JP2798552B2 - Display integrated tablet device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display-integrated tablet device used for a personal computer, a word processor and the like.

[0002]

2. Description of the Related Art As a means for inputting handwritten characters and figures to a computer or word processor, for example, a liquid crystal display and an electrostatic induction type tablet are stacked, and the characters and figures are statically written as if we were writing with paper. 2. Description of the Related Art A tablet device integrated with a display unit capable of inputting to an electric induction type tablet has been put to practical use. However, in this display unit integrated type tablet device, since the reflectance and the transmittance are different between the portion with and without the electrodes, the electrodes can be seen in a grid pattern on the display screen, causing a deterioration in the quality of the liquid crystal display. I have.

In view of the above, a tablet device with an integrated display as shown in FIG. 10 has recently been proposed as a tablet that eliminates such disadvantages (Japanese Patent Application No. 3-46751). This display-integrated tablet device serves both as a display electrode of a liquid crystal display and a coordinate detection electrode of a capacitance-type tablet device. Then, as shown in FIG. 11, a coordinate detection period for detecting designated coordinates on the tablet and a display period for displaying an image are provided during one frame period, and coordinate detection and image display are performed in a time-division manner. I have.

In FIG. 10, a liquid crystal panel 1 has common electrodes Y _{1 to} Y _n (hereinafter, an arbitrary common electrode is referred to as Y) and segment electrodes X _{1 to} X arranged orthogonally to each other.
_m (hereinafter, an arbitrary segment electrode is described as X) and a liquid crystal is interposed therebetween, and each pixel is formed in a region where each common electrode Y and the segment electrode X intersect. . That is, the liquid crystal panel 1 has pixels of n × m dots arranged in a matrix.

[0005] This display-integrated tablet device has the advantage that the grid-like electrode pattern is eliminated and is easier to see than the above-described liquid crystal display in which a capacitance type tablet is laminated. Since the electrode and the drive circuit are also used as the capacitive tablet, there is an advantage that the cost can be reduced and the size and weight can be easily reduced.

The display-integrated tablet device operates as follows. That is, the common drive circuit 2 for driving the common electrode Y and the segment drive circuit 3 for driving the segment electrode X are provided with a switching circuit 4
Are connected to the display control circuit 5 and the detection control circuit 6 via the. The switching circuit 4 is controlled by the control circuit 7 to output an output signal from the display control circuit 5 to the common drive circuit 2 and the segment drive circuit 3 during the display period, and to output the detection control circuit 6 during the coordinate detection period. Are output to the common drive circuit 2 and the segment drive circuit 3. In FIG. 10, the switching circuit 4, the display control circuit 5, the detection control circuit 6, and the control circuit 7 are represented by being divided into respective blocks. However, in an actual circuit, each of the above circuits is implemented as an LSI (Large Scale Integrated Circuit), and cannot be strictly divided into blocks as described above in terms of form.

During the display period, the shift data s is output from the shift data output terminal S of the display control circuit 5, the inverted signal fr is output from the inverted signal output terminal FR, and the clock signal cp1 is output from the clock output terminal CP1. The clock signal cp2 is output from the clock output terminal CP2.
There is output, the display from the data output terminal D0~D3 data D ₀ to D ₃ is output.

The clock signal cp1 is a clock signal having a period of displaying one row of pixels as a cycle. The clock signal cp1 is output to the clock input terminal YCK of the common drive circuit 2 via the output terminal CP10 of the switching circuit 4 as the clock signal cp1o. It is input to the latch pulse input terminal XLP of the segment drive circuit 3. The shift data s, which is a pulse signal for selecting a specific common electrode Y, is supplied to the shift data input terminal DIO1 of the common drive circuit 2 as the shift data so via the output terminal SO of the switching circuit 4, and the clock signal cp1o. Input in synchronization with.

When the shift data so is input to the common drive circuit 2, the pulse position of the shift data so is shifted by the shift register in synchronization with the clock signal cp1o, and the output of the common drive circuit 2 corresponding to the shift position is output. driving pulses of common electrode drive signals from terminal O1~On to the common electrodes Y ₁ -Yn is applied. This common electrode drive signal is supplied from a bias power supply V supplied from the DC power supply circuit 12.
It is generated based on ₀ ~V _5.

The clock signal cp2 is a clock signal whose period is a period obtained by dividing a period for displaying pixels of one row into several parts, and is output as a clock signal cp2o via the output terminal CP2O of the switching circuit 4 to the segment driving circuit 3. Is input to the clock input terminal XCK.

The display data D _{0 to} D ₃ are supplied to a switching circuit 4.
Display data D ₀ through the output terminal D0O~D3O of o~D
Input terminal XD0-XD of segment drive circuit 3 as ₃ o
3 and sequentially taken into a register in the segment drive circuit 3 in synchronization with the clock signal cp2o. And
When all the display data corresponding to the pixels of one row is captured, the captured display data is latched at the timing of the clock signal cp1o input to the latch pulse input terminal XLP, and the segment corresponding to each display data is obtained. driving pulses of the electrode driving signal is applied from the output terminal of the segment driving circuit 3 O1 to Om to the segment electrode X ₁ to X _m. The segment drive signal is also generated based on the bias power supply V ₀ ~V ₅ supplied from the DC power supply circuit 12.

The inversion signal fr is a signal for periodically inverting the application direction of the voltage applied to the liquid crystal during the display period to prevent the liquid crystal from being deteriorated by electrolysis.
The inverted signal input terminal Y of the common drive circuit 2 is output as the inverted signal fro via the inverted signal output terminal FRO of the switching circuit 4.
FR and inverted signal input terminal XFR of segment drive circuit 3
Entered as

[0013] Thus, the display is driven pixel matrix of the liquid crystal panel 1 according to the line sequence image corresponding to the display data D ₀ to D ₃ on the LCD panel 1 by the operation of the common drive circuit 2 and the segment drive circuit 3 It is done.

On the other hand, during the coordinate detection period, the shift data sd is output from the shift data output terminal Sd of the detection control circuit 6, and the inverted signal f is output from the inverted signal output terminal FRd.
rd is output, the clock signal cp1d is output from the clock output terminal CP1d, the clock signal cp2d is output from the clock output terminal CP2d, and the data output terminals D0d to D0d are output.
Drive data D ₀ d~D ₃ d is output from the 3d.

The clock signal cp1d is a clock signal having a period of a scanning period for scanning one common electrode Y, and is output as a clock signal cp1o via the output terminal CP10 of the switching circuit 4 to the clock input terminal of the common drive circuit 2. YCK and the latch pulse input terminal XLP of the segment drive circuit 3 are input. The shift data sd, which is a pulse signal for selecting a specific common electrode Y, is supplied to the shift data input terminal DIO1 of the common drive circuit 2 as the shift data so via the output terminal SO of the switching circuit 4, and the clock signal cp1d. Input in synchronization with.

Then, as in the above-described display period, the pulse position of the shift data so is shifted by the shift register of the common drive circuit 2 in synchronization with the clock signal cp1o, and the output terminal O1 corresponding to the shift position is shifted.
To the common electrodes Y ₁ to Y _{n from} the common electrode scanning signal y.
₁ ~y _n (hereinafter referred to as y any of the common electrode scanning signal) scan pulse is sequentially applied. The common electrode scanning signal y is generated based on the bias power supply V ₀ ~V ₅ supplied from the DC power supply circuit 12. The above clock signal cp
2d is a clock signal having a cycle of a scanning period for scanning the segment electrode X, and is an output terminal C of the switching circuit 4.
The clock signal cp2o is input to the clock input terminal XCK of the segment drive circuit 3 via P2O.

The drive data D ₀ d to D ₃ d are supplied to the drive data D ₀ o to D ₃ via output terminals D ₀ O to D _{3 O} of the switching circuit 4.
D ₃ o as an input terminal of the segment driving circuit 3 XD0～X
The signal is input to D3, and is sequentially taken into a register in the segment drive circuit 3 in synchronization with the clock signal cp2o. Then, scanning pulses of the segment electrode scanning signals x _{1 to} x _m (hereinafter, an arbitrary segment electrode scanning signal is described as x) corresponding to the drive data are output from the output terminals O 1 to Om of the segment driving circuit 3 to the segment electrodes X. is output to ₁ to X _m. The segment electrode scanning signal x is also supplied to the DC power supply circuit 12.
It is generated based on the bias power supply V ₀ ~V ₅ supplied from.

FIG. 12 is a timing chart of each scanning signal in the coordinate detection period of the display-integrated tablet device. The coordinate detection period is the x coordinate detection period followed by y
In the x-coordinate detection period, the segment electrode scanning signal x, which is a pulse voltage signal, is sequentially applied to the segment electrode X during the x-coordinate detection period, while the common electrode Y, which is a pulse voltage signal, is applied to the common electrode Y in the y-coordinate detection period. Electrode scanning signal y
Are sequentially applied.

By applying the pulse voltage signal, the segment electrode X or the common electrode Y and the designated coordinate detecting pen
A voltage is induced in the detection pen 8 by a stray capacitance between the detection pen 8 (hereinafter, simply referred to as a detection pen) and the tip electrode. The induced voltage generated in the detection pen 8 is amplified by the amplifier 9 and input to the x-coordinate detection circuit 10 and the y-coordinate detection circuit 11.
The x coordinate detection circuit 10 and the y coordinate detection circuit 11
Based on the output signal from the amplifier 9 and the timing signal from the control circuit 7, the time from when the pulse voltage signal is applied to when the induced voltage reaches the maximum value is detected. Detects the x coordinate or the y coordinate of the position indicated by.

FIG. 13 shows the positional relationship between the liquid crystal panel 1 and the detection pen 8. When the liquid crystal panel 1 is directly touched by the detection pen 8, stress is applied to the polarizing plate 14 and the liquid crystal sealing glass 15, and the transmittance of the liquid crystal panel 1 is modulated, so that a so-called Newton ring pattern appears. Therefore, an air gap 17 is provided by inserting a transparent protective plate 16 such as glass or acrylic material between the liquid crystal panel 1 and the detection pen 8 so that stress is not directly applied to the liquid crystal panel 1.

[0021]

However, FIG.
In the structure of the display-integrated tablet as shown in
Although the stress on the liquid crystal panel 1 can be avoided, the transparent protective plate 16 is greatly deformed by the stress, and the segment electrode X and the common electrode Y (hereinafter, simply referred to as a scanning electrode) of the liquid crystal panel 1 and the detection electrode of the detection pen 8. 13 greatly fluctuates. In a display-integrated tablet device, coordinate detection is performed using an electrostatic induction phenomenon. Therefore, the output of the detection pen 8 fluctuates in inverse proportion to the distance between the scanning electrodes X and Y and the detection electrode 13. Therefore, the conventional method of obtaining a detection pulse by binarizing the analog output of the detection pen 8 with a fixed threshold has a problem that a reliable detection pulse cannot be obtained for a detection signal having a small S / N ratio.

Here, the liquid crystal panel during the X-coordinate detection period in which the common electrode group is fixed at the voltage V ₀ , the segment electrode group is changed from the voltage V ₀ to the voltage V _5, and then changes to the voltage V ₀ again. 1 can be represented as shown in FIG. Incidentally, rcd ₁ ~rcd _n is the internal resistance of the common drive circuit 2, rsd ₁ ~rsd _m is the internal resistance of the segment drive circuit _{3, rc 1, 1 ~rc n} , m is the resistance of the common electrodes, rs _{1, 1}
To RS _{n, m} is the resistance of the segment electrode _{group, C 1, 1 ~C n,} m is the capacitance of each pixel of the liquid crystal.

In this case, ignoring the resistance values rs ₁ , _{1 to} rs _n , _m ,
rc ₁ , ₁ = rc ₁ , ₂ = ... = rc _n , _m = rc, rcd ₁ = rcd ₂ = ... =
_{rcd n = rcd, C 1,} 1 = C 1, 2 = ···· = C n, m = C, rsd 1 = rs
When _{d 2 = ···· = rsd m =} rsd, the equivalent circuit of Figure 14 is further simplified as shown in FIG. 15. In FIG. 15, the capacitor to which the voltage V ₀ is applied to the segment electrode has no charge, and the capacitor to which the voltage V ₅ is applied is charged by (V ₅ −V ₀ ) / n / C. ing.
In FIG. 15, the voltage V ₅ at the same time to the four segment electrodes are applied.

In the state of FIG. 15, when the scanning of the segment electrode group advances by one clock, the state of FIG. 16 is obtained. And
Potential discharge current flows through the capacitor of the segment electrode X has changed from V ₅ to V _0, the charging current flows through the capacitor of the segment electrode potential is changed to V ₅ from V _0. rc
Since / n is negligible compared to rsd, the charge / discharge current does not flow into the common driver.

[0025] However, as shown in FIG. 17, the common charging and discharging current of the capacitor to the scan starting segment electrode X (the voltage V ₅ is applied only to the nearest segment electrodes X ₁ to the common driving circuit 2) It flows into the drive circuit 2 and a voltage drop occurs due to the output impedance of the common drive circuit 2. These voltage drops overlap the entire common electrode group. Further, as shown in FIG. 18, since when the scan is finished (the voltage V ₅ only the farthest segment electrode Xm is applied from the common drive circuit 2) is voltage superimposed drop at the resistance of the common electrodes, scanning The noise at the end is larger than that at the start of scanning.

Also, as shown in FIG.
In the arrangement of the transparent protective plate 16 and the detection pen 8, the electrostatic coupling between the detection electrode 13 of the detection pen 8 and the common electrode group is strong,
The electrostatic coupling with the segment electrode group is very weak. For this reason, the influence of noise superimposed on the common electrode group is extremely large, and in a normal method of obtaining a coordinate pulse by binarizing the analog output of the detection pen 8 with a fixed threshold value, the detection pulse 8 is induced on the detection pen 8 when scanning the segment electrodes. The detected signal has a poor S / N ratio as shown in FIG. Therefore, there is a problem that a coordinate pulse for reliably detecting the x coordinate cannot be obtained.

In the electrostatic induction type tablet, a detection signal is obtained from the output of the detection pen 8 as a signal from which a DC component has been lost. The detection pen output in the display-integrated tablet device using the electrostatic induction type tablet includes a liquid crystal display polarity inversion pulse, a y-coordinate detection pulse, or an x-coordinate detection pulse during a display period, a y-coordinate detection period, and an x-coordinate detection period, respectively. The detection pulse is obtained as an analog signal. Therefore, a delay of a low frequency component occurs due to capacitive coupling in the x coordinate detection circuit 10 and the y coordinate detection circuit 11. For this reason, there is a problem that each of the above-mentioned pulses causes low-frequency interference with other pulses and appears as a coordinate detection error.

Therefore, an object of the present invention is to enable stable coordinate detection even when the distance between the detection electrode of the detection pen, the segment electrode, and the common electrode fluctuates, and to generate an output signal from the detection pen at the end of scanning. It is an object of the present invention to provide a display-integrated tablet device with high coordinate detection accuracy, which can remove noise caused by noise and prevent interference of another pulse with the coordinate detection pulse of the output signal.

[0029]

In order to achieve the above object, a display-integrated tablet device according to a first aspect of the present invention includes a display material sandwiched between a group of orthogonal segment electrodes and a group of common electrodes. Panel driven by a type of driving method, a detection pen having at its tip an electrode electrostatically coupled to the segment electrode group and the common electrode group of the display panel, and a segment drive circuit for driving the segment electrode group A common drive circuit that drives the common electrode group; a display control circuit that controls the segment drive circuit and the common drive circuit during a display period to display an image on the display panel; Controlling the circuit to sequentially scan the segment electrode group of the display panel while controlling the common drive circuit to sequentially scan the common electrode group. An x-coordinate detection circuit for detecting an x-coordinate on a display panel indicated by the tip of the detection pen from a timing of generating an output signal from the detection pen and a timing of scanning the segment electrode group; In a display-integrated tablet device having a y-coordinate detection circuit that detects a y-coordinate on a display panel indicated by the tip of the detection pen from a generation timing of an output signal from the detection pen and a scanning timing of the common electrode group, The detection control circuit scans one of the segment electrode group or the common electrode group located on the detection pen side in the first scanning period, and performs the scanning in the second scanning period following the first scanning period. The segment drive circuit and the common drive circuit can be controlled to scan the other electrode group, and the first scan Receiving the output signal from the detection pen while detection hold the voltage variation of the one electrode group above between, comprises a detection circuit for outputting a reference signal corresponding to the voltage change of the one electrode group described above,
The coordinate detection circuit related to the other electrode group of the x-coordinate detection circuit or the y-coordinate detection circuit detects a coordinate detection pulse in an output signal from the detection pen based on a reference signal from the detection circuit. It is characterized by:

The display-integrated tablet device according to a second aspect of the present invention provides a display panel driven by a duty-type driving method by sandwiching a display material between orthogonal segment electrode groups and common electrode groups. A detection pen having at its tip an electrode electrostatically coupled to the segment electrode group and the common electrode group of the display panel, a segment drive circuit for driving the segment electrode group, and a common drive for driving the common electrode group A circuit, a display control circuit that controls the segment drive circuit and the common drive circuit during a display period to display an image on the display panel, and a segment electrode of the display panel that controls the segment drive circuit during a coordinate detection period. A detection control circuit for sequentially scanning the groups while controlling the common drive circuit to sequentially scan the common electrode group; An x-coordinate detection circuit for detecting an x-coordinate on the display panel indicated by the tip of the detection pen from the generation timing of an output signal from the scanning pen and the scanning timing of the segment electrode group, and generation of an output signal from the detection pen In a display-integrated tablet device having a y-coordinate detection circuit that detects a y-coordinate on a display panel indicated by the tip of the detection pen from the timing and the scan timing of the common electrode group, the detection pen is used in the display period. A detection circuit that receives the output signal, detects and holds the voltage change amount of the segment electrode group and the common electrode group, and outputs a reference signal corresponding to the voltage change of the segment electrode group and the common electrode group. The x-coordinate detection circuit and the y-coordinate detection circuit perform the detection based on the reference signal from the detection circuit. It is characterized in that to detect the coordinate detection pulse in the output signal from the pen.

A display integrated tablet device according to a third aspect of the present invention is the display integrated tablet device according to the first or second aspect of the present invention, wherein the x-coordinate detection circuit or the y-coordinate detection circuit includes an output from the detection pen. A detection circuit for detecting and holding a coordinate detection pulse in the signal and outputting a detection signal; a delay circuit for delaying the detection signal from the detection circuit for a predetermined time; a detection signal from the delay circuit and an output from the detection pen And a synthesizing circuit for synthesizing the signal and suppressing noise following the peak of the coordinate detection pulse in the detection signal.

The display integrated tablet device according to a fourth aspect of the present invention is the display integrated tablet device according to any one of the first to third aspects, wherein the x coordinate detection circuit and the y coordinate detection circuit are In synchronization with the display period, the scanning period of the segment electrode group or the scanning period of the common electrode group,
An output signal from the detection pen in the display period, an output signal from the detection pen in the segment electrode group scanning period, or an output signal from the detection pen in the common electrode group scanning period, which is one different output signal. It has three clamp circuits for taking in the display signal inversion pulse, x-coordinate detection pulse, and y-coordinate detection pulse included in the output signal from the detection pen in time series. The feature is to prevent mutual interference.

[0033]

According to the first aspect of the present invention, one of the segment electrode group or the common electrode group located on the detection pen side is scanned during the first scanning period in the coordinate detection period based on the control of the detection control circuit. Is done. Then, an output signal from the detection pen at that time is input to a detection circuit, the voltage change amount of the one electrode group is detected and held, and a reference signal corresponding to the voltage change of the one electrode group is output. Is done. Then, the coordinate detection circuit for the other electrode group of the x-coordinate detection circuit or the y-coordinate detection circuit detects a coordinate detection pulse in the output signal from the detection pen based on the reference signal from the detection circuit.

In this way, the coordinate detection circuit for the other electrode group always outputs the signal from the detection pen based on the reference signal according to the voltage change amount of the one electrode group when the one electrode group is scanned. The coordinate detection pulse of the output signal is detected. Therefore, the level change of the output signal from the detection pen due to the change in the distance between the detection pen and the segment electrode or the common electrode is corrected by the reference signal.

In the second invention, an output signal from the detection pen during the display period is input to the detection circuit, and a reference signal corresponding to a voltage change of the segment electrode group and the common electrode group is output. Then, based on a reference signal corresponding to the voltage change amount of the segment electrode group and the common electrode group, a coordinate detection pulse of an output signal from the detection pen in a coordinate detection period is generated by an x coordinate detection circuit and a y coordinate detection circuit. Is detected.

In the third invention, the coordinate detection pulse in the output signal from the detection pen is detected and held by the detection circuit in the x-coordinate detection circuit or the y-coordinate detection circuit. Then, the detection signal from this detection circuit is delayed by a predetermined time by the delay circuit. Thereafter, the detection signal from the delay circuit and the output signal from the detection pen are synthesized by the synthesis circuit. Thus, noise following the peak of the coordinate detection pulse in the detection signal is suppressed.

In the fourth aspect, the output signal from the detection pen during the display period is captured by the clamp circuit that operates in synchronization with the display period. In addition, an output signal from the detection pen during the segment electrode group scanning period is captured by a clamp circuit that operates in synchronization with the segment electrode group scanning period. Further, an output signal from the detection pen during the common electrode group scanning period is captured by a clamp circuit that operates in synchronization with the common electrode group scanning period. Thus, mutual interference in the x-coordinate detection circuit and the y-coordinate detection circuit in the display voltage inversion pulse, the x-coordinate detection pulse, and the y-coordinate detection pulse included in the output signal from the detection pen in time series is prevented.

[0038]

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 block diagram showing a coordinate detection system in a display-integrated tablet device of this embodiment. Here, the same components as those in FIGS. 10 and 13 are denoted by the same reference numerals, and description thereof is omitted. In FIG. 1, 1 is a liquid crystal panel, 16 is a transparent protection panel, 13 is a detection electrode of the detection pen 8, and 9 is an amplifier structurally incorporated in the detection pen 8. 20 is a detection signal clamp circuit, 21 is a detection signal amplifier, 22 is an X coordinate signal clamp circuit, 23 is an X coordinate signal amplifier, 24 is a detection hold circuit, 25 is a delay element, 26 is a synthesizer, and 27 is a comparator. It is. 28 is a Y coordinate signal clamp circuit; 29 is a Y coordinate signal amplifier;
0 is a comparator, 32 is a display inversion signal clamp circuit, 33 is a detection hold circuit, and 7 is a control circuit.

From the control circuit 7, the coordinate detection period signal a, y coordinate detection period signal b, x
A coordinate detection period signal c and a display period signal d are output. Among them, the display period signal d may be a signal which is active only during the display voltage inversion period such as d ', or may be only the display voltage inversion timing immediately before the y coordinate detection period signal b becomes active such as d ". The detection signal induced at the detection electrode 13 of the detection pen 8 is indicated by e.

The detection signal e induced by the detection electrode 13 of the detection pen 8 and amplified by the amplifier 9 is input to the detection signal clamp circuit 20 and the display inversion signal clamp circuit 32 via a cable. As shown in FIG. 3A, the detection signal clamp circuit 20 and the display inversion signal clamp circuit 32 are composed of two resistors, one capacitor, and one voltage control switch element such as a transistor or a field effect transistor. 41. In that case, as shown in FIG. 3B, it may be combined with an operational amplifier.

In FIG. 3, when the active control voltage of 5 V is input to the control terminal, the impedance of the voltage control switch element 41 rises and the voltage control switch element 41 is turned off. On the other hand, when the inactive control voltage of 0 V is input, the voltage control switch element 41 is turned on.
State. While the control voltage is 0 V, the voltage control switch element 41 is kept in the “ON” state.
The voltage V ₂ in (a) or the current i ₂ in FIG. 3 (b) becomes “0”, and the input voltage V ₁ is completely cut off from the output side, and only charging and discharging of the capacitor is performed. Control voltage is canceled is cut off between the input side and the output side to vary the 5V from 0V, the electric charges of the capacitor charged immediately before, voltage V ₂ or current i ₂ rises from "0".

As shown in FIG. 2, the liquid crystal display polarity inversion pulse, the y coordinate detection pulse, and the x coordinate detection pulse are close in time. Further, the detection electrode 1 of the detection pen 8
Due to the high-pass filter effect caused by the capacitive coupling between the liquid crystal panel 3 and the liquid crystal panel 1, the delay of the low-frequency component of the immediately preceding signal is superimposed on the main signal component to be extracted. However, in the detection signal clamp circuit 20 or the display signal clamp circuit 23, since the input side and the output side are cut off by the switching operation of the voltage control switch element 41,
These low frequency components are not superimposed on the high frequency components.
Therefore, the low-frequency component is effectively removed by the capacitor and the resistor in the preceding stage of the voltage control switch element 41.

The configuration of the x detection signal clamp circuit 22 and the y detection signal clamp circuit 28 in FIG.
(a) or as shown in FIG. 3 (b).

The control terminal of the voltage control switch element 41 in the display inversion signal clamp circuit 32 has the configuration shown in FIG.
A display period signal d, which is active only during the display period as shown by, is applied. As a result, the detection signal e in FIG.
Only the liquid crystal display polarity reversal pulse passes through and is sent to the detection and hold circuit 33 in the next stage.

The detection and hold circuit 33 may be a peak hold circuit for detecting a peak value or an average value detection and hold circuit having an integration function. FIG. 4 shows an example of the peak hold circuit in that case, and FIG. 5 shows an example of the average value detection hold circuit. The detection hold circuit 33
Then, a DC voltage corresponding to the level of the liquid crystal display polarity inversion pulse is obtained and applied to one input terminal as a threshold voltage of the comparator 27 and the comparator 30 in the next stage.

On the other hand, a detection period signal a which is active only during the coordinate detection period as shown in FIG. 2 is applied to the control terminal of the voltage control switch element 41 in the detection signal clamp circuit 20. As a result, only the detection signal in the coordinate detection period including the y-coordinate detection pulse and the x-coordinate detection pulse passes and is input to the detection signal amplifier circuit 21 in the next stage. The detection signal amplified by the detection signal amplification circuit 21 is sent to the X detection signal clamp circuit 22 and the Y detection signal clamp circuit 28. Since the y-coordinate detection signal b shown in FIG. 2 is applied to the control terminal of the electronic control switch element of the Y-detection signal clamp circuit 28, only the y-coordinate detection signal passes. Then, the signal is amplified by the Y signal amplifier circuit 29 and supplied to the comparator 30.

At this time, the threshold voltage proportional to the magnitude of the liquid crystal display polarity inversion signal has already been applied from the detection hold unit 33 to the other input terminal of the comparator 30 as described above. Therefore, the comparator 30 outputs a y-coordinate signal having a positive pulse only when a y-coordinate detection pulse exceeding this threshold is detected.

Similarly, the X detection signal clamping circuit 22
Since the x-coordinate detection signal c shown in FIG. 2 is applied to the control terminal of the electronic control switch, only the x-coordinate detection signal passes. Then, the signal is amplified by the X signal amplification circuit 23 and supplied to the positive input terminal of the adder 26 and the detection hold circuit 24. The detection hold circuit 24 has the same configuration as the detection hold circuit 33, and outputs a DC voltage corresponding to the level of the x coordinate detection signal. However, this detection hold circuit 24 has an offset injection circuit, and FIG.
It has a dead zone as shown in the figure.

The output of the detection and hold circuit 24 is delayed by the delay element 25, applied to the negative input terminal of the adder 26, and combined with the original x-coordinate detection signal.

FIG. 7 shows output signals output from the detection hold circuit 24, the delay element 25, and the adder 26 when the x coordinate detection signal shown in FIG. 19 is input to the detection hold circuit 24. After detecting the x-coordinate detection pulse, the output signal from the adder 26 has a voltage corresponding to the level of the output signal from the detection and hold circuit 24 (that is, the level of the x-coordinate detection peak), and a noise component on the rear side. Is suppressed in the direction of the negative voltage. The same effect can be obtained by muting control of the output of the X signal amplifier 23 using the output of the delay element 25 as a digital control output.

The output of the adder 26 is applied to the input terminal of a comparator 27. A threshold voltage proportional to the magnitude of the liquid crystal display polarity inversion signal from the detection and hold circuit 33 has already been applied to the other input of the comparator 27. Therefore, the comparator 27 outputs an x-coordinate signal having a positive pulse only when an x-coordinate detection pulse exceeding this threshold is detected.

The x-coordinate pulse in the x-coordinate signal output from the comparator 27 and the y-coordinate pulse in the y-coordinate signal output from the comparator 30 reflect the position of the detection pen 8 on the tablet as a time position. Since the digital pulse is a digital pulse, an x-coordinate pulse of the x-coordinate signal or a y-coordinate pulse of the y-coordinate signal is obtained by using a counter which resets at the rise of the x-coordinate detection period signal c and the y-coordinate detection period signal b of the control circuit 7. If a logic circuit that stops counting at is used, the x-coordinate pulse or y
The time position of the coordinate pulse is obtained as a count value, and as a result, the position on the liquid crystal panel 1 indicated by the detection pen 8 can be known. FIG. 8 shows an example of the logic circuit.

As described above, in this embodiment, the detection signal clamp circuit 20, the display inversion signal clamp circuit 32, X
The detection signal clamp circuit 22 and the Y coordinate signal clamp circuit 28 separate the liquid crystal display polarity inversion pulse, the y coordinate detection pulse, and the x coordinate detection pulse from the detection signal induced on the detection electrode 13 of the detection pen 8. . Therefore, the liquid crystal display polarity inversion pulse can be input to the detection hold circuit 33, the x coordinate detection pulse to the X signal amplifier 23, and the y coordinate detection pulse to the Y signal amplifier 29 so as not to interfere with each other.

The detection hold circuit 33 obtains a DC voltage corresponding to the level of the liquid crystal display polarity inversion pulse.
Then, this DC voltage is used as a reference voltage for obtaining the x-coordinate detection pulse or the binarized pulse of the y-coordinate detection circuit in the comparators 27 and 28. In this case, the liquid crystal display polarity reversal pulse changes the detection electrode 13 of the detection pen 8 according to the distance between the segment electrode X and the common electrode Y. Therefore, the reference voltage also changes according to the distance. This means that both the detection signal voltage and the reference voltage input to the comparators 27 and 28 change according to the distance between the detection pen 8 and the segment electrode X and the common electrode. , 28 are signals that do not depend on the distance.

Further, a detection hold circuit 24 for detecting an x coordinate detection pulse, a delay element 25 and an adder 26 are added to the x coordinate detection circuit 10 so that the x coordinate detection signal passes through the detection hold circuit 24 and the delay element 25. The calculated x coordinate detection signal is added. As a result, when the x-coordinate detection pulse having the highest intensity is detected, the subsequent noise component can be suppressed.

<Second Embodiment> FIG. 9 is a block diagram showing a coordinate detection system in a display-integrated tablet device in this embodiment. However, the same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted. Since the S / N of the detection signal received from the common electrode located closer to the detection pen 8 is very good, a y-coordinate pulse with a sufficiently small error can be obtained even with a fixed threshold value. Therefore, if this is used, the first
The circuit scale of the coordinate detection system in the embodiment can be simplified.

However, it differs from the first embodiment in the following points. That is, a DC voltage proportional to the level of the y-coordinate detection pulse, which is generated earlier than the x-coordinate detection signal, is used as a reference of the comparator 27 for the x-coordinate detection signal. Therefore, in the present embodiment, the display inversion signal clamp circuit 32 and the detection hold circuit 33 for obtaining the DC voltage proportional to the level of the liquid crystal display polarity inversion pulse are removed, and the detection hold circuit 31 is added. The present invention is not limited to this.
9 and the x-coordinate detection system circuit and the y-coordinate detection system circuit in FIG. 9 are interchanged by reversing the vertical positional relationship between the common electrode group and the segment electrode group. No problem.

[0058]

As is apparent from the above description, the display-integrated tablet device of the first aspect of the present invention provides the tablet-side tablet device of the segment electrode group or the common electrode group during the first scanning period based on the control of the detection control circuit. Scans the upper electrode group located at the same time. At that time, the voltage change amount of the upper electrode group is detected and held by the detection circuit by the output signal from the detection pen, and the reference signal corresponding to the voltage change is output. Since the coordinate detection circuit relating to the lower electrode group among the coordinate detection circuit or the y-coordinate detection circuit detects the coordinate detection pulse in the output signal from the detection pen based on the reference signal, the lower electrode that is susceptible to external noise Can be changed based on the amount of voltage change during scanning of the upper electrode group.

Therefore, according to the present invention, the fluctuation of the output signal from the detection pen caused by the fluctuation of the distance between the detection electrode of the detection pen and the segment electrode and the common electrode is accurately corrected, and the coordinate is accurately obtained. Can be detected.

Further, in the display-integrated tablet device according to the second aspect of the present invention, during the display period, the voltage change of the segment electrode and the common electrode is detected and held by the detection circuit by the output signal from the detection pen, and the tablet circuit responds to the voltage change. A reference signal is output, and the x-coordinate detection circuit and the y-coordinate detection circuit detect a coordinate detection pulse in the output signal from the detection pen based on the reference signal. In the detection circuit, the fluctuation of the output effect from the detection pen can be corrected more accurately.

In the display-integrated tablet device according to the third aspect of the present invention, the detection circuit detects and holds the coordinate detection pulse in the output signal from the detection pen, further delays the detection pulse by a predetermined time by the delay circuit, and delays the delay by the synthesis circuit. Since the detection signal from the circuit is combined with the detection signal from the detection pen, noise following the peak of the coordinate detection pulse in the detection signal can be suppressed, and the accuracy of coordinate detection can be improved.

In the display-integrated tablet device according to the fourth aspect of the present invention, the three clamp circuits synchronized with the display period, the segment electrode group scanning period, and the common electrode group scanning period respectively provide the above-described three periods. Since the output signal from the detection pen is captured, mutual interference between the display voltage inversion pulse, the x coordinate detection pulse, and the y coordinate detection pulse in the x coordinate detection circuit and the y coordinate detection circuit can be prevented, and the coordinate detection accuracy can be improved. .

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of a coordinate detection system of a display-integrated tablet device of the present invention.

FIG. 2 is a timing chart of each period signal output from the control circuit shown in FIG. 1;

FIG. 3 is a diagram showing a specific example of a detection signal clamp circuit or a display inversion signal clamp circuit in FIG. 1;

FIG. 4 is a diagram showing a specific example of a peak hold circuit as a detection hold circuit in FIG. 1;

FIG. 5 is a diagram showing a specific example of an average value detection hold circuit as a detection hold circuit in FIG. 1;

FIG. 6 is a diagram illustrating input / output characteristics of a detection and hold circuit having an offset injection circuit.

FIG. 7 is a diagram showing output signal waveforms of respective circuits in a noise removal process at the end of scanning with respect to an x-coordinate detection signal.

FIG. 8 is an explanatory diagram of a logic circuit for obtaining an x coordinate and a y coordinate from the x coordinate signal and the y coordinate signal.

FIG. 9 is a block diagram of a coordinate detection system different from FIG.

FIG. 10 is a block diagram of a conventional display-integrated tablet device.

11 is a diagram showing an example of a display period and a coordinate detection period in the display-integrated tablet device shown in FIG.

12 is a timing chart of a segment electrode scanning signal and a common electrode scanning signal in the display-integrated tablet device shown in FIG.

FIG. 13 is an explanatory diagram of a positional relationship between a liquid crystal panel and a detection pen.

FIG. 14 is an equivalent circuit diagram of a liquid crystal panel.

FIG. 15 is an equivalent circuit diagram obtained by further simplifying FIG.

FIG. 16 is a diagram showing a state in which segment electrode scanning is advanced by one clock in FIG.

FIG. 17 is a diagram showing a state at the start of segment electrode scanning in FIG.

FIG. 18 is a diagram showing a state at the end of scanning of a segment electrode in FIG.

FIG. 19 is a diagram illustrating an example of an x-coordinate detection signal.

[Explanation of symbols]

1: liquid crystal panel, 8: detection pen, 2
0: detection signal clamp circuit, 22: X detection signal clamp circuit, 24, 31, 33: detection hold circuit, 25
... delay element, 26 ... adder, 2
7, 30: comparator, 32: display inversion signal clamp circuit.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Noriyoshi Kayoshi 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (56) References JP-A-1-280823 (JP, A) JP-A Sho 63-268027 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) G06F 3/03 G06F 3/033

Claims (4)

(57) [Claims] 1. A first electrode group and a first electrode group arranged in different directions.
Display having pixels corresponding to locations where two electrode groups intersect
A panel, a detection pen having at the tip a first electrode group and the second electrode group and the electrostatically coupled electrodes of the display panel, a first driving circuit for driving the first electrode group, the first
A second driving circuit for driving the second electrode group, the second display period
A display control circuit for controlling the first drive circuit and the second drive circuit to display an image on the display panel; and controlling the first drive circuit during a coordinate detection period to sequentially scan the first electrode group of the display panel . While controlling the second drive circuit to
A detection control circuit for sequentially scanning the second electrode group, and detecting the x coordinate on the display panel indicated by the tip of the detection pen from the generation timing of the output signal from the detection pen and the scanning timing of the first electrode group. Detecting the y-coordinate on the display panel indicated by the tip of the detection pen from the x-coordinate detection circuit, and the timing of generating the output signal from the detection pen and the scanning timing of the second electrode group.
In the display integrated tablet device having a coordinate detection circuit, the detection control circuit scans one of the first electrode group or the second electrode group located on the detection pen side during the first scanning period. In a second scanning period following the first scanning period, the first driving circuit and the second driving circuit can be controlled so as to scan the other electrode group, and from the detection pen in the first scanning period. And detecting and holding the voltage change amount of the one electrode group in response to the output signal, and outputting a reference signal corresponding to the voltage change of the one electrode group. The coordinate detection circuit relating to the other electrode group among the coordinate detection circuits is configured to detect a coordinate detection pulse in an output signal from the detection pen based on a reference signal from the detection circuit. Display-integrated type tablet device comprising. 2. A first electrode group and a first electrode group arranged in different directions.
Display having pixels corresponding to locations where two electrode groups intersect
A panel, a detection pen having at the tip a first electrode group and the second electrode group and the electrostatically coupled electrodes of the display panel, a first driving circuit for driving the first electrode group, the first
A second driving circuit for driving the second electrode group, the second display period
A display control circuit for controlling the first drive circuit and the second drive circuit to display an image on the display panel; and controlling the first drive circuit during a coordinate detection period to sequentially scan the first electrode group of the display panel . While controlling the second drive circuit to
A detection control circuit for sequentially scanning the second electrode group, and detecting the x coordinate on the display panel indicated by the tip of the detection pen from the generation timing of the output signal from the detection pen and the scanning timing of the first electrode group. Detecting the y-coordinate on the display panel indicated by the tip of the detection pen from the x-coordinate detection circuit, and the timing of generating the output signal from the detection pen and the scanning timing of the second electrode group.
In the display-integrated type tablet device having a coordinate detection circuit receives an output signal from the detection pen while detection hold the voltage variation of the first electrode group and the second electrode group in the display period, the first electrode A detection circuit that outputs a reference signal according to a voltage change of the group and the second electrode group, wherein the x-coordinate detection circuit and the y-coordinate detection circuit are configured to output a reference signal from the detection pen based on the reference signal from the detection circuit. A display-integrated tablet device, wherein a coordinate detection pulse in an output signal is detected. 3. The display-integrated tablet device according to claim 1, wherein the x-coordinate detection circuit or the y-coordinate detection circuit detects and holds a coordinate detection pulse in an output signal from the detection pen. A detection circuit that outputs a detection signal together with the detection signal; a delay circuit that delays the detection signal from the detection circuit for a predetermined time; and a synthesis circuit that combines the detection signal from the delay circuit and the output signal from the detection pen. A display-integrated tablet device, wherein noise following a peak of a coordinate detection pulse in the detection signal is suppressed. 4. A first electrode group and a first electrode group arranged in different directions.
Display having pixels corresponding to locations where two electrode groups intersect
Panel, first electrode group and second electrode of the display panel
Sensing pen with tip at the tip electrostatically coupled to group
A first drive circuit for driving the first electrode group;
A second driving circuit for driving the two electrode groups;
The display panel is controlled by controlling the first drive circuit and the second drive circuit.
A display control circuit for displaying images on Le, the coordinate detection period
Controlling the first driving circuit to control a first electrode of the display panel;
Controlling the second drive circuit while sequentially scanning the groups,
A detection control circuit for sequentially scanning the second electrode group;
Timing of the output signal from the
Instructed by the tip of the detection pen from the scanning timing
X-coordinate detection circuit for detecting the x-coordinate on the display panel
And the generation timing of the output signal from the detection pen
From the scanning timing of the second electrode group, the tip of the detection pen
For detecting the y coordinate on the display panel specified by y
In a display integrated tablet device with a coordinate detection circuit
Te, the x-coordinate detection circuit and the y-coordinate detection circuit, the display period, in synchronization with the first electrode group scanning period or the second electrode group scanning period, the output signal from the detection pen in the display period, the first The apparatus further comprises three clamp circuits that capture one different output signal of the output signal from the detection pen during the one electrode group scanning period or the output signal from the detection pen during the second electrode group scanning period. A display for preventing mutual interference in the x-coordinate detection circuit and the y-coordinate detection circuit in the display voltage inversion pulse, the x-coordinate detection pulse, and the y-coordinate detection pulse included in the output signal from the pen in time series. Integrated tablet device.