JP2622989B2 - Tablet device - Google Patents

Description

The present invention relates to a tablet device for inputting handwritten information to an information device such as a computer.

(B) Conventional technology As a tablet device for inputting handwritten information, a resistance type device which can obtain input coordinate information with a relatively simple structure is generally used. As such a conventional tablet device, there are a voltage switching method, a current division method, and the like that are found in the National-Technical Report. In this case, the resolution per unit length depends on the quantization accuracy of the A / D converter of the coordinate judging unit, but an A / D converter with a high quantization accuracy (more than 8 bits) is extremely expensive. Since the amount of data processing also increases, an 8-bit A / D converter is used for a low-priced tablet, and the number of detection position points is set to 256 or less for both the X and Y axes at present.

In general, in inputting an image such as a drawing, it is common to use image data which is written in a large size and then reduced to a predetermined size. On the other hand, the character input size for character recognition should not be extremely different from the normal time (an input size that is considerably smaller than image input) in view of ease of use, fatigue, and recognition rate. The former may have a coarse resolution per unit length, but the latter must have a high resolution, and contradictory conditions are required for using the same tablet.

In the conventional tablet device as described above, the resolution of a limited area on the tablet cannot be set to high resolution, so that an A / D converter with high quantization accuracy must be used and the device becomes expensive. There were drawbacks.

(C) Problems to be Solved by the Invention The present invention has been made in view of the above-mentioned circumstances, and allows a large-size image input to be performed even when an inexpensive A / D converter is used for a coordinate determination unit. On the other hand, by setting only a limited area on the tablet to a high resolution, a small character input size that is the same as that in a normal case can be realized in character recognition.

(D) Means for Solving the Problems The present invention provides a plurality of coordinate detection plates for detecting the coordinates of a plurality of axes, a detection plate control unit for controlling the detection plates, and a detection signal obtained from the detection plates. In a tablet device consisting of a coordinate determination unit that determines coordinates based on and outputs a result, and an instruction unit that receives a predetermined operation instruction from an external instruction or a switch on the main body, etc.
The resolution per unit length or the coordinate detection area on the detection plate is changed by changing the reference voltage of the A / D converter.

(E) Function Since the present invention is configured as described above, the resolution per unit length can be changed using a low-cost A / D converter with low quantization accuracy, and the coordinate detection area on the coordinate detection plate can be changed. Can be free.

(F) Embodiment FIG. 1 shows an embodiment of the tablet device. An X electrode (11) is arranged on the X-axis coordinate detection plate (1), and a Y electrode (21) is also arranged on the Y-axis coordinate detection plate (2). Controlled by 3). When there is a press input on the tablet, a detection signal obtained from the detection plate is transmitted to the coordinate determination unit (4) via the detection plate control unit (3), where the coordinates are determined and the result is output. The operation of the tablet is transmitted from the instruction unit (5) that has received the operation switch signal (51) on the tablet or the external instruction signal (52) to the detection plate control unit (3).

FIG. 2 shows the relationship between the X-axis coordinate detection plate (1), the Y-axis coordinate detection plate (2), and the detection plate control unit (3) when the voltage switching method shown in FIG. 1 is adopted. It is shown. X-axis and Y-axis coordinate detection plates (1),
(2) is a resistance sheet type structure in which two sheets of conductive rubber on which dot-shaped insulating spacers and mesh-shaped insulating spacers are formed are interposed therebetween and arranged. First, the X electrode changeover switches (311) and (312) in the detection plate control unit (3)
And the Y electrode change-over switches (321) and (322) are selected to the position, and the voltage Vx is applied to both ends of the X electrode (11) of the X-axis coordinate detection plate (1) as the upper resistance sheet.
When there is a pressing input on the tablet, the partial pressure of the applied voltage Vx of the X electrode (11) at the pressing input point P, that is, the analog information of the Y coordinate is converted into the Y information of the Y-axis coordinate detecting plate (2) as the lower resistance sheet. It can be detected from the electrode (21).

Next, the Y-electrode changeover switch (32
1), (322) to the position, and the X electrode changeover switch (31
1) and (312) are selected at positions, and a voltage is applied to both ends of the Y electrode (21) of the Y-axis coordinate detection plate (2) which is a lower resistance sheet.
Vy is applied. When there is a press input on the tablet, the partial pressure of the applied voltage Vy of the Y electrode (21) at the press input point P,
That is, analog information of the X coordinate can be detected from the X electrode (11) of the X-axis coordinate detection plate (1), which is the upper resistance sheet. As described above, the time division corresponds to the pressure input position by the method of detecting the partial pressure of the X-axis coordinate detection plate (1) and the Y-axis coordinate detection plate (2) through the electrodes of the coordinate detection plates on the opposite sides. Analog information of the X coordinate and the Y coordinate can be obtained. This analog information is transmitted to a coordinate determination unit (4) via a detection plate control unit (3), and the analog information is converted to a reference voltage (42) by an A / D converter (41) in the determination unit shown in FIG. Is compared with the set value Vs, and is converted into digital information, and a coordinate determination result is output. Generally, the set value Vs of the reference power supply (42) of the A / D converter (41) is set to be the maximum value of the input analog information. In this example, Vx = Vy = Vs. When the quantization accuracy of the A / D converter (41) is 8 bits, the number of detection position points on both axes is 0 to 255
Becomes

In the above description, two X-electrode changeover switches (311) and (3
12) Or two Y-electrode changeover switches (321) and (32)
2) The coordinate information of the X-axis coordinate detection plate (1) and the coordinate detection plate of the Y-axis (2) are both coordinated such that the entire detection plate is 0 to 255 by simultaneously linking to the X, Y, or position. States that you can get

The feature of the embodiment of FIG. 2 is that the voltages applied to the X electrodes (11) and (11) and the Y electrodes (21) and (21)
Vx and Vy can be variably selected. As shown in FIG. 3, when the reference voltage Vs of the A / D converter (41) of the coordinate determination unit (4) is used as shown in FIG. Vx = Vy = Vs to Vx =
Switching can be changed to Vy = 2Vs.

The A / D converter quantizes an input voltage of 8 bits or less at a reference voltage Vs or less into 256 steps. Therefore, the fourth
As shown in the figure, in the region where the input to the A / D converter exceeds the reference voltage Vs, the detection is saturated and the maximum value of 255 is output. As described above, when the applied voltage is 2 Vs, the coordinates can be detected as values of 1/4 section Q1 (shown by hatching) 0 to 255 of the detection plate in FIG.

In other areas Q ₂ , Q ₃ and Q ₄ , the output of the A / D converter is 2
It becomes 55. In this case, since the quantization accuracy of the A / D converter (41) is the same 8 bits, the resolution per unit length in the shaded area is twice as large as in the case where the entire coordinate detection plate is used. If the analog information input of the A / D converter (41) is restricted, a coordinate input restriction circuit (6) shown in FIG. 3 may be provided. This can be easily constituted by an element having a constant voltage function such as a Zener diode.

In this example, the set voltage value Vs is fixed and the applied voltages Vx and Vy are changed.On the contrary, in the present invention, the applied voltages Vx and Vy are fixed, and the reference voltage value Vs is variably set, for example, by half. The same effect can be obtained even with the above (see FIG. 6).

These voltages are changed using a changeover switch for changing the fixed value and a variable volume for changing the direction. The switch and the volume may be provided in the tablet device main body, or may be configured to receive the same change instruction as described above from a control device outside the main body.

By changing the polarities (±) of the applied voltages Vx and Vy and applying the doubled voltages Vx and Vy, high-resolution image information can be obtained in a region different from the above example (for example, Q _{4 in} FIG. ₄ ). (See FIG. 7). By using the above method even when using an inexpensive A / D converter in this way, when inputting images such as diagrams, use the entire tablet,
The input area for character recognition is part of the tablet surface,
By setting the area to have a high resolution, it is possible to realize an input device having a character size close to a normal state and a high recognition rate.

(G) Effects of the Invention As is clear from the above description, the tablet device of the present invention has a function of switching between the input area and the resolution with a simple circuit configuration, so that a large area can be changed from an image input to a small handwriting input. It is possible to input according to the purpose up to. Therefore, a high-performance and low-cost tablet device can be realized without using an expensive multi-bit A / D converter.

[Brief description of the drawings]

FIG. 1 is a configuration diagram for explaining the tablet device. FIG. 2 is a diagram illustrating the principle of coordinate detection. FIG. 3 is a main part configuration diagram showing an example of a coordinate determination section. FIG. 4 is a schematic diagram showing a coordinate detection area. FIG. 4 is a schematic diagram showing a coordinate detection area. FIG. 5 is a diagram for explaining the configuration of the example, FIG. 6 is a diagram for explaining the operation of coordinate determination according to the embodiment of the present invention, and FIG. 7 is a diagram for explaining another operation of coordinate determination. (1) X-axis coordinate detection plate, (2) Y-axis coordinate detection plate, (3) detection plate control unit, (4) coordinate determination unit, (5) instruction unit , (11) ... X electrode, (21) ...
Y electrode.

Claims (1)

(57) [Claims] 1. A plurality of coordinate detection plates for detecting coordinates of a plurality of axes, a detection plate control unit for controlling the detection plates, and a result of determining coordinates based on detection signals obtained from the detection plates. A tablet device comprising: a coordinate determination unit that outputs a command; and an instruction unit that receives a predetermined operation instruction from an external instruction or a switch on the main body. In accordance with an instruction from the instruction unit, the reference of the A / D converter in the coordinate determination unit A tablet device characterized by changing a resolution per unit length or a coordinate detection area on the detection plate by changing a voltage.