JPH02130612A - Coordinate input device - Google Patents

Abstract

PURPOSE:To input coordinates highly accurately by detecting oscillation, which is inputted by an oscillating pen, by plural sensors to be provided in an oscillation transmitting board and obtaining a coordinate input point based on first and second oscillation transmitting times. CONSTITUTION:A user has an oscillating pen 3 by a hand and inputs the coordinates in a position on an oscillation transmitting board 8. The oscillation transmitting board 8 transmits the ultrasonic oscillation, which is received from the oscillating pen 3, to oscillation sensors 6a-6c. Signals to be detected by the sensors 6a-6c are respectively given to a signal waveform detecting circuit 9 and the detecting circuit 9 obtains the oscillation transmitting speed with a group velocity based on the envelope signal of the respective detecting signals and obtains the transmitting time with a phase velocity based on the detecting signal. An arithmetic control circuit 1 can obtain an exact distance from the coordinate input point to the respective sensors 6a-6c based on the both transmitting times.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a coordinate input device, and more particularly, the present invention relates to a coordinate input device, and in particular, detects vibrations input by a vibrating pen using a plurality of vibration sensors provided on a vibration transmitting plate, and transmits the vibrations of the vibrating pen. The present invention relates to a coordinate input device that detects coordinates on a board.

[Prior Art] In this type of device, an accurate distance from an input point is determined based on the relationship between the vibration transmission time based on the group velocity and the vibration transmission time based on the phase velocity. Conventionally, the vibration propagation time was detected using the phase velocity based on the detection timing of the vibration propagation time based on the group velocity.

[Problem to be solved by the invention] However, in general, when trying to capture the characteristic point of group velocity (for example, the peak point of an envelope signal) from the detection signal, in reality, there is a time delay that is inevitable due to the method for extracting the characteristic. This results in inconsistency with detection based on phase velocity, and when a time delay occurs, it becomes susceptible to the effects of reflected waves, etc.

On the other hand, if an attempt is made to delay the detection of the phase signal by inserting an appropriate delay circuit into the phase signal detection system, the circuit becomes complicated and costs increase.

The present invention is intended to eliminate the above-mentioned drawbacks of the prior art, and its purpose is to provide a coordinate input device that can obtain accurate input point coordinates with a simple configuration.

[Means for Solving the Problem] In order to achieve the above object, the coordinate input device of the present invention has the following features:
In a coordinate input device that detects vibrations input by a vibrating pen using a plurality of vibration sensors provided on a vibration transmitting plate to detect the coordinates of the vibrating pen on the vibration transmitting plate, a first measuring means for measuring a first vibration transmission time, a second measuring means for measuring a second vibration transmission time based on the detected signal, and the measured first and second vibration transmission times. The outline of the system is to include a calculation means for determining the coordinate input point of the vibrating pen based on the following.

Preferably, a correction means is provided for correcting the second vibration transmission time by adding an integral multiple of the wavelength when the second vibration transmission time is not within a predetermined range based on the first vibration transmission time. The outline is as follows.

[Operation] In this configuration, the first measuring means measures the first vibration transmission time based on the envelope signal of the detected signal. The second measuring means independently measures the second vibration transmission time based on the detected signal itself. The calculation means determines the coordinate input point of the vibrating pen based on the measured first and second vibration transmission times.

Preferably, a correction means is provided, and the correction means adds an integral multiple of the wavelength to the second vibration transmission time when the second vibration transmission time is not within a predetermined range based on the first vibration transmission time. Correct it.

[Description of Embodiments] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a block configuration diagram of the coordinate input device of the embodiment. In FIG. The vibrating pen 3 has a vibrator 4 made of a piezoelectric element or the like inside, and transmits ultrasonic vibrations generated by the vibrator 4 to a vibration transmission plate 8 via a horn portion 5 with a sharp tip. Reference numeral 2 denotes a vibrator drive circuit, which drives the vibrator 4 in pulses. A vibration transmission plate 8 is made of, for example, an acrylic plate or a glass plate. The vibration transmitting plate 8 transmits the ultrasonic vibration received from the vibrating ben 3 to vibration sensors 6a to 6c made of piezoelectric elements or the like provided at its corners. 7 is an anti-reflection material;
For example, it is made of silicone rubber. The anti-reflection material 7 supports the vibration transmission plate 8 and prevents the ultrasonic vibrations propagated through the vibration transmission plate 8 from being reflected at its periphery and returning toward the center. Reference numeral 9 denotes a signal waveform detection circuit, which outputs a detection timing signal corresponding to the detection signal of ultrasonic vibration detected by each of the vibration sensors 6a to 6c. 1 is an arithmetic/control circuit that performs main control of the device and calculates input coordinates.

That is, an ultrasonic pulse signal is sent to the vibrator drive circuit 2, an internal timer is started, and the vibration sensors are activated from the time when the pulse signal is sent based on each detection timing signal inputted from the signal waveform detection circuit 9. 6a-6c
The vibration transmission plate 8 of the vibration vent 3 is detected based on the detected vibration transmission time information.
Find the input coordinates (x, y) above.

The input coordinates (x, y) obtained in this way are further used in various ways by the calculation/control circuit 1.

That is, the calculation/control circuit 1 calculates the input coordinate (x.

y), the output operation of the display 11' is variously controlled via the display drive circuit 10.

For this reason, the vibration transmission plate 8 is preferably placed on a display device 11' capable of displaying dots, such as a CRT or a liquid crystal display.
For example, a dot is displayed at the position traced by the vibrating ben 3, that is, the display 11' corresponds to the position of the vibrating ben 3.
A dot is displayed at the top position, and when the vibrating ben 3 is moved, an image composed of elements such as dots and lines appears along the trajectory of the vibrating ben 3, as if written on paper. Alternatively, an input method may be used in which a menu is displayed on the display 11' and the menu item is selected using the vibrating ben 3, or a prompt is displayed and the vibrating ben 3 is brought into contact with a predetermined position.

FIG. 2 is a diagram showing the structure of the vibrating vent 3 of the embodiment. Note that in FIG. 0, the same components as in FIG. The vibrator drive circuit 2 is a circuit capable of driving an output with low impedance, and amplifies a low-level input pulse signal with a predetermined gain and applies it to the vibrator 4. The vibrator 4 converts the electrical drive signal into mechanical ultrasonic vibration, and the ultrasonic vibration is transmitted to the vibration transmission plate 8 via the horn portion 5. The vibration frequency of the vibrator 4 is selected within a range that can generate plate waves on the vibration transmission plate 8 made of an acrylic plate, a glass plate, or the like. Further, when driving the vibrator 4, a vibration mode in which the vibrator 4 mainly vibrates in a direction perpendicular to the surface of the vibration transmission plate 8 is selected. Furthermore, by setting the vibration frequency of the vibrator 4 to the resonance frequency of the vibrator 4, efficient vibration conversion is possible. Since the elastic waves thus transmitted to the vibration transmission plate 8 are plate waves, they have the advantage that they are less susceptible to the effects of scratches, obstacles, etc. on the surface of the vibration transmission plate 8, compared to surface waves.

FIG. 3 is a block configuration diagram of the arithmetic/control circuit 1 of the embodiment. In FIG. 0, 11 is a microcomputer (CP
U) and performs various calculations and controls. lla is cp
ROM that stores programs executed by UII, l
lb is the RAM used by CPU II as a work area
It is.

Reference numeral 12 denotes a drive signal generation circuit, which outputs a drive pulse signal of a predetermined frequency to the vibrator drive circuit 2 in synchronization with the start signal from the CPU II. Let it start.

On the other hand, the signal waveform detection circuit 9 catches the detection outputs of the vibration sensors 6a to 6c and outputs various detection timing signals (timing pulse signals) for measuring vibration transmission time. For example, if the number of vibration sensors 6 is generalized to six, these signals refer to envelope signal detection timing signals t□ to t, h and phase signal detection timing signals t□ to tph, which will be described later. These detection timing signals are input to the detection signal input port 15 in parallel. A latch circuit 14 latches the contents of the counter 13 (vibration transmission time) in response to the input of each detection timing signal, and stores it in a storage area corresponding to each vibration sensor 6a to 6c. Reference numeral 16 denotes a determination circuit that determines whether or not a detection timing signal from all vibration sensors has been input, and when input, notifies the CPU II of this fact. As a result, the CPU 11 calculates the coordinates (x, y) where the vibration bench 3 is placed based on the total vibration transmission time for each vibration sensor 6a to 6c. The control of the device 11' is by this I10 boat 1.
7. Incidentally, when there is no notification signal from the determination circuit 16 even after the maximum time determined by the circuit delay time, maximum transmission delay time, etc. of the embodiment, the CPU 11 outputs a reset signal without performing any calculation and performs the above operation. repeat.

FIG. 4 is a timing chart illustrating the mode of vibration transmission in the embodiment. In the figure, a signal 41 is an ultrasonic pulse signal generated by the drive signal generation circuit 12, and is composed of sporadic pulses. According to this, the vibrator 4 vibrates ultrasonically,
The ultrasonic vibrations are transmitted to the vibration transmission plate 8 via the horn section 5.

Further, this ultrasonic vibration is transmitted through the vibration transmission plate 8 and detected by each of the vibration sensors 6a to 6C. The signal 42 is a signal waveform detected by the vibration sensor 6, and is delayed by an amount corresponding to the distance of vibration transmission. The plate wave of the embodiment is a dispersive wave, and the relative relationship between the envelope signal 421 extracted from the detected waveform and the phase signal (detected waveform) 422 changes depending on the vibration transmission distance. Now, assuming that the speed at which the envelope signal 421 advances is group velocity V6, and the speed at which the phase signal 422 advances is designated as phase velocity V, the vibration ben 3 and each of the vibration sensors 6a to 6c
The distance between them is determined based on the group velocity v, phase velocity Vp.

First, we will focus only on the envelope signal 421.

Detection of propagation due to group velocity V is performed using envelope signal 421
This is done by detecting the arrival of a certain feature point, for example, the peak point, above.Due to the method of detecting the peak point of the envelope signal 421, the detection of the feature point is delayed by at least one wavelength of the phase signal 422. Become. signal 4
3 is a peak point detection timing signal, and the time t from the time when the pulse signal 41 is generated until the peak point is detected is the actually measured vibration transmission time. Also, since the group velocity V is known, the distance d between the vibration pen 3 and each vibration sensor 6a to 60 is (
1) Determined by formula.

d=V,・tl...(1) Also,
When increasing the position detection accuracy (tablet resolution) of the vibrating pen 3, processing based on the detection of the phase signal 422 is added.

- As an example, the time tp (signal 45) from a certain point on the phase signal 422, that is, the time of generation of the pulse signal 41 to the zero-crossing point (signal 44) of the first rising edge after the detection of the peak of the envelope signal 421; By detecting this, the distance between the vibrating pen 3 and each of the vibration sensors 6a to 60 can be determined using equation (2).

d=n·λp +V, I t111++ (2) Here, λ: wavelength of elastic wave n: integer Integer n can be found from equations (1) and (2) to equation (3).

... (3) Here, the symbol [] is a Gauss symbol.

Further, N is a real number other than "0", and an appropriate value is used. For example, if N=2, n can be determined if the envelope detection accuracy is within 1% wavelength. In this way (3)
Substitute n obtained by the formula into formula (2) to find the accurate distance d.

However, as mentioned above, since the peak detection of the envelope signal 421 includes a delay time t of at least one wavelength of the phase signal 422, the envelope signal is actually delayed as 421', and this is reflected in the phase signal detection. It is not recommended to use it as a standard. Therefore, we devised a method for detecting the phase signal.

FIG. 5 is a block diagram of the signal waveform detection circuit according to the embodiment. In the figure, 51 is a preamplifier circuit that amplifies the output signal of the vibration sensor 6 to a predetermined level. 52 is an envelope detection circuit that extracts an envelope signal from the amplified signal. 53 is an envelope peak detection circuit which detects the peak of the envelope signal and triggers the signal detection circuit 54 at the detection timing. t. The signal detection circuit 54 is composed of, for example, a mono multivibrator circuit. The arithmetic/control circuit 1 counter 13 at the timing when the detection pulse signal 43 is received at t.
Based on the output of , the vibration transmission time t due to the group velocity V is obtained.

On the other hand, 55 is a signal detection circuit which forms a pulse signal 47 for a portion of the signal amplified by the preamplifier circuit 51 that exceeds a threshold signal 46 of a predetermined level. 56
is a monostable multivibrator, which opens a gate signal 48 of a predetermined time width triggered by the rise of the first pulse signal 47. A comparator 57 detects the zero-crossing point of the first rising edge of the detection signal 42 while the gate signal 48 is open, and outputs a detection signal 49 at time t,'. This time tP' is detected independently of the detection of the envelope signal. The arithmetic/control circuit 1 determines the transmission time 1p based on the phase velocity vp based on the output of the counter 13 at the timing of generation of the first detection pulse signal 49. The configuration of such a waveform detection circuit is provided for each system of vibration sensors 6a to 6c, so that accurate distances from the coordinate input point to each vibration sensor 6a to 6C can be determined.

By the way, in this method, changes in the level of the detection signal 422 due to the pen pressure caused by the vibrating pen 3, the vibration transmission distance, etc. must also be taken into account. That is, since the level of the threshold signal 46 is fixed as described above, when the level of the detection signal 422 changes, the generation position of the first detection pulse signal 47 also changes. For example, if the detection of the signal 42a is missed, the detection signal 49 at time t,' will be delayed by one wavelength. However, this delay always occurs in integer multiples of one wavelength. Therefore, the calculation/control unit 1 corrects this delay. For example, time t
When the detection signal 49 at time t,' is detected within two wavelengths from the detection signal 43 at time t,', the detection signal 49 at time t,' is used as is. However, if there is a shift of two wavelengths or more, the detection signal 43 at time t8 is corrected so that the time is within two wavelengths. That is, the actual detected time t
The value obtained by adding an integral multiple of the wavelength to p' is corrected so that it is included in the time within the two wavelengths, and the resulting time t,' is used for calculation.

Note that the above correction was determined within 2 wavelengths, but 1 wavelength or 3 wavelengths
It may also be a wavelength.

The calculation/control unit l receives each detection timing signal t□ to tfh and 1. The contents of the counter 13 are taken into the latch circuit 14 according to +~t, h, and the CPU 1 uses these values to calculate the distances d, ~dh between the vibration vent 3 and each vibration sensor according to equations (2) and (3). demand. Note that the number of vibration sensors is arbitrary as long as it is two or more.

FIG. 6 is a diagram illustrating the coordinate calculation process of the embodiment. In the figure, three vibration sensors 6 are installed at the corners of the vibration transmission plate 8.
a to 6c are provided, and the coordinates of each vibration sensor are 6a
=S, (0,0)6b=Sa (0,Y), 6C=
32 (X, O). According to the 3-square theorem, the coordinates (x, y) of the input point P can be found using equations (4) and (5).

2 2X... (4) 2 2Y... (5) By repeating the above operations, input coordinates can be detected in real time.

In the above embodiment, the time t is detected at the peak point of the envelope signal, but the detection is not limited to this.

Alternatively, for example, the envelope signal may be differentiated twice and the zero-crossing point (point of inflection of the envelope signal) of the twice-differentiated waveform may be detected. This makes signal detection at time 1g less susceptible to the influence of reflected waves.

[Effect of the invention] As described above, according to the present invention, the first measuring means and the second measuring means
Since the measurement means are independent, highly reliable measurements can be performed. It can also be made less susceptible to the effects of reflected waves. Please provide a more compact and highly accurate coordinate input device.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the coordinate input device of the embodiment, FIG. 2 is a diagram showing the structure of the vibrating ben 3 of the embodiment, FIG. 3 is a block diagram of the arithmetic/control circuit 1 of the embodiment, and FIG. 5 is a block diagram of the signal waveform detection circuit of the embodiment. FIG. 6 is a diagram illustrating the coordinate calculation process of the embodiment. In the figure, 1... calculation/control circuit, 3... vibrating pen, 4
... Vibrator, 6a-6c... Vibration sensor, 8...
Vibration transmission plate, 11-CPU, 11 a=ROM,
1 lb...RAM, 11'...Display. Figure 4 Figure 5

Claims (2)

[Claims] (1) In a coordinate input device that detects vibration input by a vibrating pen using a plurality of vibration sensors provided on a vibration transmission plate and detects the coordinates of the vibration pen on the vibration transmission plate, an envelope signal of the detected signal is used. a first measuring means for measuring a first vibration transmission time based on the detected signal; a second measuring means for measuring a second vibration transmission time based on the detected signal; and a second measuring means for measuring a second vibration transmission time based on the detected signal; A coordinate input device comprising a calculation means for determining a coordinate input point of a vibrating pen based on vibration transmission time. (2) A correction means for correcting the second vibration transmission time by adding an integral multiple of the wavelength when the second vibration transmission time is not within a predetermined range based on the first vibration transmission time. A coordinate input device according to claim 1.