JPS636620A - Coordinate input device - Google Patents

Abstract

PURPOSE:To improve the resolution of a coordinate input device by controlling the loss time component when the elastic waves are received and converted into the signals that can be detected. CONSTITUTION:This coordinate device consists of an arithmetic control part 1, an input pen 3, a vibrator drive circuit 2 of piezoelectric element 4, a transmission medium 8 of glass, etc., a received waveform detecting part 9, a drive part 10 of a display 11, etc. When a position is indicated by the pen 3 on the medium 8, the elastic waves are received by piezoelectric elements 6a-6c. The part 1 calculates the position coordinates of elements 6a-6c and displays them on the display 11. Here a time control means is added to calculate the coordinate positions from the arrival signals of the group velocity and the phase velocity of a group of the detection waves produced with control. Thus the loss time needed for conversion of the electric signals into a single pulse signal is taken into consideration. Then the position coordinates can be calculated with high accuracy.

Description

[Detailed description of the invention] [Industrial field of application] The invention relates to a coordinate detection device using elastic waves, and particularly 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.

Furthermore, the propagating elasticity is detected and converted into an electrical signal, and the propagation time is detected by generating one pulse signal to detect that signal, so the electrical signal is converted into one pulse signal. This propagation time also includes the lost time required to do so, making it impossible to accurately calculate the position coordinates of the vibrating pen.

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 panel and energizing the coordinate input panel to generate an elastic wave;
a plurality of receiving means fixed at predetermined positions on the coordinate manual board for receiving the elastic waves and generating electric signals corresponding to the intensity thereof; and a plurality of receiving means for generating an arrival signal of the group velocity of the elastic waves from the electric signals. a first signal generating means; a second signal generating means for generating an arrival signal of the phase velocity of the elastic wave from the electric signal; and time adjustment means for adjusting the delay time.

[Operation] In the configuration of the present invention, the coordinate position specified by the position specifying means is calculated from the arrival signal of the group velocity and phase velocity generated by adjustment by the time adjustment 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 an input ben for inputting coordinates, and inside it there is a piezoelectric element 4 that vibrates with 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 a propagation medium 8 (for example, glass) is specified by the input ben 3 and convert it into an electric signal. Reference numeral 7 denotes an anti-reflection material for eliminating reflection at the end of the first medium 8 for transmission of elastic waves, 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. Reference numeral 10 calculates the coordinate position of the contact point of the horn 5 of the input ben 3 using the arithmetic control unit 1, and receives the information to display a display 11, which will be described later.
This is a display driving unit for displaying, for example, a dot at the upper position. Reference numeral 11 denotes a display, and by overlapping it with the propagation medium 8, it displays the information inputted by the manual 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 input ben 3 is directed over the propagation medium 8, and convert them into electric signals (hereinafter referred to as detection signals) corresponding to the intensity thereof. 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 positional coordinates of the contact point between the human-powered bench 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 (exactly the same 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 vent 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 reason why plate waves are used is that even if there is a scratch on the propagation medium 8 or an object (such as a hand) is placed on the propagation medium 8, there is usually no L9 and the piezoelectric element 6a for 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 differ depending on the fraction. 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 and used as the propagation delay time from the position of the human 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 distance between them is very small, 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 (U velocity) and the velocity of the detected waves (phase velocity), and the coordinate position is determined. As a method for this detection, in this embodiment, the envelope 13 is obtained from the detection signal 14, the peak of this envelope 13 is used, and the delay time based on the group velocity until this detection is made is set 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 assumed to be 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 piezoelectric element 6a for the sensor, 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 (
For example, a differential circuit), 22 is a propagation delay time Tg of the group velocity detected by the envelope peak detection circuit 21 using the group velocity.
23 is a monostable multivibrator that opens a gate (opens a window) for a certain time from the signal of group velocity delay time Tg, and 24 is a multivibrator 23. 25 is a delay time adjustment circuit that adjusts the time lost during processing in each of the above-mentioned circuits (20 to 24). By comparing the passed signal with the comparator level generated by the comparator level supply circuit 24, the delay time Tp until the signal corresponding to the generated phase velocity is detected is detected.

The above processing operation will be explained using the timing chart in 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 the 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 outputs the signal 51 from the preamplifier circuit 19 to the input terminal of the RP detection circuit 26, which is a comparator, after being delayed by the time delay (preset) in each of the circuits described above. output to the other end. The Tp detection circuit 26 generates a signal 57 by comparing the signal 56 and the signal 51. The time until this signal 57 is detected is defined as the propagation delay time Tp based on the phase velocity. These T3. The coordinate position is detected by calculation using both Tp, and an example of the 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, it is better to calculate the distance from the contact point of the input pen 3 and the propagation medium 8 to the piezoelectric element 6a for the sensor from the propagation delay time Tp based on the phase velocity detected from one of the detected waves. The accuracy will be higher than that. However, the phase of each detected wave shifts due to the shadow 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, when the input bend 3 continuously moves away from the senna piezoelectric element 6a, the signal of FIG. 7(a) -
The signal in FIG. 7(b)--the signal in FIG. 7(C) and the position of its peak change. 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. Also, if the human-powered Ben 3 moves in the opposite direction, the peak movement 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 Tp are detected, when Tp is in the range of tpl for Tg in the range of tgx in FIG. 6, tP2 for Tg in the range of tg2.
When Tp is within the range of . . . , one Tp can be sequentially detected, and the distance can be calculated from this.

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

However, "n" here is when Tg is in the range of tgx, n=0tg2, tg
When in the range of 3, n=1 When in the range of tg3 and tg4, n=2 Therefore, when Tg and Tp are detected as described above, such a conversion is stored in the table in the calculation 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 the same manner as in 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 the actual side of this book, in group velocity detection, the envelope of the detected wave is divided into one plane and the zero cross point is detected. 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 multiplying the detected waveform by two planes, for example. This allows a steeper detection point to be obtained than when detecting a zero cross point for one aircraft, that is, when detecting the peak point of the envelope, and allows detection with higher accuracy than when detecting the peak of the 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 circuit for processing the envelope detected by the envelope detection circuit 20 twice for the same machine, 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 two-machine circuit 80 first generates a first differential waveform 90, and then generates a second differential waveform 91. This 2
A signal 92 is generated by the Tg signal detection circuit 22 in order to detect the zero-crossing point of the same machine waveform. This signal is sent to the arithmetic control unit l 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 (preset) delayed in each circuit.
The signal 51 from the preamplifier circuit 19 is output to the other end of the input side of the Tp detection circuit 26, which is a comparator. T.P.
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 can be performed with high precision.

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 accuracy.

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 input 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 check the table again from the highly accurate TP value.
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 present invention, by adjusting the lost time when receiving and converting elastic waves into signals that can be detected, the digitizer can be used as a digitizer. This makes it possible to increase the resolution of

[Brief explanation of the drawing]

The first factor is the overall configuration diagram of the coordinate input device according to this embodiment. Figure 2 is a diagram showing the vibration drive waveform and the detection waveform of elastic waves to the human pen. Figure 4 is a diagram illustrating the principle of error occurring when propagation delay time is detected. Figure 4 is a diagram showing the internal configuration of the received waveform detection circuit in this embodiment. Figure 5 is a diagram showing the internal configuration of the received waveform detection circuit in this embodiment. FIG. 6 shows a propagation delay time Tg based on group velocity and propagation delay time TP based on phase velocity. FIG. 8 shows a received waveform detection circuit of another embodiment. FIG. 9 is a diagram for explaining the waveform estimation in each block of FIG. 8. In the figure, 1... Arithmetic control unit, 2... Vibrator drive circuit,
3... Human pen, 4... Piezoelectric element, 5... Horn, 6a to 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 Co., Ltd., □11. - ・-1'4.1 L+ Fig. 4 No. 5121 Fig. 6 ("G) (b) (C) Fig. 8 No. 9121

Claims (4)

[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 electric signals corresponding to the intensity thereof; a first signal generating means for generating an arrival signal of the group velocity of the elastic wave from the electric signal; and a first signal generating means for generating an arrival signal of the group velocity of the elastic wave from the electric signal; a second signal generation means for generating an arrival signal; and a time adjustment means for adjusting the delay time lost until the signal is generated by the first and second signal generation means, and the time adjustment means A coordinate input device characterized in that the coordinate position specified by the position specifying means is calculated from the arrival signal of the group velocity and the phase velocity generated by adjustment. (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 signal generating means generates a signal at a zero crossing point when the envelope of the electrical signal received by the receiving means is differentiated. (4) The second signal generating means compares the signal of a predetermined length generated by the first signal generating means with the electrical signal delayed by the delay time required to generate the signal by the time adjusting means. The coordinate input device according to claim 1, wherein the coordinate input device generates a generated signal.