JPS636619A - Coordinate input device - Google Patents

Abstract

PURPOSE:To improve the resolution of a coordinate input device by measuring both the group velocity due to dispersion and the phase velocity and calculating a coordinate position. CONSTITUTION:This coordinate input device consists of an arithmetic control part 1 which performs the overall control and calculates a coordinate position, a coordinate input pen 3, a vibrator driving circuit 2 which transmits the pulse signal to a piezoelectric element 4, a transmission medium of glass, etc., a received waveform detecting part 9, a display drive part 10, etc. The relevant coordinates are indicated on the medium 8 by the pen 3 and the elastic waves are received by piezoelectric elements 6a-6c as detecting signals. Based on these detecting signals, the part 1 calculates the position coordinates of the pen 3 and displayed on a display 11. In this detection mode a delay time of transmission is detected based on the group velocity of detected waves and the velocity (phase velocity) of the detected wave for calculation of the coordinate position. Thus the error is reduced to the detected delay time and the detecting accuracy is improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a coordinate detection device using elastic waves, and particularly relates to a coordinate input device that detects coordinate positions using plate waves in elastic waves. .

[Prior Art] Conventionally, in this type of device that uses elastic waves, a start signal is output from an amplification calculation circuit or the like to a pulse generator, and the pulse generator generates a pulse electric signal in response to the start signal. Vibration generated by a driven piezoelectric element is propagated as an elastic wave to a vibration propagation body through the tip (horn) of a vibrating pen for coordinate manual use, for example. This is detected as a piezoelectric voltage by a sensor piezoelectric element, synchronized with a start signal, and the delay time until it is detected by each sensor piezoelectric element is repeatedly measured, and the position coordinates of the vibration oscillation source (pen tip) are determined. was detected.

[Problems to be solved by the invention] However, if there is an object, scratch, hand, etc. between the vibrating pen and the piezoelectric element that receives the elastic waves, the elastic waves will be attenuated by the obstruction, and the calculation will be difficult. There is a problem in that the coordinate positions determined may be different, and further problems such as inability to measure occur.

Therefore, it is possible to use plate waves that are less attenuated by obstacles. However, as the elastic wave propagates, dispersion occurs, and the group velocity and phase velocity are different. Therefore, when a threshold level is set and a predetermined pulse in the received pulse group is detected, the phase velocity Against ±
There is a drawback that an error of 1/2 wavelength (1 wavelength) occurs.

The present invention has been made in view of the above-mentioned prior art, and it is an object of the present invention to provide a coordinate input device that is highly accurate and easy to use.

[Means for solving the problem] In order to solve this problem, the present invention has the following configuration.

That is, a position specifying means for specifying a desired position on a coordinate input board and energizing the coordinate input board to generate an elastic wave;
a plurality of receiving means fixed at predetermined positions on the coordinate input board for receiving the elastic waves and generating electrical signals corresponding to the intensity thereof; and a plurality of receiving means for detecting the propagation time of the group velocity of the elastic waves from the electrical signals. a first detection means, a second detection means for detecting the propagation time of the phase velocity of the elastic wave from the electric signal, and a position specifying means based on the propagation time value detected by the first and second detection means. and calculation means for calculating the specified coordinate position.

[Operation] In the configuration of the present invention, the coordinate position of the position specifying means is calculated by the calculating means based on the propagation times detected by the first and second detecting means.

DESCRIPTION OF THE PREFERRED EMBODIMENTS [Embodiments] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[Description of overall configuration diagram] FIG. 1 is an overall configuration diagram of the coordinate input device according to the present embodiment.

In the figure, reference numeral 1 denotes an arithmetic control unit that controls the entire apparatus and calculates the coordinate position, and transmits the detected coordinate position to an external host computer or the like as necessary. 2 is a vibrator drive circuit that transmits a pulse signal to a piezoelectric element 4, which will be described later.

Reference numeral 3 denotes a human-powered pen for inputting coordinates, which includes a piezoelectric element 4 that vibrates in response to a pulse signal sent from the vibrator drive circuit 2, and a pen tip (hereinafter referred to as a horn) that expands the vibration from the piezoelectric element 4. ) 5. 6a to 6c are piezoelectric elements that receive elastic waves that propagate when a position on the propagation medium 8 (for example, glass) is specified with the manual pen 3 and convert it into an electric signal. Reference numeral 7 denotes an antireflection material for eliminating reflection of elastic waves at the ends of the propagation medium 8, and is made of, for example, silicone rubber. Reference numeral 9 denotes a reception waveform detection section that generates a signal for detecting delay time based on the electric signal generated by receiving elastic waves with the piezoelectric elements 6a to 6c. Note that details of this received waveform detection section 9 will be described later. 1° is a display drive unit that calculates the coordinate position of the contact point of the horn 5 of the input pen 3 using the arithmetic control unit 1, and receives the information to display, for example, a point at a position on the display 11, which will be described later. . Reference numeral 11 denotes a display, and by overlapping it with the propagation medium 8, it displays information manually input with the human pen 3 in real time (just like writing on paper with a writing instrument).

An outline of the processing operation of this embodiment in the configuration described above will be explained below.

First, the piezoelectric elements 6a to 6c receive elastic waves generated when the human pen 3 is pointed on the propagation medium 8, and convert them into electric signals (hereinafter referred to as detection signals) corresponding to the intensity of the elastic waves. Upon receiving this detection signal, the reception waveform detection circuit 9 generates a reception signal, and based on this signal, the calculation control unit 1 calculates the position coordinates of the contact point between the human pen 3 and the propagation medium 8,
The position coordinate data is output to the display drive circuit 10 and displayed on the display 11.

[Explanation of received waveforms (Figures 2 and 3)] At this time, the electric pulse signal generated from the vibrator drive circuit 2 and the piezoelectric element 6a for the sensor (the same is true for the other piezoelectric elements 6a and 6b) Therefore, the detected waveform converted by the piezoelectric element 6a (hereinafter, only the piezoelectric element 6a will be explained) is shown in FIG.

In the figure, 12 is a signal output from the vibrator drive circuit 2 to the piezoelectric element 4 in the input pen 3, and is driven by several pulses. Note that the pulse width is set in accordance with the resonant frequency of the vibrator. In response to this, the piezoelectric element 4 vibrates, and the vibration is amplified via the horn 5, and urges the propagation medium 8 to propagate as an elastic wave. The propagation delay time at this time is detected. Incidentally, in this embodiment, a plate wave is used as the elastic wave at this time. The use of plate waves is such that even if there is a scratch on the propagation medium 8 or an object (such as a hand) is placed on it, there is almost no effect, and the piezoelectric element 6a for the sensor This is because waves can be detected.

Further, in FIG. 2, 14 is a detection signal detected by the sensor piezoelectric element 6a, and the broken line portion 13 is an envelope of the detection signal 14. The waveform of the detection signal 14 based on this plate wave does not always have a constant shape because the group velocity and phase velocity are different due to dispersion. This is because the overall shape of the envelope 13 of the detection signal 14 differs in propagation velocity (group velocity) and propagation velocity (phase velocity) for the frequency corresponding to the signal 12 that drives the piezoelectric element 4. This is because the phase of the detection signal 14 differs from the overall shape of the envelope 13 depending on the distance between the human pen 3 and the sensor piezoelectric element 6a. Therefore, when detecting the delay time, it is necessary to use a method that reduces errors caused by the difference in group velocity and phase velocity.

Here, the method for detecting the propagation delay time will be described in detail.

As mentioned above, detection is performed by determining which part of the group of detection waves (pulses) of the detection signal 14 is detected to determine the propagation delay time from the position of the input pen 3 to the sensor piezoelectric elements 6a to 6C. The error with respect to the delay time is ±1/2 wavelength.

As an example of this, FIG. 3 shows a case where a certain threshold level is set for the detection signal 14 and a received signal is generated. In the figure, 15.17 is a detection signal, during which the input ben 3 has moved a small distance. Further, 16 and 18 are received signals of a predetermined length generated by comparing the detection signals 15 and 17 at a threshold level, respectively. As mentioned above, the position (phase) of the small wave changes depending on the distance between the input vent 3 and the piezoelectric element 6a due to the influence of dispersion, so the received signal 16.18 was generated with the same threshold level. In this case, even if the moving distance between them is minute, the detection delay time may shift by about one wavelength. “X” in Figure 3
This ends up being an error (actually, the error is the value obtained by subtracting the minute movement distance from "X").

In order to eliminate this error, the delay time is detected based on the velocity of the group of detected waves (group velocity) and the velocity of the detected waves (phase velocity), and the coordinate position is determined. In this embodiment, the detection method is to obtain the envelope 13 from the detection signal 14, detect the peak of the envelope 13, and set the delay time based on the group velocity until this detection as Tg. Furthermore, since the delay time Tg corresponding to the detected group velocity is made up of a collection of waves of the detection waves, the resolution (accuracy) is lower than that of the detection waves.

However, it is possible to roughly detect distances. Therefore, this T
The purpose is to detect one zero-crossing point of the first detected wave after g is detected, and the propagation delay time required for this detection is defined as TP. By calculating the coordinate position from the propagation delay time Tg and "rp obtained using the group velocity and phase velocity, detection with high resolution (accuracy) with few errors can be performed.

[Description of the received waveform detection circuit and its operation (FIGS. 4 and 5)] FIG. 4 is a diagram showing the internal configuration of the received waveform detection circuit 9. As shown in FIG. It should be noted that what is shown here is for the sensor piezoelectric element 6a, and is exactly the same for the other piezoelectric elements 6b and 6c.

In the figure, 19 is a preamplifier circuit that amplifies the detection signal detected by the piezoelectric element 6a, 20 is an envelope detection circuit (for example, a low-pass filter) that detects an envelope from the signal amplified by the preamplifier circuit 19, and 21 is an envelope peak detection circuit (
22 is the propagation delay time Tg of the group velocity detected by the envelope peak detection circuit 21 using the group velocity.
23 is a Tg signal detection circuit (for example, a zero cross comparator) that outputs a signal representing the group velocity delay time Tg, and 23 is a gate that opens a gate for a certain time (open window <). 25 is a delay time adjustment circuit that adjusts the time lost during processing in each of the circuits (20 to 24) described above. The delay time Tp until the signal corresponding to the generated phase velocity is detected is detected by comparing the signal passed through the comparator level with the comparator level generated by the comparator level supply circuit 24.

The above processing operation will be explained using the timing chart of FIG.

In the figure, 50 is a signal output from the vibrator drive circuit 2, and 51 is a signal detected by the sensor piezoelectric element 6a and amplified by the preamplifier circuit 19. An envelope detection circuit 2 is used to generate an envelope 52 of this signal 51.
via 0. Next, the first-order differential of the envelope 52 is passed through the envelope peak detection circuit 21 to obtain a signal 53, which generates a signal 54 in which a zero-crossing point is detected. The time value until the rise of this signal 54 is detected by the Tg signal detection circuit 22 and outputted to the arithmetic control unit 1, and also outputted to the monostable multivibrator 23 for a predetermined length (for example, 1.5 times the phase velocity wavelength). A high level pulse signal 55 is generated. Next, a pulse signal 56, which is an inversion of this pulse signal 55, is generated by a comparator level supply circuit 24 and outputted to one input terminal of a Tp detection circuit 26, which is a comparator. In addition, the delay time adjustment circuit 25 outputs the signal 51 from the preamplifier circuit 19 to the input side of the Tp detection circuit 26, which is a comparator, after being delayed by the time delay (preset) in each of the circuits described above. Output on the other end. In the Tp detection circuit 26, the signal 5
6 and signal 51, signal 57 is generated. The time until this signal 57 is detected is defined as the propagation delay time Tp based on the phase velocity. Both Tg and Tp are used to perform calculations to detect the coordinate position, and an example of this method for detecting the coordinate position will be described in detail from a one-dimensional perspective.

[Explanation of distance calculation (Figures 6 and 7)] As mentioned above, the propagation delay time Tg based on the group velocity is detected from the envelope of the detected wave, so it is calculated from one of the detected waves. The accuracy is lower when compared to the detected propagation delay time.

Therefore, from the propagation delay time "rp" based on the phase velocity detected from one of the detected waves, the input pen 3 and the propagation medium 8
Calculating the distance from the point of contact with the piezoelectric element 6a for the sensor is more accurate than calculating from Tg. However, the phase of each detected wave is excited due to the influence of dispersion as described above. Therefore, the relationship between the propagation distance and the propagation time when the highest level peak pulse is detected in the detection signal 14 in FIG. 2 is as shown by 'rp in FIG. 6. That is, as the input ben 3 continuously moves away from the sensor piezoelectric element 6a, the signal in FIG. 7(a) - the signal in FIG. 7(b) - the signal in FIG. 7(C) and their peak positions change. changes. In other words, at a certain distance, the wave of pulse a was at its peak, but gradually the wave of pulse b became the peak, and furthermore, the wave of pulse C became the peak. Furthermore, if the input ben 3 is moved in the opposite direction, the movement of the peak will also be reversed. This peak movement results in a stepwise movement like Tp in FIG. Further, the zero-crossing points of the waves of the a, b, and c pulses also exhibit the same movement.

When calculating the propagation distance, the delay time is used as a factor. Therefore, as you can see from Figure 6, two distance values are obtained for Tpl propagation delay times, but if you read the value of Tp based on Tg, one propagation distance will be obtained. become. A specific example that can be calculated with a highly accurate value based on this Tp is as follows.

As mentioned above, when Tg and "rp are detected, when Tp is in the range of tpl for Tg in the range of tgl in FIG. 6, tP for Tg in the range of tg2.
When Tp is within the range of 2, one Tp can be sequentially detected, and the distance can be calculated from this.

That is, in Fig. 6, if the propagation distance is λ, one wavelength of the detected wave (phase velocity) is λ, and the phase velocity is vp, then T=vpTp+
n·λ, and a distance sentence based on this formula can be detected.

However, "n" here is when Tg is in the range of tgx, n=0tg2, tg
3 range, n=1; tg3, tg4 range, n=2. Therefore, when Tg and "rp are detected as described above, such a conversion is stored in the table in the arithmetic control unit 1, for example,
By utilizing this, Tg is converted to n in the arithmetic control unit 1, and vp, Tp are obtained.

The sentence can be calculated by substituting the values of the parameters n and λ. Detection is performed using the piezoelectric elements 6a to 6C for each sensor in a manner similar to the above example, and the x and y coordinate positions are calculated.

[Explanation of other received waveform detection circuits and their operations (Figures 8 and 9) In addition, in this embodiment, in group velocity detection, the envelope of the detected wave is differentiated once to detect the zero-crossing point. Although the delay time Tp based on the phase velocity is detected by this method, it is also possible to detect the zero-crossing point of a waveform obtained by differentiating the detected waveform twice, for example. This allows a steeper detection point to be obtained than when detecting a zero-crossing point using one-time differentiation, that is, when detecting the peak point of an envelope, and enables detection with higher accuracy than when detecting the peak of an envelope.

A specific example of this will be explained with reference to FIGS. 8 and 9.

FIG. 8 shows another embodiment showing the internal configuration of the received waveform detection circuit 9, and FIG. 9 is a timing chart at that time.

In the figure, 80 is a two-times circuit that processes the envelope detected by the envelope detection circuit 20 twice, and a fourth
Descriptions of circuits labeled with the same numbers as in the figures will be omitted.

Now, after the envelope detection circuit 20 generates the envelope 52, the circuit 80 generates the first differential waveform 90 first, and then generates the second differential waveform 91. This 2
A signal 92 is generated by the Tg signal detection circuit 22 in order to detect zero-crossing points of the waveform for the number of times. This signal is sent to the arithmetic control unit 1 and outputted to the monostable multivibrator 23 to generate a high-level pulse signal 9 of a predetermined length.
Generate 3. Next, a pulse signal 94, which is an inversion of this pulse signal 93, is generated by a comparator level supply circuit 24 and outputted to one end of the input side of a Tp detection circuit 26, which is a comparator. In addition, the delay time adjustment circuit 25 delays by the amount of time delayed in each circuit (preset).
The signal 51 from the preamplifier circuit 19 is output to the other input end of the Tp detection circuit 26, which is a comparator. Tp
The detection circuit 26 generates a signal 95 by comparing the signal 94 and the signal 51. The time until this signal 95 is detected is defined as the propagation delay time Tp based on the phase velocity. These, Tg.

The coordinate position will be detected by calculation using both Tp, but since the calculation method is the same as that described above, the explanation will be omitted.

As explained above, according to this embodiment, the resolution as a digitizer is improved by using the plate wave of the elastic wave, and calculating the coordinate position by measuring the group velocity and phase velocity due to dispersion, which are characteristics of the plate wave. (Accuracy) can be improved. Furthermore, it becomes possible to use a transparent propagation medium (glass), and it becomes possible to construct an input/output car type digitizer.

Further, by having the relationship between Tg, Tp, and l as a table (table area shown in the arithmetic control unit 1 in FIG. 1), signal processing time can be shortened and detection with high accuracy can be achieved.

Furthermore, by providing a detection window with the monostable multivibrator 23 and the comparator level supply circuit 24 in the received waveform 9, there is an effect that position coordinates can be detected with high accuracy without being affected by false detections. Furthermore, by having the delay time adjustment circuit 25, accurate Tg can be obtained from the envelope and the detected wave.
and Tp can be detected, and the position coordinates can be detected with high precision.

In addition, in this embodiment, the zero crossing point is detected when detecting the delay time Tp based on the phase velocity, but if the peak is detected, it will be affected by the pen pressure of the manual pen and the S/N of the detected wave. This is because it is possible to detect accurate Tp without being influenced by these factors, and to detect highly accurate position coordinates.

Incidentally, the delay time adjustment circuit 25 is not necessarily a necessary circuit, as it is sufficient if the calculation control unit 1 calculates a coefficient for the delay time from the beginning.

Also, have the numerical values of the relationship between Tg and Tp in a table, and use the highly accurate value of Tp again from the table to obtain the highly accurate value of T'.
Since Tg and T''g are continuous straight lines, it is also possible to directly calculate the x and y coordinate position using the value of T'g.

Hereinafter, the margins [Effects of the invention] As explained above, according to the invention, the resolution as a digitizer can be increased by measuring the group velocity and phase velocity together due to dispersion and calculating the coordinate position. Become.

[Brief explanation of the drawing]

Figure 1 is an overall configuration diagram of the coordinate input device according to this embodiment, Figure 2 is a diagram showing the digging drive waveform to the manual pen and the detection waveform of the elastic wave, and Figure 3 is a diagram showing the waveform of the digging drive to the manual pen and the detection waveform of the elastic wave. Fig. 4 is a diagram showing the internal configuration of the received waveform detection circuit in this embodiment, and Fig. 5 shows each block in Fig. 4. FIG. 6 shows propagation delay time Tg based on group velocity and propagation delay time Tp based on phase velocity. FIG. 8 shows received waveform detection in another embodiment. FIG. 9 is a diagram showing the internal configuration of the circuit. FIG. 9 is a diagram for explaining waveform estimation in each block of FIG. 8. In the figure, 1... Arithmetic control unit, 2... Vibrator drive circuit,
3... Input pen, 4... Piezoelectric element, 5... Horn, 6a-6c... Piezoelectric element for reception, 7... Anti-reflection member, 8... Propagation medium, 9... - Received waveform detection circuit, 10... Display drive circuit, 11... Display, 19... Preamplifier circuit, 20... Envelope detection circuit, 21... Envelope peak detection circuit, 22.・・・
Tg signal detection circuit, 23... monostable multivibrator, 24... comparator level supply circuit, 25...
- Delay time adjustment circuit, 26... Comparator Tp detection circuit, 80... Circuit for two times. Patent applicant: Canon Corporation; Figure 4 Figure 5 Figure 6 (a) (b) (C) Figure 8 Figure 9

Claims (5)

[Claims] (1) a position specifying means for specifying a desired position on the coordinate input board and energizing the coordinate input board to generate an elastic wave; and a position specifying means fixed at a predetermined position on the coordinate input board for receiving the elastic wave. ,
a plurality of receiving means for generating electrical signals corresponding to the intensity thereof; a first detecting means for detecting the propagation time of the group velocity of the elastic wave from the electrical signal; and a first detecting means for detecting the propagation time of the group velocity of the elastic wave from the electrical signal; a second detection means for detecting propagation time;
A coordinate input device comprising calculation means for calculating the coordinate position designated by the position designation means from the propagation time values detected by the first and second detection means. (2) The coordinate input device according to claim 1, wherein the elastic wave is a plate wave. (3) The coordinate input device according to claim 1, wherein the first detecting means detects a zero-crossing point when the envelope of the electrical signal received by the receiving means is differentiated. (4) The coordinate input device according to claim 3, wherein the number of times of differentiation is one or two. (5) The second detection means generates a signal of a predetermined length from the point detected by the first detection means, and even when a signal of a predetermined length is generated as a result of comparing the signal of the predetermined length with the electric signal received by the reception means. 2. The coordinate input device according to claim 1, wherein the coordinate input device detects the coordinates of the coordinate input device according to claim 1.