JP3281256B2 - Coordinate input device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a coordinate input device used for a computer, a word processor, and the like.

[0002]

2. Description of the Related Art As one of input devices for performing a predetermined input to a computer, a word processor, or the like, a tablet capable of recognizing a figure or character and executing a command by an instruction of a pen or a finger is well known. Further, as a tablet which has evolved further, a display-integrated tablet device in which an electrode structure such as a liquid crystal panel and a drive circuit are shared and which has an inexpensive structure is disclosed in Japanese Patent Application Laid-Open Nos. 5-53726 and 6-63.
No. 3,314,166.

What is required of such a coordinate input device is high-speed and high-accuracy coordinate detection. Recently, it has been desired to further improve the accuracy of coordinate detection because the pixels of the display device are small, that is, the display is fine.

[0004]

However, since the speeding up and the accuracy improvement of the coordinate input device are contradictory effects, the conventional coordinate input device has to improve the coordinate detection accuracy while maintaining the high speed coordinate detection. There is a problem that can not be. That is, when performing coordinate detection at a high speed, the frequency band must be expanded, and the accuracy is reduced.

[0005] Among such coordinate input devices, a display integrated type device has further deteriorated coordinate detection accuracy for the following reasons. For example, Japanese Patent Application Laid-Open No. 5-537
In the configuration of Japanese Patent Publication No. 26, a display period and a coordinate detection period are performed in a time-division manner to achieve both display and a coordinate detection function. At this time, the coordinate detection period is set as short as possible so that the coordinate detection operation does not affect the display. Further, since the applied voltage for detection is limited by the withstand voltage of the display driving driver, a very high applied voltage is not applied. Furthermore, in the case of a coordinate input device provided integrally with a duty-type liquid crystal display device, the transparent electrode group on one side (back side) passes through the gap of the other (front side) electrode group.
Since it is electrostatically coupled with the tip electrode of the electronic pen, only a small detection voltage can be obtained. As a result, the display-integrated tablet device can only obtain a coordinate detection signal having a poor S / N.

Japanese Patent Application Laid-Open No. 6-314166 discloses a configuration in which a tablet function is added to an addressing type TFT liquid crystal panel. In order to improve the display quality, the TFT liquid crystal tends to reduce the width of the gate electrode and the source electrode, increase the area of the pixel electrode, and improve the aperture ratio. Also in this case, since the coordinate detection signal is detected in proportion to the coupling capacitance between the tip electrode of the electronic pen and the gate electrode or the source electrode, the coupling capacitance decreases as the aperture ratio increases, and the S / N of the detection signal increases. Worsens.
It is needless to say that the coordinate detection period of the coordinate input device provided integrally with the TFT liquid crystal display device must be minimized so as not to affect the display.

Further, in the conventional coordinate input device, a connection line of the electronic pen is indispensable for supplying power to the electronic pen and outputting a coordinate detection signal. Therefore, when the operator operates the electronic pen, the connection line is in the way, and the operability is significantly reduced.

[0008] A pressure-sensitive tablet in which an insulating spacer is inserted between two transparent electrodes and pressed with a pen tip or a finger, whereby the indicated coordinates can be known from the current flowing between the detection electrodes. Has also been proposed. However,
In this configuration, there are problems such as visibility due to transmittance and reflection of the transparent electrode, and input operation using a plurality of pointing tools and fingers cannot be performed at the same time.

A configuration in which a pen input function is realized by crossing transparent electrodes of a liquid crystal and measuring an electrostatic coupling capacitance with a pen tip or a finger is disclosed in US Pat. 463972
0 has been proposed. However, this configuration has a disadvantage that the structure and the driving method are complicated because the liquid crystal electrodes intersect on the same plane.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and has as its object to provide a coordinate input device which has high detection speed and high detection accuracy and can simultaneously perform a plurality of finger inputs. It is in.

[0011]

According to a first aspect of the present invention, there is provided a coordinate input device for detecting coordinates on a surface designated by a conductive indicator and outputting coordinate data. In order to achieve the above, the first electrode group arranged at a predetermined interval on the substrate and the first electrode group intersect and are arranged at a predetermined interval, and are insulated and electrostatically coupled with the first electrode group. A second electrode group and a second electrode switching unit that divides the coordinate detection period into a plurality of unit periods and selectively switches the electrodes of the second electrode group by one unit or a plurality of adjacent units in each unit period A pseudo-random signal generating means for generating a pulsed pseudo-random signal (for example, an M-sequence signal) having an autocorrelation function; First electrode driving means for sequentially applying a random signal; Basic waveform output means for outputting a basic waveform signal having substantially the same waveform as a voltage waveform induced on one or a plurality of adjacent electrodes of the second electrode group when the pointer does not indicate a coordinate position; Difference extracting means for extracting a difference signal between the detection signal induced at the electrodes of the second electrode group selected by the second electrode switching means and the basic waveform signal, and the difference signal exceeding a predetermined value To detect
When this is detected, X is used to detect the x coordinate from the electrodes of the second electrode group selected by the second electrode switching means.
Coordinate detecting means, correlation detecting means for obtaining a correlation between the difference signal and the pseudo random signal, and Y coordinate detecting means for detecting an extreme value of an output of the correlation detecting means and detecting a y coordinate. It is characterized by.

According to the above arrangement, the coordinate detection period is divided into a plurality of unit periods, and the electrodes of the second electrode group are divided into the second units in a predetermined unit (one unit or a plurality of adjacent units) in each unit period.
It is selectively switched by the electrode switching means.

The pseudo random signal generated by the pseudo random signal generating means is input to the first electrode driving means. During each of the unit periods, pseudo-random signals having different phase relationships are sequentially applied to the respective electrodes of the first electrode group by the first electrode driving means (for example, the pseudo-random signals are sequentially time-delayed by the shift register). Can be supplied to each electrode. As a result, during each unit period, voltage changes having slightly different phases appear on adjacent electrodes in the first electrode group.

The first electrode group and the second electrode group are electrostatically coupled, and a change in potential of the first electrode group is induced in the second electrode group. If a conductive indicator (for example, a user's own finger or a cordless pen having a metal case at the tip) indicating the coordinate position is brought close to the first electrode group, the indicator and the first electrode are electrically connected. And the potential induced in the second electrode group changes. Conversely, when the pointer does not indicate the coordinate position (that is, when the electrical coupling is negligible at a predetermined distance from the first and second electrode groups), the second
The voltage waveform induced in the electrodes of a predetermined unit (one unit or a plurality of adjacent units) of the electrode group is constant. A basic waveform signal having substantially the same waveform as the voltage waveform is output from the basic waveform output means (note that the basic waveform output means includes a configuration for reading a basic waveform pattern stored in a memory in advance, and a second electrode group. For example, a configuration may be considered in which a flat plate conductor is brought close to and amplifies the voltage induced on the flat plate conductor appropriately.

If there is no indicator near the electrode of the second electrode group selected by the second electrode switching means,
The difference between the detection signal induced at the electrode and the basic waveform signal is substantially zero. On the other hand, if there is an indicator near the electrode of the second electrode group, the difference is not zero because the potential induced on the electrode changes as described above. The difference signal is extracted by the difference extracting means, and the x coordinate is detected from the selected electrode of the second electrode group when the difference signal exceeds a predetermined value.

When a plurality of pointers are placed on the electrodes of a different second electrode group, a difference signal is given when the electrode on which the pointer is placed is selected by the second electrode switching means. Since the value exceeds the value, each x coordinate pointed by a plurality of pointers can be detected. This x
The coordinate detection processing is performed by X coordinate detection means.

Further, when the electrode of the second electrode group on which the indicator is placed is selected by the second electrode switching means, the difference signal obtained by the difference extraction means is:
7 shows a waveform pattern corresponding to a pseudo-random signal applied to an electrode of a first electrode group on which the indicator is placed. If the correlation between the difference signal and the pseudo random signal is obtained, an extreme value of the correlation output appears at a position corresponding to the phase of the pseudo random signal applied to the first electrode group on which the pointer is placed. The y coordinate corresponding to the detected x coordinate can also be detected. This x coordinate detection processing is performed by the correlation detection means and the Y coordinate detection means.

When a plurality of pointers are placed on different first electrodes on the same second electrode, a plurality of extreme values of the correlation output can be obtained. Can be detected.

In the method of detecting a voltage induced on a conductive indicator such as a finger or a metal piece as in the present invention, the coupling between the indicator and the first or second electrode group is very small. The detectable voltage level is also very small. However, the coordinate input device of the present invention uses a pseudo-random signal as a drive signal and performs a correlation operation when detecting coordinates,
The signal energy dispersed over time is compressed and collected at one point. As a result, the suppression ratio with respect to other signals such as random noise can be dramatically increased, and a high S / N can be obtained. As a result, it is possible to input coordinates with high detection accuracy without lowering the detection speed.

Further, according to the present invention, each electrode of the second electrode group is used as an electrode for detecting an induced voltage, and the electrodes of the second electrode group are switched by the second electrode switching means. , A plurality of coordinates can be detected, and simultaneous coordinates can be input by a plurality of pointers.

According to a second aspect of the present invention, the coordinate input device detects coordinates on the display panel indicated by the conductive indicator during the coordinate detection period, and converts the coordinates to the detected coordinates by display control during the subsequent display period. A display-integrated coordinate input device for displaying corresponding display information on a display panel, wherein a first electrode group arranged at a predetermined interval on a display panel substrate is provided to achieve the above object. A second electrode group intersected with the electrode group at predetermined intervals and insulated and electrostatically coupled to the first electrode group; first sequential driving means for driving the first electrode group; Second sequential driving means for driving the second electrode group, display control means for generating a display control signal for driving the first and second sequential driving means based on display information corresponding to the detected coordinates, Pseudorandom signal with correlation function A pseudo-random signal generating means for generating (for example, an M-sequence signal), the display control signal being selected during a display period, and the pseudo-random signal being selected during a coordinate detection period to perform first and second sequential driving. Output switching means for time-division output to the means, and a coordinate detection period divided into a plurality of unit periods, and one electrode of the second electrode group is set to one for each unit period.
A second electrode switching means for selectively switching in units of a plurality or adjacent units, and a pseudo-random signal having a mutually different phase is sequentially applied to each electrode of the first electrode group during each unit period. Control means for controlling the first sequential driving means (for example, a timing generation circuit for generating a clock or an initialization pulse); and one or a plurality of adjacent second electrode groups when the pointer does not indicate a coordinate position Basic waveform output means for outputting a basic waveform signal having substantially the same waveform as the voltage waveform induced on the electrodes of the unit, and a detection signal induced on the electrodes of the second electrode group selected by the second electrode switching means Difference extracting means for extracting a difference signal between the signal and the basic waveform signal, and detecting that the difference signal has exceeded a predetermined value, and selecting the second electrode switching means when the difference signal is detected. X coordinate detecting means for detecting the x coordinate from the electrodes of the electrode group, correlation detecting means for correlating the difference signal with the pseudo random signal, and detecting the extreme value of the output of the correlation detecting means to detect the y coordinate And a Y-coordinate detecting means.

The coordinate input device according to the present invention comprises an input device and a display panel having the same basic structure as the coordinate input device according to the first aspect. Therefore, the coordinate detection operation during the coordinate detection period is basically the same as the coordinate input device according to the first aspect.

In the coordinate input device of the present invention, the output control means selects the display control signal output by the display control means during the display period, and the pseudo random signal generation means generates the pseudo random signal during the subsequent coordinate detection period. The signal is selected, and the selected signal is switched and output to the first and second sequential driving means in a time-division manner.

During the display period, the first and second sequential drive means drive the first and second electrode groups for display based on the display control signal. On the other hand, during the coordinate detection period, the first sequential drive means is controlled by the control means to sequentially apply pseudo-random signals having different phases to each electrode of the first electrode group. The same operation as the electrode driving means is performed. The other processing during the coordinate detection period is as described above.

As described above, when the display operation and the coordinate input operation are performed, the first electrode group, the second electrode group, and the first sequential driving unit are used as common components, and are used in a time-sharing manner.
The display-integrated coordinate input device can have a simple configuration and can be reduced in size.

In the coordinate input device according to the present invention, similarly to the first aspect of the present invention, since the coordinate detection is performed by the correlation operation using the pseudo random signal, a high S / N ratio is obtained.
Can be obtained, and a coordinate input with high detection accuracy can be performed without lowering the detection speed.

In the conventional display-integrated coordinate input device, the coordinate detection period is set as short as possible so that the coordinate detection operation does not affect the display. As described above, the coordinate input device of the present invention can perform high-speed and high-accuracy coordinate detection, and can obtain good coordinate detection accuracy even in a short coordinate detection period.

According to a third aspect of the present invention, in the coordinate input device according to the second aspect of the present invention, the display panel includes a plurality of switching elements connected to the first and second electrode groups; A transparent pixel electrode in which a plurality of pixel electrodes to which elements are connected are arranged in a matrix, and a counter electrode provided to face the transparent pixel electrode,
The liquid crystal display panel is characterized by controlling the optical properties of liquid crystal sealed between the transparent pixel electrode and the counter electrode by driving the switching element.

When an active matrix liquid crystal display panel is used as the display panel, the areas of the first electrode group and the second electrode group are usually reduced as much as possible in order to increase the aperture ratio of image display. Although the electrical coupling between the group or the second electrode group and the indicator such as a finger becomes small, the obtained detection signal tends to be very small. However, the coordinate input device of the present invention uses the pseudo random signal to detect the correlation. Even if the aperture ratio of the display is increased, a highly accurate detection signal can be obtained.

According to a fourth aspect of the present invention, in the coordinate input device according to the second aspect of the present invention, the display panel is provided between a first electrode group and a second electrode group provided to face each other. The liquid crystal display panel is characterized in that the optical properties of the enclosed liquid crystal are controlled by an effective applied voltage between the first electrode group and the second electrode group.

When a liquid crystal display panel of this type is used as a display panel, the area where the first electrode group and the second electrode group intersect and the liquid crystal is sealed is usually made as large as possible in order to increase the display aperture ratio. , The electrical connection with the indicator,
The electrode group on the adjacent side has a large coupling, but the electrode group on the opposite side has a very small coupling because the electrode group is coupled through the gap of the electrode group on the front side. However, even in this case, the coordinate input device of the present invention can detect coordinates with high accuracy even at a low voltage drive by detecting the correlation of the pseudo random signal.

According to a fifth aspect of the present invention, in the coordinate input device according to the first, second, third or fourth aspect, the pseudo random signal is an M-sequence signal.

According to the above configuration, the pseudo random signal is represented by M
Since it is a series signal, a pseudo-random signal generating means having a small circuit scale can be configured. As a result, this is advantageous when configuring a portable coordinate input device that operates at high speed and has low power consumption.

[0034]

BEST MODE FOR CARRYING OUT THE INVENTION

[Embodiment 1] An embodiment of the present invention will be described below with reference to FIGS.

The coordinate input device according to the present embodiment detects coordinates using a spread spectrum technique.

As shown in FIG. 1, the coordinate input device comprises:
Timing generation circuit 1, M sequence (Maximum Length Code)
An information processing device 20 including a generation circuit 2, a column electrode drive circuit 3, a row electrode drive circuit 4, a coordinate input panel substrate 5, a column electrode group 6, a row electrode group 7, and a detection circuit 10, such as a computer or a word processor. It is connected to the.

The coordinate input panel substrate 5 is a flat plate based on an electrical insulator such as glass, phenol resin, polyethylene terephthalate, or acrylic.
A column electrode group (first electrode group) 6 and a row electrode group (second electrode group) 7 are arranged on one side or both sides of the coordinate input panel substrate 5 so as to be orthogonal to each other. Have been.

The column electrode group 6 includes n column electrodes.
Each column electrode is denoted by S1 to Sn. The row electrode group 7 includes m row electrodes, and each row electrode is indicated by G1 to Gm.
Note that the numbers of column electrodes and row electrodes may be equal or different.

The timing generation circuit 1 generates various control signals for driving the entire system, and outputs the control signals to the M-sequence generation circuit 2, the column electrode drive circuit 3, the row electrode drive circuit 4, and the detection signal. To the circuit 10.
As described later, the entire system operates based on the timing of the control signal generated by the timing generation circuit 1. The control signals include clocks ck1 and ck2, an M-sequence initialization pulse rm, a coordinate detection cycle signal d, a detection period signal det, and the like.

The M-sequence generating circuit (pseudo-random signal generating means) 2 is a circuit for generating an M-sequence signal m having a pulsed autocorrelation function based on the control signal. The M-sequence signal m is a noise having a strong whiteness, and is a function in which the autocorrelation is “1” only when the time difference is 0, and is “0” when the time difference is other than 0.

The above-mentioned row electrode drive circuit (first electrode drive means)
4 delays the M-sequence signal m by a shift register and outputs the M-sequence signal m having only a different phase to each of the row electrodes G1 to Gm.
Are sequentially applied.

The coordinates are designated by placing a conductive indicator 8 such as a cordless pen having a finger or a metal case on the tip of the user on the coordinate input panel substrate 5. The position coordinates placed are determined by the detection circuit 10 described above.
Is detected by The detection circuit 10 includes a differential amplifier circuit (differential extraction unit) 11, an A / D converter 12, a correlation calculator (correlation detection unit) 13, an LPF (low-pass filter) 14, and a Y coordinate detection circuit (Y coordinate). Detection means) 15,
An output circuit 16, a basic pattern generation circuit (basic waveform output means) 17, an X coordinate detection circuit (X coordinate detection means) 18, and a switch circuit (second electrode switching means) 19 are provided.

The information processing device 20 includes the detection circuit 1
Based on the coordinate value detected at 0, the display color of the pixel on the display at the corresponding position is changed to obtain an effect as if drawing with a pen, or the corresponding application program is driven based on the coordinate value. Or

FIG. 2 shows the operation timing of this embodiment.

The cycle for detecting the coordinates indicated by the indicator 8 such as the user's own finger is indicated by a total coordinate detection period Td, which is divided into individual coordinate detection periods Td1 to Tds. At the first timing of each coordinate detection period Tde (e = 1 to s), an M-sequence initialization pulse rm is output from the timing generation circuit 1 and supplied to the M-sequence generation circuit 2 and the row electrode drive circuit 4.

An M-sequence initialization pulse r is applied to the M-sequence generation circuit 2.
When m is input, the M-sequence generation circuit 2 is initialized, and subsequently generates an M-sequence signal m according to the clock ck1 supplied from the timing generation circuit 1.

The M-sequence signal m output from the M-sequence generation circuit 2 is supplied to the row electrode drive circuit 4 during the coordinate detection period Tde, and is shifted by the shift register incorporated in the row electrode drive circuit 4 to the timing generation circuit 1. The clock is delayed in synchronization with the clock ck2 supplied from. The signal voltage gi (i = 1 to m) corresponding to the delayed M-sequence signal m is sequentially applied to the row electrodes G1 to Gm. As described above, the potential pattern of the M-sequence signal m appears in the row electrode group 7 formed on the coordinate input panel substrate 5, and the pattern moves with time.

Next, the operation when the coordinates on the coordinate input panel substrate 5 are designated by the indicator 8 such as a finger will be described.

The indicator 8 is a conductor, and is provided with a column electrode group 6 and a row electrode through an insulator (not shown) such as a protective panel, an air layer, and a transparent substrate provided on the coordinate input panel substrate 5. It is electrostatically coupled to the electrode group 7.

FIG. 3 shows an electric connection state between the finger and the column electrode group 6 and the row electrode group 7 when the coordinates are indicated using the finger. Here, the finger is simultaneously electrostatically coupled with all the row electrodes G1 to Gm and the column electrodes S1 to Sn. When the position of the finger is as shown in the figure, the finger is closest to the column electrode S3 and the row electrode G1, and the coupling capacitance with these electrodes is the largest.

FIG. 4 shows the electrical connection state when the finger is not brought close to the coordinate input panel substrate 5, and the electric connection state when the finger is brought close to the coordinate input panel substrate 5 as shown in FIG. Are schematically shown in FIG.

One column electrode S3 and each row electrode Gi (i = 1
When the finger is not brought close to the coordinate input panel substrate 5 as shown in FIG.
Each row electrode Gi is connected to the corresponding column electrode S3 and Cs3i (i = 1 to
and m) the electrostatic coupling. Here, since the area of each row electrode Gi and the distance between each row electrode Gi and the column electrode S3 are set to be substantially constant, each coupling capacitance Cs3i is set.
Are also approximately equal. Therefore, from one column electrode S3, a detection voltage V (t) proportional to the total voltage Σgi (i = 1 to m) on which each signal voltage gi applied to each row electrode Gi is superimposed is obtained. Note that, in FIG.
3 is shown, but any column electrode Sj
The same can be said for (j = 1 to n).

When the finger is brought close to the coordinate input panel substrate 5 as shown in FIG.
i is electrostatically coupled to the column electrode S3 by a coupling capacitance Cs3, and is electrostatically coupled to the column electrode S3 by a coupling capacitance Cs3. Although FIG. 5 particularly shows only a portion connected to the column electrode S3, an arbitrary column electrode S
The same can be said for j (j = 1 to n).

When the finger is brought closer to the coordinate input panel substrate 5, the coupling capacitance between the row electrode Gi and the column electrode S3 is reduced to Cs3i '(Cs3i'<Cs3i).
This is because when the finger is brought closer to the coordinate input panel substrate 5, a part of the lines of electric force generated from the row electrodes Gi enter the finger and the number of lines of electric force entering the column electrode S3 decreases. This will be described in more detail with reference to FIGS.

Here, in order to simplify the explanation, only one row electrode Gy and one column electrode Sx will be described.

FIG. 6 shows a state in which the finger is not brought close to the coordinate input panel substrate 5, and the lines of electric force are indicated by broken lines. When a voltage is applied to the row electrode Gy, most lines of electric force enter the column electrode Sx. On the other hand, as shown in FIG. 7, when a conductor such as a finger is brought closer to the column and row electrodes Sx and Gy, a part of the lines of electric force generated from the row electrodes Gy are directed toward the finger. Here, assuming that the total number of lines of electric force is the same as in FIG. 6, the number of lines of electric force entering the column electrode Sx decreases. Therefore, when a conductor such as a finger approaches, the coupling between the row electrode Gy and the column electrode Sx is weakened, and the coupling capacitance between the two decreases.

Actually, a large number of row electrodes Gi (i = 1 to m) and column electrodes Sj (j = 1) are provided on the coordinate input panel substrate 5.
To n) are arranged, and there is an effect of adjacent electrodes. However, the coupling capacitance between the row electrode Gi and the column electrode Sj decreases as the conductor such as a finger approaches. Then, the closer the electrode is to the finger, the greater the rate of decrease. This is because the shorter the distance between the row electrode Gi and the finger, the stronger the electrostatic coupling between the row electrode Gi and the finger, and conversely, the weaker the coupling between the row electrode Gi and the column electrode Sj.

FIG. 8 shows an example of the coupling capacitance between the column electrode Sj and each row electrode Gi. This graph is a graph with the y-coordinate (row electrode) on the horizontal axis and the coupling capacitance between the column electrode S3 and each row electrode Gi on the vertical axis. In this example, since the finger is on the intersection of the row electrode G1 and the column electrode S3, the coupling capacitance Cs31 between the row electrode G1 and the column electrode S3 is the smallest.

The coupling capacitance Csji between the row electrode and the column electrode in the y direction on an arbitrary column electrode Sj will be described later as Csji (x) = hj (y) (1) Thus, the model is treated as a continuous system.

As described above, the detection voltage V (t) corresponding to the total voltage Σgi of the signal voltages gi of the respective row electrodes Gi is induced in the column electrodes Sj where no finger is placed.
This V (t) is used as a basic pattern. On the other hand, when the finger is brought closer to the electrode, in the column electrode Sj closest to the finger, the induced voltage from the row electrode Gy closest to the finger is:
Because it is smaller than the induced voltage from other row electrodes,
The detected voltage is changed from V (t) of the basic pattern to a waveform pattern Vdy (t) having a small component of the signal gy (signal corresponding to the M-sequence signal m) applied to the row electrode Gy,
This is different from the waveform pattern (basic pattern) V (t) of the column electrode on which no finger is placed. Conversely, by examining the electrode where the detected voltage has changed, the column electrode at the position where the finger is placed, that is, the x-coordinate can be found.

Here, the signal voltage gi applied to each row electrode Gi is obtained by sequentially delaying the M-sequence signal m by a shift register built in the row electrode drive circuit 4. The phase is different for each cycle of the operation clock ck2 (see FIG. 2). Clock ck2
Is the period of Δt ₂ , the signal voltage gi of each row electrode Gi
Is represented by the following equation. gi (t) = m (t−Δt ₂ × i) (2) where m (t) represents the M sequence signal m as a function of time, that is, the M sequence generation circuit 2 The output waveform of FIG.

In the coordinate detection period Tde, the row electrode G
An i-sequence M-sequence signal m corresponding to the y-coordinate position is applied to i. In the state of FIG. 3, the detection voltage Vdj ′ (t) induced at each column electrode Sj has a G1 potential pattern. The component of a certain m (t−Δt ₂ × 1) is the least.

From the above equations (1) and (2), the detection voltage Vdj '(t) is expressed as follows. Vdj '(t) = {hj (y) .m (ty) dy ... (3) However, since equation (3) is actually a discrete system, ∫ is represented by Σ.

Here, by taking the difference between V (t), which is the basic pattern, and Vdj '(t), only the pattern with a reduced number of components can be reproduced. That is, it is possible to detect a pattern including a large amount of the induced voltage component induced by the signal voltage gy at the row electrode Gy on which the finger is placed.

Here, the M-sequence will be described. The M-sequence is a binary sequence signal, and can be easily created using a shift register and an exclusive OR, for example, as shown in FIG. However, the feedback tap extracted from the middle part of the shift register may not be extracted from any position of the register, and a data sequence extracted only when a specific small number of combinations are used is called an M sequence.

The M-sequence mainly has the following three properties. If the ratio of the number of “0” and “1” included in one cycle is constant and a k-stage shift register is used, the number of “1” is 2 ^{k−1 and the} number of “0” is (2 ^k-1 ) -1. That is, the number of “0” is smaller by one. Assuming that the length of the continuation when “0” or “1” appears continuously in the series is L, the frequency of occurrence of the continuation of the length L in one cycle of the series is twice the frequency of the length L + 1. become. When the generated M-sequence and the data of the same M-sequence differing only in the initial value of the register are added, the same M-sequence is obtained by shifting the original M-sequence in time.

Therefore, the product of itself and the one shifted in time becomes M-sequence again due to the property of
, The correlation value becomes almost “0”. However, when there is no time lag between the two waveforms, the waveforms are the same, so the correlation value is “1”. In other words, when the correlation value is “1”, the two waveforms completely match, and when the correlation value is “0”, it means that the instantaneous values of the two waveforms at each time are not similar.

In the M-sequence signal m of this embodiment, when n is the number of stages of the shift register, ai is a coefficient, and _Xki is an output from a feedback tap, the M-sequence signal {X _k } (= m) is (See FIG. 12). X _k = (a1 × X _k-1 ) ∧ (a2 × X _k-2 ) ∧ · ∧ (an × X _kn ) (4) where ai and X _ki are 0 or 1, ∧ is exclusive OR.

The detection voltage Vdj '(t) at the column electrode Sj
First, the switch circuit 19 in the detection circuit 10 of FIG.
Input terminal. In the switch circuit 19, one switch is associated with each column electrode Sj, and each time an M-sequence initialization pulse rm is input from the timing generation circuit 1, one switch is sequentially selected from the switch group, and The detection voltage Vdj ′ (t) is output to the amplifier circuit 11. At this time, a plurality of adjacent column electrodes may be collectively associated with one switch so that the level of the output detection voltage is increased to some extent.

As shown in FIG. 2, the time for continuously selecting one switch, that is, the coordinate detection period Tde is:
The period from when the application of the M-sequence signal m to the first row electrode G1 starts to when the application of the M-sequence signal m to the last row electrode Gm ends. Therefore, when there are s switches in the switch circuit 19, s times M-sequence signal patterns are input to each row electrode Gi.

The output from the switch circuit 19 is input to the inverting input terminal of the differential amplifier circuit 11. On the other hand, the basic pattern V (t) generated by the basic pattern generation circuit 17 based on the M-sequence initialization pulse rm from the timing generation circuit 1 is input to the non-inverting input terminal of the differential amplifier circuit 11. . Accordingly, the differential amplifier circuit 11 outputs a voltage pattern Vdj (t) obtained by amplifying V (t) −Vdj ′ (t), which is the difference between the two inputs.

The basic pattern generation circuit 17 includes a memory, and the basic pattern V
Since the information of (t) is stored, the basic pattern V (t) can be generated by reading out the information based on the M-sequence initialization pulse rm.

Next, the detection voltage Vdj (t) output from the differential amplifier circuit 11 is input to the A / D converter 12 and converted into a digital signal. The output of the A / D converter 12 is input to an X coordinate detection circuit 18.

The X coordinate detection circuit 18 monitors whether the A / D converted detection voltage Vdj (t) has exceeded a predetermined level. The fact that the detection voltage Vdj (t) exceeds the predetermined level during the coordinate detection period Tde means that the detection voltage Vdj (t) is above the column electrode connected to the switch of the switch circuit 19 selected in the coordinate detection period Tde. Indicates that the indicator 8 is placed. The X-coordinate detection circuit 18 receives a signal from the switch circuit 19,
The switch selection signal for identifying the switch being selected is input, and the X coordinate detection circuit 18 calculates the switch selection signal based on the switch selection signal input when the detection voltage Vdj (t) exceeds a predetermined level. X indicated by the indicator 8
Detect coordinates. Then, the X coordinate detection circuit 18 outputs an x coordinate signal XADR obtained from the switch selection signal input from the switch circuit 19 to the output circuit 16.

The detection voltage Vdj (t) output from the A / D converter 12 is also input to one input terminal of the correlation calculator 13. The other terminal of the correlation calculator 13 is supplied with the M-sequence initialization pulse rm output from the timing generator 1. The correlation calculator 13 performs a correlation operation between the detection voltage Vdj (t) and the M-sequence of the same order as the M-sequence signal m generated by the M-sequence generation circuit 2 based on the M-sequence initialization pulse rm. , Sequentially,
The correlation result dj (τ) is output and supplied to the LPF.

Here, the output dj (τ) of the correlation calculator 13
Is represented by dj (τ) = ∫Vdj (t) · m (t−τ) dt (5), and from the equation (3), dj (τ) = よ り hj (y) · m (t−y) · m (t−τ) dtdy (6) In Expression (6), when m (t) that satisfies the following Expression (7), δ (τ) = ∫m (t) · m (t−τ) dt (7) is used, Dj (τ) in equation (6)
Is obtained as follows: dj (τ) = ∫hj (y) · δ (τ−y) dy = hj (τ) (8)

The equation (7) is an autocorrelation function, which shows how similar the waveform of the two is to the one shifted in time when the two periodic functions to be compared are the same. ing. From equation (8), the detection voltage Vdj (t)
When the correlation between m and (m) is obtained, hj (τ) itself in FIG. 8, which is the electrostatic coupling distribution function between the row electrodes G1 to Gm and the column electrode Sj, can be restored. Since the output dj (τ) of the correlation calculator 13 is equal to hj (τ), the Y-coordinate detection circuit 15 detects the position τ at which the extreme value of the function dj (τ) obtained through the LPF 14 is detected. Is the indicator 8
, The coordinates in the row electrode direction, that is, the y coordinates.
Then, the Y coordinate detection circuit 15 detects the detected y coordinate signal Y
The ADR is output to the output circuit 16.

The x-coordinate “x” detected by the X-coordinate detection circuit 18 and the y-coordinate “y” detected by the Y-coordinate detection circuit 15 are output via the output circuit 16 to a computer or the like. Is output to the information processing device 20. The information processing device 20, which has received the coordinate information, changes the display color of the pixel on the display at the position corresponding to the coordinates, or activates the application program corresponding to the designated coordinates.

Incidentally, actually, random noise due to thermal noise, shot noise, or the like is generated at the input section of the differential amplifier circuit 11, which has a significant effect on the detection result. Assuming that the generated random noise is nj (t), the output dj (τ) of the correlation calculator 13 is dj (τ) = hj (τ) + ∫nj (t) · m ( t−τ) dt... (9)

The second term in the equation (9) means that random noise is subjected to convolution conversion with the M-sequence signal m.
The result is random noise having all frequency components. The first term of the equation (9) is hj (τ),
As shown in FIG. 9, the signal is a signal containing a large amount of low frequency components. Therefore, the actual output dj of the correlation calculator 13
The frequency spectrum of (τ) is represented by hj (τ) shown in FIG.
And ∫nj (t) · m (t−τ) dt. In this case, using the LPF 14, the output dj (τ)
When a filtering process for suppressing high frequency components as shown in FIG. 10 is performed, only a high frequency noise is suppressed as shown in FIG. 11, and a detection signal having a high S / N is obtained.

In the above description, the coordinate detection for the plurality of pointers 8 is not particularly described. However, as will be described, the same can be handled in the same manner.

First, let us consider a case where a plurality of pointers 8 are placed on different column electrodes Sa to Sz, respectively. As described above, using the switch circuit 19, the total coordinate detection period Td
Are sequentially selected one by one (or a plurality of adjacent ones) while switching for each coordinate detection period Tde obtained by dividing s by s, and the column electrodes Sa to Sz on which the indicator 8 is placed Only when is selected by the switch circuit 19, the X coordinate detection circuit 18 outputs the x coordinate signal XADR corresponding to the column electrodes Sa to Sz as described above. That is, within the total coordinate detection period Td, the x coordinate signals XADR are obtained as many as the number of the pointers 8 placed, and a plurality of x coordinates xa to xz can be detected. Further, from the output of the correlation calculator 13 corresponding to each obtained x coordinate,
Since the y-coordinate of each of the column electrodes Sa to Sz is obtained in the Y-coordinate detection circuit 15, (xa, ya) to (x
(z, yz) are obtained.

Next, the plurality of pointers 8 are connected to the same column electrode Sa.
Let us consider the case where they are placed on different upper row electrodes Ga to Gz. Regarding the x-coordinate, when the switch circuit 19 selects the column electrode Sa, the x-coordinate detection circuit 18 outputs an x-coordinate signal XADR corresponding to the column electrode Sa. That is, the x coordinate xa is determined. The column electrode S
The output da of the correlation calculator 13 when a is selected
(Τ) is represented by the following equation.

Da (τ) = ha (τ) + · + hz (τ) dt + ∫na (t) · m (t−τ) + ·· + ∫nz (t) · m (t−τ) dt (10) The function da (τ) has the same number of extreme values as the number of the indicators 8 placed on the column electrodes Sa. When the position τa to τz at which the extreme value of the function da (τ) obtained via the LPF 14 is detected by the Y coordinate detection circuit 15, the τa to τz are the coordinates in the row electrode direction designated by the indicator 8, that is, The y coordinate. In this way, a plurality of coordinate values (xa, ya) to (xa, yz) are obtained.

Hereinafter, each circuit constituting the coordinate input device will be described in detail.

(1) M-sequence generating circuit 2 FIG. 12 shows a configuration example of the M-sequence generating circuit 2. The M-sequence generating circuit 2 generates an M-sequence having an order of 6 and an M-sequence having a repetition period of 2 ⁶ -1 = 63, and a timing chart thereof is shown in FIG. The operation of the M-sequence generation circuit 2 will be described with reference to FIGS.

The M-sequence generation circuit 2 includes flip-flops 21 to 26 with synchronous set terminals and an exclusive OR 27. Terminal Q of flip-flops 21 and 26
Is connected to the input terminal of the exclusive OR 27. The output terminal of the exclusive OR 27 is connected to the terminal D of the flip-flop 21 and serves as the output terminal of the M-sequence generation circuit 2 to output the M-sequence signal m. A clock ck1 is supplied from the timing generation circuit 1 to a terminal CK of each flip-flop, and an M-sequence initialization pulse rm is supplied to a terminal S of each flip-flop.

When the M-sequence initialization pulse rm changes from "0" to "1", the terminals D of the flip-flops 21 to 26 are set to "1" at the rise of the clock ck1. Until the next rising edge of the clock ck1, the terminal Q of the flip-flop 21 and the terminal Q of the flip-flop 26
Is “1”, the output of the exclusive OR 27 is “0”, and the M-sequence signal m is “0”. At the next rising edge of the clock ck1, "0" which is the output of the immediately preceding exclusive OR 27 is set in the flip-flop 21, and the flip-flop 2 is immediately set in the flip-flops 22 to 26.
The data held in 1 to 25 is shifted rightward and "1" is set. Terminal Q of flip-flop 21
Is "0" and the terminal Q of the flip-flop 26 is "1", the output of the exclusive OR 27 is "1", and the M-sequence signal m is "1" in this clock cycle. Note that 21D to 26D in FIG. 13 indicate signals input to the terminals D of the flip-flops 21 to 26.

As described above, the M-sequence generation circuit 2 of FIG.
As shown in FIG. 13, "0101011001101110"
.. ”Are output to the row electrode drive circuit 4. The above pattern is repeated at 63 clock cycles of the clock ck1.

Note that, here, an example has been described in which the order of the M-sequence is set to 6. However, when the order is set to another order, the configuration of FIG. 12 may be changed based on Table 1 below. Table 1 is a coefficient table serving as an index when configuring the M-sequence generation circuit 2 when generating M-sequences of other orders.

[0091]

[Table 1]

(2) Row electrode drive circuit 4 As shown in FIG. 14, the row electrode drive circuit 4 includes an AND gate 100, a number of D flip-flops 101 to 10a,
And a number of analog switches 111 to 11a.

The detection period signal det from the timing generation circuit 1 and the M-sequence signal m from the M-sequence generation circuit 2 are input to the AND gate 100. Detection period signal d
et becomes “1” during the comprehensive coordinate detection period (see FIG. 2),
At this time, the AND gate 100 passes the M-sequence signal m and supplies the M-sequence signal m to the input terminal D of the flip-flop 101. The flip-flops 101 to 10a constitute a shift register, and input data is shifted rightward in synchronization with the clock ck2. The output terminal Q of each flip-flop is connected to the input terminal D of the next-stage flip-flop and the analog switches 111 to 11 are connected.
It is also connected to the control terminal U of FIG.

When "0" is input to the control terminal U, the analog switches 111 to 11a are connected to the "a" side.
Is connected to the b side. Therefore, when the outputs of the flip-flops 101 to 10a are "0", the voltage V0 connected to the a side is applied to the row electrode G when it is "1". Since the M-sequence signals m are successively shifted to the shift register, the potential patterns of the voltages V0 and V1 are applied to the row electrodes G corresponding to the M-sequence signals m.

(3) Switch Circuit 19 FIG. 15 shows a configuration example of the switch circuit 19. The switch circuit 19 is connected to each of the column electrodes S1 to S
The switches SW1 to SWn are respectively connected to the connection lines S1 'to Sn' connected to n. Here, for simplicity of description, it is assumed that the switch circuit 19 is composed of six switches SW1 to SW6. Each of the switches SW1 to SW6 has an L terminal and an R terminal, all the L terminals are connected to a reference potential, and all the R terminals are connected to one and connected to a differential amplifier circuit 11 at a subsequent stage. ing.

When the coordinate detection cycle signal d (see FIG. 2) is input from the timing generation circuit 1 to the switch circuit 19, all the switches SW1 to SW6 are connected to the L terminal, and therefore, all the column electrodes Is the reference potential. Next, an M-sequence initialization pulse r is supplied to the switch circuit 19.
When m is input, first, only the switch SW1 is connected to the R terminal side. Thereby, the voltage induced in the column electrode S1 is input to the switch circuit 19 through the connection S1 ', and is output to the differential amplifier circuit 11 as a signal Vy. Further, when the next M-sequence initialization pulse rm is input after the coordinate detection period Tde has elapsed, the switch SW1 switches to the L terminal, and the switch SW2 is connected to the R terminal instead. As a result, the voltage induced in the column electrode S2 is input to the switch circuit 19 through the connection S2 ', and the signal Vy
Is output to the differential amplifier circuit 11. Hereinafter, similarly, S
The voltage sequentially selected up to W6 and induced in each column electrode is
The signal is output to the differential amplifier circuit 11.

The switch circuit 19 is reset at the rise of the detection period signal det, and the coordinate detection period Td
A counter 21 is provided which counts the number of times the M-sequence initialization pulse rm is input for each e. The counter 21 counts the number of times the M-sequence initialization pulse rm has been input during the comprehensive coordinate detection period Td, and the switch circuit 19 outputs the count of the counter 21 to the X coordinate detection circuit 18 as a switch selection signal.

(4) Correlation Calculator 13 FIG. 16 shows a configuration example of the correlation calculator 13. Correlation calculator 1
3 is a k-bit n flip-flops 31 to 3n;
It comprises adders 40 and 41 for adding each intermediate output, and a subtractor 42 for calculating the difference between the outputs of the two adders. Here, n is a number equal to or longer than the repetition period of the M series, and n is 63 in the present embodiment.

The digital data ado input from the A / D converter 12 is input to the terminal D of the flip-flop 3n, and k-bit data is sequentially shifted to the subsequent flip-flop by the clock ck1. Assuming that the digital data applied to the input terminal (terminal D of the flip-flop 3n) of the correlation calculator 13 is ado (t), the digital data appearing at the output terminal Qi of the i-th flip-flop is ado (ti). is there.

On the other hand, the sixth-order M-sequence signal m is obtained by the above (1)
As shown in the item of the M-sequence generation circuit 2, it is expressed as follows. {M1, m2,..., M63} = {0, 1, 0,... 1} (11) The output terminal Q of each flip-flop is a terminal corresponding to "1" in equation (11). The input terminal of the adder 40 is connected, and the terminal corresponding to “0” is connected to the input terminal of the adder 41.

For example, the flip-flop 31 has m1 = 0.
And the flip-flop 32 corresponds to m2 = 1, so that the adder 40 is connected to the input terminal of the adder 41.
Is connected to the input terminal. With this connection, the output S1 of the adder 40 and the output S2 of the adder 41 are obtained from the following calculation results.

[0102]

(Equation 1)

The outputs S of the adders 40 and 41 obtained above
1 · S2 is supplied to the input terminal of the subtractor 42, and the subtractor 42 calculates dj (τ) = S1−S2 and outputs it as dj (τ).

FIG. 17 shows an ideal timing chart according to the configuration example of FIG. The clock ck1 and the M-sequence initialization pulse rm are control signals output from the timing generation circuit 1, and are supplied to the flip-flops 31 to 3n. The M-sequence initialization pulse rm is a pulse that becomes “1” for one cycle of the clock ck1, and the flip-flops 31 to
3n is input to the synchronous reset terminal R, and the clock ck1
At the rising edge of the flip-flop, the contents of all flip-flops become “0”, and the Q terminal output ad of each flip-flop
o (ti) are all “0” (where i = 1 to
63).

Assuming that the indicator 8 is closest to the row electrode G1, the detection output ado (t) of the indicator 8 via the A / D converter 12 is output as shown in the fifth row in FIG. Electrode G1
Has a waveform very similar to that of the potential change. Flip-flop 3
Digital data ado (t) input to 1 to 3n is shifted rightward in synchronization with clock ck1.

At this time, the outputs of the flip-flops 31 to 3n are respectively set as a to a as shown in the sixth to eighth stages of FIG.
do (t-1),... ado (t-62), ado
The delayed data appears as (t-63). Since the voltage originally applied to the row electrode G1 is a signal delayed by one clock from the M-sequence signal m (t), the output of the subtractor 42 is at a position delayed by 1 + 63 + 1 = 65 clocks from the M-sequence initialization pulse rm. Only "1" is set. This is due to the property that the autocorrelation of the M sequence becomes “1” only when the time difference is 0.

In practice, the coupling capacitance between the column electrode S3 and each row electrode is as shown in FIG.
The waveform of do (t) receives an effect equivalent to a spatial low-pass filter, and becomes a smooth waveform as shown in FIG. Therefore, the output ado (ti) of each flip-flop also has a smooth waveform. As a result, the output d3 (τ) obtained from the subtractor 42 is also 1 + 63 from the M-sequence initialization pulse rm.
A smooth waveform having a peak at a position delayed by + 1 = 65 clocks is obtained. The output d3 (τ) obtained here is (9)
Given by the formula.

Also, the plurality of pointers 8 are connected to one column electrode S
j, when the plurality of row electrodes Ga to Gz are close to each other, the voltage applied to each of the row electrodes Ga to Gz is:
Since the signal is delayed by a,..., Z clocks from the output m (t) of the M-sequence generation circuit 2, the output dj of the subtractor 42
(Τ) is 1 + 63 + a = from the M-sequence initialization pulse rm.
64 + a,..., 64 + z The waveform becomes a smooth waveform with the extreme value at the position delayed by the clock. The output waveform dj (τ) obtained at this time is given by equation (10).

(5) LPF 14 As expressed by the equation (10), the output dj (τ) of the correlation calculator 13 includes an M series converted random noise generated in the differential amplifier circuit 11. Output dj
The component (τ) is also random noise having all frequency components. When the random component of the output dj (τ) is large, the detection of the peak position by the Y coordinate detection circuit 15 leads to an increase in detection error or erroneous detection.

However, hj in the first term of equation (10)
The detection signal component represented by (τ) has many low frequency components as shown in FIG. 9, and the random noise component of the second term is a signal spread from a low frequency to a high frequency component. Therefore, S / N can be improved by using a low-pass filter that mainly passes hj (τ).

FIG. 19 shows a configuration example of the LPF 14. LP
F14 is an m-1 k-bit flip-flop 51
~ 5m-1, m multipliers 61 to 6m, and adder 7
Has zero.

The output terminal Q at the preceding stage of each flip-flop is connected to the input terminal D at the subsequent stage, and the flip-flop 5m-
The output dj (τ) of the correlation calculator 13 is supplied to one input terminal D. Further, the clock ck1 and the M-sequence initialization pulse rm from the timing generation circuit 1 are supplied to each flip-flop.

The input terminals D of the multipliers 61 to 6m-1 have:
Output terminals Q of corresponding flip-flops 51-5m-1
Are respectively connected. The input terminal D of the multiplier 6m
Receives an output dj (τ). Coefficient k ₁ to k _m predetermined to the input terminal K of the multiplier 61~6m is input. Each of the multipliers 61 to 6m outputs a multiplication result represented by S = D × K (14).

Since the output terminals S of the multipliers 61 to 6m are connected to the input terminals l1 to lm of the adder 70,
The adder 70 calculates the sum of them and outputs the result as djs (τ). As a result, djs is represented by djs (τ) = Σdj (τ−i) × k _mi (15). However, i = 0 to m-1.

Here, when the coefficient k _i given by the following equation is given as the coefficient k _i , the LPF 14 becomes a matched filter, and the S / N can be maximized.

K _i = 1−Csji / (Cs1i + Cs2i +... + Csmi) (16) In order to reduce the circuit scale as much as possible, the filter circuit is configured by ignoring the small coefficient k _i. You may.

Table 2 shows an example of the index of the multiplication coefficient when the number m of the multipliers is five. Each coefficient k _i is 0.1, 0.2, 0.
Assuming that the values are 4, 0.2 and 0.1, the operation timing chart is as shown at the bottom of FIG. That is, the output djs (τ) of the LPF 14 is 1 + 6 from the M-sequence initialization pulse rm.
3 + 1 + 2 = peak at a position delayed by 67 clocks (extreme value)
Is obtained. Note that 61D to 65D in FIG.
Indicates signals input to the input terminals D of the multipliers 61 to 65.

[0118]

[Table 2]

A plurality of pointers 8 are connected to one column electrode S
j, the output djs (τ) of the LPF 14 is 1 + 63 + a + 2 = 66 + a,..., 66 from the M-sequence initialization pulse rm when the row electrodes Ga to Gz are close to each other.
A smooth waveform having an extreme value at a position delayed by + z clocks is obtained.

As described above, when the LPF 14 is a matched filter, the output dj (τ) from the correlation calculator 13
/ N can be maximized. Also, when an ideal matched filter is used, the output djs of the LPF 14 even when the indicator 8 points to the end of the coordinate input panel substrate 5
(Τ) is a function that is symmetric with respect to τ. Therefore, it is easy to detect as a pulse when determining coordinates, and it is possible to perform stable coordinate detection with respect to noise and fluctuations in detection output.

[0121] Incidentally, (16) there is shown an example of a matched filter in equation if fulfill the function of the low-pass filter as a whole, a simple factor such coefficients k _i to reduce the circuit scale "1" or "0" It may be. Also, this L
The configuration of the PF 14 is not limited to the FIR (finite impulse) type, but may be an IIR (infinite impulse) type. In this case, the circuit scale is further reduced, and S
/ N can also be improved.

(6) Y coordinate detection circuit 15 The specific operation of the Y coordinate detection circuit 15 will be described with reference to the configuration example of FIG. 21 and the timing chart of FIG.
The Y coordinate detection circuit 15 includes k-bit flip-flops 71 and 72 with a synchronous reset terminal R, and an n-bit flip-flop 7 with a reset terminal R and an enable terminal EN.
3.74.75, comparator 76, f with synchronous reset terminal R
Bit up counter 77, f with enable terminal EN
It has a bit flip-flop 78 and a correction circuit 79.

First, when the M-sequence initialization pulse rm is supplied from the timing generation circuit 1, the flip-flop 7
1 to 75 and the up counter 77 are reset,
The outputs from all the output terminals Q are "0". The output terminal Q of the flip-flop 74 is the input terminal a of the comparator 76.
Since the output terminal Q of the flip-flop 71 is connected to the input terminal b of the comparator 76, "0" is output from the output terminal a <b of the comparator 76. Therefore, the enable terminals EN of the flip-flops 73, 74, 75, 78 become "0", and the flip-flops are disabled.

Since the output djs (τ) of the LPF 14 is supplied to the input terminal D of the flip-flops 71 and 73, the output djs (τ) is synchronized with the clock ck1.
The data shifts to 72. Flip-flop 71
The output terminal Q outputs data delayed by one clock cycle of the output djs (τ).
Has been entered. Since the flip-flop 74 outputs “0”, which is input to the input terminal a of the comparator 76, the output of the comparator 76 changes to “0” until the flip-flop 71 becomes larger than “0”. I keep it.

As shown in the fifth stage in FIG. 22, when the output 71Q (b) of the flip-flop 71 becomes larger than "0",
The output 76a <b (EN) of the comparator 76 becomes "1",
At the next rise of the clock ck1, to no flip-flops 73 and 75 to enable the flip-flop 73 is djs (tau), the flip-flop 74 djs (τ- △ t _2), flip-flop 75
Latches data of djs (τ−2 × Δt ₂ ).

On the other hand, after being reset by the M-sequence initialization pulse rm, the up-counter 77 counts up by the clock ck1, and the output 76a <
When b (EN) becomes “1”, the enable terminal EN of the flip-flop 78 connected to the subsequent stage of the up-counter 77 also becomes “1” and becomes enabled, latches the data of the up-counter 77 and outputs it as data ADR. Output to the correction circuit 79.

The data djs (τ− △) of the flip-flop 71 is obtained from the data stored in the flip-flop 74.
When t ₂ ) increases, the output of the comparator 76 becomes “1” as described above, and the data of the flip-flops 73 to 75 and the count data of the flip-flop 78 are updated. If the data djs of the flip-flop 71 is obtained from the data stored in the flip-flop 74,
When (τ− △ t ₂ ) becomes small, the output of the comparator 76 becomes “0” again, and the flip-flops 73, 74, 75.
Reference numeral 78 is disabled, and the previous data is retained without updating the data.

That is, when these operations are completed, d
The maximum value M2 = djs (τ _max ) of js (τ) is stored in the flip-flop 74 as data M3 = djs (τ
_max - △ t ₂₎ to the flip-flop 75, also immediately after the data _{M1 = djs (τ ma x +} △ t 2) is held in the flip-flop 73, it is supplied to the correction circuit 79.
At the same time, the value of the up counter 77 is held as a coordinate value in the flip-flop 78 as a timing at which the maximum value M2 is captured, and is supplied to the correction circuit 79 as data ADR.

In the correction circuit 79, M1 · M2 · M
By substituting the data of No. 3, the input data ADR is corrected, and a more accurate f + α bit output YADR is output. That is, the input data ADR
Is corrected to the output YADR by the following equation (17).

YADR = ADR + (M3-M1) / (2 × M2-M1-M3) / 2 (17) As shown in FIG. 23, the correction circuit 79 includes a doubler 90 and a subtractor. 91/92, adders 93/94, divider 95, 1 /
It can be constituted by a doubler 96. Note that the doubler 90 and the ９６ multiplier 96 may be configured by bit shifting by connection.

As described above, by configuring the correction circuit 79, an accurate peak position can be detected based on the equation (17). In particular, if a matched filter is employed for the LPF 14, the output djs (τ) of the LPF 14 becomes a target function for τ, so that the detection accuracy by the quadratic curve interpolation of the equation (17) is further improved.

(7) Output Circuit 16 Next, the output circuit 16 will be described with reference to the configuration example of FIG. 24 and the timing chart of FIG. Output circuit 16
Has an flip-flop 97/98 with an enable terminal EN of f + α bits and an interface 99 with the information processing device 20.

Enable terminal E of flip-flop 97
The control signal YEN is input to N, and the control signal XEN is input to the enable terminal EN of the flip-flop 98, respectively. The control signals YEN and XEN are pulses supplied from the timing generation circuit 1 and generated at the end of the coordinate detection period Tde in the same cycle as the individual coordinate detection period Tde.

In the coordinate detection period Tde, the column electrode is driven by the M-sequence signal m, a signal electrostatically induced in the column electrode is detected by the correlation calculator 13, and the signal peak position is determined via the LPF 14 to the Y coordinate. The detection circuit 15 performs the calculation. When this series of operations is completed, the output YAD of the Y coordinate detection circuit 15 is output.
The detected y coordinate is determined for R. The output YADR is input to the input terminal D of the flip-flop 97,
The control signal YEN becomes “1” after the output YADR is determined, and its value is stored in the flip-flop 97 and output to the interface 99 as the Y coordinate value YADR.

On the other hand, the output XADR of the X coordinate detection circuit 18
, The detected x-coordinate is determined. This output XADR
Is input to the input terminal D of the flip-flop 98, and the control signal XEN becomes “1” after the output XADR is determined.
And the value is stored in the flip-flop 98, and X
The coordinate value is output to the interface 99 as XADR.

Interface 9 with Computer 15
9 includes RS (Recommanded Standard) 232C and GP
There are a method based on various standards such as IB (general purpose interface bus) and a method directly connected to the input / output bus of the information processing device 20.

In the present embodiment, the basic pattern generating circuit 17 has the same configuration as that of the basic pattern generating circuit 17.
The basic pattern V (t) is previously stored in the built-in memory.
Is stored, and the information is read out to generate the basic pattern V (t). However, the present invention is not limited to this. For example, a flat conductor (not shown) is brought into close contact with (approached to) the entire surface or a part of the coordinate input panel substrate 5, and a voltage induced on the flat conductor is appropriately amplified as a basic pattern V (t). The signal may be input to the differential amplifier circuit 11. This is because the reduction of the induced voltage caused by placing the indicator 8 such as a finger on the coordinate input panel substrate 5 is small, and if the induced voltage is picked up by a flat conductor having a sufficiently large area, the basic pattern V (t) is obtained. Is induced.

As described above, the coordinate input device according to the present embodiment sets the total coordinate detection period Td to a plurality of coordinate detection periods Td.
1 to Tds, the switch circuit 19 selectively switches the column electrodes one by one (or in units of a plurality) in each coordinate detection period Tde, and M generated by the M-sequence generation circuit 2. Using the series signal m as a row electrode scanning signal,
During each coordinate detection period Tde, the M-sequence signal m is sequentially applied to the row electrodes while changing the phase, and the difference between the voltage induced on the selected column electrode and the basic pattern V (t) is detected. This is a configuration for performing a correlation operation between the detected voltage and the M-sequence signal m.

As described above, by using the M-sequence signal m whose potential constantly changes as a scanning signal and performing a correlation operation at the time of coordinate detection, the signal energy scattered over time is compressed and collected at one point. be able to. In other words, the energy density of the signal increases. At this time, there is an effect that time-dispersed signal energies are collected for necessary detection signals, and signal energy is not collected for other interfering signals such as random noise. Can be improved.

As a result, the row electrodes can be driven with a low power supply voltage. This makes it possible to meet the demand for lowering the voltage as the coordinate input device becomes more portable. In addition, for liquid crystal panels, plasma displays, and EL (electroluminescence) panels having thin row electrodes and column electrodes having a high optical aperture ratio,
It is possible to provide a coordinate input device capable of detecting coordinates that can withstand practical use.

Further, the coordinate input device of the present embodiment can detect the position coordinates specified by the plurality of pointers 8 as described above, and provide a coordinate input device corresponding to various applications. Can be.

In the case of a coordinate input device having only a coordinate input function instead of a display-integrated type coordinate input device as described below, operation is possible even if the column electrode drive circuit 3 is omitted.

[Second Embodiment] The following will describe another embodiment of the present invention with reference to FIGS. 26 to 29. For the sake of convenience of explanation, the same members as those shown in the drawings of the above-mentioned embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

The coordinate input device according to this embodiment has a T
This is a display-integrated coordinate input device in which the coordinate input function of Embodiment 1 is added to an FT (thin film transistor) liquid crystal display device, and includes a row electrode (gate electrode) group, a column electrode (source electrode) group, and a row of a TFT liquid crystal panel. The electrode drive circuit and the column electrode drive circuit are shared.

In the coordinate input device of the present embodiment, as shown in FIG. 26, the coordinate input panel substrate 5 of the first embodiment is replaced with a TFT liquid crystal display panel (display panel) 5 'and a display control circuit. (Display control means) 201 and a switching circuit (output switching means) 202 are added.

The above-mentioned TFT liquid crystal display panel 5 ′ comprises a transparent TFT substrate 203, a counter substrate 205, and a counter substrate 2.
05 is formed on the transparent counter electrode 204. On the counter electrode 204 side of the TFT substrate 203, a row electrode group 7 and a column electrode group 6 are arranged so as to intersect each other, and a TFT (switching element) 206 is arranged at the intersection. Each TFT 206 has a gate connected to a row electrode, a source connected to a column electrode, and a drain connected to a pixel electrode 207. The column electrode group 6 is connected to the column electrode drive circuit 3, and the row electrode group 7 is connected to the row electrode drive circuit 4. The pixel electrode 207 and the counter electrode 20
Liquid crystal is sealed between the liquid crystal display device 4 and the liquid crystal display device 4.

The display control circuit 201 converts display data output from the information processing device 20 into control signals and image data for driving the TFT liquid crystal display panel 5 'as a display device. The display control circuit 201 is connected to one input terminal of the switching circuit 202, and supplies an output of the display control circuit 201 to the row electrode drive circuit 4 and the column electrode drive circuit 3 during a display period Tdsp described later. The M-sequence generation circuit 2 is connected to the other input terminal of the switching circuit 202, and supplies the output of the M-sequence generation circuit 2 to the row electrode drive circuit 4 during the total coordinate detection period Td.

FIG. 27 is a timing chart showing the operation of FIG. It is to be noted that the method of driving the display of the TFT liquid crystal display device in the display period Tdsp is well known, and the display operation is omitted.

The system operation cycle Tc, which is the operation cycle of the entire system, includes a display period Tdsp and the above-described total coordinate detection period Td. System operation cycle T
c is determined based on the vertical synchronization signal Vd, and the display period Tdsp and the coordinate detection period Td are determined based on the detection period signal det. During the display period Tdsp, the TFT liquid crystal display panel 5 'enters the display operation mode, and the total coordinate detection period Td
, The TFT liquid crystal display panel 5 'operates as a coordinate input device. The total coordinate detection period Td is the same as in the first embodiment, and the individual finger coordinate detection period Tde (e = 1 to
s) is divided into s.

Here, in order to make the display function and the coordinate input function compatible in the TFT liquid crystal display panel 5 ', it is necessary to devise the voltage applied to the TFT 206 as described below.

FIG. 29 shows operation waveforms in the display period Tdsp. In the display period Tdsp, a voltage corresponding to the display luminance for one column is applied to the TFT 206 by the column electrode S1. At the same time, the row electrodes G1 to Gm are sequentially scanned in the row direction in synchronization with the horizontal clock signal ch.
As a result, the TFT 206 connected to each row electrode becomes
When the voltage becomes N, the voltage corresponding to the display data of the column electrode S1 is charged to the liquid crystal via the pixel electrode 207. Note that FIG.
In 9, the pixel electrode P1m means the pixel electrode in the first column and m-th row. In this way, charging of all the pixels is completed. The same applies to other column electrodes S2 to Sn other than the column electrode S1.

FIG. 28 shows the drain current versus gate voltage characteristics of the TFT 206. −Vf0 and −Vf1 are gate voltages at which cutoff is performed, and Vn is a gate voltage at the time of ON. As described above, when the row electrode group 7 is sequentially scanned during the display period Tdsp, the charging corresponding to the display data to all the pixels is completed. In the total coordinate detection period Td after the display period Tdsp, if the gate of the TFT 206 has Vn
Is applied, the TFT 206 is turned on. On the other hand, when -Vf0 or -Vf1 is applied to the gate, the TFT 206 is turned on.
Turns off at 6.

In the total coordinate detection period Td, the indicator 8
Is applied to the row electrode group 7 to detect the coordinates indicated by the TFT 20. At this time, the TFT 20
The potential must be determined so that 6 does not turn on.
This is because if the TFT 206
Is turned on, the charges corresponding to the image data charged in the pixels during the display period Tdsp are lost by discharging. Therefore, in the total coordinate detection period Td, all the column electrode groups 6 are set to 0 V, and the potential of the row electrode group 7 is set to (for example, V0 and V1 in FIG. 14) -Vf.
When 0 and -Vf1 are selected, the row electrode group 7 can be scanned without turning on the TFT 206.

According to the above configuration, the total coordinate detection period Td
, An induced voltage is induced in the column electrode group 6 due to the M-sequence signal m applied to the row electrode group 7. Detection circuit 10
Calculates the correlation between these detection signals and the M-sequence signal m, removes noise with an appropriate LPF 14, and detects the indicated coordinates of an indicator 8 such as a finger or a cordless pen having a metal case at the tip.

The coordinate values detected as described above are input to the information processing device 20. At this time, the information processing device 20 generates display data for displaying a point image at the tip position of the indicator 8 on the TFT liquid crystal display panel 5 ′ based on the coordinate values, and outputs the display data to the display control circuit 201. I do. The display control circuit 201 generates a display control signal and image data based on the display data. After the end of the total coordinate detection period Td, the switching circuit 202 selects the display control circuit 201 based on the detection period signal det generated by the timing generation circuit 1, and the control signal and the image data generated by the display control circuit 201 are Column electrode drive circuit 3
And to the row electrode drive circuit 4. The operation of the column electrode driving circuit 3 and the row electrode driving circuit 4 causes the TF
A point image is displayed at the tip position of the indicator 8 on the T liquid crystal display panel 5 '.

In this embodiment, the control means according to claim 2 is constituted by the timing generation circuit 1.

As described above, the display-integrated coordinate input device according to the present embodiment is configured to perform the coordinate detection by applying the correlation detection method based on the M-sequence signal and to have a display function. At this time, a high S /
Since N can be obtained, it is possible to increase the detection accuracy and the detection speed. Therefore, the total coordinate detection period Td can be set relatively short, and the display is not affected. Further, by performing display and coordinate detection in a time-sharing manner, the structure and the drive circuit of the display device are commonly used with those for coordinate detection, so that the configuration can be simplified. As a result, it is possible to provide a display-integrated coordinate input device that has high transmittance, good visibility, is lightweight, thin, and inexpensive.

In the case of the above-mentioned TFT liquid crystal display panel 5 ', it is usual that the area of the column electrode group 6 and the row electrode group 7 is extremely reduced to increase the aperture ratio, and the coordinate detection signal becomes extremely large. Become smaller. However, the coordinate input device according to the present embodiment can obtain a highly accurate detection signal even with a low voltage drive by detecting the correlation using the M-sequence signal.

In the present embodiment, as described above, the information of the basic pattern V (t) is stored in advance in the memory incorporated in the basic pattern generation circuit 17, and the information is read out to store the basic pattern V (t). A configuration for generating the pattern V (t) may be used, but the present invention is not limited to this. For example, the counter electrode 2 of the TFT liquid crystal display panel 5 '
A signal obtained by appropriately amplifying the voltage induced in the voltage 04 may be input to the differential amplifier circuit 11 in the detection circuit 10 as the basic pattern V (t). This is because the reduction in the induced voltage caused by placing the indicator 8 such as a finger on the TFT liquid crystal display panel 5 'is slight, and if the induced voltage is picked up by the counter electrode 204 having a sufficiently large area, the basic pattern V (t ) Is induced.

In this embodiment, the liquid crystal display panel is described as an example of a TFT liquid crystal panel. However, the present invention is not limited to this, and other liquid crystal display panels such as an STN liquid crystal panel and an MIM type liquid crystal panel, or Not only liquid crystal display panels, but also EL panels, plasma displays, etc.
The coordinate input device according to the present embodiment can be applied.
In other words, a configuration in which an electrode group for applying a voltage for display and a shift register for driving the electrode group can be shared for display and coordinate input uses a correlation detection method based on an M-sequence signal as described above. Can be applied.

For example, in the case of the duty type liquid crystal driving, a transparent substrate provided with a column electrode group and a transparent substrate provided opposed to the transparent substrate and provided with a row electrode group are provided. The liquid crystal is interposed between the substrates, and the optical properties of the liquid crystal are controlled by the effective applied voltage of the column electrode group and the row electrode group. According to this configuration, a pixel is formed in a region where the row and column electrode groups intersect. Then, while the column electrode group is activated to select a row of the pixel matrix, a signal corresponding to the display data is output to the row electrode group, whereby liquid crystal display is performed.

In such a duty type liquid crystal,
Usually, in order to increase the aperture ratio of display, it is usual to make the area where the column electrode group and the row electrode group intersect and interpose the liquid crystal as large as possible. Although the coupling is large with the adjacent front-side electrode group, the coupling on the opposite side is very small because the coupling is made through the gap of the front-side electrode group. However, even in this case, the coordinate input device of the present embodiment is
By the correlation detection using the M-sequence signal, a highly accurate detection signal can be obtained even with a low voltage drive.

Although the first and second embodiments use the M-sequence signal m, the present invention is not limited to this.
Anything may be used as long as the autocorrelation function satisfies the expression (7) and the autocorrelation function is a pulse-like PN sequence (Pseudo random noise). This PN sequence has a binary function and an analog function.

The M sequence described above is composed of “0” and “1”.
Therefore, there is an advantage that the configuration is simple and the circuit scale is small as shown in FIG. As a function of a binary sequence other than the M sequence, there are a Gold sequence, a Barker code, a Frank code, a complementary sequence code, and the like, and these may be used. However, since the M-sequence has characteristics other than τ = 0 and has a good S / N, and the configuration is simple as described above, the M-sequence is more desirable.

Further, a chirp signal and a white noise signal can be used as the analog function. However, when an analog function is used, a drive circuit that can shift an analog voltage is required as the row electrode drive circuit 4. As such a driving circuit, for example,
A configuration in which a buffer amplifier is attached to each tap of the CCD is conceivable. That is, since the CCD has a function of sampling and holding an analog voltage and shifting it, it operates as an analog delay element with an intermediate tap. By connecting a buffer amplifier to each tap of this CCD and applying a voltage buffered by each buffer amplifier to each row electrode, an analog signal such as a white noise signal can be applied to each row electrode while delaying it. .

As described above, when another function satisfying the expression (7) is adopted instead of the M-sequence signal m, the correlation calculator 13 in the detection circuit 10 must be a circuit corresponding to the adopted function. . However, since the correlation calculator 13 is a product-sum operation, it can be easily configured based on FIG. Also in this case, when a binary sequence such as an M sequence is used, the circuit configuration of the correlation calculator 13 is small in circuit scale because the product coefficient is ± 1 and the calculation can be performed at high speed.

In the first and second embodiments, the PN sequence signal such as the M sequence signal m is applied to the row electrode and detected by the column electrode. However, the present invention is not limited to this. Needless to say, a PN series signal such as the M series signal m may be applied to the column electrode and detected by the row electrode.

[0168]

As described above, in the coordinate input device according to the first aspect of the present invention, the first electrode group arranged on the substrate at a predetermined interval and the first electrode group intersect at a predetermined interval. And the second electrode which is insulated and electrostatically coupled with the first electrode group.
An electrode group, second electrode switching means for dividing the coordinate detection period into a plurality of unit periods, and selectively switching one electrode of the second electrode group or a plurality of adjacent electrodes for each unit period; A pseudo-random signal generating means for generating a pulse-like pseudo-random signal, and a first electrode driving means for sequentially applying pseudo-random signals having mutually different phases to each electrode of the first electrode group during each unit period. Means for outputting a basic waveform signal having substantially the same waveform as a voltage waveform induced on one or a plurality of adjacent electrodes of the second electrode group when the pointer does not indicate a coordinate position; Means, a difference extracting means for extracting a difference signal between the detection signal induced at the electrode of the second electrode group selected by the second electrode switching means and the basic waveform signal, and a means for extracting a predetermined value from the difference signal. Beyond that X-coordinate detection means for detecting the x-coordinate from the electrodes of the second electrode group selected by the second electrode switching means when detecting this, and correlates the difference signal with the pseudo-random signal. The configuration includes a correlation detecting means and a Y coordinate detecting means for detecting an extreme value of an output of the correlation detecting means and detecting a y coordinate.

Therefore, each electrode of the first electrode group changes potential at the same time, and by correlating to a slight change in voltage induced by the change, it is equivalent to efficiently collecting energy. Therefore, a good coordinate signal with less noise can be obtained. As a result, even when the distance between the pointer and the coordinate input device is large, and even when scanning is performed at high speed, there is an effect that good coordinate detection accuracy can be obtained. Further, since the electrodes of the second electrode group are switched by the second electrode switching means, a plurality of coordinates can be detected during the coordinate detection period, and simultaneous coordinate input by a plurality of pointers is possible. Is played together.

As described above, in the coordinate input device according to the second aspect of the present invention, the first electrode group arranged at a predetermined interval on the display panel substrate and the first electrode group intersect at the predetermined interval. A second electrode group that is insulated and electrostatically coupled with the first electrode group, a first sequential drive unit that drives the first electrode group, and a second sequential unit that drives the second electrode group Driving means; display control means for generating a display control signal for driving the first and second sequential driving means based on display information corresponding to the detected coordinates; and autocorrelation function generating a pulse-like pseudo-random signal. A pseudo-random signal generating means for selecting the display control signal during a display period, and selecting the pseudo-random signal during a coordinate detection period to time-divisionally output to the first and second sequential driving means. Means,
A second electrode switching unit that divides the coordinate detection period into a plurality of unit periods, and selectively switches one electrode of the second electrode group or a plurality of adjacent electrodes in each unit period; Control means for controlling the first sequential driving means so that pseudo-random signals having different phases are sequentially applied to the respective electrodes of the first electrode group; and A basic waveform output means for outputting a basic waveform signal having substantially the same waveform as a voltage waveform induced on one or a plurality of adjacent electrodes of the two electrode group; and a second electrode selected by the second electrode switching means. A difference extracting means for extracting a difference signal between the detection signal induced at the electrodes of the electrode group and the basic waveform signal, and detecting that the difference signal exceeds a predetermined value, and detecting the difference signal when the second signal is detected. Selected by switching means X-coordinate detection means for detecting the x-coordinate from the electrodes of the second electrode group, correlation detection means for correlating the difference signal with the pseudo-random signal, and obtaining an extreme value of the output of the correlation detection means. and a Y-coordinate detecting means for detecting a y-coordinate.

Therefore, similarly to the first aspect of the present invention, a good coordinate signal with less noise can be obtained, and even if the distance between the pointer and the coordinate input device is large, or if scanning is performed at high speed. It is advantageous in that good coordinate detection accuracy can be obtained and simultaneous coordinate input by a plurality of pointers is possible. Further, since the components of the display function and the coordinate detection function are shared in a time-sharing manner, the display function and the highly accurate coordinate input can be achieved with a simple configuration.

As described above, a coordinate input device according to a third aspect of the present invention is the coordinate input device according to the second aspect of the present invention, wherein the display panel includes a plurality of switching elements connected to the first and second electrode groups. A plurality of pixel electrodes to which the switching element is connected, a transparent pixel electrode in which a plurality of pixel electrodes are arranged in a matrix, and an opposing electrode provided to face the transparent pixel electrode. The liquid crystal display panel controls the optical properties of the liquid crystal sealed between the transparent pixel electrode and the counter electrode.

In this case, even when the areas of the first and second electrode groups are reduced as much as possible in order to increase the aperture ratio of the liquid crystal display panel, highly accurate coordinate detection can be performed even at a low voltage drive by detecting the correlation of the pseudo random signal. It is possible. Therefore,
The application to this type of liquid crystal display panel is very effective.

As described above, in the coordinate input device according to a fourth aspect of the present invention, in the configuration of the second aspect of the present invention, the display panel includes the first electrode group and the second electrode group provided to face each other. The liquid crystal display panel controls the optical properties of the liquid crystal sealed between the first and second electrode groups by an effective applied voltage between the first and second electrode groups.

In this case, the voltage induced in the electrode group located on the back side when viewed from the input surface of the liquid crystal display panel becomes small. However, by detecting the correlation of the pseudo-random signal, the detected energy is effectively collected to obtain good coordinate detection. Is possible. Therefore, there is an effect that application to this type of liquid crystal display panel is very effective.

As described above, the coordinate input device according to the fifth aspect of the present invention has a configuration in which the pseudo random signal is an M-sequence signal in the configuration of the first, second, third or fourth aspect of the present invention. I have.

Therefore, the pseudo-random signal (M-sequence signal) can be generated by the pseudo-random signal generating means having a small circuit scale, and in addition to the effects of claims 1, 2, 3 or 4, The present invention also has an advantage that it is advantageous when configuring a portable coordinate input device that operates at high speed and has low power consumption.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a main part of a coordinate input device according to a first embodiment of the present invention.

FIG. 2 is a timing chart showing an operation of the coordinate input device.

FIG. 3 is an explanatory diagram showing a state of electrostatic coupling between a finger as a pointer and a row electrode and a column electrode.

FIG. 4 is an explanatory diagram showing an electrical connection state when a pointer is not brought close to the coordinate input device.

FIG. 5 is an explanatory diagram showing an electrical connection state when a finger as a pointer is brought close to the coordinate input device.

FIG. 6 is an explanatory diagram showing lines of electric force between a row electrode and a column electrode.

FIG. 7 is an explanatory diagram showing lines of electric force between a finger and a row and column electrode when a finger as a pointer is brought close to the coordinate input device.

FIG. 8 is a graph showing a coupling capacitance characteristic between a column electrode S3 and each row electrode in a Y-axis direction.

FIG. 9 is a graph showing a frequency spectrum of an output of a correlation calculator in the coordinate input device.

FIG. 10 is a graph showing a signal transmission characteristic of an LPF in the coordinate input device.

FIG. 11 is a graph showing a frequency spectrum of the output of the LPF.

FIG. 12 is a circuit diagram illustrating a configuration example of an M-sequence generation circuit in the coordinate input device.

FIG. 13 is a timing chart showing the operation of the M-sequence generation circuit.

FIG. 14 is a circuit diagram showing a configuration example of a row electrode drive circuit in the coordinate input device.

FIG. 15 is a circuit diagram showing a configuration example of a switch circuit in the coordinate input device.

FIG. 16 is a circuit diagram showing a configuration example of a correlation calculator in the coordinate input device.

FIG. 17 is a timing chart showing the operation of the correlation calculator in the case of an ideal detection waveform.

FIG. 18 is a timing chart showing the operation of the correlation calculator in the case of an actual detected waveform including the effect of a spatial low-pass filter.

FIG. 19 is a circuit diagram showing a configuration example when an LPF is an FIR low-pass filter.

FIG. 20 is a timing chart showing the operation of the FIR type low-pass filter.

FIG. 21 is a circuit diagram showing a configuration example of a Y coordinate detection circuit in the coordinate input device.

FIG. 22 is a timing chart showing the operation of the Y coordinate detection circuit.

FIG. 23 is a circuit diagram showing a configuration of a correction circuit in the Y coordinate detection circuit.

FIG. 24 is a circuit diagram showing a configuration of an output circuit in the coordinate input device.

FIG. 25 is a timing chart showing the operation of the output circuit.

FIG. 26 is a block diagram showing a configuration of a main part of a display-integrated coordinate input device according to a second embodiment of the present invention;

FIG. 27 is a timing chart showing the operation of the display-integrated coordinate input device.

FIG. 28 shows a TFT in the display-integrated coordinate input device.
5 is a graph showing drain current vs. gate voltage characteristics of FIG.

FIG. 29 is a timing chart showing a display operation during a display period of the display-integrated coordinate input device.

[Explanation of symbols]

Reference Signs List 1 timing generation circuit (control means) 2 M-sequence generation circuit (pseudo random signal generation means) 3 column electrode drive circuit (first electrode drive means, first sequential drive means) 4 row electrode drive circuit (second sequential drive means) Reference Signs List 5 coordinate input panel substrate (substrate) 5 ′ TFT liquid crystal display panel (display panel) 6 column electrode group (first electrode group) 7 row electrode group (second electrode group) 8 pointer 10 detection circuit 11 differential amplifier circuit ( Difference extracting means) 12 A / D converter 13 Correlation calculator (Correlation detecting means) 14 Low-pass filter 15 Y coordinate detecting circuit (Y coordinate detecting means) 16 Output circuit 17 Basic pattern generating circuit (Basic waveform outputting means) 18 X coordinate Detection circuit (X coordinate detection means) 19 Switch circuit (second electrode switching means) 20 Information processing device 201 Display control circuit (Display control means) 202 Switching circuit Output switching means) 206 TFT (switching element)

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G06F 3/03 335 G06F 3/033 360

Claims (5)

(57) [Claims] 1. A coordinate input device for detecting coordinates on a surface pointed by a conductive indicator and outputting coordinate data, comprising: a first electrode group arranged on a substrate at a predetermined interval; A second electrode group intersected with the electrode group at predetermined intervals and insulated and electrostatically coupled to the first electrode group; dividing the coordinate detection period into a plurality of unit periods; A second electrode switching means for selectively switching the electrodes of the second electrode group one by one or a plurality of adjacent electrodes every time; a pseudo-random signal generating means for generating a pulse-like pseudo-random signal with an autocorrelation function; A first electrode driving means for sequentially applying pseudo-random signals having different phases to each electrode of the first electrode group during each unit period, and a second electrode group when a pointer does not indicate a coordinate position. To one or multiple adjacent electrodes Basic waveform output means for outputting a basic waveform signal having substantially the same waveform as the voltage waveform to be output; a detection signal induced by the electrodes of the second electrode group selected by the second electrode switching means; A difference extracting means for extracting the difference signal of the second electrode group, and detecting that the difference signal has exceeded a predetermined value, and detecting the difference signal from the electrodes of the second electrode group selected by the second electrode switching means when detecting the difference signal. X-coordinate detecting means for detecting coordinates, correlation detecting means for correlating the difference signal with the pseudo-random signal, Y-coordinate detecting means for obtaining an extreme value of an output of the correlation detecting means and detecting a y-coordinate. A coordinate input device comprising: 2. A method for detecting coordinates on a display panel indicated by a conductive indicator during a coordinate detection period, and displaying display information corresponding to the detected coordinates on the display panel by display control during a subsequent display period. A first electrode group arranged at a predetermined interval on a display panel substrate, and the first electrode group intersects with the first electrode group at a predetermined interval. A second electrode group that is insulated and electrostatically coupled to the first electrode group; a first sequential drive unit that drives the first electrode group; a second sequential drive unit that drives the second electrode group; Display control means for generating a display control signal for driving the first and second sequential driving means based on the display information obtained, a pseudo-random signal generating means for generating a pulse-like pseudo-random signal having an autocorrelation function; Displayed above during the display period An output switching unit for selecting a control signal, selecting the pseudo-random signal during the coordinate detection period, and outputting the pseudo-random signal to the first and second sequential driving units, and dividing the coordinate detection period into a plurality of unit periods. A second electrode switching means for selectively switching one or a plurality of adjacent electrodes of the second electrode group in each unit period, and connecting each electrode of the first electrode group to each electrode in each unit period. Control means for controlling the first sequential driving means so that pseudo-random signals having different phases are sequentially applied to one or more of the second electrode group or a plurality of adjacent electrodes when the pointer does not indicate a coordinate position Basic waveform output means for outputting a basic waveform signal having substantially the same waveform as the voltage waveform induced on the unit electrode; detection signals induced on the electrodes of the second electrode group selected by the second electrode switching means; Above basic waveform signal And a difference extracting means for extracting a difference signal between the second electrode group and the second electrode group selected by the second electrode switching means when the difference signal exceeds a predetermined value. X-coordinate detecting means for detecting an x-coordinate, correlation detecting means for correlating the difference signal with the pseudo-random signal, and Y-coordinate detecting means for detecting an extreme value of an output of the correlation detecting means and detecting a y-coordinate And a coordinate input device. 3. The display panel according to claim 1, wherein the plurality of switching elements connected to the first and second electrode groups, and a plurality of pixel electrodes to which the switching elements are connected are arranged in a matrix. A liquid crystal display panel comprising: a counter electrode provided to face the transparent pixel electrode; and driving the switching element to control optical properties of liquid crystal sealed between the transparent pixel electrode and the counter electrode. The coordinate input device according to claim 2, wherein 4. The display panel according to claim 1, wherein the optical property of the liquid crystal sealed between the first electrode group and the second electrode group provided opposite each other is determined by the first electrode group and the second electrode group. 3. The coordinate input device according to claim 2, wherein the coordinate input device is a liquid crystal display panel controlled by an effective applied voltage during the period. 5. The coordinate input device according to claim 1, wherein said pseudo random signal is an M-sequence signal.