JPH02130616A - Coordinate input device - Google Patents

Abstract

PURPOSE:To detect the exact position of coordinates by correcting an oscillation transmitting time to an attention oscillation sensor based on the change of a signal characteristic to be detected by the oscillation sensor and calculating the coordinate position of an oscillating pen based on the correspondent oscillation transmitting time. 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 from the oscillation transmitting time to the sensor to be obtained by the detecting circuit 9, the position of the oscillating pen 3 is detected in an arithmetic and control circuit 1. The detecting circuit 9 detects the change of the signal characteristic in the detected signal, for example, an envelope level and the detected change is sent to the circuit 1. The circuit 1 corrects the oscillation transmitting time to the attention sensor based on the detected result of the envelope level and detects the position of the oscillating pen 3. Then, the correct position of the coordinates can be detected.

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.

In this type of device that uses plate wave elastic waves as vibration waves, the vibration delay time is determined by measuring the delay time Tg due to the group velocity. If you explain in detail,
Based on a predetermined position of the envelope of the electrical signal detected by the vibration sensor, it is recognized that the vibration has reached the sensor of interest, and the vibration delay time from the vibration pen to the vibration sensor of interest is determined.

Usually, the peak position or inflection point of the envelope is often detected as the predetermined position of the envelope.

Furthermore, the vibration delay time Tp due to the phase velocity is detected,
It is configured to calculate the coordinate position of the vibrating pen by calculating Tg and 'rp.

[Problems to be Solved by the Invention] However, it has been found that the waveform of the detection signal detected by the vibration sensor changes depending on the distance between the vibration sensor and the vibration pen due to dispersion and the like.

Due to this waveform change, the arrival time Tg of the group velocity detected by the detection method described above does not maintain linearity with respect to distance, which has been an obstacle to detecting accurate coordinate positions.

The present invention was made in view of this problem, and regardless of the change in the detection waveform of the vibration sensor due to the vibration propagation distance,
It is an object of the present invention to provide a coordinate input device that makes it possible to detect accurate coordinate positions.

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

That is, in a coordinate input device that detects vibrations generated from a vibrating pen by 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 generated by the vibration pen is detected by the vibration sensor. a detection means for detecting a change in the signal characteristics of the detected signal, a correction means for correcting the vibration transmission time to the vibration sensor of interest based on the detection result of the detection means, and each vibration sensor corrected by the correction means. calculation means for calculating the coordinate position of the vibrating pen based on the vibration transmission time corresponding to the vibration transmission time.

[Operation] In the configuration of the present invention, the detection means detects the signal characteristics of the signal detected by the vibration sensor, and the correction means corrects the vibration transmission time based on the detection result. and,
The calculation means calculates the coordinate position of the vibrating pen based on the corrected vibration transmission time corresponding to each 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, 1 is an arithmetic control circuit that controls the entire device and calculates coordinate positions. 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 vibration ben 3 is performed by touching the top of this 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 vibration bevel 3, and the dot is displayed on the vibration transmission plate 8 (as it is made of a transparent material).
It is now possible to see through it. That is, a dot is displayed at a position on the display 11 corresponding to the detected coordinates of the vibrating ben 3, and an image composed of elements such as points and lines input by the vibrating ben 3 is displayed as if it were written on paper. Appears after the trajectory of the vibrating ben.

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 vibrator 3 includes a vibrator (made of a piezoelectric element) 4 that vibrates based on a signal supplied by the 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 5 ms), 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. (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 vibration ben.

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

FIG. 3 shows the internal configuration of the arithmetic control circuit 1 in the 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 34a 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. Although the details will be described later, based on the information from the envelope level detection circuit in the signal waveform detection circuit 9, the vibration arrival time detected by each of the vibration sensors 6a to 6b is corrected, and after a predetermined calculation, The coordinate position on the vibration transmission plate 8 by the vibration ben 3 is calculated. Then, by outputting the calculated coordinate position information to the display drive circuit IO via the I10 boat 37, a dot or the like is displayed at the corresponding position on the display, for example.

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 no coordinates have been input by the vibrating pen 3, and the coordinate position is not calculated, and the processing 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 vibrating pen 3 to the vibration transmission plate 8 in synchronization with this signal travel for a time tg corresponding to the distance to the vibration sensor 6a, and then are detected by the vibration sensor 6a. The signal indicated by 42 indicates the signal waveform detected by the vibration sensor 6a.

By the way, the vibration used in the example is a plate wave,
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 changes during vibration transmission according to the transmission distance.

Here, let Vg be the advancing speed of the envelope 421, that is, the group velocity, and Vp be the phase velocity of the phase 422. The distance between the vibrating pen 3 and the vibration sensor 6a 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 becomes d=n·λp+vp-tp...■. Here, λp is the wavelength of the elastic wave, and n is an integer.

The above integer n can be calculated from the formula (■) and the formula (0) as n= [(Vg-
tg-Vp-tp)/λp+1/Nl...
・It is expressed as ■.

Here, N is a real number other than 0, and an appropriate value is used.

For example, if N=2 and within ±172 wavelengths, n can be determined. Set n calculated as above to 0
By substituting into the formula, the vibration pen 3 and the vibration sensor 6a
The distance between the vibrating pen 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 multi-by-break circuit, etc., and is input to the arithmetic control circuit 1.

Moreover, this signal Tg is the monostable multi-by-break 55 (
After passing through a comparator level supply circuit 56 (generating a signal 44 with a predetermined pulse width) and a signal 44 having a predetermined pulse width, it is supplied to a comparator Tp detection circuit 58 for comparison with the original signal delayed by a delay time adjustment circuit 57. . The comparator Tp detection circuit 58 supplies the phase delay time signal Tp to the arithmetic control circuit l.

On the other hand, the envelope detection circuit 52 separately from the signal Tg indicating the group velocity delay time signal and the phase delay time signal Tp.
The envelope level detected by the envelope level detection circuit 59 is detected by the envelope level detection circuit 59. The envelope level detection circuit is, for example, an A/D converter, and its level data is output to the arithmetic control circuit I and used in the correction process described above.

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 each of envelope delay time Tgl-h and phase delay time Tpl-h are input to the arithmetic control circuit l.

Then, in the arithmetic control circuit 1, the above Tgl~h, Tpl
~h signals are input from the input port 35, and the time values (count values) of the timer 33 are taken into the latch circuits 34a to 34c as respective timing triggers. Since the timer 33 is started in synchronization with the driving of the vibrating pen, the latch circuits 34 to 34c will latch data indicating the respective delay times of the envelope and phase of each of the vibration sensors 6a to 6C. .

Explanation of correction processing and coordinate position calculation (FIGS. 6 to 8)> Next, correction of the vibration transmission time in the embodiment and coordinate position calculation processing based on the correction will be described.

Group velocity delay time Tg obtained by the above process
As shown by the solid line in FIG. 7, the linearity is lost in region a, as shown by the solid line in FIG. In other words, if the obtained Tg is within the a region, the detected coordinate position will naturally be affected, making it impossible to obtain an accurate coordinate position.

This is because the waveform rapidly deforms when the distance between the indicated position of the vibrating pen 3 and the vibration sensor 6a (the same applies to other sensors) exceeds a certain value. Also,
Similarly, the electrical signal (fourth
The relationship between the detection level (amplitude) of signal 42 (corresponding to signal 42 in the figure) and their distance is as shown in Figure 8.
The greater the distance, the lower the level of the detection signal.

Therefore, in this embodiment, the level of this detection signal is detected indirectly by detecting the envelope level using the envelope level detection circuit 59, and the delay time caused by each vibration sensor is corrected using the detected level. It is something to do. In other words, based on the detected level, RO
The correction amount ΔTg is obtained by referring to the correction table stored in M31a, and the correction is performed by subtracting the ΔTg from the Tg before correction.

Note that this is not limited to the case where the correction amount ΔTg is subtracted from the actual measurement value rg. For example, the correction amount ΔTg may be calculated using the relationship of true delay time Tg=correction amount f×actual measurement value Tg. In this case, the value of the correction amount f is set to "1" for the portion where linearity is maintained outside the a region, and
Within the area, the corresponding numerical value is less than 1.

Based on the corrected delay time Tg thus obtained, an accurate distance between the vibration sensor 6a and the vibration ben 3 can be calculated.

The principle of calculating the coordinate input position of the vibrating vent 3 will be explained below.

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

Then, the distances between the vibration vent 3 and each of the vibration sensors 6a to 6c, which were determined based on the principle explained earlier, are calculated from d1 to 6c, respectively.
When dc is assumed, the obtained P(x, y) is as shown in the following equation according to the Pythagorean theorem.

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.

As described above, according to this embodiment, by correcting the detection delay time due to the waveform deformation of the detection signal of the vibration sensor, it is possible to detect an accurate coordinate position.

In the embodiment, the correction amount is obtained from the relationship between the level of the detection signal and the distance, and the accurate coordinate position is calculated, but the present invention is not limited to this.

For example, since the frequency component of the envelope also changes depending on the distance, the change in the frequency component may be made to correspond to the correction amount of Tg.

[Effects of the Invention] As described above, according to the present invention, it is possible to detect accurate coordinate positions regardless of changes in the detection waveform of the vibration sensor due to the vibration propagation distance.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the coordinate input device of this embodiment, Fig. 2 is a diagram showing the structure of the vibration vent, Fig. 3 is a diagram showing the internal configuration of the arithmetic control circuit in the embodiment, and Fig. 4 is a vibration Figure 5 is a diagram for explaining the distance measurement between Ben and the vibration sensor. Figure 5 is a diagram showing a partial configuration of the signal waveform detection circuit in the embodiment. Figure 6 is for explaining the principle of coordinate position calculation. FIG. 7 is a diagram showing the relationship between starting transmission time and distance, and FIG. 8 is a diagram showing the relationship between detection level by a vibration sensor and distance. In the figure, 1... 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, 11... Display, 31... Microcomputer, 31 a=ROM, 3 l b-RAM
. 33...Timer, 34a-34c...Latch circuit,
35...Detection signal input port, 36...Judgment circuit,
37...I10 boat. Canon Co., Ltd. (Sho exit site)

Claims (1)

[Scope of Claims] A coordinate input device that detects vibrations generated from 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, comprising: a detection means for detecting a change in signal characteristics of a signal detected by the vibration sensor; a correction means for correcting the vibration transmission time to the vibration sensor of interest based on the detection result of the detection means; A coordinate input device comprising: calculation means for calculating the coordinate position of the vibrating pen based on the vibration transmission time corresponding to each vibration sensor.