JPS63100531A - Coordinate input device - Google Patents

Abstract

PURPOSE:To improve the resolution (precision) of a digitizer by measuring both of the group velocity and the phase velocity due to dispersion of a plane wave of an elastic wave and calculating the coordinate position on the basis of these velocities. CONSTITUTION:An calculating means is provided which calculates a distance (r) between the indicated point, with which an oscillating pen is brought into contact, and the detection point of a transducer in accordance with an equation 1 where upsilong, upsilonp, tg, tp lambdap, and terrg.p are the group velocity, the phase velocity, the group delay time, the phase delay time, the wavelength, and an error term respectively. Since both of the group velocity and the phase velocity due to dispersion of a plane wave of an elastic wave are measured and the coordinate position is operated based on these velocities, the resolution (precision) of the digitizer is improved. Since the distance (r) between the oscillating pen and the sensor is determined in accordance with the prescribed calculating equation based on the group velocity and the phase velocity, this device easily copes with the change of a constant or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a coordinate input device that detects coordinate positions based on the propagation delay time of elastic waves, and is particularly intended to improve detection accuracy.

[Prior Art] Conventionally, as a coordinate input device a called a digitizer or the like for inputting a coordinate position, for example, the following ones are known.

■ Overlap the resistive films for the X coordinate and the ylI mark with the - side as the resistor, apply voltage or current to each resistive film, and press the coordinate input point with a pen or fingertip.)
A resistive film type that measures the voltage or current ratio, etc., and detects and inputs the coordinate position of that point.

■ Generate a local magnetic field pulse from the pen tip,
A type exclusively for electromagnetic communication that detects and inputs the coordinate position of the pen tip by bringing the pen tip close to one of the electrode wires wired in a matrix on the panel, making an electromagnetic connection, and measuring the current generated in the electrode wire. Of things.

■ Types that use ultrasound include those that measure position coordinates by detecting the propagation delay time of surface waves through the ultrasound propagation medium, or those that transmit ultrasound into the air and measure the propagation time of the ultrasound. There are things to measure.

[Problem that the invention attempts to solve] However, these conventional devices have the following drawbacks.

In other words, in the above-mentioned 0-term resistive film type, the uniformity of the resistor directly affects the accuracy of graphic input.
In particular, it requires a resistor with excellent uniformity, which makes it very expensive. Furthermore, since two resistive films are required, one for the X-coordinate and one for the X-coordinate, there is also a drawback that the transparency is reduced.

Next, the above-mentioned 0-term electromagnetic 8 conductor type does not become transparent because the electric wires are arranged in a matrix.

Furthermore, if a surface wave or sound wave is used, such as the ultrasonic type described in Item 0 above, if there is a flaw or an obstacle such as a hand between the sound wave transmitting part and the receiving part,
These obstacles may cause problems such as erroneous detection of measurement points or failure to measure rice. On the other hand, in the case of conventional coordinate input devices that use plate waves of elastic waves, dispersion occurs, and the group velocity and phase velocity of the elastic waves are different, so it is necessary to detect the peak of the envelope and set a predetermined threshold. This detection has the disadvantage that an error of ±1/2 wavelength occurs.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks and provide a coordinate input device that is transparent, highly accurate, and easy to use.

[Means for solving problems].

In order to achieve such an object, the present invention brings a vibrating pen that generates mechanical vibration into contact with a signal input plate made of a vibration propagation medium, and arranges an elastic wave propagated to the vibration propagation medium at a predetermined position of the vibration propagation medium. A coordinate input device that detects the position coordinates of a vibrating pen by detecting the generated mechanical vibration with a conversion element that converts it into an electric signal and measuring the propagation delay time of an elastic wave based on the detected electric signal. The distance 1jir between the contacting pointing point and the detection point of the conversion element is calculated using the following formula (%), where υg is the group velocity, υp is the phase velocity, tg is the group delay time, tp is the phase delay time, and λp is the wavelength. ,terrg-p
is characterized in that it has an arithmetic means for calculating based on an error term.

[Function] In the present invention, both the group velocity and phase velocity due to the dispersion of the plate wave of the elastic wave are measured, and the coordinate position is calculated based on these velocities, so the resolution (accuracy) as a digitizer is improved. ), and in turn, it is possible to provide a transparent digitizer integrated with a human output. In addition, since the distance between the vibrating pen and the sensor is determined using a predetermined calculation formula based on group velocity and phase velocity, it is easy to respond to changes in constants, etc., and delay correction and offset It is also possible to easily incorporate corrections to improve accuracy.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows the overall configuration of a coordinate input device according to an embodiment of the present invention. In Kiguchi, 1 is an arithmetic control circuit that performs arithmetic operations and control according to the present invention, and is composed of, for example, a microcomputer, a RAM, and the like. Reference numeral 2 denotes a vibrator drive circuit, which generates a pulse signal for driving the vibrator in response to a synchronization signal from the arithmetic control circuit 1. Reference numeral 3 denotes a vibrator for coordinate human power, which includes a vibrator 4, such as a piezoelectric element, which expands and contracts in response to pulse signals from the vibrator drive circuit 2, and a pointed end that magnifies the amplitude of the imaging of the vibrator 4. It is composed of a horn 5 and a rod-shaped shaft portion that supports them.

6 is a sensor for receiving vibrations, 7 is an anti-reflection material, and 8 is a transparent propagation medium such as glass that propagates vibrations. The sensors 6 are disposed at a plurality of predetermined locations (in this example, three corners) of the propagation medium 8 that constitutes the signal input board, and convert the vibration waves (plate wave elastic waves) of the pen 3 propagated through the propagation medium 8 into mechanical and electrical signals. It is made of, for example, a piezoelectric element and is extracted as an electrical signal.

The reflective stopper 7 is made of silicone rubber, for example, and absorbs vibrations from the pen 3 and prevents the vibrations from being reflected at the end of the propagation medium 8.

9 is a received waveform detection circuit, which processes the signal received by the sensor 6 as described below and converts it into a signal indicating the propagation time of the elastic wave propagated within the propagation medium 8 from the pen 3 to the sensor 6; Output to the arithmetic control circuit 1. The arithmetic control circuit 1 detects the propagation delay time from the signals indicating the propagation time sent from the three sensors 6 via the reception waveform detection circuit 9, and uses a predetermined calculation formula based on the propagation delay time to detect the pen. 3. Calculate the contacting coordinate position.

Reference numeral 10 denotes a display 11 that is integrally disposed below a transparent propagation medium (for example, glass) 8 and displays characters, images, etc.
This is a display drive circuit that drives the . The coordinate information of the pen 3 calculated by the arithmetic control circuit 1 can be displayed on the display 11 through the display drive circuit 10 in almost real time, so that characters, figures, etc. drawn with the pen 3 can be displayed as they are on the display 11 instantly.

FIG. 2 shows signal waveforms and timing in the embodiment of FIG. In FIG. 2, reference numeral 12 is a drive pulse signal applied to the vibrator 4 from the vibrator drive circuit 2, and the pulse width of this pulse signal 12 is set to the resonance frequency of the vibrator 4. 14 is a sensor signal (received signal) output from the sensor 6, and 15 is an output signal of the received waveform detection circuit 9 obtained by processing this signal 14.

When the tip of the pen 3 touches the glass plate 8, which is the propagation medium,
The amplitude of the imaging of the vibrator 4 driven by the pulse signal 12 as shown in FIG. 2 is amplified through the horn 5 and transmitted to the glass plate 8. The vibration then becomes an elastic wave (ultrasonic wave) and propagates within the glass 8. At this time, plate waves are used as elastic waves. Using plate waves in this way,
Even if a flaw or an object is placed on the surface of the glass plate 8, there is almost no effect, and the sensor 6 can receive a waveform elastic wave signal, making it possible to easily detect the position coordinates. It is from.

By the way, the vibration waveform due to this plate wave does not have a constant shape because the group velocity and phase velocity differ due to dispersion. That is, the velocity (group velocity) at which the overall shape (envelope) shown by 13 in FIG. This is because, since the velocities (phase velocities) are different, a phenomenon occurs in which the phase of the carrier signal 14 becomes different with respect to the overall waveform 13 depending on the distance between the pen 3 and the sensor 6. Therefore, when detecting the propagation delay time, it is necessary to detect it using a method that minimizes the error caused by the difference between the group velocity and the phase velocity.

Next, specific means for detecting propagation delay time will be described in detail.

As mentioned above, the error in the detected delay time varies by ±172 depending on which part of the group of small waves of the signal 14 in FIG. Wavelengths may occur.

For example, if a predetermined threshold S is set for the signal 14 and extracted as a detection signal 15 as shown in B in FIG. 3, the position of small waves ( Since the phase) changes with the distance between Ben 3 and sensor 6, even if Ben 3 moves a very small distance, the detection delay time changes by about one wavelength λ, as shown by A-D in Figure 3. Sometimes it happens. Therefore, in this embodiment, in order to eliminate this one-wavelength error, the propagation delay is calculated based on the velocity of a group of small waves (group velocity) and the velocity of each small wave (phase velocity). The coordinate position is calculated based on this delay time.

For example, the received waveform detection circuit 9 detects the envelope 13 from the sensor output signal 14 shown in FIG. 2, and detects the peak of the envelope 13. This peak is taken as a signal with a delay time Tg based on the group velocity. The accuracy of the signal resolution of the detected delay time Tg is higher than when small waves are detected because a collection of small waves is measured as one wave. However, the signal of this delay time Tg can also roughly detect the distance with respect to the coordinates of the vibration occurrence position.

Therefore, in this embodiment, after detecting the signal with the delay time Tg, the zero-crossing rising point of one of the first small waves is detected, and this detected rising point is used as the signal with the propagation delay time τp. When the arithmetic control circuit 1 calculates the coordinate position from the rise of each signal of the propagation delay times Tg and Tp obtained using the group velocity and phase velocity and the rise of the first pulse of the drive pulse signal, an error occurs. It is possible to detect coordinate positions with high resolution (accuracy).

FIG. 4 shows an example of the configuration of a received waveform detection circuit 9 that detects a signal representing the above-mentioned propagation delay time tg-Tp for one sensor 6 among the sensors 6.

Moreover, FIG. 5 shows the waveform of the output signal of the circuit of FIG. 4.

Here, 6' indicates one of the plurality of sensors 6 in FIG. 19 is a preamplifier circuit that amplifies the signal received by this sensor 6', 20 is an envelope detection circuit that detects the envelope 13 from the optical signal 14 amplified by the preamplifier circuit 19, and 21 is a signal that is detected by the envelope detection circuit 20. This is an envelope peak detection circuit (for example, a differentiating circuit) that differentiates the envelope in order to detect the peak of the envelope 13.

22 is a Tg signal detection circuit (for example, a zero-cross comparator) that outputs a signal 22' representing the point where the signal 21' obtained by differentiating the envelope 13 crosses zero, that is, the propagation delay time Tg detected using the above-mentioned group velocity;
23 is an 11 stable multivibrator circuit which opens the gate for a certain period of time (creating a so-called window) from the rise of the signal 22' representing the propagation delay time Tg; 24 is a monostable multivibrator circuit 23 which opens the gate; This is a comparator level supply circuit that provides a comparator level of the comparator 26 at the time when the comparator 26 is in use. 25 is an envelope detection circuit 20. Envelope peak detection circuit 21. T
g signal detection circuit 22, monostable multivibrator 23.
This is a delay time adjustment circuit that adjusts the amount of time delayed through each circuit of the comparator level supply circuit 24. A signal 26' obtained by inputting the signal passing through the delay time adjustment circuit 25 and the comparator level generated by the comparator level supply circuit 24 to the comparator 2S is detected representing the propagation delay time Tp based on the phase velocity. Signal.

A signal 22' representing these propagation delay times rg and Tp
and 26', the arithmetic and control circuit 1 performs calculations to detect the coordinate position. An example of the procedure for detecting this coordinate position will be described in detail below.

As mentioned above, the propagation delay time Tg based on the group velocity is determined by counting from the time when the drive pulse signal 12 is output, but since this time is detected from the envelope of the detected wave, The detection accuracy is lower than the propagation delay time detected from . Therefore, calculating the distance between Ben 3 and the sensor 6 from the propagation delay time Tp detected from one of the detected waves is much more accurate than calculating from the propagation time T8 based on the group velocity.

However, as described above, the phase of each detected wave shifts due to the effects of dispersion. Therefore, when detecting the peak with the highest level in the signal 14 in FIG. 2, the relationship between the propagation path 1iIJl and the propagation time t becomes Tp in FIG.
It becomes as shown by i (however, i=1.2...). That is, as the tip position of the pen 3 continuously moves away from the sensor 6, the peaks change in the order shown by (A)-(B)-(C) in FIG. That is, at a certain distance, the a wave is at its peak, but gradually the b wave becomes the peak. Next, when the C wave reaches its peak, it will move like a lid. If the pen 3 is moved in the opposite direction, its peak movement will also be the opposite of that described above. When this peak movement is shown as a function of the propagation time t and the propagation path 11iii, it becomes a step-like movement curve as shown by Tpi in FIG.

Further, the zero-crossing points of waves a, b, and c exhibit similar movements.

By the way, since the propagation distance is calculated by counting the delay time, in the case of Tpi in FIG. 6, two values are obtained for the propagation distance l for one propagation delay time t. Therefore, by reading the value of the propagation delay time Tp based on the propagation delay time Tg, one propagation distance can be calculated with a highly accurate value based on Tp. A specific example of this is as follows.

Assuming that the propagation delay times Tg and Tp are detected as described above, Tp+ is in the range of jp+ for Tgr in the range of tgl in FIG. 6, and tp2 for Tgz in the range of jg2 in FIG. Tp2, t8 in the range
．． It is possible to sequentially detect one Tp for one sensor 6, and calculate the distance based on this Tpi.

That is, in FIG. 6, when the propagation distance is 1, one wavelength of the detected wave is λ, and the phase velocity is υp, the following equation (1) holds true.

f=VPTP+nλ ・(1) This above equation (1)
A distance 11J2 based on can be detected.

However, when Tg is in the range of tgl, n=o, 1 is j
g2. When the range of tgs is nxl, therefore, when the propagation delay times Tg and Tp are detected as described above, data conversion based on the above equation (1) is performed in the internal table IA of the arithmetic control circuit 1 (see Fig. 1). have this table IA
Using this, Tg is converted to the value of n in the arithmetic control circuit 1, and the values of phase velocity vp, propagation delay time Tp, constant n, and wavelength λ are substituted into equation (1) to calculate do. Through such calculations, sensor output signals are detected using the plurality of sensors 6, and the X and y coordinate positions are calculated and output.

Note that the delay time adjustment circuit 25 in FIG.
This circuit is not necessary if the delay time adjustment is counted from the beginning. Also, Tg and Tp
The internal table IA contains numerical values indicating the relationship between
Since Tg and Tp' are continuous straight lines, it is also possible to directly calculate the x and y coordinate position using the value of Tg'.

Furthermore, as shown in Figures 8 and 9, in group velocity detection, instead of envelope peak detection, the group velocity is detected by detecting the zero-crossing point of a waveform obtained by twice differentiating the envelope of the detected wave. It is also possible. By this double differentiation, a steeper detection point can be obtained than when detecting a zero crossing point with a single differentiation, that is, when detecting an envelope peak point, and detection can be performed with higher accuracy than envelope peak detection. When detecting peaks, it is affected by pen pressure, 37N of detection wave, etc.
In the case of zero-cross detection, accurate phase delay time Tp can be detected without being affected by these influences.

That is, 211 in FIG. 8 is a two-time differentiating circuit, and the fourth
It is connected in place of the envelope peak detection circuit 21 shown in the figure, and outputs the twice differentiated output waveform 211'' shown in FIG. ) is shown in FIG.

In this embodiment shown in FIG. 4, table 1^(
(see Figure 1) to determine the value of n and calculate the distance. However, using this table LA increases the memory capacity, and if the constants are changed, the table IA
This is inconvenient from a calibration point of view.

Therefore, in the embodiment of the present invention shown in FIG. 8, an arithmetic expression as described below is adopted, which allows easy calibration even for constant fluctuations.

First, as mentioned earlier, if the group delay time is tg, the phase delay time is tp, the group velocity is 'Jgh, the phase velocity is υp, and the wavelength is λp, the equation for each distance ir is the following equation (2),
It is given by equation (3).

r==votg...(2)
r=υ, tp+nλp ”' (3) (2
) and (3), n is given by equation (4).

n = [(V w tg v p tp)
/ λ2 Ko ・ (4) Here, n
is a positive integer including O. In equation (4), tg has an error within a certain range. This error is 1/N
Assuming λP (where N is a real number other than 0), n is expressed by the following formula (
5) is given by

In equation (5), N is set to 2.0, for example, and the calculation result on the right side is rounded down to the decimal point, and then the delay time t
If g fluctuates within ±172 cycles, the value of n is calculated. The value of N may be determined depending on the variation of tg.

That is, in equation (5), tg and tp are the delay time Δt and offset time jof as shown in FIG.
If these Δ1.1°f are included, a detection error will occur. Therefore, for each of tg and tp, these Δt, jo? When the value of is corrected, it becomes as shown in the following equation (6).

n = [(νg(tg-Δt)-tp(tp-Δt-
t,)r))/λ1+-]
...(6) Also, the formula (3) is the same as described above, and the value of the distance 1flfr described above becomes the following formula (7).

r=nλ, 10vp(tp-Δt-t,t)・(7)(6
) By substituting n determined by the equation (7), the error term is corrected, and the distance r between the pen 3 and the sensor 6 can be determined with high accuracy provided by the phase delay. Therefore, (6
) and (7), equation (8) is obtained with terrg-p as the error term.

r = f (υ,, tg, vp, tp,
Eh, terrg-p) = nλp + v p
(tp-terrp) - (8) where n; [(υ, (tg-terrg)-tp (tp-
terrp)/λ2+-] Also, round down to the decimal point in [], N≧1゜terrg
= Δt, terrp ``Δt+tor.'' In other words, the error term jerrg is the physical delay Δt from the rise of the vibrating pen drive signal to the detection by the sensor 6 due to the circuit delay and the horn passage time of the vibrating pen 3. ,
t is the phase offset. It consists of f. The arithmetic control circuit calculates the distance γ based on the above equations (7) and (8).

[Effects of the Invention] As explained above, according to the present invention, both the group velocity and the phase velocity due to the dispersion of the plate wave of the elastic wave are measured, and the coordinate position is calculated based on these velocities. So,
The resolution (accuracy) of the digitizer can be improved, and a transparent digitizer with integrated input and output ports can be provided.

Further, according to the present invention, since the distance between the vibrating pen and the sensor is determined using a predetermined calculation formula based on the group velocity and phase velocity, it is easy to deal with changes in constants, etc. In addition, delay correction and offset correction can be easily incorporated, and high accuracy can be achieved.

Further, according to the present invention, by providing a detection window using a monostable multivibrator and a comparator level supply circuit, it is possible to detect position coordinates with high accuracy without being affected by false detections.

Further, according to the present invention, by providing a delay adjustment circuit, accurate group delay time Tg and phase delay time Tp can be detected from the envelope and the detected wave, and position coordinates can be detected with high accuracy.

Furthermore, according to the present invention, when detecting the phase delay time Tp, instead of detecting the peak of the detected wave, by detecting the zero cross, the pen pressure when detecting the peak, the S/N of the detected wave, etc. It is possible to accurately detect the phase delay time Tp and to detect highly accurate position coordinates without being affected by the effects of the above.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the overall configuration of a coordinate input device according to an embodiment of the present invention. FIG. 2 is a block diagram showing the drive pulse signal of the vibrator shown in FIG. 1, the output signal of the sensor, and the propagation delay time detection signal. A waveform diagram showing the waveform and output timing. Figure 3 is a waveform diagram showing the principle that a detection error occurs when the waveform of the propagation delay time detection signal is detected at a certain threshold. Figure 4 is a waveform diagram showing the reception of Figure 1. A block diagram showing a configuration example of a waveform pressure detection circuit. Fig. 5 is a waveform diagram showing the waveform and output timing of the output signal of the circuit in Fig. 4. Fig. 6 is a relationship between distance and time between propagation delay times Tg and Tp. 7 (A), (B), and (C) are explanatory diagrams showing enlarged peaks and zero cross points near the peak of the detected wave,
Fig. 8 is a block diagram showing a modification of the embodiment of the present invention, Fig. 9 is a waveform diagram showing the waveform and output timing of the output signal of the circuit in Fig. 8, and Fig. 1O is the group delay time tg and phase delay time. FIG. 3 is an explanatory diagram showing delay correction and offset correction in tp. DESCRIPTION OF SYMBOLS 1... Arithmetic control circuit, 2... Vibrator drive circuit, 3... Pen (photographing pen), 4... Vibrator, 5... Horn, 6... Sensor, 7... - Anti-reflection material, 8... Propagation medium (glass), 9... Received waveform detection circuit, 10... Display drive circuit, 11... Display, 20... Envelope detection circuit, 21... Envelope peak detection circuit, 22...T
g signal detection circuit, 23... Monostable multivibrator, 24... Comparator level supply circuit, 25... Delay time adjustment circuit, 26... Comparator (Tp detection circuit), 211...
・Two-time differentiation circuit. Fig. 3 is the old tax map showing the scarcity correction and the offset cotton ball, which shows Yoshiyake's right number rail in the row of shells.
Figure 0

Claims (1)

[Claims] 1) A vibrating pen that generates mechanical vibration is brought into contact with a signal input plate made of a vibration propagation medium, and an elastic wave propagated to the vibration propagation medium is disposed at a predetermined position of the vibration propagation medium. A coordinate input device that detects the positional coordinates of the vibrating pen by detecting mechanical vibrations generated by a transducer with a conversion element that converts them into electrical signals, and measuring the propagation delay time of the elastic waves based on the detected electrical signals, The distance r between the pointing point that the vibrating pen is in contact with and the detection point of the conversion element is calculated using the following formula: r=f(υg, fg, υp, tp, λp, terrg・
p) However, υg is group velocity, υp is phase velocity, tg is group delay time, tp is phase delay time, λp is wavelength, terrg
- A coordinate input device characterized in that p has an arithmetic means for calculating based on an error term. 2) In the device according to claim 1, the error term terrg·p is determined by the physical difference between the rise of the vibrating pen drive signal and the detection by the conversion element due to circuit delay, horn passage time of the vibrating pen, etc. Δt which is the delay
and t_o_f, which is a phase offset.