JPH02130617A - Coordinate input device - Google Patents

Abstract

PURPOSE:To stable detect the position of coordinates with high accuracy by setting the amplification factor of an electric signal, which is outputted from an oscillation sensor, and the voltage level of a driving signal, which is impressed to the oscillation sensor, to a specified minimum detecting signal level. CONSTITUTION:A user has an oscillating pen 3 in a hand and inputs the coordinates in the position on an oscillation transmitting board 8. The oscillation transmitting board 8 transmits the ultrasonic oscillation, which is received from the oscillating pen 3, to oscillation sensors 6a-6c. Signals to be detected by the sensors 6a-6c are respectively given to a signal waveform detecting circuit 9 and an oscillation transmitting time to the sensors 6a-6c is obtained. An arithmetic and control circuit 1 detects the position of the oscillating pen 3 from the oscillation transmitting time to the sensors 6a-6c. At such a time, the amplification factor of the electric signal, which is outputted from the sensors 6a-6c, and the voltage level of the driving signal to be impressed to the sensors 6a-6c are set according to the minimum detecting signal level based on the resolution of a device and the frequency of the detecting signal. Then, the position of the coordinates can be stably detected with the high accuracy.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention detects vibrations generated from a vibrator in a coordinate input device, particularly a vibrating pen, using a plurality of vibration sensors provided on a vibration transmission plate. The present invention relates to a coordinate input device that detects the position of the vibrating pen from the vibration transmission time to the sensor.

[Conventional technology] A brief explanation of this method is as follows.

An input pen is brought into contact with a vibration transmission plate (forming the coordinate input surface of the tablet), and vibrations generated from the input pen are detected by a plurality of vibration sensors provided at predetermined positions on the vibration transmission plate. Then, the designated coordinate position is calculated by measuring the vibration delay time for each vibration sensor.

[Problems to be Solved by the Invention] By the way, the minimum amplitude of a detection signal detected by a vibration sensor and used for subsequent processing has usually been determined through experiments.

Specifically, we use a pen pressure detection device, etc. to obtain a good writing feeling, and in that environment, we actually put the pen in contact with the vibration transmission plate and use the vibration value when it reaches a steady state as the standard. The minimum amplitude value is often determined based on the

However, when changing the thickness, material, etc. of the vibration transmission plate, or changing the size of the vibration transmission plate itself, it is necessary to conduct the above-mentioned experiment each time to determine the minimum amplitude of the detection signal. It must be said that there is a problem from the viewpoint of work efficiency in the manufacturing process.

The present invention was made in view of this problem, and it quantitatively determines the amplification factor of the electrical signal detected by the vibrator or vibration sensor in the vibrating pen, thereby stably and highly accurately determining the coordinates. It is an object of the present invention to provide a coordinate input device that makes it possible to detect a position.

[Means for Solving the Problem] and [Operation] In order to solve this problem, the present invention has the configuration shown below.

That is, in the coordinate input device that detects vibrations generated from a vibrator in a vibrating pen using a plurality of vibration sensors provided on a vibration transmission plate, and detects the position of the vibrating pen from the vibration transmission time to each vibration sensor, The amplification factor of the electric signal output from the vibration sensor and the voltage level of the drive signal applied to the vibration sensor were set by the minimum detection signal level based on the resolution of the device and the frequency of the detection signal detected from the vibration sensor. .

[Embodiments] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Description of Device Configuration (Fig. 1)> Fig. 1 shows the structure of the coordinate input device in this embodiment.

In the figure, l is an arithmetic control circuit that controls the entire device and calculates the coordinate position. Reference numeral 2 denotes a vibrator drive circuit, which generates a drive signal for vibrating the pen tip of the vibrating pen 3. Reference numeral 8 denotes a vibration transmission plate made of a transparent member such as an acrylic or glass plate, and coordinate input using the vibrating pen 3 is performed by touching the top of the vibration transmission plate 8. An anti-reflection material 7 is provided on the outer periphery of the vibration transmission plate 8 to prevent (reduce) the reflected vibration from returning to the center, and a piezoelectric element or the like is placed at the boundary of the anti-reflection material 7 to convert the mechanical vibration into an electrical signal. Vibration sensors 6a to 6C are fixed at the positions shown in the figure.

Reference numeral 9 denotes a signal waveform detection circuit that outputs a signal indicating that vibration has been detected by each of the vibration sensors 6a to 6c to the arithmetic control circuit 1.

Reference numeral 11 denotes a display capable of displaying dots, such as a CRT (or liquid crystal display), and is arranged behind the vibration transmission plate 8. Then, by driving the display drive circuit 10, a dot is displayed at the position traced by the vibrating vane 3, and it is possible to see it through the vibration transmitting plate 8 (as it is made of a transparent member). . That is, the display 11 corresponding to the detected coordinates of the vibrating pen 3
A dot is displayed at the upper position, and an image composed of elements such as points and lines inputted by the vibrating ben 3 appears after the trajectory of the vibrating ben as if written on paper.

Further, according to such a configuration, the menu is displayed on the display 11, and input methods such as having the vibrating ben 3 select the item or displaying a prompt and touching the vibrating ben 3 at a predetermined position can be performed. It can also be used.

FIG. 2 shows the structure (cross-sectional view) of the vibrating vent 3 according to the embodiment.

The vibrating pen 3 includes a vibrator (made of a piezoelectric element) 4 that vibrates based on a signal supplied by a vibrator drive circuit 2, and a horn for transmitting ultrasonic vibrations generated from the vibrator 4 to a vibration transmission plate 8. A portion (pen nib) 5 is provided.

Note that the drive signal for the vibrator 4 is a low-level pulse signal supplied from the arithmetic control circuit 1, which is amplified by a predetermined gain by a vibrator drive circuit 2 capable of low impedance driving, and then applied to the vibrator 4. be done.

Here, the vibration frequency of the vibrator 4 is selected to a value that can generate plate waves on the vibration transmission plate 8 made of acrylic, glass, or the like. Further, when driving the vibrator, a vibration mode is selected in which the vibrator 4 mainly vibrates in the vertical direction in FIG. 2 with respect to the vibration transmission plate 8. Furthermore, the frequency of the drive signal applied from the vibrator drive circuit 2 is set to the resonance frequency of the vibrator 4 to obtain efficient vibration.

The elastic waves transmitted to the vibration transmission plate 8 as described above are plate waves, and compared to surface waves, scratches on the surface of the vibration transmission plate, etc.
It has the advantage of being less affected by obstacles.

Explanation of the arithmetic control circuit (Fig. 3)> In the above-described configuration, the arithmetic control circuit 1 operates at a predetermined period (Figure 3).
For example, every SMS), the transducer drive circuit 2 outputs a signal (a pulse signal having a repetition period of the resonant frequency of the transducer 4) to drive the transducer 4 in the vibrator 3, and also outputs a signal (a pulse signal having a repetition period of the resonant frequency of the transducer 4) to the transducer drive circuit 2, and also outputs a signal (a pulse signal having a repetition period of the resonant frequency of the transducer 4) to the transducer drive circuit 2. (configured) starts timing. The vibrations generated by the vibration vent 3 arrive with a delay depending on the distance to the vibration sensors 6a to 6c. The vibration waveform detection circuit 9 includes each vibration sensor 6a to 6c.
The arithmetic control circuit 1 inputs this signal for each sensor and generates a signal indicating the timing of vibration arrival at each vibration sensor through waveform detection processing described later. Detection of the vibration arrival time up to 6c and calculate the coordinate position of the vibrating pen.

Then, the arithmetic control circuit 1 drives the display drive circuit 10 based on the calculated coordinate position information of the vibrating pen 3 to control the display operation of the display 11.

FIG. 3 shows the internal configuration of the arithmetic control circuit 1 in this embodiment, and each component and its operation outline will be explained below.

In the figure, 31 is a microcomputer that controls the arithmetic control circuit 1 and the entire coordinate input device, and includes internal counters,
ROM31 that stores operating procedures and correction tables to be described later
a, and RAM3 l used as a work area
It has a built-in b. 33 is a timer (consisting of a counter) that measures a reference clock selected from the required resolution, and is used to cause the vibrator drive circuit 2 to start driving the vibrator 4 in the vibrating vent 3. The time measurement is started by outputting a start signal. That is,
This synchronizes the start of time measurement and the timing of vibration generation.

The circuits that constitute the lot number components will be explained in order.

First, the microcomputer 31 outputs a reset signal to the timer 33, etc., and clears them once. Thereafter, a signal is output to the vibrator drive circuit 2 to drive the vibrator 4 in the vibrating vent 3.

Note that as a result of this, the timer 33 starts counting time.

In this way, the vibrations generated by the vibration oven 3 reach each of the vibration sensors 6a to 6c after a delay time corresponding to each distance has elapsed. Although the details will be described later, the timing signals of the vibration arrival of each vibration sensor 6a to 6c obtained via the signal waveform detection circuit 9 are inputted to the latch circuits 34a to 34c via the detection signal input port 35. Ru. The latch circuits 348 to 34c correspond to the vibration sensors 6a to 6c, and when each receives a timing signal that is a signal from the corresponding vibration sensor, it latches the time value of the timer 33 at that time. When the determination circuit 36 determines that all detection signals have been received, it outputs a signal to that effect to the microcomputer 31. When the microcomputer 31 receives this signal from the determination circuit 36, it reads the vibration arrival time from the latch circuits 34a to 34c to each vibration sensor, performs a predetermined calculation, and calculates the coordinates of the vibration ben 3 on the vibration transmission plate 8. Calculate the position. Then, the display drive circuit 1 is connected via the I10 boat 37.
By outputting the coordinate position information calculated as 0, for example, a dot or the like is displayed at the corresponding position on the display.

If the signal indicating the arrival of the signal is not inputted from the determination circuit 36 even after the maximum delay time has passed, it is assumed that the coordinates have not been inputted by the vibrating vent 3, and the coordinate position is not calculated, and the calculation after the previous reset process is performed. Execute processing.

Explanation of vibration propagation time detection (Figures 4 and 5)> Below,
The principle of measuring the vibration arrival time to the vibration sensor will be explained.

FIG. 4 shows the detected waveform input to the signal waveform detection circuit 9,
FIG. 3 is a diagram for explaining a vibration transmission time measurement process based on this. Note that although the vibration sensor 6a will be explained below, the same applies to the other vibration sensors 6b and 6c.

It has already been explained that the measurement of the vibration transmission time to the vibration sensor 6a starts with the output of the start signal to the vibrator drive circuit 2.

At this time, a drive signal 41 is applied from the vibrator drive circuit 2 to the vibrator 4.

The ultrasonic vibrations transmitted from the vibration vent 3 to the vibration transmission plate 8 in synchronization with this signal are detected by the vibration sensor 6a after traveling for a time tg corresponding to the distance to the vibration sensor 6a. A signal indicated by 42 in the figure indicates a signal waveform detected by the vibration sensor 6a.

By the way, the vibration used in the embodiment is a plate wave, and therefore, the relationship between the envelope 421 and the phase 422 of the detected waveform with respect to the propagation distance within the vibration transmission plate 8 is that the relationship between the envelope 421 and the phase 422 of the detected waveform is It changes accordingly.

Here, the advancing speed of the envelope 421, that is, the group velocity Vg, and the phase velocity of the phase 422 are Vp. The distance between the vibration sensor 6a and the vibration sensor 3 can be detected from the difference between the group velocity Vg and the phase velocity Vp.

First, focusing only on the envelope 421, its speed is Vg, and when a point on a certain waveform, for example a peak, is detected as in the signal 43 shown in the figure, the distance between the vibrating pen 3 and the vibration sensor 6a is d is the vibration transmission time tg, and d=Vg-tg...■
Although this formula relates to one of the vibration sensors 6a,
The distances between the other two vibration sensors 6b and 6c and the vibration pen 3 are also expressed by the same principle using the same formula.

Furthermore, in order to determine coordinate values with higher precision, processing based on phase signal detection is performed.

The time from a specific detection point of the phase waveform signal 422, for example, vibration application to a zero crossing point after passing the peak, is tp(
A window signal 44 of a predetermined width is generated using the signal 43, and a phase signal 42 is generated.
2), the distance d between the vibration sensor and the vibration pen is d=n·λp+VpIItl) ””■. Here, λp is the wavelength of the elastic wave, and n is an integer. From the above equations ■ and 0, the above integer n is n= [(Vg-t
g-Vp-tp)/λp+1/N]...
■ It is expressed as.

Here, N is a real number other than O, and an appropriate value is used.

For example, if N=2, n can be determined if it is within ±1/2 wavelength. Set n calculated as above to 0
By substituting into the formula, the vibration vent 3 and the vibration sensor 6a
The distance between the vibration ben 3 and the vibration sensors 6b, 6c
The distance between can be measured accurately.

The signals 43 and 45 for measuring the two vibration propagation times tg and tp mentioned above are generated by the signal waveform detection circuit 9, and this signal waveform detection circuit 9 is configured as shown in FIG.

In FIG. 5, the output signal of the vibration sensor 6a is amplified to a predetermined level by a preamplifier circuit 51. In FIG. The amplified signal is input to the envelope detection circuit 52, and only the envelope of the detection signal is extracted. The timing of the peak of the extracted envelope is detected by the envelope peak detection circuit 53. The peak detection signal is formed into a signal Tg (signal 53), which is an envelope delay time detection signal of a predetermined waveform, by a Tg signal detection circuit 54 composed of a mono multivibrator or the like, and is input to the arithmetic control circuit 1.

Moreover, this signal Tg is applied to the monostable multivibrator 55 (
After passing through a comparator level supply circuit 56 (generating a signal 44 with a predetermined pulse width) and a comparator level supply circuit 56 (generating a predetermined threshold value), it is supplied to a comparator Tp detection circuit 58 for comparison with the original signal delayed by a delay time adjustment circuit 57. . This comparator Tp detection circuit 58 detects the phase delay time signal T.
p is supplied to the arithmetic control circuit l.

The circuit explained above is for the vibration sensor 6a, and the same circuit is provided for the other vibration sensors 6b and 6c.

Therefore, if the number of sensors is generalized to h, then h detection signals of each of the envelope delay times Tgl to h and the phase delay time Tpl-h are input to the arithmetic control circuit 1.

Then, in the arithmetic control circuit 1, the above Tgl~h, Tpl
-h signal is input from the input port 35, and the time value (count value) of the timer 33 is taken into the latch circuits 34a to 34c as each timing trigger.The timer 33 is started in synchronization with the driving of the vibration ben. Therefore, the latch circuits 34 to 34c latch data indicating the respective delay times of the envelope and phase of each of the vibration sensors 6a to 6C.

Explanation of Coordinate Position Calculation (FIG. 6)> Next, the principle of actually detecting the coordinate position on the vibration transmission plate 8 by the vibrator 3 will be explained.

Now, the coordinates of the vibration sensor 6a on the vibration transmission plate 8 are S,
(O, O), that is, the origin, and the vibration sensors 6b, 6
Let the coordinate position of c be S b (X, O), 5-(0, Y), and let the coordinate position of the vibrating ben be P (x, y).

Based on the principle explained earlier, if the distances between the vibration vent 3 and each of the vibration sensors 6a to 6C are d and ~de, respectively, then the P(x, y) to be obtained is calculated from the following formula using the Pythagorean theorem. It becomes like this.

Here, "X" and "Y" are the horizontal and vertical distances of the vibration sensors 6b and 6c from the vibration sensor 6a.

In the manner described above, the position coordinates of the vibrating ben 3 can be detected in real time.

Description of Level Determination of Detection Signal (FIG. 7) Next, a method of determining the level of the detection signal (corresponding to signal 42 in FIG. 4) in the embodiment will be described with reference to FIG.

Let's assume a coordinate input device that has the following conditions.

・Frequency of detection signal = 400 KHz ・Resolution = 0.1 mm ・Phase velocity V, = 2000 m/s Then, the minimum time of one wavelength of the reference clock counted by the timer 33 in the arithmetic control circuit 1 is v=f・λ From the relationship, 1/f=λ/v=0.1 (mm)/2000
(m/s)=0. IX 10-'/2000=5
It becomes 0nsec.

Similarly, the time for one wavelength of the detection signal is 1/(4
00X 10”) = 25u sec.

Here, if the detection signal is a sine wave with a single frequency and its amplitude is "1", the timer 3 near the zero cross
The maximum amplitude in one count of 3 is in the state shown in FIG.

Therefore, the maximum level L within one force count width is L = 5i
n(180-(25x 10-'/25x 10-'
)) 0.03. In other words, the comparator Tp in FIG.
The detection circuit 58 must determine zero crossing by this level.

For example, assume that the noise level of the detection signal is 10 mVp-p [peak-to-peak], and a margin of twice is taken from the level of one count of zero crossing.

If the detection signal level at this time is a, then aXo, 03
/2=5mVo-p,', a=0.33Vo-p. This value is then set as the minimum amplitude level (peak-to-peak) of the waveform for Tp detection.

By the way, this value does not take into account the detection wave having a single frequency and the time delay of each circuit element. An actual waveform not only contains not only a single component frequency but also a considerable amount of high frequency, and also has a time delay in TTL and the like. Therefore, instead of the above-mentioned 2x margin, a 3x or more 5x margin should be taken.

Incidentally, when taking a margin of 3 times, a is “0.5Vo
-p, and when it is 5 times that, “0.83Vo-p
becomes.

In other words, the level of the resolution limit near the zero crossing of the detection signal is calculated, and the minimum level of the detection signal is determined by taking a margin from this. Note that this level is the farthest distance r @jlX from the sensor of interest (for example, sensor 6a)
s, that is, it occurs at the position where the vibration is most attenuated.

Next, the voltage level of each block is determined based on the amplitude a at rl, , obtained in this way.

Now, KP%, which is the electromechanical coupling coefficient of PZT of the vibrating pen 3, the amplification factor of the horn section 5, βH1, the attenuation formula at the distance r on the vibration transmission plate 8, is (1/r)・A-e′″2, and the vibration It is assumed that the amplification factor of the preamplifier circuit 51 is expressed by βA. However, A is the initial amplitude, a
is the damping constant.

At this time, the driving voltage Vo applied to the PZT (vibrator 4) of the vibrating pen 3 may be determined by the following.

Of course, even if the pen drive voltage VD and the amplification factor β of the preamplifier circuit 51 are determined experimentally by placing the vibrating pen 3 at the farthest distance and setting the minimum amplitude level to a, the above equation Needless to say, this is the same as what was sought from .

As explained above, according to this embodiment, the amplification factor of the electrical signal detected by the vibration sensor and the voltage of the drive signal applied to the vibrator in the vibrating pen are calculated from the resolution, detection signal frequency, etc. Therefore, it is possible to quantitatively calculate each of these factors due to design changes. Therefore, the thickness of the vibrating voltage plate, etc.
Regardless of the size or even changes in material, it is possible to always perform stable and highly accurate coordinate detection.

In the embodiment, the drive voltage of the vibrating pen 3 and the amplification factor β of the preamplifier circuit 51 were determined based on the minimum amplitude level of the detection signal, but the pen pressure detection level was determined based on this minimum amplitude level. It is also possible to decide.

For example, a comparator with a threshold set at level a is newly provided as a pen pressure detection circuit. Alternatively, consider setting a margin for the minimum amplitude level a, and setting a high threshold for people who use strong pen pressure, a medium threshold for people with normal pen pressure, and a low threshold for people who use weak pressure. It will be done.

[Effects of the Invention] As explained above, according to the present invention, the amplification factor of the electrical signal detected by the vibrator or vibration sensor in the vibrating pen can be determined quantitatively, so it can be stably and accurately determined. It becomes possible to detect the coordinate position.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the coordinate input device of this embodiment, and FIG. 2 is a diagram showing the structure of a vibrating pen. Fig. 3 is a diagram showing the internal configuration of the arithmetic control circuit in the embodiment, Fig. 4 is a diagram for explaining distance measurement between the vibrating pen and the vibration sensor, and Fig. 5 is the signal waveform detection circuit in the embodiment. FIG. 6 is a diagram for explaining the principle of coordinate position calculation. FIG. 7 is a diagram for explaining the method for determining the minimum amplitude in the embodiment. In the figure, l: arithmetic control circuit, 2: vibrator drive circuit, 3: vibrating pen, 4: vibrator, 6a to 6C...
・Vibration sensor, 7... Vibration isolating material, 8... Vibration transmission plate,
9... Signal waveform detection circuit, 10... Display drive circuit, il... Display, 12.13-... Temperature sensor, 13... Buzzer 31... Microcomputer, 33... Timer, 34a to 34c...Latch circuit, 35...Detection signal input port, 36...
Judgment circuit, 37... I10 board, 51... Preamplifier circuit, 52... Envelope detection circuit, 53...
Envelope peak detection circuit, 54... Tg detection circuit, 55... Monostable multivibrator, 56... Comparator level supply circuit, 57... Delay time adjustment circuit, 58... Comparator Tp detection circuit. be. -,,; 2. 2 Part', 2 Sayo-9 Figure 4 (Shoutaguchi Road) 5th Ward Figure 6

Claims (1)

[Claims] In a coordinate input device that detects vibrations generated from a vibrator in a vibrating pen using a plurality of vibration sensors provided on a vibration transmission plate, and detects the position of the vibrating pen from the vibration transmission time to each vibration sensor, the vibration sensor The amplification factor of the electrical signal output from the vibration sensor and the voltage level of the drive signal applied to the vibration sensor are set by the minimum detection signal level based on the resolution of the device and the frequency of the detection signal detected from the vibration sensor. Characteristic coordinate input device.