JPH0123804B2 - - Google Patents

Description

DETAILED DESCRIPTION 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.

Tablet input devices are easy to operate and are inexpensive, allowing them to be used for inputting character and graphic data and item data.
In recent years, it has become most 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)
sequentially applying a scanning pulse to an X electrode group and a Y electrode group arranged in two orthogonal directions, and detecting the scanning pulse with an input pen in contact with the tablet;
From this timing, coordinate information regarding the contact area of the input pen is input.

Specifically, as shown in FIG. 1, n electrodes X ₁ to X _o and Y ₁ to _{Y o} are arranged in the x-axis direction and the y-axis direction of the tablet 1 on which character information etc. are displayed. Electrode drive circuits 2 and 3 sequentially apply scanning pulses to one end of these X electrode group and Y electrode group.
is connected.

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.
The counting operation of the counter 7 connected to the oscillator 6 is started. The counted value of this counter 7 is sent to the electrode drive circuit 2 or 3 every cycle via a gate 8 controlled by a control circuit 5. Then, this 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 as described above (see FIG. 3). When a scanning pulse is applied to the electrode (for example, X _i ) related to the key segment KS (see FIG. 2) that the input pen 4 is in contact with, scanning is performed due to capacitive coupling between the input pen 4 and the tablet 1. Pulse detection is performed. After this detection signal is amplified by an amplifier 9, 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 has a function of passing only a detection signal equal to or higher than a predetermined threshold level set by a semi-fixed resistor R,
This is to prevent scanning pulses of electrodes applied to adjacent key segments from being detected.

When the input pen 4 is brought into contact with the tablet 1 and the pen switch 4A is closed, the control circuit 5 closes the gate 1.
2 is the latch circuit 1 which 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, during one cycle of scanning of one electrode group, a detection signal exceeding the threshold is inputted to the latch circuit 13 as a latch STB signal. This latch circuit 13 is
When the latch 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. When one cycle of scanning of the one electrode group is completed, a data check operation is then started. That is, by the action of the control circuit 5, the scanning pulse is once again applied to the 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. Thereby, the output data of the latch circuit 13 when a coincidence 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 the way, conventionally, when setting the threshold value of the comparator 10, when the input pen 4 comes into contact with the center of the boundary of the key segment KS (as shown in FIG.
(see P ² ), if the amplified detection signal levels a _i , a _i+1 (a _i = a _i+ 1 ) induced from the electrodes X _i , X _i+1 on both sides are used as a reference (see Fig. 4 (see SO in Figure 5), when the boundary is shifted toward either key segment from the center, the detection signal level a _i , a _i+1 is a _i > SO > a _i+1 (see Figure 5, 1).
Or a _i <SO < a _i+1 (see Figure 5, 2), so
A detection signal equal to or higher than the threshold value SO can be 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.

However, setting the ideal threshold value using the semi-fixed resistor R described above is extremely difficult due to variations in products and changes in environmental conditions, and requires time for adjustment. If the threshold value fluctuates from SO and shifts up or down,
This method has the disadvantage that coordinate detection becomes impossible near the boundaries of key segments. Specifically, when the threshold value increases, as shown in SU in Figure 4, no detection signal can be obtained, while when the threshold value decreases, as shown in SD in the same figure, two detection signals are obtained in one scanning cycle. Since the above detection signal is obtained, the comparator 1
4, the coordinates cannot be detected because there is no match. In addition, when using page-type information sheets, etc., the detection level decreases overall as the number of sheets increases, so individual signal level compensation is required, but accurate compensation is difficult, so Similarly, there was the problem that there were areas where the coordinates could not be detected.

The present invention has been made in view of the shortcomings of the prior art, and it is possible to compare detection signals step by step using a plurality of threshold values and select the detection signal with the maximum level, thereby detecting a key segment. It is an object of the present invention to provide a tablet input device with excellent operability that eliminates non-detection areas near the boundaries of the tablet and allows reliable data input at all times.

The present invention includes a counter that counts input pen detection signals that exceed a predetermined threshold value within one scan of one electrode group, and a counter that switches between a plurality of threshold values set at predetermined intervals. comprising a threshold value switching circuit and a control circuit that performs threshold switching control according to the count value of the counter and causes the electrode group to rescan, and when the count value within one scan is 1, The above object is achieved by configuring the system to generate coordinate information based on this detection signal.

Hereinafter, one embodiment of the present invention will be described based on FIGS. 6 to 9. 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 diagram, 1 is X
This is a tablet on which electrode groups X ₁ -X _o and Y electrode groups Y ₁ -Y _o are arranged. When the input pliers are brought into contact with this tablet 1, the pen switch 4A is closed, and the counter 7 is operated by the function of the control circuit 20 in the same way as in the conventional example, and the count value of this counter 7 is transmitted through the gate 8. The signals are sent to the electrode drive circuit 2 or 3, and each of the X electrodes X ₁ to X _o or the Y electrodes Y ₁ to _Yo is scanned. The input pen 4 is
The scanning pulse is detected by capacitive coupling with the tablet 1, and its output signal is sent to one input terminal of the comparator 21 via the amplifier 9. The other input terminal of the comparator 21 is connected to a DA converter 22 as a threshold switching circuit. The D-A converter 22 generates an analog signal corresponding to the digital signal based on a threshold designation signal (digital signal) sent from the control circuit 20, and applies a predetermined threshold voltage to the comparator 21. It has a function to output. To explain this in more detail, the D-A converter 22 converts the amplifier 9 between the minimum output level Qmin and the maximum output level Qmax by 2·K (K= 1,
2, . . .) Threshold voltages set to equally divided values are generated by switching.

The output of the comparator 21 is sent to the gate 12 and the counter 23 via the shaping circuit 11.
This counter 23 operates while one electrode group of the X electrode group X ₁ to X _o or the Y electrode group Y ₁ to _{Y o} is scanned once.
It has a function of counting detection signals selected by the comparator 21 as detection signals equal to or higher than a threshold level, and this count value is calculated by the control circuit 2.
It is set to be sent to 0. Then, when the count value of the counter 23 is other than "1", the control circuit 20 sends a threshold designation signal different from the previous one to the D-A converter 22 according to the count value, and outputs a threshold value to the D-A converter 22. In addition to raising or lowering the threshold level, the same electrode group as the previous scan is re-scanned. By scanning this operation in one cycle of the same electrode group, one detection signal is output from the comparator 21 (the count value of the counter 23 is "1").
By repeating this until the maximum level of the detection signal is reached, the maximum level of the detection signal can be obtained. This maximum level detection signal is due to the scanning pulse of the electrode closest to the contact area of the input pen 4 (the key segment designated by the input pen 4). Note that details of the operation of varying the threshold level will be explained later.

The gate 12 is switched and connected to the latch circuit 13 by the control circuit 20 until the above-mentioned operation of selecting the maximum level detection signal is completed. Therefore, this latch circuit 13 latches the count value of the counter 7 every time a detection signal is input through the gate 12, but ultimately,
The count value of the counter 7 at the timing when the maximum level detection signal is input is latched. The data latched by the latch circuit 13 is position data relating to the contact portion of the input pen 4, as described above. When the above-described operation of selecting the maximum level detection signal is completed, the control circuit 20 leaves the threshold level unchanged and switches the gate 12 to the comparator 14 side, and rescans the contact electrode group. do. As a result, the detection signal is inputted to the comparator 14 as a comparison timing signal via the gate 12,
The comparator 14 compares the count value of the counter 7 at the timing when the detection signal is inputted with the output data of the latch circuit 13, and outputs a match signal when they match. Therefore,
The output data of the latch circuit 13 when the comparator 14 outputs a coincidence signal will be output as correct coordinate data.

The operation of varying the threshold level of the comparator 21 described above is performed as follows. Here, the threshold value is the output level width of the amplifier 9, a level S ¹ that equally divides the range between Qmax and Qmim into 8
^.about.S8 (see FIG. 7), and a case will be taken as an example in which X coordinate data related to the contact area of the input pen 4 is detected.

First, the control circuit 20 specifies a threshold level of S ⁵ =(Qmax-Qmim)·1/2 before applying a scanning pulse. Then, the gate 8 is connected to the electrode drive circuit 2 side, the counting operation of the counter 7 is started, and a scanning pulse is sequentially applied to each of the X electrodes X ₁ to _{X o} . At this time, when the signal detected by the input pen 4 becomes as shown in 1 in FIG. 7 to 1 in FIG. 9 depending on the contact position or state of the input pen 4, the counter 23 respectively The value counted is "1",
They become "2" and "0". 1 in Figure 7 is the input pen 4
shows the output of the amplifier 9 when the key segment KS (x=i) is brought into contact with the approximate center (see P ¹ in Fig. 2), and there is only one detection signal that exceeds the threshold value S ⁵ ( (See 2 in Figure 7). This detection signal ai is due to a scanning pulse applied to the electrode X _i of the contact portion of the input pen 4. At this time, "1" is input from the counter 23 to the control circuit 20, indicating that the selection of the detection signal of the maximum level has been completed, and the data check operation then begins.

Next, 1 in Fig. 8 is a case where the input pen 4 is brought into contact near the boundary of the key segment KS (Fig. 2).
(see P ³ ), and the signal exceeding the threshold S ⁵ is 2
There is one (see Figure 8 2). At this time, the count value is “2”
is sent to the control circuit 20, so the control circuit 2
0 increases the threshold and S ⁷ = (Qmax−Qmim)・3/
Specify a threshold level of 4 and apply a scanning pulse to the X electrode group again. This time, there is only one detection signal that exceeds the threshold value ^S7 (see FIG. 8, 3), so the count value becomes "1", and the selection of the detection signal of the maximum level is completed in the same manner as described above. This detection signal is due to the scanning pulse applied to the electrode X _i (key segment KS (x=i) designated by the input pen 4) closer to the input pen 4.

1 in FIG. 9 is a case where the overall detection level has decreased for some reason, and the detection signal exceeding the threshold value ^S5 is 0 (see FIG. 9, 2). At this time, the count value "0" is input to the control circuit 20, so the control circuit 20 lowers the threshold value and satisfies ^S3 =(Qmax-
Specify Qmim)・1/4 and apply the scanning pulse to the X electrode group again. Then, there is one detection signal that exceeds the threshold value S ³ (see FIG. 9, 3), so the count value becomes "1", and the key segment KS (x The scanning pulse applied to the electrode Xi according to =i) is detected.

In this way, for a certain threshold value, the counter 23
When the count value is "2" or more, the threshold value is raised, and when it is "0", the threshold value is lowered, and the threshold value is changed asymptotically to detect the maximum level detection signal. In particular, according to the above-mentioned two-division method, it is possible to change the threshold level divided into 2 ^R by performing R operations.For example, it is possible to change the threshold level by 256 times by performing 8 operations. Here, the scanning of the electrode is done at a very high speed compared to the operating speed of the operator.
Even if the scanning is repeated for 8 cycles, it will not interfere with the operator's input operations.

As described above, when the X coordinate data is input, the next control circuit 20 connects the gate 8 to the electrode drive circuit 3 side, scans the Y electrode group, and converts the data to the Y coordinate in the same manner as described above. The detection signal having the maximum level is selected, and the Y coordinate data regarding the contact portion of the input pen 4 is input.

According to this embodiment, since the electrode closer to the input pen (the scanning pulse applied to the key segment specified by the input pen can always be reliably detected), the apparent non-detection area on the tablet can be eliminated. Operability can be improved,
It is possible to improve work efficiency when inputting a large amount of characters, such as when editing a newspaper. Further, since adjustment and maintenance for setting the threshold value, which is required in the conventional method, is not necessary, manufacturing of the device becomes easier.

Furthermore, even when information is input using a page-type information sheet, there is no need to adjust individual threshold values, and the device can be used for multiple purposes.
Furthermore, even when an expanded key segment consisting of multiple coordinate areas is configured by changing the character sheet, etc., no undetected areas occur within the expanded key segment, and therefore a free layout can be performed without replacing the tablet itself. becomes possible.

As described above, according to the present invention, it is possible to eliminate undetected areas near the boundaries of key segments, and to provide a tablet input device with excellent operability 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 a partial plan view of the tablet which is a part of Fig. 1, Fig. 3 is an explanatory diagram of the operation of Fig. 2, and Fig. 4 is a 1 and 2 in FIG. 5 are explanatory diagrams showing the operation of the comparator in FIG. 1, and FIG. 6 is a block diagram showing the tablet input device according to the present invention. Figure 7 1
6 is an explanatory diagram of the operation of the D-A converter and a schematic explanatory diagram of the detection signal, 2 in FIG. 7 is an operational diagram of the comparator, and 1 in FIG. 8 is a schematic explanatory diagram of the detection signal. 2 and 3 are operation diagrams of the comparator, 1 in FIG. 9 is a schematic explanatory diagram of the detection signal, 2 and 3 in FIG.
3 is an operational diagram of the comparator. X ₁ ~X _o ...X electrode, Y ₁ ~ _{Y o} ...Y electrode, 1...
...Tablet, 4...Input pen, 10, 21...
Comparator, 13... Latch circuit as the main part of the coordinate information generating section, 20... Control circuit, 22...
...D-A converter as a threshold switching circuit,
23...Counter.

Claims (1)

[Claims] 1. A tablet having an X electrode group and a Y electrode group, to which scanning pulses are sequentially applied, an input pen that inputs coordinate information by contacting the tablet, and a predetermined output signal from among the output signals of this input pen. a comparator that passes only signals above a threshold of
In the tablet input device, the tablet input device includes a coordinate information generating section that outputs position data of the scanning pulse as coordinate information based on a detection signal that is an output of the comparator, and a predetermined threshold value is set within one scan of the one electrode group. a counter that counts the detection signal of the input pen that exceeds the input pen; a threshold switching circuit that switches between a plurality of thresholds set at predetermined intervals; and a control circuit that performs switching control and rescans the electrode group, and is configured to generate coordinate information based on this detection signal when the count value within one scan is 1. tablet input device.