JPH0895701A - Combination touch panel and transparent digitizer - Google Patents

Abstract

PURPOSE: To obtain a touch panel and digitizer function which has high transmissivity and high stability at low cost by using a transparent tablet for the digitizer even as an input medium for a touch panel. CONSTITUTION: Respective X- and Y-axial electrode wires (X1 -Xn and Y1 -Ym ) are connected independently to the respective terminals of analog multiplexers 3 and 4. The multiplexers 3 and 4 are connected to the port of a control part 9 and optional analog switches can optionally be set. After the power source is turned on, this device counts the frequency that an AC pen 2 transmits to detect the state of the pen 2. When the pen 2 is nearby the tablet 1, processing is performed as the digitizer. When the pen 2 is not on the tablet 1, the operation is repeated as the touch panel. Further, when the pen 2 is nearby the tablet 1, this device functions as the digitizer, so even when the hand gripping the pen 2 touches the touch panel, no wrong data is sent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coordinate detecting device which detects the position touched on a tablet with a finger or a pen by changing the precision according to the purpose and outputs each coordinate.

[0002]

2. Description of the Related Art When a transparent digitizer is placed on a liquid crystal screen and considered as an input interface, high resolution is required for inputting image data such as character input and details such as point designation, and a coordinate indicator such as a pen. Is required. However, the coordinate input device often does not require such high resolution. For example, when confirming the contents displayed on the screen from the user,
A resolution such as a touch panel that requires a coordinate signal as a region is sufficient. In addition, it is more direct to specify without using a pen or the like, which is a more user-friendly input method.

[0003]

As a solution to this problem, a method of combining a digitizer and a touch panel by providing a touch panel on the upper part of the digitizer unit can be considered. However, the transmittance of the conventional touch panel deteriorates due to the resistance sheet. There is a method such as applying the same voltage on a transparent film with uniform resistivity on the glass plate surface, measuring the current flowing when the human body touches due to electrostatic capacitance at four points on the edge of the panel and detecting the position. However, since the signal was shielded by the resistive film, it was impossible to combine the resistive touch panel with the digitizer. Similarly, there is a method in which a pulse is applied to one electrode of a tablet in which a lattice-shaped resistance film is arranged in the X / Y directions and the position of the finger is detected by a signal at the end of the electrode line. When scanning the side electrode line, the upper electrode shields the signal and the signal S / N
The ratio was poor and unstable. Other touch panels that can be combined are optical and ultrasonic touch panels, but they have become expensive in price.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the conventional problems, and includes a tablet having a plurality of electrode lines arranged along the X and Y electrode axes, an AC signal generator, and An analog multiplexer that connects an AC signal generator to the plurality of X-direction electrode lines, an analog multiplexer that sequentially selects the plurality of Y-direction electrode lines, and an operational amplifier having an input impedance of 1 KΩ or less that applies the output of each multiplexer. A circuit for detecting the output of this amplifier, an AD converter for A / D converting the output signal from the detection, and a control unit for reading this signal.

[0005]

When the pen operates as a transparent digitizer, the signal oscillated by the pen is sequentially input to every two adjacent electrode lines, and the position of the pen is determined based on the signals differentially amplified and input from the two electrode lines. To detect. When the pen is near the electrode wire, the difference between the signals input from the two electrode wires is large.
A large signal can be obtained near the corresponding electrode wire. Using this principle, the coordinates can be obtained in the X and Y directions.
When operating as a touch panel, one electrode on one side is oscillated and a signal is sequentially input on the other electrode. When a finger or the like that is pseudo-grounded exists near the intersection of the electrode lines, the electric signal decreases and a signal lower than that when other electrode line signals are input is obtained.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the accompanying drawings. First, a circuit diagram used in the present invention will be described with reference to the electrical block diagram of FIG. X and Y axis electrode wires (X1 to X
n, Y1 to Ym) are independently connected to the respective terminals of the analog multiplexers 3 and 4. Each electrode wire (X1
Xn, Y1 to Ym) and multiplexers 3 and 4 are 1 KΩ
Is connected to GND. Each of the analog multiplexers 3 and 4 is connected to the port of the control unit 9 so that any analog switch can be independently set.

The analog multiplexers 3 and 4 are used to select an arbitrary electrode line, and all adjacent electrode lines (X1 to Xn, Y1 to Ym) are used as a circuit connecting method.
Not only can you select two at the same time,
Independently, even one electrode line can be selected. (See FIGS. 2 and 3) A circuit 10 that oscillates at the same frequency as the AC signal pen 2 is connected to the touch panel / digitizer switching analog multiplexer 5. The touch panel / digitizer switching analog multiplexer 5 is connected to only one of the analog multiplexers 3 and 4 (X side or Y side) connected to each electrode line. The touch panel / digitizer switching analog multiplexer 5 is controlled by the control unit 9 to oscillate circuit 1.
Applying a signal from 0 to the electrode line via one analog multiplexer 3 and the AC picked up by the electrode line during digitizer operation
The input of the signal from the signal pen 2 is switched.

The analog multiplexer 5 is connected to the differential amplifier circuit 6 and amplifies the difference between the two input signals to improve the S / N ratio. The output signal of the differential amplifier circuit 6 allows the bandpass filter 7 to pass only the frequency in the required band and removes the unnecessary signal. In this case, it is set to the frequency of the AC signal pen 2. The signal that has passed through the bandpass filter is shaped into a direct current level by AM detection. Next, the DC signal is converted into a digital value by the A / D converter 8 and taken in by the control unit 9.

Next, selection of digitizer operation and touch panel operation for the entire apparatus will be described. After the power is turned on, this device counts the frequency that AC pen 2 is transmitting,
The state of the AC pen 2 is detected. And (1) AC pen 2
Is near the tablet 1, it is processed as a digitizer. (2) If the AC pen 2 is not on the tablet 1, the operation as the touch panel is repeated. (3) When the AC pen 2 is in the vicinity of the tablet 1, it functions as a digitizer, so that erroneous data is not transmitted even when the hand holding the AC pen 2 touches the touch panel.

Next, an outline of the digitizer operation will be described. Since the method of detecting the position is substantially the same in the X-axis direction and the Y-axis direction, only the X-axis direction will be described. Touch panel / digitizer switching analog multiplexer 5,
The signals from the electrode lines (X1 to Xn, Y1 to Ym) of the tablet 1 are switched to the analog multiplexers 3 and 4, respectively, and the two signal lines from the analog multiplexers 3 and 4 are connected to the differential amplifier 6. To switch. X1, X2, X3, ..., Xp, Xp + 1, ...
If Xn, electrode lines X1 and X2, X2 and X3, ..., Xp-
The analog multiplexer 3 is selected so that signals of two electrode lines can be sequentially input simultaneously with 1 and Xp, Xp and Xp + 1, ..., Xn.

The signal input from the analog multiplexer 3 is canceled by the differential amplifier circuit in common mode noise to improve the S / N ratio. Here, when the AC pen 2 exists near the electrode wire, a signal difference is generated depending on the distance between the tip of the AC pen 2 and the electrode wire (X1 to Xn). Therefore, the position is detected using this difference. . AC pen 2
Exists near the electrode line Xp, the electrode lines Xp-1 and Xp,
When Xp and Xp + 1, Xp-1 and Xp-2, or Xp + 1 and Xp + 2 are simultaneously decoded, the control unit 9 calculates the position of the pen from the three signal level ratios detected.

Next, an outline of the touch panel operation will be shown. The analog multiplexer 5 for switching the touch panel / digitizer uses the signal from the oscillation circuit 10 for each electrode line (X1 to X1).
n) so that it can be transmitted sequentially. Oscillator circuit 10
The signal from sends the signal to the connected electrode line.
A case where a signal is transmitted from the Y-axis side electrode wires (Y1 to Ym) and a signal is output from the X-axis side electrodes (X1 to Xn) will be described.
While oscillating the signal on one electrode line, the signal on the other electrode line is transmitted from the analog multiplexer 3 to X1, X2, ...
Input from Xp, Xp + 1, ..., Xn and one electrode line from the X-side electrode line. When a signal is transmitted from the electrode wire Yi, X
After inputting all the electrode lines on the side, the transmitting electrode line is changed to the next electrode line Yi + 1.
Similarly, the input side electrode wires are sequentially selected from the first one. This process is repeated for all the output side electrode lines. The input signal is amplified by a circuit similar to that in the digitizer operation, and the signal level is taken in by the control unit 9 after A / D conversion.

When there is no operator's finger or the like on the tablet 1, a constant signal is transmitted by electrostatic coupling because the distance between the electrode line to which the signal is applied and the input electrode line is small, but the signal is applied. If there is a finger or the like that is pseudo-grounded at the intersection of the input electrode line and the input electrode line, the cross capacitance between both electrode lines is reduced by passing through the human body and the transmission signal level is also lowered. In the actual measurement example of the prototype, the signal attenuation rate was 20 to 25%. From this, it is possible to detect the position of the finger or the like that is pseudo grounded from the applied electrode wire number and the input electrode wire number having a low signal level.

The control unit 9 scans the entire surface of the tablet 1,
The center point is calculated from the area where the voltage level is low. Coordinates are transmitted for the calculated value with the designated resolution as the touch position.

[0015]

EFFECTS OF THE INVENTION Since the present invention is configured as described above, a transparent tablet for a digitizer is also used as an input medium of the touch panel to enable a touch panel with a high transmittance and a high stability, and a digitizer function. It can be realized at low cost. In addition, because the electrode wire spacing is arranged so as to satisfy the digitizer function, when a signal is input as a touch panel, changes in the signal can be detected at many electrode wire intersections, so the center of gravity of the signal change position can be detected by a program. However, the position can be detected at any resolution. This enables a touch panel function with an electrode line pattern suitable for a transparent digitizer.

[Brief description of drawings]

FIG. 1 is an electrical block diagram of the entire apparatus.

FIG. 2 Analog multiplexer switching circuit diagram

FIG. 3 is a circuit diagram of an analog multiplexer and an electrode wire.

[Explanation of symbols]

1 Tablet 2 AC Signal Pen 3 Analog Multiplexer 4 Analog Multiplexer 5 Touch Panel / Digitizer Switching Analog Multiplexer 6 Differential Amplifier 7 Bandpass Filter 8 Analog / Digital Converter 9 Controller 10 Oscillation Circuit

Claims (2)

[Claims] 1. A tablet having a plurality of electrode lines arranged along the X and Y coordinate axes, respective analog multiplexers coupled to the electrode lines of at least one coordinate axis of the tablet, and via the analog multiplexer. A transparent digitizer also used as a touch panel, which sequentially applies an oscillation signal to the electrode lines and detects the position where the tablet is touched with a finger. 2. A tablet having a plurality of electrode lines arranged along the X and Y coordinate axes, and a pen for transmitting a balanced AC signal from two conductors of a pen tip portion capacitively coupled to the electrode lines of the tablet. In the digitizer, the analog multiplexers coupled to the electrode lines of the respective coordinate axes of the tablet are alternately selected to select two electrode lines each, and capacitively coupled to the two conductors at the tip of the pen, thereby the digitizer A transparent digitizer that doubles as a touch panel and is characterized by detecting the position touched with a pen as a digitizer.