JP3270544B2 - Coordinate input device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coordinate input device for inputting coordinates by receiving electromagnetic waves or the like through a wire grid or the like using a pen or cursor that oscillates electromagnetic waves or the like.

[0002]

2. Description of the Related Art Conventionally, a pen / cursor or the like for indicating a position to a coordinate input device using an electromagnetic wave or the like is usually configured as shown in FIG. In FIG. 8, reference numeral 2 denotes an output unit of an electromagnetic field generating coil or the like (in the case of using ultrasonic waves, a piezoelectric speaker or the like), 4 denotes an excitation unit of the output unit 2, 9 denotes a control unit such as a microprocessor, and 10 denotes a control unit such as a microprocessor. It is a power supply and is built in the pen body 1.

FIG. 9 shows an example of a typical input voltage to the output section 2 in the conventional example shown in FIG. That is, a waveform having a constant frequency and amplitude or the like is constantly or intermittently input to the output unit 2 as shown in FIG. 9, and the frequency and amplitude of the input waveform are determined by the external noise mode or the output unit 2. The structure was controlled without having a correlation with the electromagnetic field intensity actually induced in the external environment.

FIG. 10 shows a configuration example of a typical receiving unit (wire grid or the like) side in a conventional example. That is, under the control of the receiving side control unit 19, the multiplexer 17 operates, and the voltages induced by the output from the pen 1 are sequentially taken into the grids 11 installed in the X and Y directions via the amplifier 20. . FIG. 11 is a diagram showing this state. That is, the setting of the multiplexer 17 changes one after another, and the voltage generated in the grid selected by the multiplexer 17 is input to the amplifier 20. Amplifier 20 amplifies and outputs the input voltage.

FIG. 12 shows a state in which the input coordinate position is estimated in either the X or Y direction based on the induced voltage taken from the grid. That is, the grids are usually arranged at intervals of several mm to several tens of mm.
In order to obtain a coordinate accuracy of about / 100 mm, usually, a pattern of an estimated curve like a solid line 121 in FIG. Then, the pattern of the estimated curve is matched, and the coordinate position is calculated from the zero cross point (in the case of FIG. 12), the peak point, and the like.

[0006]

However, in the above-mentioned conventional example, the input voltage waveform to the output unit 2 varies depending on the mode of external noise or the electromagnetic field intensity actually induced in the external environment by the output unit 2. Since it is not configured, it has the following disadvantages.

(1) During use, if an external noise including a component having a frequency and an amplitude similar to the input voltage waveform arrives, the performance of the coordinate input device, such as accuracy and responsiveness, is reduced due to interference by the noise. There is a risk of significant deterioration.

(2) The only way to increase the performance degradation resistance under the arrival of external noise without affecting the basic method of the coordinate input device is to increase the amplitude of the input voltage to the output unit 2 uniformly. The power consumption of the power supply 10 is increased, and particularly in a wireless pen or the like, the cost, superposition, or replacement frequency of the power supply 10 is increased, which is extremely inconvenient.

(1) will be further described with reference to FIGS.

As described above, the method of estimating coordinates on the normal coordinate detection medium side (hereinafter referred to as the receiving side) is based on the premise that the distortion of a directivity pattern such as a pen cursor can be detected in a sufficiently small state. If the voltage pattern induced in the grid by the cursor or the like (hereinafter referred to as reception pattern) is distorted or fluctuated by external noise, errors and jitters are mixed in the estimated coordinates.
The relationship between the S / N ratio and the coordinate estimation error on the receiving side is usually shown in FIG.
Since the error increases rapidly when the S / N ratio deteriorates, the estimation accuracy rapidly increases when external noise is large due to, for example, a power cord for supplying a large current or a CRT display being nearby. It was supposed to deteriorate.

Also, depending on the algorithm for estimating the coordinate position, an attempt to increase the estimation accuracy in a state where the S / N ratio is low increases the calculation time, which results in a deterioration in the responsiveness of the coordinate input. There were cases.

The present invention has been made in view of the above conventional example, and has as its object to provide a coordinate input device capable of inputting coordinates with high accuracy and stability.

[0013]

To achieve the above object, a coordinate input device according to the present invention has the following configuration. A coordinate input device comprising: a coordinate designation unit that outputs a signal; and a main body that detects a signal output from the coordinate designation unit and determines a coordinate position designated by the designation unit. Transmitting means for transmitting a variable frequency signal, receiving means for receiving the variable frequency signal, means for changing the frequency of the signal received by the receiving means, and received by the receiving means, other than the transmitting means Selecting means for selecting a frequency having the lowest signal level from signals from the signal source, wherein the frequency selected by the selecting means is used as the transmitting frequency of the transmitting means.

Preferably, the main unit includes a receiving unit for receiving a signal of a variable frequency, a unit for changing a frequency of a signal received by the receiving unit, and a signal having the highest signal level among the signals received by the receiving unit. Selecting means for selecting a high frequency, and the frequency selected by the selecting means is used as the receiving frequency of the receiving means.

Preferably, the signal is an electromagnetic wave.

[0016]

【Example】

[First Embodiment] As a first embodiment of the present invention, a coordinate input device for detecting and inputting an electromagnetic wave by a grid will be described.

FIG. 1 is a drawing which best illustrates the features of the present invention. In FIG. 1, reference numeral 1 denotes a housing of a coordinate pointing device such as a pen / cursor (hereinafter referred to as a pen 1
2) an output medium such as a coil for outputting an electromagnetic wave or the like (hereinafter referred to as an “output coil”); 3 a coil, a sensor, etc. for detecting the electromagnetic field intensity or the like near the medium of the pen 1 ( 4 is an output coil 2
An excitation unit that supplies a signal for generating electromagnetic waves and the like to the
Reference numeral 5 denotes a band-pass filter (BPF) for extracting only the frequency component of the waveform output from the excitation unit 4 out of the output of the detection coil 3, and 6 denotes a control for controlling the amplitude of the output waveform of the excitation unit 4. A D / A conversion circuit, 7 is a detector for detecting the envelope of the band-pass filter 5, and 8 is an A / D for digitizing the output of the detector 7 and transmitting it to the control unit 9.
The conversion circuit 10 is a power supply for supplying power to each circuit of the pen 1, and 11 is a coordinate detection medium (hereinafter, referred to as a wire grid) such as a wire grid for detecting coordinates specified by receiving an electromagnetic wave or the like from the output coil 2. According to an instruction from the reception-side control unit 19, the grid 17 selects one of the grids developed in each of the X and Y directions for each direction.
A multiplexer for transmitting the voltage induced in the selected grid to the amplifier 18 having an automatic gain adjustment function;
Reference numeral 8 denotes an amplifier with an automatic gain control function (AGC) for automatically controlling the gain so that a signal having a constant amplitude is input to the receiving side control unit 19 even if the output from the pen cursor changes. Is a receiving side control unit which controls the multiplexer 17, estimates coordinates, and outputs the estimation result to the outside.

FIG. 2 is a diagram showing the operation of the coordinate input device of FIG. In FIG. 2, when the input of the signal voltage to the output coil 2 is stopped, the control unit 9 outputs the output coil 2 through the detection coil 3, the BPF 5, the detector 7, and the A / D converter 8. It is detected whether or not the external noise of the frequency component to be arrived near the pen 1. Based on the result, a signal waveform having a predetermined amplitude level is applied to the output coil 2 so as to secure the allowable S / N ratio shown in FIG. Therefore, in a state where the noise has arrived, a signal waveform having an amplitude increased according to the amplitude of the noise is applied to the output coil 2. In general, when coordinates are instructed by the pen 1, the pen 1 and the grid 11 are almost in contact with each other. Therefore, by performing control as shown in FIG. The noise-to-noise ratio will be maintained.

On the other hand, on the receiving side, the gain of the amplifier 18 with automatic gain adjustment function is automatically adjusted, and the amplitude of the signal input to the receiving side control unit 19 is kept constant as shown in FIG. That is, extraneous noise is suppressed by that much.

The detection of the external noise can be performed only once when the supply of the voltage to the output coil 2 is started.
By making the voltage supply to the output coil 2 intermittent and detecting the noise and adjusting the amplitude of the signal waveform immediately before the start of the voltage supply in each cycle, even when the form of the external noise fluctuates, Can be adjusted for the amplitude.

Further, in the present embodiment, the frequency of the electromagnetic wave generated from the output coil 2 is always constant, and the grid 11 always needs to focus on a single frequency for processing, and the circuit on the receiving side is relatively simple. There is an advantage that it can be done.

[0022]

[Other embodiments]

[Embodiment 2] FIG. 3 is a view of a coordinate pointing device according to a second embodiment of the present invention. In the figure, reference numeral 12 denotes a voltage controlled oscillator (V) that changes the output frequency according to the output voltage of the D / A converter 6.
CO), 13, 21 are VCOs, 22,, which generate variable frequencies in order to multiply detect only a specific frequency component of the output voltage of the output coil 3 and the grid 11.
Reference numeral 14 denotes a low-pass filter (LPF) constituting the product detection circuit, and reference numeral 15 denotes a multiplication circuit that multiplies the output signal of the VCO by the output signal of the LPF.

FIG. 4 is a diagram showing the operation of the embodiment of FIG.

In the first embodiment, the amplitude of the voltage applied to the output coil 2 is adjusted according to the mode of the external noise. In the present embodiment, the frequency of the applied voltage is changed. . That is, as shown in FIG. 4, prior to the start of the supply of the input voltage to the output coil 2, that is, the output voltage of the VCO 12, the control unit 9 controls the V / V
By controlling the CO 13 and performing multiplication detection by the LPF 14 and the multiplier circuit 15 on a plurality of frequency components (f ₁ and f _{2 in} FIG. 4) defined in advance, the electromagnetic field intensity of the external noise of each frequency component Is detected. Thereafter, a frequency (f _{1 in} FIG. 4) having the lowest noise level is selected from the plurality of frequencies, and the VCO 12 is controlled so that a signal voltage (amplitude is not particularly defined) of the selected frequency is output to the output coil 2. ) Is applied. The application of the voltage to the VCO 12 intermittently and the adjustment of the frequency in each cycle can be applied to the case where the mode of the external noise fluctuates, similarly to the first embodiment.

The processing on the receiving side in this embodiment will be described with reference to FIG. That is, the receiving side control unit 19 controls the VCO 21 to perform multiplication detection of a plurality of frequency components defined in advance, detects a frequency having the maximum amplitude level (f _{1 in} FIG. 4), and thereafter detects the frequency. Coordinate detection is performed based on the frequency.

As can be easily understood from this, the pen 1
Frequency f output from₁ The amplitude level of the electromagnetic wave
The voltage induced by the electromagnetic waves on the grid 11 is an external noise.
Of the voltage induced by the
Other frequency (f in FIG. 4) _Two ) Induced components
Must be set to always exceed.

This embodiment is effective when it is desired to secure an appropriate signal-to-noise ratio when there is a narrow-band and large-amplitude noise such as noise generated by an inverter or a DC / DC converter near the frequency band to be used. is there. Further, as described above, the amplitude of the output side of the output coil or the like only needs to exceed the maximum value of the noise levels of a plurality of predetermined frequency components (Sf ₁ / N in FIG. 4).
may be a f _2> 1), in comparison with the first embodiment can be kept small amplitude of the output side, it is effective in terms of reduced power consumption.

Embodiment 3 FIG. 5 shows a third embodiment of the present invention. In the second embodiment, the frequency is selected from among a plurality of discrete frequencies.
Oscillation frequency is set to a predetermined frequency range (Fig. 5
If f ₁ ~f ₂₎ is continuously changed (scanned) in the most noise level low frequencies (in the case of FIG. 5 f _opt) VC of
The frequency of O12 is selected. This embodiment operates in the same manner as the second embodiment except that the frequency oscillated from the coordinate pointing device is selected from a continuous range.

This embodiment is effective when the external noise has a high level over a considerably wide band and its frequency spectrum has large irregularities.

[Embodiment 4] FIG. 6 shows a fourth embodiment of the present invention.

In the above-described embodiment, the output coil and the detection coil are separately provided. However, in this embodiment, the functions of the output coil and the detection coil are integrated by using the three-terminal coil 16. ing. This allows
The pen 1 can be reduced in size and weight.

[Embodiment 5] FIG. 7 is a diagram showing an operation example of a fifth embodiment of the present invention. The configuration of the apparatus of this embodiment is similar to that of the first or fourth embodiment.

In each of the above embodiments, the output coil 2
Although the detection coil 3 is used to detect external noise when the output from the
This is an example in which the output state is fed back to the amplitude control of the output of the excitation unit 4.

That is, an electromagnetic wave oscillated from the output coil 2 is detected by the detection coil 3 and the excitation
To control the amplitude of the signal to be supplied to the output coil 2. FIG.
If the amplitude level of the signal output from the BPF 5 decreases, the output of the excitation unit 4 increases and the pen 1
, The output signal level can be raised and always kept at a constant level.

[Embodiment 6] In each of the above embodiments, the coordinate input system using an electromagnetic wave has been mainly described. However, other systems such as an electrostatic coupling system and a system using ultrasonic waves may be used. Can be realized.

For example, a coordinate input device using ultrasonic waves is shown in FIG. In the drawing, a vibrator 4 is driven by a vibrator driving circuit 2 of a vibrating pen 3, and an ultrasonic vibration is emitted from a cone 5 at the tip thereof. In addition, the receiving side replaces the grid for receiving the electromagnetic waves with a vibration transmission plate 8 such as an acrylic plate that transmits the vibration transmitted from the pen 3 and a sensor 6 such as a piezoelectric element that converts the vibration transmitted thereto into an electric signal. Multiple),
A signal waveform detection circuit 9 for detecting an output signal of the sensor 6, a display 11 for displaying an input coordinate position and the like, and a display drive circuit 10 for driving the same, and control them collectively to perform calculations such as calculation of a coordinate position. And an arithmetic control circuit 1 for performing the operation. On the receiving side, the delay time from the driving of the transducer driving circuit 2 to the detection of the vibration by the signal waveform detection circuit 9 is measured, the distance from each sensor to the vibration source is calculated from the value, and the calculation is performed based on the calculated distance. The control circuit 1 geometrically calculates a coordinate position.

Even in such a coordinate input device utilizing ultrasonic vibration, functions equivalent to those of the first to fourth embodiments can be provided. For example, a signal detected by the signal waveform detection circuit 9 in a state where the vibrator drive circuit 2 is not driven is regarded as noise, and when noise is detected, the level of vibration generated from the pen 3 is increased. Without directly inputting the output signal of the sensor 6 to the signal waveform detection circuit 9,
If the signal is input to the signal waveform detection circuit 9 via a GC (not shown), the detected noise level can be reduced.

When a coordinate is designated, the vibration pen 3 is used.
Is pressed against the plate 8, the sound pressure level generated from the tip of the pen 3 may be affected, or the output level may fluctuate due to fluctuations in the power supply voltage. Fluctuations in the output level from the pen 3 can also be corrected. For example, a sensor for detecting vibration of the cone 5 or the vibrator 4 is provided in the pen 3, and the vibration is input to the arithmetic and control circuit 1 and output from the vibrator drive circuit 2 in accordance with the fluctuation of the input signal level. The signal output for driving the vibrator 4 is controlled. By doing so, a constant level of vibration is always applied to the vibration transmission plate 8.

As described above, the coordinate input device described above can (1) greatly improve the signal-to-noise ratio while minimizing the increase in power consumption even when external noise occurs. It is possible to minimize the deterioration of the accuracy responsiveness.

(2) It is possible to detect and correct a drop in sound pressure due to pressing of the speaker for generating an ultrasonic wave or a drop in output level due to a change in power supply voltage, etc., thereby always obtaining stable coordinate input performance. it can.

(3) There is no need to particularly connect the pen cursor or the like to the grid or the like by a wire, and the effect of improving the performance of a so-called "cordless digitizer" can be obtained.

The present invention may be applied to a system composed of a plurality of devices or an apparatus composed of one device. Needless to say, the present invention can be applied to a case where the present invention is achieved by supplying a program to a system or an apparatus.

[0043]

As described above, the coordinate input device described above can perform highly accurate and stable coordinate input.
In particular, even when external noise is generated, the signal-to-noise ratio can be greatly improved while minimizing the increase in power consumption, and deterioration in precision responsiveness can be minimized.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a coordinate input device according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating the operation of the first embodiment.

FIG. 3 is a diagram illustrating a configuration of a coordinate input device according to a second embodiment.

FIG. 4 is a diagram illustrating the operation of the second embodiment.

FIG. 5 is a diagram illustrating an operation of a third embodiment.

FIG. 6 is a diagram illustrating a configuration of a coordinate input device according to a fourth embodiment.

FIG. 7 is a diagram illustrating the operation of the fifth embodiment.

FIG. 8 is a diagram showing a configuration of a conventional coordinate input indicator.

FIG. 9 is a diagram showing a detection output example of a signal input by a pointing device in a conventional coordinate input device.

FIG. 10 is a diagram illustrating a configuration example of a conventional coordinate input device.

FIG. 11 is a diagram illustrating an operation example of a conventional coordinate input device.

FIG. 12 is an explanatory diagram of calculating an estimated coordinate position.

FIG. 13 is a diagram illustrating a relationship between an S / N ratio on a grid and a coordinate estimation error.

FIG. 14 is a diagram illustrating a configuration of a coordinate input device using ultrasonic waves according to a sixth embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Coordinate pointing pen housing, 2 ... Output coil, 3 ... Detection coil, 4 ... Exciting part, 5 ... Band pass filter, 6 ... D / A converter, 7 ... Detector, 8 ... A / D converter, 9: control unit, 10: power supply, 12, 13: VCO, 14: low-pass filter, 15: multiplication circuit, 16: coil, 17: multiplexer, 18: amplifier with automatic gain adjustment function, 19: reception side control unit, 20 ... Amplifier, 21 ... VCO3, 22 ... Low-pass filter.

Claims (3)

(57) [Claims] 1. A coordinate input device comprising: a coordinate indicating means for outputting a signal; and a main body for detecting a signal output from the coordinate indicating means and determining a coordinate position specified by the indicating means. Transmitting means for transmitting a signal of a variable frequency, receiving means for receiving a signal of a variable frequency, means for changing the frequency of a signal received by the receiving means, received by the receiving means, Selecting means for selecting a frequency having the lowest signal level among signals from signal sources other than the transmitting means, wherein the frequency selected by the selecting means is used as the transmitting frequency of the transmitting means. Input device. 2. The apparatus according to claim 1, wherein the main unit includes a receiving unit that receives a signal of a variable frequency, a unit that changes a frequency of the signal received by the receiving unit, and a frequency having a highest signal level among the signals received by the receiving unit. and selecting means for selecting the coordinate input device according to claim 1, characterized in that the frequency selected by said selection means and receiving frequency of the receiving means. Wherein the signal is the coordinate input device according to claim 1 or 2, wherein the is an electromagnetic wave.