JPS605325A - Finger-touching type coordinate input device - Google Patents

Abstract

PURPOSE:To cancel the stray capacity and improve the sensitivity of a finger- touching type coordinate input device, by adding LC parallel resonators which resonate when no finger touches the finger-touching type coordinate input panel of the device. CONSTITUTION:When either one of X- and Y-directions is selected under a time shared condition by means of analog switches 8-1, 8-2, 9-1, and 9-2, it can be known from the output of an output terminal 13 that which position in this direction is touched with a finger. Since stray capacities exist in the analog switches and wiring and, therefore, the sensitivity of a touch sensor is lowered, LC parallel resonators 6 and 7 which resonate together with the above mentioned floating capacities when no finger touches a finger-touching type coordinate input panel 4 are provided in this invention. Because of the parallel resonators 6 and 7 which resonate to the frequency of a sine wave oscillator 1 including the stray capacities, decline in the sensitivity resulting from the existence of a stray capacity can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The present invention relates to a coordinate input device, and more particularly to a finger-touch type coordinate input device that determines the coordinates of a finger-touch point by detecting a capacitance that changes due to a finger touch.

(2) Background of technology With the recent development of electronic engineering, the application of electronic engineering in all fields is becoming popular. One of its applications is a coordinate input device. There are various input methods for coordinate input devices, but there is a device that uses a coordinate indicating medium to indicate coordinates on a certain board with an operator's finger, and electrically detects the coordinates using a detection circuit. Further, more accurate determination can be made using such a method. There is an even greater desire for something with better sensitivity.

(3) Prior Art and Problems Conventionally, there is a coordinate input device that applies a voltage to both ends of a resistive film and detects a coordinate point from the ratio of currents flowing from both ends of the resistive film to a designated point on the resistive film. In this device, the resistive film is generally covered with a dielectric layer to protect the resistive film, and the power source must be an AC power source. This is because, as described above, the dielectric layer covering the resistive film is an insulator that does not conduct direct current. however.

Since an AC power source is used as a power source, stray capacitance hanging from a transparent resistance layer on a substrate, a finger-touch coordinate input panel that covers the resistance layer with a transparent insulating layer, and a detection circuit becomes a problem. This is because current leaks through stray capacitance.

Therefore, in conventional devices, this stray capacitance is equal to or greater than the human body's ground capacitance, so when finger-touch type coordinate detection is performed, there is a problem that sufficient detection sensitivity, that is, resolution cannot be obtained.

(4) Object of the Invention The present invention is intended to solve the above-mentioned problems, and its object is to provide a finger-touch type coordinate input device with high resolution.

(5) Structure of the Invention The present invention is characterized in that one end is connected to at least one of both ends or four ends of a finger-touch type coordinate entry cover panel in which a resistance layer disposed on a substrate is covered with an insulating layer. In the coordinate input device, the current detecting means comprises a switch means, the other end of the switch means is connected to one end and the other end is connected to a power source, and an arithmetic means for receiving input from the current detecting means. The finger-touch coordinate input device is characterized in that an element for canceling stray capacitance between the current detection means, the switch means and a connecting line is provided at a connection point of the switch means.

(6) Examples of the invention The present invention will be described in detail below using the drawings.

FIG. 1 is a block diagram showing the principle of the finger touch type coordinate input device of the present invention. A sine wave oscillator whose one end is grounded; a current detector 2 and a current detector 3 connected to the other end;
It consists of a finger-touch coordinate input cover panel 4 to which the other end of each current detector is connected. Here, the touching finger 5 is indicated by human body-to-ground capacitance 5'.

When a finger is touched, the current is connected to two paths, one is from the sine oscillator 1 via the current detector 2, enters from the a end of the finger touch type coordinate input panel 4, and is connected to the human body ground capacitance from the finger touch point (x, y). 5' to the earth. Let this flowing current value be I+. Similarly, the other wave enters from the b end of the finger-touch coordinate input panel 4 from the sine wave oscillator 1 via the current detector 3 and flows from the finger touch point (X, Y> to the ground via the human body-to-ground space M5'. The value of this flowing current is I2.Since the finger-touch type coordinate input cover panel 4 is a resistance layer, it can be considered as a resistance.
Since the voltages applied to the ends are equal, the current flowing between ax and bx, that is, the ratio of current (1) to current (2), is equal to the inverse ratio of the resistance value between ax and the resistance value between bx. Since the resistance layer of the finger touch type coordinate panel 4 is uniform, the resistance value between ax and bx
The resistance values between 5- and 5- are proportional to the distances between ax and bx, respectively. Where the finger touch point X is located between ab and the finger touch type coordinate panel 4 can be calculated using equation (1). Here, i indicates the distance between ab and ab.

ax+bx T +→-■2 Equation (1) shows that the finger touch point X is a on the finger touch coordinate panel 4.
It shows what percentage position it is in when viewed from end a between b. For example, when the value of equation (1) is 0.3, it indicates that the finger touch point X is at a position 3/10 from end a to ab between ab and ab. FIG. 2 is a plan view and a side view, respectively, showing the structure of the finger touch type coordinate input cover panel of the present invention. FIG. 2 <a> shows the finger-touch type coordinate input cover panel viewed from directly above, and FIG. 2(b) shows the finger touch type coordinate input cover panel viewed from the side. A resistive layer 42 is provided on a substrate 41, and an insulating film 43 is coated on the resistive layer 42 to protect the resistive layer 42.

FIG. 3 is a block diagram of the finger-touch type coordinate input device of the present invention. One end of the sine wave oscillator is grounded, and the other end is connected to one end of the current detector 2.3. The other end of the current detector 2 is connected to the first terminal of the adder 11, and the other end of the inductor L1 and the capacitor CI are connected to the parallel resonator 6 and the analog switch group 8-. 1
．． 9-2. The other end of the current detector 3 is the second input of the adder 11, the other end of the parallel resonator 7 of the increment L2 and the capacitor C2 whose one end is grounded, one end of the analog switch group 8-2.9-1, The output of adder 11 is connected to the dividenend input of divider 12, which is added to the divisor input. Analog switch group B-1゜9-1
are the resistor portions 12 at the left and right ends of the cover panel 4 containing the 1,000-meter coordinates. The analog switch groups 8-2 and 9-2 are connected to resistor portions at the lower and upper ends of the finger-touch coordinate input cover panel 4, respectively. Analog switch group 13-1.8-2.
9-1 and 9-2 are each composed of a plurality of analog switches, and each switch has the above-mentioned control function.
It is discretely connected to the resistor part of the inch type coordinate system.

Here, the touching finger is indicated by human body-to-ground capacitance 5'.

The circuit in FIG. 3 shows a circuit configuration based on the principle explained using FIG. 1. Analog switch 8-1.
8-2. Analog switches 9-1 and 9-2 select either the X direction or the Y direction in a time-sharing manner. When one of them is selected, the position where the finger in that direction touches the finger touch coordinate input panel 4, that is, the coordinates in the selected direction can be known from the output from the output terminal 13. Current detector 2
Current value flowing through ■1 and current value flowing through current detector 3 ■2
The output of is input to adder 11, and from adder 1, TI+
12 is output. The output of I + 12 is input as a divisor to the divider 12, the output of the current detector 3 is input as the dividend to the divider 12, and the output of the divider 12 is +2.
/(T++Iz) is obtained. Therefore, as described above, it is possible to know the position touched by the finger on the finger touch coordinate entry panel. The embodiment of the present invention shown in FIG.
selects the X direction and Y direction, and the X coordinate,
You can know the coordinates.

In the circuit described above, there is stray capacitance in analog switches, wiring, etc., and this stray capacitance has a value equal to or greater than the human body's ground capacitance. In order to cancel this stray capacitance, an LC parallel resonator 6. which resonates together with the above-mentioned stray capacitance when the finger is not touching the coordinate input cover panel 4. LC parallel resonator 7 with analog switch ik1.9
-2 and current detector 2, and analog switch 8-2
9-1 and the current detector 3, respectively.

In other words, since the r, C parallel resonator 6゜7 including the stray capacitance resonates at the frequency of the sine wave oscillator 1, the wire where the stray capacitance occurs has a high impedance with respect to ground, and the current flowing due to the stray capacitance becomes almost zero. By providing this LC parallel resonator 6.7, the above-mentioned current error is reduced, so that the resolution of the finger touch type coordinate input device is improved.

(7) Effects of the Invention In the finger-touch type coordinate human-powered device of the present invention, by providing an LC parallel resonator that resonates when the finger does not touch the finger-touch type coordinate input panel, the effects of alternating current 9- Since the impedance increases rapidly at the resonance point, stray capacitance can be canceled out, which has the effect of increasing detection sensitivity and resolution. In other words, there is an effect of improving the SN value of the current component to the coordinate indicating medium.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the principle of the finger-touch type coordinate input device of the present invention, FIG. The figure is a configuration diagram of the finger touch type coordinate input device of the present invention. 1... Sine wave oscillator, 2.3... Current detector,
4...Finger Taso 1000 type coordinate input cabanel, 5...Human body ground capacity. 6.7...LC parallel resonator, 8-1. ．． 8-2.9
-1.9-2...Analog switch group. 11... Adder, 12... Divider. 13... Coordinate output terminal, 41... Board. 42... Resistance layer, 43... Insulating layer 10- Figure 1 Figure 2 Figure 3

Claims (4)

[Claims] (1) Switch means, one end of which is discretely connected to both ends or at least one of the four ends of a finger-touch coordinate input cover panel in which a resistive layer placed on a substrate is covered with an insulating layer;
In a coordinate input device comprising a current detecting means to which the other end of the switch means is connected to one end and a calculation means for receiving input from the current detecting means, a connection point between the current detecting means and the switch means; A finger touch coordinate input device, further comprising an element for canceling the stray capacitance of the current detection means, the switch means, and the connection line. (2) The finger-touch type coordinate input device according to claim 1, wherein the canceling element is a resonant circuit composed of capacitance and inductance. (3) The switch means has a control means, and the control means turns on and off a switch in the X-axis or Y-axis direction in a time-sharing manner.
The finger-touch type coordinate input device described in Section 1. (4) The finger touch type coordinate input device according to claim 1, wherein the resistive layer and the insulating layer are transparent.