having electrodes; and a coordinate input device having an indicator for indicating a position on the coordinate input panel, wherein the first and second electrodes output coordinate signals corresponding to the position of the indicator. A signal detecting means for detecting a coordinate signal output from the first electrode and the second electrode; a signal converting means for converting a coordinate signal detected by the signal detecting means into a digital data string; Storage means for storing a digital data string from the signal conversion means when the indication means is not provided above; and a digital data string from the signal conversion means when the indication means is present on the coordinate input panel. Using the digital data sequence stored in the storage device to generate a corrected digital data sequence; Based on the barrel data column coordinate input device characterized by comprising a calculating means for calculating the indicated coordinate on the coordinate input panel according to the instruction unit. 2. The coordinate input device according to claim 1, wherein said first and second electrodes are electrostatically coupled to said indicating means so as to output said coordinate signal according to a coupling capacitance. A coordinate input device, comprising: 3. The coordinate input device according to claim 2, wherein said signal detecting means detects first signal detecting means for detecting a coordinate signal from said first electrode, and detects a coordinate signal from said second electrode. An AC applying means for generating and outputting an AC signal, and sequentially selecting a first electrode on the coordinate input panel from one end side to the first signal detecting means. A first switching means for switching and connecting a first electrode which is not selected to the AC applying means, and a second electrode on the coordinate input panel which is sequentially selected from one end and switched to the second signal detecting means. A second switching means for switching and connecting a second electrode that is not selected to the AC applying means while connecting, the first and second switching means, the first and second signal detecting means,
A coordinate input device comprising: a control unit that controls the signal conversion unit, the storage unit, the correction unit, and the calculation unit to detect a designated coordinate on the coordinate input panel by the instruction unit. 4. The coordinate input device according to claim 1, wherein the coordinate input panel has pixels arranged in a matrix, and the first and second electrodes are connected to a display element forming the pixels. The image display panel also serves as an image display panel, and outputs an image signal and a display control signal during a display period in which an image is displayed on the pixel, while detecting coordinates indicated by the indicating means on the coordinate input panel. A panel control means for outputting a detection control signal during the detection period, and being connected to the first electrode, receiving a control signal from the panel control means, and receiving the control signal from the panel control means in the case of the display control signal. Driving the display element on the basis of the image signal of the first driver, and in the case of the detection control signal, a first driver for transmitting a coordinate signal from the first electrode to the signal detecting means. And connected to the second electrode, receiving a control signal from the panel control means, and in the case of the display control signal, driving the display element based on an image signal from the panel control means. And a second drive unit for transmitting a coordinate signal from the second electrode to the signal detection unit in the case of the detection control signal, and the signal detection unit, the signal conversion unit, the storage unit, the correction unit, and the calculation unit. A coordinate input device which operates when receiving the detection control signal from the panel control means. 5. The coordinate input device according to claim 4, wherein said first and second electrodes are electrostatically coupled to said indicating means so as to output said coordinate signal according to a coupling capacitance. A coordinate input device, comprising: 6. The coordinate input device according to claim 5, further comprising: an AC applying unit that generates and outputs an AC signal, wherein the signal detecting unit detects a coordinate signal from the first electrode. A signal detection unit configured to detect a coordinate signal from the second electrode, wherein the first drive unit receives the detection control signal and receives the coordinate input panel. The upper first electrodes are sequentially selected from one end side and are connected to the first signal detecting means for switching connection, while the first electrodes which are not selected are connected for switching to the AC applying means, and the second driving means is provided. When the detection control signal is received, the second electrodes on the coordinate input panel are sequentially selected from one end side and are connected to the second signal detecting means, and the unselected second electrodes are connected to the AC signal. Coordinate input apparatus characterized by being adapted to switch connected to a pressurized device. 7. The coordinate input device according to claim 4, wherein said panel control means is a system control means for controlling the entire system.