JP2707254B2 - Input device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an input device configured by combining two transparent sheet-shaped panels. [Prior Art] A conventional input device using a finger, a pen, or the like has a structure in which an upper panel 1 made of a film or glass having a surface provided with an overall electrode 40 as shown in FIG.
And a lower panel 2 made of glass subjected to the above-mentioned method, and combined such that the entire surface electrodes face each other and bonded together via a spacer or the like. Electrode terminals 42 and 43 are formed at both ends of the full-surface electrode 40, and electrode terminals 44 and 45 are similarly formed at both ends of the full-surface electrode 41. These electrode terminals are arranged in a direction orthogonal to the upper panel and the lower panel. FIG. 3 shows an example of a drive circuit used in the above input device. That is, 3-8 in the figure are transistors, 9-20, 31, and 32 are resistors, 21 and 22 are ceramic capacitors, and terminals 23 and 24 are applied with a voltage of, for example, 5V. Terminal 2
Reference numerals 5 and 27 are control input terminals for controlling the switching of the transistors 3 to 8. Terminals 26 and 30 are voltage detection output terminals. First, the outline of the operation principle will be described. <Detection of X Coordinate> 5 V is applied to one electrode terminal of the lower panel 2 and 0 V is applied to the other electrode terminal to generate a uniform potential gradient on the resistance surface (over the entire surface of the electrode). One electrode terminal is connected to an AD converter (not shown in FIG. 5), and the other electrode terminal is in a floating state (connected transistor is OFF)
And Here, when a pressing operation is performed from the upper panel 1 side, the entire surface electrodes 40 and 41 of the upper panel 1 and the lower panel 2 contact at the pressing point, and a potential corresponding to the X coordinate of the pressing point is transmitted to the upper panel 1. Can be This potential is digitized using an AD converter and output as an X coordinate value. <Detection of Y Coordinate> On the other hand, detection of the Y coordinate is performed by the upper panel 1 and the lower panel 2.
And the same operation as the X coordinate detection is performed. The pressing point position is detected by repeating these operations alternately and continuously.
No. 290522, page 2 and FIG. 5). In FIG. 3, a control method for detecting the X coordinate and then detecting the Y coordinate will be described below. + For terminals 23 and 24
Apply a voltage of 5V. To detect the X coordinate, connect +
Apply a 5V signal and a ground (GND) level signal to terminal 27. Then, the transistors 3 to 5 are turned on, and the transistors 6 to 8 are turned off. That is, the lower panel 2 has X
A voltage is applied in the direction, and the voltage distribution is proportional to the distance in the entire surface electrode 41. And the upper panel 1
For example, when pressed with a finger or a pen or the like, the lower panel 2 comes into contact with the lower panel 2. Is detected by To detect the Y coordinate,
First, a GND level signal is input to the terminal 25, and a + 5V signal is input to the terminal 27. Then, the transistors 3 to 5 are turned off, and the transistors 6 to 8 are turned on. That is, a voltage is applied to the upper panel 1 in the Y direction, and the Y
The voltage at the pressing point in the direction can be detected. Where the resistance
31 and 32 have a role of releasing unnecessary charges stored in the stray capacitance of the detection side panel (upper panel or lower panel) and stabilizing the panel potential. However, at the same time, since this resistor is connected in series between the contact resistance between the panels and GND, a problem occurs in that the potential at the pressing point is divided by the resistance and input to the AD converter. Therefore, in order to solve the latter problem at a practical level, resistors 31 and 32 must be used.
Is preferably as large as possible (for example, 5 MΩ). The ceramic capacitors 21 and 22 are used to speed up the switching of the transistors 4 and 7, and use capacitors having a small capacitance (for example, 22PF). [Problems to be Solved by the Invention] However, in the above-mentioned conventional technology, for the operation of detecting the voltage at the position of pressing one side of the full-surface electrode on the opposite side, for example, the full-surface electrode of the upper panel A voltage of 5 V is applied between both sides of the panel, and in the next stage, the panel becomes a side that detects the potential at the position of the pressed point on the opposite side. That is, it had a certain voltage level to switch simultaneously from + 5V and GND. To explain this point in more detail, during the operation of detecting the X coordinate as in the above-described example, since the lower panel is driven at 5 V and 0 V, a constant current flows between the electrodes. When switching from the X-coordinate detection operation to the Y-coordinate detection operation, an induced current is generated due to interruption of driving by 5V and 0V, and electric charges are stored in a floating capacitance existing between the upper panel and its wiring and peripheral members. . In the Y coordinate detection operation, since the upper panel is simply grounded to the AD converter with a high resistance such as an input resistance or an OFF resistance of a transistor, the stored charge remains for a long time. In this case, there is a problem that the upper panel has some potential even if the pressing operation is not performed, so that it cannot be distinguished from the pressing operation. Also, even when the pressing operation is performed, if the contact resistance of the upper and lower panels is large or the detection operation is performed at high speed, the potential of the upper panel fluctuates until it reaches the correct level according to the pressed position. However, there is a problem that a correct coordinate value cannot be obtained.
A similar phenomenon occurs when the operation is switched from the Y coordinate detection operation to the X coordinate detection operation. For the above reasons, accurate voltage detection is not possible.
Therefore, there has been a problem that accurate position coordinates cannot be detected. The present invention has been made to solve such a problem, and an object of the present invention is to provide an input device capable of detecting an accurate voltage at a pressing point. [Means for Solving the Problems] The input device of the present invention has a pair of panels having an entire surface formed on the inner surface and electrode terminals provided at both ends thereof opposed to each other. Voltage applying means for applying a predetermined voltage level and a voltage at the GND level to form a voltage distribution on the surface thereof, and switch means for opening and closing voltage application from the voltage applying means to the electrode terminal, When the full-surface electrodes formed on the pair of panels come into contact with each other, in an input device that detects a contact position from the voltage obtained by the other full-surface electrode and the voltage distribution, a voltage is applied to the full-surface electrodes of one panel. Before detecting the voltage from the electrode terminal of the other panel via the contact point of the full-surface electrode, control the switch means so as to apply the voltage of the GND level to the full-surface electrode of both panels. It is characterized in. [Operation] According to the above configuration, the entire surface electrodes of both panels are once grounded.
To keep the level, without having any potential,
In the next step, the voltage at the opposing pressing point can be accurately detected. Embodiment FIG. 1 is a diagram illustrating an example of a drive circuit according to an embodiment of the present invention. 1 is the upper panel, 2 is the lower panel, 3 ~
8 is a transistor, 9 to 20 are resistors, and 21 and 22 are ceramic capacitors. For example, a voltage of 5 V is applied to the terminals 23 and 24. Terminals 25 to 28 are control input terminals for controlling the switching of the transistors 3 to 8. Terminals 29 and 30 are voltage detection output terminals. Hereinafter, a control method for detecting the X coordinate and the Y coordinate will be described with reference to Tables 1 and 2 and FIG. First, when detecting the X coordinate, as shown in Table 1, the terminals 25 to 28 are controlled in the initial state → STEP1 → STEP2. That is, in the initial state, the terminals 25, 26, 27, 28
Transistors 3, 4, 6, and 7 are OFF because they are V, 0V, and 5V
Thus, the transistors 5 and 8 are turned on. Therefore, the upper panel and the lower panel are electrically maintained at the GND level. Next, at the stage of STEP1, the transistors 3 and 4 are turned on. That is, a voltage is applied to the entire surface electrode in the X direction. At this time, the upper panel on the voltage detecting side is kept at the GND level. Next, at the stage of STEP2, the transistor 8
FF. That is, the voltage at the pressing point position in the X direction from the terminal 30 is detected. Then, as the next stage, the Y coordinate is detected. In this case, as shown in FIG. 2 and Table 2, the terminals 25 to 28 are controlled in the initial state → STEP1 → STEP2. Accordingly, in the initial state, the terminals 25, 26, 27, and 28 are at 0 V, 5 V, 0 V, and 5 V, respectively, so that the transistors 3, 4, 6, and 7 are off, and the transistors 5 and 8 are on. That is, the upper panel and the lower panel are electrically maintained at the GND level. In other words, at this point, the lower panel in the X direction is between the electrode terminals on both sides.
By connecting to the GND level from the state where a potential difference of 5 V is applied, the potential of the lower panel becomes the GND level. Next, at the stage of STEP1, the transistors 6, 7 are turned on. Therefore, a voltage is applied to the entire surface electrode in the Y direction. At this time, the lower panel for detecting the voltage is kept at the GND level. Next, at the stage of STEP2, the transistor 5
FF. That is, the voltage at the pressing point position in the Y direction from the terminal 29 is detected. Therefore, as shown in FIG. 2 and Table 2, by controlling the above steps, the voltage at the pressing point position in the Y direction can be detected. As described above, the charge accumulated in the floating capacitance of the panel on the detection side is released by the initial state and the operation of the first step, so that the voltage of the panel to which the voltage is applied can be accurately detected. . Further, in the above embodiment, a transistor is used as the switching means for driving the input device, but FIG. 4 shows an example of a drive circuit in the case where an analog switch is used instead of the transistor. 1 are the same as those in FIG. In the example of the driving circuit shown in FIG. 4, 33 to 36 are analog switches, and a voltage of, for example, 5 V is applied to the terminals 23 and 24. Terminals 25 to 28 are control terminals for controlling the analog switch. Hereinafter, the control method for detecting the X coordinate and the Y coordinate is exactly the same as in the above embodiment, and an accurate potential could be obtained at the time of the coordinate detection. [Effects of the Invention] According to the present invention, since the entire surface electrodes of both panels once maintain the GND level, there is no potential, and the voltage at the pressing point on the opposite side, which is the next step, is accurately detected. can do.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing an embodiment of the present invention. FIG. 2 is a view showing a flowchart for explaining a control method of the present embodiment. FIG. 3 is a diagram showing an example of a drive circuit used in a conventional input device. FIG. 4 is a view showing another embodiment of the present invention. FIG. 5 is a diagram showing a configuration of a conventional input device. 1 Upper panel 2 Lower panel 3-8 Transistors 9-20, 31, 32 Resistors 21, 22 Ceramic capacitors 23, 24 Terminals 25-28 Terminals (control input Terminals) 33 to 36 Analog switches 40 and 41 Full-surface electrodes 42 to 45 Electrode terminals

Claims (1)

(57) [Claims] A pair of panels with an entire surface electrode formed on the inner surface and electrode terminals provided at both ends are opposed to each other, and a predetermined voltage level and a GND level voltage are applied to the electrode terminals at both ends of one full surface electrode, respectively. A voltage applying means for forming a voltage distribution, and a switch means for opening and closing voltage application from the voltage applying means to the electrode terminal, and when the entire surface electrodes formed on the pair of panels come into contact with each other, the other In an input device for detecting a contact position from a voltage obtained by a full-surface electrode and the voltage distribution, a voltage is applied to a full-surface electrode of one panel, and the voltage is applied from an electrode terminal of the other panel through a contact point of the full-surface electrode. An input device, wherein the switch means is controlled so as to apply the voltage of the GND level to the entire surface electrodes of both panels before detecting the signal.