JPH0196716A - Coordinate input device - Google Patents

Abstract

PURPOSE:To always ensure the accurate detection of vibrations with a coordinate input device of a vibration pen input type by analyzing the vibration detecting waveform and changing the driving frequency of a vibration pen. CONSTITUTION:The vibrations of a vibration pen are detected by a vibration sensor 116 (at plural points) and an address of the pen is decided from the intensity, the frequency phase, etc., of the detection signal of the sensor 116 measured at each point. In such a constitution, the output of the sensor 116 is used for address arithmetic and at the same time the vibration detecting waveform is analyzed by a vibration waveform detecting circuit 3. Then the input vibration frequency of the vibration pen is controlled based on the result of analysis of the circuit 3. Thus it is possible to always ensure the accurate input of coordinates based on the detected vibrations regardless of the state change of the vibrator of the vibration pen, the change of the transmission characteristics of a vibration transmitting plate 117, the change of the writing pressure, etc.

Description

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

[Prior Art] Conventionally, human coordinate devices using various input pens and tablets have been known as devices for inputting handwritten characters, figures, etc. into processing devices such as computers. Among them, the sixth coordinate input device uses ultrasonic vibrations and detects the propagation time of ultrasonic vibrations transmitted from the input pen to the 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 vibration sensor made of a piezoelectric element 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.

Next, in FIG. 7, reference numeral 149 is a pen drive waveform. Reference numeral 150 indicates a detected waveform in the sensor, which is amplified by a predetermined gain by the preamplifier circuits 130 to 132 shown in FIG. 6 for each sensor, and then sent to the vibration waveform detection circuit 133.1.
34.135. In the vibration waveform detection circuit, the seventh
The envelope ferry tS3 in the figure is extracted, the peak point 151 of the envelope and the zero-crossing point 152 of the first detected waveform after the peak point are detected, and the detection signals are input to the latch circuits 136, 137, and 138 in FIG. The latch circuit latches the timing result of the timing counter 139 started in synchronization with the drive signal using the detection signal,
The phase delay time tp and group delay time tg shown in FIG. 7 are output to the control device 140. In the control device, the tp%
Based on tg, the pen input position P(x
%y).

FIG. 8 schematically shows the arrangement of the vibration sensor 144 shown in FIG. 6. In FIG. 8, vibration sensor positions SO and SL
, Sl distance rx%ry.

5O1S1, the distance between Sl and P (x%y) is dO.

dl, d2, and the previously measured phase velocity of the elastic wave are given as Vp. Here, τO1τ1 and τ2 are expressed by the above-mentioned tp and the frequency of the elastic wave measured in advance as f (subscripts 1-0 to 2 indicate sensors).

n in the above equation is an integer given by the group velocity Vg of the elastic wave measured in advance and the above tg (INT[] indicates integerization)
.

Therefore, in the past, the coordinate values were calculated by creating the envelope waveform 153 shown in FIG. 7 and measuring tg1%tpt.

[Problems to be Solved by the Invention] However, in the conventional example described above, in order to detect the peak of the envelope in FIG. Since the envelope waveform was obtained and the peak point detection timing was set at the time when the envelope waveform exceeded a certain predetermined level, changes in the resonance point of the pen's vibrator,
Alternatively, if the amplitude and width of the detected waveform cannot be obtained sufficiently due to the condition of the vibration transmission plate, the phase delay time tp cannot be measured, which causes a decrease in the accuracy of coordinate detection.

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

[Means for solving problems]

In order to solve the above problems, in the present invention, vibrations input from a vibrating pen are detected by a plurality of vibration sensors provided on a vibration transmitting plate, and the coordinates of the vibrating pen on the vibration transmitting plate are detected. The coordinate input device employs a configuration including means for detecting the waveform of a vibration detection signal from the vibration sensor and means for controlling the frequency of input vibration of the vibrating pen based on the detection result output by the waveform detection means. did.

[Function] According to the above configuration, by changing the drive frequency of the vibrating pen according to the waveform result of the detection signal from the vibration sensor, the state of the vibrator of the pen changes, the transmission characteristic of the vibration transmission plate changes, Coordinate input based on accurate vibration detection is possible at all times, regardless of changes in pen pressure.

[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 consisting of a vibration transmitting plate 11.

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 pen 114 on the vibration transmission plate 117 are detected by measuring the transmission time of the ultrasonic vibration transmitted from the vibration pen 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.

Photographing ben 1 that transmits ultrasonic vibration to the vibration transmission plate 117
14 has a vibrator 113 made of a piezoelectric element or the like inside, and transmits the ultrasonic vibration generated by the vibrator 113 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 a pen drive signal from the control circuit as a trigger, and is supplied to a predetermined level by the vibrator drive circuit 111 capable of low impedance driving. After being amplified with a gain of , 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 output to the 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 constructed 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 manually input to the envelope beak detection circuit in order to obtain a signal necessary for manual coordinate detection. The peak detection signal detected by the envelope peak detection circuit is formed into an envelope delay time detection signal Tg having a predetermined waveform by a signal detection circuit 203 composed of a mono-multivibrator, etc., 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 the original signal delayed by this Tg multiplied signal delay time adjustment circuit 200, and a phase delay time detection signal Tp is formed by the latch circuit 1.
06 is input.

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, the control device 110 determines coordinate values by the following calculation. Since the sensor arrangement is the same as in the previous embodiment, it will be explained below with reference to FIG.

In FIG. 8, the distance between sensor SO and Sl, 32 is rx,
The distance IIr between ry%So, Sl, S2 and P (x, y) is given by dOldl, d2, and the previously measured phase velocity of the elastic wave is Vp, as described above. Here, τ0, τ1, τ2 are the tpt
, the frequency of the elastic wave measured in advance is rt (t-
o, t, 2). ni in the above equation is an integer given by the group velocity vg of the elastic wave measured in advance and the above tgi.

Here, if the amplitude of the envelope waveform reaches a predetermined value, the coordinate values can be calculated using the method explained above, but if the amplitude of the envelope is not sufficient, tg and tp cannot be determined. In the example,
The extracted envelope is further applied to the vibration period adjustment circuit 11.
2 and control the vibration frequency based on the detected envelope value.

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 is input to an A/D converter 300, converted to an 8-bit digital signal, and output to an input port of a CPU 301. The CPU is always in a state where it can check the numerical value of this input port. CPU301
RAM302 and ROM303 are connected to RO
RAM30 according to the microprogram in M303
Processing is performed using 2 as a work area.

A program as shown in FIG. 4 is written in the ROM 303. In step 5401, the CPU monitors the pen drive signal input from the control circuit 110, 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 54Q2; otherwise, the process proceeds to step 54Q2. returns to step 5401.

In step 5402, since vibration is transmitted from the pen and detected by the sensor, the A/D converter 300
Check the output and set it to a certain value, 80H in this example.
(Hexadecimal number; indicates digitized amplitude value) Check whether it is greater than or equal to (hexadecimal number; indicates the digitized amplitude value).

If it is 80H or more, the envelope has sufficient amplitude, so the process returns to step 5401. If it is less than 80H, the amplitude of the envelope is not sufficient, so the process moves to step 5403, inputs 0 to the variable A indicating the detected amplitude value, and moves on to step 5404.

In step 5404, the D/A converter 30 of FIG.
Output the value of variable A to 4. D/A converter 304
converts the value of the input variable A into an analog voltage and outputs it to the voltage controlled oscillator (VCO) 305. VCO305
Then, a pulse having a frequency corresponding to the input voltage is output 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, the process proceeds to step 5405, where it is determined whether the amplitude of the envelope is 80)1 or more based on the output of the A/D converter. If it is 80H or more here, step 5
The process returns to 401 and the series of processes ends. If the amplitude is still insufficient, the process proceeds to step 3406, where A+1 is substituted for A, and the process proceeds to step 5407.

In step 5407, it is checked whether A has become FFH (hexadecimal number), and if A has become FFH, all the frequencies to be investigated have been checked, so the process returns to the beginning and step 5401
Proceed to. If A has not reached FFH, step 540
4, and repeat the series of operations from steps 3404 to 5407.

By performing the above operations, it is possible to always obtain a sufficient amplitude of the envelope waveform. Even when the amplitude of the waveform cannot be obtained, the amplitude of the envelope waveform is increased by automatically changing the frequency to enable stable coordinate detection.

In the above embodiment, the vibration frequency given to the pen in FIG.
This was done by controlling the VCO 305 using the voltage output of the A converter 304, but as shown in FIG. The frequency is divided into a plurality of predetermined frequencies, one is selected by the signal selection circuit 503 based on a selection signal from the CPU, and is output to the vibrator drive circuit 111. Generally, VCOs are limited in frequency variation within a limited range, but according to the embodiment of the youngest son type, it is possible to select a relatively wide range of frequencies.

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, vibration input from a vibrating pen is detected by a plurality of vibration sensors, and transmitted to the vibration transmitting plate of the vibrating pen. A coordinate input device for detecting the coordinates of a vibration sensor, comprising means for detecting a waveform of a vibration detection signal from the vibration sensor, and means for controlling a frequency of input vibration of the vibrating pen based on a detection result outputted by the waveform detection means. By changing the drive 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, and It is possible to provide a coordinate input device that can always input coordinates based on accurate vibration detection, regardless of changes in pressure.

[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. Fig. 6 is a block diagram of a conventional ultrasonic coordinate human power device, Fig. 7 is a waveform diagram showing drive waveforms and detection waveforms, and Fig. 8 is an explanation showing the distance relationship between the pen and sensor. It is a diagram. 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;
A coordinate input device comprising: means for controlling the frequency of input vibration of the vibrating pen based on the detection result output by the waveform detecting means.