JPH11353103A - Tablet input device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To prevent a decrease in measurement accuracy due to a temperature variation of a delay time of a waveform shaping circuit. According to the present invention, a test circuit section for detecting a variation amount of a propagation delay time of a waveform shaping circuit, and a switch for switching between a detection output of an input pen and a test signal output from the test circuit section. Means 17 are provided. The test circuit section 16 inputs the test signal S2 to the waveform shaping circuit via the switch means 17 at the time of initial setting of the apparatus (t = t ₀ ) and at a predetermined time (t = t _i ). And the output of the waveform shaping circuit,
(T ₀ ) and τ (t _i ) are measured, and a variation Δi = τ (t _i ) −τ (t ₀ ) of the delay time is calculated from the measured values and supplied to the X and Y position calculation means. I do. The X, Y position calculation means corrects the X, Y coordinate position of the input pen using the variation Δi.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatically-coupled tablet input device for inputting a pen to a computer or the like.

[0002]

2. Description of the Related Art A tablet input device sequentially detects the position of an input pen (pen-type detection sensor) that moves on a tablet input plate, and gives the position data to a computer or the like. The user can know the figures and characters drawn by the input pen, display the figures and characters, and use them to change the figures displayed on the screen.

[0005] A conventional electrostatically-coupled tablet input device 1 shown in FIG.
It comprises a Y electrode drive circuit 4, a pen-type detection sensor (hereinafter referred to as an input pen) 5, a waveform shaping circuit 6, an X position calculation circuit 7, a Y position calculation circuit 8, and the like. Tablet input board 2
, X electrodes X1 to XN are arranged in parallel at equal intervals in the X direction, and Y electrodes Y1 to YM are similarly arranged in parallel at equal intervals in the Y direction. As shown in FIG. 7, the X electrode Xi and the Y electrode Yi are formed on the insulating substrates 13 and 14, respectively, by a method such as printing or vapor deposition, and their electrode patterns are orthogonal to each other with the insulating plate 15 interposed therebetween so as not to contact each other. Are arranged as follows.
In particular, when a screen input tablet is superimposed on a display screen such as an LCD or CRT, glass is used as the insulating substrates 13 and 14, a transparent adhesive sheet is used as the insulating substrate 15, and the insulating substrates 13 and 14 are made of ITO. It is formed by depositing a transparent film and etching it so as to leave an electrode pattern portion.

In order to measure the position of the input pen 5 in the X direction, a voltage is sequentially applied to the X electrodes X1 to XN at fixed time intervals. Since a capacitance is formed between the input pen 5 and the X electrode, a voltage appears on the input pen 5 when a voltage is applied to an electrode close to the input pen 5. This voltage takes a maximum value when a voltage is applied to the electrode closest to the input pen 5 (FIG. 6). The position of the input pen 5 in the X direction is detected from the relationship between the temporal change of the voltage obtained by the input pen 5 and the voltage application time to each electrode. The same applies to the position detection in the Y direction.

The waveform shaping circuit 6 includes an amplifier 6a, a filter 6
b and a circuit for shaping the voltage waveform detected by the input pen 5 into a waveform suitable for position measurement. The oscillating circuit 9 supplies a synchronizing signal of the frequency Fx to the X electrode driving circuit 3 and the X position calculating circuit 7, and the oscillating circuit 10 supplies a synchronizing signal of the frequency Fy to the Y electrode driving circuit 4 and the Y position calculating circuit 8. You.

[0006]

In the tablet input device, a detection output of the input pen is input to an X position calculation circuit 7 and a Y position calculation circuit 8 through a waveform shaping circuit 6 including an amplifier 6a, a filter circuit 6b and the like. You. With this circuit configuration, the temperature inside the device at the time of initial setting (initialization) of the tablet input device may be affected by the heat generated by the components used in the waveform shaping circuit 6 due to the lapse of time after the device has been operated, or the ambient temperature. Due to the change, the temperature of the component changes, and the output signal waveform of the waveform shaping circuit 6 is temporally shifted due to the temperature characteristic of the component used. Then, there is a problem that it differs from that after a lapse of time.

An object of the present invention is to prevent fluctuations in the X and Y position detection outputs due to the temperature characteristics of the delay time of the waveform shaping circuit 6.

[0008]

(1) The tablet according to claim 1
Input input device, the fluctuation of the propagation delay time of the waveform shaping circuit
Test circuit for detecting the amount, input pen detection output and test
Switch to switch between test signal output from circuit section
Steps are provided. The test circuit section is used when
(T = t₀) And a predetermined time (t = t_i)
Test signal to the waveform shaping circuit via the switch means
And comparing the input signal with the output of the waveform shaping circuit.
Propagation delay time τ (t₀), Τ (t_i) And measure them
From the measured value of Δi = τ (t_i)-
τ (t ₀) Is calculated and supplied to the X, Y position calculating means.
The X, Y position calculation means uses the variation Δi to
Is corrected.

(2) According to a second aspect of the present invention, the test circuit section comprises:
The calculation of the variation Δi of the propagation delay time of the waveform shaping circuit is periodically performed.

[0010]

FIG. 1 shows an embodiment of the present invention, and FIG.
The same reference numerals are given to the portions corresponding to and the description will be omitted. In the present invention, the test circuit unit 16 for newly detecting the amount of change in the propagation delay time of the waveform shaping circuit 6 and the input pen 5
And a switch circuit 17 for switching between the detection output S1 of FIG.

At the time of initial setting (at the time of initialization) and at a regular time, the output of the input pen 5 and the test signal S2 are switched by the switching signal S3 for testing and input to the waveform shaping circuit 6. The test circuit unit 12 includes a test signal generation unit 12a, a delay time calculation unit 12b, and the like. The difference between the time when the test signal S2 is output from the test signal generation unit 12a and the time when the signal S4 returns through the waveform shaping circuit 6 is detected. Measure τ (t) (FIG. 2). This τ (t) is the propagation delay time of the waveform shaping circuit 6 at the time t depending on the temperature state. The delay time calculation unit 12b calculates a change in the delay time of the waveform shaping circuit due to the temperature change from τ (t).

Normally, the detection signal S1 from the input pen 5 is switched and selected and input to the waveform shaping circuit 6 to detect the position of the input pen 5. Delay time τ of waveform shaping circuit 6 at initialization
Since the delay time τ (t _i ) after the change of (t ₀ ) and the ambient temperature or the temperature of the used component may change, the test circuit unit 12 periodically switches the switch circuit 13 to change the test signal S2. Is input to the waveform shaping circuit 6, and a change in the delay time is calculated from the delay time τ (t _i ) of the circuit 6 at that time, and the X position calculation circuit 7 and the Y position calculation circuit 8 use the above change. To calculate the position of the input pen 5.

For example, it is assumed that the delay time is τ (t ₀ ) as shown in FIG. 3 when the power is turned on (t = t ₀ ). It is assumed that the tablet device has been calibrated at that time. Thereafter, the temperature of the ambient temperature and the components used are changed, when sending the test signal S2 again t = t _1, the circuit delay time tau (t
₁ ) Suppose it was. In that case, the delay time calculation unit 12b
Calculates the change amount of the delay time Δ ₁ = (t ₁ ) −τ (t ₀ ) and gives information to the X position calculation circuit 7 and the Y position calculation circuit 8. The X position calculation circuit 7 and the Y position calculation circuit 8
By correcting the variation delta ₁ of the delay time from the time corresponding to the coordinate position of the obtained input pen by the detection signal S1 from the input pen 5, to calculate the position data of high accuracy. FIG. 4 collectively shows the operation flow of the above-described tablet device.

[0014]

According to the present invention, the switch means 17 and the test circuit section 16 as described above are provided, and the influence of the variation in the delay time of the waveform shaping circuit is corrected by the X and Y position calculation circuits 7 and 8, so that the surroundings are corrected. Even when the temperature or the temperature of the component used changes, the correct X, Y coordinate position can always be detected.

[Brief description of the drawings]

FIG. 1 is a block diagram of the present invention.

FIG. 2 is a waveform chart showing a relationship between a test signal S2 and a circuit delay signal S4 in FIG.

FIG. 3 is a circuit delay signal S4 for the test signal S2 of FIG. 1;
FIG. 7 is a waveform chart showing an example of the change of FIG.

FIG. 4 is an operation flowchart of FIG. 1;

FIG. 5 is a block diagram of a conventional tablet input device.

FIG. 6 is an operation waveform diagram of a main part of FIG. 5;

FIG. 7 is an exploded perspective view of the tablet input plate 2 of FIG.

Claims (2)

[Claims] 1. A method in which a plurality of X, Y electrodes are laid at regular intervals.
A tablet input plate, means for applying a scan pulse to each of the X and Y electrodes, and
An input pen (pen-type detection) that detects the voltage induced at a desired point
Output sensor), means for shaping the waveform of the input pen, and the table of the input pen from the output of the waveform shaping means.
X, Y position calculating means for calculating the coordinate position on the input board
A tablet input device comprising: a detection unit for detecting a variation amount of a propagation delay time of the waveform shaping circuit;
Test circuit unit, the detection output of the input pen and the output from the test circuit unit
Switch means for switching between the test signal and the test signal.₀)When,
At a predetermined time (t = t_iIn the above, the test signal is
Input to the waveform shaping circuit via a switch means,
Compare the input signal with the output of the waveform shaping circuit to determine the propagation delay
Time τ (t₀), Τ (t_i) And measure them
From the variation of the propagation delay time Δi = τ (t _i) −τ
(T₀) Is calculated and supplied to the X, Y position calculating means.
The X, Y position calculating means uses the variation Δi to calculate
X and Y coordinate positions of the input pen are corrected.
Tablet input device. 2. The test circuit according to claim 1, wherein:
A tablet input device for periodically calculating a variation Δi in a propagation delay time of the waveform shaping circuit.