JPH05189132A - Coordinate input device - Google Patents

Abstract

PURPOSE:To provide the high-accuracy coordinate input device which is easily used and miniaturized. CONSTITUTION:When vibrations are applied to a vibration transmitting board by a vibrating pen, they are transmitted through the vibration transmitting board and detected by vibration sensors. A distance from the positions of the respective sensors to that of the vibrating pen is calculated and from that calculated distance, the coordinate values of the vibrating pen on the vibration transmitting board as a coordinate input plane are calculated independently for X and Y axes. In this case, A vibrator driving circuit to drive the vibrating pen generates signals at frequencies fb and fc through a frequency divider circuit 202 from signals generated at an oscillator 201, and either of those signals is inputted to a shift register 205 by a switching circuit 204. As the switching signal of the switching circuit 204, the signal generated at the oscillator 201 is frequency divided and used. Thus, when the vibrating pen is driven at the two kinds of frequencies and these vibrations are received, phase delay time is measured from the signal at the lower frequency, group delay time is measured from the higher frequency and based on those data, coordinates are calculated.

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.

(1) A method of detecting a coordinate value by a resistance film and a sheet material arranged so as to face each other and detecting a change in resistance value of a pressed point.

(2) A method of detecting the coordinate position of both electromagnetic and electrostatic inductions of conductive sheets and the like arranged opposite to each other.

(3) A method of detecting the coordinate position of the input pen based on 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 above-mentioned resistance film utilizing type (in the case of 1), the uniformity of the low antibody directly influences the accuracy of the figure input, so that the low antibody having excellent uniformity is required,
Therefore, a device that requires particularly high precision is very effective. 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 using electromagnetic induction (case 2), since the electric wires are arranged in a matrix, the coordinate input surface is not transparent, and it is placed on the manuscript or the display. Not suitable for use. Further, the coordinate detection accuracy of the device according to this method directly depends on the positions of the electric wires arranged in a matrix, that is, the processing accuracy, so that a highly accurate input device becomes very expensive.

Compared to these methods, the ultrasonic method 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 for calculating the position coordinates on the tablet. Since no work is done, 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, the ultrasonic method has the following drawbacks. The vibration that is input to the tablet by the input pen propagates in the tablet while being attenuated, eventually reaches the end surface of the tablet, and is reflected. Even if an anti-vibration material is attached to the end face to suppress the vibration, this reflected wave cannot be completely removed. Therefore, the direct wave necessary for measuring the arrival delay time of the wave (the wave propagating in the shortest distance between the input pen and the sensor for detecting the vibration) and the reflected wave are superposed, and from the superposed portion, There is a problem that the detection signal waveform output from the sensor is distorted. This distortion causes an error when measuring the time when the wave propagates, and significantly lowers the coordinate detection accuracy. In order to solve this problem, it is necessary that the reflected wave does not overlap with the delay time detection point in the detection signal waveform formed by the direct wave in any case. For this reason, the sensor is set at a position that is not affected by the reflected wave.

[0011]

However, this solution is to solve this problem by increasing the path difference between the direct wave and the reflected wave in order to save the time for the reflected wave to return. As a result, there is a new defect that the size of the entire device, that is, the size of the coordinate input surface becomes larger than the effective area in which the coordinates can be input.

Further, the higher the sound velocity of the wave propagating on the vibration transmitting plate, the lower the resolution of the coordinate calculation. In other words, if the counters for measuring time have the same resolution, it means that the slower the sound velocity of the wave to be handled, the better the resolution of distance measurement. Therefore, when a distance is calculated from the delay time using a high-speed wave, a counter having a corresponding time resolution (increasing the counter frequency) is used to maintain the resolution of the calculated distance, which results in cost reduction. It had the drawback of being expensive and consuming large amounts of power.

The present invention has been made in view of the above conventional example, and an object thereof is to provide a coordinate input device which is small in size, high in accuracy, low in cost and low in power consumption.

[0014]

[Means for solving the problem] and

To achieve the above object, the coordinate input device of the present invention has the following structure. 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 input surface by the coordinate indicator is measured. A coordinate input device for calculating and outputting the designated point as a coordinate value, the means for measuring a delay time relating to the phase velocity of the vibration from the vibration of the first frequency transmitted through the coordinate input surface; Means for measuring the delay time relating to the group velocity of the vibration from the vibration of the second frequency higher than the first frequency transmitted through the input surface, and the means for measuring the delay time based on the measured group velocity and phase velocity. And means for calculating the coordinate position of the coordinate pointing device.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the embodiments shown in the drawings. [Embodiment 1] FIG. 1 shows the structure of a coordinate input device according to the present embodiment. In the figure, reference numeral 1 is an arithmetic control circuit for controlling the entire apparatus and calculating a 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, the vibration transmitting material 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. Reference numeral 9 is 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).

FIG. 2 shows the vibrating pen 3 in more detail. The vibrator 4 built in the vibrating pen 3 is vibrated by a signal input from the vibrator driving circuit, and the vibration energy is concentrated by the horn 5, so that the vibration transmitting plate 8
Communicate to.

<Description of Transducer Drive Circuit> FIG. 3 is a block diagram showing a specific configuration of the oscillator drive circuit 2 for driving the oscillator 4 of the vibrating pen 3, and FIG. 4 is a timing chart thereof.

In FIG. 3, the clock of the frequency fb (signal 211 of the timing chart of FIG. 4) oscillated by the oscillator (OSC) 201 is divided by the frequency dividing circuit 202 into the frequency of fc (signal 212 of the timing chart). After that, it is input to the switching circuit 204 for switching between fb and fc. Further, the clock fb output from the OSC 201 is supplied to the signal 21 of the timing chart by another frequency dividing circuit 203.
It is divided into clocks indicated by 3. Further, the clock 213 is input to the switching circuit 204, and the switching circuit 204 alternately selects the clock fb and the clock fc according to the clock 213, and inputs them to the shift register 205. This signal is the signal 215 in FIG. 4, and changes from the frequency fb to fc with the clock 213. The shift register 205 is configured to output a pulse train of several cycles (4 cycles in this embodiment) immediately after the clock 213 changes, and the frequency of the pulse train 214 is fb.
And the frequency of fc.

As a result, from the shift register 205,
As shown in the timing chart of FIG.
Immediately after the change of frequency f
The clocks 1 and f2 are output alternately. A drive circuit 206 changes the clock 214 output from the shift register 205 to an electric signal level optimal for driving the vibrator 4. In the case of this embodiment, the oscillator is driven by a pulse train of a rectangular wave, but there is no problem even if the drive waveform is a sine wave or the like.

Here, the vibrator 4 is driven at two different frequencies. By making these two frequencies the resonance frequencies of the vibrating pen 3, the vibration of the desired frequency can be efficiently obtained from the pen tip of the vibrating pen 3. be able to. That is, in the state where the vibrator is incorporated in the vibrating pen 3, it is possible to efficiently obtain the vibration by checking the resonance characteristics of the vibrator and using the fundamental resonance frequency and the secondary resonance frequency as the drive frequencies.

<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).
To start the vibrator drive circuit 2 and output the signal for driving the vibrator 4 in the vibrating pen 3 as described above.
The time measurement by the internal timer (which is composed of a counter) is started. Then, the vibration generated by the vibrating pen 3 propagates on the vibration transmitting plate 8 and arrives after being delayed according to the distance to the vibration sensors 6a to 6d.

The signal waveform detecting circuit 9 includes the vibration sensors 6a to 6a.
The signal from 6d is detected and a signal indicating 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, and each vibration sensor The vibration arrival times of 6a to 6d are detected, and the coordinate position of the vibrating pen is calculated. Further, the arithmetic control circuit 1 drives the display drive circuit 10 based on the calculated position information of the vibrating pen 3 to control the display by the display 11, or the serial,
Coordinates are output to an external device by parallel communication (not shown).

FIG. 5 is a block diagram showing a schematic structure of the arithmetic and control circuit 1 of the embodiment. The respective constituent elements and the operation outline thereof 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 sensor (6a
It is possible to measure the delay time until the vibration is detected by (6d).

The circuits that are the other constituent elements will be described in order.

The vibration arrival timing signals from the vibration sensors 6a to 6d output from the signal waveform detection circuit 9 are latched via the detection signal input port 35 to the latch circuits 34a to 34a.
It is input to d. 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 the detection signals have been received,
A signal to that effect is output 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. Then, by outputting the calculated coordinate position information to the display drive circuit 10 via the I / O port 37, it is possible to display a dot or the like at a corresponding position on the display 11, for example. 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.

<Characteristics of Plate Wave (FIGS. 6 and 7)> FIG. 6 shows general properties of velocity of elastic wave (plate wave) propagating on the plate. It is well known that the phase velocity Vp and the group velocity Vg of the plate wave depend on the product of the plate thickness d and the frequency f of the wave (hereinafter referred to as the fd value). It can be seen that in the frequency band in which the fd value is relatively low, the group velocity Vg and the phase velocity Vp both increase as the fd value increases. In this embodiment, the frequency of the plate wave propagating on the vibration transmitting plate 8 is several hundred KHz, and the plate thickness is about 1.6 mm, which is a region where the above-mentioned fd value is relatively low. Therefore, it can be seen that the plate wave generated at the high frequency has a higher group velocity and phase velocity than the plate wave generated at the low frequency.

FIG. 7 is a detailed view of a region (fd = 0.3 to 1.0 MHz * mm) having a relatively small fd value in FIG.
Now, let us consider calculating the distance from the arrival delay time using this plate wave. Since the plate wave obviously has a different group velocity and phase velocity, the phase information differs with respect to the entire waveform (envelope) depending on the propagation distance of the wave. FIG. 8 shows such a situation. The peak of the envelope and the peak of the phase of the detection signal waveform at a certain point and the detection signal waveform at a certain distance L from the point coincide with each other (FIG. 8).
In contrast to (A)), when the distance changes by ΔL, the peak of the envelope and the peak of the phase do not match (FIG. 8 (B)). That is, as the propagation distance increases, the phase in the detection signal waveform always starts in the positive direction (FIG. 8 (A)).
Instead, the phase gradually shifts and it starts from the negative direction (FIG. 8 (B)), and when the distance further shifts, it returns to the original state, and the periodic phenomenon is repeated. At this time, if the phase delay time Tp related to the phase velocity is to be measured, for example, when the phase level becomes a certain level or more for a first time as a detection point, the relationship between the distance and the phase delay time is staircase. Become a state.

On the other hand, the group delay time Tg related to the group velocity is
Since the relationship between the envelope and the phase changes depending on the distance, it cannot be detected from the phase information. Therefore, it is necessary to take out the envelope of the waveform formed by the phase information and measure the group delay time Tg with a singular point such as a peak of the waveform as a detection point. At this time, the problem here is that the detection point of the group delay time Tg is located at a later point on the time axis than the detection point of the phase delay time Tp. That is, the group delay time Tg
That is, the detection point is not in the head portion of the detection signal waveform but in the vicinity of the peak of the waveform which is later in time than the head portion. If the vibration sensor 6 exists near the end surface of the vibration transmission plate 8, the leading portion of the detection signal waveform is reflected by the end surface, and the reflected wave is superimposed on the direct wave (the detection signal waveform is distorted). There arises a problem that the peak value formed by the direct wave cannot be detected correctly.

Now, it is assumed that the peak value of the detection signal waveform by the direct wave is formed at the K wavelength from the head portion of the direct wave. If the group velocity of this wave is Vg1 and the frequency is f1, the time from the beginning to the peak value (detection point) is t _point = K · 1 / f1 = K / f1 (1) The distance L _d that the group travels is L _d = t _point · Vg1 = (K · Vg1) / f1 (2) Therefore, in order to prevent the reflected wave from being superimposed on the peak of the direct wave, the vibration sensor 6 and the vibration transmission plate 8
The distance from the end face of the must be L _d / 2 or more.
As a result, there is a problem that the size of the vibration transmission plate 8 becomes larger than that of the effective area in which the coordinates can be input, and thus the size of the entire device becomes large.

This problem can be applied to the detection point of the phase delay time, but the detection point can be set near the beginning of the detection signal waveform (indicating that the value of K in the equation (1) is smaller). It can be said that it is the position of the group delay time detection point that determines the size of the vibration transmission plate 8.

Returning to FIG. 7 again, the relationship between frequency and group velocity will be considered. From this relationship, it is assumed that when the plate thickness is constant, the equation (3) approximately holds in a certain minute range.

Vg1 = αf1 + β; (α and β are positive constants) (3) When the formula (3) is substituted into the formula (2), L _d = K · (α + β / f1) (4) Therefore, the plate When a wave is used, the value of L _d can be reduced by increasing the frequency. Although the equation (3) is considered in a certain minute range, the relationship between the fd value and the group velocity Vg / phase velocity Vp increases uniformly and monotonically in the above-mentioned region where the fd value is relatively small, and is convex upward ( The slope is monotonically decreasing), and the value of L _d can be reduced as the frequency is increased within the range of the fd value.

At this time, an adverse effect caused by increasing the frequency will be considered. The coordinate input device using ultrasonic waves calculates the distances from the vibrating pen 3 to the sensors 6a to 6d, that is, measures the propagation time of the wave and calculates the product with the velocity of the wave to calculate the coordinates. It is basically done.
Therefore, the coordinate detection resolution is closely related to the distance calculation resolution. The distance calculation resolution depends on the time resolution of the counter that measures the delay time and the velocity of the wave. That is,
If the time resolution of the counter is the same, the distance calculation resolution is improved by using a slower wave.

As described above, when a high frequency wave is used to reduce the unnecessary portion of the vibration transmission plate 8, the speed increases with it, so that the counter having a higher time resolution is required to maintain the distance calculation resolution. However, there are drawbacks such as high cost and large power consumption. Therefore, a plate wave having a high frequency is used for measuring the group delay time, and a plate wave having a low frequency and a slow speed is used for measuring the phase delay time. A method for calculating coordinates from the group delay time Tg and the phase delay time Tp will be described below. However, since the group delay time is not used for direct distance calculation as described later, the time resolution of the counter is the group delay time detection value. The coordinate calculation algorithm has a feature that is not required by the coordinate calculation algorithm.

<Description of Vibration Propagation Time Detection (FIGS. 9 and 1)
0)> Hereinafter, the principle of measuring the vibration arrival time to the vibration sensor 3 will be described.

FIG. 9 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. 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 circuit 2. At this time, the drive signal 41 is applied from the oscillator circuit 2 to the oscillator 4. This signal 41 causes the vibration pen 3 to move to the vibration transmission plate 8.
The ultrasonic vibration transmitted to the vibration sensor 6a is detected by the vibration sensor 6a after being signaled for a time corresponding to the distance to the vibration sensor 6a.

The signal indicated by 42 in the figure is the vibration sensor 6a which is a wave generated when the frequency of the signal for driving the vibration pen is high.
2 shows a detection signal waveform detected by the above-mentioned method and a detection signal waveform obtained by a low-frequency drive signal driven after a fixed time (tc in the figure). As described above, since the vibration used in this embodiment is a plate wave, the envelope 42 of the detected waveform with respect to the propagation distance in the vibration transmission plate 8 is used.
1 and phase 422, and envelope 425 and phase 426
During vibration transmission, the relationship of changes according to the transmission distance. Here, the traveling speed of the envelope 421 obtained by driving with a high frequency, that is, the group speed is Vg. In addition, the traveling speed of the phase (426 in the figure) obtained by driving with a low frequency is defined as 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 speed is Vg, and when a point on a certain specific waveform, for example, a peak is detected, the envelope 43 is differentiated (signal 44) and its zero-cross point is set to the group delay time. Use as the detection point. The distance between the vibration pen 3 and the vibration sensor 6a is given by d = Vg · tg (5), where the vibration transmission time is tg. 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. The time from the specific detection point of the phase waveform signal 426, for example, the vibration application to the zero crossing point at which the phase is changed from the negative to the positive after the predetermined signal level 45 is tp'48 (signal 46).
On the other hand, when the window signal 47 having a predetermined width is generated and is compared with the phase signal 426), the time tp at which the wave actually propagates is tp = tp'-tc (6). Therefore, the distance between the vibration sensor and the vibration pen is d = n · λp + Vp · tp (7) Here, λp is the wavelength of the elastic wave (wavelength of the wave obtained at a low driving frequency), and n is an integer.

From the equations (5) and (7), the above integer n
Is expressed as n = int [(Vg · tg−Vp · tp) / λp + 1 / N] (8).

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. In other words, there is a margin in the detection of Tg, and the error is absorbed by the equation (8), so a high-resolution counter is not necessary for the group delay time detection. By substituting n obtained in this way into the equation (7), the distance between the vibration pen 3 and the vibration sensor 6a can be accurately measured. As is clear from the equation (7), since the phase delay time Tp to be measured is measured using a wave having a low frequency and a low speed, the distance can be calculated with high resolution.
The signals 43 and 48 for measuring the two vibration transmission times tg and tp 'described above are generated by the signal waveform detection circuit 9. The signal waveform detection circuit 9 is configured as shown in FIG. To be done.

FIG. 10 is a block diagram showing the configuration of the signal waveform detection circuit 9 of the embodiment. In FIG. 10, the output signal of the vibration sensor 6a is amplified to a predetermined level by the preamplifier circuit 51, and then input to the envelope detection circuit 52 including an absolute value circuit and a low pass filter.

The peak point of the signal extracted by the envelope detection circuit 52 is detected by the envelope peak detection circuit 53. Thereafter, a signal t which is an envelope delay time detection signal of a predetermined waveform is detected by a tg signal detection circuit 54 composed of a mono multivibrator or the like.
g (signal 43 in FIG. 9) is formed and input to the arithmetic control circuit 1.

After the group delay time tg is detected (the interval between the first drive frequency and the second drive frequency is tc),
The vibrating pen 3 is driven at a lower frequency, and the detection signal waveform that is also output by the vibrating pen 3 is output.

In this embodiment, in order to detect signal arrival,
Again, the envelope 425 of the detection signal waveform is taken out. A signal detection circuit 55 forms a pulse signal 46 of a portion of the envelope signal 425 detected by the envelope detection circuit 52 that exceeds the threshold signal 45 of a predetermined level. Reference numeral 56 is a monostable multivibrator, which opens the gate signal 47 of a predetermined time width triggered by the first rising edge of the pulse signal 46. 57 is a tp 'comparator, which is a phase signal 42 while the gate signal 47 is open.
The first rising zero cross point of 6 is detected, and the phase delay time signal tp'48 is supplied to the arithmetic control circuit 1. Note that in the block diagram of FIG. 10, the output of the phase delay time related to the phase information 422 is the detection signal waveform obtained when the driving frequency is high, and the detection signal waveform obtained when the driving frequency is low is related to the envelope 425. Although the output of the group delay time is obtained, the originally required group delay time tg related to the envelope 421 and the phase delay time tp ′ related to the phase information 422 may be selected by the arithmetic control circuit. Needless to say, after the tg detection is performed, the circuit may be switched using a switch before and after the envelope detection circuit 52, for example. The circuit described above is for the vibration sensor 6a,
The same circuit is provided for the other vibration sensors in this embodiment.

<Description of Calculation of Coordinate Position (FIG. 11)> Next, the principle of actually detecting the coordinate position on the vibration transmission plate 8 by the vibration pen 3 will be described.

Now, in the vicinity of the midpoint of four sides on the vibration transmission plate 8,
When the two vibration sensors 6a to 6d are provided at the positions S1 to S4, the linear distances da to dd from the position P of the vibration pen 3 to the positions of the respective vibration sensors 6a to 6d are calculated based on the principle described above. You can ask. Further, the arithmetic control circuit 1 can obtain it based on the linear distances da to dd from the theorem of 3 squares of the coordinates (x, y) of the position P of the vibrating pen 3 as follows.

X = (da + db) · (da−db) / 2X (9) y = (dc + dd) · (dc−dd) / 2Y (10) 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. In this way, by measuring the group delay time using the vibration of a frequency higher than the vibration used for measuring the phase delay time, the path of the reflected wave directly to the effective area where the coordinates can be input. It has become possible to reduce the extra area for making a difference. Moreover, with such a configuration, the phase delay time directly required for calculating the coordinates can be obtained by using a wave with a slow phase velocity (low frequency), so a high-frequency clock is used to increase the resolution. It is possible to realize the downsizing of the device without lowering the resolution of the distance calculation without using a correspondingly expensive and power-consuming device.

[0052]

[Other Examples]

[Second Embodiment] As a second embodiment, a coordinate input device having substantially the same configuration as that of the first embodiment as shown in FIGS. 1 and 2 will be described. However, the configuration of the signal waveform detection circuit 5 is different as shown in FIG. 13, and the oscillator drive circuit 2 does not generate two frequencies as shown in the timing chart of FIG. A pulse of one frequency is applied to the vibrating pen to drive the vibrator 4. Here, the oscillator 4 is driven by a pulse-like signal having a high frequency. The basic resonance frequency of the vibrator 4 is, for example, 400 KHz, and when the vibrator 4 is incorporated into the vibrating pen 3, the vibration characteristics of the entire frequency band are wide. By driving the vibrator in impulse, vibrations including various frequency components are incident on the vibration transmission plate from the pen tip of the vibration pen 3.

<Characteristics of Plate Wave> As described above, FIG.
Shows the general property of the velocity of elastic waves (plate waves) propagating on the plate. Phase velocity Vp and group velocity Vg of plate wave
Is well known to depend on the product of the plate thickness d and the wave frequency f (hereinafter referred to as the fd value). In the frequency band where the fd value is relatively low, the group velocity Vg and the phase velocity Vp
Both and are faster as the fd value is larger. In the present embodiment, the frequency band of the plate wave propagating on the vibration transmission plate 8 is several tens KHz to several hundreds Hz and the plate thickness is about 1.6 mm, which is a region where the above-mentioned fd value is relatively low. There is.
Therefore, when the vibration waveform detected by the sensor 6 is compared on the time axis, the leading portion of the signal waveform is composed of a wave having a high propagation speed and a high frequency, and a plate having a frequency that gradually decreases with time. The wave reaches the sensor 6, is electrically converted by the sensor, and is output by being listed with the wave having a higher frequency that has reached earlier. Waves with different velocities can be detected by processing the signals output from the sensor through bandpass filters with different center frequencies. That is, if the center frequency of the band addition filter is made high, a wave having a high speed can be detected, and as the center frequency of the band pass filter becomes lower, the speed becomes slower accordingly.

[0054] Also, as described in the first embodiment, upon detection of the K wavelength from the head of the direct wave of the frequency f1, the distance L _d of vibration from the beginning to the detection point is transmitted, L _d = K・ (Α + β / f1) ... (4)

Therefore, when a plate wave is used, the value of L _d can be reduced by increasing the frequency. Now, the formula (3) is considered in a certain minute range, but the above-mentioned relatively fd
In the region where the value is small, fd value and group velocity Vg / phase velocity V
The relationship with p is a uniform monotonic increase and a convex relationship (the slope is monotonically decreasing), and the value of L _d can be reduced as the frequency is increased within the range of the fd value. .. However, if high-frequency vibration is used, a high-resolution counter must be used.Therefore, a plate wave with a high frequency is used to measure the group delay time, and a plate wave with a low frequency and a slow speed is used to measure the phase delay time. To use. A method for calculating coordinates from the group delay time Tg and the phase delay time Tp will be described below. However, since the group delay time is not used for direct distance calculation as described later, the time resolution of the counter is the group delay time detection value. The coordinate calculation algorithm has a feature that is not required by the coordinate calculation algorithm.

<Explanation of vibration propagation time (FIGS. 12 and 13)
> Hereinafter, the principle of measuring the vibration arrival time to the vibration sensor 3 will be described.

FIG. 12 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. Note that the vibration sensor 6a will be described below, but the other vibration sensors 6b, 6 will be described.
The same applies to c and 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 circuit 2. At this time,
A drive signal 41 is applied from the oscillator 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 signaled for a time corresponding to the distance to the vibration sensor 6a, and then the vibration sensor 6a.
Detected in.

A signal indicated by 42 in the figure shows a detection signal waveform obtained when the signal detected by the vibration sensor 6a is processed by the first bandpass filter having a high center frequency. As described above, since the vibration used in this embodiment is a plate wave, the relationship between the envelope 421 of the detection waveform and the phase 422 with respect to the propagation distance in the vibration transmission plate 8 is that during the vibration transmission. It changes according to the transmission distance. Here, the advancing speed of the envelope 421, that is, the group speed is Vg.
And The signal indicated by 44 indicates a detection signal waveform obtained when the signal detected by the vibration sensor 6a is processed by the second bandpass filter whose center frequency is lower than that of the first bandpass filter. At this time, the advancing speed of the phase 442, that is, the phase speed is set to Vp. These group velocities V
The distance between the vibration pen 3 and the vibration sensor 6a can be detected from g and the phase velocity Vp. First, envelope 4
Focusing only on 21, the speed 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 distance between the vibration pen 3 and the vibration sensor 6a is detected. Is given by d = Vg · tg (5) with its vibration transmission time being tg. 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 is performed based on the detection of the phase signal. The time from a specific detection point of the phase waveform signal 422, for example, vibration application, to a zero-cross point at which the phase first changes from negative to positive after a certain predetermined signal level 46 is tp49 (a window signal having a predetermined width with respect to the signal 47). 48 is obtained and obtained by comparing with the phase signal 442), the distance between the vibration sensor and the vibration pen is d = n · λp + Vp · tp (6). Here, λp is the wavelength of the elastic wave (wavelength of the wave detected by the second bandpass filter), and n is an integer.

From the above equations (5) and (6), the above integer n
Is expressed as n = int [(Vg · tg−Vp · tp) / λp + 1 / N] (7).

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. That is, there is a margin in the detection of Tg, and the error is absorbed by the equation (7), and therefore a high-resolution counter is not necessary for detecting the group delay time. By substituting n obtained in this way into the equation (6), the distance between the vibration pen 3 and the vibration sensor 6a can be accurately measured. As is clear from the equation (6), since the measured phase delay time Tp is measured using a wave having a low frequency and a low speed, the distance can be calculated with high resolution.
Further, the signals 43 and 49 for measuring the two vibration transmission times tg and tp described above are generated by the signal waveform detection circuit 9. The signal waveform detection circuit 9 is configured as shown in FIG. ..

FIG. 13 is a block diagram showing the configuration of the signal waveform detection circuit 9 of the embodiment. In FIG. 13, the output signal of the vibration sensor 6a is amplified to a predetermined level by the amplifier circuit 51. In the present embodiment, a bandpass filter is used as the bandpass filter, and the above-mentioned amplified signal is subjected to bandpass filter 511 and bandpass filter 512 to remove the extra frequency component of the detection signal. Then, for example, the signals are respectively input to the envelope detection circuit 521 and the envelope detection circuit 522 which are configured by an absolute value circuit, a low pass filter, and the like. Here, the pass center frequency of the band pass filter 511 is set higher than that of the band pass filter 512.

The peak point of the signal extracted by the envelope detection circuit 521 is detected by the envelope peak detection circuit 53. After that, a signal tg (signal 43 in FIG. 7), 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 is input to the arithmetic control circuit 1.

On the other hand, 55 is a signal detection circuit, which detects the envelope signal 4 detected by the envelope detection circuit 522.
A pulse signal 47 of a portion of 41 which exceeds a threshold signal 46 of a predetermined level is formed. 56 is a monostable multivibrator, which opens the gate signal 48 of a predetermined time width triggered by the first rising edge of the pulse signal 47. 57 is tp
This is a comparator, which detects the first rising zero-cross point of the phase signal 442 while the gate signal 48 is open, and supplies the phase delay time signal tp49 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.

The distance between the vibration sensor 6 and the position where the vibration pen 3 enters the wave can be obtained based on the above principle, and the coordinates are calculated from the distance as described in <Description of coordinate position calculation> in the first embodiment. Can be calculated and output.

As described above, the group delay time is measured by using the vibration having a higher frequency than the vibration used for the measurement of the phase delay time, so that the direct wave and the reflection are reflected to the effective area where the coordinates can be input. It has become possible to reduce the extra area for gaining the path difference from the waves. Moreover, with such a configuration, the phase delay time directly required for calculating the coordinates can be obtained by using a wave with a slow phase velocity (low frequency), so a high-frequency clock is used to increase the resolution. It is possible to realize the miniaturization of the device without lowering the resolution of the distance calculation without using a correspondingly expensive and power-consuming 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.

[0068]

As described above, the coordinate input device according to the present invention can realize a highly accurate coordinate input which is small in size, low in cost and low in power consumption.

[Brief description of drawings]

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

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

FIG. 3 is a block diagram of a vibrator drive circuit.

FIG. 4 is a timing chart of a vibrator drive circuit.

FIG. 5 is a block diagram showing a configuration of an arithmetic control circuit.

FIG. 6 is a diagram illustrating plate wave velocity.

FIG. 7 is a diagram illustrating plate wave velocity.

FIG. 8 is a schematic diagram of a detection signal waveform.

FIG. 9 is a timing chart of signal processing.

FIG. 10 is a block diagram showing a configuration of a signal waveform detection circuit.

FIG. 11 is an explanatory diagram for calculating coordinate positions.

FIG. 12 is a timing chart of signal processing according to the second embodiment.

FIG. 13 is a block diagram illustrating a configuration of a signal waveform detection circuit according to a second exemplary embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 arithmetic control circuit, 2 oscillator drive circuit, 3 vibrating pen, 6 sensor, 7 anti-vibration material, 8 vibration transmission plate, 9 signal waveform detection circuit, 201 oscillator, 202/203 collection circuit, 204 switching circuit, 205 shift The register 206 is a drive circuit.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Jun Tanaka, 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Yuichiro Yoshimura, 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Within the corporation

Claims (3)

[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. A coordinate input device for calculating and outputting a designated point on the coordinate input surface as a coordinate value by measuring the delay time related to the phase velocity of the vibration from the vibration of the first frequency transmitted through the coordinate input surface. Means, means for measuring a delay time relating to a group velocity of the vibration from a vibration having a second frequency higher than the first frequency transmitted through the coordinate input surface, the measured group velocity and phase velocity And a means for calculating the coordinate position of the coordinate indicator based on the coordinate input device. 2. The coordinate input device according to claim 1, wherein the coordinate pointing device is alternately driven at the first frequency and the second frequency in a predetermined cycle. 3. A first bandpass filter having the first frequency as a center frequency, and a second bandpass filter having the second frequency as a center frequency, wherein the coordinate designating means includes the first bandpass filter. Of the first frequency band and the second frequency band of the second frequency band are generated by the first band-pass filter and the second band-pass filter from the output signal of the sensor. The coordinate input device according to claim 1, wherein the vibration of the frequency is extracted.