JPH0340859B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field to which the invention pertains] The present invention relates to a tablet input device, and in particular, detects the coordinates of one contact of a signal detection pen at least twice, collates the results, and performs detection. The present invention relates to a tablet input device that determines whether a result is valid or invalid.

[Prior art and its problems]

In order to prevent malfunctions caused by noise, etc., tablet input devices usually detect coordinates at least twice.
This is repeated several times, and when the results match, the detected coordinates are considered valid for subsequent processing (see Japanese Patent Publication No. 53-37163). However, with conventional devices, such as capacitively coupled tablets,
If the wave height of the detection pulse is slightly higher than the threshold value, such as when a pen touch is made at the boundary between electrodes, slight movement of the pen tip or slight change in the indentation of the sheet may occur. Therefore, during coordinate detection operation for data check, the peak value of the detection pulse may become lower than the threshold value, and coordinate re-detection may not be performed accurately.
In particular, a device that detects coordinates while changing the height of the scanning pulse (Japanese Patent Application No. 57-189476.
189477), this tendency was strong because the height was controlled to approach the threshold.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned disadvantages of the prior art, and it is an object of the present invention to provide a tablet input device that can accurately detect coordinates when checking data.

[Summary of the invention]

Therefore, in the present invention, in a tablet input device that detects coordinates at least twice for one pen contact, collates the results, and determines whether the detection result is valid or invalid, it is possible to detect coordinates at the time of data check. A control circuit that sends out a drive level designation signal so that the drive level of the scanning signal that drives the electrode lines of the tablet is slightly higher than the drive level that is used for coordinate detection during data latching, and a The above object is achieved by adopting a configuration including a drive level switching circuit for switching the drive level.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described based on FIGS. 1 to 6.

FIG. 1 is an electrical block diagram showing 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 to Xn and Y electrode groups Y ₁ to Yn are arranged. When the input pen 4 is brought into contact with the tablet 1, the pen switch 4A is closed and the counter 7 is activated by the action of the control circuit 20.
The counted value of this counter 7 is sent to the X or Y electrode drive circuit 2 or 3 via the gate 8, and each
Scanning of X ₁ to Xn or Y electrodes Y ₁ to Yn is performed. The X and Y electrode drive circuit 2,
3 is connected to a drive level switching circuit 31 via a gate 30. The drive level switching circuit 31 is supplied with the power supply voltage Vcc, and performs, for example, D-A conversion in accordance with the drive level designation signal (digital signal) input from the control circuit 20, and converts the corresponding analog voltage. occurs, and the X
Alternatively, it has a function of outputting as a power source for driving the output stage of the Y electrode drive circuit 2 or 3. In detail, the drive level switching circuit 31
The distance between Qmin and maximum level Qmax is 2・K (K=
1, 2,...), and an analog voltage higher than these analog voltages by ΔV as described later. ,3
is the drive level switching circuit 31 via the gate 30.
A scanning pulse whose peak value is an analog voltage input from the electrodes can be outputted to the X and Y electrode groups X ₁ to Xn and Y ₁ to Yn. The gate 30 receives x, y signals sent from the control circuit 20 in synchronization with the gate 8.
Switching is controlled by a scan switching signal.

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. A predetermined threshold voltage SO set by a semi-fixed resistor R is input to the other input terminal of the comparator 10.

The output of the comparator 10 is sent to a gate 12 and a counting circuit 23 via a shaping circuit 11. This counting circuit 23 selects a detection signal which is selected by the comparator 10 as a detection signal equal to or higher than a threshold level while one electrode group of the X electrode group X ₁ to Xn or the Y electrode group Y ₁ to Yn is scanned once. It has a function of counting detected signals, and this counted value is sent to the control circuit 20. Then, when the count value of the counting circuit 23 after one round scanning is other than "1", this control circuit 20 sends a drive level designation signal different from the previous one to the drive level switching circuit 31 according to the count value, In addition to raising or lowering the wave height of the scanning pulse, the same electrode group as the previous scan is re-scanned. This operation is performed by the comparator 10 by scanning the same electrode group in one cycle.
The maximum level detection signal can be obtained by repeating the process until one detection signal is output from the input pen 4 (the count value of the counting circuit 23 becomes "1"). This is due to the scanning pulse of the electrode closest to the contact area (the key segment designated by the input pen 4).When the maximum level detection signal is obtained, the control circuit 20 performs the next data check. , a drive level designation signal is sent to the drive level switching circuit 31 to vary the drive level so that the drive voltage is set to a slightly higher drive voltage than the drive voltage at which the maximum level detection signal was obtained. Details of the variable operation 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 switches the drive level switching circuit 31 to the drive level switching circuit 31 for data checking.
Slightly increase the output level as described above,
The gate 12 is switched to the comparator 14 side, and the electrode group is rescanned. As a result, the detection signal is input as a comparison timing signal to the comparator 14 via the gate 12, and the comparator 14 compares the count value of the counter 7 and the output data of the latch circuit 13 at the timing when the detection signal is input, When a match occurs, a match signal is output. Therefore, the output data of the latch circuit 13 when the comparator 14 outputs a coincidence signal is outputted to the computer main body or the like (not shown) as correct coordinate data.

The operation of varying the output level of the aforementioned X or Y drive circuit 2 or 3 is performed as follows. Here, the drive level at the time of data latch is the maximum/minimum output of the drive level switching circuit 31.
Level V ₁ to V ₈ that divides Qmax to Qmin into 8 equal parts
Let us take as an example a case where X coordinate data related to the contact area of the input pen 4 is detected.

First, the control circuit 20 specifies a drive level of V ₅ =(Qmax-Qmin)·1/2 before applying a scanning pulse. Then, the gates 8 and 30 are connected to the X 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 Xn. At this time, if the signal detected by the input pen 4 becomes 1 in FIG. 2, 1 in FIG. 3, or 1 in FIG. 4 depending on the contact position or state of the input pen 4, each The values counted by the counting circuit 23 are "1", "2", and "0". In other words, 1 in FIG.
_P1 in the figure) shows the output of the amplifier 9, and there is only one detection signal exceeding the threshold SO (see 2 in Figure 2). This detection signal ai is due to a scanning pulse applied to the electrode xi of the contact portion of the input pen 4. When one cycle of scanning of the X electrode group is completed, "1" is input from the counting circuit 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 is then started. Bye.

On the other hand, 1 in Fig. 3 is a case where the input pen 4 is brought into contact near the boundary of the key segment KS (Fig. 5).
(see P ₃ ), and the signal exceeding the threshold SO is 2
There is one (see Figure 3 2). At this time, the count value is “2”
is sent to the control circuit 20, so the control circuit 2
0 lowers the drive level and V ₃ = (Qmax − Qmin)・
Specify a drive level of 1/4 and apply a scanning pulse to the X electrode group again. This time, the detection signal exceeding the threshold is 1 (see FIGS. 3 and 4), so the count value becomes "1", and the selection of the detection signal of the maximum level is completed in the same way as described above. This detection signal is due to the scanning pulse applied to the electrode xi closer to the input pen 4 (key segment KS designated by the input pen 4).

1 in Fig. 4 is a case where the overall detection level has decreased for some reason, such as when the sheet placed on the tablet 1 is thick, and the threshold value
A detection signal exceeding SO is 0 (see FIG. 4, 2). At this time, the count value "0" is input to the control circuit 20, so the control circuit 20 increases the drive level, specifies V ₇ = (Qmax - Qmin) 3/4, and again applies a scanning pulse to the X electrode group. Apply. Then, there is one detection signal that exceeds the threshold SO (Fig. 4, 3,
4), therefore, the count value becomes "1", and the scanning pulse applied to the electrode xi associated with the key segment KS (x=i) designated by the input pen 4 is detected in the same manner as described above.

In this way, for a certain threshold value, the counting circuit 2
When the count value of 3 is "2" or more, the drive level is lowered, and when it is "0", the drive level is increased, and by changing the drive level asymptotically, the maximum level that exceeds the threshold SO is A detection signal can be obtained.

As described above, when "1" is input from the counter 23 to the control circuit 20, it is known that the selection of the maximum level detection signal, that is, the data latch operation has been completed, and the data check operation then begins. At this time, the control circuit 20 controls the drive voltage V _Lo (n=1 to 8 in this embodiment) at the time of data latch.
Drive voltage V _Co slightly higher than ΔV (however, n=1~
8), a drive level designation signal is output to the drive level switching circuit 31. That is, during a data check, the drive voltage is operated in stages from 1 to 8, just like when data is latched, and this stage is determined by the general formula V _Co = V _Lo + ΔV (for example, V _C1 = V _L1 +
ΔV).

As a result, even if the height of the detection pulse ai- _C at the time of data check, which should normally be at the height H _CD , is reduced by H _D due to the above-mentioned causes, it will still be at the height H _CM. is kept higher than the threshold value So, so that the control circuit 20 can perform a data check, that is, determine whether the coordinates related to the detection pulse a _Lo and the coordinates related to the detection pulse a _Co match or do not match. (See Figure 6).

After a series of processes related to the X coordinate data are performed in this way, the control circuit 20 then connects the gates 8 and 30 to the Y electrode drive circuit 3 side, scans the Y electrode group, and performs the same operation as described above. Then Y
After selecting the detection signal of the maximum level related to the coordinates, a series of processes related to the Y coordinate data related to the contact area of the input pen 4 is performed without performing a data check.

In the above-mentioned embodiments, a detection method is described in which the drive level is varied when data is latched; however, the present invention is not limited to this, and the drive level is fixed when data is latched. It's okay. Further, the present invention is applicable not only to the capacitive coupling method but also to other methods such as an electromagnetic coupling method.

〔Effect of the invention〕

As described above, according to the present invention, in a tablet input device that detects the coordinates of one pen contact at least twice, collates the results, and determines whether the detection results are valid or invalid, A control circuit that sends out a drive level designation signal so that the drive level of a scanning signal that drives and scans the electrode lines of the tablet during coordinate detection is slightly higher than the drive level that is used to detect coordinates during data latch, and the drive level designation. By adopting a configuration that includes a drive level switching circuit that switches the drive level based on the signal, coordinates can be detected accurately during data checks, and errors may occur even if the pen is touched correctly. It is possible to provide a tablet input device that does not cause such problems.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the tablet input device according to the present invention, and FIG. 2 shows the amplifier and comparator shown in FIG. 1. FIG. 5 is a partial plan view showing a part of the tablet shown in FIG. 1, and FIG. 6 is an explanatory diagram showing the amplifier outputs during data latch and data check. . 20...control circuit, 31...drive level switching circuit.

Claims (1)

[Claims] 1. In a tablet input device that detects the coordinates of each pen contact at least twice and compares the results to determine whether the detection results are valid or invalid, the tablet's electrodes are A control circuit that sends out a drive level designation signal so that the drive level of a scanning signal for driving and scanning a line is slightly higher than the drive level during coordinate detection during data latch, and switching the drive level based on this drive level designation signal. A tablet input device characterized by comprising a drive level switching circuit for performing the following.