JPH0562770B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a coordinate input device that detects a coordinate position based on the propagation delay time of an elastic wave, and is particularly aimed at improving detection accuracy.

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

One side is used as a resistor, and the resistive films for the x-coordinate and the y-coordinate are stacked, voltage or current is applied to each resistive film, and the point (coordinate input point) applied with a pen or fingertip is , a type that uses a resistive film to measure the voltage or current ratio, etc., and detect and input the coordinate position of that point.

By generating a local magnetic field pulse from the pen tip, bringing the pen tip close to one of the electrode wires wired in a matrix on the panel, electromagnetically coupling it, and measuring the current generated in the electrode wire. An electromagnetic induction type that detects and inputs the coordinate position of the pen tip.

Types that use ultrasound include those that measure positional 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 do.

[Problems to be Solved by the Invention] However, these conventional devices have the following drawbacks.

That is, in the above-mentioned resistive film type, the uniformity of the resistor directly affects the accuracy of graphic input, so a resistor with particularly excellent uniformity is required, and is therefore very expensive. Also, two resistive films are required, one for the x-coordinate and one for the y-coordinate.
It also has the disadvantage of reduced transparency.

Next, the electromagnetic induction type mentioned above is not transparent because the electric wires are arranged in a matrix.

Furthermore, if a device that uses surface waves or sound waves, such as the ultrasonic type described in the above section, has a flaw or an object, such as a hand, between the sound wave transmitter and receiver, the problem may occur. There is a drawback that the measurement point may be detected incorrectly due to an obstacle, or the measurement point may not be able to be measured. On the other hand, in the case of a conventional coordinate input device that uses plate waves of elastic waves, the group velocity and phase velocity of the elastic waves are different, so detection of the envelope peak or detection at a predetermined threshold (threshold) is difficult. The drawback was that an error of /2 wavelengths occurred.

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 the Problems] In order to achieve the above object, the present invention provides a vibration input means for inputting vibration, and a vibration propagation system that propagates the input vibration by contacting the vibration input means. a member, a vibration detection means provided on the vibration propagation member to detect the vibration input by the vibration input means, and a signal based on the phase velocity formed by the vibration detected by the vibration detection means. Based on the positive and negative thresholds set in the waveform, the propagation delay time corresponding to the positive threshold and the propagation delay time corresponding to the negative threshold of the signal based on the phase velocity. a derivation means for deriving;
The vibration propagation is determined based on the propagation delay times corresponding to the positive and negative thresholds derived by the deriving means and the context of the propagation delay times corresponding to the positive and negative thresholds. A coordinate deriving means for deriving the coordinates of the vibration input point of the member.

Moreover, the present invention preferably has, as one aspect thereof,
In order to correct the level of the signal output from the vibration detection means based on the phase velocity that changes according to the propagation delay time, an amplification means whose amplification factor changes according to the propagation delay time is combined with the vibration detection means. It may be characterized in that it is provided between the deriving means.

[Operation] In the coordinate input device of the invention, the vibration input by contacting the vibration input means is propagated by the vibration propagation member, and the vibration is detected by the vibration detection means provided on the vibration propagation member. In the present invention, a signal based on the phase velocity is generated based on the positive and negative thresholds set in the waveform of the signal based on the phase velocity, which is formed by the vibration detected by the vibration detection means. The propagation delay time corresponding to the positive threshold and the propagation delay time corresponding to the negative threshold are derived by the deriving means, and the propagation delay time corresponding to the derived positive and negative thresholds is calculated. Since the coordinates of the vibration input point of the vibration propagation member are derived by the coordinate derivation means based on the delay time and the context of the propagation delay time corresponding to the positive and negative thresholds, highly accurate coordinates can be obtained. Can input data.

[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 this figure, 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. 2 is a vibrator drive circuit, and an arithmetic control circuit 1
A pulse signal for driving the vibrator is generated in response to a synchronization signal from the oscillator. 3 is a vibrating pen for inputting coordinates, which includes a vibrator 4 such as a piezoelectric element that expands and contracts in response to a pulse signal from the vibrator drive circuit 2, and a horn with a pointed end that increases the amplitude of the vibration of the vibrator 4. 5, and a rod-shaped shaft portion that supports them.

6 is a sensor for driving reception, 7 is an anti-reflection material, 8
is a propagation medium that propagates vibrations and is transparent, such as glass. The sensors 6 are located at multiple predetermined locations (three corners in this example) of the propagation medium 8 that constitutes the signal input board.
It is made of, for example, a piezoelectric element, which is disposed in the propagation medium 8 and converts the vibration waves (plate wave elastic waves) of the pen 3 propagated through the propagation medium 8 into mechanical and electrical signals and extracts them as electrical signals. The antireflection material 7 is made of, for example, silicone rubber, 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. In the arithmetic control circuit 1, there are three sensors 6
The propagation delay time is detected from the signal indicating the propagation time sent from the received waveform detection circuit 9 through the received waveform detection circuit 9, and based on this propagation delay time, the coordinate position where the pen 3 is in contact is calculated by a predetermined calculation formula. .

Reference numeral 10 denotes a display drive circuit that is integrally disposed below a transparent propagation medium (for example, glass) 8 and drives a display 11 that displays characters, images, and the like. 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 almost in 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, 12 is a drive pulse signal applied to the vibrator 4 from the vibrator drive circuit 2, and the frequency of this pulse signal 12 is assumed to be the resonant frequency of the vibrator 4. 14 is sensor 6
The sensor signal (received signal) 15 outputted from the sensor signal 14 is the output signal of the received waveform detection circuit 9 obtained by processing this signal 14.

When the tip of the pen 3 comes into contact with the glass plate 8, which is a propagation medium, the vibration of the vibrator 4 driven by the pulse signal 12 as shown in FIG. 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. By using plate waves in this way, even if there are scratches or objects placed on the surface of the glass plate 8, there is almost no effect, and the sensor 6 can receive waveform elastic wave signals, making it easy to determine the position coordinates. This is because it can be detected.

By the way, the vibration waveform due to this plate wave does not have a constant shape because the group velocity and phase velocity are different.
That is, the velocity (group velocity) at which the overall shape (envelope) shown by 13 in FIG. Since the velocity (phase velocity) is different, the signal 14 becomes a carrier depending on the distance between the pen 3 and the sensor 6.
This is because a phenomenon occurs in which the phases of the waveforms 13 and 13 are different from each other with respect to the entire waveform 13. Therefore, when detecting the propagation delay time, 1 in Fig. 2 is propagated by the phase velocity of the detected waveform.
4 waveform is detected, and the second waveform for the detected waveform is detected.
The signal 15 in the figure is supplied to the arithmetic control circuit 1 to calculate the distance from the position of the pen 3 to each sensor 6 based on the delay time, calculate the x and y coordinates from this calculation result, and calculate the Information on the obtained X and Y position coordinates is transmitted to the display drive circuit 10 and displayed on the display 11 as an image such as a point or line. With the above configuration, it is possible to provide an input/output integrated digitizer for handwritten input.

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

As mentioned above, the error in the detected delay time depends on which part of the group of small waves of the signal 14 in FIG. It may occur about ±1/2 wavelength.

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 (phase) changes depending on the distance between the pen 3 and the sensor 6, as shown in A to D in FIG. 3, even if the moving distance of the pen 3 is extremely small, the detection delay time is approximately 1
It may move by the wavelength λ. Therefore, in this embodiment, in order to eliminate this one-wavelength error, the propagation delay time is detected using the velocity of a group of small waves (group velocity), and the coordinate position is calculated based on the detected time. .

For example, as shown in FIG. 4, a comparison is performed by setting a threshold at a level close to zero crossing for the detection waveform (waveform of the detection signal) 14' to obtain a signal indicated by 23'. This signal 2
Signal 2 indicating the propagation delay time Tp・r (phase・rise) of the waveform 14′ that detects the rising edge of, for example, the fourth digit of 3′.
Detected as 4'.

The relationship between the distance x between the pen 3 and one sensor 6 obtained by this detection and the propagation delay time Tp·r is shown in FIG. 5, for example. That is,
One detection point Tp・r・1 in Fig. 5
However, since two distance data A and B appear, it is necessary to correct them.

In the detection method shown in FIG. 4, the threshold is set at a level close to the zero crossing from the positive side of the detected waveform 14', but in this embodiment, the threshold is set at a level close to the zero crossing from the negative side of the detected waveform 14'. Comparison is performed by providing a threshold of 2, and a signal shown at 25' in FIG. 6 is obtained. This 2
Propagation delay time Tp・f of waveform 14', which is the same as the positive side of signal 5', detecting the falling edge this time.
It is detected as a signal 26' indicating (phase/fall).

Similarly to the above, the relationship between the distance x between the pen 3 and one sensor 6 and the detection propagation delay time Tp·f is shown in FIG. 7, for example. That is, Tp・f・1 is detected for the two distance data A and B obtained for Tp・r・1 shown in FIG. 5, and one distance data C for this Tp・f・1 is can get. In this way, the times of the fourth rise and fall from one detected waveform 14' are detected, and based on these two detection times, a distance with high accuracy and non-step-like linearity is calculated.
Find the relationship between propagation delay times. Next, an example of the detection process will be explained.

For example, distance information for Tp and r is stored in table 1A (first
(see figure) and store it. However, in the shaded area in Figure 7, one Tp/
Two distance data will be output for r, so
Using Tp·f as a criterion, one of the two distance data is selected and adopted.

Here, Tp·r and Tp.f always have a difference of time t ₁ corresponding to 1/2 wavelength of the detected waveform 14'. Also, in the shaded area in Figure 7, +t ₁ for Tp・r,
Alternatively, a time lag of −t ₁ occurs. Therefore, the seventh
To explain using the example shown in the figure, determining whether to use distance A or distance B for Tp・r・1 is as follows:
Since Tp.f.1 is a time of -t ₁ with respect to Tp.r.1, distance B is detected by assuming that Tp.r.1 corresponds to distance B. Further, for detection other than the shaded area in FIG. 7, the distance to Tp·r is extracted as is from the table 1A in the arithmetic and control circuit 1 described above, and the distance is detected.

Furthermore, if it is assumed that the distance to point A in FIG. 7 is an accurate position, Tp·f detected with respect to Tp·r·1 becomes Tp·f·2. At this time,
Since Tp・f・2=Tp・r・1+t ₁ , it is determined that it is point A.

FIG. 8 shows a specific configuration example of a received waveform detection circuit that executes the above-mentioned propagation delay time detection process.
As shown in FIG. 8, the detected waveform 14 received by the sensor 6 is amplified to some extent by the preamplifier circuit 21, and the amplified waveform 14' is further transmitted to the time-varying amplifying circuit 21.
Then, a change in the amplitude of the detected waveform 14' is corrected in accordance with the delay time to obtain a waveform 22' in which a detection error due to the amplitude is reduced. A positive comparator 23 has a comparator level on the positive side of this waveform 22', and a negative comparator 2 has a comparator level on the negative side.
5, the respective outputs 23' and 25' are processed by counters 24 and 26, which output signals for several pulses (fourth pulse in the above example), as Tp·r24' shown in FIG. Obtain the signal of Tp·f26'.

Next, these counter outputs 24' and 26' are input to the arithmetic and control circuit 1, and a highly accurate distance x is detected by referring to a pre-stored internal table 1A (see FIG. 1).

In this way, by measuring the distance x by detecting the dispersive phase velocity, the positional coordinates from each sensor 6 to the pen 3 are detected, and the coordinate information is displayed on the display 11 or sent to an external device, etc. Can be output.

FIG. 9 shows an example of the configuration of the above-mentioned time-varying amplification circuit 22. On the glass 8, as shown by the solid line 27 in FIG. 10, the amplitude changes as the amplitude voltage decreases with respect to the delay time, so the broken line 28 in FIG.
The output 14' of the preamplifier circuit 21 is corrected and calibrated using an amplifier circuit having an amplification factor as shown in FIG. Therefore, the characteristics and amplitude of the resistance _RDS between the drain and source of the FET (field effect transistor) change close to the exponential curve, so the charging and discharging characteristics of the capacitor C and the resistor R can be used to The configuration was as shown in Figure 9. Further, a time change start signal is sent from the arithmetic control circuit 1 in synchronization with the drive signal for the pen 3.

In the embodiment shown in FIG. 8, Tp·r is used as a reference, but it goes without saying that Tp·f may be used as a reference.

As explained above, according to the embodiment of the present invention, a signal indicating the propagation delay time is detected at the threshold level provided on both the positive side and the negative side of the detected waveform obtained by the sensor. Since the coordinate position of the vibrating pen is detected based on two signals and the phase velocity, the coordinate position can be detected with high accuracy.

In addition, in the embodiment of the present invention, a plate wave of an elastic wave is used to minimize the detection error caused by the difference between the group velocity and phase velocity, and the rise and fall of the detected wave and the phase velocity are used. Since the coordinate position is calculated and output using the digitizer, the resolution (accuracy) of the digitizer can be increased, and an input/output integrated type transparent digitizer can be easily constructed.

Further, according to the embodiment of the present invention, by adding a time-varying amplifier circuit, it is possible to reduce detection errors in delay time.

Further, in the embodiment of the present invention, by setting the number of pulses of a counter that measures propagation delay time, it is possible to select a pulse of a detection wave with a good S/N ratio, and detection with a small detection error can be performed.

Furthermore, according to the embodiment of the present invention, the counter for measuring the propagation delay time selects the number of pulses with a good S/N ratio and as close to the beginning as possible. It is possible to reduce the influence of reflections from
As a result, the effective area of the digitizer can be increased.

[Effects of the Invention] As explained above, according to the present invention, the positive side and negative side peaks set in the waveform of the signal based on the phase velocity formed by the vibration detected by the vibration detection means are Based on the threshold, the deriving means derives the propagation delay time corresponding to the positive threshold and the propagation delay time corresponding to the negative threshold of the signal based on the phase velocity, and the derived positive The vibration input of the vibration propagation member is performed by the coordinate derivation means based on the context of the propagation delay times corresponding to the side and negative side thresholds and the propagation delay times corresponding to the positive and negative side thresholds. Since the coordinates of a point are derived, it is possible to input highly accurate coordinate data.

[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. Figure 3 is 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 fixed threshold. Figure 4 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 constant threshold. Figure 5 is a characteristic diagram showing the relationship between the distance between the vibrating pen and the sensor and the propagation delay time obtained from the detected waveform in Figure 4, and Figure 6 is a graph showing the relationship between the positive and negative sides. A waveform diagram showing a detection waveform with a threshold of
FIG. 7 is a characteristic diagram showing the relationship between the distance between the vibrating pen and the sensor and the propagation delay time obtained from the detected waveform of FIG. 6, and FIG. 8 is a block diagram showing the configuration of the received waveform detection circuit of FIG. 1. FIG. 9 is a circuit diagram showing an example of the configuration of the time-varying amplification circuit shown in FIG. 8, and FIG. 10 is a characteristic diagram showing the attenuation characteristics of the detected waveform. 1... Arithmetic control circuit, 2... Vibrator drive circuit,
3... Pen (vibration pen), 4... Vibrator, 5...
Horn, 6... Sensor, 7... Anti-reflection material, 8...
...propagation medium (glass), 9...received waveform detection circuit,
DESCRIPTION OF SYMBOLS 10... Display drive circuit, 11... Display, 21... Preamplifier circuit, 22... Time varying amplifier circuit, 23... Positive side comparator, 24...
...Counter, 25...Negative side comparator, 26...
…counter.

Claims (1)

[Scope of Claims] 1. Vibration input means for inputting vibrations; A vibration propagation member that propagates the input vibration by contacting the vibration input means; A vibration propagation member provided on the vibration propagation member and configured to transmit the vibration input. vibration detection means for detecting vibration input by the vibration detection means; and positive and negative thresholds set in a waveform of a signal based on phase velocity formed by the vibration detected by the vibration detection means. a deriving means for deriving a propagation delay time corresponding to a positive threshold and a propagation delay time corresponding to a negative threshold of a signal based on the phase velocity; The coordinates of the vibration input point of the vibration propagation member are determined based on the propagation delay times corresponding to the positive and negative thresholds and the context of the propagation delay times corresponding to the positive and negative thresholds. A coordinate input device comprising: coordinate deriving means for deriving the coordinates. 2. In order to correct the level of the signal output from the vibration detection means based on the phase velocity that changes according to the propagation delay time, an amplification means whose amplification factor changes according to the propagation delay time is connected to the vibration detection means. 2. The coordinate input device according to claim 1, wherein the coordinate input device is provided between the deriving means and the deriving means.