JPH05233134A - Coordinate input device - Google Patents

Abstract

PURPOSE:To provide a coordinate input device having a wireless vibration pen. CONSTITUTION:The input pen 1 for inputting ultrasonic vibration is set to be wireless, and the ultrasonic signal of a prescribed frequency is outputted at a prescribed period in asynchronizing with the control part of a main body. On the other hand, plural vibration sensors 2 provided in the prescribed positions of a vibration transmission board 3 detect the vibration. The control part measures transmission time till signals arrive at the respective sensors 2 from reference time which is appropriately decided, calculates (X, Y)-coordinates by the plural combinations of the sensors based on the transmission time, calculates backward the timing difference between reference time and the timing difference of ultrasonic signal output in the actual pen 1 and calculates the accurate coordinate value obtained by correcting the difference. Thus, the coordinate can be calculated without deteriorating precision with respect to the ultrasonic signal which is asynchronously inputted from the input pen 1, and the cordless type ultrasonic coordinate input device can be realized.

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 vibration transmission time to an input pen by detecting a vibration input from an input pen to a vibration transmission plate by a plurality of vibration sensors provided on the vibration transmission plate. And a coordinate input device for detecting the input coordinates of the input pen on the vibration transmission plate based on the measurement result.

[0002]

2. Description of the Related Art An ultrasonic coordinate input device has been conventionally known as an application device of ultrasonic distance measurement.

FIG. 14 is a schematic view of a conventional ultrasonic type coordinate input device. In the figure, reference numeral 1 is an input pen as a coordinate pointing tool, which has a piezoelectric element incorporated therein and outputs a predetermined ultrasonic vibration from its tip.

The vibration transmitting plate 3 constitutes an input section,
It is made of aluminum or glass that transmits ultrasonic vibrations. A vibration isolator 4 is provided around the vibration transmission plate 3 for the purpose of preventing the reflected waves other than the direct waves from the input pen 1 from entering the sensor 2. It should be noted that reference numeral 1a indicates a vibration transmission plate 3
Shows the effective input area divided by printing.

In the ultrasonic coordinate input device having the above structure, as shown in the figure, at least two or more vibration sensors 2, 2, ... The coordinate value of the designated point can be calculated from the distance between the points.

Various methods of calculating the distance r between the sensor and the pointing point are known, but basically, the calculation is performed from the arrival time of the ultrasonic vibration emitted from the input pen 1 to the vibration sensor 2.

When the piezoelectric element of the input pen 1 is driven by several pulses, the vibration detected by the vibration sensor 2 is as shown in FIG.
It becomes something like 5.

A circuit as shown in FIG. 16, for example, is used for vibration detection. The received waveform amplified by the amplifier 5 is rectified by the full-wave rectifier 6, the envelope is extracted by the low-pass filter 7, and its peak position or inflection point is detected by the differentiating circuit 8 and the comparator 9,
This timing is defined as the signal group arrival time tg. Then, the vibration transmission distance r can be calculated by r = vg * tg + (offset value), but if time detection is performed based on the envelope, some fluctuation will inevitably occur due to the influence of the signal output size and the filter characteristics. In order to obtain further accuracy, the phase at an appropriate position is detected, the phase arrival time tp is obtained, and finer accuracy is obtained.

More detailed ultrasonic signal arrival time (tg, t
FIG. 17 shows the configuration of the actual measurement system of p), and FIG. 18 shows the signal waveforms of the circuit parts a to i in FIG.

In FIG. 17, reference numeral 2 is a vibration sensor,
A preamplifier 5 is installed in the immediate vicinity thereof to prevent noise from entering. The received signal amplified by the amplifier 5 is converted into a one-sided envelope waveform (FIG. 18c) by the full-wave rectification (absolute value) circuit 6 and the low-pass filter 7, and the envelope waveform is converted twice by the differentiating circuits 8 and 8 ′. Is performed, and the zero cross point (envelope waveform inflection point) is extracted by the comparator 9 to be the group arrival time tg.

However, in order to extract only the zero crossing point which is the inflection point of the envelope waveform, the reference level comparator 11a which outputs the "H" level when the first differential waveform by the differentiating circuit 8 is above a certain reference level. The window signal for tg detection is set by, and the AND gate 12 takes the logical product with the output of the comparator 9 to set the first rising edge to tg.

Similarly, the tp signal is obtained by passing the envelope output through the reference level comparator 11b, sets a window signal for tp detection, and AND gates 13 the logical product of the sensor output signal and the output of the zero-cross comparator 10. The first fall is tp.

The above times tg and tp correspond to the transmission time of the group and the phase of the ultrasonic vibration, respectively.

A method of calculating the inter-pen-sensor distance r using the above-described detection method will be described below.

When the group velocity vg and the phase velocity vp are equal, it can be obtained by r = vp * tp + (offset value), but when vg ≠ vp, the phase in the group shifts with the distance r. As tp, a stepped one as shown in FIG. 19 is observed, and conversion work is required. This stage shows the movement of the phase detection point, and the connection between the stages is the parallel movement of the period T of the signal. When vg and vp are equal and a constant phase detection point can be observed at all times, such stairs cannot be obtained and tp such as the straight line a is obtained. Therefore, it is only necessary to convert tp obtained in a stepwise manner into the original straight line.

That is, tpa≈ (vg / vp) tg-tof (tof: offset value), but since tg has a large fluctuation, tpi≈nT≈ (vg / vp) tg-tof-tp
Using the property of (n: integer value), tpa is calculated as tpa = tp + T * Int [{(vg / vp) tg-tof-tp} /T+0.5], and r is calculated from the following equation (In
t () represents an integer operation).

R = vp * tp-rof (rof: offset value) An actual operation example until an ultrasonic signal is transmitted from a pen and each sensor of a propagating body receives the ultrasonic signal and calculates a coordinate value of a designated point. Will be explained.

In principle, in the ultrasonic coordinate input device,
The propagation time from when the ultrasonic wave is emitted from the pen until it is received by the sensor is measured, and the distance between the pen sensors is calculated based on this. Therefore, the control unit needs to recognize the time when the ultrasonic signal is transmitted from the pen, and therefore the control unit sends the pen drive signal itself or the pen drive trigger signal to the pen and the controller unit. It is usually supplied to the pen through the connecting signal line.

FIG. 7 shows the structure of the vibration propagation time measuring portion of the conventional control unit.

In the figure, reference numeral 106 is an oscillator which serves as a current clock for measuring the propagation time and which is used for pen drive signal generation after a predetermined frequency division. 107 is a counter circuit for measuring the propagation time.

Here, there are four sensors on the vibration transmission plate, and from each of them, the circuits tg1 to tg from the circuit of FIG.
4, it is assumed that timing pulses of tp1 to tp4 are generated.

Reference numerals 108-1 to 108-8 are eight latch circuits for temporarily saving the propagation time by using the timing pulse as a trigger, and the pulse outputs (tg1 to tg4) from the signal processing system indicating the signal arrival. , Tp1 to tp
The counter value at that time is held by 4).

Reference numeral 109 is a select circuit for selecting each latch circuit when fetching the latched signal arrival times tg1 to tg4 and tp1 to tp4 into the CPU 112, and based on the decoding result of the control code from the CPU 112, One of the latch circuits 108-1 to 108-8 is selected.

Reference numeral 110 is a bus for transmitting the counter value of the counter circuit 107 to each of the latch circuits 108-1 to 108-8, and 111 is a data bus for transmitting the latched propagation time to the CPU 112. Reference numeral 112a is a start signal for resetting and starting the counter and for driving the pen drive circuit 113.

Reference numeral 113 is a pen drive generation circuit for generating a drive signal to the piezoelectric element in the input pen 1 in synchronization with the start signal 112a.

The operation of the circuit of FIG. 7 is as follows. The CPU 112 uses the start signal 112a as shown in FIG.
Is output periodically. As a result, the counter circuit 107
Are reset, and a pen drive signal is output from the pen drive circuit 113.

After that, the CPU monitors signal arrival at each sensor. Then, when it is confirmed that the signals have arrived at all the sensors (after taking in tg3 in FIG. 9), C
The PU sequentially outputs the latch select code to the select circuit 10
It outputs to 9 and takes in the data of each latch circuit 108-1 to 108-8.

When all the data have been taken in, the coordinate values are calculated. Note that if the arrival of signals is not confirmed by all the sensors within the specified time, the counter is restarted and restarted.

The conventional control as described above is shown as a flow chart in FIG. In step S21 of FIG. 3, the counter for measuring the signal transmission time is reset, and step S2
In 2, the input pen is driven. Steps S23 and S2
In step 4, the arrival of vibration to all the sensors is waited for a predetermined time, the vibration transmission times tg and tp to all the sensors are fetched in step S25, and coordinate calculation is performed in step S26.

[0030]

However, in the above-mentioned conventional example, it is necessary to accurately measure the time from the time when the ultrasonic signal is transmitted from the pen to the time when the sensor reaches the sensor. Therefore, the time is managed in the control unit. , A synchronized piezoelectric element drive signal must be provided to the input pen. Therefore, a cable as a signal supply line is indispensable between the control section and the input pen.

In general, from the viewpoint of improving operability, it is widely demanded that the pen of the coordinate input device is cordless.
It goes without saying that the ultrasonic coordinate input device has similar requirements.

An object of the present invention is to solve the above problems and provide a highly accurate coordinate input device having a wireless input pen.

[0033]

In order to solve the above problems, in the present invention, the vibration input from the input pen to the vibration transmission plate is detected by a plurality of vibration sensors provided on the vibration transmission plate. In the coordinate input device that measures the vibration transmission time to the input pen and detects the input coordinates on the vibration transmission plate of the input pen based on the result, the vibration input is intermittently applied to the vibration transmission plate at a predetermined cycle. On a predetermined coordinate system, a wireless configuration input pen including all the mechanisms for performing the operation and a predetermined plurality of combinations of the vibration sensors are used, and vibration transmission time to the vibration sensor from an appropriately determined reference time is used. Input coordinate values are calculated, and the time difference between the reference time and the actual vibration input time from the input pen is corrected based on the difference between the obtained coordinate values, and based on the obtained vibration transmission time. Adopting a configuration in which a control means for calculating a can input coordinates.

[0034]

With the above arrangement, coordinate calculation can be performed without the need for synchronizing control of the input pen and coordinate calculation.

[0035]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the embodiments shown in the drawings. In the following example, the input pen has a completely wireless configuration.

<First Embodiment> FIG. 1 shows the internal circuit of an input pen according to the present invention. In the figure, reference numeral 101 is an oscillator, which generates a reference clock for the counter circuit 102 and the drive signal generator 103.

The counter circuit 102 counts the pulses from the oscillator 101, and outputs a trigger signal for prompting the drive signal output to the drive signal generator 103 at regular intervals.

The drive signal generator 103 outputs a drive signal to the piezoelectric element 104 according to the trigger signal from the counter circuit 102.

By applying a predetermined voltage to the piezoelectric element 104,
Ultrasonic vibrations are generated, and the ultrasonic vibrations are input to the vibration transmission plate via the pen tip of the input pen.

Reference numeral 105 'is a power source composed of a battery such as a lithium battery and serves as a power source of an electric circuit in the pen. Reference numeral 105 is a pen switch for extending the life of the battery, which turns on / off the power supply 105 '. The pen switch 105 is composed of a micro switch or the like attached to the pen tip so that the power is turned on only when the coordinate input operation is performed.

With the above-described wireless structure, when coordinates are input, ultrasonic vibration is output from the input pen independently of the main body control unit, and if the input pen is in contact with the vibration transmission plate, this ultrasonic vibration will occur. Input to the vibration transmission plate. The parts operated by the user (input pen, vibration transmission plate, etc.)
The configuration of is similar to that shown in FIG.

On the other hand, FIG. 2 is a block diagram of a control unit installed in the apparatus main body. Compared to the conventional example, the characteristic part of the figure is that the pen drive circuit is eliminated, but the other parts are the same as the conventional example.

Next, the operation of the above configuration will be described with reference to FIG.
This will be described with reference to the flowchart of FIG.

In the input pen, as shown on the left side of FIG. 8, ultrasonic vibration is output every time a carry is generated by the counter 102 (step S6), that is, at regular time intervals (step S7).

On the other hand, in the control section of FIG. 2, the counter reset is first performed basically asynchronously with the signal transmission of the pen (step S1). Then, after that, the arrival of signals from each sensor is monitored for a certain time (steps S2 and S3), and when the signals arrive at all the sensors in Tr1, each propagation time is fetched into the CPU in the same manner as the conventional method (step S4). ),
Coordinates are calculated according to an algorithm described later (step S5).

When the signals do not arrive at all the sensors within the fixed time Tw, the operation of resetting the counter and monitoring the signal arrival at each sensor again is repeated.

Here, a branch is performed in which the counter is reset and the signal arrival is monitored again (step S3).
The maximum waiting time T of the signal as a threshold of the condition for
How to determine w will be described with reference to FIGS.

First, FIG. 4 shows the same ultrasonic signal (114
The case where the group arrival time for a) is obtained is shown.
Here, t114 is the time when the ultrasonic signal is transmitted from the pen. Further, t115b is the time when the counter is reset in the control unit.

The four signals shown in the figure are pulse signals indicating the group arrival time at the four vibration sensors (generated by the circuit of FIG. 17), and the counter value of the counter 107 is based on them. Latched, Tg1
It is taken into the CPU 112 as Tg4.

In this case, a relationship such as t114 <t115 <(Tg1 to Tg4) min (= tg1) is established (hereinafter, T represents time and t represents time, and (Tg1 to Tg4 ) Min is T
(representing the minimum value of g1 to Tg4), Tg is measured on the basis of t115 in all the sensors.

On the other hand, as shown in FIG. 5, when the counter of the control unit is reset in a time relationship such that (Tg1 to Tg4) min <t115, the group arrival pulse that has arrived before time t115 cannot be recognized. Only the next transmitted ultrasonic signal can be detected.

Since correct coordinate calculation cannot be performed as it is, this is avoided in the present embodiment by the following algorithm.

That is, after the first arrival of a signal is detected, the maximum waiting time Tw for arrival of other signals after that is detected.
Is set as follows, and if the signals do not arrive at all the sensors within this range, it is determined that the relationship of (Tg1 to Tg4) min <t115 is satisfied, the counter is reset, and each sensor is newly added. Start to monitor the arrival of the signal.

That is, the maximum value (in the coordinate input area) of the time from when the signal is sent from the pen until it reaches each sensor is Tr0, the repetition cycle of the signal sent by the pen is Tr2, and the signal from the pen is Tr1 is the maximum value (in the coordinate input effective area) of the difference between the maximum and the minimum of the time from when the signal is sent to the time of reaching each sensor, which is the latest of the arrival times for a certain ultrasonic signal. Let Tr3 be the time between the object and the earliest arrival time for the ultrasonic signal transmitted next (in the entire effective area), and set Tr2 so that Tr1 << Tr3 Tr0 << Tr2. Then, an appropriate signal maximum waiting time Tw that satisfies Tr1 << Tw << Tr3 is determined (FIG. 6).

By the signal arrival time capturing algorithm as described above, the signal arrival time of each sensor with respect to a certain ultrasonic wave signal can be captured from all the sensors with reference to an appropriate certain time.

Next, a coordinate calculation algorithm for the obtained signal arrival time will be described.

In general, when the ultrasonic signal transmission time from the input pen is time-controlled in the control section, first, between the respective sensors and the pen, based on the algorithm described in the section "Prior Art". Then, the procedure of calculating the distance of, and then calculating the coordinate value of the pen based on them.

The method of calculating coordinate values from the distances between a plurality of pen sensors is a purely geometrical problem, but for example, FIG.
When the sensors (0) to (3) are arranged like 0 and the xy absolute coordinate system is taken as shown in FIG.

First, a straight line connecting the 0 sensor and the 1 sensor is X'1 coordinate system, and a straight line connecting the 2 sensor and the 3 sensor is Y'1.
Assuming a coordinate system, each coordinate value for the designated point p in FIG. 11 is given by the following equation.

[0060]

[Equation 1]

Here, X'1 is the distance between the sensors (0) to (1), Y'1 is the distance between the sensors (2) to (3), and R0 to R
3 is the distance from the pen to the sensors (0) to (3), respectively.

Then, by performing coordinate conversion (primary conversion) between the xy coordinates and the X'1 to Y'1 coordinates, the absolute coordinates of the input point p can be obtained.

X = D1 (x'1) + D2 (y'1) + GX y = D3 (x'1) + D4 (y'1) + GY where D1 to D4, GX, and GY are conversion constants, which are in the xy coordinate system. When the X'1-Y'1 coordinate systems are completely the same, D1
= D4 = 1, and 2 = D3 = GX = GY = 0.

However, in this embodiment, since the input from the pen is performed asynchronously with the arithmetic system, the signal arrival time (tg, tp) is from when the signal is transmitted by the sensor to when it reaches the sensor. It does not represent time but includes equal offsets among all the sensors, and the conventional method cannot accurately calculate the distance between the pen and the sensor. Therefore, in this embodiment, the distance between the pen and the sensor is calculated by adopting the following algorithm.

First, using the signal arrival time (tg, tp) of each sensor that has been taken in as it is, the n value is calculated by the same calculation formula as the conventional one.

Next, using this n value, the inter-pen-sensor distance R is calculated by the same formula as in the conventional case. As a result, the inter-pen-sensor distance R obtained is not the true distance Rr but has the same offset value Rofst in each sensor (the same applies to R2 to R4).

R1 = R1−Rr + Rofst On the other hand, in order to obtain the coordinate value of the designated point in the absolute coordinate system, when the time measurement is performed by the conventional method, as described above, the two (non-parallel) sensors are used. The coordinate value in the coordinate system may be calculated first, and the coordinate value may be converted into the absolute coordinate system.However, as described above, in the present embodiment, the calculated offset amounts are the same for each pen-sensor distance. Therefore, the correct absolute coordinate value cannot be obtained based on such a sensor coordinate system.

Therefore, in this embodiment, in order to obtain the absolute coordinate system, a plurality of ways of the two sensor coordinate systems are considered,
First, the absolute coordinate value including the calculated error is calculated. Since the coordinates are calculated using the wrong pen sensor distance, the calculated absolute coordinates naturally have different values depending on how the sensor coordinate system is used.

Then, it is assumed that the offset included in the distance between the pen sensors is back-calculated from the difference between the relative relationships, and the correct absolute coordinates corrected by that amount are calculated.

Now, consider three types of sensor coordinate systems for calculating absolute coordinate values, as shown in FIG. The formula for calculating absolute coordinate values based on each coordinate system is as follows.

[0071]

[Equation 2]

On the other hand, since the distance between the pen sensors includes the offset amount of ROFST in all the sensors, the absolute coordinate values calculated by the respective calculation formulas include the following error components for the x coordinate, for example. Naru (Rφr ~ R3
r represents the true distance from Rφ to R3).

X (1) = (true x) +2 (ROFST) {D1 (1/2
X'1) (R0r-R1r) + D2 (1 / 2Y'1)
(R2r-R3r)} x (2) = (true x) +2 (ROFST) {D'1 (1/2
X'2) (R2r-R1r) + D'2 (1 / 2Y'2)
(R1r-R3r)} x (3) = (true x) +2 (ROFST) {D ″ 1 (1/2
X'3) (R0r-R3r) + D "2 (1 / 2Y'3)
(R2r-R0r)} However, here, R0r-R1r = R0-R1 R2r-R3r = R2-R3 R2r-R1r = R2-R1 R1r-R3r = R1-R3 R0r-R3r = R0-R3R2r-R0r = R2. Since −R0, as shown in the following equation, x (1), x (2),
(ROFST) can be calculated from the difference of x (3).

X (1) -x (2) = 2 (ROFST) {D1
(1 / 2X'1) (R0r-R1r) + D2 (1/2
Y'1) (R2r-R3r) -D'1 (1 / 2X'2)
(R2r-R1r) -D'2 (1 / 2Y'2) (R1r
-R3r)} x (1) -x (3) = 2 (ROFST) {D1 (1 / 2X '
1) (R0r-R1r) + D2 (1 / 2Y'1) (R2
r-R3r) -D "1 (1 / 2X'3) (R0r-R3
r) -D "2 (1 / 2Y'3) (R2r-R0r)} x (2) -x (3) = 2 (ROFST) {D'1 (1/2
X'2) (R2r-R1r) + D'2 (1 / 2Y'2)
(R1r-R3r) -D "1 (1 / 2X'3) (R0r
-R3r) -D "2 (1 / 2Y'3) (R2r-R0
r)} Similarly, for y, (Rofst) can be obtained by three methods.

Back calculation is performed by the above six methods (ROFST)
In principle, the same value can be obtained, but each sensor has a finite measurement error, so
The reliability is improved by taking a method such as averaging the required (ROFST) among these 6 ways.

After all, the correction (ROFST) is used to perform the correction of subtracting the (Rofst) term from X (1) to X (3) and Y (1) to Y (3) ( It suffices to find the true x). The true y coordinate is also obtained by the same calculation.

As described above, the four sensors are used,
In the configuration in which the input pen is driven asynchronously, the input coordinates can be specified. The above method has the advantage that high-speed processing is possible because each coordinate calculation can be performed without using square root calculation at all.

<Second Embodiment> In the first embodiment,
As a measurement method that eliminates the timing difference between the measurement start reference time inside the control unit and the ultrasonic signal transmission time at the pen with all installed sensors, we adopted an algorithm that allows all sensors to obtain the arrival time for the same signal did. Therefore, for each sensor output signal, an analog signal processing circuit for determining the signal arrival time is required individually for each sensor.

In this method, the signal arrival time is determined by all the sensors at the same time for a certain signal, so that the processing time can be shortened and the coordinate input device can be used for character input or continuous curve input. Suitable when is required.

However, it is necessary to individually have an analog signal processing circuit for each signal to determine the signal arrival time, which increases the cost.

In the conventional synchronous type using a cord-connected input pen, an analog switch such as a multiplexer is provided in the input section of a 1-channel analog signal processing circuit, and this is shared by other sensors in a time division manner. A scheme has been proposed.

In the following, in such a system,
An algorithm that makes the timing difference between the measurement start time inside the control unit and the signal transmission time at the pen the same for all sensors is shown.

First, the signal transmission cycle on the pen side and the time measurement start cycle in the control unit are set to be the same.

This may be managed by a timer interrupt in the CPU so that the counter reset period for timing becomes the same as the signal transmission period on the pen side.

The method for determining the signal arrival times of all the sensors is as follows when, for example, n sensors (1) to (n) are used.

First, the signal arrival time of the sensor (1) is measured. When the signal arrival signal arrives within a fixed time, the signal arrival time at that time is temporarily stored. Next, the signal arrival time of the sensor (2) is measured. When a signal arrival signal arrives within a fixed time, the signal arrival time at that time is also temporarily stored.

As described above, if signals from (1) to (n) all arrive within a fixed time, the signal arrival time of each sensor stored up to that point is determined, and the coordinate calculation is started.

On the other hand, if the signal does not arrive within a certain time on the way, the counter is immediately reset and the signal arrival time is measured from the sensor. If the signal arrives within a fixed time, the signal arrival time is stored and the next sensor is operated.

After that, when the signals arrive cyclically and continuously at all the sensors within a fixed time, the signal arrival time of each sensor is fixed at that time, and the coordinate calculation is started.

With the above algorithm, all the sensors can measure the time so that the timing difference between the measurement start time and the signal transmission time becomes equal.

The variation in the timing difference among the sensors depends on the degree of coincidence between the measurement start cycle inside the control unit and the signal transmission cycle on the pen side. If the original clock is used for time management, for example, if there are about four sensors, fluctuations in the timing difference during the time measurement by the four sensors in order are sufficiently negligible.

The above processing flow is shown in FIGS. In each figure, n indicates the number of sensors. k represents the sensor number for detecting the signal arrival time, and s represents the number of sensors for which the arrival time has been detected.

Steps S31 to S33 in FIG. 12 show the counter reset for clocking and its synchronous control. This control is performed by the interrupt processing of FIG. The timing counter is synchronously controlled so as to have the same signal transmission cycle as the input pen.

In steps S34 and S35, the waiting time T
Wait for signal to reach sensor k during w. When the signal is detected by the sensor k, the next sensor is addressed (step S
36), the counter reset flag is cleared (step S37). Steps S38 to S40 show an increment process for cyclically addressing all the sensors,
In step S42, it is determined whether or not the transmission times of all the sensors have been acquired. The process after capturing the transmission times of all the sensors is the same as that of the above-described embodiment.

FIG. 13 shows a timer interrupt process for synchronizing the starting period of time measurement with the signal transmission period (making the difference disappear). When a CPU timer interrupt occurs,
The counter reset flag is set (step S51), and the counter is reset and restarted (step S52).

According to such a configuration, it is not necessary to individually have an analog signal processing circuit for determining the signal arrival time in each sensor, and there is an advantage that the manufacturing cost can be reduced.

[0097]

As is apparent from the above, according to the present invention, the vibration input from the input pen to the vibration transmission plate is detected by a plurality of vibration sensors provided on the vibration transmission plate.
In a coordinate input device that measures the vibration transmission time to the input pen and detects the input coordinates on the vibration transmission plate of the input pen based on the result, vibration is intermittently input to the vibration transmission plate at a predetermined cycle. A combination of a wireless input pen that incorporates all of the above mechanisms and a predetermined plurality of combinations of the vibration sensors, and a vibration transmission time to the vibration sensor from an appropriately determined reference time is used on the predetermined coordinate system. Calculate the input coordinate values, correct the time difference between the reference time and the actual vibration input time from the input pen based on the difference between the obtained coordinate values, and then calculate the input coordinates based on the obtained vibration transmission time. Since it adopts a configuration provided with a control means that does not require synchronous control of the input pen and coordinate calculation,
Accurate and fast coordinate input can be performed using an input pen that is completely wireless.

[Brief description of drawings]

FIG. 1 is a block diagram of a signal generation unit according to a first embodiment.

FIG. 2 is a block diagram of a control unit according to the first embodiment.

FIG. 3 is a flowchart showing an operation of a conventional example.

FIG. 4 is a timing chart showing an operation in the first embodiment.

FIG. 5 is a timing chart showing an operation in the first embodiment.

FIG. 6 is a timing chart showing an operation in the first embodiment.

FIG. 7 is a block diagram of a control unit of a conventional example.

FIG. 8 is a flowchart showing an operation in the first embodiment.

FIG. 9 is a timing chart showing the operation of the conventional example.

FIG. 10 is an explanatory diagram showing an outline of coordinate calculation.

FIG. 11 is an explanatory diagram showing an outline of coordinate calculation.

FIG. 12 is a flowchart showing an operation in the second embodiment.

FIG. 13 is a flowchart showing an operation in the second embodiment.

FIG. 14 is an explanatory diagram showing a schematic configuration of an ultrasonic coordinate input device.

FIG. 15 is a waveform diagram showing oscillator drive waveforms.

FIG. 16 is a block diagram showing a peak position detection circuit.

FIG. 17 is a block diagram showing an inflection point detection circuit.

FIG. 18 is a waveform diagram showing the operation of the signal detection circuit.

FIG. 19 is an explanatory diagram showing calculation of a vibration transmission distance.

[Explanation of symbols]

 1 Input Pen 2 Sensor 3 Propagator 4 Vibration Isolator 101 Oscillator 102 Counter Circuit 103 Drive Signal Generator 104 Piezoelectric Element 105 Pen Switch 106 Oscillator 107 Counter Circuit 108 Latch Circuit 109 Select Circuit 110 Data Bus 1 111 Data Bus 2 112 Start Signal 113 drive circuit

Claims (1)

[Claims] 1. A vibration input from an input pen to a vibration transmission plate is detected by a plurality of vibration sensors provided on the vibration transmission plate, a vibration transmission time to the input pen is measured, and the input is performed based on the result. A coordinate input device for detecting input coordinates of a pen on a vibration transmission plate, comprising: an input pen having a wireless structure, which includes all mechanisms for intermittently inputting vibrations to the vibration transmission plate at a predetermined cycle; Using a plurality of predetermined combinations of the above, the input coordinate value on the predetermined coordinate system is calculated using the vibration transmission time to the vibration sensor from the appropriately set reference time, and based on the difference between the obtained coordinate values. The coordinate input is characterized in that the time difference between the reference time and the actual vibration input time from the input pen is corrected, and control means for calculating the input coordinates based on the obtained vibration transmission time is provided. Apparatus.