JPH0219490B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tablet input device, and particularly to a tablet input device that extracts a predetermined number of detection signals by changing the threshold value or the level of a scanning signal with respect to the output signal of an input pen, and extracts a predetermined number of detection signals based on the detection signals. The present invention relates to a tablet input device that generates coordinate information.

Tablet input devices are easy to operate and are inexpensive, allowing them to be used for inputting character/graphic data and item data.
It has been widely used in recent years for magazine editing, inventory management, etc. To explain the operation of this tablet input device using a capacitive coupling type as an example, as shown in FIG.
X ₁ to Xn, Y ₁ to Ym are arranged, and on the character sheet 50 placed on this tablet 1, key segments KS divided for each character corresponding to each intersection part of the electrode group are arranged. Alternatively, an expanded key segment LKS extending over a plurality of intersection parts is formed.
Scanning pulses are sequentially applied to the X and Y electrode groups X ₁ to Xn and Y ₁ to Ym from the X and Y electrode drive circuits (see FIG. 7), so that the operator can scan the character sheet 50. desired key segment KS,
When you touch the input pen (see Figure 7) to LKS,
The input pen is capacitively coupled to the electrodes of the tablet 1 to detect the scanning pulse, and from the detection timing, coordinate information of the key segments KS and LKS that are in contact with the input pen can be obtained.

By the way, when the input pen is capacitively coupled to the electrodes of the tablet 1, the input pen detects not only the electrodes of the key segments KS and LKS that are in contact with it, but also the scanning pulses applied to the adjacent electrodes. For this reason, conventionally, among the output signals of the input pen, only signals exceeding a predetermined threshold value SO are treated as detection signals. Specifically, the threshold value
Let SO be the same as the detection signal levels aj, aj+1 (aj=aj+1, see Figure 4) induced from the electrodes Xj, X _j+1 on both sides when the input pen is brought into contact with the boundary of the key segment KS. If the pen touch is biased toward either key segment KS, aj > SO > aj + 1 or aj < SO < aj + 1. Using this fact, input a detection signal that is above this threshold value SO. This was taken as the maximum level detection signal associated with the scanning pulse applied to the electrode closest to the pen. However, setting the threshold value to the above ideal value using a semi-fixed resistor is extremely difficult due to variations in products and changes in environmental conditions, and requires time to adjust. If the threshold value fluctuates above and below the SO, coordinate detection becomes impossible near the boundaries of key segments.

Therefore, in order to solve this drawback, the applicant of the present application first made the threshold variable, and changed the threshold in stages to select the output signal of the input pen, so that the detection signal with the maximum level was selected. An application was filed for an invention that enabled extraction (Patent Application No. 135837/1983)
(Special Application No. 135838/1983). In this invention, for example, when a pen is touched on P1, P2, and P3 in FIG. 1, the output signals after amplification of the input pen in x-direction scanning become as shown in FIGS. 2 to 4, respectively, and the signal selection is When gradually lowering the threshold for
If one or two detection signals at the maximum level can be obtained with the thresholds S4, S3, and S2, and there is one detection signal at the maximum level, two detection signals are obtained based on that signal.
In the case of two signals, the X coordinate is specified based on one of the signals.

However, in the above invention, the key segment at the outermost periphery of the tablet, that is, for example, the X coordinate=1
Regarding KS, when the pen is touched to the limit point P4 of the input area, the input pen output becomes as shown in Fig. 5, one detection signal of the maximum level is obtained at the threshold value S2, and based on this, the X coordinate ( = 1) is specified, even if the point P5 outside the input area is touched, the threshold value is automatically lowered to the level S1 at which there is only one detection signal, and the X coordinate (= 1) is also specified. is output (see Figure 6). Therefore, if the tip of the input pen touches the outer periphery of the tablet when the operator places his or her hand holding the input pen on the periphery of the tablet to read a document, turn a page, or take a pause, it is the same as touching the outermost key segment with the pen. Also, when inputting figures, even if the trajectory of the input pen leaves the outermost key segment and draws an arc outward, it may not be possible to input it to the outermost key segment, that is, draw a straight line. There was a risk that the coordinates would be input as if they had been entered.

The present invention has been made in view of the above drawbacks, and includes a tablet input device that extracts a detection signal of the maximum level by increasing or decreasing the scanning pulse level or threshold level. By providing an electrode and making coordinate data related to this dummy electrode invalid data when it is generated, it is possible to eliminate undetected areas of the key segment and ensure data input, and at the same time, it is possible to input coordinate data on the outer periphery of the tablet. The object of the present invention is to provide a tablet input device that eliminates input errors and improves reliability and operability.

The present invention provides a tablet having a group of X and Y electrodes and a dummy electrode provided outside the group of X and Y electrodes, an input pen that inputs coordinates by contacting the tablet, and a pen that inputs a scanning signal to each electrode of the tablet. extracting a predetermined number of detection signals from the output signals of the input pen by changing the threshold value for the output signal of the input pen or the level of the scanning signal; The above-mentioned object is achieved by providing means for generating coordinate information on which the dummy electrode is brought into contact, and means for invalidating the coordinate information when the coordinate information relates to the dummy electrode. Hereinafter, one embodiment of the present invention will be described based on FIGS. 7 to 16.

FIG. 7 is a block diagram showing the overall configuration of a tablet input device according to the present invention. In the figure,
An insulating substrate 100A (see FIGS. 9 and 10) is sandwiched between the tablet 100 on which the character sheet 50 (see FIG. 9) is placed in the x-axis direction and the Y-axis direction, respectively.
m X, Y electrode groups X ₁ to Xn, Y ₁ to Ym are arranged. Outside these X and Y electrodes, there are further X dummy electrodes X ₀ , Xn+1, and Y dummy electrodes.
Y ₀ and Ym+1 are provided, and electrode drive circuits 2 and 3 that sequentially apply scanning pulses are connected to one end of the X and Y electrode group constituted by each of these electrodes. In order to specify characters, the input pen 4 operated by the operator has a built-in pen switch 4A that operates when it touches the tablet 1.
When the pen switch 4A is closed, the control circuit 5 is activated and the ring counter 7 connected to the oscillator 6 starts counting. The count value of the ring counter 7 is sent to the electrode drive circuit 2 or 3 in units of one period via a gate 8 which is controlled to be switched to the X or Y side by the control circuit 5. Then, this electrode drive circuit 2 or 3 converts the sign of the count value sent from the ring counter 7,
X, Y electrode group X ₀ to Xn in the tablet 100
+1, Y ₀ to Ym+1 (see FIG. 8).

Key segments KS and LKS (see FIG. 9) partitioned for each character are provided on the character sheet 50 at the intersections of the X electrodes X ₁ to Xn and the Y electrodes Y ₁ to Ym, and the input pen 4 abutted key segment of
When a scanning pulse is applied to the electrode related to KS, the scanning pulse is detected by capacitive coupling between the input pen 4 and the electrode of the tablet 100. This signal is amplified by an amplifier 9 connected to the output side of the input pen 4 and then sent to one input terminal of a comparator 10. The other input terminal of this comparator 10 is connected to a DA converter 11 as a threshold switching circuit. The D-A converter 11 generates an analog signal corresponding to the digital signal based on a threshold designation signal (digital signal) sent from the control circuit 5, and applies a predetermined threshold voltage to the comparator 10. It has a function to output. To explain this in more detail, the D-A converter 11 operates at a plurality of threshold voltages S1 to S4 whose level increases step by step, as shown in FIG. It has become possible to generate

The output of the comparator 10 is sent via a shaping circuit 12 to a gate 13 and a counting circuit 15 in the discriminating means 14. This counting circuit 15 receives a detection signal that is equal to or higher than a predetermined threshold level by the comparator 10 while one electrode group of the X electrode group X ₀ to Xn+1 or the Y electrode group Y ₀ to Ym+1 is scanned once. It has a function of counting the selected detection signals, and this count value is sent to a discrimination circuit 16 connected to the output side of the counting circuit 15. This discrimination circuit 16 detects the counting circuit 15 at the point when one cycle of scanning of one electrode group is completed.
When the count value which is the output is "2" or more (for example, when the threshold value is S2 in FIG. 11), the detection incomplete signal is "1" (also when the threshold value is S3)
It is configured to send a detection end signal to the control circuit 5. In addition, if the count value changes from "2" to "0" when the threshold value is increased by one step (for example, in FIG. 12, the threshold value is
2 to S3), a threshold return signal is sent to the control circuit 5.

The control circuit 5 has a function of controlling switching of the threshold value based on the output of the discriminating means 14 and causing one electrode group to rescan.
That is, the control circuit 5 controls the pen switch 4A.
When closed, first, the minimum level threshold value S1 is specified and one electrode group of the tablet 100 is scanned, and the threshold value is increased one step at a time until the detection end signal from the discrimination circuit 16 is input. As the electrode group is raised, the electrode group is rescanned. When a detection end signal is input from the discrimination circuit 16, the threshold value is then fixed and a data check operation, which will be described later, is performed. Separately, when a threshold return signal is input from the discrimination circuit 16, the control circuit 5 lowers the threshold by one level and rescans the electrode group (at this time, the comparator 10 outputs two detection signals)
In addition to performing coordinate detection, a data check operation, which will be described later, is also performed.

On the other hand, the gate 13 is switched and connected to the latch circuit 17 by the control circuit 5 until a data check operation is started. Therefore, this latch circuit 17 controls the ring counter 7 every time a detection signal is inputted through the gate 13.
The count value of is latched, but in the end, the last latched data is output. Specifically, when the discrimination circuit 16 outputs a detection end signal to the control circuit 5, the latch data indicates the position of the electrode (the electrode closest to the contact area of the input pen 4) associated with the detection signal of the maximum level. This is the data of the key segment KS specified by the input pen 4. Furthermore, when the discrimination circuit 16 outputs the threshold value return signal, it is the case that there are two detection signals of the maximum level between a certain threshold value S(l) and S(l+1). At this time, the latch data becomes the coordinate data of the electrode position related to the detection signal detected later (see a4 in FIG. 4).
For example, when the input pen 4 is brought into contact with the center position between the electrodes in the enlarged key segment LKS that displays one item across multiple input areas (see P3 in Figure 1 and P10 in Figure 9), both of the corresponding Whichever scanning pulse is applied to the electrode is detected as data for the expanded key segment LKS.

When the coordinate data has been latched as described above, the control circuit 5 then switches the gate 13 to the comparator 18 and performs a data check operation. 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 output to the gate 13 in the same manner as described above.
The data is sent to the data comparator 18 via the data comparator 18. When a detection signal is input, this data comparator 18 detects the ring counter 7 at that timing.
The count value is compared with the latch data of the latch circuit 17, and when they match, a match signal is output. A data check is performed when the discrimination circuit 16 outputs a detection end signal or a threshold return signal.
outputs a detection end signal, only one maximum level detection signal related to the same electrode as the detection signal that performed the data latch is inputted to the data comparator 18 as a comparison timing signal. ring counter 7 in
The counted value and the latch data of the latch circuit 17 match, and the data comparator 18 outputs a match signal.

On the other hand, when the discrimination circuit 16 outputs the threshold return signal, the data comparator 18 detects two maximum levels of approximately the same level existing between the thresholds S(l) and S(l+1). A signal is 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 17 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 17 match, so the data comparator 18 outputs a match signal. The coincidence signal that is the output of the comparator 18 is sent as a signal to an external CPU via a gate 19.
etc. are now being sent. and the concerned
On the CPU side, the latch data output of the latch circuit 17 at the timing of receiving the signal is performed.
Import DATA as correct coordinate data that is not affected by noise.

A gate 1 is connected to the output side of the comparator 18.
9 is connected. This gate 19 is controlled by an address verification means 20 for blocking the output of a coincidence signal from the comparator 18 and invalidating the coordinate information output when the data latched in the latch circuit 17 relates to the X or Y dummy electrode. . This address verification means 20 includes a coincidence detection circuit 2 which inputs the counted value of the counter 7 through a gate 21.
2, 23, and an X, Y dummy address memory 2 connected to each of these coincidence detection circuits 22, 23.
It consists of 4.25. The gate 21 is configured to be switched to the X or Y side in synchronization with the control circuit 8. Also, X dummy address memory 2
4 stores an X dummy address of X=0 and n+1, and outputs the address to the coincidence detection circuit 22. On the other hand, Y dummy address memory 25
stores the address of Y=0, m+1 and outputs the address to the coincidence detection circuit 23. The function of the address collation means 20 configured in this way will be explained with respect to the X electrode group, for example. At this time, the gate 21 is connected to the coincidence detection circuit 22 side, and the count value of the ring counter 7 is connected to the X dummy address memory 24.
A gate close signal is sent as a control signal to the gate 19 via the OR circuit 26 only when the data matches the data related to the X dummy electrode _X0 or Xn+1 stored in the data. The gate 19 is closed by this control signal and does not output a signal even if a coincidence signal is input from the comparator 18. Therefore, for example, when the input pen 4 touches each point P6 to P9 in FIG. 9 on the outermost key segment KS of the tablet 100,
The amplified output of the input pen 4 is as shown in FIGS. 11 to 14. As a result, the key segment KS (X=
1, Y=i) is output, but
When the pen is touched outward, the input pen ₄ related to the scanning pulse applied to the X dummy electrode
The output signal after amplification is extracted as the maximum level detection signal, and the count value (0) is input to the latch circuit
Even if the data is latched and a signal is output from the data comparator 18 due to the data check operation, this signal is blocked by the gate 19, so the latched data of the latch circuit 17 becomes invalid and is not incorporated into the CPU or the like. ing.
The same holds true for the Y coordinate. Note that this data invalidation processing may be performed on the CPU side.

30 is an error detection circuit for warning the operator that the pen touch is outside the input range of the outermost key segment KS of the tablet 100. As shown in FIG. 15, this error detection circuit 30 includes a monostable multivibrator 27 which inverts and inputs the signal which is the output of the pen switch 4A, and an S terminal of which the output of the monostable multivibrator 27 is connected to the gate 19. of
A set-reset flip-flop (hereinafter referred to as "R-
It is abbreviated as "SF/F". )28 and this R-SF/F2
8's Q terminal output and the pen switch 4A's
It consists of a NAND circuit 29 that inputs the PSW output. As shown in FIG. 16, the pen switch 4A outputs a low signal while the input pen 4 is in contact with the tablet, and the monostable multivibrator is activated by the touch operation of the input pen 4. 27 outputs a single pulse to set R-SF/F 28, which is previously in a reset state. When the input pen 4 is correctly brought into contact within the input range of the character sheet, a signal is output from the gate 19 after a certain time delay from the pen down. This signal is configured to be output as a low signal, and is connected to the R-
Reset SF/F28. After that, when the input pen 4 is turned up, the signal becomes high.
During this time, the signal output from the NAND circuit 29 remains high. Apart from this, if there is no signal output after the pen-touch, the R-SF/F28 that was set at the time of the pen-touch will not be reset, so the NAND circuit 2
Both inputs of 9 are high and therefore the corresponding
The signal of the NAND circuit 29 becomes low.
Based on this low level signal, a warning is issued using a lamp, screen display, buzzer, etc.

As described above, when the output of one of the x and y coordinate data is completed, the control circuit 5
The gates 8 and 21 are switched to the opposite side from the previous time, and the other coordinate data is sent out in exactly the same manner as described above.

Note that 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, it will not interfere with the operator's input operation.

According to this embodiment, since the outermost key segment of the tablet has a clear boundary with the non-input area, there is no possibility of erroneous input and a highly reliable input device can be obtained. In addition, there are no undetected areas in the key segment or enlarged key segment, and coordinate input can always be performed reliably regardless of the contact position of the input pen, improving operability. Since the character sheet can be freely laid out without changing the tablet, it is possible to create a device that meets the operator's needs and conditions of use. Also, as in the past,
Since adjustment and maintenance for setting the threshold value are not necessary, manufacturing of the device becomes easier. Furthermore, when inputting information using a page-based information sheet, there is no need to adjust individual threshold values, which simplifies configuration and maintenance, and allows the device to be used on multiple days. can do.

In addition, in the above embodiment, the threshold value of the comparator is configured to be raised in stages, but the present invention is not limited to this in any way, and it may be lowered in stages. , it is also possible to asymptotically converge using the two-division method (see patent application No. 56-135838). In addition, the threshold value of the comparator is fixed, an analog voltage that changes step by step is generated by a D-A converter, etc., and this analog voltage is used as the operating power source of the output stage of the electrode drive circuit to apply scanning to each electrode. The maximum level detection signal may be extracted by changing the pulse height value. Furthermore, the dummy electrodes may also be provided only at necessary locations.

Also, for character sheets, key segments
A stepped portion may be provided between the KSs.

As described above, according to the present invention, although the non-detection area within the key segment is eliminated, it is possible to have a clear boundary between the key segment at the outermost periphery of the tablet and the non-input area. It is possible to improve performance and operability.

[Brief explanation of drawings]

Figure 1 is a plan view showing a conventional tablet;
Figures 7 to 6 are explanatory diagrams showing the input pen output waveform after amplification and the threshold value for selecting the detection signal, respectively.
8 is an explanatory diagram showing a scanning pulse, FIG. 9 is a partial plan view showing the tablet of FIG. 7, and FIG. 10 is a partial plan view of the tablet of FIG. 9 is a longitudinal sectional view taken along line X-X in FIG. 9, FIGS. 11 to 14 are line diagrams showing the input pen output after amplification, FIG. 15 is a block diagram showing the configuration of the error detection circuit, and FIG. 16 is a timing chart showing the operation of FIG. 15. X ₁ to Xn...X electrode, X ₀ , Xn+1... X dummy electrode, Y ₁ to Ym... Y electrode, Y ₀ , Ym+1...
Y dummy electrode, 1,100...tablet, 2,
3... Electrode drive circuit, 4... Input pen, 5... Control circuit, 10... Comparator, 11... D-A
Converter, 14...Discrimination means, 17...Latch circuit, 18...Data comparator, 20...Address verification means.

Claims (1)

[Claims] 1. A tablet having a group of X, Y electrodes and dummy electrodes provided outside the group of X, Y electrodes, an input pen that comes into contact with the tablet to input coordinates, and a scanning signal is applied to each electrode of the tablet. a means for extracting a predetermined number of detection signals from the output signals of the input pen by changing a threshold value for the output signal of the input pen or the level of the scanning signal; and based on the detection signals, the input pen comes into contact with the input pen. 1. A tablet input device comprising: means for generating coordinate information; and means for invalidating the coordinate information when the coordinate information relates to the dummy electrode.