JPH05189135A - Coordinate input device - Google Patents

Abstract

PURPOSE:To provide the high-accuracy coordinate input device. CONSTITUTION:When vibrations are applied to a vibration transmitting board 8 by a vibrating pen 3, they are transmitted through the transmitting board 8 and detected by vibration sensors 6a-6d. Only the prescribed frequency is extracted from the detected signal by a band pass filter 9, this signal is logarithmically amplified by a logarithmical amplifier 10 and afterwards, it is judged whether the signal reaches a prescribed level or not. When the signal reaches it, with that time point as transmission delay time, a distance from a coordinate indicator to the vibration sensors 6a-6d is calculated. Then, the input coordinate value of the vibrating pen 3 is calculated from the measured distance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coordinate input device for specifying a position of a vibration source by utilizing a transmission delay time of elastic vibration and for inputting coordinates.

[0002]

2. Description of the Related Art Conventionally, a coordinate input device using various input pens and tablets has been known as a device for inputting handwritten characters, graphics and the like into a processing device such as a computer. In this type of device, the input image information including characters and figures is displayed and output on a display device such as a CRT display or a recording device such as a printer. Among such coordinate input devices, the following various methods are known as a coordinate detection method in a tablet type coordinate input device.

A method of detecting the coordinate value of a pressed point by a change of the resistance value of the sheet material, which is made of a sheet material arranged to face the resistance film.

A method of detecting a coordinate position based on electromagnetic or electrostatic induction of a conductive sheet or the like arranged opposite to each other.

A method of detecting the coordinate position of the input pen based on the ultrasonic vibration transmitted from the input pen to the tablet.

However, the conventional coordinate input device adopting these methods has the following drawbacks.

That is, in the case of (the case of) the type using the resistance film described above, the uniformity of the resistor directly influences the accuracy of the figure input, so that the resistor having excellent uniformity is required,
The larger the device, the more difficult it is to make, and it is not suitable for devices that require high precision. In addition, since two resistance films for the X coordinate and the Y coordinate are required, the transparency of the coordinate input surface is reduced. For this reason, there is also a drawback that the original becomes difficult to see when it is used by overlapping it with the original.

Next, in the case of the type utilizing electromagnetic induction (in the case of), the electric wires are arranged in a matrix, and the coordinate detection accuracy is the position of the electric wires arranged in the matrix, that is, the processing accuracy. It is very expensive in a high-precision input device, because it is directly influenced by.

Compared to these methods, the ultrasonic method (in the case of) is a method for calculating the position coordinates by detecting the delay time of a wave propagating on the tablet which is the input surface, and Since no work such as a matrix electric wire is applied, it is possible to provide an inexpensive device. Moreover, if a transparent plate glass is used for the tablet, it is possible to construct a coordinate input device having higher transparency than other methods.

However, in the conventional ultrasonic type coordinate input device, the detected waveform of the wave output by the sensor not only changes the amplitude level due to the attenuation of the wave depending on the distance between the vibration input pen and the sensor, but also the operator. It greatly depends on the pen pressure of the input pen.

Therefore, when the delay time is detected with a specific point where the detection signal waveform is above a certain level (the level needs to have a certain value or more to distinguish from noise), the detection signal is detected. Depending on the level of the waveform, the specific point detected despite the same coordinate position moves back and forth and shifts by several cycles, which causes a defect that the coordinate is erroneously detected. To address this issue,
A method has been adopted in which the envelope of the detected signal waveform is electrically extracted and subjected to differential processing to detect the peak of the envelope or the inflection point of the envelope as a specific point and measure the delay time.

[0012]

In these methods, in order to eliminate the above-mentioned problem of deterioration of the detection accuracy due to the reflected wave, the phase delay time and the group delay time or the phase delay time with the leading portion of the detected waveform as a specific point. Only need to detect. However, since the phase delay time is the specific point near the amplitude of the detected waveform being above a certain level, there is a problem that when the level of the detected waveform becomes smaller, the specific point is later on the time axis than the beginning part. In addition, since the group delay time has the peak or inflection point of the envelope of the waveform as the specific point, there is a problem that the head portion does not become the specific point. Therefore, it is difficult to measure the delay time from the beginning of the detected waveform stably without being affected by the reflected wave by any of the methods, which is a new cause of deterioration of the coordinate detection accuracy. However, in order to avoid the influence of reflected waves, the coordinate input plate must be made sufficiently large, which causes a problem that the device becomes large.

The present invention has been made in view of the above-mentioned conventional example, and an object thereof is to provide a small-sized coordinate input device capable of highly accurate coordinate detection.

[0014]

In order to achieve the above object, the coordinate input device of the present invention has the following configuration.

A plurality of vibration sensors are arranged on a coordinate input surface for propagating vibration, and the distance between each of the coordinate indicator and the sensor for generating vibration is measured from the arrival time of the vibration, and the coordinate indicator is used to measure the distance. A coordinate input device for calculating and outputting a designated point on a coordinate input surface as a coordinate value, the signal generating unit generating an electric signal based on the vibration detected by the vibration sensor, and the signal generating unit generated by the signal generating unit. It comprises means for logarithmically amplifying the signal, and means for determining that the logarithmically amplified signal has reached a predetermined level, and vibrates from the time when the indicator is vibrated until the time when the predetermined level is reached. The distance is measured as the arrival time.

[0016]

With the above structure, the vibration applied to the coordinate input surface by the coordinate pointing device is detected by the vibration sensor, and an electric signal based on the vibration is generated. This signal is logarithmically amplified, and then it is determined whether or not it has reached a predetermined level, and if it has reached that level, the distance between the coordinate indicator and the vibration sensor is measured with that point of time as the transmission delay time.

[0017]

FIG. 1 shows the structure of a coordinate input device according to this embodiment. In the figure, 1 controls the entire apparatus,
It is an operation control circuit for calculating the coordinate position. Reference numeral 2 is a vibrator drive circuit for vibrating the pen tip inside the vibrating pen 3. Reference numeral 8 is a vibration transmission plate made of a transparent member such as acrylic or glass plate, and the coordinate input by the vibration pen 3 is performed by touching the vibration voltage plate 8. That is, the vibration generated by the vibrating pen 3 is made incident on the vibration transmission plate 8 by designating the area (hereinafter, referred to as an effective area) indicated by a solid line A in the figure with the vibrating pen 3, and The position coordinates of the vibrating pen 3 can be calculated by measuring and processing.

In order to prevent (decrease) the propagating wave from being reflected at the end face of the vibration transmitting plate 8 and returning to the central portion of the vibration transmitting plate 8, a vibration isolator 7 is provided on the outer periphery of the vibration transmitting plate 8. The
As shown in FIG. 1, vibration sensors 6a to 6d, such as piezoelectric elements, which convert mechanical vibrations into electric signals are fixed near the inside of the vibration isolator. The electric signals converted by the vibration sensors 6a to 6d are extracted by the bandpass filter 9 only for a single frequency component, and then logarithmically amplified by the logarithmic amplifier 10.
The signal subjected to logarithmic amplification processing is further subjected to waveform detection processing, which will be described later, in the signal waveform detection circuit 11, and then the arithmetic control circuit 1
Is output to. Reference numeral 13 is a display such as a liquid crystal display capable of displaying in dot units, and is arranged behind the vibration transmission plate. Then, by driving the display drive circuit 12, dots are displayed at the position traced by the vibrating pen 3.
It is possible to see it through the vibration transmission plate 8 (made of a transparent member).

The vibrator 4 built in the vibrating pen 3 is driven by the vibrator driving circuit 2. The drive signal for the vibrator 4 is supplied as a low-level pulse signal from the arithmetic control circuit 1, amplified by a predetermined gain by the vibrator drive circuit 2, and then applied to the vibrator 4. The electric drive signal is converted into mechanical vibration by the vibrator 4, and is transmitted to the vibration transmission plate 8 via the pen tip 5.

Here, the vibration frequency of the vibrator 4 is selected to a value capable of generating a plate wave on the vibration transmission plate 8 such as glass. Further, when driving the vibrator, a mode in which the vibration transmitting plate 8 vibrates in the vertical direction of FIG. 2 is selected. Further, by setting the vibration frequency of the vibrator 4 to the resonance frequency including the pen tip 5, it is possible to efficiently perform vibration conversion. The elastic wave transmitted to the vibration transmission plate 8 as described above is a plate wave, and has an advantage that it is less susceptible to scratches or obstacles on the surface of the vibration transmission plate as compared to surface waves.

<Description of Arithmetic and Control Circuit> In the above-mentioned configuration, the arithmetic and control circuit 1 operates every predetermined period (for example, every 5 ms).
Then, a signal for driving the vibrator 4 is output to the vibrator driving circuit 2 and the vibrating pen 3, and the internal timer (which is composed of a counter) starts timing. And
The vibration generated by the vibrating pen 3 propagates on the vibration transmission plate 8 and arrives with a delay depending on the distance to the vibration sensors 6a to 6d.

The signal waveform detection circuit 11 includes the vibration sensors 6a.
The signal from 6d is detected, and the signal which shows the vibration arrival timing to each vibration sensor is generated by the waveform detection processing described later. The arithmetic control circuit 1 inputs this signal for each sensor, The vibration arrival time to the sensors 6a to 6d is detected, and the coordinate position of the vibration pen is calculated. Further, the arithmetic control circuit 1 drives the display drive circuit 12 based on the calculated position information of the vibrating pen 3 to control the display by the display 13, or outputs the coordinate output to an external device by serial or parallel communication. Perform (not shown).

FIG. 3 is a block diagram showing a schematic structure of the arithmetic and control circuit 1 of the embodiment, and each constituent element and its operation outline will be described below.

In the figure, reference numeral 31 is a microcomputer for controlling the arithmetic control circuit 1 and the coordinate input apparatus as a whole, and an internal counter, a ROM storing operation procedures, a RAM used for calculation and the like, and a nonvolatile memory storing constants and the like. It is composed of a memory. Reference numeral 33 is a timer (not shown) that counts a reference clock and is configured to input a start signal to the vibrator driving circuit 2 to start driving the vibrator 4 in the vibration pen 3. Then, the timing starts. By this, the start of timing and the vibration detection by the sensor are synchronized, and the sensors 6a ...
The delay time until the vibration is detected by 6d can be measured.

The vibration arrival timing signals from the vibration sensors 6a to 6d output from the signal waveform detection circuit 11 are
Latch circuits 34 a to 3 via the detection signal input port 35
4d is input. Each of the latch circuits 34a to 34d corresponds to each of the vibration sensors 6a to 6d, and when receiving the timing signal from the corresponding sensor, it latches the measured value of the timer 33 at that time. When the determination circuit 36 determines that all detection signals have been received in this manner, it outputs a signal to that effect to the microcomputer 31. When the microcomputer 31 receives the signal from the determination circuit 36, the vibration arrival time from the latch circuits 34a to 34d to the respective vibration sensors is read from the latch circuit, a predetermined calculation is performed, and the vibration on the vibration transmission plate 8 is vibrated. The coordinate position of the pen 3 is calculated. And I / O port 3
By outputting the calculated coordinate position information to the display drive circuit 12 via 7, the display 12
A dot or the like can be displayed at the position corresponding to. Alternatively, the coordinate value can be output to an external device by outputting the coordinate position information to the interface circuit via the I / O port 37.

<Description of Vibration Propagation Time Detection (FIGS. 4 and 5)
> Hereinafter, the principle of measuring the vibration arrival time to the vibration sensor 3 will be described.

FIG. 4 is a diagram for explaining a detection waveform input to the signal waveform detection circuit 9 and a vibration transmission time measuring process based on the detection waveform. The vibration sensor 6a will be described below, but the other vibration sensors 6b, 6c, 6
The same is true for d. It has already been described that the measurement of the vibration transmission time to the vibration sensor 6a starts simultaneously with the output of the start signal to the vibrator drive circuit 2. At this time,
A drive signal 41 is applied from the oscillator drive circuit 2 to the oscillator 4. The ultrasonic vibration transmitted from the vibration pen 3 to the vibration transmission plate 8 by the signal 41 is transmitted to the vibration sensor 6a.
After traveling for a time tg corresponding to the distance up to, the vibration sensor 6a detects the vibration.

The signal indicated by 42 in the figure shows the signal waveform detected by the vibration sensor 6a. Since the vibration used in this embodiment is a plate wave, the envelope 421 and the phase 422 of the detected waveform with respect to the propagation distance in the vibration transmission plate 8
During vibration transmission, the relationship of changes according to the transmission distance. Here, the traveling speed of the envelope 421, that is, the group speed is Vg, and the phase speed of the phase 422 is Vp.
The distance between the vibration pen 3 and the vibration sensor 6a can be detected from 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 specific waveform, for example, an inflection point or a peak such as a signal shown in FIG. 43 is detected, the vibration pen 3 and the vibration are detected. The distance between the sensors 6a is
Given that the vibration transmission time is tg, d = Vg · tg (1) This equation relates to one of the vibration sensors 6a. The same equation applies to the other three vibration sensors 6b.
The distance between 6d and the vibrating pen 3 can be similarly expressed.

Further, in order to determine the coordinates with higher accuracy, processing based on the detection of the phase signal is performed. The time from the specific detection point of the phase waveform signal 422, for example, the vibration application to the zero cross point after a certain predetermined signal level 46 is Tp.
45 (obtained by generating the window signal 44 having a predetermined width with respect to the signal 47 and comparing it with the phase signal 422), the distance between the vibration sensor and the vibration pen is d = n · λp + Vp · tp (2) Becomes Here, λp is the wavelength of the elastic wave, and n is an integer.

From the above equations (1) and (2), the above integer n
Is expressed as n = int [(Vg · tg−Vp · tp) / λp + 1 / N] (3).

Here, N is a real number other than "0", and an appropriate value is used. For example, if N = 2, then n can be determined if there is a variation such as tg within ± 1/2 wavelength.

By substituting the determined value n into the equation (2), the distance between the vibration pen 3 and the vibration sensor 6a can be accurately measured. Signals 43 and 4 for measuring the above two vibration transmission times tg and tp
Generation of 5 is performed by the signal waveform detection circuit 11, which is configured as shown in FIG.

FIG. 5 is a block diagram showing the configuration of the signal waveform detection circuit 11 of the embodiment. In FIG. 5, the output signal of the vibration sensor 6a is amplified to a predetermined level by the preamplifier circuit 51. The bandpass filter 511 removes extra frequency components of the detected signal from the amplified signal,
For example, it is input to the envelope detection circuit 52 including an absolute value circuit and a low-pass filter, and only the envelope of the detection signal is extracted. The timing of the envelope peak is determined by the envelope peak detection circuit 5
3 is detected. In the peak detection circuit, a signal tg (signal 43 in FIG. 4) which is an envelope delay time detection signal having a predetermined waveform is formed by the tg signal detection circuit 54 composed of a mono multivibrator or the like, and the signal tg is input to the arithmetic control circuit 1.

On the other hand, 55 is a signal detection circuit, which detects the envelope signal 42 detected by the envelope detection circuit 52.
The pulse signal 47 of a portion exceeding the threshold value signal 46 (hereinafter, referred to as a comparator level) having a predetermined level in 1 is formed. 56 is a monostable multivibrator, which opens the gate signal 44 of a predetermined time width triggered by the first rising edge of the pulse signal 47. Reference numeral 57 denotes a tp comparator, which detects the first rising zero-cross point of the phase signal 422 while the gate signal 44 is open, and supplies the phase delay time signal tp45 to the arithmetic control circuit 1. The circuit described above is for the vibration sensor 6a, and the same circuit is provided for other vibration sensors.

<Explanation of delay time correction> Strictly speaking, the vibration transmission time latched by the latch circuit is, for example, the time during which the sound wave travels in the horn 5, the time during which the signal output from the sensor is processed by the circuit, and the like. Is included. Therefore, these delay times other than the time when the wave propagates on the vibration transmission plate 8 are defined as the intrinsic delay time et. Further, the difference between the group delay time and the phase delay time at the reference point is defined as the phase offset time t.
Defined as off. The error caused by these is always included in the same amount when the vibration is transmitted from the vibration pen 3 to the vibration transmission plate 8 and the vibration sensors 6a to 6d. Therefore,
For example, when the position of the origin O in FIG. 6 is set as the reference point and the distance to the vibration sensor 6a is R1 = (X / 2), the origin O is measured by the vibration pen 3 at the origin O. The measured vibration transmission time to the sensor 6a is tgz ', t
pz ', and the true transmission time from the origin O to the sensor is t
Assuming gz and tpz, these have a relationship of tgz '= tgz + et (4) tpz' = tpz + et + toff (5) with respect to the intrinsic delay time et and the phase offset toff.

On the other hand, the measured value tg 'at an arbitrary input point P
Similarly, tp 'is tg' = tg + et (6) tp '= tp + et + toff (7). When the difference between these (4), (6), (5) and (7) is calculated, tg'-tgz '= (tg + et)-(tgz + et) = tg-tgz (8) tp'-tpz '= (tp + et + toff)-(tpz + et + toff) = tp-tpz (9), the intrinsic delay time et and the phase offset toff included in each transmission time are removed, and from the position of the origin O. It is possible to obtain the difference in the true transmission delay time according to the distance from the position of the sensor 6a between the input points P as the starting point, and it is possible to obtain the difference in distance by using the equations (2) and (3). Since the distance from the vibration sensor 6a to the origin O is stored in advance in a non-volatile memory or the like and can be known, the distance between the vibration pen 3 and the vibration sensor 6a can be determined. The other sensors 6b to 6d can be similarly obtained. The measured values tgz 'and tpz' at the origin O
Is previously stored in the non-volatile memory, and (2),
The equations (8) and (9) are executed before the calculation of the equation (3), and highly accurate measurement can be performed.

<Description of Coordinate Position Calculation (FIG. 6)> Next, the principle of actually detecting the coordinate position on the vibration transmission plate 8 by the vibration pen 3 will be described. Now, if four vibration sensors 6a to 6d are provided at positions S1 to S4 near the midpoints of four sides on the vibration transmission plate 8, each of the vibration sensors 3a to 6d from the position P of the vibrating pen 3 based on the principle described above. The linear distances da to dd to the positions of the vibration sensors 6a to 6d can be obtained. Further, the arithmetic control circuit 1 uses the vibrating pen 3 based on the linear distances da to dd.
From the Pythagorean theorem of the coordinates (x, y) of the position P of, the following equation can be used.

X = (da + db) · (da−db) / 2X (10) y = (dc + dd) · (dc−dd) / 2Y (11) where X and Y are vibration sensors 6a and 6b, respectively. And the distance between the vibration sensors 6c and 6d.

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

<Explanation of Effect of Signal Pre-Processing> Here, characteristics of the logarithmic amplifier 10 will be described. Logarithmic amplifier 10
Can be easily configured by combining several electronic components such as operational amplifiers as shown in FIG. The logarithmic conversion utilizes the voltage-current characteristics of the base-emitter voltage and the collector current of the transistor, and the output voltage Vo in FIG. 7 has a value of the following equation with respect to the input voltage Vi.

Vo = -k · T · (R ₇ + R ₈ ) / (q · R ₇ ) · Log _e (R ₆ · Vi / R ₁ / V _CC ) where, k: Poltzmann constant, T: absolute Temperature, q: electronic charge amount, e: base of natural logarithm, R _i : resistance value of resistor R _i , V _CC : power supply voltage.

That is, it can be seen that the output voltage is proportional to the logarithmic value of the input voltage.

FIG. 8 shows an outline of the characteristic of the logarithmic amplifier of FIG. Input and output PEAK to PEAK values were measured using a continuous wave as the input electrical signal. The solid line shows the value of the output signal voltage amplitude with respect to the actually measured input signal voltage amplitude. The broken line is the characteristic of an ideal logarithmic amplifier. The slope of the straight line portion of the characteristic diagram is adjusted by changing the resistance value of the resistor R _{8 in} FIG. 7.

The advantage of the logarithmic amplifier as compared with the automatic gain control described in the prior art is that all the input data are stored because the characteristics of the transistor are used as they are instead of adjusting the gain by referring to the detected signal. This is a point that can be used for coordinate detection. Further, although the maximum amplitude level of the output signal is not always constant, as shown in FIG. 8, the fluctuation of the output signal amplitude level is very small with respect to the change of the input signal amplitude level, and the effect of eliminating the influence of the fluctuation of the input level is initially considered. Is sufficiently satisfied.

FIG. 9 schematically shows the characteristics of the logarithmic amplifier in the actual detection waveform. Reference numerals 91 and 92 are detection waveforms having different levels input to the logarithmic amplifier, and 93 and 94 are output waveforms of the logarithmic amplifier. What can be seen from the comparison for each waveform is the effect of eliminating the influence of the level fluctuation described above. Although the input signals 91 and 92 have a double level difference, the output signals 93 and 94 have a level difference of only a few percent.
Considering the configuration of the signal waveform detection circuit, the comparator level 46 for generating the gate signal 47 described in FIG.
In contrast to (dotted line in FIG. 9), the third waveform of the input signal 91 and the fourth waveform of the input signal 92 are detected as signals having reached a predetermined level. Further, a waveform whose level is lower than that of the input signal 92 cannot be detected by the comparison level 46. However, the output signal 93 after logarithmic amplification,
In 94, the output signal 93 is the first shot, and in the output signal 94, it is 2 shots.
The eye is detected, and as seen from the characteristic diagram of FIG. 8, even if the level is reduced by a factor of 10 or more, it is detected because it is amplified more than the comparator level 46. Disappear. In actual operation,
It can be easily imagined from FIG. 8 that the output becomes almost constant even when the level is increased more than expected due to the increase in the writing pressure of the operator, and erroneous detection due to the level increase is eliminated.

Furthermore, it is another advantage to be emphasized that the logarithmic amplifier is used. Since the automatic gain control sets the gain by referring to the peak value of the detection signal waveform, the waveform size changes, but the waveform shape does not change. However, in the case of a logarithmic amplifier, the output amplitude is determined according to the amplitude of each of the waveforms.
As shown in, the waveform shape itself changes. As a result, since the head portion of the detected waveform (actually, the level is considerably lower than the peak) is emphasized more, the head portion of the waveform is easily detected by the comparator level 46, as mentioned above. In fact, in the conventional configuration, since the level of the leading portion is very small with respect to the dynamic range of the circuit, it is difficult to set the comparator level 46 at a stable small value and detect the leading portion. However, by performing logarithmic amplification, by emphasizing and amplifying the leading portion, that is, a small signal level, the tp signal 4
This means that it is easy to bring the detection points of 5 to the vicinity of the head portion with respect to the detected waveform.

Further, consider the tg signal 43. In FIG. 4, the tg signal is up to the peak of the envelope of the detected waveform. However, when it is desired to bring the tg signal earlier on the time axis, it is configured up to the inflection point in the front part of the envelope of the waveform. If logarithmic amplification is performed at this time, it is easily inferred that the inflection point of the envelope comes further ahead because the detected waveform is deformed as shown in FIG. That is, the logarithmic amplification process of the tg signal also brings the detection point near the beginning.

However, simply bringing the detection point forward causes a new problem. Since the frequency component of the detection signal at the detection point changes depending on the distance between the vibration pen 3 and the vibration sensor 6, the coordinate detection accuracy deteriorates. That is, the plate wave used has the characteristic that both the phase velocity and the group velocity have different values depending on the frequency of the wave (called dispersiveness), and therefore the detection waveform detected by the sensor. Depends on the distance between the vibrating pen and the sensor. That is, the farther the distance between the vibrating pen and the sensor, the wider the difference in the arrival time of the higher frequency component and the lower frequency component of the propagating wave at the sensor.

In the case of the asymmetric mode of the plate wave, the higher the frequency, the faster the speed tends to reach the sensor, so that the sensor arrives earlier and the lower component reaches the sensor later. Looking at this with the detection waveform on the time axis, the higher the frequency component, the earlier the frequency component appears on the time axis, and the lower one appears later as the distance increases. This phenomenon does not occur if only waves of a single frequency are propagated, but it is technically difficult in reality. For this reason, if the specific point from which the delay time is extracted from the detected waveform is near the peak of the detected waveform, wave information of a constant frequency (average value of the frequency components of the entire waveform) is always obtained, but the specific point is the peak. The farther away from, the frequency of the wave at the detection point changes drastically according to the distance between the vibrating pen and the sensor.

Therefore, in the present invention, the process of extracting only a single frequency component from the detected waveform is performed by the bandpass filter 9 before the logarithmic amplification. Since the weaker signal in front of the detected waveform is detected as the leading portion is detected, it is preferable that the band pass filter 9 has a narrow band. With a twin-T type bandpass filter or a surface wave filter, a filter having Q = 50 or more can be easily obtained.

Further, in the above embodiment, the configuration of the coordinate position calculation using the tp signal and the tg signal is shown, but the configuration of the coordinate position calculation using only the tp signal or only the tg signal is also possible. Since the required tp and tg signals are the same, they can be configured in the same manner as this embodiment.

As is clear from the above, the coordinate input device of this embodiment takes out only a single frequency component from the signal detected by the sensor 6 by the bandpass filter, and performs logarithmic amplification processing on the taken out signal by the logarithmic amplifier. By performing the waveform processing after the correction, it is possible to accurately calculate the arrival delay time without being affected by the level of the detection level, and based on this, highly accurate coordinate detection can be performed. Furthermore, it is possible to calculate the delay time near the beginning of the detected waveform on the time axis, eliminating erroneous detection and reduction in detection accuracy due to the influence of the reflected wave from the end face of the transmission plate, and thus the vibration transmission plate and thus the device shape. Can provide a small device.

The present invention may be applied to a system composed of a plurality of devices or an apparatus composed of a single device. Further, it goes without saying that the present invention can be applied to the case where it is achieved by supplying a program to a system or an apparatus.

[0055]

As described above, the coordinate input device according to the present invention can be made compact and can detect coordinates with high accuracy.

[Brief description of drawings]

FIG. 1 is a schematic explanatory diagram of a coordinate input device.

FIG. 2 is a schematic explanatory diagram of a vibrating pen.

FIG. 3 is a block diagram showing a configuration of an arithmetic control circuit.

FIG. 4 is a timing chart of signal processing.

FIG. 5 is a block diagram showing a configuration of a vibration waveform detection circuit.

FIG. 6 is an explanatory diagram for calculating coordinate positions.

FIG. 7 is a configuration diagram of a logarithmic amplifier.

FIG. 8 is an input / output characteristic diagram of a logarithmic amplifier.

FIG. 9 is a schematic explanatory diagram of characteristics of a logarithmic amplifier.

[Explanation of symbols]

 1 operation control circuit, 2 vibrator drive circuit, 3 vibrating pen, 6 vibration sensor, 8 vibration transmission plate, 9 band pass filter, 10 logarithmic amplifier, 11 signal waveform detection circuit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsuyuki Kobayashi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Yuichiro Yoshimura 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Within the corporation

Claims (2)

[Claims] 1. A plurality of vibration sensors are arranged on a coordinate input surface for propagating vibration, and the distance between each of the coordinate indicating tools that generate vibration and the sensor is measured from the arrival time of the vibration, and the coordinate indicating tools. Is a coordinate input device for calculating and outputting a designated point on the coordinate input surface as a coordinate value, the signal generating unit generating a signal based on the vibration detected by the vibration sensor, and the signal generating unit generating the signal. And means for logarithmically amplifying the signal, and means for determining that the logarithmically amplified signal has reached a predetermined level, from when vibration is generated by the indicator until the time when the predetermined level is reached. The coordinate input device is characterized in that the distance is measured with the arrival time of vibration as. 2. The coordinate input device according to claim 1, wherein the signal generating means includes means for filtering a predetermined frequency component from the output signal of the vibration sensor.