JPH10320103A - Coordinate input device - Google Patents

Abstract

(57) [Problem] To provide a coordinate input device capable of detecting coordinates with high accuracy regardless of the input attitude of an oscillation source. SOLUTION: A plate wave vibration from a vibration oscillation source 3 is detected by a plurality of vibration sensors 6a to 6d 'provided on a vibration transmission plate 8, and a position coordinate of the oscillation source is detected based on the vibration transmission time. Vibration sensor 6a provided on the surface of vibration transmission plate 8
To 6d detect the asymmetric wave of the vibration wave with high sensitivity, and the vibration sensors 6a 'to 6d' provided on the side face detect the symmetric wave with high sensitivity. Since the amplitudes of the symmetrical and asymmetrical waves change depending on the position of the oscillation source, by detecting this, one of the vibration sensors is selected according to the position of the oscillation source, and the transmission of the plate wave detected by the selected sensor is performed. The coordinate calculation is performed at the speed. With such a configuration, highly accurate coordinate input is possible regardless of the input attitude of the oscillation source with respect to the vibration transmission plate.

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 a coordinate of a designated point from a vibration transmission time of an elastic wave vibration input from an oscillation source onto a vibration transmission plate. It is.

[0002]

2. Description of the Related Art Conventionally, there has been known a coordinate input device in which a vibration pen having a built-in piezoelectric element or the like in a vibration transmission plate is used to input vibration and a plurality of sensors provided on the vibration transmission plate detect coordinates of an input point. I have.

A conventional coordinate input device for detecting vibration propagating through a plate-shaped vibration transmission plate is often used mainly as a handwriting input device for a portable or desktop device, or as a pointing device. Therefore, the angle of the vibrating pen with respect to the vibration transmitting plate, which is the input plate, of the vibrating pen is relatively perpendicular to the vibration transmitting plate 8 as shown in FIG. Hardware and software have also been developed for use at different angles. However, when considering the coordinate input device not for personal use but for a whiteboard size for a presentation such as a meeting, the person who inputs the coordinates basically faces the audience and displays the body as much as possible. In order not to block the vibration, it is necessary to make the pointer (vibrating pen, pointing stick) considerably bounce against the vibration transmitting plate. When this is performed by a conventional coordinate input device, the angle of the vibrating pen 3 'is as shown in FIG.

[0004]

However, as described above, vibration input is performed by a vibration pen having a built-in piezoelectric element or the like in a conventional vibration transmission plate, and coordinates of an input point are detected by a plurality of sensors provided on the vibration transmission plate. In the coordinate input device for detecting the vibration pen 3 ′, it is not assumed that the vibration pen 3 ′ is used at an angle lying on the vibration transmission plate 8 as shown in FIG.
As is clear from the figure, there is a limit to the angle at which the vibrating pen can be laid down in order for the vibrating pen to come into contact with the vibration transmitting plate and transmit the vibration from the shape of the vibration pen. Further, strictly speaking, in the conventional coordinate input device for detecting vibration, there is a disadvantage that a large angle of the vibration pen causes a coordinate detection error. This is because, in the coordinate input device that detects the vibration, the plate wave is detected, but the plate wave is physically affected by the incident angle of vibration, which differs depending on the vibration mode, and the detected vibration amplitude fluctuates. This is caused by deformation of the detected vibration waveform.

Specifically, for example, in a conventional coordinate input device for detecting vibration by mounting a vibration sensor on the surface of a vibration transmission plate, a relatively vibrating pen is set up (around 90 ° vertically).
In the case of inputting, the fundamental mode of the asymmetric wave mode of the plate wave (hereinafter referred to as A0 wave) is mainly detected. However, even in the conventional device, if the angle is tilted to about 45 °, the ratio of the detected waveform amplitude of the fundamental mode (hereinafter referred to as S0) of the symmetric wave mode of the plate wave to the detected waveform amplitude of the A0 wave increases, and the cause of the erroneous detection is increased. Had become. Therefore, in the configuration in which the pointer (vibrating pen, pointing stick), which is the main object of the present invention, is considerably laid on the vibration transmitting plate, the S0 wave becomes considerably large, and the conventional simple single wave In a configuration that detects only the A0 wave (or the S0 wave depending on the vibration sensor configuration), there is a problem that a detection error occurs and the accuracy is reduced.

Accordingly, the present invention has been made to solve such a problem, and has as its object to provide a coordinate input device capable of detecting coordinates with high accuracy regardless of the input attitude of an oscillation source. I do.

[0007]

In order to solve the above-mentioned problems, according to the present invention, a plate wave vibration from a vibration oscillation source is detected by a plurality of vibration sensors provided on a vibration transmission plate, and the oscillation is transmitted based on the vibration transmission time. In a coordinate input device for detecting a position coordinate of a source, means for discriminating plate wave vibrations having different vibration modes generated from the oscillation source and transmitting the vibration transmission plate, and means for selecting a vibration mode from the discriminated plate wave vibrations And means for calculating the position coordinates of the oscillation source based on the vibration transmission of the selected vibration mode.

In such a configuration, the vibration mode of the plate wave vibration which is dominant according to the input attitude of the oscillation source is selected.
Since the position coordinates of the oscillation source are calculated based on the vibration transmission time and the transmission constant of the selected vibration mode, not only when the angle of the oscillation source such as the vibration pen and the pointing rod is laid down on the vibration transmission plate, For an application in which the incident angle of the oscillation source widely varies from vertical (90 °) to lying down (0 °), it is possible to provide a coordinate input device that does not cause an error. Therefore, it is possible to provide a highly accurate coordinate input device even in applications such as presentation of a large-sized conference or the like, in which there are many opportunities to input a vibration pen (pointing rod) with respect to the vibration transmission plate.

[0009]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

(First Embodiment) FIG. 1 is a diagram best representing the features of the structure of a coordinate input device according to this embodiment. In the figure, reference numeral 1 denotes an arithmetic control circuit which controls the entire apparatus, calculates a coordinate position, and further controls the timing of capturing a delay time at the time of setting a reference point, which is a feature of the present invention. Reference numeral 2 denotes a vibrator drive circuit which vibrates a substantially spherical pointing member 5 in the pointing rod 3 via the vibrator 4. Reference numeral 8 denotes a vibration transmission plate made of a transparent member such as an acrylic or glass plate. The coordinate input by the pointing rod 3 is performed by touching the vibration transmission plate 8. The pointing member 5 does not have a pointed tip shape like the tip of a conventional vibrating pen, and has a substantially spherical shape, which is almost parallel to the vibration transmission plate 8. Even when laid at a low angle (0 °),
This is to enable coordinate input.

A vibration isolator 7 is provided on the outer periphery of the vibration transmitting plate 8 to prevent (reduce) the reflected vibration from returning to the central portion. Eight vibration sensors 6a to 6d 'such as piezoelectric elements for converting mechanical vibration into electric signals are arranged and fixed at the corners. These vibration sensors 6 a to 6 d ′ are mounted on the four corners of the vibration transmission plate 8, two at the same location, one on the surface of the vibration transmission plate 8, and one on the side surface of the vibration transmission plate 8. You. The details will be described later. A in the drawing is an effective area for inputting coordinates.

The output signals from the vibration sensors 6a to 6d 'are sent to a preamplifier circuit (not shown) provided near the vibration sensors 6a to 6d' as shown in FIG. The amplified outputs are sent to the signal waveform detection circuit 9, respectively. Further, signals of the signal waveform detection circuit 9 corresponding to the respective vibration sensors 6a to 6d 'are sent to the arithmetic and control circuit 1 to perform coordinate calculation.

Reference numeral 11 denotes a liquid crystal display and a display capable of displaying in units of dots, such as a projection display, or the like.
It is a CRT and its projection type display, etc., and is arranged behind the vibration transmission plate. The display drive circuit 10 drives the display at the position traced by the pointing rod 3 so that the display can be seen through the vibration transmission plate 8 (made of a transparent member). The display may be a device such as a PDP as long as it has a large whiteboard size, and may not necessarily be integrated with the display depending on the use of the product.

The vibrator 4 built in the pointing rod 3 is driven by a vibrator driving circuit 2 also built in the pointing rod 3, as shown in FIG. The drive signal of the vibrator 4 is supplied as a low-level pulse signal from the arithmetic and control circuit 1, amplified by a predetermined gain by the vibrator drive circuit 2 stored in the pointing rod 3, and then applied to the vibrator 4. In addition,
The vibrator drive circuit 2 may be provided at another position without being stored in the pointing rod 3 as shown in FIG. The electric drive signal is converted into mechanical ultrasonic vibration by the vibrator 4 and transmitted to the vibration transmission plate 8 via the pointing member 5.

Here, the vibration frequency of the vibrator 4 is selected to a value that can generate a plate wave on the vibration transmission plate 8 such as glass. In addition, when the vibrator is driven, a mode of vibrating in the vertical direction in FIG. Also,
By setting the vibration frequency of the vibrator 4 to the resonance frequency including the pointing member 5, efficient vibration conversion is possible.

The elastic wave transmitted to the vibration transmission plate 8 as described above is a plate wave, and has an advantage that the surface of the vibration transmission plate is less susceptible to scratches, obstacles, and the like than surface waves. However, there is a problem that the detected vibration amplitude of the A0 wave and the S0 wave varies depending on the vibration incident angle.

<Description of Arithmetic Control Circuit> In the above-described configuration, the arithmetic control circuit 1 operates at predetermined intervals (for example, 5 ms).
The vibrator 4 in the indicator rod 3 via the vibrator drive circuit 2
, And starts time keeping by its internal timer (constituted by a counter). The vibration generated from the pointing rod 3 is transmitted to the vibration sensor 6.
It arrives with a delay according to the distance from a to 6d '.

The signal waveform detection circuit 9 includes the vibration sensors 6a to 6a.
The signal from 6d 'is detected, and one of the two sets of vibration sensors at one location, that is, 6a-
6d or 6a 'to 6d', and generates a signal indicating the timing of arrival of the vibration at each vibration sensor. The arithmetic and control circuit 1 outputs the signal of each of the vibration sensors 6a to 6d or 6a 'to 6d'. Is input, the arrival time of the vibration to each vibration sensor (details will be described later) is detected, and the coordinate position of the indicator rod is calculated using the arrival time of the vibration of the vibration sensor. The selection by the waveform detection processing will be described later in detail.

The arithmetic and control circuit 1 drives the display drive circuit 10 based on the calculated position information of the pointing rod 3 to control the display on the display 11 or to an external device by serial or parallel communication. Output coordinates (not shown).

FIG. 3 is a block diagram showing a schematic configuration of the arithmetic and control circuit 1 according to this embodiment. Each component and its operation will be outlined below.

In the figure, reference numeral 31 denotes a microcomputer which controls the arithmetic control circuit 1 and the whole coordinate input device, and stores an internal counter, a ROM storing operation procedures, and values used for calculation and the like at the time of setting a reference point. It is composed of a RAM, a non-volatile memory for storing distance values related to setting of constants and reference points, and the like. In the present invention, since the distance is calculated based on the vibrations of the two modes (A0 wave and S0 wave) having different vibration transmission speeds, the constants of the respective vibration modes are also stored in advance as constants such as the vibration transmission speed. .

Reference numeral 33 denotes a timer (constituting, for example, a counter) for measuring a reference clock (not shown), which is used to start the driving of the vibrator 4 in the pointing rod 3 by the vibrator driving circuit 2. When a signal is input, the timing starts. As a result, the start of timing and the detection of vibration by the sensor are synchronized, and the delay time until vibration is detected by each vibration sensor can be measured.

Other circuits constituting each component will be described in order.

The vibration arrival timing signals from the vibration sensors 6a to 6d or 6a 'to 6d' output from the signal waveform detection circuit 9 are input to the latch circuits 34a to 34d via the detection signal input circuit 35. Is done.

Each of the latch circuits 34a to 34d includes
It corresponds to each of the vibration sensors 6a to 6d or 6a 'to 6d', and when a timing signal is received from the corresponding sensor, the time value of the timer 33 at that time is latched. Thus, each of the vibration sensors 6a to 6d or 6a 'to 6a
When the determination circuit 36 determines that the detection signals of all the vibration sensors have been received in d ′, it outputs a signal to the microcomputer 31 to that effect.

Here, the microcomputer 31 includes:
A signal from the changeover pen switch is input, and a select signal as a judgment changeover signal to the power supply control circuit and the judgment circuit 36 is output.

When the microcomputer 31 receives the signal from the determination circuit 36, the determination circuit 36 reads the vibration arrival time from the latch circuits 34a to 34d to the respective vibration sensors from the latch circuit, and performs a predetermined calculation. Then, the coordinate position of the pointing rod 3 on the vibration transmission plate 8 is calculated. Then, by outputting the calculated coordinate position information to the display drive circuit 10 via the I / O port 37, for example, a dot or the like can be displayed at a corresponding position on the display 11. Alternatively, by outputting the coordinate position information to the interface circuit via the I / O port 37, the coordinate value can be output to the external device.

<Description of Vibration Propagation Time Detection (FIGS. 4 and 5)
In the above, any one of the vibration arrival timing signals from the vibration sensors 6a to 6d or 6a 'to 6d' is selected by the waveform detection process before the measurement step of the vibration transmission delay time of the arithmetic and control circuit. An example in which the vibration transmission delay time is measured has been described. Hereinafter, the principle of measuring the vibration arrival time up to the vibration sensor will be described.

FIG. 4 is a diagram for explaining a detection waveform input to the signal waveform detection circuit 9 and a process of measuring a vibration transmission time based on the detection waveform. Hereinafter, the case of the vibration sensor 6a will be described, but the same applies to the other vibration sensors 6b to 6d '.

As described above, the measurement of the vibration transmission time to the vibration sensor 6a is started simultaneously with the output of the start signal to the vibrator drive circuit 2. At this time, the drive signal 41 is applied from the transducer drive circuit 2 to the transducer 4. The ultrasonic vibration transmitted from the indicator rod 3 to the vibration transmission plate 8 by the signal 41 advances over a time tg corresponding to the distance to the vibration sensor 6a, and is detected by the vibration sensor 6a. A signal indicated by reference numeral 42 indicates a signal waveform detected by the vibration sensor 6a.

Since the vibration used in this embodiment is a plate wave, the relationship between the envelope 421 and the phase 422 of the detected waveform depends on the propagation distance in the vibration transmission plate 8 during the transmission of the vibration. Will change accordingly. Here, the traveling speed of the envelope 421, that is, the group velocity is Vg, and the phase velocity of the phase 422 is Vp. The distance between the pointing rod 3 and the vibration sensor 6a can be detected from the group velocity Vg and the phase velocity Vp. However, in the case of the present invention, as described above, the group velocity Vg and the phase velocity Vp are different depending on the vibration mode, so that the vibration sensors 6a to 6d and 6
Different constants are used for tg and tp of a 'to 6d'.

First, focusing only on the envelope 421, its velocity is Vg. When a peak on a point on a specific waveform, for example, an inflection point or a signal shown by 421 'in FIG. The distance between the sensors 6a is given by d = Vg · tg (1), where tg is the vibration transmission time. This equation is for one of the vibration sensors 6a, but the same equation is used for the other three vibration sensors 6b.
6d or 6a 'to 6d', the distance to the pointing rod 3 can be similarly expressed.

Further, in order to determine coordinates with higher accuracy, processing based on detection of a phase signal is performed.

A signal 47 is formed in a region where the envelope signal 421 exceeds a certain predetermined signal level 46, and the window signal 44 corresponding to the signal 47 and the phase signal 422 are compared with each other, whereby a specific detection of the phase waveform signal 422 is performed. Assuming that a time from a point, for example, vibration application to a zero crossing point after the phase signal 422 enters the window signal 44 is tp (45),
The distance between the vibration sensor and the pointing rod is as follows: 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 = [(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 it is a change such as tg within ± 1/2 wavelength. By substituting n obtained as described above into equation (2), the distance between the indicator rod 3 and the vibration sensor 6a can be measured with high accuracy. The two vibration transmission times t described above
The generation of signals 43 and 45 for the measurement of g and tp is
This is performed by the signal waveform detection circuit 9. The signal waveform detection circuit 9 is configured as shown in FIG.

FIG. 5 is a block diagram showing a configuration of the signal waveform detection circuit 9 of the embodiment.

In FIG. 5, the output signal of the vibration sensor 6a is amplified by a preamplifier circuit 51 to a predetermined level. The amplified signal is filtered by a band-pass filter 511 to remove extra frequency components from the detection signal. The amplified signal is input to, for example, an envelope detection circuit 52 including an absolute value circuit and a low-pass filter. Only those are retrieved. The timing of the envelope peak is detected by the envelope peak detection circuit 53. 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 a tg signal detection circuit 54 composed of a monomultivibrator or the like, and input to the arithmetic and control circuit 1.

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

<Description of Circuit Delay Time Correction> The vibration transmission time latched by the latch circuit includes a circuit delay time et and a phase offset time toff.
The errors caused by these always include the same amount when the vibration is transmitted from the pointing rod 3 to the vibration transmission plate 8 and the vibration sensors 6a to 6d '.

Therefore, for example, from the position of the origin O in FIG.
For example, the distance to the vibration sensor 6a is R1 (= X / 2), an input is made at the origin O with the pointing rod 3, and the actually measured vibration transmission time from the origin O to the sensor 6a is tg.
Assuming that the true transmission times from the origin O to the sensor are tgz and tpz, the circuit delay time et and the phase offset toff are as follows: tgz ′ = tgz + et (4) tpz ′ = tpz + et + toff (5) ) There is a relationship.

On the other hand, an actual measurement value tg 'at an arbitrary input point P
Similarly, tp 'is expressed as tg' = tg + et (6) tp '= tp + et + toff (7) When the difference between (4) (6) and (5) (7) is obtained, tg′−tgz ′ = (tg + et) − (tgz + et) = tg−tgz (8) tp′−tpz ′ = (tp ′) + Et + toff) − (tpz + et + toff) = tp−tpz (9) The circuit delay time et and the phase offset toff included in each transmission time are removed, and the position of the sensor 6a between the position of the origin O and the input point P is set as a starting point. The difference of the true transmission delay time according to the distance can be obtained, and the above (2)
The distance difference can be obtained by using the equation (3).

Since the distance from the vibration sensor 6a to the origin O is stored in advance in a non-illustrated non-volatile memory or the like in the arithmetic and control circuit 1 and is known, the distance between the pointer 3 and the vibration sensor 6a can be determined. . The same applies to the other sensors 6b to 6d.

In the configuration of the present invention, the actually measured values tgz 'and tpz' at the origin O are stored in the memory as appropriate not only at the time of shipment but also at the time of using the product after shipment. Before calculating equation (3) (8) (9)
The formula is executed 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 transmitting plate 8 by the pointing rod 3 will be described with reference to FIG.

The coordinate calculation formula is calculated from the three-square theorem.

For example, three of the vibration sensors 6a, 6b, 6c
When the measurement is performed based on the signals from the three sensors, the linear distance d from the position P of the pointing rod 3 to the position of each of the vibration sensors 6a, 6b, 6c is based on the principle described above.
a, db, dc can be determined. Further, based on the linear distances da, db, dc, the arithmetic control circuit 1 can determine the coordinates (x, y) of the position P shown in FIG.

X = (da + db) · (da−db) / 2X (10) y = (da + dc) · (da−dc) / 2Y (11) where X and Y are distances between the vibration sensors 6a and 6b, respectively. , The distance between the vibration sensors 6a and 6c. Above, 6
The same applies to a ′ to 6d ′, but 6a to
If the vibration sensors 6a 'to 6d' cannot be mounted at exactly the same location as the vibration sensors 6d, the following calculation is performed based on the unique distance of the vibration sensors 6a 'to 6d'.

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

In the first embodiment, the arrangement of the vibration sensors is not limited to the above, and the total number of the vibration sensors may be appropriately adjusted according to the size of the vibration transmitting plate. If the number of vibration sensors used for coordinate calculation is two or more, the number is not limited to three, and the arrangement of the vibration sensors is not limited to the above. For example, all of the vibration sensors 6a to 6d may be used. Vibration sensor 4 at the center of the side used or arranged in a cross shape
It goes without saying that individual pieces may be used.

<Description of Vibration Mode Selection by Waveform Detection Process (FIGS. 7 to 10)> In order to explain the vibration mode selection by the waveform detection process of the present invention, the mounting position of the vibration sensor 6 on the vibration transmission plate 8 will be described below. The relationship between the amplitude and the sensitivity (sensitivity) of the detection wave in each vibration mode will be described. As schematically shown in FIG. 7, the asymmetric wave (A) mode of the plate wave is mainly a transverse wave, that is, the vibration amplitude in the thickness direction of the vibration transmission plate is large, and therefore, as shown in FIG. When the sensor 6 of the directional oscillator is mounted on the surface of the vibration transmission plate, the asymmetric wave A
Zero wave is detected with high sensitivity.

On the other hand, in the symmetric wave (S) mode, as schematically shown in FIG. 7, the longitudinal wave, that is, the vibration amplitude in the vibration transmitting direction of the vibration transmitting plate is large, so that the vertical ( When the sensor 6 of the (thickness) direction transducer is mounted on the side surface of the vibration transmission plate, the sensitivity of the asymmetric wave A0 decreases, and the detection sensitivity of the symmetric S0 wave increases. As actual detection vibrations, both the A0 wave and the S0 wave are detected with different sensitivities. This is schematically illustrated by respective detection waveforms in the case of the mounting position of the vibration sensor 6 on the vibration transmission plate 8.
8 (b) and 9 (b).

However, this is the case where the vibration is incident on the vibration transmission plate almost perpendicularly as shown by the arrow in the figure, as shown in FIGS. 8 (c) and 9 (c). In the case where the vibration is incident on the vibration transmission plate while being laid down, the vibration transmission direction component of the vibration transmission plate, that is, the vibration amplitude of the S0 wave increases, and the A0 wave decreases. It becomes a waveform. Therefore, when the mounting position of the vibration sensor 6 on the vibration transmission plate 8 is either the front surface or the side surface of the vibration transmission plate and the detection wave mode is only A0 or S0, the detected waveform amplitude depends on the vibration incident angle. It fluctuates greatly and erroneous detection occurs.

FIG. 10 shows a mounting configuration of the vibration sensor according to the embodiment of the present invention on the vibration transmission plate. Vibration sensor 6a
Is mounted on the surface of the vibration transmission plate 8, and the vibration sensor 6a '
Is attached to the side. The same applies to the vibration sensors 6b to 6d '. With this configuration, it is possible to always obtain any of the detection waves in FIGS. 8 and 9 described above. In the signal waveform detection circuit 9, it is determined whether the detection wave is from the vibration sensor 6a or from the vibration sensor 6a '. It can be determined.

That is, in the signal waveform detection circuit 9, FIGS.
A predetermined threshold value L1 to L4 is provided as shown in FIG. 3 and the detected waveform amplitude is compared with these threshold values to select a vibration mode. The detection signal which has reached a predetermined level by the selection means is used to measure the vibration transmission delay time. Each threshold value is set so that at least one of the detection amplitude levels of the A0 wave detection by the vibration sensor 6a and the S0 wave detection by the vibration sensor 6a 'exceeds the threshold value,
It is also assumed that the attenuation curve due to distance is taken into account.

As described in <Description of the arithmetic control circuit>, the signals detected from the respective vibration sensors 6a to 6d 'are compared with the above-mentioned threshold value in the signal waveform detection circuit 9 and are selected by the selecting means. Any of the two sets of vibration sensors, namely, 6a to 6d or 6a 'to 6d', is selected, and a signal indicating the timing at which the vibration reaches each vibration sensor is generated. For example, when the A0 wave exceeds the predetermined threshold, the vibration sensors 6a to 6d are selected, and when the S0 wave exceeds the predetermined threshold, the vibration sensors 6a 'to 6d' are selected.

Therefore, in a wide range from a vertical angle where the vibration incident angle of the indicator rod is vertical to almost parallel to the vibration transmission plate, either the A0 wave or the S0 wave having a sufficiently large amplitude to prevent erroneous detection can be detected. If the detected vibration sensor is 6a, it is A0, and if it is 6a ', it is S0. Therefore, based on the information, the arithmetic and control circuit 1 determines A0 for each of the vibration sensors 6a to 6d. Of 6a '~
In the case of 6d ', the distance is obtained from the vibration arrival time to each vibration sensor using the velocity constant of S0, and the coordinate position of the pointing rod is calculated.

(Second Embodiment (FIG. 11)) At all incident angles in the present invention, whichever of the A0 wave or the S0 wave, which has the larger vibration amplitude, is detected, and the A0 wave and the S0 wave are discriminated. As another embodiment to be performed, Japanese Patent Laid-Open No. 5-1994
6 and the mounting position configuration on the vibration transmission plate 8 of the vibration sensor 6 disclosed in Japanese Patent Application No. 6-4425 (FIG. 11).
The case where is used will be described.

As shown in the figure, two longitudinal (thickness) direction vibration sensors are provided for the same detection point with the vibration transmission plate interposed therebetween (6a, 6a "). Two vibration sensors 6a, 6a" at the same detection point on the front and back sides are provided. Assuming that the polarity of the electrodes is negative on the vibration transmission plate side and positive on the opposite side, the two vibration sensors 6a and 6a "have the opposite phase with respect to the A0 wave as shown in FIG. (Theoretically doubled if there is no misalignment factor on the front and back), and for the S0 wave, the two vibration sensors 6a and 6a "have the same phase, and thus are strengthened by adding (also the same). Theoretically, if there are no misalignment factors on the front and back, 2
Times). Therefore, in the present embodiment, the difference between the signal outputs of the two vibration sensors 6a and 6a ″ corresponds to the case where the vibration sensor is mounted on the surface of the vibration transmission plate, and the added one is mounted on the side surface. The subsequent processing is the same as that of the first embodiment.Theoretically, as described above, the unnecessary vibration modes should cancel each other and become 0, but in actuality, In many cases, the vibration sensor itself has dimensions that cannot be ignored with respect to the wavelength, and positional deviation between the front and the back is added.

(Third Embodiment) In the above description, the plate wave vibration having different modes of transmitting the vibration transmitting plate is discriminated and selected according to the mounting position of the vibration sensor. And the like, the plate wave vibrations having different modes of transmitting the vibration transmitting plate in the detection signal and the arithmetic processing may be discriminated and selected.

In the present embodiment, means for storing in advance constants such as different transmission speeds corresponding to the plate wave vibrations in the different modes, and a vibration sensor provided on the vibration transmission plate.
A plurality of vibration sensors, two or more sets of vibration sensors from among the three or more vibration sensors, coordinate calculation for each of the sets, and comparing the results with each other. The calculation is performed twice using constants such as the above, and the calculation result of the transmission speed constant that matches the coordinate calculation result obtained by the comparison is used. That is, when the vibration incident angle of the pointing rod is nearly vertical and large, the A0 wave is detected, and the S0 wave is detected as the vibration incident angle falls. In any case, the A0 wave and the S0 wave are detected. Calculate with two speed constants. At this time, similarly to the above-described embodiment, it is desirable to provide a means for canceling another level fluctuation factor such as distance attenuation so that the vibration mode at the time of capturing does not differ for each vibration sensor.

The above calculation method is described in Japanese Patent Application
The determination may be made by the method disclosed in 15989.

[0063]

As described above, according to the present invention, different vibration modes transmitting the vibration transmitting plate are discriminated and selected, and the coordinate calculation is performed based on the vibration transmission of the selected vibration mode. High-precision coordinate input becomes possible regardless of the input attitude of the oscillation source (vibrating pen, pointing stick, etc.) with respect to the vibration transmission plate.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing the overall configuration of a coordinate input device according to the present invention.

FIG. 2 is a configuration diagram illustrating a configuration of a pointing rod.

FIG. 3 is a block diagram illustrating an internal configuration of an arithmetic control circuit in detail.

FIG. 4 is a time chart of signal processing.

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

FIG. 6 is an explanatory diagram for calculating a coordinate position.

FIG. 7 is an explanatory diagram illustrating two types of vibration modes of a plate wave.

FIG. 8 is an explanatory diagram showing a detection waveform when a vibration sensor is attached to a surface of a vibration transmission plate.

FIG. 9 is an explanatory diagram showing a detection waveform when a vibration sensor is attached to a side surface of a vibration transmission plate.

FIG. 10 is an explanatory diagram showing attachment of a vibration sensor according to one embodiment of the present invention.

FIG. 11 is an explanatory view showing attachment of a vibration sensor according to another embodiment of the present invention.

FIG. 12 is an explanatory diagram showing an input angle of a conventional vibration pen.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Arithmetic control circuit 2 Oscillator drive circuit 3 Indicator rod 4 Oscillator 5 Indicating member 6a-6d 'Vibration sensor 7 Anti-vibration material 8 Vibration transmission plate 9 Signal waveform detection circuit

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hajime Sato 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Ryozo Yanagisawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inside the corporation

Claims (6)

[Claims] 1. A coordinate input device for detecting a plate wave vibration from a vibration oscillation source by a plurality of vibration sensors provided on a vibration transmission plate and detecting a position coordinate of the oscillation source based on the vibration transmission time. Means for discriminating between plate wave vibrations having different vibration modes generated and transmitted to the vibration transmission plate, means for selecting a vibration mode from the discriminated plate wave vibrations, and a position of the oscillation source based on the vibration transmission of the selected vibration mode. A coordinate input device comprising: means for calculating coordinates; and 2. The coordinate input device according to claim 1, wherein said means for selecting a vibration mode selects a vibration mode by comparing the vibration amplitude of a detection signal of a vibration sensor. 3. The mode according to claim 1, wherein the different vibration modes are a symmetric wave mode and an asymmetric wave mode.
2. The coordinate input device according to 1. 4. The means for discriminating between plate wave vibrations having different vibration modes is a vibration sensor provided on the surface and side surface of the same detection point of the vibration transmission plate, respectively. The coordinate input device according to claim 3, wherein the vibration is distinguished from a vibration in a symmetric wave mode from a vibration sensor provided on a side surface. 5. The means for discriminating between plate wave vibrations having different vibration modes is a vibration sensor provided on the front surface and the back surface of the same detection point of the vibration transmission plate, and calculates a difference or a sum of signals of the respective vibration sensors. The coordinate input device according to claim 1, wherein the vibration mode is discriminated by this. 6. A coordinate input device for detecting plate wave vibration from a vibration oscillation source by three or more vibration sensors provided on a vibration transmission plate and detecting a position coordinate of the oscillation source based on the vibration transmission time. Means for calculating the position coordinates of the oscillation source from the vibration transmission time detected by a predetermined set of the vibration sensors and the calculation constants corresponding to the first and second vibration modes of the plate wave vibration, respectively; Means for calculating the position coordinates of the oscillation source from the vibration transmission time detected by the other set and the calculation constants corresponding to the first and second vibration modes of the plate wave vibration, respectively, A coordinate input device for comparing a coordinate and detecting a position coordinate from a calculation result of a matching calculation constant.