JPH02130619A - coordinate input device - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

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.

A human-powered 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, by measuring the vibration transmission time to each vibration sensor, the designated coordinate position is calculated.

The advantage of this method is that the vibration transmission plate that makes up the input tablet has a very simple structure and can be manufactured at low cost.Also, transparent glass etc. can be used as the vibration transmission plate, so the display screen can be For example, it can be placed on the front or used over a document or the like.

[Problems to be Solved by the Invention] By the way, a vibrator (such as a piezoelectric element) is installed inside this vibrating pen to generate the vibration, but the vibrator has temperature characteristics. , its resonant frequency, and the combined resonant frequency of the vibrator and the pen tip that transmits the vibration to the vibration transmission plate change depending on the temperature.

The vibration waveform detected by a vibration sensor naturally needs to have a waveform with little distortion, but for the reasons mentioned above, coordinate detection processing has always been performed with a distorted vibration waveform, so it is not possible to achieve stable and high precision. It was not possible to perform accurate coordinate detection.

The present invention has been made in view of such problems, and it is an object of the present invention to provide a coordinate input device that can always detect coordinate input points with high accuracy regardless of temperature changes.

[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 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, at least A temperature detection means for detecting the temperature of the vibrator, a signal generation means for generating a drive signal for driving the vibrator, and a frequency of the drive signal generated by the signal generation means is detected by the temperature detection means. and control means for controlling the resonant frequency of the vibrator to correspond to the temperature.

[Function] In the configuration of the present invention, the temperature detecting means detects the temperature of the vibrator built in the vibrating vent, and the signal generating means generates a drive signal having a resonant frequency of the vibrator corresponding to the detected temperature. The control means controls the occurrence of such occurrence.

[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 material such as an acrylic or glass plate. Coordinate input using the vibration ben 3 is performed by touching the top of this vibration transmission plate 8. On the outer periphery of this vibration transmission plate 8, An antireflection material 7 is provided to prevent (reduce) reflected vibrations from returning to the center, and vibration sensors 6a to 6c, such as piezoelectric elements, that convert mechanical vibrations into electrical signals are placed at the positions shown in the figure at the boundaries thereof. Fixed.

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), which is disposed 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 it is possible to see it through the vibration transmission plate 8 (as it is made of a transparent member). 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. In addition to the pen tip 5, a temperature sensor 12 for detecting the temperature of the vibrator 4 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.

Further, although the details will be described later, the temperature detected by the temperature sensor 12 is taken into the arithmetic control circuit l, and the vibrator drive circuit 2
It feeds back to the drive signal generated from the By setting the vibration frequency of the vibrator 4 to the resonance frequency of the vibrator 4, efficient vibration conversion is possible.

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), a signal for driving the vibrator 4 in the vibrating vent 3 is output to the vibrator drive circuit 2, and an internal timer (consisting of a counter) starts measuring time. 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 detects signals from each of the vibration sensors 6a to 6c, and generates a signal indicating the timing of vibration arrival at each vibration sensor through waveform detection processing, which will be described later. Input this signal and detect the vibration arrival time to each vibration sensor 6a to 6c.
Then, the coordinate position of the vibrating ben is calculated.

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,
It has a built-in ROM 31a1 that stores operating procedures (flowchart in FIG. 8) and tables to be described later, and a RAM 31b that is used as a work area. 33 is a timer (consisting of a counter) that measures a reference clock (not shown), and outputs a start signal to the vibrator drive circuit 2 to start driving the vibrator 4 in the vibrating vent 3. Then, start measuring the time. In other words, 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.

Each vibration sensor 6a obtained via the signal waveform detection circuit 9
The timing signal of arrival of the vibration of ~6C is manually input to the latch circuits 34a to 34e via the detection signal input port 35. The latch circuits 34a to 34c are vibration sensors 6a to 6c.
, and when each receives a timing signal that is a signal from a corresponding vibration sensor, the timer 3 at that time
Latch the time value of 3. 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 348 to 34c to each vibration sensor, performs a predetermined calculation, and determines the coordinates of the vibration ben 3 on the vibration transmission plate 8. Calculate the position.

Then, by outputting the calculated coordinate position information to the display drive circuit 10 via the I10 boat 37,
For example, a dot or the like is displayed at a corresponding position on the display.

Also, during this time, temperature information obtained from the temperature sensor 12 is taken into the microcomputer 31 via the I10 boat 37.

The microcomputer 31 stores this temperature information in the ROM 31.
The corresponding vibration frequency is determined by referring to the temperature-pulse frequency table stored in a, and the vibrator drive circuit 2 is controlled to generate a vibrator drive signal of that frequency. Note that details of this processing will be described later.

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 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, the speed at which the envelope 421 advances, that is, the group velocity, is Vg, and the phase velocity of the phase 4220 is Vp. 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 velocity is Vg, and when a point on a certain waveform, for example a peak, is detected as a signal indicated by 43 in the figure, the distance between the vibration vent 3 and the vibration sensor 6a is atd is d-Vg-tg, where the vibration transmission time is tg...
(2) Although this equation relates to one of the vibration sensors 6a, the distance between the other vibration sensors 6b, 6c and the vibration ben 3 can also be expressed using the same principle.

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 11d between the vibration sensor and the vibration pen becomes dwn·λp+Vp-tp...■. 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/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, 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 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 with 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. . The comparator Tp detection circuit 58 supplies the phase delay time signal "rp" to the arithmetic control circuit 1.

Note that the circuit described 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 envelope delay times Tgl to h and phase delay times Tpl to h are manually input to the arithmetic control circuit 1.

Then, in the arithmetic control circuit 1, the above Tgl~h%Tp1
The ~h signal is input manually from the input boat 35, and the time value (count value) of the timer 33 is taken into the latch circuits 34a to 34c using each timing as a trigger. 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 Coordinate Position Calculation (FIG. 6)> Next, the principle of actually detecting the coordinate position on the vibration transmission plate 8 using the vibrating pen 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 coordinate positions of the vibration sensors 6b and 6c are S b (X, 0), S c (0, Y)
shall be. Then, the coordinates of the vibrating pen are P (x, y).

Then, based on the principle explained earlier, if the distances between the vibrating pen 3 and each of the vibration sensors 6a to 6C are d and ~dc, the obtained p(x, y) can be calculated using the following equation from 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.

As described above, the position coordinates of the vibrating pen 3 can be detected in real time.

Explanation of the correction processing of the vibration drive signal (Figs. 7 and 8)> Next, in this device that detects the coordinate position using the configuration and principle described above, the voltage applied to the vibrator 4 generated from the vibrator drive circuit 2 will be explained. The frequency correction process of the signal 41 will be described below.

The temperature of the piezoelectric element constituting the vibrator 4 is generally -20°C to 60°C (although it varies depending on its material), and its resonance frequency f is approximately 100 to 600 kHz (ppm/ll). The vibrator 4 in the embodiment has a temperature characteristic of fr of 3.
00 [KHz] [P Pm /'C] PZT was used.

Then, the driving frequency at 20°C is 400[K)121[
ppm/'e] is the optimal value (=f of PZT),
R
Stored in OM3ia. In other words, the table shown in FIG. 7 shows the resonant frequency of the vibrator 4 corresponding to the temperature.

In the case shown, the practical use temperature range is 2.5℃~47℃.
．． 5° C. and the correction temperature interval is 5° C., but the practical use temperature range, correction temperature interval, etc. may of course be changed depending on the usage conditions or specifications.

The operation processing of the embodiment will be described below according to the flowchart of FIG.

When the device is powered on, first, in step S1, the temperature of the vibrator 4 is detected by the temperature sensor 12. Then, the process proceeds to step S2, and the frequency of the drive signal corresponding to the detected temperature is derived based on the table stored in the ROM 31 (see FIG. 7). Thereafter, the process proceeds to step S3, where the vibrator drive circuit 2 is set to generate a drive signal of that frequency. Thereafter, by applying a drive signal having this set frequency to the vibrator 4, at least the vibrator 4 itself will resonate. At this time, the microcomputer 31 stores temperature information corresponding to the set driving frequency in the RAM 3 lb.

Now, after the frequency setting is completed in this way, the process advances to step S4, where processing related to actual coordinate input and output processing of calculated coordinate data (in the embodiment, display 11
output) is performed.

The process then proceeds to step S5, where the temperature is detected again, and in step S6, it is determined whether or not it is necessary to change the set frequency in view of the temperature information stored in the RAM 3 lb. While it is determined that the drive frequency does not need to be changed, the process of step S4 is repeated, and when it is determined that a change is necessary, the process from step S2 onwards is executed. At this time, the temperature information stored in the RAM 31b is also updated.

In the embodiment, the temperature is constantly detected and the vibration frequency is corrected, but for example, a timer or the like is used to generate an interrupt signal every 30 minutes, and the frequency of the drive signal is set by the interrupt processing. You may also do this.

Further, in the embodiment, the temperature detection target of the temperature sensor 12 is only the vibrator 4, but both the vibrator 4 and the horn section 5 may be used. In this case, there is an advantage that the drive frequency can be corrected to reflect the resonance characteristics of the entire vibrating vent 3 while also taking into account the temperature characteristics of the horn section 5 itself.

The temperature sensor 12 is not particularly limited as long as it can accurately detect the temperature around room temperature and is small enough to fit inside the pen.

Description of another embodiment (FIG. 9) In the embodiment described above, the drive frequency generated from the vibrator drive circuit 2 was corrected in accordance with the temperature characteristics of the resonance frequency of the vibrator 4 of the vibrating pen 3. As shown in FIG. 9, a temperature sensor 13 for detecting the temperature of the vibration transmission plate 8 may be newly added. In this case, correction that takes into account temperature characteristics such as propagation characteristics of the vibration transmission plate 8 can be performed by changing the driving frequency, and more comprehensive temperature correction can be performed for the entire device.

As explained above, according to this embodiment, at least the vibrator in the vibrating pen can be vibrated at a resonant frequency corresponding to the temperature of the vibrator itself, and the coordinate position can be detected stably and with high precision. becomes possible.

Further, by expanding the temperature detection target to the horn portion 5 of the vibrating pen 3 and further to the vibration transmission plate 8, it becomes possible to input coordinates with higher accuracy and stability.

[Effects of the Invention] As explained above, according to the present invention, it is possible to cause the vibrator in the vibrating pen to always resonate regardless of temperature changes, so a detection waveform with less distortion can be detected by the vibration sensor. This makes it possible to input stable and highly accurate coordinates.

[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 showing the relationship between the temperature of the vibrator and the resonant frequency in the embodiment, and FIG. A flowchart for explaining the processing contents of the microcomputer in the embodiment, and FIG. 9 is a block diagram of the coordinate human-powered device of another embodiment. 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, 12.13... Temperature sensor, 13... Buzzer 31... Microcomputer, 3ia=ROM, 3 l b. RAM, 3
3-...Timer, 34a-34c...Latch circuit, 3
5...Detection signal human powered boat, 36...Judgment circuit, 3
7...I10 boat. Patent applicant Canon Co., Ltd. agent Patent attorney Yasunori Otsuka (and one other person) Figure 4 Figure 5 Figure 6 Figure 8

Claims (1)

[Claims] Coordinate input for detecting vibrations generated from a vibrator in a vibrating pen using a plurality of vibration sensors provided on a vibration transmission plate, and detecting the position of the vibrating pen from the vibration transmission time to each vibration sensor. The apparatus includes at least temperature detection means for detecting the temperature of the vibrator, signal generation means for generating a drive signal for driving the vibrator, and a frequency of the drive signal generated by the signal generation means based on the temperature. A coordinate input device comprising: control means for controlling the resonant frequency of the vibrator to correspond to the temperature detected by the detection means.