JPH04337825A - Coordinate input device - Google Patents

Abstract

PURPOSE:To obtain a coordinate input device where the number of parts can be reduced, position detection time becomes short and versatility is enlarged. CONSTITUTION:A position detection control circuit 6 is provided with ROM 130 storing control data for controlling an electrode driving circuit in a position detection period, generates and outputs a control signal controlling the electrode driving circuit based on control data. Thus, the device can correspond to various kinds of the electrode driving circuits by setting and altering stored data in ROM 130 in accordance with the electrode driving circuit. Thus, the number of the parts in the coordinate input device can be reduced, a position detection period becomes short, the device can correspond to various liquid crystal panels and the electrode driving circuits, a use range and versatility are enlarged.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coordinate input device such as a so-called tablet used for inputting characters, figures, etc. into a personal computer, word processor, or the like.

0002

[Prior Art] As a means of inputting handwritten characters and figures into computers, word processors, etc., a liquid crystal display and an electrostatic induction tablet are combined, and characters and figures input to the electrostatic induction tablet can be inputted by an operator. Input devices have been put into practical use that allow input to feel like writing with a writing utensil on paper and display the information on a liquid crystal display.

However, in the case of this electrostatic induction tablet, the reflectance and transmittance are different between the parts with and without transparent electrodes in the coordinate input section, so the electrodes are visible in a grid pattern on the display screen, and the liquid crystal display This causes a drop in quality.

[0004] Therefore, a so-called display-integrated tablet as shown in FIG. 7 has been proposed as a tablet that overcomes these drawbacks.

[0005] In this display-integrated tablet, the display electrode of the liquid crystal display also serves as a position detection electrode, and position detection and display are performed in a time-sharing manner.

In FIG. 7, the liquid crystal panel 21 includes common electrodes Y1 to Y80 (generally referred to as Y) arranged in directions crossing each other, and segment electrodes X1 to X80.
(generally referred to as X), a liquid crystal layer is interposed between the common electrodes Y and the segment electrodes X, and the liquid crystal layer at the intersection of each common electrode Y and segment electrode X forms each pixel. That is, in the liquid crystal panel 1, pixels of 80×80 dots are arranged in a matrix.

[0007] This display-integrated tablet has the advantage that the grid-like electrode pattern is no longer visible compared to the tablet placed on the liquid crystal display, making it easier to see. This has the advantage of reducing costs and making it easier to reduce the size and weight.

The common drive circuit 22 for driving the common electrode Y and the segment drive circuit 23 for driving the segment electrode X are connected to a display control circuit 25 and a position detection control circuit via a switching circuit 24. 26. This switching circuit 24 is switched and controlled by a control circuit 27, outputs the output from the display control circuit 25 to the drive circuits 22 and 23 during the display period, and drives the output from the position detection control circuit 26 during the position detection period. Output to circuits 22 and 23.

During the display period, the display control circuit 25
Start signal S, inverted signal M, clocks CP1, CP2
, and output display data D0 to D3, respectively. The clock CP1 is a clock whose cycle is a scanning period for scanning one row of pixels, and is input to the common drive circuit 22 and the segment drive circuit 23 via the switching circuit 24. Further, the start signal S is a signal indicating the start of a scanning period for displaying the common electrode Y, and is outputted via the switching circuit 24 and inputted to the common drive circuit 22 in synchronization with the clock CP1.

In response to the shift of the clock CP1, a drive signal is outputted to the common electrode Y from the output terminal of the common drive circuit 22 corresponding to the shift position. This drive signal is a bias voltage V0 to V0 supplied from the power supply circuit 32.
Created based on V5. The clock CP2 is a clock whose period is a period obtained by dividing a scanning period for scanning one column of pixels into a plurality of periods, and is outputted via the switching circuit 24 and inputted to the segment drive circuit 23.

The display data D0 to D3 are outputted via the switching circuit 24 and inputted to the segment drive circuit 23.
The data are sequentially taken into registers inside the segment drive circuit 23. When display data corresponding to one row of pixels is captured, these display data are latched at the timing of the clock CP1, and drive signals corresponding to each display data are sent from the output terminal of the segment drive circuit 23 to the segment electrodes. Output to X. This drive signal is also created based on bias voltages V0 to V5 supplied from the power supply circuit 32. Note that the inversion signal M is a signal for periodically inverting the polarity of the voltage applied to the liquid crystal to prevent deterioration of the liquid crystal due to electrolysis.

By the operations of the common drive circuit 22 and the segment drive circuit 23, the pixels of the liquid crystal panel 21 are driven in accordance with their row order, and an image corresponding to display data is displayed on the liquid crystal panel 21.

On the other hand, during the position detection period, the position detection control circuit 26 receives the start signal Sd, the inverted signal Md, the clocks CP1d and CP2d, and the drive data D0d to D3d.
Output each. The clock CP1d is a clock whose cycle is a scanning period for scanning one row of common electrodes Y, and is input to the common drive circuit 22 and the segment drive circuit 23 via the switching circuit 24. Further, the start signal Sd is a signal instructing the start of scanning of the common electrode Y, and is outputted via the switching circuit 24 and inputted to the common drive circuit 22 in synchronization with the clock CP1d.

In response to the shift of the clock CP1d,
A scanning signal is output to the common electrode Y from the output terminal of the common drive circuit 22 corresponding to the shift position. This scanning signal is a bias voltage V0 supplied from the power supply circuit 32.
~Created based on V5.

The clock CP2d is a clock whose period is equal to the scanning period for scanning one column of segment electrodes X, and is output from the switching circuit 24 to
3 is input.

The drive data D0d to D3d are transferred to the switching circuit 2.
4, is input to the segment drive circuit 23, and is sequentially taken into a register inside the segment drive circuit 23. When drive data corresponding to one row of segment electrodes It is input to segment electrode X. This drive signal also
It is created based on bias voltages V0 to V5 supplied from the power supply circuit 32. Note that the inversion signal Md is a signal for periodically inverting the polarity of the voltage applied to the liquid crystal to prevent deterioration of the liquid crystal due to electrolysis.

When a position detection pen (hereinafter simply referred to as detection pen) 28 is brought close to the surface of the liquid crystal panel 21, a gap between the electrode provided at the tip of the detection pen 28 and the electrodes X and Y to which a voltage is applied is detected. Due to the stray capacitance of the detection pen 28
A voltage is induced in the electrode. The voltage induced in the detection pen 28 is amplified by an amplifier 29 and applied to an X coordinate detection circuit 30 and a Y coordinate detection circuit 31. The X-coordinate detection circuit 30 and the Y-coordinate detection circuit 31 calculate the X-coordinate and Y-coordinate, respectively, based on the generation timing of the induced voltage of the detection pen 28 and the timing signal from the control circuit 27.

[0018]

[Problems to be Solved by the Invention] In the above-mentioned so-called display-integrated tablet, the common drive circuit 22 and the segment drive circuit 23 are used in common during the display period and the position detection period, but they are originally drive circuits for display control. Since the position detection control circuit 26 is used as a controller and has inferior functions for position detection control, it is necessary to add a wide variety of circuits to the position detection control circuit 26 in order to be compatible with different types of display drive circuits.

For example, in FIG. 7, during the display period, the segment drive circuit 23 has an output control section for 80 pixels, and input data D0 to D3 are sent to specified segment electrodes (pixels) in synchronization with the clock CP2. shift. Further, the clock CP1 latches the shift data and outputs the data to each segment electrode X1 to X80. At this time, if the number of pixels is 80 or more,
It has an enable terminal that can be used by connecting segment drive circuits 23 in cascade.

The common drive circuit 22 also has an output control section for 80 pixels, and the common electrode Y corresponding to the clock CP1 is selected. It also has terminals to which start signals S and Sd for instructing the start of scanning are applied from the electrode Y1, which is the leading electrode.

That is, each pixel associated with the common electrode Yn selected by the common electrode drive signal from the common drive circuit 22 is displayed by the segment electrode drive signal output from the segment drive circuit 23 in accordance with display data.

On the other hand, during the position detection period, the segment drive circuit 22 (X-coordinate side) cannot perform a pixel-by-pixel shift operation, and it is necessary to write display data for 80 pixels. cannot be shortened.

In addition, the position detection control circuit 26 requires a wide variety of additional circuits in order to be compatible with various drive circuits, which is undesirable from the standpoint of reducing the number of parts.

An object of the present invention is to solve the above technical problems, to reduce the number of parts and to shorten the position detection period.
It is another object of the present invention to provide a coordinate input device whose versatility is further expanded.

[0025]

[Means for Solving the Problems] The present invention provides a liquid crystal panel configured by interposing a liquid crystal layer between a plurality of segment electrodes and a plurality of common electrodes that are orthogonal to each other, and a liquid crystal panel that drives the segment electrodes and the common electrode. an electrode driving means; a display control means for controlling the electrode driving means to display an image on a liquid crystal panel during a display period; a position detection pen electrostatically coupled to the segment electrode and the common electrode; a position detection control means for sequentially applying a scanning voltage by controlling the electrode drive means during a set position detection period; and based on the induced voltage induced in the position detection pen and the application timing of the scanning voltage to the electrodes. In the coordinate input device, the position detection control means includes a storage means for storing control data for controlling the electrode driving means during the position detection period, and the position detection control means includes a storage means for storing control data for controlling the electrode drive means during the position detection period, and This coordinate input device is characterized in that it creates and outputs a control signal for controlling an electrode driving means.

[0026]

[Operation] According to the present invention, the position detection control means includes a storage means for storing control data for controlling the electrode drive means during the position detection period, and controls for controlling the electrode drive means based on the control data. Create and output signals. Therefore, by changing the settings of the data stored in the storage means in accordance with the electrode driving means, it becomes possible to correspond to various electrode driving circuits.

[0027]

Embodiment FIG. 1 is a block diagram showing the basic configuration of a position detection control circuit 6 which is an embodiment of the present invention, and FIG. 2 is a block diagram showing the configuration of a coordinate input device using the position detection control circuit 6. It is.

In FIG. 2, the liquid crystal panel 1 includes common electrodes Y1 to Y80 (generally referred to as Y) arranged in directions crossing each other, and segment electrodes X1 to X80 (generally referred to as Y).
(When collectively referred to as X), a liquid crystal layer is interposed between each common electrode Y and segment electrode X.
The portion of the liquid crystal layer where these intersect with each other constitutes each pixel. That is, in the liquid crystal panel 1, pixels of 80×80 dots are arranged in a matrix.

[0029] Compared to a tablet placed on a liquid crystal display, this display-integrated tablet has the advantage that the grid-like electrode pattern is no longer visible and is easier to see. This has the advantage of reducing costs and making it easier to reduce the size and weight.

The common drive circuit 2 for driving the common electrode Y and the segment drive circuit 3 for driving the segment electrode X are connected to a position detection control circuit 6. This position detection control circuit 6 is controlled by a control circuit 7, and outputs a signal for display control to the drive circuits 2 and 3 during the display period, and outputs a signal for position detection to the drive circuit 2 and 3 during the position detection period. , 3.

During the display period, the position detection control circuit 6 receives the start signal S, the inverted signal M, and the clocks CP1 and CP1.
2. Output display data D0 to D3, respectively. The clock CP1 is a clock whose cycle is a scanning period for scanning one row of pixels, and is input to the common drive circuit 2 and the segment drive circuit 3. Further, the start signal S is a signal instructing the start of scanning of the common electrode Y, and is input to the common drive circuit 2 in synchronization with the clock CP1.

In response to the shift of the clock CP1, a drive signal is outputted to the common electrode Y from the output terminal of the common drive circuit 2 corresponding to the shift position. This drive signal is a bias voltage V0 to V supplied from the power supply circuit 12.
5. The clock CP2 is a clock whose cycle is a period obtained by dividing a scanning period for scanning one column of pixels into a plurality of periods, and is input to the segment drive circuit 3.

Display data D0 to D3 are input to the segment drive circuit 3 and are sequentially taken into registers inside the segment drive circuit 3. When display data corresponding to one row of pixels is captured, these display data are latched at the timing of the clock CP1, and drive signals corresponding to each display data are sent from the output terminal of the segment drive circuit 3 to the segment electrodes. Output to Y. This drive signal is also created based on bias voltages V0 to V5 supplied from the power supply circuit 12. Note that the inversion signal M is a signal for periodically inverting the polarity of the voltage applied to the liquid crystal to prevent deterioration of the liquid crystal due to electrolysis.

By the operations of the common drive circuit 2 and the segment drive circuit 3, the pixels of the liquid crystal panel 1 are driven in accordance with their row order, and an image corresponding to display data is displayed on the liquid crystal panel 1.

On the other hand, during the position detection period, the position detection control circuit 6 receives the start signal Sd, the inverted signal Md, and the clock C.
It outputs P1d, CP2d, and drive data D0d to D3d, respectively. The clock CP1d is a clock whose cycle is a scanning period for scanning one row of common electrodes Y, and is input to the common drive circuit 2 and the segment drive circuit 3. Further, the start signal Sd is a signal instructing the start of scanning of the common electrode Y, and is input to the common drive circuit 2 in synchronization with the clock CP1d. Said CP1
According to the shift of d, a scanning signal is outputted to the common electrode Y from the output terminal of the common drive circuit 2 corresponding to the shift position. This scanning signal is created based on bias voltages V0 to V5 supplied from the power supply circuit 12.

The clock CP2d is a clock whose cycle is equal to the scanning period for scanning one column of segment electrodes X, and is input to the segment drive circuit 3.

Drive data D0d to D3d are input to the segment drive circuit 3 and are sequentially taken into registers inside the segment drive circuit 3. When drive data corresponding to one row of segment electrodes X is taken in, the clock CP
At timing 1d, these drive data are latched, and a drive signal corresponding to each drive data is input to the segment electrode X from the output terminal of the segment drive circuit 3. This drive signal is also created based on bias voltages V0 to V5 supplied from the power supply circuit 12. Note that the inversion signal Md is a signal for periodically inverting the polarity of the voltage applied to the liquid crystal to prevent deterioration of the liquid crystal due to electrolysis.

A position detection pen (
When the detection pen 8 (hereinafter simply referred to as detection pen 8) is brought close, a voltage is induced in the electrode of the detection pen 8 due to the stray capacitance between the electrode provided at the tip of the detection pen 8 and the electrodes X and Y to which voltage is applied. do. The voltage induced in the detection pen 8 is amplified by an amplifier 9 and applied to an X coordinate detection circuit 10 and a Y coordinate detection circuit 11. The X-coordinate detection circuit 10 and the Y-coordinate detection circuit 11 calculate the X-coordinate and Y-coordinate, respectively, based on the generation timing of the induced voltage of the detection pen 8 and the timing signal from the control circuit 7.

In FIG. 1, a display period determining circuit 100 is a circuit that determines a common line for a liquid crystal display period.
For example, in the case of a liquid crystal panel having pixels of 640×400 dots, “400” is set. This common line setting operation is performed based on the common electrode start signal S and the common electrode shift clock CP1, and each signal S and CP1 is applied to one input of the multiplexer 160.

The detection period determination circuit 110 is a circuit that determines a position detection period, and this position detection period differs depending on the type of driving circuit of the liquid crystal panel. This position detection period is determined based on the shift clock CP2 and clock CP1 of the segment data, and this shift clock C
P2 is applied to one input of multiplexer 160.

Address generation circuit 120 generates an address signal to ROM 130 during the position detection period. R
The OM 130 stores various signals necessary for processing the induced voltage (position information) induced in the detection pen 8 and data for control signals of the drive circuits 2 and 3, and stores data for control signals of the drive circuits 2 and 3.
The stored data is output to the latch circuit 140 according to the address signal from the latch circuit 140 .

The latch circuit 140 holds the output signal from the ROM 130 using the clock CP2, and its outputs Sd, C
P1d and CP2d are given as the other input of multiplexer 160. The decoder 150 generates a selection signal for each drive circuit during the position detection period when a plurality of segment drive circuits 3 are connected in cascade. Output signals CAS0d to CAS7d from decoder 150
is given as the other input of multiplexer 160.

The multiplexer 160 outputs various signals to the liquid crystal panel 1 by switching between one input and the other input during the display period and the position detection period. On the other hand, the inputs are signals S, CP1, CP2, M, D0 to D3, CAS0 to CA
S7, and the other inputs are signals Sd, CP1d, CP2d
, Md, D0d to D3d, and CAS0d to CAS7d.

FIG. 3 is a timing chart showing the operation of the position detection control circuit 6. The display period is set by counting the shift clock CP1 from the common electrode start signal S. Further, the position detection period is the period from the end of the display period to the next common electrode start signal S, and includes a segment clear period and a segment reading period (X
It has three periods: a coordinate reading period) and a common reading period (Y coordinate reading period).

The position detection period is set by counting the clocks CP2 and CP1 (only the clock CP1 is used in the common reading period) for each of the three periods mentioned above. In the case of a 640×400 dot liquid crystal panel, each of the three periods is set according to Table 1 below.

[0046]

[Table 1]

Here, the segment read period is a total of 20 clocks for the shift clock for writing to the selected drive circuit, 1 clock for the latch clock, 5 clocks for writing to the next stage, and 1 clock for the latch clock. 26
clock is required, and this segment reading period is 1
Five times are required for the drive circuit, and eight drive circuits are required for 400 pixels.

On the other hand, one line in the display period has 640
/4+1=161 clocks are required, so 1461
/161=9 (lines), and the liquid crystal display in this case has a duty of 1/409.

FIG. 4 is a flowchart illustrating the operation of the position detection circuit 6. In step a1, since the segment data (display data) selected by the final common electrode in the display period remains in the segment drive circuit 3,
Clear this data. In step a2, shift data (start signal) S for X coordinate detection and shift clock CP1 are written in accordance with an example of the data format shown in FIG. In the following step a3, a latch clock for outputting the data written in step a2 to the segment electrodes X is written. In step a4,
Determine whether writing of all segment data has been completed, and if not, step a2 and step a
Repeat step 3. Here, if writing has been completed, the process advances to step a5.

In step a5, all segment data is cleared as in step a1. In step a6, common data (start signal) S for Y coordinate detection is written. In step a7, the shift clock of the common data written in step a6 is written, for example, 400 times in the common embodiment. As a result, an induced voltage (position information) as shown in FIG. 6 is obtained in the detection pen 8.

As described above, according to this embodiment, the ROM 130 included in the position detection control circuit 6 secures various signals necessary for detecting position information induced in the detection pen 8 as data, and this stored data Drive circuit 2, 3 based on
Create and output a control signal to control. therefore,
It can be used with a wide variety of drive circuits, and the number of parts can be reduced. Furthermore, the position detection period can be shortened by the program set in the ROM 130.

[0052]

As described above, according to the present invention, the position detection control means includes a storage means for storing control data for controlling the electrode drive means during the position detection period, and the position detection control means includes a storage means for storing control data for controlling the electrode drive means during the position detection period. Create and output a control signal to control the driving means. Therefore, corresponding to the electrode driving means,
By changing the settings of the data stored in the storage means, it becomes possible to correspond to various electrode drive circuits. This makes it possible to reduce the number of parts of the coordinate input device, shorten the position detection period, and also make it compatible with various liquid crystal panels and electrode drive means, greatly expanding the range of use and versatility.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing the configuration of a position detection control circuit 6 that is an embodiment of the present invention.

FIG. 2 is a block diagram showing the basic configuration of a display-integrated coordinate input device.

3 is a timing chart showing the operation of the position detection control circuit 6 shown in FIG. 1. FIG.

FIG. 4 is a flowchart illustrating the operation of the position detection control circuit 6. FIG.

FIG. 5 is a diagram showing an example of a data format of the ROM 130.

6 is a waveform diagram showing the waveform of a detection signal that is position information obtained from the detection pen 8. FIG.

FIG. 7 is a block diagram showing the configuration of a conventional display-integrated coordinate input device.

[Explanation of symbols]

1.LCD panel 2 Common drive circuit 3 Segment drive circuit 5 Display control circuit 6 Position detection control circuit 8 Position detection pen 100 Display period determination circuit 110 Detection period detection circuit 120 Address generation circuit 130 ROM 140 Latch circuit 150 decoder 160 multiplexer X segment electrode Y Common electrode

Claims (1)

[Claims] 1. A liquid crystal panel comprising a liquid crystal layer interposed between a plurality of segment electrodes and a plurality of common electrodes that are orthogonal to each other, an electrode driving means for driving the segment electrodes and the common electrode, and a display period. a display control means that controls the electrode drive means to display an image on the liquid crystal panel; a position detection pen that electrostatically couples with the segment electrodes and the common electrode; a position detection control means that controls the drive means and sequentially applies a scanning voltage; and a coordinate calculation means that calculates coordinates based on the induced voltage induced in the position detection pen and the timing of application of the scanning voltage to the electrodes. In the coordinate input device, the position detection control means includes a storage means for storing control data for controlling the electrode drive means during the position detection period, and controls for controlling the electrode drive means based on the control data. A coordinate input device characterized by creating and outputting a signal.