JP3296977B2 - 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 tablet device for detecting coordinates indicated by a detection pen on a display screen of a word processor or the like.

[0002]

2. Description of the Related Art As a means for inputting handwritten characters and figures to a computer or a word processor, for example, when a liquid crystal display and an electrostatic induction type tablet are stacked and we write characters and figures on paper using a writing instrument There is a multi-layer tablet device capable of inputting characters and figures with a feeling similar to that of the tablet device. When characters or figures are input to the electrostatic induction tablet using a coordinate input pen or the like, the coordinates indicated by the pen are detected, and data representing the detected coordinates is provided to the liquid crystal display. The liquid crystal display performs display based on given data. Therefore, the same characters and figures as those input to the tablet using the pen are displayed on the liquid crystal display.

[0003] In the laminated tablet device, since the reflectance and the transmittance are different between the electrode portion of the electrostatic induction type tablet and the portion without the electrode, there is a problem that the electrodes are seen in a grid pattern on the display screen. As a technique for solving this inconvenience, a display-integrated tablet device has been devised.

FIG. 12 shows a display-integrated tablet device having a duty-type liquid crystal panel 1, FIG. 13 is a timing chart for explaining the operation of the display-integrated tablet device, and FIG. It is a timing chart of a signal. The display-integrated tablet device combines the display electrode of the liquid crystal display 1 with the coordinate detection electrode of the electrostatic induction tablet device,
The coordinate detection and the image display are performed in a time-division manner.

The liquid crystal panel 1 has n common electrodes Y1 to Yn (referred to as a reference Y when collectively referred to) and m segment electrodes X1 to Xm (referred to as reference when referred to collectively). X is used) and a liquid crystal is interposed therebetween. In the liquid crystal panel 1, each common electrode Y
Each of the regions where the pixel and the segment electrode X intersect is a pixel, and n × m pixels are arranged in a matrix. Common drive circuit 2 and segment drive circuit 3
Applies a voltage supplied from the DC power supply circuit 12 selectively to each of the electrodes X and Y.

As shown in FIG. 13, when scanning is performed for the N-th frame period in the period T1, (N
The scanning of the (+1) th frame period is performed. Period T1
Is configured to include a display period T3 and a coordinate detection period T4. During the display period T3, each switching signal from the display control circuit 5 to which the display data is supplied from an external device (not shown) is selected by the switching circuit 4 and supplied to the common drive circuit 2 and the segment drive circuit 3. The common electrode drive circuit 2 applies a drive pulse of a common electrode drive signal to the common electrode Y, and the segment electrode drive circuit 3 applies a drive pulse of the segment electrode drive signal to the segment electrode X. In the coordinate detection period T4, each detection control signal from the detection control circuit 6 is selected by the switching circuit 4 and supplied to the common drive circuit 2 and the segment drive circuit 3. The coordinate detection period T4 is an x coordinate detection period T5
1 and a y-coordinate detection period T6.
As shown in FIG. 4, during the x coordinate detection period T5, the segment electrode drive circuit 3 causes the segment electrode scanning signals SX1 to SX
Xm scanning pulses are sequentially applied, and the y-coordinate detection period T6
In the example, the common electrode drive circuit 2 sequentially applies the scan pulses of the common electrode scan signals SY1 to SYn.

When a scanning pulse is applied, a stray capacitance between the segment electrode X or the common electrode Y and a detection electrode provided at the tip of a designated coordinate detection pen (hereinafter, simply referred to as a “detection pen”) 8 is used. A voltage is induced. The voltage induced by the detection pen 8 is converted to a pulse conversion circuit 9
Given to. The pulse conversion circuit 9 makes a comparison between the applied voltage and a predetermined voltage to generate a pulse-like signal, and outputs the signal to the x-coordinate detection circuit 10 and the y-coordinate detection circuit 11. x coordinate detection circuit 10 and y coordinate detection circuit 11
Detects the x-coordinate or the y-coordinate of the position indicated by the detection pen 8 based on the timing signal supplied from the control circuit 7 to which the display synchronization signal is given.

FIG. 15 is a waveform diagram for explaining the operation of the pulse conversion circuit 9 in the display-integrated tablet device. For example, when a scan pulse having a pulse width of W1 shown in (1) is applied to the segment electrode X of the liquid crystal panel 1 in the x coordinate detection period T5, the detection electrode of the detection pen 8 has a waveform (2). Is induced. The voltage detected by the detection electrode is binarized based on a slice voltage Es predetermined by a comparator included in the pulse conversion circuit 9. After being binarized by the comparator, the x-coordinate detection circuit 1 outputs a detection pulse shown in (3).
0 is given. The pulse width of the detection pulse is width W2.

In the x coordinate detection period T5, when the detection electrode detects noise from an external device, a plurality of pulses are generated as detection pulses. The x-coordinate detection circuit 10 obtains and outputs the coordinates for all the applied detection pulses, so that data indicating coordinates different from the coordinates indicated by the detection pen 8 is provided to an external circuit (not shown). The external circuit processes the given data as, for example, drawing data, and updates the display data. When the data is used as drawing data, coordinates due to external noise are displayed at undesired positions in addition to the locus of the detection pen 8. When the external circuit uses the given data as the pointing data instead of using it as the drawing data, the display mode is switched to the display mode according to the pointing position. In this case, if the coordinates indicated by the data and the coordinates indicated by the detection pen 8 are different, a malfunction may occur.

The voltage induced on the detection electrode of the detection pen 8 is extremely weak. In particular, in the case of a display-integrated tablet device having a duty-type liquid crystal panel 1, the electric field generated by the segment electrodes located below the detection surface is shielded by the upper electrodes, so that the lower electrodes are scanned. In this case, the induced voltage at the detection electrode of the detection pen 8 becomes a particularly weak signal of about several mV.

FIG. 16 shows a display-integrated tablet device having an active matrix type liquid crystal panel 21. In the liquid crystal panel 21, n gate bus line electrodes G1 to Gn (a G is used when collectively referred to) and m
The source bus line electrodes S1 to Sm (the reference numeral S is used when collectively referred to) are arranged orthogonally to each other and insulated. A TFT (thin film transistor) 25 is disposed in a region formed by the gate bus line electrode G and the source bus line electrode S, and a pixel electrode 24 is connected to the TFT 25. One pixel electrode 24 corresponds to one pixel. Therefore, the liquid crystal panel 21 has n × m
The display pixels of dots are arranged in a matrix. The liquid crystal panel 21 is provided with a counter electrode (not shown) so as to face the pixel electrode 24, and performs display by applying a voltage to a liquid crystal layer sandwiched between the two electrodes. A voltage is applied to each of the electrodes S and G of the liquid crystal panel 21 by the gate electrode drive circuit 22 and the source electrode drive circuit 23 to perform display. Other configurations are the same as those of the display-integrated tablet device shown in FIG.

In the coordinate detection period T4, the liquid crystal panel 1
The detection pen 8 is positioned on the input surface of the liquid crystal panel 21, and the electrostatic force between the detection electrode of the detection pen 8 and the gate bus line electrode G or the source bus line electrode S is the same as in the case of the display integrated tablet device having Detection pen 8 by coupling
, The voltage induced on the detection electrode is detected, and the x-coordinate detection circuit 10 or the y-coordinate detection circuit 11 detects the voltage.
Find the coordinates indicated by.

In the case of a display integrated tablet device having an active matrix type liquid crystal panel 21, T
The source bus line electrode S and the gate bus line electrode G for driving the FT 25 are used as scanning electrodes. However, since the electrode width of each of the source bus line electrode S and the gate bus line electrode G is about several tens μm,
The induced voltage induced on the detection electrode of the detection pen 8 is also extremely weak.

As described above, in the display-integrated tablet device having the duty type liquid crystal panel 1 and the display-integrated tablet device having the active matrix type liquid crystal panel 21, the detection electrode of the detection pen 8 is used during the coordinate detection period T4. The induced voltage is very weak and very susceptible to noise from external devices.

As an example of noise in the display-integrated tablet device, when writing characters or figures on the liquid crystal panels 1 and 21 with the detection pen 8, a detection electrode 57 is attached to the tip of a detection pen 38 shown in FIG. There is noise caused by friction between the tip resin 58 which is a dielectric formed so as to cover the protection plate 56 and the protection plate 56, thereby causing noise. The electric charge due to the triboelectric charging gradually attenuates due to the leakage current of the resin portion and the protection plate, and thus does not pose a problem under normal conditions.

However, when the display-integrated tablet device is used in a very dry environment with low humidity,
The resistance value of the resin portion increases, and the voltage due to triboelectric charging becomes higher than under normal conditions. If the voltage generated by the friction is higher than the voltage attenuated by the leak current, the electric charges will be accumulated in the panel, and if the voltage exceeds the limit in the panel, the portion having a small charge amount will be discharged instantaneously. Since the voltage of the charged portion changes instantaneously by the discharge, a spike-like voltage is induced on the detection electrode of the detection pen 8. The voltage generated at the detection electrode is supplied to each of the coordinate detection circuits 10 and 11, and is processed in the same manner as the voltage generated by scanning the electrode.

Another example of the noise in the display-integrated tablet device is a noise generated by bringing an electric device operating at a relatively high frequency and a high voltage close to the coordinate input surfaces of the liquid crystal panels 1 and 21. is there. Further, the influence of power supply noise in the detection pen 8 and the pulse conversion circuit 9 may be considered.

Unnecessary signals are superimposed on the actual detection signal due to the influence of noise as described above, and a pulse is detected other than the detection pulse induced on the detection electrode by scanning the scanning electrode. In addition, the original detection pulse may be erased, and the coordinate pointed by the tip of the detection pen 8 may not be correctly detected.

FIG. 17 shows waveforms for explaining the state of the erroneously detected pulse. The waveform shown in (a) shows the waveform of the detection pulse 101 which is not affected by noise in a normal state. The detection pulse 101 shown in FIG.
Similarly to the detection pulse shown in (3), the width of the pulse is W2.

In the display-integrated tablet device, a detection signal shown in (b) to (f) is converted from the pulse conversion circuit 9 to the x-coordinate detection circuit 10 by superimposing a noise signal on the detection signal from the detection pen 8. And y coordinate detection circuit 1
1 will be supplied. The x-coordinate detection circuit 10 and the y-coordinate detection circuit 11 output coordinate data having values different from the coordinates actually pointed by the tip of the detection pen 8.

A situation in which erroneous detection pulses in the states shown in (b) to (f) are output from the pulse conversion circuit 9 will be described. (B) shows a detection pulse 10 having a wider pulse width than the original detection pulse in addition to the detection pulse 101.
2 or narrow detection pulse 103 is detection pulse 101
Shows a state that occurs in a portion other than the timing at which the error occurs. (C) shows a state in which detection pulses 104 and 105 having a pulse width substantially equal to the pulse width W2 of the detection pulse 101 are generated at a portion other than the timing when the detection pulse 101 is generated due to superimposed noise. (D)
Either the detection pulse 101 coincides with the timing and noise is superimposed on the detection pulse 101, or only the detection pulse 101 is affected by the noise to form the detection pulse 106. In the case of (d), although the number of pulses does not increase or decrease as compared with the normal state, the rising and falling timings are shifted and the pulse width becomes the width W3.

FIG. 5E shows a state in which the detection signal that should have been obtained by the original scanning is canceled due to the superposition of noise, the pulse is not detected by the pulse conversion circuit 9, and there is no pulse during the coordinate detection period. . (F), the detection signal expected to be obtained by the original scanning is canceled by the superposition of the noise, and the detection signal having substantially the same pulse width as the original detection pulse at a timing different from the detection pulse 101 generated due to the noise. When the detection pulse 107 is detected by the pulse conversion circuit 9, the number of pulses does not increase or decrease.

A technique for preventing erroneous detection of coordinates in a device for detecting a coordinate position is disclosed in Japanese Patent Application Laid-Open No. 61-201321.
No. 6,086,045. The position detecting device includes a position detecting plate, a driving unit, a voltage detecting unit, a signal extracting unit, a data generating unit, and a data processing unit.
A plurality of strip conductors are arranged in parallel on the position detection plate at predetermined intervals, and the coordinate position on the surface of the position detection plate is indicated by voltage detection means. The driving unit performs a voltage supply operation of sequentially applying a predetermined voltage to the plurality of strip conductors for a predetermined short period every unit detection period. When the voltage detecting means is positioned on the position detecting plate, a detection output is generated in the voltage detecting means by the voltage applied to the strip conductor. From the detection output, a signal component of a predetermined frequency is extracted by a signal extracting unit.

[0024] The data generating section may determine whether the signal component has reached a predetermined voltage level from a reference time associated with the supply of voltage to the strip conductor, or again after a predetermined voltage level has been exceeded from the reference time. The data corresponding to the time required to cross the level is supplied to the data processing unit.

In the data processing section, the data supplied from the data generating section is fetched by the data fetching means as sequential coordinate data having a predetermined detection cycle, and two data indicated by the first and second coordinate data fetched continuously. The absolute value of the difference between the values is obtained by the coordinate difference calculating means, and whether the coordinate data is valid is determined by the coordinate data selecting means based on the absolute value, and the position detection output based on the valid coordinate data is determined. Send out.

In the coordinate data selection means, the first and second
In the period corresponding to the detection cycle when the coordinate data is captured, the reference data determined according to the maximum distance that the voltage detection means moves on the position detection plate is compared with the absolute value, and When the value is below the reference data, the first
At least one of the coordinate data and the second coordinate data is regarded as valid coordinate data.

Since the coordinates other than the coordinates at which the voltage detecting means is considered to be movable are not output as position detection outputs,
It is possible to prevent display at undesired coordinates due to noise or the like.

A technique for preventing erroneous detection of coordinates in a coordinate-integrated tablet device is disclosed in JP-A-6-295219.
No. 6,086,045. Since the coordinate-integrated tablet device disclosed in the above publication has a configuration similar to that of the display-integrated tablet device shown in FIG. 12, the description will be made using the reference numerals of the corresponding components.

The number of times that the output signal output from the detection pen 8 exceeds the threshold voltage during the coordinate detection period is counted by the counting means, and the counted number is compared with the number of scans of the electrode group during the coordinate detection period. Is larger than the number of scans, the coordinate detection circuits 10 and 11 in the coordinate detection period.
The erroneous detection determining means determines that the erroneously detected coordinates are included in the coordinates detected in step (1).

[0030]

In recent personal computers, the resolution of a display device has been improved, and an SVGA (Super Video Graphimeter) using a cathode ray tube (CRT) has been developed.
c Array) and XGA (eXtended Video Graphic Array)
High-resolution display based on a standard referred to as such is performed. Similarly, the resolution of a personal computer equipped with a liquid crystal panel is also increasing, and in order to perform high-resolution display, for example, in a duty-type liquid crystal panel 1, the pitch of each electrode is formed to be narrow. Also in the active matrix type liquid crystal panel 21, in order to secure the aperture ratio of the pixel electrode,
The electrode widths of the source bus line electrode and the gate bus line electrode are formed to be small.

Further, in order to reduce power consumption in the device, there is a tendency to lower the voltage for driving the liquid crystal, and the voltage applied to the electrodes for detecting the coordinates is also set lower. As the voltage applied to the electrode decreases, the voltage induced on the detection electrode also decreases, making it difficult to detect the coordinates indicated by the detection pen 8.

In the position detecting device disclosed in Japanese Patent Application Laid-Open No. 61-201321, an error in the erroneous detection determination corresponding to the maximum movement distance of the voltage detecting means with respect to the detection cycle remains. If the reference value is reduced, the speed at which characters and graphics are written is limited, and if the input is performed at a speed exceeding this speed, an erroneous determination is made that false detection has occurred. There is.

In the display-integrated tablet device disclosed in JP-A-6-295219, coordinates are generated by noise such as noise caused by friction between the protective plate of the liquid crystal panel and the resin portion at the tip of the detection pen 8, high-frequency noise, and power supply noise. There is a problem that detection becomes inaccurate. Also,
The x and y coordinates are detected once in one frame period, and there is a possibility that erroneous detection may be performed due to each noise.

An object of the present invention is to provide a tablet device capable of preventing erroneous detection due to mixing of erroneous signals or erroneous operation and performing stable and accurate coordinate detection.

[0035]

SUMMARY OF THE INVENTION According to the present invention, a surface position of a tablet on which a first electrode extending in a first direction and a second electrode extending in a second direction intersecting the first direction are arranged is set to the first position.
By electrically scanning the electrode and the second electrode sequentially with a pulse signal and instructing the coordinate detection electrode electrostatically coupleable with the first electrode and the second electrode by a detection means provided at the tip, In a tablet device for detecting as coordinates based on a signal induced in a detected coordinate, a pulse width detecting means for detecting a pulse width of a signal induced in a coordinate detecting electrode, and a pulse width detected by the pulse width detecting means. A tablet device comprising: an erroneous detection determination unit that compares the pulse width with a set reference pulse width and determines that erroneous detection is performed when a difference between the pulse widths is outside a predetermined allowable range. According to the present invention, when the tablet means is pointed to by the detecting means, the coordinate detecting electrodes of the detecting means and the first and second electrodes are electrostatically driven by the pulse signals sequentially applied to the first and second electrodes. The signals are induced by the combination, and the coordinates are detected based on the induced signals. The pulse width of the signal induced in the coordinate detection electrode is detected by pulse width detection means. The erroneous detection determination means compares the detected pulse width with a predetermined pulse width, and determines that the detected coordinates are erroneously detected if the difference between the pulse widths is outside a predetermined allowable range. Therefore, it is possible to determine whether or not the detected signal is erroneous detection based on the pulse width of the detected signal which is likely to change due to the influence of noise or the like, and to determine whether or not the detection signal is erroneously detected. it can.

Further, according to the present invention, the surface position of a tablet on which a first electrode extending in a first direction and a second electrode extending in a second direction intersecting with the first direction are arranged is determined by the first electrode and the second electrode. Are sequentially electrically scanned by a pulse signal,
By instructing a coordinate detection electrode that can be electrostatically coupled to the first electrode and the second electrode with a detection unit provided at the tip,
In a tablet device that detects as coordinates based on a signal induced in the detected coordinates, storage means for storing the coordinates detected by the coordinate detection means, and based on a plurality of consecutive coordinates stored in the storage means, Coordinate prediction means for predicting the coordinates of the surface position of the tablet specified by the detection means, and prediction error estimation for estimating, as a prediction error, a coordinate error predicted by the coordinate prediction means with respect to the coordinates stored in the storage means Means, a coordinate error detected by the coordinate detecting means with respect to the coordinates predicted by the coordinate predicting means, and a prediction error by the prediction error estimating means are compared, and when the comparison result is outside a predetermined allowable range. Erroneous detection determining means for determining erroneous detection, wherein the prediction error estimating means increases the distance between the coordinates stored in the storage means. It is a tablet and wherein the increasing the value of the prediction error with the. According to the present invention, when the tablet surface is pointed by the detecting means, the coordinate detecting electrodes of the detecting means and the first and second electrodes are statically moved by the pulse signals sequentially applied to the first electrode and the second electrode. A signal is induced by being electrically coupled, and coordinates are detected based on the induced signal. The detected coordinates are stored in the storage unit. The coordinate predicting unit predicts a surface position of the tablet specified by the detecting unit based on coordinates detected a plurality of times in succession. The prediction error estimation unit estimates a coordinate error predicted by the coordinate prediction unit as a prediction error. This prediction error is estimated to increase as the distance between the coordinates stored in the storage unit increases. The erroneous detection determination unit obtains an error between the coordinates detected based on the coordinates detected by the coordinate detection unit and the coordinates predicted by the coordinate prediction unit, and the obtained error and the error estimated by the prediction error estimation unit. A comparison is made with the prediction error, and it is determined whether or not the detected coordinates are erroneous based on the comparison result. Therefore, based on the history of the movement of the detecting means, it is determined whether or not the detected coordinates are actually deviated from the coordinates indicated by the detecting means, and it is determined whether or not the detected coordinates are erroneously detected. Can be determined. Further, when the detection means moves at high speed, such as when a relatively rough figure or character is drawn, a large prediction error is predicted, so that it is erroneously determined to be erroneous detection at high speed drawing. It can be prevented as much as possible.

[0037]

According to the present invention, the surface position of a tablet on which a first electrode extending in a first direction and a second electrode extending in a second direction intersecting with the first direction are arranged is determined by the first electrode and the second electrode. Are sequentially electrically scanned by a pulse signal,
By instructing a coordinate detection electrode that can be electrostatically coupled to the first electrode and the second electrode with a detection unit provided at the tip,
In a tablet device for detecting as coordinates based on a signal induced in detected coordinates, a scanning pulse generating means for continuously applying a plurality of scanning pulse signals to a first electrode and a second electrode, respectively, Comparing the pulse interval calculated by the pulse interval calculating means with a pulse interval calculating means for calculating the pulse interval of the signal induced on the coordinate detection electrode by a plurality of scanning pulses given by the means, An erroneous detection determination unit that determines erroneous detection when the pulse interval is out of a predetermined range. According to the present invention, when the tablet surface is designated by the detecting means, the coordinate detecting electrodes of the detecting means are supplied by a plurality of scanning pulse signals sequentially supplied from the scanning pulse generating means to the first electrode and the second electrode. And the first and second electrodes are electrostatically coupled to induce a signal, and the coordinates are detected based on the induced signal. The pulse interval calculation means calculates and calculates the pulse interval of the signals based on the plurality of signals induced by applying the plurality of scanning pulse signals to the electrodes. The erroneous detection determination means compares the pulse interval obtained by the calculation with a predetermined comparison criterion, and determines that the detected coordinates are erroneously detected if the pulse interval is outside a predetermined allowable range. Therefore, for example, when signal detection is not performed normally due to the influence of noise or the like, the pulse interval falls outside the predetermined range of the comparison reference, and the pulse of the signal generated by applying a plurality of scanning pulses is generated. Is prepared in advance as a comparison standard, it is possible to determine whether the detected coordinates are actually shifted from the coordinates indicated by the detecting means, and whether the detected coordinates are erroneously detected. Can be determined with high accuracy.

According to the present invention, the surface position of a tablet on which a first electrode extending in a first direction and a second electrode extending in a second direction intersecting with the first direction are arranged is determined by the first electrode and the second electrode. Are sequentially electrically scanned by a pulse signal,
By instructing a coordinate detection electrode that can be electrostatically coupled to the first electrode and the second electrode with a detection unit provided at the tip,
In a tablet device for detecting as coordinates based on a signal induced at a detected coordinate, a scanning pulse signal applied to a first electrode and a second electrode is supplied to an induced voltage from a coordinate detecting electrode at both a rising portion and a falling portion. Scanning pulse generating means for generating a pulse width which can be detected as a change in the pulse width, and pulse interval calculating means for performing an operation for obtaining a pulse interval of a signal induced on a coordinate detection electrode by a scanning pulse given from the scanning pulse generating means And comparing the pulse interval calculated by the pulse interval calculation means with a predetermined comparison reference, and when the pulse interval is out of a predetermined range, including an erroneous detection determination means for determining erroneous detection, wherein the pulse interval calculation means Is a pulse of a signal induced by the coordinate detection electrode at a rising portion and a falling portion of the scanning pulse, respectively. Interval is a tablet and wherein the determining the. According to the present invention, the scanning pulse generating means generates a scanning pulse signal having a pulse width capable of detecting a change in the induced voltage in the coordinate detection electrode at both the rising portion and the falling portion. When the tablet surface is designated by the detecting means, the coordinate detecting electrodes of the detecting means, the first and second electrodes, and the coordinate detecting electrodes of the detecting means are supplied to the first electrode and the second electrode by a scanning pulse signal sequentially given from the scanning pulse generating means. Are electrostatically coupled to induce a signal, and the coordinates are detected based on the induced signal. Further, the pulse interval calculating means calculates the pulse interval of the signal based on two signals induced on the coordinate detection electrode at the rising portion and the falling portion of the scanning pulse. The erroneous detection determination means compares the pulse interval obtained by the calculation with a predetermined comparison criterion, and determines that the detected coordinates are erroneously detected if the pulse interval is outside a predetermined allowable range. Therefore, for example, when the signal is not normally detected due to the influence of noise or the like, the interval between the pulses is out of the predetermined range of the comparison standard, and two pulses induced at the rising portion and the falling portion of the scanning pulse. By preparing the pulse interval of the signal as a comparison reference in advance, it can be determined whether or not the detected coordinates are actually shifted from the coordinates indicated by the detecting means. Whether or not there is can be determined with high accuracy.

Further, according to the present invention, the first and second electrodes are electrodes for indicating coordinates, and are electrodes for display of an image display panel having intersections as pixels. It is characterized by including a display / coordinate detection switching means for switching in a time-division manner whether or not to perform. According to the present invention,
The detection of the coordinates, which is the surface position of the tablet, and the display of an image that pixels the intersection of the first and second electrodes arranged on the tablet are performed by time division control by the display / coordinate detection switching means. Therefore, a device that displays coordinates specified on the tablet by using the detecting means with the same feeling as writing a character or the like on paper with a writing instrument, for example, a device that displays handwritten characters written by the detecting means in a tablet It can be realized by sharing the electrodes indicating the coordinates and the electrodes for displaying the image display panel, and controlling the display and the coordinate detection in a time-division manner, and by stacking the tablet device and the display device. The visibility of the display screen can be improved as compared with the case where the display screen is provided.

[0041]

FIG. 1 is a block diagram showing a configuration of a display-integrated tablet device 30 according to a first embodiment of the present invention. The display-integrated tablet device 30 includes a liquid crystal panel 31, a common electrode drive circuit 32, a segment electrode drive circuit 33, a switching circuit 34, a display control circuit 35, a detection control circuit 36, a control circuit 37, Pen 38, pulse conversion circuit 39, x-coordinate detection circuit 4
0, a y-coordinate detection circuit 41, a DC power supply circuit 42, and an erroneous detection determination circuit 43. A feature of the display-integrated tablet device 30 is that it is different from the conventional display-integrated tablet device in that the detection signal for finding the coordinates on the liquid crystal panel 31 indicated by the detection pen 38 is erroneously detected. The erroneous detection determination circuit 43 is provided.

The liquid crystal panel 31 includes n common electrodes Y1 to Yn (referred to as a reference Y when collectively referred to) and m segment electrodes X1 to Xm (referred to as reference when referred to collectively). X is used) and a liquid crystal is interposed therebetween. In the liquid crystal panel 31, a region where each common electrode Y and each segment electrode X intersect is a pixel, and n × m pixels are arranged in a matrix. The common drive circuit 32 and the segment drive circuit 33 selectively apply the voltage supplied from the DC power supply circuit 42 to each of the electrodes X and Y.

1 in the display-integrated tablet device 30
The frame period includes a display period and a coordinate detection period, similarly to the display-integrated tablet device of the related art. In the display period, display data supplied from an external device (not shown) and display signals output from the display control circuit 35 are selected by the switching circuit 34 and supplied to the common drive circuit 32 and the segment drive circuit 33. The common electrode drive circuit 32 applies a drive pulse of a common electrode drive signal to the common electrode Y, and the segment electrode drive circuit 33 applies a drive pulse of the segment electrode drive signal to the segment electrode X.

In the coordinate detection period, each detection control signal output from the detection control circuit 36 is selected by the switching circuit 34 and supplied to the common drive circuit 32 and the segment drive circuit 33. The coordinate detection period includes an x coordinate detection period and a y coordinate detection period. During the x coordinate detection period, the electrode scanning signal is sequentially applied from the segment electrode driving circuit 33 to the segment electrode X, and during the y coordinate detection period, the electrode scanning signal is sequentially applied from the common electrode driving circuit 32 to the common electrode Y. . The switching circuit 34, the display control circuit 35, and the detection control circuit 36 constitute display / coordinate detection switching means.

FIG. 2 is a sectional view of the detection pen 38 and the liquid crystal panel 31. The liquid crystal panel 31 includes, for example, a panel portion 54 formed by sandwiching a liquid crystal layer with a light-transmitting substrate, a sealing member 55 provided around the panel portion 54, and a panel portion formed by the sealing member 55. 54
And a protection plate 56 for protecting the panel portion 54. A detection electrode 57 is provided at the tip of the detection pen 38, and a tip resin 58 is formed so as to cover the detection electrode 57. Each substrate of the liquid crystal panel 31 is provided with electrodes X and Y, respectively.

A voltage generated by electrostatic induction between each of the electrodes X and Y of the panel portion 54 and the detection electrode 57 is supplied from the detection electrode 57 to the pulse conversion circuit 39, and further to each of the coordinate detection circuits 40 and 41. By being given, the coordinates indicated by the detection pen 38 are detected.

FIG. 3 shows the configuration of the x-coordinate detection circuit 40 in the display-integrated tablet device 30. FIG. 4 is a timing chart of each signal in the x-coordinate detection circuit 40. Since the x and y coordinate detection circuits 40 and 41 have the same configuration, the following description will be made using the x coordinate detection circuit 40.
In the present embodiment, the x-coordinate detection circuit 40 and the y-coordinate detection circuit 41 are both provided.
Since the coordinate detection period and the y-coordinate detection period are provided independently of each other, one of the coordinate detection circuits may be provided, and the coordinate detection may be performed by switching in a time-division manner.

The x coordinate detecting circuit 40 includes a coordinate counting circuit 45, a detection pulse latch circuit 46, a falling latch circuit 47, a rising latch circuit 48, an average value calculating circuit 49, and inverter circuits NT1 and NT2. It is comprised including. The coordinate count circuit 45 receives the x coordinate detection period signal XDET supplied from the control circuit 37 at the terminal CLR.
, And an x-coordinate count clock CLC having a shorter cycle than the scan clock CLD for scanning the segment electrode X is input to the terminal CK. The coordinate counting circuit 45 performs a count-up operation in response to the rise of the x-coordinate counting clock CLC during the period in which the x-coordinate detection period signal XDET is at a high level, and counts when the x-coordinate detection period signal XDET goes to a low level. Clear the value. Therefore, the count of the x-coordinate counting clock CLC is counted as time elapses from the start of the coordinate detection scan corresponding to the start of the detection scan.

In this embodiment, the frequency of the count clock CLC divided by 4 is used as the scan clock CLD, and the coordinates are detected by counting the electrodes with a four-fold clock. Therefore, it is possible to perform detection with an accuracy higher than the electrode pitch.

The detection pulse latch circuit 46 latches the detection pulse Xout output from the pulse conversion circuit 39 at the falling edge of the x-coordinate counting clock CLC during the period when the x-coordinate detection period signal XDET is at the high level. As a result, an x-coordinate count data latch signal XoutLT synchronized with the counting operation of the coordinate count circuit 45 is output to the rising latch circuit 48, the inverting circuit NT2, and the erroneous detection determination circuit 43.

Next, the falling latch circuit 47 and the rising latch circuit 48 count the count value Count of the coordinate counting circuit 45 with the x-coordinate count data latch signal X.
At the time t1 when outLT rises and at the time t2 when its inverted signal rises, it is latched and output to the average value calculation circuit 49 and the erroneous detection determination circuit 43 as X detection pulse rising data XdataP and X detection pulse falling data XdataN. .

The average value calculating circuit 49 calculates the average of the count values indicated by the X detection pulse falling data XdataN and the X detection pulse rising data XdataP, thereby corresponding to the coordinates indicated by the tip electrode 57 of the detection pen 38. The count value of the coordinate counting circuit 45 at the timing corresponding to the central portion of the detection pulse Xout, that is, the peak portion of the signal detected by the detection pen 38 is obtained, and the coordinate data indicated by the detection pen 38 is obtained.

The operation of the X-coordinate detection circuit 40 when the detection pulses shown in FIGS. 17B to 17F are given will be described below. First, when the detection pulses shown in (b) and (c) are given, the falling latch circuit 47 and the rising latch circuit 4 each time a pulse appears in the detection signal.
8, the count value of the coordinate count circuit 45 is latched,
Eventually, the count value Count corresponding to the detection pulse that appears at the end of the period when the x-coordinate detection period signal XDET is at the high level is output as the coordinate data. Next, when the detection pulses shown in (d) and (f) are given, the count data latched by the falling latch circuit 47 and the rising latch circuit 48 deviates from the count data indicated by the normal detection pulse. The detected pulse average data output from the average value calculating circuit 49 is shifted from the coordinates indicated by the detection pen 38.

When the detection pulse shown in (e) is given,
Since no data is latched by the falling latch circuit 47 and the rising latch circuit 48 in the coordinate detection period, the data latched in the previous detection period is held. When the latch circuits 47 and 48 are independently provided for x-coordinate detection, the coordinate data detected in the previous detection period is output, so that the movement amount during the detection period indicates the deviation of the detected coordinates. Becomes If each of the latch circuits 47 and 48 is used for both x-coordinate detection and y-coordinate detection, completely different data will be output as detection data, resulting in a large shift.

FIG. 5 is a block diagram showing the configuration of the erroneous detection determination circuit 43. The erroneous detection determination circuit 43 includes a pulse width calculation circuit 51, a reference pulse width output circuit 52, and a pulse width comparison circuit 53. The pulse width calculation circuit 51 obtains the pulse width of the detection pulse by subtracting the corresponding detection pulse rising data from the x / y detection pulse falling data. Therefore, the pulse width calculation circuit 51 can be constituted by a simple difference circuit. The pulse width obtained by the pulse width calculation circuit 51 is
Even when the detection is normally performed, a slight change may occur depending on the coordinate position indicated by the detection pen 8.

In the reference pulse width output circuit 52, reference pulse width data corresponding to coordinates is stored in a memory in advance, and the reference pulse width data is converted into a pulse width comparison circuit 53 according to the input x / y detection pulse average data. Is output to The pulse width comparison circuit 53, which is an erroneous detection determination unit, compares the output of the pulse width calculation circuit 51 with the output of the reference pulse width output circuit 52, and determines whether or not the detected pulse is abnormal.
If it is determined to be abnormal, an erroneous detection determination signal is output. Based on the erroneous detection determination signal, whether or not to perform display based on each coordinate data is determined by a control device (not shown), so that display at an undesired position due to the influence of noise or the like can be prevented.

In the erroneous detection determination circuit 43, it is premised that the detected pulse width is different from the pulse width detected in a normal state in order to determine erroneous detection. Of the detection pulses shown in FIG.
The detection pulses 102, 103,
When given 106, it can be determined whether or not an erroneous detection has been made.

Generally, in the case of a malfunction due to the discharge of the electric charge charged by friction, the signal induced in the detection pen 38 has a very large output compared to the signal detected in a normal state. In many cases, the pulse width of the detection pulse also becomes extremely large. Therefore, by determining whether the detection is normal or erroneous based on the pulse width, it is possible to reliably determine whether the detected coordinates are the coordinates indicated by the detection pen 38 or erroneous detection. be able to.

As described above, the erroneous detection determination circuit 43 in the present embodiment is configured to detect the number of detected pulses during the coordinate detection period when the detected pulse as shown in FIG. When there is no change in, the erroneous detection can be detected based on the width of the detection pulse. Further, in the case of detecting the erroneous detection by estimating the movable range of the conventional detection pen 8, there is a trade-off between the criterion of the erroneous detection determination and the speed of moving the detection pen 8. Since the erroneous detection determination circuit 43 detects the occurrence of erroneous detection by evaluating the detection pulse during the detection period, erroneous detection can be performed regardless of the speed at which the detection pen 38 is moved.

Further, since the reference pulse width is stored in the memory of the reference pulse width output circuit 52 in association with the coordinates, a change in the pulse width of the detection pulse due to the coordinates indicated by the detection pen 38 is obtained. Can be dealt with, and erroneous detection can be determined more strictly.

If the change in the pulse width of the detection pulse due to the coordinates indicated by the detection pen 38 can be approximated as a relatively simple linear function, the reference pulse width output circuit 5
2 is not configured to include a memory, but a simple configuration in which the correspondence between the coordinates and the pulse width is formulated to form a logic circuit, and the pulse width is obtained and output by the logic circuit based on the input coordinates. It is also possible to use

Further, the configuration of the reference pulse width output circuit 52 can be simplified by changing the pulse width and outputting the pulse width every x / y coordinate detection period. Furthermore, the configuration of outputting the single fixed reference pulse width data in the x, y coordinate detection period can further simplify the configuration of the reference pulse width output circuit 52. Even with a simple configuration with a small number of output pulse widths, the pulse width of the detection pulse in the case of erroneous detection is sufficiently large compared to the pulse width of the detection pulse in a normal state, so that erroneous detection is ensured. It can be performed.

FIG. 6 is a block diagram showing the configuration of the erroneous detection determination circuit 60 in the display-integrated tablet device 30a according to the second embodiment of the present invention. The display-integrated tablet device 30a has a configuration in which the erroneous detection determination circuit 43 of the display-integrated tablet device 30 is replaced by an erroneous detection determination circuit 60. Therefore, the other components will be described using the same reference numerals. I do.

The erroneous detection determination circuit 60 includes a detection data storage circuit 61, a detection coordinate prediction circuit 62, a prediction error estimation circuit 63, and a distance comparison circuit 64. The detection data storage circuit 61 stores the x / y detection pulse average data detected by the x coordinate detection circuit 40 and the y coordinate detection circuit 41 during the coordinate detection period as coordinates on the liquid crystal panel 31 indicated by the detection pen 38, respectively. Is stored for the number of times of detection.

Using the detection result stored in the detection data storage circuit 61, the detection data before and after the data output as x / y detection coordinate data is used to determine the data actually detected in the detection coordinate prediction circuit 62. Separately, prediction is performed on the coordinate data indicated by the detection pen 38 at that timing based on the coordinate data detected before and after that, and the prediction is output to the prediction error estimation circuit 63 and the distance comparison circuit 64 as prediction coordinate data. Prediction error estimation circuit 63
Calculates and outputs an error range based on the detected data and the predicted coordinate data.

The detected coordinate predicting circuit 62 uses the coordinate data detected in the detection period before and after the coordinate to be predicted and performs linear interpolation to obtain the predicted coordinate data. In the erroneous detection determination circuit 60, the detection data storage circuit 61
Since the detection coordinate prediction circuit 62 predicts the coordinates based on the detection data stored in the detection pen 38, it is more erroneous than the case where the movable distance of the detection pen 38 is simply predicted based on the coordinates detected earlier. It is possible to reliably determine whether or not detection has been performed.

In the distance comparison circuit 64, which is an erroneous detection determination means, the absolute value of the distance between the predicted coordinate data from the detected coordinate prediction circuit 62 and the detected coordinate data output from the detected data storage circuit 61 as the prediction target is calculated. The value is obtained, and the absolute value is compared with the error range output from the prediction error estimation circuit 63. When the absolute value is within the range of the prediction error, the distance comparison circuit 64 determines that the detection has been performed in a normal state, and when the absolute value is outside the range of the prediction error, erroneous detection is performed due to some abnormality. It is determined that an error has occurred, and the determination result is output as an erroneous detection determination signal.

It is conceivable that the prediction error is caused by the detection accuracy and by the movement of the detection pen 38.
The prediction error accompanying the detection accuracy is as follows.
This is related to the fact that there is a difference between the regions of the display surface in. This detection accuracy can be obtained by actually measuring. A table is created based on the measured data, stored in the prediction error estimating circuit 63, and the measured data is compared based on the input coordinate data. The reference value is given to the distance comparison circuit 64.

In general, in a display-integrated tablet device, the coordinate detection cycle of the detection pen is determined by the frame frequency of the display. It is also conceivable that the possible amount of movement of the detection pen is not always sufficient as a criterion for erroneous detection with respect to the accuracy of a figure or character input by the detection pen.

However, the detection coordinate predicting circuit 62 in the display-integrated tablet device 30a of the present embodiment, when the detection pen 38 moves at a high speed, such as when a relatively rough figure or character is drawn, By estimating that the prediction error becomes large, it is possible to extremely reduce the risk of erroneously determining high-speed drawing as erroneous detection.

The movement of the detection pen 38 is relatively slow and complicated when a fine figure or character is input or near the drawing start and stop points. Is required. In such a situation, similarly high accuracy is required for the detection of erroneous detection. However, in such a situation, the density of detected coordinates is high, so that the accuracy of prediction in the detected coordinate prediction circuit 62 is high. Become. Further, since the movement distance of the detection pen 38 is small before and after the detection pen 38, the prediction error can be predicted to be small, and the occurrence of erroneous detection of a small distance can be detected. Erroneous detection can be determined according to

As described above, according to the present embodiment, the erroneous detection determination circuit 60 can determine erroneous detection when all the detection pulses shown in FIG. In contrast to the determination, since the determination regarding the deviation of the detected coordinates based on the movement history of the detection pen 38 is performed, it is possible to detect the erroneous detection with higher accuracy.

The provision of the prediction error estimating circuit 63 allows the detection pen 38 to move in accordance with the moving speed.
In a portion where a relatively rough figure or the like is input, an area determined to be normally detected based on a large movement amount of the detection pen 38 is set as a large range.
The degree of freedom with respect to the moving speed can be ensured, and in a portion where a fine character or the like is input, erroneous detection can be determined in a narrow range corresponding to the input. Can be realized.

Further, an erroneous detection determination signal is output to an external circuit and supplied to a detection coordinate prediction circuit 62. If it is determined that no erroneous detection has occurred, the coordinate data from the detection data storage circuit 61 is replaced by x. The coordinate data may be output as / y detection coordinate data, and when it is determined that the detection is erroneous, the predicted coordinate data may be output. By providing an erroneous detection determination signal to the detection coordinate prediction circuit 62, if erroneous detection does not result in accurate detection of the coordinates, the predicted coordinates are output. Thus, data indicating the coordinates can be always output, and the detected coordinates can be prevented from being interrupted.

As a prediction method used in the detection coordinate prediction circuit 62, in addition to the above-described method, the respective moving directions are obtained by using the two points before and after, and the intersection of the extension line between the two points is calculated as the predicted coordinate. It may be data. Further, prediction may be performed from a plurality of detection points using a curvilinear approximation technique. In the display-integrated tablet device 30a, the detection coordinate prediction circuit 62 can be configured with a necessary and sufficient circuit scale by employing an optimal prediction method based on the relationship between the detection cycle and the required detection accuracy.

FIG. 7 shows a configuration of an erroneous detection determination circuit 70 in a display-integrated tablet device 30b according to a third embodiment of the present invention, and FIG.
It is a timing chart in 0b. In the display-integrated tablet device 30b, the same components as those in the display-integrated tablet device 30 are denoted by the same reference numerals, and description thereof will be omitted.

The features of the display-integrated tablet device 30b are that the erroneous detection determination circuit 43 in the display-integrated tablet device 30 is replaced by an erroneous detection determination circuit 70, and that the x-coordinate detection period and the y-coordinate That is, the detection period is provided a plurality of times.

In the conventional display-integrated tablet device, in the time division operation of the display period and the coordinate detection period, the x-coordinate detection period and the y-coordinate detection period are each performed once in the detection period within one frame cycle of display. Is provided only for each. In the display integrated tablet device 30b according to the present embodiment, the detection control circuit 36a and the control circuit 3
7a, the first and second x-coordinate detection periods T are added to the coordinate detection period T22 in the N-th frame period T20.
23, T24 and a y-coordinate detection period T25 are performed. Note that each coordinate detection period is 2 in the frame period T20.
It may be configured to be provided a plurality of times or more. Further, any of the coordinate detections may be performed in the frame period T20 before the display period T21.

The erroneous detection determination circuit 70 includes a detection data storage circuit 71, a coordinate data calculation circuit 72, a comparison reference generation circuit 73, and a detection data comparison circuit 74. The detection data storage circuit 71 includes an x-coordinate detection circuit 40.
And x / y detection pulse average data output from the y coordinate detection circuit 41. As for the x-coordinate, the results of the two coordinate detections are stored. The detection data storage circuit 71 outputs data to the coordinate data calculation circuit 72 and the detection data comparison circuit 74.

In the coordinate data calculation circuit 72, the detection is performed in the first x coordinate detection period T 23 and the second x coordinate detection period T 24 and stored in the detection data storage circuit 71.
An average of the two x-coordinate data is obtained, and the calculation result is output as x-detection coordinate data. The y coordinate detection data is output as it is. The x / y detection coordinate data is also supplied to the comparison reference generation circuit 73.

The comparison reference generating circuit 73 is provided with a memory for storing the detection accuracy for the coordinates detected for each area on the liquid crystal panel 31, for example.
Is output to the detection data comparison circuit 74 as a comparison criterion, based on the detection accuracy in the area including the coordinates indicated by the first detection data and the second detection data.

In the detection data comparison circuit 74 which is an erroneous detection determination means, the first data output from the detection data storage circuit 71
The absolute value of the difference between the x-detected pulse average data detected in the x-coordinate detection period and the second x-coordinate detection period is obtained. If this absolute value is smaller than the comparison reference value supplied from the comparison reference generation circuit 73, It is assumed that the detection has been performed in a normal state, and if it is larger, it is determined that an erroneous detection has occurred, and an erroneous detection determination signal is output.

The first x-coordinate detection period and the second x-coordinate detection period are very close in terms of time with respect to the display period, so that the movement of the detection pen 38 during that period is almost ignored. In a case where it is necessary to detect an erroneous detection within the allowable range, the comparison reference generating circuit 73 stores the previously detected coordinate data in the same manner as in the second embodiment. In advance, the detection pen 38 is set based on the coordinate data.
Is calculated, and when it is determined that the detection pen 38 is moving at a high speed in accordance with the moving distance, the comparison standard is set to be gradual. Conversely, when the detection pen 38 is moving at a low speed, the comparison standard is used. By generating a comparison reference in accordance with the situation, such as by setting a stricter condition, it is possible to prevent erroneous detection more than necessary and to perform erroneous detection reliably.

As described above, according to the present embodiment, the erroneous detection determination circuit 70 performs the detection scan continuously during the same detection period, so that the movement of the detection pen 38 during the continuous detection period is extremely small. The occurrence of erroneous detection can be detected with extremely high accuracy as compared with the conventional display-integrated tablet device in which the next detection period passes through a display period that is extremely long from the detection period.

Further, in the conventional display-integrated tablet device, since the voltage level of the signal induced from the segment electrode X, which is located on the lower side when the detecting pen 8 is approached, is extremely small, the segment electrode X is Although the problem arises that the detection accuracy of the coordinate data obtained by scanning is lower than the detection accuracy of the coordinate data obtained by scanning the common electrode Y,
By adopting a configuration such as the erroneous detection determination circuit 70 that obtains coordinate data based on detection data obtained by a plurality of scans, detection accuracy can be improved.

In this embodiment, since the y-coordinate detection period included in one frame period is set to one time, the average y-detection pulse data is output as the y-coordinate data.
The detection may be performed a plurality of times in the same manner as in the x-coordinate detection period. When detecting the y coordinate a plurality of times, an average value is obtained and output based on the data in the detection data storage circuit 71.

FIG. 9 shows a configuration of an erroneous detection determination circuit 80 in a display-integrated tablet device 30c according to a fourth embodiment of the present invention. FIG. 10 is a timing chart of each signal in the display-integrated tablet device 30c. is there.

A feature of the display-integrated tablet device 30c according to the present embodiment is that the conventional display-integrated tablet device basically includes a liquid crystal indicated by the detection pen by applying a single scanning pulse to each scanning electrode. Although the coordinates on the panel are detected, the detection control circuit 36b and the control circuit 37b use a detection signal D including a plurality of scanning pulses.
X and DY are created, and signals DX and DY are applied to each electrode to detect the coordinates on the liquid crystal panel 31 indicated by the detection pen 38. In the display-integrated tablet device 30c, two detected pulse average data are detected based on the two detected pulses.

In the x coordinate detection period T32 in the coordinate detection period T31, the segment electrode scanning signals DX1 to DXm
Are sequentially applied to the segment electrode X, and the common electrode scanning signals DY1 to DYn are applied to the common electrode Y in the y coordinate detection period T33.

Scanning signal D for detection applied to each electrode
X and DY are detected by the detection pen 38 and are converted into pulse signals as detection pulses in the pulse conversion circuit 39 to such an extent that two detection pulses are not detected as a single pulse. A plurality of scan pulses are included at a sufficient interval.

Further, by using a plurality of scanning pulses, the x-coordinate detection period T32 and the y-coordinate detection period T33 are lengthened, and the coordinate detection period T31 needs to be lengthened as a whole. As compared with the case where a plurality of detection periods are provided as shown in (1), it is possible to make the detection period slightly longer, and it is possible to suppress the extension of the detection period.

The erroneous detection determination circuit 80 includes a detection data storage circuit 81, a pulse interval calculation circuit 82, a comparison reference generation circuit 83, a pulse interval comparison circuit 84, and a coordinate data calculation circuit 85. . Detection data storage circuit 8
1 includes an x-coordinate detection circuit 40 and a y-coordinate detection circuit 41
The x / y detection pulse average data output from is stored as first detection pulse data and second detection pulse data. The stored detection pulse data is output to the pulse interval calculation circuit 82 and the coordinate data calculation circuit 85.

The pulse interval calculation circuit 82 obtains an interval between the first detection pulse and the second detection pulse by subtracting the first detection pulse data from the second detection pulse data, and outputs it to the pulse interval comparison circuit 84. The coordinate data operation circuit 85 is obtained by applying a plurality of scanning pulses, and is based on the plurality of data stored in the detection data storage circuit 81, on the liquid crystal panel 31 indicated by the tip of the detection pen 38. Is calculated. Coordinate data calculation circuit 8
5 calculates coordinate data from each of the plurality of detection data,
The coordinates are obtained by averaging the two sets of coordinate data.

When the pulse interval calculated by the pulse interval calculation circuit 82 is detected in a normal state, the pulse interval is equal to the interval at which the scanning pulse is output, but depends on the coordinate position on the liquid crystal panel 31. A slight difference in detection accuracy may occur. Comparison reference generation circuit 8
3 outputs the comparison reference data of the pulse interval to the pulse interval comparison circuit 84 according to the output of the coordinate data calculation circuit 85. Pulse interval comparison circuit 8 serving as erroneous detection determination means
In 4, when the relationship between the first detection pulse and the second detection pulse is within a predetermined range output from the comparison reference generation circuit 83, it is determined that detection in a normal state has been performed. On the other hand, if it is out of the range, it is determined that some erroneous detection has occurred, and the determination result is output as an erroneous detection determination signal.

As described above, according to the present embodiment, the signal for detection applied to each electrode during the coordinate detection period is a signal including a plurality of scanning pulses, so that two signals can be detected during one coordinate detection period. Since the detected pulse average data is obtained, the detected coordinate data is obtained based on the two detected pulse average data, and it is determined whether or not an erroneous detection has been performed. Therefore, the accuracy of detecting the coordinate data can be improved. .

Further, with respect to scanning by a plurality of pulses, the purpose is only to detect erroneous detection, and with respect to coordinate detection, data having the smallest change in detected coordinate value is selected from among a plurality of detected data, and the detection is performed. It may be configured to calculate coordinate data based on the data.

In the erroneous detection determination circuit 80, although the x / y detection pulse average data is input to the pulse interval calculation circuit 82, by adopting such a configuration, the stored detection data and the previous detection data can be used. By calculating the pulse interval from the detection data input as the x / y detection pulse average data, the configuration of the detection data storage circuit 81 is simplified. Further, when all the data are once stored in the detection data storage circuit 81 and then the pulse interval is obtained, there is no need to input the data.

FIG. 11 is a waveform diagram for explaining the operation of the pulse conversion circuit 39a in the display-integrated tablet device 30d according to the fifth embodiment of the present invention. In the display-integrated tablet device 30d, the same components as those in the display-integrated tablet device 30 are denoted by the same reference numerals, and description thereof is omitted. Since the erroneous detection determination circuit 90 has the same configuration as the erroneous detection determination circuit 80 shown in FIG. 9, the description will be made using the same reference numerals.

A feature of the display-integrated tablet device 30d is that scanning is performed with a scanning pulse having a wider pulse width W11 than the pulse width W1 of the scanning pulse in the conventional display-integrated tablet device.

The detection control circuit 16 in the conventional display-integrated tablet device is most suitable for detecting the signal induced by the detection pen 8 as a single pulse in the pulse conversion circuit 9 as shown in FIG. For example, the pulse width W
One scanning pulse is output. When a scanning pulse is applied to each electrode, a detection waveform as shown in FIG. 15 (2) is output from the detection pen 8, and this detection waveform is binarized in the pulse conversion circuit 9, and FIG. 15 (3) Are supplied to the x-coordinate detection circuit 10 and the y-coordinate detection circuit 11 as detection pulses shown in FIG.

The detection control circuit 36c in the present embodiment
Outputs a scanning pulse whose pulse width is W11 shown in FIG. 11A under the control of the control circuit 37c.
When the scanning pulse applied to each electrode of the liquid crystal panel 31 is detected by the tip electrode 57 of the detection pen 38, a signal is detected at the rising and falling timings of the scanning pulse, and the detection waveform shown in (2) is obtained. The signal is converted by the pulse conversion circuit 39
a.

The pulse conversion circuit 39a binarizes the applied signal with different signal levels, and converts it into a first detection pulse and a second detection pulse, for example, x
It is supplied to the coordinate detection circuit 40.

The erroneous detection determination circuit 90 detects whether detection has been performed in a normal state or an erroneous detection has occurred for some reason, based on the generation timing of the two pulses. In addition, the average of the rise and fall of each of the first detection pulse and the second detection pulse is obtained, and the average of both of them is obtained.
By obtaining the coordinate position on the liquid crystal panel 31 indicated by 8, the influence of noise from a power supply or the like can be reduced, and more accurate detected coordinates can be obtained.

Although the above embodiments have been described using the display-integrated tablet devices 30, 30a to 30d, a detection circuit in an electrostatic tablet device that does not include a display function is described. Similarly, it can be configured to detect occurrence of erroneous detection. Although the duty-type liquid crystal panel is used as the liquid crystal panel 31 in the display integrated tablet device 30, 30a to 30d, the liquid crystal panel 31 may be replaced with an active matrix type liquid crystal panel shown in FIG.

Although the erroneous detection determination circuits 43, 60, 70, 80, and 90 in the above embodiments have been described on the assumption that they are used independently of each other, when they are actually used, By appropriately combining the methods in the respective erroneous detection determination circuits, a more effective erroneous detection determination circuit can be configured.

In the erroneous detection determination circuits 43, 60, 70, 80, and 90 in each of the above-described embodiments, when the detection of the erroneous detection and the improvement of the detection accuracy can be simultaneously realized, both can be realized. However, it is possible to configure only one of the functions according to the situation, by removing unnecessary parts. The selection is appropriately made in consideration of the circuit scale and the like.

[0107]

As described above, according to the present invention, by comparing the pulse width of a detected signal with the pulse width of a predetermined reference pulse, it is determined whether the detected signal is erroneously detected. Is determined, it is possible to reliably determine whether or not an erroneous detection is made, and it is possible to prevent a malfunction or an undesired display based on a signal changed by the influence of noise or the like.

Further, according to the present invention, it is determined whether or not the detected coordinates actually deviate from the coordinates indicated by the detecting means based on the history of the movement of the detecting means. Erroneous detection can be determined in accordance with the above, preventing malfunction or undesired display from being performed,
And coordinate detection can be performed reliably. Further, when the detection means moves at high speed, such as when a relatively rough figure or character is drawn, a large prediction error is predicted, so that it is erroneously determined to be erroneous detection at high speed drawing. It can be prevented as much as possible.

[0109]

Further, according to the present invention, when the signal detection is not performed normally due to the influence of noise or the like, the interval between the pulses is out of the predetermined range of the comparison standard. By preparing a pulse interval of a signal generated by being applied as a comparison reference in advance, it can be determined whether or not the detected coordinates are actually shifted from the coordinates indicated by the detecting means. It can be determined with high accuracy whether or not the detected coordinates are erroneous detections.

Further, according to the present invention, when a signal is not normally detected due to, for example, the influence of noise or the like, the interval between the pulses is out of the predetermined range of the comparison standard, so that the rising edge of the scanning pulse is used. By preparing in advance the interval between the pulses of the two signals induced at the falling part as a comparison reference, it is possible to determine whether or not the detected coordinates actually deviate from the coordinates indicated by the detecting means. It is possible to determine with high accuracy whether or not the detected coordinates are erroneous detection.

Further, according to the present invention, since the intersection of the first and second electrodes arranged on the tablet is used as a pixel, display / coordinate detection switching means performs time division switching to perform coordinate detection and display. An electrode indicating coordinates on the tablet and an electrode for displaying the image display panel are shared, so that the tablet device and the display device can be integrally formed, and the tablet device and the display device are stacked. The visibility of the display screen can be improved as compared with the case where the display screen is provided.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a display-integrated tablet device 30 according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a detection pen 38 and a liquid crystal panel 31.

FIG. 3 is a block diagram illustrating a configuration of an x-coordinate detection circuit 40 in the display-integrated tablet device 30.

4 is a timing chart of each signal in an x coordinate detection circuit 40. FIG.

FIG. 5 is a block diagram illustrating a configuration of an erroneous detection determination circuit 43.

FIG. 6 is a block diagram illustrating a configuration of an erroneous detection determination circuit 60 in a display-integrated tablet device 30a according to a second embodiment of the present invention.

FIG. 7 is a block diagram showing a configuration of an erroneous detection determination circuit 70 in a display-integrated tablet device 30b according to a third embodiment of the present invention.

FIG. 8 is a timing chart in the display-integrated tablet device 30b.

FIG. 9 is a block diagram illustrating a configuration of an erroneous detection determination circuit 80 in a display-integrated tablet device 30c according to a fourth embodiment of the present invention.

FIG. 10 is a timing chart of signals applied to the electrodes X and Y in the display-integrated tablet device 30c.

FIG. 11 is a waveform diagram for explaining an operation of a pulse conversion circuit 39a in a display-integrated tablet device 30d according to a fifth embodiment of the present invention.

12 is a block diagram showing a configuration of a display-integrated tablet device having a duty-type liquid crystal panel 1. FIG.

FIG. 13 is a timing chart for explaining the operation of the display-integrated tablet device.

FIG. 14 is a timing chart of each signal during a coordinate detection period.

FIG. 15 is a waveform diagram for explaining the operation of the pulse conversion circuit 9 in the display-integrated tablet device.

FIG. 16 shows an active matrix type liquid crystal panel 2.
1 is a block diagram showing a display-integrated tablet device having a display device 1;

FIG. 17 is a waveform chart for explaining states of erroneous detection pulses.

[Explanation of symbols]

 30, 30a-30d Display integrated tablet device 31 Liquid crystal panel 32 Common electrode drive circuit 33 Segment electrode drive circuit 34 Switching circuit 35 Display control circuit 36, 36a-36c Detection control circuit 37, 37a-37c Control circuit 38 Detection pen 39, 39a pulse conversion circuit 40 x-coordinate detection circuit 41 y-coordinate detection circuit 42 DC power supply circuit 43 erroneous detection determination circuit 51 pulse width calculation circuit 52 reference pulse output circuit 53 pulse width comparison circuit

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-60-124723 (JP, A) JP-A-8-234907 (JP, A) JP-A-61-201321 (JP, A) JP-A-6-2013 295219 (JP, A) JP-A-5-53726 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G06F 3/03 310 G06F 3/03 335 G06F 3/033 350

Claims (5)

(57) [Claims] The surface position of a tablet on which a first electrode extending in a first direction and a second electrode extending in a second direction intersecting the first direction are arranged, the first electrode and the second electrode are sequentially arranged. By electrically scanning with a pulse signal in advance and instructing a coordinate detection electrode electrostatically coupleable to the first electrode and the second electrode with a detection means provided at the tip, a signal induced in the detected coordinates can be obtained. In a tablet device for detecting as coordinates based on a pulse width, a pulse width detecting means for detecting a pulse width of a signal induced in a coordinate detecting electrode; and a pulse width detected by the pulse width detecting means and a preset reference pulse width. A tablet device, comprising: an erroneous detection judging means for judging an erroneous detection when the difference between the pulse widths falls outside a predetermined allowable range. 2. The tablet device according to claim 1, wherein the first electrode extending in the first direction and the second electrode extending in the second direction intersecting with the first direction are arranged on the surface of the tablet. By electrically scanning with a pulse signal in advance and instructing a coordinate detection electrode electrostatically coupleable to the first electrode and the second electrode with a detection means provided at the tip, a signal induced in the detected coordinates can be obtained. A tablet device that detects coordinates based on the coordinates based on a plurality of consecutive coordinates stored in the storage device. Coordinate prediction means for predicting the coordinates of the surface position, and prediction error estimation for estimating a coordinate error predicted by the coordinate prediction means for the coordinates stored in the storage means as a prediction error Means, for the coordinates predicted by the coordinate predicting means, comparing the error of the coordinates detected by the coordinate detecting means and the prediction error by the prediction error estimating means, when the comparison result is out of a predetermined allowable range Erroneous detection determining means for determining erroneous detection, wherein the prediction error estimating means increases the value of the prediction error with an increase in the distance between the coordinates stored in the storage means. Tablet device. 3. A tablet in which a first electrode extending in a first direction and a second electrode extending in a second direction intersecting the first direction are arranged, the first electrode and the second electrode are sequentially arranged. By electrically scanning with a pulse signal in advance and instructing a coordinate detection electrode electrostatically coupleable to the first electrode and the second electrode with a detection means provided at the tip, a signal induced in the detected coordinates can be obtained. Scanning pulse generating means for continuously applying a plurality of scanning pulse signals to the first electrode and the second electrode, respectively; and a plurality of scanning pulses provided from the scanning pulse generating means. A pulse interval calculating means for calculating a pulse interval of a signal induced in the coordinate detection electrode by the pulse interval calculating means; and a comparison reference for determining a pulse interval calculated by the pulse interval calculating means in advance. A tablet device comprising: an erroneous detection judging means for judging an erroneous detection when the pulse interval is out of a predetermined range. 4. A tablet in which a first electrode extending in a first direction and a second electrode extending in a second direction intersecting the first direction are arranged, the first electrode and the second electrode are sequentially arranged. By electrically scanning with a pulse signal in advance and instructing a coordinate detection electrode electrostatically coupleable to the first electrode and the second electrode with a detection means provided at the tip, a signal induced in the detected coordinates can be obtained. In a tablet device for detecting as coordinates based on a pulse width, a pulse signal for scanning applied to a first electrode and a second electrode can be detected as a change in an induced voltage from a coordinate detection electrode at both a rising portion and a falling portion. A scanning pulse generating means for generating a pulse interval between the scanning pulses generated by the scanning pulse generating means, and a pulse for performing a calculation for obtaining a pulse interval of a signal induced on the coordinate detection electrode by the scanning pulse provided from the scanning pulse generating means. Calculating means for comparing the pulse interval calculated by the pulse interval calculating means with a predetermined comparison reference, and when the pulse interval is out of a predetermined range, erroneous detection determining means for determining erroneous detection; The tablet device, wherein the calculating means obtains a pulse interval of a signal induced by the coordinate detection electrode at a rising portion and a falling portion of the scanning pulse. 5. The first and second electrodes are electrodes for indicating coordinates and are electrodes for display of an image display panel having pixels at intersections, and determine whether to perform coordinate detection or display. 5. The tablet device according to claim 1, further comprising display / coordinate detection switching means for switching in a time-division manner.