JPH0461371B2 - - Google Patents

Description

[Detailed Description of the Invention] [Summary] Two opposing sides of a planar resistor each have a phase.
a first drive mode that applies drive signals different by 90°;
The coordinates of the indicated position of the input pen are detected based on the difference in the phase of the detection signal of the input pen in the second drive mode where the phase relationship of each drive signal is reversed and added, and the error is canceled out to improve the detection accuracy. It is intended to improve

[Industrial application field]

The present invention relates to a coordinate detection method that can accurately detect the coordinates of an input pen's instruction signal in a coordinate input device called a digitizer or tablet.

Coordinate input devices called digitizers or tablets are known that detect the indicated position of an input pen as two-dimensional coordinates at high speed, process the input information of characters and figures by the input pen, and display the information on a display device, for example. There is. In such a coordinate input device, it is important to accurately detect the position indicated by the input pen in order to accurately input characters and figures drawn with the input pen to the processing device. Furthermore, in order to follow the movement of the input pen and detect its position, it is desired to improve the accuracy of coordinate detection.

[Conventional technology]

Various configurations of coordinate input devices are already known, and a conventional example using a planar resistor having uniform resistance is shown in FIG. In the figure, 31 is a planar resistor, 32 is an input pen that detects the signal on the planar resistor by capacitive coupling, and 33 is a reference drive signal φ ₁ and a drive signal φ ₂ having a 90° phase difference. 34 is a switching circuit, 35 is an amplifier including a filter and amplifies the input pen detection signal, and 36 is a phase detection section.

The reference drive signal φ ₁ from the drive signal generator 33 is applied to one side a of the planar resistor 31, and the reference drive signal φ 1 is applied to the other side b via the switching circuit 34 at the same frequency and amplitude as the reference drive signal φ ₁ . , when driving signals φ ₂ with phases different by 90° are added, the sides a and b of the planar resistor 31
The signal phase at a position x (normalized to 0<x<1) in between is expressed as θ=tan ⁻¹ x/1−x (1). Input this signal with pen 32
The detection signal is amplified by an amplifier 35 and applied to a phase detection section 36. Further, since the reference drive signal φ ₁ is added as a reference phase to the phase detection section 36, the phase of equation (1) is detected. In that case, since a phase shift occurs in the amplifier 35, the detected phase θ ₁ becomes θ+α. That is, the detected phase includes the phase error α.

Therefore, the switching circuit 34 switches the drive signal φ ₂ to the reference drive signal φ ₁ and applies it to the planar resistor 31 . In that case, since the reference drive signal φ ₁ of the same phase is applied to both sides a and b, the planar resistor 31
The upper signal phases are all 0°. Therefore, when the detection signal of the input pen 32 is amplified by the amplifier 35 and the phase is detected by adding it to the phase detection section 36, the detected phase θ ₂
becomes α.

Therefore, in the signal processing section (not shown), by performing the calculation θ ₁ - θ ₂ = (θ + α) - α = θ ... (2), it is possible to detect a phase that does not include error components. Can be done. Then, the coordinate x of the indicated position of the input pen 32 can be obtained from the following equation, which is obtained by reversing equation (1).

x=tanθ/1+tanθ...( ₃ ) Regarding the Y coordinate in the
By adding the drive signal φ ₂ and the drive signal φ 2 , the coordinates of the indicated position of the input pen 32 can be detected in a similar process.

[Problems to be Solved by the Invention] In the conventional example described above, the phase error α is detected after the phase detection of the detection signal of the input pen 32 is performed, and the phase error α detection process is performed. In this case, the phase error component by the amplifier 35 is simply detected, and is not related to the indicated position of the input pen 32, so that sufficient detection accuracy cannot be obtained. Furthermore, since coordinate detection is performed in the first detection process out of the two detection processes, and then correction process is performed, there is a drawback that the actual detection speed becomes low.

The present invention aims to improve detection accuracy by effectively utilizing detection processing.

[Means for solving problems]

The coordinate detection method of the present invention performs coordinate detection using a first drive mode and a second drive mode, and will be explained with reference to FIG. 1.

The reference drive signal φ 1 from the drive signal generator 3 is applied to one of the two opposing sides a, b or c, d of the uniform planar resistor 1, and the reference drive signal φ ₁ is applied to the other side. A drive signal φ ₂ having the same frequency and amplitude as the signal φ ₁ and a phase difference of 90° is added, the detection signal of the input pen 2 is amplified by the amplifier 6, and the phase detection unit 7 converts the signal to the phase of the reference drive signal φ ₁ . A first drive mode is used to compare and detect the coordinates of the indicated position of the input pen 2, in which a reference drive signal φ ₁ is applied to one side of the planar resistor 1 and a drive signal φ ₂ is applied to the other side. and a second drive mode in which the drive signal φ ₂ is applied to one side and the reference drive signal φ ₁ is applied to the other side,
The switching circuits 4 and 5 switch at a predetermined period to change the phase of the detection signal in the first drive mode and the second drive mode.
The coordinates of the indicated position of the input pen 2 are detected from the difference between the phase of the detection signal in the drive mode.

[Effect]

In the first drive mode, the switching circuit 4 selects and outputs the reference drive signal φ ₁ and applies it to the side a of the planar resistor 1, and the switching circuit 5 selectively outputs the drive signal φ _{2 and} applies it to the side a of the planar resistor 1. It is added to side b of resistor 1. Input pen 2 from side a of planar resistor 1
When the position of is set to x, the phase θ ₁ detected by the phase detection section 7 becomes θ ₁ =θ+α.

However, θ=tan ⁻¹ x/1−x, α=phase error in the amplifier 6, etc.

In the second drive mode, the switching circuit 4 selectively outputs the drive signal φ ₂ and the planar resistor 1
The reference drive signal φ ₁ is selectively outputted by the switching circuit 5 and applied to the side b of the planar resistor 1 . The position x of the input pen 2 from side a is
If the position is the same as in the first drive mode,
The phase θ ₂ detected by the phase detection section 7 is θ ₂ =
θ′+α. Note that θ' is the phase on the planar resistor 1 directly below the input pen 2, and the second drive mode is the one in which the drive signal is switched with respect to the first drive mode, and the input pen 2 Since the position x from side a is normalized, the position from side b is 1-x. Therefore, x in equation (1) can be changed to (1
-x), θ'=tan ^-1 1-x/1-(1-x) = tan ^-1 1-x/x = 90°-tan ^-1 x/1-x = 90°-θ ...(4) becomes.

Then, using the phase θ ₁ detected in the first drive mode and the phase θ ₂ detected in the second drive mode, θ ₁ −θ ₂ +90/2 = (θ+α) − [( By performing the calculation 90−θ)+α]+90/2 =θ, it is possible to obtain the phase θ that does not include the error component α, and by converting this using equation (3), the phase θ of the input pen 2 can be obtained. The position x can be determined.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 2 is a block diagram of an embodiment of the present invention,
11 is a planar resistor, 11a is an electrode arranged separately from each other, 12 is an input pen, 13 is a drive circuit,
14 and 15 are switching circuits, 16 is a reference clock generation circuit, 17 is a frequency divider, 18 is an amplifier, 19 is a filter, 20 is a comparison circuit for waveform shaping, 21 is a phase comparison circuit, 22 is a counter, and 23 is a control - Arithmetic circuit, 24 is an output terminal.

For example, the planar resistor 11 is formed by forming a thick film resistor on an insulating substrate, forming electrodes 11a on each side a to d, and connecting the drive circuit 13 to each side (sides c and d of the planar resistor 11). (The structure connected to the resistor is not shown in the figure), and a thin insulating sheet is formed on a thick film resistor. Alternatively, a transparent planar resistor may be formed by forming tin oxide or the like as a resistor on a glass substrate by vapor deposition or the like and covering it with a transparent thin insulating sheet. In this way, the surface of the input pen 12 is protected by the insulating sheet, and the input pen 12 detects the electric field on the planar resistor 11 through capacitive coupling. For example, when the input pen 12 is brought into contact with the surface of the planar resistor 11, an electrostatic coupling capacitance of, for example, about 0.2 pF is obtained because the insulating sheet is interposed.

Further, the clock signal from the reference clock generation circuit 16 is frequency-divided by the frequency dividing circuit 17, for example, 3 to 3.
A square wave reference drive signal φ ₁ with a frequency of about 4KHz
and a drive signal φ ₂ having a 90° phase difference therefrom are outputted and applied to switching circuits 14 and 15.
The switching circuits 14 and 15 switch between the reference drive signal φ ₁ and the drive signal φ ₂ in accordance with a switching control signal of a predetermined period from the control/arithmetic circuit 23.
The reference drive signal φ ₁ is applied to the side a of the planar resistor 11, and the side b
A first drive mode in which a drive signal φ ₂ is applied to each side, and a second drive mode in which an error signal φ ₂ is applied to side a, and a reference drive signal φ ₁ is applied to side b, respectively.

The drive circuit 13 amplifies the reference drive signal φ ₁ or the drive signal φ ₂ and applies it to the planar resistor 11 as a drive signal of approximately 5V. An electric field of corresponding phase is generated. Therefore, by pointing or moving a desired position with the input pen 12, a signal is induced in the input pen 12 by capacitive coupling, this signal is amplified by the amplifier 18, and filtered into the fundamental frequency component by the filter 19. is extracted, compared with a reference value by the comparison circuit 20, converted into a binary signal, and applied to the phase comparison circuit 21.

In the phase comparator circuit 21, the reference drive signal φ ₁ and
A phase comparison with the output signal of the comparator circuit 20 is performed,
A signal with a pulse width corresponding to the phase difference is output.
This signal is applied to the counter 22 as a count enable signal, so the counter 22 counts the clock signal from the reference clock generation circuit 16. The count content of this counter 22 counts the pulse width of the phase comparison output signal, so it indicates the phase θ ₁ (or θ ₂ ) of the detection signal of the input pen 12 with respect to the reference drive signal φ ₁ , and is used for control. - Added to the arithmetic circuit 23.

The control/arithmetic circuit 23 calculates θ=(θ ₁ −θ ₂ +90)/from the phase θ ₁ detected in the first drive mode and the phase θ ₂ detected in the second drive mode.
2, the phase θ that does not include the phase error component α generated in the amplifier 18 etc. is determined, and based on the signal of this phase θ, as shown in equation (3), x=tanθ/
By calculating (1+tanθ), a process for determining the position x in the X coordinate of the input pen 12 is performed.

Also, regarding the sides c and d of the planar resistor 11, in the same manner as described above, the phase error component is calculated from the phase detected in the first drive mode and the phase detected in the second drive mode. Find the phase that does not include
Processing is performed to obtain the position y in the Y coordinate of the input pen 12 from the phase, and the X, Y coordinates of the input pen 12 are
It is possible to detect the position x, y in the coordinates,
The data is transferred from the output terminal 24 to a display device (not shown).

Note that after switching from the first drive mode to the second drive mode or vice versa, the phase comparison of the detection signal of the input pen 12 is performed after a predetermined period of time when the signal phase on the planar resistor 11 becomes stable. It is preferable to perform control to perform the following. Further, the present invention is not limited to the above-described embodiments, and various additions and changes can be made.

〔Effect of the invention〕

As explained above, the present invention provides the detection signal phases θ _{1 and} θ in the first drive mode and the second drive mode in which the phase relationship of the drive signals in the first drive mode is reversed. ₂ contains information regarding the position of the input pen 2, and therefore, the process of determining the phase of the detection signal of the input pen 2 based on the difference between the phase θ ₁ and the phase θ ₂ is performed twice. This corresponds to finding the average value of phase measurements, and since phase error components can be removed, there is an advantage that coordinate detection accuracy can be improved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the principle of the present invention, FIG. 2 is a block diagram of an embodiment of the present invention, and FIG. 3 is an explanatory diagram of a conventional example. 1 is a planar resistor, 2 is an input pen, 3 is a drive signal generator, 4 and 5 are switching circuits, 6 is an amplifier, and 7 is a phase detector.

Claims (1)

[Claims] 1. A reference drive signal φ 1 is applied to one of the two opposing sides of a uniform planar resistor 1, and a reference drive signal φ ₁ is provided to the other side, and has the same frequency and amplitude as the reference drive signal φ ₁ . In a coordinate detection method in which a drive signal φ ₂ having a phase difference of 90° is applied, and the coordinates of the indicated position of the input pen 2 are detected based on the detection signal phase of the position indicated by the input pen 2, one of the planar resistors 1 a first drive mode in which the reference drive signal φ ₁ is applied to one side of the planar resistor 1 and _{the drive signal φ 2 is} applied to the other side; A second drive mode in which the reference drive signal φ ₁ is applied to the other side is switched at a predetermined period, and the phase of the detection signal in the first drive mode and the phase in the second drive mode are changed. A coordinate detection method characterized in that the coordinates of the indicated position of the input pen 2 are detected from the difference between the phase of the detection signal and the phase of the detection signal.