JPH04181418A - Pressure sensitive coordinate input device - Google Patents

Abstract

PURPOSE:To improve ability for recognizing characters by correcting a signal showing the coordinates of an input point to be outputted from a pressure sensitive tablet corresponding to pen pressure, and averaging read coordinate data. CONSTITUTION:This device is composed of a pressure sensitive tablet 101, driver circuit 102, A/D converter 103, tablet voltage detecting circuit 104, CPU 105, ROM 106 and RAM 107. In this case, when force pressing the pressure sensitive tablet 101 with an input pen 30, namely, the pen pressure is weak, contact resistance between resistance sheets 10 and 20 is enlarged and the signal outputted from the pressure sensitive tablet 101 does not exactly show the position of the input point. Therefore, this signal is read plural times after being corrected corresponding to the pen pressure. Further, the result of averaging the plural obtained signals is defined as the coordinates of the input point. Thus, even in the case of generating chattering when the pen pressure is weak or when the sensitivity of the pressure sensitive tablet 101 is not uniform, the coordinates of the input point can be exactly read.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a coordinate input device for handwritten character recognition used in computers such as OA (office automation) equipment.

[Prior Art] In a pressure-sensitive coordinate input device, chattering occurs when a pen is lowered and raised on a tablet made of two resistive strips. In addition, when the writing pressure is small, the contact resistance between the resistance sheets varies, so chattering occurs even when the pen is in the ON period, that is, while the pen is moving on the tablet. Furthermore, chattering may occur if the sensitivity of the tablet is not uniform.

If chattering occurs, the coordinates of the read points will be unexpected values, which will have a negative impact on character recognition. Therefore, in the conventional pressure-sensitive coordinate input device, when chattering occurs due to hardware or software processing, the coordinates of the input point, that is, the point pressed by the pen, are not read.

[Invention or problem to be solved] Generally, when inputting strokes with a pen, especially when inputting straight strokes, the pen pressure is not constant;
The pen pressure at the midpoint between the start and end points becomes weaker. If the pen pressure becomes weaker than a certain level, the coordinates of the input point cannot be read correctly, so in conventional devices, such input points are excluded from the data for recognizing handwritten characters.

Therefore, with the above-mentioned conventional device, if the pen pressure is weak, the data at the intermediate point will be lost, and if the number of sampling points is small, the data will be divided into, for example, a straight line of one stroke or a straight line of two or more strokes. There is a problem that the characters are read and the character recognition process cannot be performed correctly.

The present invention has been made in view of the above problems, and provides a pressure-sensitive coordinate input device that can accurately read the coordinates of an input point even when the pen pressure is small and when the sensitivity of the pressure-sensitive tablet is uneven. It's about doing.

[Means for Solving the Problems] The object of the present invention is to provide a pressure-sensitive coordinate input device having a pressure-sensitive tablet made of a resistive sheet, in which a signal representing the position of an input point outputted from the pressure-sensitive tablet is provided. This is achieved by a pressure-sensitive coordinate input device characterized by comprising means for correcting the signal according to the writing pressure, and means for averaging the corrected signal.

[Effect] If the force of pressing the pressure-sensitive tablet with the input pen, that is, the writing pressure, is weak, the contact resistance between the resistance sheets will increase, and the signal output from the pressure-sensitive tablet will no longer accurately indicate the position of the input point. Therefore, this signal is read multiple times after being corrected according to the pen pressure.

Furthermore, the coordinates of the input point are determined by averaging the obtained plurality of signals. This allows the coordinates of the input point to be read accurately even if chattering occurs when the pen pressure is weak or the sensitivity of the pressure-sensitive tablet is uneven.

[Embodiments] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 2 is a perspective view showing the general structure of a pressure-sensitive tablet made of a resistance sheet.

In the figure, lO is a resistance sheet for reading the X coordinate, 2
0 is a resistance sheet for reading the Y coordinate, and 30 is a pen for input. As shown in FIG. 3(A), terminals XH and XL are attached to the left and right ends of the resistance sheet IQ, respectively, and terminals YH and XL are attached to the upper and lower ends of the resistance sheet 20, respectively.
and a terminal YL are attached, respectively.

The check operation performed prior to reading the coordinates of the input point, that is, the determination of whether the pen or tablet is being pressed, is performed using the terminal as shown in the check mode column of FIG. 3(B). Apply a voltage of 5V to Xll, and connect the other terminal
This is executed by leaving L, YH, and YL open (floating), respectively, and reading the voltage at terminal YL in this state via an A/D converter (not shown). When the pen is pressing the tablet, resistor sheets 10 and 2
0 touch each other, the voltage at terminal YL is approximately 5V.

To read the X coordinate of the point pressed by the pen, that is, the input point, set the terminal XH to 5v1 and the terminal Terminals Yli and YL are opened, and the voltage at terminal YL is measured in this state. At this time, the voltage of the resistive sheet 20 becomes equal to the voltage of the point on the resistive sheet 10 that is pressed by the pen.

Since the voltage at the point on the resistive film C hlo where the pen is placed increases in proportion to the distance from the terminal XL, it is possible to read the X coordinate.

Similarly, when reading the Y coordinate of the input point, see Figure 3 (B
), set terminal Y[I to 5V, terminal YL to Ov, open terminals XH and XL, and measure the voltage at terminal XL in this state.

FIG. 4 is a block diagram of an embodiment of the pressure-sensitive coordinate input device of the present invention. In the figure, 101 is a pressure-sensitive tablet;
+02 is a driver circuit that drives the pressure-sensitive tablet 101, 103 is an A/D converter that converts the voltage signal output from the pressure-sensitive tablet into a digital signal when reading an input point, and 104 is a circuit that indicates whether the input pen 3o is on or off. A tablet voltage detection circuit for detecting which state the tablet is in, that is, whether or not the pen is pressing the tablet, and also detecting whether chattering has occurred when the pen 30 is in the on section; 106 is a ROM (read-only memory) that stores a control program for the device; 1.7 is a RAM (random access memory) for temporarily storing various data when using the device; 105
is a CP (central processing unit) for controlling the entire device.

FIG. 5 shows the timing of operation of each mode of the pressure-sensitive tablet. In the figure, C represents a pen check operation, and X and )' represent X and Y coordinate reading operations, respectively.

FIG. 6 shows an example of a temporal change in the value of the output voltage of the terminal XL when the input pen 30 presses the pressure-sensitive tablet 101 during a check operation. In the same figure, T2O1
indicates the chattering period when the pen or tablet is moved from the off state, i.e., the pen or tablet is away from the pen or tablet, to the on state, i.e., the pen or tablet is pressed, and T2O2
indicates the chattering period when the pen changes from the on state to the off state. Further, T2O3 indicates a chattering period that occurs while the pen is in the ON period, and this occurs when the writing pressure is weak or when the sensitivity of the pressure-sensitive tablet is uneven. When the pen pressure is normal, the output voltage remains at 5V (hereinafter referred to as VC) 1 during the on period.

Next, the operation of the pressure-sensitive coordinate human power device having the above configuration will be explained as follows.
The explanation will be given according to the flowchart shown in the figure.

First, in Step S], set the pressure-sensitive tablet to the third prong (B) check mode, convert the voltage at terminal Y5 (hereinafter referred to as check voltage V TAB) to A/1) and read it, then turn off the pen. It is determined whether the state has changed from the on state to the on state. Here, the check voltage VTAB and the predetermined threshold voltage VSH are compared n times in succession (5, always VTAB
If VSH is always higher than VTAB, it is determined that the pen is in the on state. Conversely, if VSH is always higher than VTAB, it is determined that the pen is in the off state. In step S1, the comparison is repeated n times in succession until it is determined that the pen is in the on state.

When it is determined that the pen is in the on state, the process proceeds to step S2, where the X coordinate reading mode is set and the voltage C of the terminal YL (hereinafter referred to as VXIN) is converted into A,/D and read.

In the next step S3, chattering in the ON period (721 in Fig. 6)3), which occurs due to weak pen pressure or uneven sensitivity, is compensated according to the following formula1, and VXIN is changed to VX
Correct to.

VX-(Vcc/VTAB) ・VXIN
Next, in step S4, the same process as step S1 is performed,
It is determined again whether the pen is in the on state. At this time, if it is determined that the pen is not in the on state, step S
1 and do not read the coordinates of this input point. If it is determined in step S4 that the pen is in the on state, the process advances to step S5 to set the X coordinate reading mode and
-XL voltage (hereinafter referred to as VYIN) is converted into A7D and read. Next, in step S6, in order to compensate for chattering as in step S3, VYIN is corrected to VY according to the following equation.

VY: (Vcc/VTAB) ・VYIN In the above equation, VTAB is the check voltage obtained in step S4.

The check operation is performed again in step S7. If it is determined that the pen is not in the on state, the process returns to step S1 and the coordinates of this input point are not read. Step S
If it is determined in step S7 that the pen is in the on state, the process advances to step S8. In Ste-Tubu S8, the coordinate data of the input point,
That is, in order to average the values of VX, ~'Y in the next step S9, each of the above steps is set to 0 for one input point.
Repeat once to obtain m coordinate data.

In step S9, the average value of the m pieces of coordinate data is calculated, and among these m pieces of data, those that are ahead of the average value by a predetermined value or more are replaced with this average value, and then the m pieces of coordinate data are calculated again. Calculate the average value of the data. Then, the average value of this and the previously calculated average value of m points is taken, and this is used as the coordinate data of the input point. Thereby, the convergence point of m pieces of data can be set as the coordinates of the manual point.

FIG. 7 shows the pressure-sensitive coordinate human-powered device of the above embodiment,
Figure 8 shows the reading results of an input point input with weak pen pressure without voltage correction and averaging processing, and Figure 8 shows the same result when voltage correction and averaging processing were performed on the same pressure-sensitive coordinate input device. and shows the reading results of the input points. From these figures, it can be seen that the coordinates of input points input with weak pen pressure are read more accurately by voltage correction and averaging processing.

[Effects of the Invention] The pressure-sensitive coordinate input device of the present invention, depending on the pen pressure,
It is configured to correct the signal indicating the coordinates of the input point output from the pressure-sensitive tablet and average the read coordinate data, so it can be used in cases where the pen pressure is weak or the sensitivity of the pressure-sensitive tablet is uneven. This has the effect that the number of missing reading points is smaller than that of conventional devices, which contributes to improving character recognition ability.

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing the operation of the pressure-sensitive coordinate input device of the present invention, FIG. 2 is a perspective view showing the general configuration of a pressure-sensitive tablet, and FIGS. FIG. 4 is a block diagram showing the configuration of the pressure-sensitive coordinate input device of the present invention, and FIG. 5 is a diagram showing the operation of the pressure-sensitive coordinate input device in each mode of the present invention. 6 is a diagram showing an example of the temporal change in the writing pressure of the input pen. FIG. 7 is a diagram showing the reading results of input points when voltage correction and averaging processing are not performed. FIG. 8 is a diagram showing the reading results of input points when voltage correction and averaging processing are performed. 10.2G...Resistance sheet, 3o...
Input pen, 1lli...pressure sensitive tablet, 1.
02...Driver circuit, 1゜3...A
/D converter, 104... Tablet voltage detection circuit, 105 .=-CPU, 106 =-= RO
M, IO". ...RAM0 Agent Patent Attorney Funa Yamatake No. 1 = Page 4 - Time Figure 5 Figure 6, j+-+ ・tsu'''7'''-0! −・ F 1, - transfer /gu'ゝ

Claims (1)

[Claims] A pressure-sensitive coordinate input device having a pressure-sensitive tablet made of a resistance sheet, the device comprising: means for correcting a signal representing the position of an input point outputted from the pressure-sensitive tablet according to pen pressure; and the corrected signal. A pressure-sensitive coordinate input device characterized by comprising: means for averaging.