JPS6029964B2 - Coordinate detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a coordinate detection device that detects the position of an input point.

FIG. 1 is a perspective view showing the configuration of a conventional position coordinate detection device, in which 1 is a fixed plate, 2 is a first parallel electrode group that is flexible, and 3 is a second parallel electrode that is also flexible. 4 is a first resistor in contact with one end of the first parallel electrode group 2; 5 is a second resistor in contact with one end of the second parallel electrode group 3; 6, 7, and Reference numerals 8 and 9 are electrodes provided on the first and second resistors 4 and 5, respectively.

The insulating substrate 11 is a pressure-sensitive rubber sheet that is conductive only in the vicinity of the pressed point.

Further, a, b, c, d are the electrodes 6, 7, 8, respectively.
9, and W indicates the input surface.
FIG. 2 is a configuration diagram showing details of the first parallel electrode group 2, in which electrodes Y,, Y2,...YN are placed on an insulating substrate 10.
are arranged in parallel.

Further, the second parallel electrode group in FIG. 1 is similarly constructed by arranging electrodes X, X2, . . . , xN in parallel on the insulating substrate 10. The first parallel electrode group 2 and the second
The parallel electrode groups 3 are orthogonal, and both parallel electrode groups 2,
3 are facing each other on the inside, and a pressure sensitive rubber sheet 11 is provided between the first parallel electrode group 2 and the second parallel electrode group 3.
When characters or figures are written on the input surface W, which is the back surface of the second parallel electrode group 3, conduction occurs at the point where the pressure-sensitive rubber sheet 11 is pressed by the pressure of the pen, and the first parallel electrode group 2 and One electrode in each of the second parallel electrode group 3 is adapted to be conductive. FIG. 3 is a detailed diagram of a conventional position detection circuit, in which 12 is a constant current source, 13, 14 are obeamps, 15,
16 is a microresistance, 17 and 18 are each an X output terminal,
This is the Y output terminal.

19 is a current detection circuit, and 20 is a pen down output terminal.

Note that other symbols indicate the same parts as in FIG. To operate this, in Fig. 1, the first parallel electrode group 2 and the second
Input surface W above the part where the parallel electrode group 3 overlaps
For example, when characters, figures, etc. are written with a pen, the pressure-sensitive rubber sheet 11 conducts the second parallel electrode group 3 and the first
Each one electrode in the parallel electrode group 2 is adapted to Ben's pen pressure.

Therefore, as shown in FIG.
The x-coordinate and y-coordinate can be detected by the current flowing in and out of the terminal c and the current flowing in and out of the terminal c and terminal d.

However, as shown in FIG. 4, which shows an example of the output waveform, as the input point moves, the output waveform becomes step-like and noise is added due to the chatter of the pressure-sensitive rubber sheet 11, resulting in poor detection accuracy. There were drawbacks that seriously impaired the

In order to eliminate these drawbacks, the present invention provides a position coordinate detection device with a low-pass filter function only while the pen is down.

Hereinafter, the invention will be explained in detail with reference to the drawings. FIG. 5 shows an embodiment of the present invention, in which 100 is a position coordinate detection device, 101 is a detection x signal terminal, 102 is a detection y signal terminal, 103 is a detection z signal terminal, 110 and 111 are variable filter circuits, 112 is a z signal processing circuit, 120 is an x signal processing circuit
Signal output terminals 121 are y signal output terminals, and 122 are z signal output terminals.

6a to 6c are signal waveform diagrams for explaining the operation of the present invention.

FIG. 7 shows the variable filter circuits 110 and 11 shown in FIG.
1, 13 is a coordinate signal input terminal, 131 is a switching signal input terminal, 132 is a coordinate signal output terminal, 13
is an obeamp.

Further, R, , R2, R', , R'2 are resistors, C is a capacitor, and T, , T2 are analog switches. 8A to 8D are waveform diagrams for explaining the operation of the variable filter circuits 110 and 111 of FIG. 7. Next, the operation of the embodiment shown in FIG. 5 will be explained using FIG. 6.

The position coordinates are detected by a position coordinate detection device 10 constructed according to the prior art.

Signals corresponding to the detected x and y coordinates are output to a detection x signal terminal 101 and a detection y signal terminal 102, respectively. Also, the z signal indicating Ben's up and down is
It is output to the detection z signal terminal 103. The detected z signal enters the z signal processing circuit 112 and undergoes processing as shown in FIG. 6c. This process converts the input signal shown in FIG.
As shown in FIG. 6b, the signal delayed by a certain period of time ro and the input signal are ANDed. On the other hand, detection x
Signals from signal terminal 101 and detection y signal terminal 102 enter variable filter circuits 110 and 111, respectively.

When the z signal indicates pen-down, the variable filter circuits 110 and 111 operate as low-pass filters with cutoff frequency fL, and when the z signal indicates pen-up, the variable filter circuits 110 and 111 operate at cutoff frequency fH. It performs a low-frequency filter operation with a As will be described later, by setting fL<<fH, it is possible to smooth the x, y coordinate signals while minimizing the delay of the x, y coordinate signals immediately after bending down. Next, an example of how to configure the variable filter circuits 110 and 111 will be described.

In the circuit shown in FIG.
When the switching signal input from the pen is in a state indicating pen down, the ana.

The analog switches T,, T2 are non-conductive, and when the switching signal indicates pen-up, the analog switches T,, T2
is designed to be suitable. Therefore, the transfer function between the signal o inputted from the coordinate signal input terminal 130 and the signal o outputted to the coordinate signal output terminal 132 is as follows. fire.

R′ ・hi RI+j CR However, is the angular frequency.

Also, R and R' are R when the switching signal is pen down.
=R, 10R2. R=R', R'2, and when the switching signal is pen-up, R=R, , R'=R',.

Here R, = R', , R2 = R'2, CR, = 1/fH
, CR2=1/fL-1/fH, it is possible to change only the cutoff frequency without changing the DC gain in the bend-down or pen-up state.

Note that since there are several degrees of freedom between each element, a variable filter can be constructed without setting constants as described above. By doing this, the x or y coordinate signal from the position coordinate detection device 100 (FIG. 8a)
) becomes a smoothed signal as shown in FIG. 8b by switching the cutoff frequencies of the variable filter circuits 110 and 111 using the z signal (FIG. 8c).

Note that the switching response time and rise time of the variable filter circuits 110 and 111 are different. By delaying the z signal by 100 ms as shown in FIG. 8d, it is possible to obtain the correct x and y coordinates immediately after bending down. As described in detail above, the present invention can smooth the coordinate signal without causing any delay in the rise or fall of the coordinate signal by changing the filter characteristics during bend-down and pen-up.
This has the advantage of being able to remove noise generated in detection circuits and the like.

In addition, the x, y coordinate signals from the position coordinate detection device have a step-like waveform depending on the total interval of the electrode sheets, but according to the present invention, intermediate values are interpolated, so the equivalent This has the advantage that the resolution of the position coordinate detection device can be improved.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a configuration example of a conventional position coordinate detection device, FIG. 2 is a perspective view showing a configuration example of a parallel electrode group in FIG. 1, FIG. 3 is a conventional position detection circuit diagram, and FIG. The figure is an output signal waveform diagram obtained from the position coordinate detection device of the slave, FIG. 5 is a block diagram showing an embodiment of the present invention, and FIGS. 6 a to c
is a waveform diagram of the z signal processing circuit of the embodiment shown in FIG. 5, FIG. 7 is a detailed diagram of the variable filter circuit, and FIGS.
FIG. 3 is a waveform diagram for explaining the operation of the illustrated embodiment. In the figure, 100 is a position coordinate detection device, 101 is a detection x signal terminal, 102 is a detection y signal terminal, 103 is a detection z signal terminal, 110 and 111 are variable filter circuits, 112 is a z signal processing circuit, and 120 is an x signal 121 is a y signal output terminal, 122 is a z signal output terminal, 130 is a coordinate signal input terminal, 131 is a switching signal input terminal, 132 is a coordinate signal output terminal, and 133 is an oven amplifier. Figure 1 Figure 2 Figure 3 Figure M Figure 1. Figure 5 Figure 6 Figure 7 Figure 8

Claims (1)

[Claims] 1. A position coordinate detection device that detects the position coordinates and outputs a signal indicating the x-coordinate, y-coordinate, and pen-down, a low-pass filter whose cut-off frequency can be changed depending on pen-down and pen-up, and a cut-off frequency of the low-pass filter that changes when the pen is up. and means for lowering the cut-off frequency of the low-pass filter in a pen-down state.