JPH0247767B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a tablet input device, and more particularly to a tablet input device for inputting coordinates by detecting the timing of a scanning pulse applied to the tablet.

[Prior art and its problems]

Tablet input devices are easy to operate and are inexpensive, allowing them to be used for inputting character/graphic data and item data.
In recent years, it has been widely used for magazine editing, inventory management, etc. The operation of this tablet input device is, for example, in the case of a scanning pulse type, the tablet (input panel surface)
A scanning pulse is sequentially applied to the X electrodes and the Y electrode group arranged in two orthogonal directions, the scanning pulse is detected by the input pen that is in contact with the tablet, and the contact of the input pen is detected from that timing. The system allows you to input coordinate information about the body part.

Specifically, as shown in FIG. 1, an insulating substrate 1A (third,
n electrodes X ₁ to X _o and
Y ₁ to Y _o are arranged, and these X electrode groups,
X and Y electrode drive circuits 2 and 3 that sequentially apply scanning pulses are connected to one end of the Y electrode group.

In order to specify characters, the input pen 4 operated by the operator has a built-in pen switch 4A that is activated by contact with the tablet 1. When the pen switch 4A is closed, the control circuit 5 is activated and a counter 7 connected to an oscillator 6 starts counting. This counter 7
The count value is sent to the aforementioned X (or Y) electrode drive circuit 2 (or 3) every cycle via the gate 8 controlled by the control circuit 5. And this X
(or Y) The electrode drive circuit 2 (or 3) converts the sign of the count value sent from the counter 7 and applies a scanning pulse to each electrode in the tablet 1 (see FIG. 2).

On the character sheet 15 at the intersection of each X electrode and Y electrode, a key segment KS (third
) is provided, and when a scanning pulse is applied to the electrode related to the key segment KS in contact with the input pen 4, the input pen 4 and the tablet 1
The scanning pulse is detected by capacitive coupling with the scanning pulse. After this detection signal is amplified by an amplifier 9 connected to the output side of the input pen 4, it is sent to a gate 12 via a comparator 10 and a shaping circuit 11 for selecting the maximum level signal.

The comparator 10 passes only a detection signal equal to or higher than a predetermined threshold level set by a semi-fixed resistor R in order to prevent scanning pulses related to adjacent key segments KS from being detected, and the input pen 4
It has a function to select detection signals related to key segment KS specified by .

The control circuit 5 controls the gate 12 when the input pen 4 is brought into contact with the tablet 1 and the pen switch 4A is closed.
The latch circuit 13 is the main part of the coordinate information generating section.
When the detection pulse is input from the shaping circuit 11, the gate 12 is switched to the comparator 14 side.

Therefore, first, during one cycle of scanning of one electrode group, a detection signal exceeding the threshold value is inputted to the latch circuit 13 as a latch STB signal. This latch circuit 13 is a latch circuit.
When the STB signal is input, the count value of the counter 7 at that timing is latched. This count value represents the position of the electrode to which the scanning pulse was applied, ie, the coordinates of the key segment KS with which the input pen 4 came into contact.

When one period of scanning of one electrode group is completed,
Next, a data check operation begins. That is, by the action of the control circuit 5, the scanning pulse is once again applied to the aforementioned electrode group, and the detection signal exceeding the threshold level is sent to the comparator 14 via the gate 12 in the same manner as described above.

When the detection signal is input, the comparator 14 compares the count value of the counter 7 at that timing with the latch data of the latch circuit 13, and when they match, outputs a match signal. Therefore,
The output data of the latch circuit 13 when a matching signal is sent out from the comparator 14 is sent out as correct coordinate information free from the influence of noise and the like. By code-exchanging the x, y coordinate information output in this way, character information specified by the input pen 4 can be obtained.

By the way, conventionally, the threshold value SO of the comparator 10
is the amplified detection signal level ai, ai+1 (ai= ai + 1) as a reference (see SO in Figure 5). In actual operator operation, either key segment
I lean toward KS. Therefore, ai＞SO＞ai+1 or ai
Since <SO<ai+1, a detection signal equal to or higher than the threshold value SO is detected as the maximum level detection signal related to the electrode closest to the input pen 4, that is, the key segment KS that the input pen 4 is in contact with. I was getting used to it.

However, in the above-mentioned conventional technology, in order to make function keys etc. easier to see on the character sheet 15, enlarged key segments LKS (third
(see figure), the expanded key segment
Pen-touching on LKS is often done at the center position between the electrodes (see P2 in Figure 3). in this case,
Since the detection signal level due to the scanning pulse applied to both electrodes is equal to the threshold value SO, there is a drawback that no output is made from the comparator 11, making it impossible to input coordinates.

In addition, the threshold SO itself is subject to variations in products and changes in environmental conditions, so it is extremely difficult to set it to an ideal state using the semi-fixed resistor R mentioned above, and the threshold SO may fluctuate for some reason. If the position is shifted vertically, there is a risk that coordinate input will not be possible near the center between the electrodes in the enlarged key segment LKS. For example, as the threshold value increases, the
As shown in SU, the detection signal is no longer obtained,
On the other hand, when the threshold value is lowered, two or more detection signals can be obtained in one scanning period, as shown in SD in the same figure.
The comparator 14 cannot find a match, making it impossible to input coordinates.

[Purpose of the invention]

The present invention has been made in view of the drawbacks of the prior art, and it changes the wave height of the scanning pulse in stages, and even if two detection signals of the maximum level are obtained in one scan, they cannot be selected. By eliminating undetectable areas within the enlarged key segment, the character sheet can be freely laid out, and data can always be entered reliably, making it an easy-to-use tablet input with a wide range of uses. Its purpose is to provide equipment.

[Means for solving problems]

The present invention includes a tablet equipped with a group of X and Y electrodes, an X and Y electrode drive circuit that sequentially applies scanning pulses to the group of X and Y electrodes, and a drive control of the X and Y electrode drive circuit at a predetermined timing. an input pen that inputs coordinate information by contacting the tablet; a comparator that passes output of the input pen that is above a predetermined threshold value as a detection signal; and a control circuit that inputs coordinate information based on the output of this comparator. and a coordinate information generation circuit that generates information. In addition, it is equipped with a counting circuit that counts the number of output pulses of the comparator for each scan for each of the X and Y electrode groups, and when this counting circuit outputs two or more detection pulses, a detection incomplete signal is sent. Further, when this counting circuit outputs detection pulse 1, a signal extraction circuit that outputs a detection end signal is equipped at the output stage of the counting circuit,
The X and Y electrode drive circuits are also provided with a drive level switching circuit that sets the overall level of the scanning pulse to be raised or lowered stepwise as required. Furthermore, the control circuit has a scan pulse level switching control function that performs variable control by repeating the level setting operation of the drive level switching circuit until the signal extraction circuit outputs a detection end signal, and Even if the scanning pulse level is variably set by energizing the drive level switching circuit that operates based on the signal, if the minimum value of the pulse count value becomes 2 again, it works together with the coordinate information generation circuit to move to the later position. It has a post-pulse identification function that identifies a pulse as a position information pulse. This aims to achieve the above-mentioned purpose.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described based on FIGS. 6 to 8. In the drawings, the same reference numerals are used for the same components as in the prior art.

FIG. 6 is an electrical block diagram illustrating a tablet input device according to the present invention. In the figure, code 1
shows a tablet in which an X electrode group X ₁ -X _o and a Y electrode group Y ₁ -Y _o are arranged. When the input pen 4 comes into contact with this tablet 1, the pen switch 4A closes.
In the same manner as in the conventional example described above, the counter 7 is operated by the function of the control circuit 20, and this counter 7
The counted value of is sent to the X (or Y) electrode drive circuit 2A (or 3A) via the gate 8, and each X _electrode
Scanning of X _o or Y electrodes Y ₁ to _{Y o} is performed.

The X and Y electrode drive circuits 2A and 3A include a gate 3.
A drive level switching circuit 31 is connected through 0. The power supply voltage Vcc is input to the drive level switching circuit 31, and in accordance with the drive level designation signal (digital signal) input from the control circuit 20, it performs, for example, D-A conversion, and converts the corresponding analog voltage. X (or Y) electrode drive circuit 2
It has a function of outputting as a power source for driving the A (or 3 A) output stage.

To explain this in more detail, drive level switching circuit 3
1 is a value obtained by dividing the range from the minimum level Qmin to the maximum level Qmax into n equal parts (in this example, n=3,
Analog voltages set at each drive level (R ₁ =Qmin, R ₂ , R ₃ , R ₄ =Qmax) are switched and generated. In addition, the X, Y electrode drive circuit 2
A and 3A are configured to output scanning pulses whose peak value is the analog voltage input from the drive level switching circuit 31 via the gate 30 to the X and Y electrode groups X ₁ to _{X o} and Y ₁ to _Yo . It's on.

This gate 30 is controlled by an x, y scan switching signal sent from the control circuit 20 in synchronization with the gate 8.
Switching is controlled in units of one scan of one electrode group.

The input pen 4 detects the scanning pulse through capacitive coupling with the tablet 1, and sends its output signal to one input terminal of the comparator 10 via the amplifier 9. The other input terminal of this comparator 10 has a predetermined threshold voltage set by a semi-fixed resistor R.
SO is entered.

The output of this comparator 10 is passed through a shaping circuit 11 to a gate 12 and a counting circuit 2 in an extraction means 25.
Sent to 3. This counting circuit 23 includes an X electrode group
While one electrode group of X ₁ to X _o or Y electrode group Y ₁ to _{Y o} is cycled, the comparator 10 counts detection signals selected as detection signals equal to or higher than a predetermined threshold level. This count value is sent to a signal extraction circuit 24 connected to the output side of the counting circuit 23.

This signal extraction circuit 24 detects when the count value which is the output of the counting circuit 23 is "2" or more (1 and 2 in FIG.
It is configured to send a detection incomplete signal (see 3 and 4 in FIG. 7) to the control circuit 20, and a detection completion signal when it is "1" (see 3 and 4 in FIG. 7). Also, when the drive level is lowered by one step, the count value is "2" →
If it changes to "0" (see Figure 8 1-4),
A drive level return signal is sent to the control circuit 20.

Here, FIGS. 7 1 and 3 show the amplifier 9 when the input pen 4 at drive levels R ₄ and R ₃ is in contact with the current Xi in the enlarged key segment LKS (see P3 in FIG. 3). shows the approximate output waveform of
Figures 2 and 4 are the comparators 10 in Figures 1 and 3, respectively.
shows the output of Further, Figs. 8 1 and 3 show the case where the input pen 4 at the drive levels R ₂ and R ₁ is brought into contact with the center between the electrodes Xi-1 and Xi in the enlarged key segment LKS (see P2 in Fig. 3). Figures 2 and 4 show the outputs of the comparator 10 in the cases of Figures 1 and 3, respectively.

The control circuit 20 has a function of controlling drive level switching based on the output of the extracting means 25 and causing one electrode group to rescan. That is, when the pen switch 4A is closed, the control circuit 20 first specifies the maximum drive level, and
One electrode group of the tablet 1 is scanned, and the drive level is lowered one step at a time until a detection end signal is input from the signal extraction circuit 24, and the electrode group is rescanned. and,
When the detection end signal is input from the signal extraction circuit 24, the drive level is then fixed and the data check operation described above is performed. Separately, when a drive level return signal is input from the signal extraction circuit 24, the control circuit 20 raises the drive level by one step and rescans the electrode group (at this time, the comparator 10 In addition to performing coordinate detection (outputting two detection signals), the data check operation described above is then performed.

On the other hand, the gate 12 is switched and connected to the latch circuit 13 by the control circuit 20 until the data check operation is started. Therefore, this latch circuit 13 latches the count value of the counter 7 every time a detection signal is inputted through the gate 12, but ultimately outputs the last latched data.

To explain this more specifically, when the signal extraction circuit 24 outputs a detection end signal to the control circuit 20, the latch data is stored at the electrode (the electrode closest to the contact area of the input pen 4) related to the maximum level detection signal. ) is the coordinate data of the position, which is input pen 4
This is the data of the key segment KS or LKS specified by .

Further, when the signal extraction circuit 24 outputs a drive level return signal, certain drive levels R(l) and R(l
-1), there are two maximum level detection signals detected by the comparator 10, but in this case, the latch data is the detection signal detected later (see ai in Figure 8). This is the coordinate data of the electrode position. For example, when the input pen 4 is brought into contact with the center between the electrodes in the aforementioned enlarged key segment LKS (see P2 in Figure 3), no matter which of the electrodes the scanning pulse applied to the enlarged key segment LKS is detected, the enlarged key This becomes segment LKS data.

When the coordinate data has been latched as described above, the control circuit 20 then switches and connects the gate 12 to the comparator 14 side to perform a data check operation. When the signal extraction circuit 24 outputs a detection end signal, the detection signal input to the comparator 14 as a comparison timing signal is the maximum level detection signal related to the same electrode as the detection signal that performed the data latch, and therefore , since the counted value of the counter 7 and the latch data of the latch circuit 13 at the comparison timing match, the comparator 14
outputs a match signal.

On the other hand, when the signal extraction circuit 24 outputs the drive level return signal, the comparator 14 has a
Two maximum level detection signals are input. At this time, when the previous detection signal is input, the count value of the counter 7 and the latch data of the latch circuit 13 at that timing do not match, and no match signal is output. However, when a later detection signal is input, the count value of the counter 7 at that timing and the latch data of the latch circuit 13 match, so the comparator 14 outputs a match signal. Therefore, the output data of the latch circuit 13 at the timing when the comparator 14 sends out the coincidence signal is sent out as correct coordinate data.

In this way, when the output of one of the x and y coordinate data is completed, the control circuit 20 switches the gates 8 and 30, and detects the other coordinate data in exactly the same manner as described above.

Note that the interval between the drive levels of the drive level switching circuit 31 is sufficiently narrow, and the maximum level that can be distinguished between a certain drive level R(l) and R(l-1) depending on the contact position of the input pen. The detection signal is set to be one in the normal key segment KS (see FIG. 3) and two or less in the expanded key segment LKS.

Furthermore, since the electrodes are scanned at a very high speed compared to the operating speed of the operator, even if the same electrode group is repeatedly scanned, this does not interfere with the operator's input operations.

According to this embodiment, it is possible to always input coordinates reliably regardless of the contact position of the input pen within the enlarged key segment, thereby improving operability and at the same time making it possible to change the tablet. Since it is possible to freely lay out the character sheet without any trouble, it is possible to create a device that meets the operator's needs and conditions of use.

Furthermore, when inputting information using a page-type information sheet, there is no need to adjust individual threshold values, which simplifies the configuration and maintenance, and allows the device to be used for multiple purposes. Can be done.

In the above embodiment, the electrode drive level was configured to be lowered in stages, but the present invention is not limited to this in any way, and may be increased in stages. It is also possible to asymptotically converge using the two-division method (see patent application No. 56-135838).

In addition, the conventional character sheet 1 shown in Figures 3 and 4
5, the key segment KS shown in FIG.
The step between them is eliminated and a flat one is used, and furthermore, even when two detection signals of the maximum level are obtained by touching a pen between key segments KS, coordinate information is generated based on one of the detection signals. It's okay.

〔Effect of the invention〕

As described above, according to the present invention, since the pulse height of the scanning pulse is raised or lowered stepwise as necessary, the maximum level signal detected by the input pen can be detected more reliably. This makes it possible to easily detect the required signal even from low-sensitivity areas called non-detection areas near the boundaries of key segments, resulting in non-detection. In addition, when an expanded key segment is provided and two signals of the same level are detected within the segment, the coordinate information generation circuit and control circuit work together to Since the located signal is specified as coordinate data, signal processing can be performed stably and with high precision.This eliminates undetected areas within the enlarged key segment and allows the character sheet to be laid out freely. It is possible to provide a tablet input device with excellent operability and a wide range of uses that allows data input to be performed reliably at all times.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a conventional tablet input device, Fig. 2 is an explanatory diagram of the operation of an electrode drive circuit, which is a part of Fig. 1, and Fig. 3 is a partial plan view showing the tablet portion of Fig. 1; 4 is a vertical sectional view taken along the line - in FIG. 3, FIG. 5 is an explanatory diagram of the operation of the first comparator, FIG. 6 is a block diagram showing the tablet input device according to the present invention, and FIGS. Figure 8 is the 6th
FIG. 3 is an explanatory diagram showing the output states of the amplifier and comparator in the figure. X ₁ ~X _o ...X electrode, Y ₁ ~ _{Y o} ...Y electrode, 1...
...tablet, 2,2A...X electrode drive circuit,
3,3A...Y electrode drive circuit, 4...Input pen,
10... Comparator, 13... Latch circuit as the main part of the coordinate information generating section, 20... Control circuit, 25
. . . Discrimination means, 31 . . . Drive level switching circuit.

Claims (1)

[Claims] 1. A tablet equipped with a group of X and Y electrodes, and an X and Y device that sequentially applies scanning pulses to the group of X and Y electrodes.
an electrode drive circuit; a control circuit that drives and controls the X and Y electrode drive circuits at predetermined timing; an input pen that inputs coordinate information by contacting the tablet; In a tablet input device equipped with a comparator that passes an output as a detection signal, and a coordinate information generation circuit that generates coordinate information based on the output of the comparator, the number of output pulses of the comparator is set to each of the X and Y electrodes. It is equipped with a counting circuit that counts every scan for the group, and when this counting circuit outputs 2 or more detection pulses, it outputs a detection incomplete signal, and when this counting circuit outputs 1 detection pulse, it outputs a detection incomplete signal. A signal extraction circuit that outputs a detection end signal is equipped at the output stage of the counting circuit, and the X and Y electrode drive circuits are set to raise or lower the overall level of the scanning pulse in stages as necessary. scanning pulse level switching control, further comprising a drive level switching circuit for setting, wherein the control circuit performs variable control by repeating the level setting operation of the drive level switching circuit until the signal extraction circuit outputs a detection end signal; If the minimum value of the pulse count value becomes 2 again even if the scan pulse level is variably set by energizing the drive level switching circuit and operating based on the detection incomplete signal from the signal extraction circuit. A tablet input device characterized in that it has a subsequent pulse specifying function that cooperates with the coordinate information generating circuit to specify a subsequent pulse as a position information pulse.