JPH0683520A - Coordinate input device - Google Patents

Abstract

PURPOSE:To prevent the accuracy of a coordinate position from being lowered by reflected waves. CONSTITUTION:When any vibration is inputted in an effective area A on a vibration transmission board 8, an arithmetic operation/control circuit 1 compares delay time from vibration source of vibrations detected by sensors 6a-6d and among areas Aa-Ad, the area adjacent to the sensor having the shortest delay time is judged as the area where the vibration is inputted. When the vibration from the judged area is reflected by a vibration-proof member and detected by the respective sensors, the coordinate position of the vibration source is calculated based on the vibrations detected by the remaining sensors excepting the sensor which most enlarges the incidental/emitting angle of reflection, namely, which detects a lot of reflected waves.

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, and more particularly to a coordinate input device for detecting vibrations generated by a vibrating pen by a vibration sensor provided on a vibration transmission plate to detect designated coordinates of the signal pen. It is a thing.

[0002]

2. Description of the Related Art Generally, in this type of device, the time required for the vibration generated from a vibrating pen to reach each vibration sensor provided at a predetermined position of a vibration transmission plate is measured.
The distance between the vibration pen and each vibration sensor,
As a result, the pointing coordinates by the vibrating pen were calculated.

By the way, the signal detected by the vibration sensor is not only a direct wave component generated from the vibrating pen and propagating and reaching the vibration sensor directly, but also a signal which is once reflected by the end face of the vibration transmitting plate and then reaches the vibration sensor. There is a wave component. It is necessary to reduce the influence of the unnecessary reflected wave component, because the components other than the direct wave component necessary for the coordinate calculation are unnecessary and the coordinates are calculated erroneously. Therefore, first, in order to suppress the level of the reflected wave, a structure is adopted in which a vibration isolator is attached near the end surface of the vibration transmission plate to attenuate the reflected wave.

Further, there is also one system in which the direct wave and the reflected wave are temporally separated so that they are not affected by the reflected wave when the direct wave is detected. Specifically, it is a method of enlarging the outer shape of the vibration transmission plate or moving the sensor away from the effective area for the coordinate input possible area (hereinafter referred to as the effective area). The input device itself becomes large.

Further, even when the vibration isolator is mounted, it is necessary to secure a sufficient width of the vibration isolator to damp the vibration, and it is naturally limited to bring the outer shape of the vibration transmission plate close to the effective area. There is.

Another method for reducing the influence of the reflected wave is that the reflected wave has the same time delay as the direct wave,
If the direct wave is detected before the vibration waveform in terms of time in which the direct wave and the reflected wave do not overlap, the same effect as the method of temporal separation can be obtained. In other words, this is a method of calculating coordinates from the delay time near the rising edge of the direct detection wave on the time axis.

As another conventional technique, one more vibration sensor than the number required to calculate the coordinates is arranged, the sensor to be used for the coordinate calculation is selected, and one less sensor is arranged. There is a method to find the coordinates. This is a configuration in which the sensor farthest from the coordinate designated position is excluded, and the purpose is S / S except for those with a low sensor detection level.
It was to secure N.

[0008]

In order to reduce the influence of the reflected wave, even if a vibration isolator is attached and a direct wave is detected on the front side of the vibration waveform on the time axis, the outer shape of the coordinate input device is adjusted. If the size is further reduced, the influence of reflected waves cannot be avoided. The first problem is the increase of the influence of the reflected wave when the coordinate is designated by the vibrating pen near the frame of the effective area. As the device becomes smaller, the effective area approaches the vibration isolator, so that the incident angle of the reflected wave reflected from the vibration pen interface at the vibration isolator and reaching the sensor becomes larger. When the incident angle becomes large and approaches 90 ^° , the reflectance at the vibration-proof material mounting interface approaches 1, so the level of the reflected wave increases, and erroneous detection of coordinates due to the influence of the reflected wave becomes a problem.

This problem becomes noticeable because the reflection angle becomes larger as the distance from the pen pointing position to the sensor is longer and the pen pointing position is closer to the effective area frame (closer to the vibration isolator).

The present invention has been made in view of the above-mentioned conventional example, and an object of the present invention is to provide a coordinate input device which prevents a decrease in the accuracy of coordinate detection due to a reflected wave.

[0011]

[Means for Solving the Problems] and

In order to achieve the above object, the coordinate input device of the present invention has the following structure. Based on the delay time until the elastic wave vibration input to the rectangular vibration transmission plate is detected from the vibration source by at least three vibration sensors arranged on the vibration transmission plate, the vibration on the vibration transmission plate is detected. A coordinate input device for calculating a coordinate position of a vibration source, wherein the means for determining the approximate position of the vibration source based on the vibration detected by each of the vibration sensors, and the vibration based on the approximate position of the vibration Of the sensors, a determination unit that determines the vibration sensor that receives the vibration reflected by the end surface of the vibration transmission plate with the largest incident angle and the largest emission angle, and a vibration sensor that excludes the vibration sensor that is determined by the determination unit. And means for calculating the coordinates of the vibration source based on the detected delay time of the vibration.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the structure of a coordinate input device in this embodiment. In the figure, 1 controls the entire apparatus,
It is an operation control circuit for calculating the coordinate position. Reference numeral 2 denotes 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. Coordinates are input by the vibration pen 3 by touching the vibration transmission plate 8. That is, by designating the inside of the area (hereinafter referred to as the effective area) indicated by the solid line A in the drawing with the vibrating pen 3, the vibration generated by the vibrating pen 3 is incident on the vibration transmitting plate 8 and measured and processed. By doing so, the position coordinates of the vibrating pen 3 can be calculated.

In order to prevent (reduce) the propagating wave from being reflected at the end surface of the vibration transmitting plate 8 and returning to the central portion, the vibration isolator 7 is provided on the outer periphery of the vibration transmitting plate 8. As shown in FIG. 1, a vibration sensor 6a for converting mechanical vibration into an electric signal, such as a piezoelectric element, is provided near the inside of the vibration isolator as shown in FIG.
6d is fixed. Reference numeral 9 denotes a signal waveform detection circuit that outputs a signal in which vibration is detected by each of the vibration sensors 6a to 6d to the arithmetic control circuit 1. Reference numeral 11 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 10, it is possible to display a dot at a position traced by the vibrating pen 3 and 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, by setting the vibration frequency of the vibrator 4 to the resonance frequency including the pen tip 5, it is possible to perform efficient 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 and obstacles on the surface of the vibration transmission plate as compared with surface waves. .

In the above-mentioned configuration, the arithmetic control circuit 1 outputs a signal for driving the vibrator driving circuit 2 and the vibrator 4 in the vibrating pen 3 at every predetermined cycle (for example, every 5 ms), and the internal timer thereof. Starts timing (by a counter). Then, the vibration generated by the vibrating pen 3 propagates on the vibration transmission plate 8 and the vibration sensors 6a to 6d.
It arrives after a delay according to the distance. The signal waveform detection circuit detects the signals from the vibration sensors 6a to 6d and generates a signal indicating the vibration arrival timing at each vibration sensor by the waveform detection processing described later. By inputting this signal, each vibration sensor 6a-6a
The vibration arrival time up to d is detected, and the sensor with the shortest arrival delay time is determined. According to the judged sensor,
The combination of sensors used for coordinate calculation is selected, and the coordinate position of the vibration pen is calculated using the vibration transmission delay time up to three sensors. For example, when 6a is determined to be the sensor with the shortest delay time, the delay times up to three sensors 6a to 6c are used.

Further, the arithmetic control circuit 1 uses the calculated position information of the vibrating pen 3 to display the drive circuit 10.
To control the display on the display 11 or output coordinates to an external device by serial or parallel communication.

<Description of Coordinate Calculation Process Flowchart> FIG. 2 shows a flowchart of the sensor selection process performed by the arithmetic control circuit 1.

First, the data of the respective vibration arrival delay times Ta to Td of the four sensors 6a to 6d are fetched (S21). These four data are compared and the smallest value is selected (S22). As a result, the vibrating pen 3 among the areas Aa to Ad obtained by dividing the effective area A in FIG.
This limits which area is designated.

Next, according to the selected sensor, the process proceeds to each coordinate calculation routine (S23 to S26). The coordinate calculation routine uses the vibration arrival delay time of the three sensors to perform coordinate calculation calculation, which will be described later. 3 out of 4 sensors
There are four combinations for selecting the individual, and one of them is selected as a combination corresponding to each selected sensor. Specifically, when the sensor 6a, that is, the area Aa, is input, the three sensors except the sensor 6d are used, and similarly, when the area Ab is 6c, when Ac is 6b, A
6a is excluded when d. Finally, the coordinate data obtained by the calculation is converted into the coordinate system output from the coordinate input device, and the coordinate calculation process is completed (S27).

By the way, if the sensor position is set at the apex of a rectangle, no matter which combination of sensors is selected, two of the line segments connecting the three sensors are orthogonal to each other.
The method of obtaining the origin in the Cartesian coordinate system using the axis is the same. Therefore, the coordinate calculation routine may be shared, and when the coordinate conversion of the output of the coordinate input device to the coordinate system is performed thereafter, the parameters may be converted using the parameters according to the selected sensor.

The reason why the coordinate calculation is performed by removing one of the four vibration sensors will be described. FIG. 3 shows a model explanatory diagram of a reflected wave when the pen coordinate is designated near the frame of the effective area A.

A broken line shows a propagation path of a reflected wave reflected by the mounting surface of the vibration isolator 7 to the sensor. The sound wave incident on the vibration isolator 7 at the incident angle θ is divided into a component that travels inside the vibration isolator and a component that is reflected by the vibration isolator. The reflectance is a value obtained by dividing the reflected energy component by the total energy of the original sound wave. Since the acoustic damper has a larger acoustic impedance than the unattached portion, the reflectance increases as the incident angle increases, and the reflectance becomes 1 at a certain incident angle (called a critical angle) or more. That is, with respect to the level of the direct wave that reaches the sensor 6 directly from the vibrating pen 3, the difference in level of the reflected wave becomes smaller as the incident angle becomes larger, so that erroneous detection due to the influence of the reflected wave becomes a serious problem.

As is clear from FIG. 3, the incident angle increases as the distance between the sensor and the pen increases. It is possible to specify the pen pointing position where the incident angle of the reflected wave component with respect to the vibration proof material with respect to an arbitrary sensor becomes large in the effective area. Further, in the case of the arrangement of four sensors as shown in FIG. 1, it is almost uniquely determined that one sensor has the largest incident angle in an arbitrary region. In Figure 1,
Since the effective area A is rectangular and the distance between the effective area frame on the short side and the sensor is large, even if the side is specified near the short side frame, two sensors closer to the specified position can be reached. The incident angle of the reflected wave is not so large. Therefore, when the pen is instructed near the long side frame of the effective area, only the influence of the reflected wave on the sensor near the long side frame and having a longer distance from the pen can be said to be a problem. Specifically,
When the pen points the coordinates in the frame on the long side of the area Ad,
The influence of the reflected wave on the vibration sensor 6a is adversely affected by the 6d sensor in the long side frame of the area Aa, the 6c sensor in the long side frame of the area Ab, and the 6b sensor in the long side frame of the area Ac. There is no problem because the incident angle of the reflected wave component on the vibration isolator is small both in the short side frame and inside the frame that is not near the frame.

That is, the influence of the reflected wave is particularly problematic in the vicinity of the effective area frame where the incident angle of the reflected wave is large.
Since it does not pose a problem in other positions,
This problem is solved unless the sensor is divided into four areas and one sensor is used for each area.

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

FIG. 4 is a diagram for explaining a detected waveform input to the signal waveform detection circuit 9 and a vibration transmission time measuring process based on the detected waveform. In the following, the vibration sensor 6a will be described, but the other vibration sensors 6b, 6c,
The same is true for 6d.

It has already been described that the measurement of the vibration transmission time to the vibration sensor 6a is started at the same time as the output of the start signal to the vibrator drive circuit 2. At this time, the drive signal 41 is applied from the vibrator drive circuit 2 to the vibrator 4. The ultrasonic vibration transmitted from the vibration pen 3 to the vibration transmission plate 8 by the signal 41 progresses for a time corresponding to the distance to the vibration sensor 6a, and then is detected by the vibration sensor 6a.

The signal 42 shown in the figure represents the signal waveform detected by the sensor 6a. Since the vibration used in this embodiment is a plate wave, the relationship between the envelope 43 of the detected waveform and the phase 42 with respect to the propagation distance in the vibration transmission plate 8 is:
It changes according to the transmission distance during vibration transmission. here,
The traveling velocity of the envelope 43, that is, the group velocity is Vg, and the phase velocity of the phase 422 is Vp. This group velocity V
The distance between the vibration pen 3 and the vibration sensor 6a can be detected from g and the phase velocity Vp.

First, focusing only on the envelope 43, its speed is Vg, and when a point on a certain specific waveform, for example, an inflection point or a peak like 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, it is given by d = Vg · tg (1). This formula relates to one of the vibration sensors 6a, but the other three vibration sensors 6b are represented by the same formula.
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. A time from a specific detection point of the phase waveform signal 42, for example, vibration application to a zero cross point after a certain predetermined signal level 431 is t.
p'47 (obtained by generating a window signal 46 of a predetermined width from the time when it exceeds the level 431 and comparing it with the phase signal 42)
Then, the distance between the vibration sensor and the vibration pen is d = n · λp + Vp · tp (2). 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. The distance between the vibration pen 3 and the vibration sensor 6a can be accurately measured by substituting the determined n into the equation (2). By the way, what is actually measured by the signal waveform detection circuit 9 is tg ′ and tp ′ that include the offset of the delay time inside the vibrating pen or in the circuit, but they are substituted into the equations (2) and (3). In doing so, it is necessary to subtract the offset amount and restore it to tg and tp. The signals 45 and 47 are generated by the signal waveform detection circuit 9 for measuring the two vibration transmission times tg 'and tp' described above. The signal waveform detection circuit 9 is configured as shown in FIG. .

FIG. 5 is a block diagram showing the configuration of the signal waveform detection circuit 9 of this 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 inflection point is determined by the envelope inflection point detection circuit 5
3 detected. In the peak detection circuit, a signal tg ′ (signal 45 in FIG. 4), which is an envelope delay time detection signal of a predetermined waveform, is formed by the tg signal detection circuit 54 composed of a mono multivibrator or the like, and the arithmetic control circuit 1
Entered in.

On the other hand, 55 is a signal detection circuit, which is the envelope signal 43 detected by the envelope detection circuit 52.
A pulse signal 47 of a portion exceeding a threshold signal 431 of a predetermined level is formed. 56 is a monostable multivibrator, which opens the gate signal 46 of a predetermined time width triggered by the first rising edge of the pulse signal. Reference numeral 57 denotes a tp comparator, which detects the first rising zero-cross point of the phase signal 42 while the gate signal 46 is open, and supplies the phase delay time signal tp47 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.

<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, based on the principle described above, it is possible to obtain the respective linear distances from the position P of the vibrating pen 3 to the positions of the respective vibration sensors 6a to 6d. Furthermore,
From the three distance data obtained by removing one from the four distance data, it can be obtained from the theorem of the coordinate 3 square of the position P of the vibrating pen 3.

In FIG. 6, a relative coordinate value is calculated with the sensor position arranged in S1 as coordinates (0, 0), the sensor direction of the position of S2 as the x-axis, and the direction of S3 orthogonal thereto as the y-axis. There is. The relative coordinate value can be obtained as in the following equation.

X = X / 2 + (d1 + d2) (d1-d2) / 2X (4) y = Y / 2 + (d1 + d3) (d1-d3) / 2Y (5) where X and Y are S2 and S3. It is the distance between the position vibration sensor and the sensor at the origin (0,0). Further, the relative coordinates can be easily converted into absolute coordinates which are the output of the coordinate input device.

According to the equations (4) and (5), the sensor position S
The relative position can be obtained by the coordinate system with 1 as the coordinate origin,
The sensor position S1 can be a sensor 6a-6d, which translates it into a uniform coordinate representation. For example, consider converting a relative coordinate value into a coordinate value with the sensor 6a as the origin. It should be noted that the coordinate axes of the relative coordinate system with each sensor as the origin are taken to have the long side of the diaphragm 8 as the x-axis and the short side as the y-axis.

In the case of a coordinate system having the sensor 6b as the origin, it is not necessary to convert the x component of the coordinate. For the y component, a value obtained by subtracting the value y calculated by the equation (5) from the value Y is set as a new y component. That is, the new coordinates after conversion are (x ', y')
Then, the coordinates can be converted by x ′ = xy ′ = Y−y.

In the same manner, if the origin is the sensor 6c, x '= X-xy' = Y-y, and if the origin is 6d, x '= X-xy' = y. In this way, the relative coordinate values can be expressed by the unified coordinate system by a simple conversion.

As described above, the coordinate calculation is performed by the remaining sensors excluding the sensor in which the incident angle of the reflected wave component on the vibration isolator mounting interface becomes large. The position coordinates of the vibrating pen 3 can be stably and accurately detected in real time without being affected by waves.

[0045]

[Other Embodiments] In the above-described embodiment, the coordinate calculation is performed by selecting three sensors having less influence of reflection among the four sensors according to the area, and selecting two sensors according to the area. The coordinates may be calculated. In FIG. 1, when the pen instruction is made in the areas Aa and Ad, the sensors 6b and 6c are selected, and Ab
And Ac select 6a and 6c. In the coordinate calculation formula,
(4) is used as it is, and the y coordinate is obtained from the following equation using x obtained in (4).

Y = sqrt (d1 ² −x ² ) (6) sqrt (x): square root of x Further, although the four sensor configuration has been described, five or more sensors are arranged to divide the region. Needless to say, the configuration may be such that, for each region, the remaining sensors excluding the sensor having a large incident angle of the reflected wave are selected and the coordinates are calculated from the vibration arrival delay time detected by the selected sensor.

Further, in the above-described embodiment, the sensor having the shortest vibration arrival delay time is detected for the area determination.
Even if the sensor with the longest delay time is sought, it is possible to specify the area of the pen pointing position. Also, the same effect can be obtained by determining the area in which the vibration is input based on the magnitude of the vibration detection level instead of the vibration arrival delay time.

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.

[0049]

As described above, the coordinate input device according to the present invention has an effect that it is possible to prevent a decrease in the accuracy of coordinate detection due to a reflected wave.

[Brief description of drawings]

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

FIG. 2 is a flowchart of a coordinate calculation processing program.

FIG. 3 is an explanatory diagram of an incident angle of a reflected wave component near the effective area frame.

FIG. 4 is a timing chart of signal processing.

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

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

[Explanation of symbols]

 1 ... Arithmetic control circuit, 3 ... Vibration pen, 6 ... Vibration sensor, 9 ... Signal detection circuit, A ... Effective area.

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

Claims (5)

[Claims] 1. An elastic wave vibration input to a rectangular vibration transmission plate is detected based on a delay time from the vibration source to detection by at least three vibration sensors arranged on the vibration transmission plate. A coordinate input device for calculating the coordinate position of a vibration source on a vibration transmission plate, wherein the means for determining the approximate position of the vibration source based on the vibration detected by each of the vibration sensors, and the approximate position of the current vibration. On the basis of the vibration sensor, a determination unit that determines the vibration sensor that receives the vibration reflected by the end surface of the vibration transmission plate with the largest incident angle and the largest emission angle, and the vibration sensor that is determined by the determination unit. A coordinate input device comprising: means for calculating coordinates of the vibration source based on a delay time of vibration detected by the excluded vibration sensor. 2. The vibration sensor is provided on the vibration transmission plate.
One of each of the vibration sources is provided at each corner, and the approximate position of the vibration source is one of four regions divided by a line that divides the vibration transmission plate into upper and lower parts and left and right parts. Of the four vibration sensors, the vibration generated from the vibration source at the substantially position is reflected by the end surface of the vibration transmission plate, and a reflected wave detected by the vibration sensor is applied to the end surface of the vibration transmission plate. The one vibration sensor having the maximum incident angle is determined, and the coordinates of the pen pointing position are calculated using signals detected by three sensors excluding the vibration sensor. Coordinate input device. 3. The vibration sensor is provided on the vibration transmission plate.
One of each of the vibration sources is provided at each corner, and the approximate position of the vibration source is one of four regions divided by a line that divides the vibration transmission plate into upper and lower parts and left and right parts. Of the four vibration sensors, the vibration generated from the vibration source at the substantially position is reflected by the end surface of the vibration transmission plate, and a reflected wave detected by the vibration sensor is applied to the end surface of the vibration transmission plate. The one vibration sensor having the maximum incident angle is determined, two adjacent vibration sensors are selected from the three sensors excluding the vibration sensor, and the signals detected by the selected two vibration sensors are selected. The coordinate input device according to claim 1, wherein the coordinates of the pen pointing position are calculated by using. 4. The means for determining the approximate position of the vibration source comprises:
The elastic wave vibration from the vibration source is determined based on a delay time of reaching the vibration sensor.
The coordinate input device described. 5. The means for determining the approximate position of the vibration source comprises:
The coordinate input device according to claim 1, wherein the determination is performed based on energy of elastic wave vibration from the vibration source detected by the vibration sensor.