JP2537537B2 - Coordinate input device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a coordinate input device, and more particularly to vibration transmission of the vibrating pen by detecting vibration input from a vibrating pen by a vibration sensor provided on a vibration transmitting plate. The present invention relates to a coordinate input device that detects coordinates on a board.

[Prior Art] In the coordinate detection method as described above, since the structure of the vibration transmission plate forming the input tablet is simple and the transparent material can be used as the vibration transmission plate, it can be overlaid on the display, the original, etc. It has the advantage that it can be arranged.

In this type of coordinate input device, the input vibration from the vibrating pen is detected by a plurality of vibration sensors provided on the vibration transmission plate. However, the influence of the phase delay during the vibration transmission on the vibration transmission plate and the detection circuit The correct coordinate value cannot be detected unless the influence of the circuit delay time is corrected. The circuit delay includes not only an electric circuit but also a delay inherent in a circuit in which vibration is mechanically transmitted between the vibrating pen and the vibration transmission plate.

[Problems to be Solved by the Invention] In FIG. 8, the horizontal axis represents time t, and the vertical axis represents the vibration transmission distance from the input point to the vibration sensor. The group delay time tg in which the envelope of the vibration waveform advances a certain distance. And shows the change of the phase delay time tp in which the phase of the waveform advances.

As shown in the figure, the circuit delay time et is always included even at the distance 0, and the curve (straight line) of each delay time is offset to the right in the graph. Also, the phase waveform causes a regular phase delay according to the wavelength as shown, but the difference tof between the group delay time tg and the phase delay time at the distance 0, that is, the phase offset changes due to the effect of the circuit delay time. To do.

In the method of measuring the vibration transmission time by detecting the transverse wave component on the vibration transmission plate, a method of determining the vibration transmission time using both the group delay time tg and the phase delay time tp is known. In such a method, the correct vibration transmission time cannot be obtained unless the circuit delay time et and the phase offset tof are corrected.

Therefore, conventionally, there is known a method of correcting the vibration transmission time by storing a correction value according to the average circuit delay time et and the phase offset tof measured in advance and subtracting the correction value from the measured value.

However, this circuit delay time et and phase offset tof
For the determination of, it is necessary to perform arithmetic on the data sampled at a certain point using constants such as group velocity, phase velocity, and period. Therefore, the error of the value of velocity, etc. Due to the above error, the accuracy of the coordinate determination may be degraded.

In addition, since the actual circuit delay time changes according to environmental changes such as temperature, the conventional method has a problem that it is not possible to accurately measure the vibration transmission time regardless of changes in environmental conditions.

 An object of the present invention is to solve the above problems.

[Means for Solving the Problems] In order to solve the above problems, in the present invention, the vibration input from the vibrating pen is detected by a plurality of vibration sensors provided on the vibration transmitting plate to detect the vibration of the vibrating pen. In a coordinate input device for detecting coordinates on a transmission plate, a delay time from generation of a drive signal pulse to detection of a detection timing signal at a predetermined point at a known distance from the vibration sensor is measured, and the delay time is measured. Storage means for storing
The delay time from the generation of the drive signal pulse to the detection of the detection timing signal of the input applied to the arbitrary point on the vibration transmission plate is measured, and the delay time and the delay time stored in the storage means are A means for deriving the vibration transmission time in the vibration transmission plate from the arbitrary point to the predetermined point from the difference is provided, and the distance from the arbitrary point to the predetermined point or the vibration sensor is derived from the derived vibration transmission means. The derivation means is provided.

[Operation] According to the above configuration, the vibration transmission time from the predetermined point to each vibration sensor and the vibration transmission time from the input point to each vibration sensor similarly include the circuit delay time and the phase offset time. Therefore, it is possible to calculate the vibration transmission time by removing the circuit delay time and the phase offset time by subtracting them. This vibration transmission time corresponds to the distance from the predetermined point measured from the vibration sensor position to the input point, so if coordinate calculation is performed based on this vibration transmission time, it will be accurate regardless of the effects of circuit delay time and phase offset time. It is possible to obtain various coordinate values.

[Examples] Hereinafter, the present invention will be described in detail based on examples shown in the drawings.

FIG. 1 shows the structure of an information input / output device adopting the present invention. The information input / output device of FIG. 1 causes the input tablet composed of the vibration transmission plate 8 to input coordinates by the vibrating pen 3, and the display device 11 'composed of a CRT arranged on the input tablet according to the input coordinate information. The input image is displayed on.

The reference numeral 8 in the drawing denotes a vibration transmission plate made of acrylic, glass plate or the like, which transmits vibration transmitted from the vibration pen 3 to three vibration sensors 6 provided at the corners. In this embodiment, the coordinate of the vibration pen 3 on the vibration transmission plate 8 is detected by measuring the transmission time of the ultrasonic vibration transmitted from the vibration pen 3 to the vibration sensor 6 via the vibration transmission plate 8.

The vibration transmitting plate 8 has its peripheral portion supported by an antireflection material 7 made of silicon rubber or the like in order to prevent the vibration transmitted from the vibrating pen 3 from being reflected at the peripheral portion and returning toward the central portion. ing.

The vibration transmitting plate 8 is arranged on a display device 11 'capable of displaying dots, such as a CRT (or a liquid crystal display device), and displays dots at the position traced by the vibration pen 3. That is, a dot display is performed at a position on the display 11 ′ corresponding to the detected coordinates of the vibrating pen 3, and the image composed of elements such as points and lines input by the vibrating pen 3 is written on paper. Appears after the locus of the vibrating pen as you did.

Further, according to such a configuration, a menu is displayed on the display 11 ', and the vibrating pen is used to select the menu item, or a prompt is displayed to bring the vibrating pen 3 into contact with a predetermined position. Can also be used.

Further, a mark 8a is provided at a predetermined position (the position is completely arbitrary) on the input surface of the vibration transmission plate 8. In the present embodiment, the coordinates of the mark 8a are stored in advance in the ROM or the like, the vibration input is performed by the vibration pen 3, the vibration transmission time to each vibration sensor 6 is measured, and the measured value is corrected for the vibration transmission time. Used for. The correction method will be described later in detail.

The vibration pen 3 for inputting ultrasonic vibrations to the vibration transmission plate 8 is
It has a vibrator 4 composed of a piezoelectric element or the like inside, and transmits the ultrasonic vibration generated by the vibrator 4 to the vibration transmission plate 8 via the horn portion 5 having a sharp tip.

FIG. 2 shows the structure of the vibrating pen 3. Vibrating pen 3
The vibrator 4 built in is driven by the vibrator drive circuit 2. The drive signal for the vibrator 4 is supplied as a low-level pulse signal from the arithmetic and control circuit 1 in FIG. 1, amplified by a predetermined gain by the vibrator drive circuit 2 capable of low impedance driving, and then the vibrator 4 Applied to.

The electric drive signal is converted into mechanical ultrasonic vibration by the vibrator 4 and transmitted to the diaphragm 8 via the horn unit 5.

The vibration frequency of the vibrator 4 is selected to a value capable of generating a plate wave on the vibration transmission plate 8 such as acrylic or glass. Further, when driving the vibrator, the second
A vibration mode in which the vibrator 4 mainly vibrates in the vertical direction in the figure is selected. Further, by setting the vibration frequency of the vibrator 4 as the resonance frequency of the vibrator 4, it is possible to perform efficient vibration conversion.

The elastic wave transmitted to the vibration transmitting plate 8 as described above is a plate wave, and has an advantage that it is less susceptible to scratches and obstacles on the surface of the vibration transmitting plate 8 as compared to surface waves.

Again, in FIG. 1, the vibration sensor 6 provided at the corner of the vibration transmission plate 8 is also composed of a mechanical-electrical conversion element such as a piezoelectric element. The output signals of the three vibration sensors 6 are input to the waveform detection circuit 9, and the timing of vibration arrival at each sensor is detected by the waveform detection processing described below. This detection timing signal is input to the arithmetic control circuit 1.

The arithmetic control circuit 1 detects the vibration transmission time to each sensor according to the detection timing input from the waveform detection circuit, and further detects the coordinate input position of the vibration pen 3 on the vibration transmission plate 8 from this vibration transmission time.

The detected coordinate information of the vibrating pen 3 is processed in the arithmetic and control circuit 1 according to the output system by the display 11 '.
That is, the arithmetic control circuit controls the output operation of the display 11 'via the video signal processing device 10 based on the input coordinate information.

FIG. 3 shows the structure of the arithmetic control circuit 1 of FIG. Here, the structure of the drive system of the vibration pen 3 and the vibration detection system by the vibration sensor 6 is mainly shown.

The microcomputer 11 has an internal counter, a ROM 11a and a RAM 11b built therein. The coordinate value of the mark 8a is stored in the ROM 11a. Further, the RAM 11b has a correction value used for a vibration transmission time correction described later, that is, the vibration transmission plate 8
The transmission time of the vibration input from the mark 8a to each vibration sensor 6 is stored.

The drive signal generation circuit 12 outputs a drive pulse of a predetermined frequency to the vibrator drive circuit 2 in FIG. 1, and is started by the microcomputer 11 in synchronization with a coordinate calculation circuit.

The count value of the counter 13 is latched in the latch circuit 14 by the microcomputer 11.

On the other hand, the waveform detection circuit 9 outputs timing information of a detection signal for measuring a vibration transmission time from an output of the vibration sensor 6 as described later. These pieces of timing information are input to the input ports 15, respectively.

The timing signal input from the waveform detection circuit 9 is input to the input port 15 and each of the vibration sensors 6 in the latch circuit 14
Is stored in the storage area corresponding to the result of the calculation, and the result is transmitted to the microcomputer 11.

That is, the vibration transmission time is expressed as a latch value of the output data of the counter 13, and the coordinate calculation is performed based on this vibration transmission time value. At this time, the determination circuit 16 determines whether or not all the waveform detection timing information from the plurality of vibration sensors 6 has been input, and notifies the microcomputer 11 of this.

The output control processing of the display 11 'is performed via the input / output port 17.

FIG. 4 illustrates a detection waveform input to the waveform detection circuit 9 of FIG. 1 and a vibration transmission time measuring process based on the detection waveform. In FIG. 4, reference numeral 41 denotes a drive signal pulse applied to the vibration pen 3. The ultrasonic vibration transmitted to the vibration transmission plate 8 from the vibration pen 3 driven by such a waveform passes through the inside of the vibration transmission plate 8 and is detected by the vibration sensor 6.

After traveling within the vibration transmission plate 8 for a time tg corresponding to the distance to the vibration sensor 6, the vibration reaches the vibration sensor 6. Reference numeral 42 in FIG. 4 indicates a signal waveform detected by the vibration sensor 6. The plate wave used in this embodiment is a dispersive wave, and therefore the relationship between the envelope 421 and the phase 422 of the detected waveform changes according to the vibration transmission distance.

Here, the speed at which the envelope advances is defined as the group speed Vg, and the phase speed is defined as Vp. The distance between the vibration pen 3 and the vibration sensor 6 can be detected from the difference between the group velocity and the phase velocity.

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 as indicated by reference numeral 43 in FIG. 4, the distance between the vibrating pen 3 and the vibration sensor 6 is detected. d is the vibration transmission time tg, d = Vg · tg (1) This equation relates to one of the vibration sensors 6, but the same equation can be used to calculate the distance between the other two vibration sensors 6 and the vibration pen 3. Can be shown.

Further, in order to determine the coordinate value with higher accuracy, processing based on the detection of the phase signal is performed. Phase waveform of Fig. 4
If the time from the specific detection point of 422, for example, the application of vibration to the zero crossing point after passing the peak is tp, the distance between the vibration sensor and the vibration pen is d = n · λp + Vp · tp (2). Here, λp is the wavelength of the elastic wave, and n is an integer.

From the above equations (1) and (2), the integer n is expressed as follows: 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 and n is within ± 1/2 wavelength, n can be determined.

The distance between the vibration pen 3 and the vibration sensor 6 can be accurately measured by substituting n obtained as described above into the expression (2).

In order to measure the two vibration transmission times tg and tp shown in FIG. 4, the waveform detection circuit 9 can be constructed, for example, as shown in FIG.

In FIG. 5, the output signal of the vibration sensor 6 is amplified to a predetermined level by the above-mentioned amplifier circuit 51.

The amplified signal is input to the envelope detection circuit 52, and only the envelope of the detection signal is extracted. The timing of the peak of the extracted envelope is detected by the envelope peak detection circuit 53. The peak detection signal is formed into an envelope delay time detection signal Tg having a predetermined waveform by a signal detection circuit 54 composed of a mono multivibrator or the like, and input to the arithmetic control circuit 1.

Also, the timing of this Tg signal and the delay time adjustment circuit
The phase delay time detection signal Tp is formed by the detection circuit 58 from the original signal delayed by 57 and is input to the arithmetic control circuit 1.

That is, the Tg signal is converted into a pulse having a predetermined width by the monostable multivibrator 55. Further, the comparator level supply circuit 56 forms a threshold value for detecting the tp signal according to the pulse timing. As a result, the comparator level supply circuit 56 forms the signal 44 having the level and timing as indicated by reference numeral 44 in FIG.
To enter.

That is, the monostable multivibrator 55 and the comparator level supply circuit 56 are for allowing the measurement of the phase delay time to operate only for a fixed time after the envelope peak is detected.

This signal is a detection circuit composed of a comparator, etc.
It is input to 58 and compared with the detection waveform delayed as shown in FIG. 4, and as a result, a tp detection pulse such as reference numeral 45 is formed.

The circuit shown above is for one of the vibration sensors 6,
The same circuit is provided for each of the other sensors. If the number of sensors is generalized to be h, the envelope delay time Tg1 to h and the phase delay time Tp1 to h are h, respectively.
The individual detection signals are input to the arithmetic control circuit 1.

In the arithmetic control circuit of FIG. 3, the signals Tg1 to h and Tp1 to h are input from the input port 15, and the count value of the counter 13 is fetched into the latch circuit 14 with each timing as a trigger. As described above, since the counter 13 is started in synchronization with the driving of the vibrating pen, the latch circuit 14 receives the data indicating the delay time of each of the envelope and the phase.

As shown in FIG. 6, when the three vibration sensors 6 are arranged at the corners of the vibration transmission plate 8 at the positions S1 to S3, the processes described with reference to FIG. The straight line distances d1 to d3 to the position of the vibration sensor 6 can be obtained. Further, in the arithmetic control circuit 1, this linear distance d1 ~
Based on d3, the coordinates (x, y) of the position P of the vibrating pen 3 can be obtained from the Pythagorean theorem as follows.

x = X / 2 + (d1 + d2) (d1-d2) / 2X (4) y = Y / 2 + (d1 + d3) (d1-d3) / 2Y (5) where X and Y are the positions of S2 and S3. Vibration sensor 6 and origin (distance along the X and Y axes of the sensor at position S1).

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

Next, in the above configuration, a correction process for removing the influence of the circuit delay time et and the phase offset time tof in the above-described calculation between the pen-sensor distance and the coordinate determination will be described.

The vibration transmission time latched by the latch circuit 14 includes a circuit delay time et and a phase offset time tof. The error caused by these is always included in the same amount when the vibration is transmitted from the vibration pen 3 to the vibration transmission plate 8 and the vibration sensor 6.

Therefore, for example, the distance from the position of the mark 8a in FIG. 1 to one of the vibration sensors 6 is R, and the measured vibration transmission time from the mark 8a to the sensor is tg'r, tp'r,
Also, the true transmission time from the mark 8a to the sensor is tgr, t
Assuming pr, these have a relationship of tg'r = tgr + et (6) tp'r = tgr + et + tof (7) with respect to the circuit delay time et and the phase offset tof.

On the other hand, measured values tg'p, tp'p at arbitrary input point P
Similarly, tg′p = tgp + et (8) tp′p = tpp + et + tof (9) When the difference between the two is calculated, tg′p−tg′r = (tgp + et) − (tgr + et) = tgp−tgr
(10) tp'p-tp'r = (tpp + et + tof)-(tgr + et + tof) = tpp-tpr (11), the circuit delay time et and the phase offset tof included in each transmission time are removed, and the mark 8a It is possible to obtain the difference in the true vibration transmission time according to the distance from the position to the input point P with the sensor position as the starting point.

The distance difference between the two points can be obtained by using the above equations (2) and (3) for the time difference value, and the distance R from the mark 8a to the sensor is stored in advance in the ROM 11a and is known. Therefore, if the sum of these is obtained, the distance between the input point and the sensor can be determined, and the above (4), (5)
The coordinate position can be determined by calculating the formula.

Correction values tg'r, t due to vibration input to the position of mark 8a
The acquisition of p'r may be performed at a predetermined timing, for example, by prompting the operator by displaying on the display 11 'immediately after turning on the power. Alternatively, the acquisition of the correction value may be performed every predetermined time during operation. The acquired correction value may be stored in the RAM 11b.

If the above correction is always performed during the operation, it is possible to appropriately correct the change in the circuit delay time or the like caused by the influence of the environmental change. However, it is possible to properly correct at least the circuit delay and the phase offset, which have variations in each device, by a method in which a correction value is fetched at the time of factory shipment and the data is stored in a non-volatile memory or the like.

In the above-described embodiment, it is necessary to measure the delay time at the known position of the mark 8a, and the operator is required to accurately input the coordinate at the position of the mark 8a. But,
By using the following method, it is possible to input coordinates for inputting a correction value at an arbitrary position.

That is, the coordinate is determined from the hyperbolic function by using the delay time difference between the sensors, and the delay time is corrected from the value.

The coordinate determination based on the delay time difference is, for example, when the sensors are arranged as shown in FIG.
If the difference in distance between them is b, the designated point (x, y) is obtained as the intersection of the hyperbolic functions as in the following equation.

However ^{c 2 = 4X 2 -a 2,} d 2 = 4Y 2 -b 2, c 2 d 2 -a 2 b 2> 0 can determine the coordinates of an arbitrary input point by these formulas.
RAM1 is used as the correction value for the vibration transmission time to each sensor at this time.
If it is stored in 1b, the above correction processing can be performed.

According to such a method, the correction value can be acquired at an arbitrary position, so that the user can easily perform the correction. Also, for example, if this operation is performed regularly or irregularly at fixed time intervals (for example, when an arbitrary area is being input during coordinate input), the correction value is automatically loaded without the user being aware of it. You can Further, it becomes possible to completely correct a change in circuit delay time due to a change in temperature.

However, as you can see from Eqs. (12) and (13), the arithmetic operation using the microprocessor becomes very complicated.
The method described above is more advantageous for real-time coordinate determination in terms of accuracy and calculation speed.

However, when the correction value is fetched as in the present embodiment, there is not much time limitation and the number of digits for calculation can be increased, so that it can be sufficiently used for coordinate determination.

Needless to say, even with the sensor arrangement as shown in FIG. 7, the coordinates can be determined by the Pythagorean theorem as described above.

In the above embodiments, the coordinate input device using a plate wave was mainly described, but the configuration of the present invention is not limited to this, and it is applicable to various types of coordinate input devices that mediate vibration transmission. Needless to say.

[Effects of the Invention] As is apparent from the above, according to the present invention, the delay time from the generation of the drive signal pulse to the detection of the detection timing signal at a predetermined point at a known distance from the vibration sensor is measured and stored. Also, the same delay time is measured with respect to an input applied to an arbitrary point on the vibration transmission plate, and the vibration transmission in the vibration transmission plate from an arbitrary point to a predetermined point is determined from the difference between the measured time and the stored delay time. Since the time is obtained and the distance from the arbitrary point to the predetermined point or the vibration sensor is obtained from this vibration transmission time, the circuit is obtained by subtraction when calculating the vibration transmission time corresponding to the distance from the predetermined point to the input point. The effects of delay time and phase offset time can be eliminated, and the delay time in the transmission path of vibration or signal other than the transmission delay time propagating on the vibration transmission plate As a result of being able to exclude the influence between the two, accurate coordinate values can be obtained regardless of changes in environmental conditions.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing the configuration of an information input / output device adopting the present invention, FIG. 2 is an explanatory diagram showing the structure of the vibrating pen of FIG. 1, and FIG. 3 is an arithmetic control circuit of FIG. 4 is a block diagram showing the structure of FIG. 4, FIG. 4 is a waveform diagram showing a detection waveform for explaining the distance measurement between the vibrating pen and the vibration sensor, and FIG. 5 is a block showing the configuration of the waveform detection circuit of FIG. 6 and 6 are explanatory views showing the arrangement of vibration sensors, FIG. 7 is an explanatory view showing the arrangement of sensors in different embodiments, and FIG. 8 is a diagram showing the problems of the conventional coordinate input device. is there. 1 ... Arithmetic control circuit, 3 ... Vibration pen 4 ... Vibrator, 6 ... Vibration sensor 8 ... Vibration transmission plate, 8a ... Mark 11 ... Microcomputer 11a ... ROM, 11b ... RAM

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Noriyuki Suzuki 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Katsuyuki Kobayashi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Incorporated (72) Inventor Shigeki Mori 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Innovator Shinnosuke Taniishi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) References JP-A-59-41090 (JP, A)

Claims (2)

(57) [Claims] 1. A coordinate input device for detecting vibrations input from a vibrating pen by a plurality of vibration sensors provided on a vibration transmitting plate to detect coordinates of the vibrating pen on the vibration transmitting plate. At a given point at a known distance,
A delay time from the generation of the drive signal pulse to the detection of the detection timing signal is measured, and a storage means for storing the delay time and a detection of the drive signal pulse of an input made at an arbitrary point on the vibration transmission plate are detected. The delay time until the timing signal is detected is measured, and the vibration transmission time in the vibration transmission plate from the arbitrary point to the predetermined point is derived from the difference between the delay time and the delay time stored in the storage means. And a deriving unit that derives a distance from an arbitrary point to a predetermined point or the vibration sensor from the derived vibration transmission time. 2. The coordinate input device according to claim 1, further comprising informing means for informing the predetermined point.