JPH01106129A - Coordinate input device - Google Patents

Abstract

PURPOSE:To realize the sure detection of coordinates with high stability by changing the vibration frequency of a vibration pen according to the waveform of a detection signal obtained by a vibration sensor to obtain the amplitude of a satisfactory envelope waveform. CONSTITUTION:The elastic waves produced in a vibration transmitting plate 117 by a vibrator 113 of a vibration pen 114 are detected by three vibration sensors 116. The waveforms detected by the sensors 116 are supplied to the vibration waveform detecting circuits 103-105. Then the time count value of a time counter 109 is taken into latch circuits 106-108 in the timing detected the vibration waveform detecting circuit. Thus the data showing the envelopes and the delay times of the sensors 116 are obtained and used for detection of the coordinate position of the pen 114 with calculation of a control circuit 110. While the vibration frequency of the vibrator 113 is changed by a vibration frequency adjusting circuit 112 in case the envelope amplitude of said detected waveform is small.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention detects vibrations input from a coordinate input device, particularly a vibrating pen, using a plurality of sensors provided on a vibration transmitting plate. The present invention relates to a coordinate input device that detects coordinates on the top.

[Prior Art] Coordinate input devices using various input pens and tablets have been known as devices for inputting handwritten characters, figures, etc. into a processing device such as a computer. Among them, as a coordinate input device that uses ultrasonic vibration, the seventh coordinate input device detects the propagation time of ultrasonic vibration transmitted from an input pen to a vibration transmission plate, and detects the coordinate position of the input pen. A configuration as shown in the figure has been devised.

The vibrating pen 143 is a pen for generating elastic waves in a vibration transmission plate 146 that transmits elastic waves, and has a vibration-generating piezoelectric element (vibrator) 142 inside. Also, code 14
1 is a drive circuit for this pen. Reference numeral 144 is a piezoelectric element (sensor) for detecting elastic waves transmitted through the vibration transmission plate 146. Reference numeral 145 is a vibration isolating material that prevents reflection at the end face of the vibration transmission plate 146.

It is the shape. Reference numeral 150 indicates a detected waveform in the sensor, which is amplified by a predetermined gain by the preamplifier circuits 130 to 132 in FIG. 7 for each sensor, and then sent to the vibration waveform detection circuit 1
33.134.135. The vibration waveform detection circuit extracts the envelope waveform 153 shown in FIG. 8, detects the peak point 151 of the envelope and the first zero-crossing point 152 of the detected waveform after the peak point, and sends the detection signal to the latch circuit 136 shown in FIG. Enter 137.138. The latch circuit latches the timing result of the timing counter 139 started in synchronization with the drive signal using the detection signal, and outputs it to the control device 140 as a phase delay time tp147 and a group delay time tg148 in FIG. The control device detects the coordinates of the pen input position P (x, y) by the following calculation based on the tp% tg.

In Fig. 9, the distances between the sensors So, sl, and s2 are rx
,ry% So, Sl, the distance between S2 and P(x,y) is d
Oldl, d2, and the previously measured phase velocity of the elastic wave are given as Vp. Here, τ01τ1 and τ2 are expressed by the above-mentioned tp and the frequency of the elastic wave measured in advance as f. The deviation of the above equation is an integer (converted to an integer in brackets) given by the group velocity Vg of the elastic wave measured in advance and the above tg.

Therefore, conventionally, the envelope waveform 153 shown in FIG. 8 was created and the coordinate values were calculated by measuring tg, i, and tpi.

[Problems to be Solved by the Invention] However, in the conventional example described above, in order to find the peak of the envelope in FIG. , because the peak point detection timing was set when a certain predetermined level was exceeded, a sufficient amplitude of the detected waveform could not be obtained due to changes in the resonance point of the pen's vibrator or the condition of the vibration transmission plate. In some cases, the phase delay time tp cannot be measured, which causes a decrease in the accuracy of coordinate detection.

Furthermore, if the envelope waveform detection level is set low in advance, the possibility of false detection increases due to external influences such as noise.

[Means for Solving the Problems] In order to solve the above-mentioned problems, in the present invention, a plurality of vibration sensors provided on a vibration transmission plate detect a photographic image input from a vibrating pen, and the vibrating pen A coordinate input device for detecting coordinates on a vibration transmission plate includes means for detecting the waveform of a vibration detection signal from the vibration sensor, and a means for detecting the waveform of the vibration detection signal of the vibration pen based on the detection result output by the waveform detection means. A means for controlling the frequency, and a constant used for coordinate calculation based on information regarding the vibration frequency changed by the frequency control means, and vibration on the vibration transmission plate of the changed constant and the vibration detected by the vibration sensor. A configuration is adopted that includes a means for detecting the coordinates of the point of vibration input by the vibrating pen from the transmission time information.

[Function] According to the above configuration, the driving frequency of the vibrating pen is changed according to the waveform result of the detection signal from the vibration sensor, and the constant for coordinate calculation is changed based on the changed frequency. Changes in the state of the pen's oscillator,
Coordinate input based on accurate vibration detection is possible at all times, regardless of changes in the transmission characteristics of the vibration transmission plate, changes in pen pressure, etc.

[Example] Hereinafter, the present invention will be described in detail based on the example shown in the drawings.

FIG. 1 shows the structure of an information input device employing the present invention. The information input device shown in FIG. 1 allows coordinates to be input using a vibrating pen 114 to an input tablet comprising a vibration transmitting plate 117.

In the figure, reference numeral 117 denotes a vibration transmission plate made of an acrylic glass plate or the like, which transmits vibrations transmitted from the vibration ben 114 to three vibration sensors 116 provided at its corners.

In this embodiment, the coordinates of the vibration ben 114 on the vibration transmission plate 117 are detected by measuring the transmission time of the ultrasonic vibration transmitted from the vibration ben 114 to the vibration sensor 116 via the vibration transmission plate 117.

The vibration transmission plate 117 has its peripheral portion covered with an anti-reflection material 115 made of silicone rubber or the like in order to prevent the vibration transmitted from the vibration ben 114 from being reflected at the peripheral portion and returning toward the central portion. Supported.

1. The vibration ben 114 that transmits ultrasonic vibration to the radial transmission plate 117 has a vibrator 113 made up of a piezoelectric element or the like inside.
The ultrasonic vibration generated by the vibrator 113 is transmitted to the vibration transmission plate 117 via a horn portion 118 having a sharp tip.

A vibrator 113 built into the vibrating ben 114 is driven by a vibrator drive circuit 111. The drive signal for the vibrator 113 is supplied as a low-level pulse signal of a predetermined frequency from the vibration frequency adjustment circuit 112 using the pen drive signal from the control circuit IIO as a trigger, and is supplied by the vibrator drive circuit 111 capable of low impedance driving. After being amplified with a predetermined gain, it is applied to the vibrator 113.

The electrical drive signal is converted into mechanical ultrasonic vibration by the vibrator 113 and transmitted to the vibration transmission plate 117 via the horn section 118.

The vibration frequency of the vibrator 113 is adjusted by the vibration frequency adjustment circuit 112 from among values that can generate plate waves in a vibration transmission plate such as acrylic glass, and is outputted as a vibrator drive circuit 111.

Further, when driving the vibrator, a vibration mode in which the vibrator 113 vibrates in a direction perpendicular to the vibration transmission plate 117 is selected.

As described above, the elastic waves transmitted to the vibration transmission plate 117 are plate waves, and compared to surface waves etc., the vibration transmission plate 117
It has the advantage of being less susceptible to surface scratches and obstacles.

In FIG. 1, the vibration sensor 116 provided at the corner of the vibration transmission plate is also constituted by a mechanical/electrical conversion element such as a piezoelectric element. The output signal of each of the three vibration sensors 116 is input to a preamplifier circuit 100.101.102,
After being amplified with a predetermined gain, each vibration waveform detection circuit 1
03.104.105.

The vibration waveform detection circuit is configured as shown in FIG.

FIG. 2 shows only one system of the vibration waveform detection circuit. In FIG. 2, the signal input from the preamplifier circuit 100 is input to the envelope detection circuit 205,
Only the envelope of the detection signal is detected. The extracted envelope must have sufficient amplitude and is input to the vibration frequency adjustment circuit 112 to determine this. On the other hand, if the amplitude of the envelope is sufficient, it is also input to the envelope peak detection circuit 204 in order to obtain a signal necessary for input coordinate detection. A signal detection circuit 203 composed of a mono multivibrator etc. is generated from the peak detection signal detected by the envelope peak detection circuit.
The envelope delay time detection signal Tg of a predetermined waveform is
is formed and input to the latch circuit 106.

Further, a phase delay time detection signal "rp" is formed by a comparator detection circuit 206 from the original signal delayed by the Tg flaw signal delay time adjustment circuit 200, and is input to the latch circuit 106.

Further, a phase delay time detection signal Tp is formed by a comparator detection circuit 206 from this Tg flaw signal and the original signal delayed by the delay time adjustment circuit 200, and is input to the latch circuit 106.

The circuit shown above is for one vibration sensor 116, and the same circuit is provided for each of the other sensors. If the number of sensors is generalized to h, then h detection signals of envelope delay times Tgl to h1 and phase delay times Tpl to h are input to the latch circuit 106, respectively.

Referring again to FIG. 1, the latch circuits 1 to 3 use the above-mentioned detection signals Tgl to Tgl to 3 and Tp1 to 3 as triggers to take in the time value of the clock circuit 109 into the latch circuits 1 to 3. Since the clock circuit 109 is started in synchronization with the pen drive signal of the vibrating pen, the latch circuits 1 to 3 receive data indicating the respective delay times of the envelope and phase of each sensor.

Using the above measured values, 1. The control device 110 determines the coordinate values by the following calculation.

In FIG. 9, the distance between the sensors so, sl, and s2 is r
x, ry, So, sl, s2 and P(X.

y) distance r is dOldl, d2, and the phase velocity of the elastic wave measured in advance is Vp, as described in (1) and (2) above.
It is given by the formula ie. Here, τ0, τ1, τ2 are the tpi
, and the frequency of the elastic wave previously measured as fl(
t=o, 1.2). ni in the above equation is the group velocity Vg of the elastic wave measured in advance and the above tg
It is an integer given by i.

Here, if the amplitude of the envelope waveform has reached a predetermined value, the coordinates and coordinate values can be calculated using the method explained above, but if the amplitude of the envelope is not sufficient, tg and tp can be calculated. I can't decide. Therefore, in this embodiment, the extracted envelope is further input to the vibration period adjustment circuit 112, and the vibration frequency is controlled based on this.

The vibration frequency adjustment circuit will be explained below based on FIGS. 3 and 4.

In FIG. 3, an envelope signal input from an envelope detection circuit 205 is input to an A/D converter 300, converted to an 8-bit digital signal, and sent to a CPU 3.
It is output to the input port of 01. The CPU 301 is in a state where it can always check the numerical value of this input port. C
A RAM 302 and a ROM 303 are connected to the PU 301, and processes are performed using the RAM 302 as a work area according to the microprogram in the ROM 303.

On the other hand, the CPU 301 has a D/A converter 304, a VCO
The drive frequency of the vibrator drive circuit 111 is controlled via the oscillator drive circuit 305 .

A program as shown in FIG. 4 is stored in the ROM 303. This control program will be explained below. First, in step T401, the CPU 301 controls the control circuit 1.
The pen drive signal input from 10 is monitored, and when the pen drive signal is input, it is assumed that vibration has been input from the pen to the vibration transmission plate - and the process proceeds to step T402; otherwise, the process returns to step T401.

In step T402, since vibration is transmitted from the pen and detected by the sensor, the A/D converter 300
It is checked whether the digital output value is greater than or equal to a certain predetermined value, in this embodiment 80H (hexadecimal). If it is 80H or more, the envelope has a sufficient amplitude, so the process returns to step T401. s O
If it is below H, the amplitude of the envelope is not sufficient, so
The process returns to step T403.

In step T403, 0 is assigned to variable A, and step T
Proceed to 404. In step T404, the D/A of FIG.
A variable A is applied to the converter 304 and the vibration frequency signal 119.
Output the value of .

The D/A converter 304 converts the value of the input variable A into an analog voltage and outputs the converted voltage to the voltage controlled oscillator (VCO) 305.
Output to. The VCO 305 outputs pulses with a frequency corresponding to the input voltage to the vibrator drive circuit 111.

Since the detection waveform detected by the sensor is a superposition of elastic waves applied to the vibration transmission plate by the drive signal, the amplitude of the envelope changes as the frequency changes.

Next, in step T405, it is checked whether the amplitude of the envelope has become 80H or more based on the output of the A/D converter. If it is 80H or more, the process returns to step T401 and ends the series of processes.

Here, the coordinate values are detected again by the control circuit 110, but since the frequency of vibration has changed from the initial state, this state is detected from the vibration frequency signal 119, and the vibration frequency of the elastic wave at that time is detected. fl(t=o, 1.2) is selected from among a plurality of pre-measured frequencies of elastic waves, and di ni τi == −=−+ t p ...(
7) Determine τi based on Vp f i and calculate coordinate values using equations (1), (2), and (6) above. Here, it is assumed that a plurality of imaging frequencies of elastic waves are measured in advance and stored in the information processing device.

If the amplitude is still not sufficient, the process proceeds to step T406, where A+1 is assigned (increased by 1) to the counter or register A, and the process proceeds to step T407. Step T407
Now check whether A has become FFH (hexadecimal number), and if A has become F
If it is FH, all the rice frequencies to be checked have been checked, so the process returns to the beginning and moves to step T401. A is FF)
(If it has not reached step T404, the series of operations from steps T404 to T5407 is repeated.

As described above, by selecting an appropriate vibration frequency based on the detection envelope, it is possible to always obtain a sufficient amplitude of the envelope waveform. Therefore, even if a sufficient envelope waveform cannot be obtained due to the state of the pen's vibrator, the state of the vibration transmission plate, etc., or the pen pressure during writing, the amplitude of the envelope waveform can be adjusted by automatically changing the frequency. to enable stable coordinate detection.

Moreover, since the most suitable elastic wave frequency for each elastic wave whose frequency is changed at the same time can be used as a constant for coordinate detection, more accurate coordinate detection is possible.

As another embodiment, when detecting the vibration frequency, as shown in FIG.
A possible method is to detect the actual vibration period, calculate the frequency from the period, and use it as a constant for the coordinate calculation. Fifth
The figure shows only one system of sensors. In this embodiment, the frequency for one system is used as a representative value and used as a constant for calculation.

FIG. 6 shows the configuration of the vibration period measuring circuit 120 of FIG. 5.

As shown in the figure, the input waveform input from the amplifier circuit 130 has a zero cross point detected by a comparator 601, and a counter 602 and a one-shot pulse generation circuit 60.
3 is input.

In the counter 601, the counter value is cleared by the zero cross signal, and the count is increased by a certain constant clock. On the other hand, one-shot pulse generation circuit 604
Then, when the zero-cross signal is input, a latch signal is immediately output to the latch circuit 604.

Since the latch signal is output before the counter 602 is cleared, the latch circuit 604 latches the time from zero-crossing point to zero-crossing point of the input waveform, that is, the vibration period. This period is read out by the control device, converted into a frequency, and used as a constant for coordinate calculation.

According to such a method, more accurate and highly accurate coordinate detection can be stably performed. Furthermore, by adding a vibration period measuring circuit to each sensor, highly accurate coordinate detection can be performed.

As described above, by changing the driving frequency of the vibrating pen according to the waveform result of the detection signal from the vibration sensor, changes in the state of the pen's vibrator, changes in the transmission characteristics of the vibration transmission plate, changes in pen pressure, etc. Even if sufficient amplitude of the envelope waveform cannot be obtained and coordinate detection becomes impossible, sufficient amplitude can be obtained by immediately changing the frequency of the pen drive signal, allowing highly stable and reliable coordinate detection. It has the effect of making it possible.

[Effects of the Invention] As is clear from the above description, according to the present invention, vibrations input from a vibrating pen are detected by a plurality of vibration sensors provided on the vibration transmitting plate, and vibrations inputted from the vibrating pen are detected by vibration sensors provided on the vibration transmitting plate of the vibrating pen. In the blade device, a means for detecting a waveform of a vibration detection signal from the vibration sensor, and a frequency of input vibration of the vibrating pen are controlled based on a detection result output from the waveform detection means. and a means for changing a constant used for coordinate calculation based on information regarding the vibration frequency changed by the frequency control means, and transmitting the vibration detected by the changed constant and the vibration sensor on the vibration transmission plate. Since the configuration includes means for detecting the coordinates of the vibration input point of the vibrating pen from time information, the driving frequency of the vibrating pen is changed based on the waveform result of the detection signal from the vibration sensor, and the changed frequency Since the coordinate calculation constants are changed based on A coordinate input device can be provided.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a coordinate input device according to the present invention, and FIG.
Figure 3 is a block diagram of the vibration waveform detection circuit, Figure 3 is a block diagram of the vibration frequency adjustment circuit, Figure 4 is a flowchart of the program for controlling the vibrator drive frequency, and Figure 5 is the vibration frequency selection circuit in another embodiment. Figure 6 is a block diagram of the vibration period measuring circuit shown in Figure 5, Figure 7 is a block diagram of a conventional ultrasonic coordinate input device, and Figure 8 shows drive waveforms and detection waveforms. The waveform diagram in FIG. 9 is an explanatory diagram showing the distance relationship between the pen and the sensor. 100-102... Preamplifier circuits 103-105... Vibration waveform detection circuits 106-108
... Latch circuit 109 ... Time counter 110 ... Control circuit 111 ... Vibrator drive circuit 112 ... Vibration frequency adjustment circuit 114 ... Vibration pen 116 ... Sensor 117 ...
・・Vibration transmission plate

Claims (1)

[Claims] In a coordinate input device that detects vibration input from a vibrating pen using a plurality of vibration sensors provided on a vibration transmission plate to detect coordinates of the vibration pen on the vibration transmission plate, the waveform of a vibration detection signal from the vibration sensor a means for detecting;
means for controlling the frequency of the input vibration of the vibrating pen based on the detection result output by the waveform detecting means, and changing constants used for coordinate calculation based on information regarding the vibration frequency changed by the frequency controlling means; A coordinate input device comprising means for detecting coordinates of a vibration input point by a vibrating pen from a constant determined by the vibration sensor and vibration transmission time information on the vibration transmission plate of the vibration detected by the vibration sensor.