JPS6277627A - Coordinate input device - Google Patents

Abstract

PURPOSE:To reduce the circuit scale of detecting circuits and to obtain a small- sized coordinate input device by providing a pen which incorporates a coil generating a magnetic field in response to an impressed carrier signal and also providing a filter amplifier to the detecting circuits. CONSTITUTION:Electric signals ax and ay generated by two scanning circuits 4X and 4Y which make a scan at the same time with the input from the pen 7 incorporating the coil generating the magnetic field in response to the carrier signal applied from an oscillator 50 are detected by detecting circuits 30X and 30Y. The filter amplifiers 31X and 313Y pass and amplify signal components of predetermined bands including the carrier frequencies of carriers of the electric signals ax and ay. They are detected by detectors 32X and 32Y and peak detecting circuits 33X and 33Y detect peak signals hx and hy. Coordinate signal generating circuits 8X and 8Y send out coordinate signals X and Y on the basis of the time differences between the peak signals hx and hy and a pulse signal (i) indicating the time corresponding to the origin of coordinates from a controller 6.

Description

[Detailed description of the invention] The present invention relates to a coordinate input device xvc.

Conventional 1 As a means of converting patterns such as characters and figures entered by handwriting into electrical signals, the position of the pen on the input surface of the tablet is electromagnetically detected and an electrical signal indicating the coordinates of the pen input position is generated. The coordinate input device is being used incorrectly. Two sets of conductor loops are provided on the human power side of the tablet, and the pen for inputting one line has a built-in coil, so that during handwriting input, there are two conductor loop groups on the input side and the coil of the pen. By detecting the electromagnetic coupling point of the pen, an electrical signal indicating the coordinates of the pen input position is generated.

FIG. 7 is a block diagram showing a conventional coordinate input device.
FIG. 8 is a time chart for explaining the operation. Immediately below the input surface 12 of the tablet 1, Ki1, two sets of conductor loops 10 and 11 are arranged orthogonally to each other, and a pen 7 for moderate input is provided with a coil l'9. Each set of loops 1O and 11 is given a multiphase burst signal, which is a multiphase pulse signal modulated by a carrier signal, from scanning circuits 3X and 3Y, and the X coordinate axis and the generates a magnetic field that travels along the The control circuit 5 sends a switching signal instructing switching of the scanning directions of the scanning circuits 3 A signal e in which a pulse rises at the timing
It is sent to the f coordinate generation circuit 8. For example, within one period T for generating a traveling magnetic field in the direction of the X coordinate axis, as shown in FIG. A magnetic field traveling along the X coordinate axis? generate. During input, that is, when handwritten input is made on the input surface 12 as shown by the broken line arrow A with the pen 7, the coil of the pen 7 interlinks with the traveling magnetic field, and the coil receives a voltage signal a corresponding to the change in the magnetic field strength. It is induced.

The switches S1 and S2 are both changeover switches for guiding the signal a to the detection circuit 20X (or 20Y) during scanning in the X-coordinate (or X-coordinate) direction. For example, during scanning in the X coordinate direction, the signal a is guided to the detection circuit 20X, amplified by the amplifier 21, detected by the detector 22, and sent to the filter 23 as a signal. A filter 23 extracts the fundamental wave component of the signal and sends it to an amplifier 24. The amplifier 24 amplifies the fundamental wave component of the signal C and sends it to the amplitude comparator 2. The amplitude comparator 25 generates a signal d whose pulse rises when the amplitude of the signal C becomes zero, and sends it to the ni coordinate generating circuit 8. Coordinate generating circuit 81-1% Generates a digital signal having a value proportional to the time t between the pulses r111 of the signal e and the signal d, and sends this as a coordinate signal. Since the pulse interval time t of the signal e and the signal d is proportional to the X coordinate of the input location, the coordinate signal indicates a digital value proportional to the X coordinate of the input location.

When scanning in the X coordinate direction, the signal a is guided to the detection circuit 20Y, and the coordinate generation circuit 8 generates a coordinate signal of a digital value proportional to the Yi mark at the input location in the same manner as described above.

In such a conventional coordinate input device, when switching scans in both directions, two detection circuits 20X and 20Y' are provided and switched alternately in order to prevent mutual interference of signals C caused by scanning in each direction. There is a need. Since the sweet filter 23 extracts only the fundamental wave component, its amplitude becomes small, and an amplifier 24 is required to amplify this component.Furthermore, the frequency F of the fundamental wave component extracted by the filter 23 is approximately 1/(2).
(d) (fc and T is the scanning period in each coordinate direction), the frequency is necessarily quite low, and the filter 23 becomes large. For this reason, the conventional coordinate input device has the disadvantage that the circuit scale of the detection circuits 20X and 20Y becomes large, resulting in an increase in the size and cost of the device.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned problems and to provide a coordinate input device which has a smaller circuit scale than the conventional one and is therefore small and inexpensive.

The device of the present invention includes a pen having a built-in coil that generates a magnetic field in response to an applied carrier wave signal, and two sets of conductor loops arranged below an input surface, so that the input surface by the pen is The electric signals induced in the two sets of loops in response to the magnetic field are scanned simultaneously when the first and second loops are input.
A pair of Tonami amplifiers that pass and amplify signal components of a predetermined bandwidth including the frequency of the carrier wave of the first and second electric signals. What is the means for detecting the Tonami amplified electrical signal? a pair of peak detection means for detecting the peak of the waveform of the detected electrical signal and generating third and fourth electrical signals indicating the time of the peak, corresponding to the origin of the coordinates; It is characterized by transmitting a coordinate signal indicating the coordinates of the input location in response to the time difference VC between the pulse signal indicating the time at which the input point and the third and fourth electric double angles are set.

Next, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a time chart for explaining its operation.

In this embodiment, the carrier wave current ? generated by the oscillator 50 in a coil (not shown) in the pen 7? The current flows to generate an alternating magnetic field, and each conductor loop of tablet 1 (not shown) is
The coordinates of the input location are detected by sequentially scanning the voltages induced in the input point.

The scanning circuits 4X and 4Yld sequentially scan the induced voltage of each conductor loop of the tablet l, and the respective detection circuits 30X
, leads to 30Y. Filter width filter 3 of detection circuit 30X],
Then, high frequency components of both side band components with respect to the carrier wave are removed from the signal ax, the stepped envelope of the signal ax is smoothed, and a signal fx having a smooth envelope is sent to the detector 32X. In order to obtain a signal fx with a smooth envelope, the carrier frequency iF. Let the scanning frequency be FB (however, each scanning time of signals x1 to XN, that is, the burst length k TB, and the scanning frequency FB = 1/TB)
%F wave width filter 31XP wave characteristics, CFo-FB)
Attenuation amount in the following frequency bands and in the frequency band above (F, +FB)? If you set it large enough, it will work. Detector 32
X detects the signal fx and sends the detected signal gxk to the peak detection circuit 33X. When a synchronous detector is used as the detector 32X (Fig. 5), the signal g after detection at vc is the second
In contrast to the voltage waveform shown by the solid line in the figure, when an envelope detector is used (Fig. 1), the TIC signal g becomes the voltage waveform shown by the broken line, and the carrier wave is transferred to the F wave width detector 31.
If the signal is added before envelope detection (Fig. 6), the signal g
x has a voltage waveform as shown by the solid line.

In the case of No. 11 as well, the peak detection circuit 33X detects the signal g.
A signal hX, in which a pulse rises at the peak of the waveform, is generated and sent to the n, i coordinate generation circuit 8X. Coordinate generation circuit 8X
generates a digital signal with a value proportional to the pulse interval time t between the signal i and the signal hx, in which the pulse rises at the timing corresponding to the origin of each coordinate r sent from the control circuit 6, and converts this n into the coordinate Send as a signal.

Note that in Figures 1, 5, and 6, the detection circuit 30
The Y and coordinate generation circuit 8Y operates exactly the same as the above-described test output circuit 30X and coordinate generation circuit 8X, and generates a coordinate signal for the Y coordinate.

Figure 3 (a) and (bl is the real side VC)
A block diagram showing an example of the configuration of the peak detection circuit 33X (33Y) and its operation t! This is a time chart for clarity. The detected signal gx[gy] is sent to an amplitude comparison circuit 34 and a differentiation circuit 35. Differential circuit 35
is a signal by differentiating the waveform of signal gx(g,),
This fl' is sent to the zero-crossing detection circuit 36. The zero crossing detection circuit 36 generates a signal 1-fz which rises as a pulse every time the signal waveform becomes zero level, and sends this signal to the 10,000 input terminal of the AND gate 37.

On the other hand, the amplitude comparison circuit 34 generates a signal mf which rises as a pulse only when the voltage of the signal g exceeds a predetermined threshold voltage t, and sends the signal mf to the other input terminal of the AND gate 37. The logic value gate 37 sends out a signal hx (h,) which is a logical product signal of signals l and m(D).
, ), even when there is no noise, there are places where the differential value becomes zero other than the peak, and when external noise is added, the signal g
The differential value becomes zero even at the peak of the noise in the part where the voltage of Erroneous peak detection can be prevented by sending out only the pulse of the signal 1 when the voltage exceeds the threshold voltage Vt.

FIG. 4 shows the peak detection circuit 33X (33Y) of this embodiment.
FIG. 3 is a block diagram showing another example of the configuration.

In this configuration example, the amplitude comparison circuit 340 in the circuit shown in FIG.
) Comparison circuit 3 that can be varied in response to the peak of
8 is conveniently used. That is, the predetermined threshold voltage V1
Instead of the signal gx(g,)i, the peak holding circuit 40 and the amplitude adjustment circuit 41V? - The threshold voltage obtained by passing through the amplitude comparator circuit 42I/c is sent.

This threshold voltage is a constant multiple of the peak voltage of the signal gx(g,), and the signal gx(g,
) When the voltage exceeds the threshold voltage, a signal is generated in which three pulses rise.

Therefore, by adding 3 to an appropriate value in advance in the amplitude adjustment circuit 41 of this threshold voltage and the beam voltage of the signal g (g), fluctuations in the peak voltage of the signal gx (g,) can be reduced. Even if the peak of the signal gx(gy) exists, the peak of the signal gx(gy) can be detected reliably.

The detection circuits 30X and 30Y of this embodiment detect the peaks of the detected signals g x and g y, and the large filter 23 for low frequencies unlike the conventional one is not necessary. Furthermore, since there is no mutual interference between signals caused by switching the Erica scanning direction when R waves are generated by the filter 23, the X and Y axes can be scanned simultaneously, and the number of detections can be doubled compared to the conventional method. Note that the filter portions of the Tonami amplifiers 31X and 31Y are good at extracting all the frequencies near the high-frequency carrier signal, and can be made much smaller than the conventional filter 23. Therefore, the detection circuit 30X of this embodiment.

30YH1 Compared to the conventional detection circuits 20X and 20YVc, it can be made smaller and lower in size.

As is clear from the above description, the present invention has the effect of realizing a coordinate input device that has a smaller circuit scale than the conventional one and is therefore compact and inexpensive.

[Brief explanation of drawings]

1, 5, and 6 are block diagrams showing an embodiment of the present invention, FIG. 2 is a time chart for explaining the operation of the embodiment of the present invention, and FIG. 3 is a block diagram showing an embodiment of the present invention. FIG. 8 is a time chart for explaining the operation of FIG. 7. 1...Tablet, 10.11...Loop, 12...Input surface, 3X, 3Y, 4X, 4
Y...Eating reduction circuit, 5,6...Control circuit, 7...Pen, 8X. 8Y...Coordinate generation circuit, 20X, 20Y, 30
X. 30Y...detection circuit, 31X, 31Y...
...F wave width detector, 32X, 32Y...detector,
33X, 33Y...Peak detector, 34.42
......Amplitude comparator, 35...Differentiating circuit, 3
6... Zero crossing detection circuit, 37... AND gate, 40... Peak holding circuit, 41...
... Vibration @ adjustment circuit, 50 ... Oscillator, 51.
...Switching circuit. Agent Patent Attorney Susumu Uchihara - T-□1 Bud 2 Figure (a) (b) A 9 WA Figure 4 Figure 5 Figure Otsu El Figure 7 Figure T-1111111 calculation Figure 3

Claims (8)

[Claims] (1) A pen with a built-in coil that generates a magnetic field in response to an applied carrier wave signal, and two sets of conductor loops arranged below the input surface, and when inputting to the input surface with the pen, A coordinate input device comprising: a tablet that simultaneously scans electrical signals induced in two sets of the loop groups in response to the magnetic field and sends out first and second electrical signals; a pair of filtering and amplifying means for passing and amplifying a signal component of a predetermined bandwidth including the frequency of the carrier wave of the signal; a pair of detection means for detecting the filtered and amplified electric signal; and a pair of detection means for detecting the filtered and amplified electric signal, and the detected electric signal. a pair of peak detecting means for detecting the peak of the waveform of and generating third and fourth electrical signals indicating the time of the peak, and a pulse signal indicating the time corresponding to the origin of the coordinates and the third and A coordinate input device characterized in that it transmits a coordinate signal indicating the coordinates of an input location in response to each time difference with a fourth electrical signal. (2) The coordinate input device according to claim 1, wherein the filtering and amplifying means has a passing bandwidth set to be equal to or less than twice the scanning frequency within the loop group. (3) The coordinate input device according to claim (1), wherein the detection means is an envelope detector. (4) The coordinate input device according to claim (1), wherein the detection means is a synchronous detector. (5) A patent in which the detection means is an envelope detector that adds a carrier signal to the first and second electric signals in front of the filtering and amplifying means and then envelope-detects the filtered and amplified electric signals. A coordinate input device according to claim (1). (6) Claim (1) wherein the peak detection means generates the third and fourth electrical signals by differentiating the waveform of the detected electrical signal and then detecting its zero crossing point. Coordinate input device as described. (7) The coordinate input device according to claim (6), wherein the peak detection means detects the zero crossing point only when the detected electrical signal exceeds a predetermined threshold voltage. (8) Claim (6) wherein the peak detection means detects the zero crossing point only when the detected electrical signal exceeds a threshold voltage determined in response to the peak of its own waveform. Coordinate input device described in section.