JP2612055B2 - Coordinate input device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coordinate input device, and more particularly, to a vibration input of a vibration pen by detecting vibrations input by a vibration pen with a plurality of vibration sensors provided on a transmission plate. The present invention relates to a coordinate input device that detects coordinates on a board.

[Prior Art] In this type of apparatus, an accurate distance from an input point is obtained by a relationship between a vibration transmission time based on a group velocity and a vibration transmission time based on a phase velocity. Conventionally, the vibration transmission time based on the phase velocity has been detected based on the detection timing of the vibration transmission time based on the group velocity.

[Problems to be Solved by the Invention] However, in general, when trying to capture a characteristic point of a group velocity (for example, a peak point of an envelope signal) from a detection signal, a time delay inevitably required in a method for extracting the characteristic. , And cannot be matched with the detection based on the phase velocity. Further, if a time delay occurs, it is likely to be affected by a reflected wave or the like.

On the other hand, if an appropriate delay circuit is inserted into the phase signal detection system to delay the detection of the phase signal, the circuit becomes complicated, leading to an increase in cost.

An object of the present invention is to eliminate the above-mentioned disadvantages of the prior art, and it is an object of the present invention to provide a coordinate input device capable of obtaining accurate input point coordinates with a simple configuration.

[Means for Solving the Problems] In order to achieve the above object, a coordinate input device of the present invention comprises:
A coordinate input device for detecting a vibration input from a vibration pen by a plurality of vibration sensors provided on a power transmission plate to detect coordinates of the vibration pen on the vibration transmission plate, and detecting a delay time based on a group velocity. Group delay time detecting means, different from the group delay time detecting means, phase delay time detecting means for detecting a delay time based on a phase velocity prior to detection of the delay time by the group delay time detecting means, The outline is to have a calculating means for calculating coordinates based on the detection results by the time detecting means and the phase delay time detecting means.

Also preferably, the group delay time detecting means outputs an envelope signal of the detection signal of the vibration sensor, detects a predetermined point of the output envelope signal, and sets the group delay time based on the predetermined point as a reference. Is detected.

Further preferably, the phase delay time detecting means detects a portion of the detection signal of the vibration sensor exceeding a predetermined threshold value and outputs a gate signal, and the vibration sensor detects the vibration signal during a period of the output gate signal. , The phase delay time based on the phase speed is detected with reference to the rising edge of the detection signal.

Preferably, the gate signal is an output signal of an amplifier circuit.

[Operation] In such a configuration, the group delay time detecting means detects a delay time based on the group velocity, and the phase delay time detecting means
The group delay time detecting means detects the delay time based on the phase velocity before detecting the delay time based on the group velocity. The coordinate calculating means calculates the coordinates of the vibrating pen based on the detection results by the group delay time detecting means and the phase delay time detecting means.

[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 diagram of the coordinate input device of the embodiment. In the figure, reference numeral 3 denotes a vibration pen, which is used by a user to carry out coordinate input at a position on the vibration transmission plate 8. That is, the vibrating pen 3 has a vibrator 4 made of a piezoelectric element or the like inside, and transmits the ultrasonic vibration generated by the vibrator 4 to the vibration transmitting plate 8 via the horn portion 5 having a sharp tip. I do. Reference numeral 2 denotes a vibrator driving circuit, which drives the vibrator 4 in a pulsed manner. Reference numeral 8 denotes a vibration transmission plate, which is made of, for example, an acrylic plate, a glass plate, or the like. The vibration transmission plate 8 transmits the ultrasonic vibration received from the vibration pen 3 to the vibration sensors 6a to 6c including the piezoelectric elements provided at the corners. Reference numeral 7 denotes an anti-reflection material, which is made of, for example, silicon rubber. The anti-reflection member 7 supports the vibration transmitting plate 8 and also prevents the ultrasonic vibration transmitted through the vibration transmitting plate 8 from being reflected at the peripheral portion thereof and returning to the central portion. 9 is a signal waveform detection circuit,
A corresponding detection timing signal is output according to the detection signal of the ultrasonic vibration detected by each of the vibration sensors 6a to 6c. 1
Is an operation / control circuit which performs main control of the apparatus and operation of input coordinates. That is, while transmitting the ultrasonic pulse signal to the vibrator drive circuit 2, the internal timer is started, and based on each detection timing signal input from the signal waveform detection circuit 9, the respective vibration sensors are transmitted from the time when the pulse signal is transmitted. Detects the vibration transmission time until vibration is transmitted to 6a to 6c,
The input coordinates (x, y) of the vibration pen 3 on the vibration transmission plate 8 are obtained based on the detected vibration transmission time information.

The input coordinates (x, y) thus obtained are further variously used by the arithmetic and control circuit 1. That is, the arithmetic and control circuit 1 variously controls the output operation of the display 11 'via the display drive circuit 10 based on the obtained input coordinates (x, y).

Therefore, the vibration transmitting plate 8 is preferably superimposed on a dot display 11 'such as a CRT or a liquid crystal display, and performs dot display at a position traced by the vibrating pen 3, for example. That is, a dot is displayed at a position on the display 11 'corresponding to the position of the vibrating pen 3, and when the vibrating pen 3 is moved, an image composed of elements such as points and lines is written as if written on paper. Appears following the trajectory of the vibration pen 3. Alternatively, an input method may be used in which a menu is displayed on the display 11 ', and the menu item is selected by the vibration pen 3, or a prompt is displayed to bring the vibration pen 3 into contact with a predetermined position.

FIG. 2 is a view showing the structure of the vibration pen 3 of the embodiment.
The same components as those in FIG. 1 are denoted by the same reference numerals. In the figure, a low level (for example, 5 V
) Is transmitted. Vibrator drive circuit 2
Is a circuit that can drive the output with low impedance.
A low level input pulse signal is amplified with a predetermined gain and applied to the vibrator 4. The vibrator 4 converts the electric drive signal into mechanical ultrasonic vibration, and the ultrasonic vibration is transmitted to the vibration transmission plate 8 via the horn 5. The vibration frequency of the vibrator 4 is selected within a range in which a plate wave can be generated on a vibration transmission plate made of an acrylic plate, a glass plate, or the like. When the vibrator 4 is driven, a vibration mode in which the vibrator 4 vibrates mainly in a direction perpendicular to the surface of the vibration transmission plate 8 is selected. Further, 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 wave transmitted to the vibration transmission plate 8 is a plate wave, there is an advantage that the surface of the transmission transmission plate 8 is less susceptible to scratches, obstacles, and the like than surface acoustic waves.

FIG. 3 is a block diagram of the arithmetic and control circuit 1 of the embodiment. In the figure, reference numeral 11 denotes a micro computer (CP
U) to perform various calculations and controls. 11a is a ROM storing a program to be executed by the CPU 11, and 11b is a RAM used by the CPU 11 as a work area. 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 a start signal from the CPU 11. Further, the start signal from the CPU 11 causes the timer counter 13 to start the counting operation.

On the other hand, the signal waveform detection circuit 9 outputs various detection timing signals (timing pulse signals) for measuring the vibration transmission time by catching the detection outputs of the vibration sensors 6a to 6c. These signals are, for example, the detection timing signals t _{g1 to} t _{gh of} envelope signals and the detection timing signals t _{p1 to} t _ph of phase signals, which will be described later, assuming that the number of vibration sensors 6 is generalized to h. These detection timing signals are input to the detection signal input port 15 in parallel. A latch circuit 14 latches the contents (vibration transmission time) of the counter 13 in accordance with the input of each detection timing signal, and stores the contents in a storage area corresponding to each of the vibration sensors 6a to 6c. Reference numeral 16 denotes a determination circuit which determines whether or not a detection timing signal has been input from all the vibration sensors.
Notify 1 Thereby, the CPU 11 calculates the coordinates (x, y) where the vibration pen 3 is placed based on the total vibration transmission time for each of the vibration sensors 6a to 6c. Reference numeral 17 denotes an I / O port. Control of, for example, the display 11 ′, which is an external circuit, is performed on the I / O port 1.
Done through 7. Note that if there is no notification signal from the determination circuit 16 even after the maximum time determined by the circuit delay time, the maximum transmission delay time, and the like of the embodiment, the CPU 11 outputs the reset signal without performing the operation and performs the above operation. repeat.

FIG. 4 is a timing chart for explaining the mode of vibration transmission of 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 several pulses. Accordingly, the vibrator 4 is ultrasonically vibrated, and the ultrasonic vibration is transmitted to the vibration transmission plate 8 via the horn 5. Further, the ultrasonic vibration is transmitted through the vibration transmission plate 8 and detected by the respective 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 the vibration transmission. The plate wave of the embodiment is a dispersive wave,
The relative relationship between the envelope signal 421 extracted from the detected waveform and the phase signal (detected waveform) 422 changes according to the transmission distance of the vibration. Now, the group velocity and the speed of travel of the envelope signal 421 V _g, when the speed of travel of the phase signal 422 and the phase velocity V _p, the distance between the vibration sensors 6a~6c the vibration pen 3 is the group velocity
V _g , based on the phase velocity V _p .

First, attention is paid only to the envelope signal 421. Group velocity V _g
Is detected by detecting arrival of a certain characteristic point on the envelope signal 421, for example, a peak point. In this case, the detection of the characteristic point is delayed by at least one wavelength of the phase signal 422 from the viewpoint of detecting the peak point of the envelope signal 421. Signal 43 is a detection timing signal of the peak point, time t _g to peak point detection from the time of occurrence of the pulse signal 41 is a vibration transmission time of actual measurement. Also since the group velocity V _g is known, the distance d between the vibration sensors 6a~6c the vibration pen 3 is obtained by (1).

d = V _g · t _g (1) Further, when the position detection accuracy (tablet resolution) of the vibration pen 3 is increased, 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 point of occurrence of the pulse signal 41 to the first rising zero-crossing point (signal 44) after the peak detection for the envelope signal 421 is _defined as: Detect
The distance between the signal pen 3 and each of the vibration sensors 6a to 6c can be obtained by equation (2).

d = n · λ _p + V _p · t _p (2) where λ _p : wavelength of elastic wave n: integer The integer n is obtained by the formula (3) from the formulas (1) and (2).

Here, the symbol [] is a Gaussian symbol. N is a real number other than "0", and an appropriate numerical value is used. For example, N
If n = 2, n can be determined if the envelope detection accuracy is within ± 1/2 wavelength. Thus, the accurate distance d is obtained by substituting n obtained by Expression (3) into Expression (2).

However, as described above, the peak detection of the envelope signal 421 requires at least the delay time t of at least one wavelength of the phase signal 422.
_{Since e} is included, the envelope signal is delayed substantially like 421 ', and it is not preferable to use this as a reference for phase signal detection. Therefore, a method for detecting the phase signal is devised.

FIG. 5 is a block diagram of the signal waveform detection circuit of the embodiment. In the figure, reference numeral 51 denotes a preamplifier circuit, which amplifies an output signal of the vibration sensor 6 to a predetermined level. Reference numeral 52 denotes an envelope detection circuit, which extracts an envelope signal from the amplified signal. An envelope peak detection circuit 53 detects a peak of the envelope signal and triggers the _tg signal detection circuit 54 at the detection timing. The t _g signal detection circuit 54 is constituted by, for example, a monomultivibrator circuit. Arithmetic and control circuit 1 to obtain a t _g detection pulse vibration transmission time t _g by the speed V _g groups based on the output signal 43 counter 13 at the timing that has received the.

On the other hand, 55 is a signal detection circuit, which is a predetermined-level threshold signal of the signals amplified by the preamplifier circuit 51.
A pulse signal 47 of a portion exceeding 46 is formed. Reference numeral 56 denotes a monostable multivibrator, which opens a gate signal 48 having a predetermined time width triggered by the rise of the first pulse signal 47.
_Reference numeral 57 denotes a t _g comparator, which detects the first rising zero-cross point of the detection signal 42 while the gate signal 48 is open, and outputs a detection signal 49 at time t _p ′. The time t _p 'are those detected independently of the detection of the envelope signal. Arithmetic and control circuit 1 obtains a transmission time t _p 'by phase velocity V _p on the basis of 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 of the systems of the vibration sensors 6a to 6c, and an accurate distance from the coordinate input point to each of the vibration sensors 6a to 6c is obtained.

By the way, in such a method, it is necessary to consider the level change of the detection signal 422 due to the writing pressure by the vibrating pen 3, the vibration transmission distance, and the like. 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 position where the first detection pulse signal 47 is generated also changes. For example, the detection signal 49 of the detection if you missed the time t _p 'of signal 42a is delayed one wavelength. However, this delay always occurs at an integer multiple of one wavelength. Therefore, the arithmetic and control unit 1 corrects this delay. For example, detection signal 43 at time t _g
When the detection signal 49 of t _p ′ is detected within two wavelengths, the detection signal 49 of the time t _p ′ is used as it is.
However, when there is a shift of two or more wavelengths, the detection signal 43 at time t _g
Is corrected so that the time is within two wavelengths. That is, correction is performed so that a value obtained by adding an integer multiple of the wavelength to the actually detected time t _p ′ is included in the time within the two wavelengths, and the resulting time t _p ′ is used in the calculation.

Note that the above correction is determined within two wavelengths, but may be one wavelength or three wavelengths.

The arithmetic and control unit 1 detects each of the detection timing signals t _{g1 to} t _gh and
The contents of the counter 13 are taken into the latch circuit 14 in accordance with t _{p1 to} t _ph . The CPU 11 calculates (2) and (3) based on these values.
A slave connexion vibration pen 3 in the formula determining the distance d ₁ to d _h between the vibration sensors. The number of vibration sensors is arbitrary as long as it is two or more.

FIG. 6 is a diagram for explaining the coordinate table calculation processing of the embodiment.
In the figure, three vibration sensors are provided at the corners of the vibration transmission plate 8.
6a to 6c are provided, and the coordinates of each vibration sensor are 6a = S ₁
(0, 0), 6b = S ₃ (0, Y), and 6c = S ₂ (X, 0). Then, according to the three-square theorem, the coordinates (x, y) of the input point P can be obtained by the equations (4) and (5).

By repeating the above operation, input coordinates can be detected in real time.

In the above-described embodiment, the time _tg is detected at the peak point of the envelope signal. However, the present invention is not limited to this. Alternatively, for example, the envelope signal may be differentiated twice to detect a zero cross point (an inflection point of the envelope signal) of the twice differentiated waveform.
Thus the signal detection time t _g is less likely affected by reflected waves.

[Effects of the Invention] As described above, according to the present invention, prior to the detection of the delay time based on the group velocity, the delay time based on the phase velocity is detected by the phase delay time detection means different from the group delay time detection means. Therefore, there is no dependency of the phase delay time on the group delay time, and highly reliable measurement can be performed. In addition, since the detection point of the phase delay time becomes earlier, it is hard to be affected by the reflected wave, and highly accurate measurement can be performed. Furthermore, since it is hard to be affected by the reflected wave, a compact coordinate input device can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram of the coordinate input device of the embodiment, FIG. 2 is a diagram showing the structure of the vibration pen 3 of the embodiment, FIG. 3 is a block diagram of the arithmetic and control circuit 1 of the embodiment, FIG. FIG. 5 is a timing chart for explaining the mode of vibration transmission of the embodiment, FIG. 5 is a block diagram of a signal waveform detection circuit of the embodiment, and FIG. 6 is a diagram for explaining coordinate calculation processing of the embodiment. In the figure, 1 ... calculation / control circuit, 3 ... vibration pen, 4 ...
Vibrator, 6a to 6c: Vibration sensor, 8: Vibration transmission plate, 11
... CPU, 11a ... ROM, 11b ... RAM, 11 '... Display.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Ryozo Yanagisawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Shinnosuke Taniishi 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Yuichiro Yoshimura 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) References JP-A-63-6618 (JP, A)

Claims (4)

(57) [Claims] 1. A coordinate input device for detecting a vibration input from a vibration pen by a plurality of vibration sensors provided on a power transmission plate to detect coordinates of the vibration pen on the vibration transmission plate, based on a group velocity. Group delay time detecting means for detecting a delay time, and, unlike the group delay time detecting means, a phase delay time detecting means for detecting a delay time based on a phase speed prior to detection of the delay time by the group delay time detecting means And a calculating means for calculating coordinates based on detection results by the group delay time detecting means and the phase delay time detecting means. 2. The group delay time detecting means outputs an envelope signal of a detection signal of the vibration sensor, detects a predetermined point of the output envelope signal, and sets a group delay based on the predetermined point as a reference. The coordinate input device according to claim 1, wherein time is detected. 3. The phase delay time detecting means detects a portion of a detection signal of the vibration sensor exceeding a predetermined threshold and outputs a gate signal, and outputs the gate signal during the output gate signal period. 2. The coordinate input device according to claim 1, wherein a phase delay time based on a phase speed is detected based on a rise of a detection signal of the sensor. 4. The coordinate input device according to claim 3, wherein said gate signal is an output signal of an amplifier circuit.