JPS616725A - Input position detector - Google Patents

Abstract

PURPOSE:To attain highly accurate and stable position detection with a simple constitution by forming constant current source circuits for fixing current flowing into respective detecting electrodes respectively. CONSTITUTION:A voltage sensitive resistor sheet of an information input device is constituted by applying a conductive layer 2 consisting of a metallic sheet to the upper surface of a voltage sensitive sheet 1 and laminating a plane resistor 3 to its lower surface and detecting electrodes 5a-5d are formed by connecting plural diodes to respective sides of the resistor 3 to detect the coordinates of a depressed position at the time of depression through an indicating pen or the like. Constant current sources 22a, 22b are connected respectively between the electrode 5a and the earth and between the electrode 5b and the earth to fix their outflow currents independently. In addition, operational amplifiers 21a, 21b are connected respectively between the electrode 5a and a terminal 101 to detect the potential difference between both the electrodes 5a, 5b and find out positional coordinates (X, Y). The potential of the electrode 5a is compared with a reference voltage 25 by a comparator 24, and when the former value is larger than the latter one, a Z signal is generated to make said X and Y is signals significant.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a device for detecting the coordinates of a position where pen pressure is applied during handwriting input or the like.

[Conventional technology]

2. Description of the Related Art Conventionally, there is a type of information input device that uses a pressure-sensitive resistor sheet to input information by utilizing a change in resistance at a pressed position. FIG. 2 shows a circuit H showing an example of its configuration. In the same figure.

A conductive layer 2 made of a metal sheet is disposed on the upper surface of the pressure sensitive sheet 1, and resistors 3 having uniform sheet resistance are laminated on the lower surface.5 These constitute an input surface. Figure 3 shows its laminated structure, and the Δ-
It is an arrow direction view of A cross section.

Now, a power source 4 for applying a driving voltage is connected between the conductive N2 on the input surface and the ground terminal.

A positive driving voltage is always applied to the conductive layer 2 due to this voltage ti,4. On the other hand, each side of the resistor 3 is provided with detection electrodes 5a, 5b, 5c, 5d each having a plurality of diodes arranged and connected at equal intervals. These detection electrodes 5a, 5b, 5c, 5d are of the type #4.
This is to uniformly flow the current flowing into the resistor 3 through the pressing position of the electric layer 2 and the pressure-sensitive sheet 1 from all sides of the resistor 3 by 11 degrees. Note that the diode prevents the current that has once flowed out from flowing back into the resistor 3. And each of the above-mentioned detection electrodes 5a.

5b, 5c, and 5d are detection resistors 6a, 6b, and 6, respectively.
c, 6d, and then commonly connected to opposing electrodes 5a, 5b and 5c, 5dfIf, and then connected to one constant current source 8 via switches 7a, 7b. This constant current source 8 is for making the output current of the power source 4 for applying the drive voltage constant. Also,
” 2. Each detection resistor 6a.

Operational amplifiers 9a, 9b for detecting the voltage drop are connected to the rear resistors 5b, 5c of 5b, 6c, 6d, and these operational amplifiers 9a.

The voltage value detected at 9b is sent to the sampling hold circuit (
S/H) 10a and 10b. Note that the fifth detection control circuit 11 is as follows.

The switches 7a and 7b are alternately closed, and the sampling and hold circuit 10a is closed accordingly.
, 10b perform a sampling and holding operation, thereby detecting the pressed position on the input surface separately in the X direction and the Y direction.

With such a configuration, when an arbitrary position on the input surface is pressed with an indicator pen or the like, the resistance value of the pressure-sensitive sheet 1 at this pressed position decreases, resulting in a substantially short-circuited state. here,
Detection control (assuming that the switch 7a is closed by the control signal issued from the I circuit 11, the output current of the power source 4 is changed to the conductive layer 2 by the pressing operation with the indicator pen)
．． It flows out from the detection electrodes 5a and 5b via the pressed position of the pressure-sensitive sort 1 and the resistor 3, and then flows out from the detection resistor 6.
a, flows to 6b. And these detection resistors 6a, 6
The voltage drop across the resistor 6b is detected by the operational amplifier 9b, and this detected value is applied to the sampling pole 1 circuit 101.
]. Note that since the sum of the currents flowing through each of the detection resistors 6a and ib is defined to a constant value by the constant current source 8, the ratio of the currents flowing through each of the detection resistors 6a and 6b is as follows.
This corresponds to the resistance ratio of the resistor 3 corresponding to the pressed position of the pressure sensitive sheet 1. Therefore, the operational amplifier 9b
The value of the voltage drop across the detection resistor 6b detected by and held by the sunblink hold circuit 10b directly indicates the coordinate 4 in the X direction of the pressed position on the input surface.

When the seat lever in the X direction at the pressed position is detected in this way, a control signal is output from the detection control circuit 11, and the switch 7b is closed instead of the switch 7a.

As a result, the output current of the power source 4 is now reduced to the detection electrodes 5c and 5.
d flows to the detection resistors 6c and 6d.

The voltage drop across the detection resistor 6c is detected by the operational amplifier 9a as information indicating the Y-direction coordinate of the pressed position. In this way, the coordinates of the pressed position in the X and Y directions are detected.

In this way, with this configuration, it is relatively easy to detect the pressed position on the pressure-sensitive sheet, that is, the input information, compared to other devices such as electrostatic capacitive modeling. can do.

[Problem that the invention attempts to solve]

However, in the conventional device, the X-direction and Y-direction coordinates of the five pressed positions are alternately detected by using one constant current source 8 and switching the switches 7a and 7b. Therefore, information switches 7a, 7b and a circuit for switching control thereof are required, as well as sampling and holding circuits lQa, 10b for holding each detected value in the X direction and Y direction. Therefore, the two-circuit configuration becomes complicated, which is not practical. Also, since detection is performed while switching.

Unstable elements are likely to be included in the detected values, making it difficult to improve detection accuracy.

[Means for solving problems]

The present invention eliminates these drawbacks, can be realized with a simple configuration, and enables accurate and highly stable position detection.

Detection electrodes are provided on two adjacent sides of the resistor that constitutes the input surface, and a constant current source circuit is provided to make the current flowing through the valley detection electrode constant for each electrode, so that each coordinate in the X and Y directions can be adjusted. Detection is possible without switching control.

Embodiments will be described below with reference to two drawings.

〔Example〕

FIG. 1 shows a circuit configuration in an embodiment of the present invention.

Components that are the same as those in FIG. 2 are given the same reference numerals and detailed explanations will be omitted.

In FIG. 1, constant current sources 22'a, 22b are connected between each detection electrode 5a, 5d and the ground terminal, and each detection electrode 5a is connected by these constant current sources 22'a, 22b.

The currents flowing out from 5d are each made constant independently. The constant current source 22a connects the source and gate of the field effect transistor 50 with a resistor R5, and outputs a constant current I when a positive voltage is applied to the drain by input. 22b also has a similar configuration. Further, the detection electrode 5a and the terminal 101 and
An operational amplifier 2 is connected between the detection electrode 5d and the terminal 101.
]a and 21b are connected, detect the potential difference between the detection electrode 5a and the terminal 101, and between the detection electrode 5d and the terminal 101, and input these potential differences (press) to the position coordinates (X, Y) of the point. Output as . moreover.

The comparison circuit 24 compares the potential appearing on the detection electrode 5a with the output voltage E of the reference voltage a25, and when the potential is equal to or higher than this reference voltage, the comparison circuit 24 generates an "H" level Z signal.

When the Z signal is at the "I" level, it is determined that there is an input (press), and the X obtained at that time.

The Y signal is considered significant.

FIG. 4 is an equivalent circuit for explaining the operation of the device shown in FIG. When an input is performed, the conductive layer is brought into electrical contact with the resistor 3 at the input position via the pressure-sensitive sheet 1 due to the pen pressure. In Fig. 4.

When a power source E for applying a drive voltage is applied to the input position indicated by the reference numeral 100, the detection electrode 5a and the input position 100
Similarly, a constant current I is applied to the equivalent resistance R2 between the detection electrode 5d and the input position 100.
2 flows. Since the resistor 3 has a uniform resistance value, R+
is proportional to the distance between the detection electrode 5a and the input position 100,
R2 is proportional to the distance between the detection electrode 5d and the input position 100.

The values of R1 and R2 are constant current Il between both resistors.

(2) Voltage rise RII+ due to 2 can be obtained by measuring RzT2. Therefore, by measuring R+I+, R2I2, X of the input position 100.

The Y coordinate is obtained.

R3 is an equivalent resistance between the input position 100 and the terminal 101 of the resistor 3, and the subtraction circuit consisting of two operational amplifiers 21a etc. is connected between the input position 100 and the output terminal 104 of the detection electrode 5a via the resistor R3. Detects the potential difference between If the subtraction circuit is constructed from elements with high input impedance, such as operational amplifiers, the influence of R3 can be ignored. In addition, the detection electrode 5a
Since the current flowing through the diode inside is constant, it can be known in advance and corrected. Similarly, the subtraction circuit consisting of the operational amplifier 21b has a resistance l? 3, the potential difference between the input position 100 and the output terminal 103 of the detection electrode 5b is detected.

Note that the input surface used in the device of the present invention is not limited to the configuration shown in FIG. 3, and may be constructed using a transparent material such as an ITO transparent film or Nesa glass.

It can also be used in combination with a CRT or other flat display.

In addition, a pressure-sensitive rubber band or a spacer that maintains a constant interval may be used as the pressure-sensitive sheet, and a flexible conductive layer or a structure in which tension is applied to the resistor and the two electrically contact each other only when pressure is applied may be used. You can also do it.

[Effects of the Invention] - As explained above, according to the present invention, there is no need to switch the constant current source 8, and the number of detection electrodes having a plurality of diodes can be reduced from four to two. , it has advantages such as not requiring a sampling and holding circuit.

[Brief explanation of the drawing]

Fig. 1 is an embodiment of the device of the present invention. Fig. 2 is a configuration diagram of a conventional input position detection device. Fig. 3 is a cross-sectional view of the input surface as viewed from the arrow. Fig. 4 explains the embodiment shown in Fig. 1. This is an equivalent circuit for 1... Pressure sensitive sheet 2... Conductive layer 3... Resistor 4... Power source for applying driving voltage 5a, 5b,
5c. 5 d, Detection electrodes 6a, 6b, 5c,
6d...Detection resistor 7a, 7b...Switch 8.22a. 22 b...constant current source 9a, 9b, 2] a, 2
1b...Operation amplifier 10'a, 10b...Sampling bold circuit 11...Detection control circuit
24... Comparison circuit 25... Reference power supply 5o.
...Field effect transistor R1...Resistance 10
1,103.104...Terminal 100...Input position Patent applicant Mori, patent attorney representing Nippon Telegraph and Telephone Public Corporation 1) Hiroshi Figure 1

Claims (2)

[Claims] (1) An input surface in which a conductive layer and a resistor are arranged facing each other, and the conductor and the resistor are electrically contacted at a position where pressure is applied between the two; Detection electrodes provided on two adjacent sides, a drive voltage application circuit that applies a drive voltage between these detection electrodes and the conductor, and a current that flows through each of the detection electrodes due to the application of the drive voltage. An input position detection device comprising: a constant current source circuit that makes the current constant for each electrode; and an arithmetic circuit that detects a potential difference between the voltage appearing at each of the detection electrodes and the resistor. (2) In the input position detection device according to claim (1), when the magnitude of the potential appearing on the detection electrode reaches a preset value, the detection result obtained by the arithmetic circuit is An input position detection device comprising a detection control circuit that determines a true input position.