JPH0580920A - Coordinate input device - Google Patents

Abstract

PURPOSE:To detect accurate coordinates by correcting variation in the transmission speed of vibration propagated in a transmission body with temperature in the coordinate input device which gives the vibration to the transmission body from a vibration pen and detects the vibration by a separately installed sensor to determine the coordinates. CONSTITUTION:When the vibration pen 3 is pressed against a vibration transmission plate, the vibration is detected by the sensor 6 to determine the coordinates of the vibration pen, but the propagation delay time of the vibration in the vibration transmission body 8 and a vibration transmission path varies with the outside air temperature. For the purpose, a signal waveform detecting circuit 9 is provided with a delay circuit to compensate variation in the delay time in the vibration transmission body 8 and vibration transmission path. The delay circuit naturally varies the delay time with the temperature so as to cancel the delay in the propagation body 8. For the purpose, the delay circuit uses a capacitor and a resistor having known temperature characteristics.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coordinate input device for detecting designated point coordinates using elastic waves.

[0002]

2. Description of the Related Art Conventionally, a coordinate input device utilizing elastic waves is disclosed in Japanese Patent Application No. 61-281681 or Japanese Patent Application No. P63.
As described in -283868, in order to perform temperature compensation, a specific coordinate position is designated, and the detected coordinate is compared with the actual coordinate measured on the coordinate input plate in advance, It is configured to correct based on the difference. In general, temperature correction is performed by a method in which a temperature sensor is specially installed and the temperature is corrected based on the outside air temperature detected by the sensor.

[0003]

However, in the above-mentioned conventional example, since it is necessary for the user to perform a special operation of instructing a specific point whose coordinates are known in advance, the original instruction for correction is required. There is an unavoidable physical error such as an error between the specific pointing point that must be provided and the point actually pointed by the user. To avoid this,
In order to minimize the physical error as much as possible, the structure must be highly accurate, which leads to an increase in cost.

When a temperature sensor or the like is used,
There is a drawback in that cost is increased because components such as a temperature sensor and a sensor circuit are required.

The present invention has been made in view of the above-mentioned conventional example, and provides a coordinate input device which has a simple structure and corrects a coordinate detection deviation due to a change in the outside air temperature to improve the coordinate detection accuracy. With the goal.

[0006]

In order to achieve the above object, the coordinate input device of the present invention has the following structure. A coordinate input device for detecting the vibration of the vibration transmitting body by a vibration detecting means arranged on the vibration transmitting body to detect the coordinates of a vibration source on the vibration transmitting body. Compensation means for compensating the temperature characteristic of the vibration transmission speed in the transmission path is provided.

[0007]

With the above arrangement, the coordinate input device of the present invention corrects the change of the vibration transmission speed in the vibration transmitter and the vibration transmission path due to the outside air temperature, and detects the coordinate position without being influenced by the outside air temperature. To do.

[0008]

EXAMPLE A coordinate input device using elastic waves will be described as an example of the present invention.

<Structure> FIG. 1 is a diagram showing the basic structure of the coordinate input device of this embodiment.

Reference numeral 1 is a calculation control block for controlling each block and calculating coordinate values and the like. Reference numeral 3 denotes a vibrating pen for generating an elastic wave in a vibration transmitting body 8 that transmits the elastic wave, and includes a piezoelectric element 4 for generating vibration, a horn portion 5 and a supporter thereof. Reference numeral 2 is a drive circuit for the vibrating pen 3. Reference numeral 6 is a sensor for detecting the elastic wave transmitted through the transmission body 8, and 9 is a signal detection circuit for generating a detection signal depending on the propagation delay time from the signal obtained from the sensor 6. Reference numeral 7 denotes an antireflection material for preventing reflection at the end of the transmitter 8. Reference numeral 11 is a display for displaying points input by the vibrating pen 3, and 10 is a drive circuit thereof.

The operation of each block will be described below in sequence.

FIG. 2 is a block diagram of the configuration of the arithmetic control unit 1.

Reference numeral 1-1 is a microcomputer, which has an internal counter, ROM and RAM. In this configuration, first, the reset signal is sent to the counter 1-3 for measuring delay time and the detection signal input port 1-5, and is cleared to enter the state of waiting for input.

Next, a start signal is sent from the microcomputer 1-1 to the drive signal generating circuit 1-2 and the counter 1-3. In response to this start signal, the drive signal generation circuits 1-2 generate a pulse train having a repeating cycle of the resonance frequency of the in-pen oscillator 3, and output it to the oscillator drive circuit 2. Further, the counter circuit 1-3 starts counting with respect to the clock selected from the required resolution.

The pen 3 is driven by the vibrator drive circuit 2 by the signal output from the drive signal generation circuit 1-2, the elastic wave generated thereby is detected by the sensor 6 and the detection circuit 9, and the detection signal is the detection signal. It is input to the input port 1-5. In accordance with this detection signal, the latch corresponding to each sensor in the latch circuit 1-4 takes in the counter value and holds the value. The judgment circuit 1-6 outputs a signal to the microcomputer 1-1 when all the necessary data are prepared. Upon receiving this signal, the microcomputer 1-1 sequentially takes in the data held in the latches in the latch circuit 1-4 and calculates the coordinate value from this data.

The obtained coordinate values are transferred to an external circuit such as a display driving circuit or a host computer via the I / O port 1-7. When the data set signal from the determination circuit 1-6 is not output even after the time determined by the circuit delay time maximum delay time or the like has passed, the microcomputer 1-1 does not perform the operation and repeats the operation after the reset. The above-described operation is repeated to determine the designated point coordinates.

FIG. 3 is a block diagram of the pen 3.

In the same configuration, the drive signal output from the arithmetic control unit 1 is amplified to a predetermined voltage by the vibrator drive circuit 2 capable of low impedance drive and applied to the vibrator 4. The drive signal is electromechanically converted by the vibrator 4 (piezoelectric element in this embodiment) to excite the vibration, and the horn 5 amplifies the vibration generated by the vibrator and transmits the vibration by coming into contact with the transmitter 8. .. The vibration frequency of the oscillator 4 is the transmitter 8
A frequency that can generate a plate wave is selected. Further, the vibration mode of the vibrator 4 is selected so that it vibrates mainly in the direction perpendicular to the transmission body 8. More efficiently by setting the vibration frequency of the vibrator 4 as the resonance frequency of the vibrator 4,
It can generate vibration.

The vibration excited in the propagating body 8 by the pen 3 propagates as an elastic wave.

This elastic wave is a wave called a plate wave, and has the advantage that it is less susceptible to surface scratches and obstacles than surface waves. The wave propagating through the transmitter 8 arrives at the sensor 6 with a delay corresponding to the distance. Sensor 6
This wave is electromechanically converted by (for example, a piezoelectric element) and sent to the signal detection circuit 9.

FIG. 4 is an explanatory diagram of signals input to the signal detection circuit, and describes processing of signals detected by one sensor 6.

4-1 is a drive signal waveform, which is composed of several pulses. 4-2 is a waveform detected by the sensor 6, which is delayed from the drive signal 4-1 by a distance corresponding to the distance. The plate wave used in this embodiment is a dispersive wave. Therefore, the relationship between the envelope (4-2-1 broken line) of the detected waveform and the phase (4-2-2) changes with the propagation distance. The speed at which the envelope 4-2-1 advances is defined as a group speed Vg, and the phase speed is defined as a phase speed vp. The coordinates are determined using this group phase velocity. First, focusing only on the envelope, its speed is vg, and at a certain point,
For example, when the peak of the envelope is detected as 4-3, the distance d between the pen and the sensor is given by d = vg · tg (1) with the delay time being tg. Similarly, the distances can be obtained for other sensors, and if the sensors 6 are arranged at the three corner points of the transmission body 8 as shown in FIG. 1, the position of the pen coordinate can be determined from that.

However, not only the envelope but also the phase is focused in order to determine the coordinate value with higher accuracy. If the delay time at a specific point having a phase, for example, the zero-cross point after passing the peak is tp (4-4, 4-5), then d = n · λp + vp · tp (2) is given. Here, λp is a wavelength and n is an integer. From the expressions (1) and (2), the integer n is n = [(vg · tg−vp · tp) / λp + 1 / N] (3). Here, N is a real number other than 0, and an appropriate value is used. For example, if N = 2, then n is determined if the envelope detection accuracy is within ± 1/2 wavelength.

By substituting n obtained by the above equation (3) into the equation (2), the pen-sensor distance can be accurately obtained.

FIG. 5 is a block diagram of a conventional signal detection circuit.

From the signal obtained from the sensor 6, the detection signal T
g, a detection signal Tp is generated and sent to the arithmetic control unit 1. The signal electromechanically converted by the sensor 6 is amplified by the preamplifier circuit 5-1 and passes through the envelope detection circuit 5-2 and the envelope peak detection circuit 5-3 to detect the envelope peak. From this, the Tg signal detection circuit 5 -4 to detection signal T
g is output. Further, a detection signal Tp is output from the comparator 5-8 from the Tg signal and the original signal displayed by the delay time adjusting circuit 5-7.

The above-mentioned circuit is provided for each sensor, and the detection signals of Tg1 to h and Tp1 to h are sent to the arithmetic control unit 1 for the number of sensors h.

Attention is paid to the temperature-delay time characteristic at Tp. If the signal processing circuit is provided with an electrical temperature-delay time characteristic that cancels the temperature characteristic of the propagation delay time in the transmission body 8, a highly accurate device without temperature characteristics can be configured as the coordinate input device as a whole. For example, the delay of the propagation delay time of about 15~20nsec / ^o C in transfer body 8 is measured, and advances the same only in the signal processing circuit, i.e. if circuit issuing a -15~-20nsec / ^o C delay .. The specific configuration is as shown in FIG. This has a configuration in which the temperature correction circuit 7-1 having the above-mentioned temperature characteristic is incorporated in the block diagram of FIG.

A specific example of the temperature correction circuit 7-1 will be described.
For example, the signal frequency of the coordinate input device of this embodiment is set to 250K.
If the frequency is set to Hz, the low-pass filter (LPF) as shown in, for example, FIG. 8 is configured in order to have no influence on the detection signal waveform and to give the circuit delay time a temperature characteristic opposite to the above-mentioned temperature characteristic of the propagation delay time. do it.

The frequency generated by the vibrating pen is 500 KHz.
If the cutoff frequency f _c is 500 KHz or more, the detection signal waveform is not affected. Therefore, f _c = 50
When it is set to 0 kHz, it can be configured with R = 1 kΩ and c = 320 pF. The capacitor has one for temperature compensation, for example, those having a temperature coefficient of -750 ppm / ^o C. Temperature characteristic of -1.5nsec / ^o C can be obtained when configuring the LPF in FIG. 8 using this capacitor. Thus since it is necessary to temperature compensation circuit with a temperature characteristic of the circuit delay of -15nsec / ^o C for some of the temperature characteristic of the propagation delay time of 15nsec / ^o C, -7500ppm
/ ^O C or to use a capacitor having a temperature coefficient of, or LPF of FIG. 8 by connecting 10 stages -15Nsec /
^o The structure will have a C characteristic. Needless to say, the same correction can be made for other transmission paths (for example, the horn 5). Therefore, the temperature characteristic can be similarly corrected for the entire vibration transmission path.

Needless to say, if such temperature correction is performed immediately after the preamplifier circuit 5-1, not only Tp but also Tg is corrected.

In the arithmetic and control unit 1, Tg1 to h and Tp1 to
The counter value is latched according to the h signal.

From this value, the microcomputer calculates the distances d1 to h between each sensor and the pen from the above equations (2) and (3). The number of sensors is arbitrary, but two or more sensors are used, but when three sensors are used as in the present embodiment, when the sensors are arranged as shown in FIG. 6, they are instructed from the distances d ₁ , d ₂ , d _{3 with} respect to the sensors S 1, S 2, S ₃ . The coordinates (x, y) of the point P are x = X / 2 + {(d ₁ + d ₂ ) · (d ₁ −d ₂ ) / 2X} (4) y = Y / 2 + {(d ₁ + d ₃ ). _{· (d 1 -d 3) /} 2Y} ... given by (5), can determine the coordinates. However, X is the distance between the sensors S1 and S2, and Y is the distance between the sensors S1 and S3.

With the configuration and procedure as described above, it is possible to realize a coordinate input device capable of accurate coordinate detection by correcting the temperature characteristic of the vibration transmitting plate without providing a temperature sensor or the like.

[0035]

[Embodiment 2] In the above embodiment, an LPF is used as a temperature correction circuit.
However, if the signal processing circuit of the coordinate input device such as the preamplifier circuit 5-1 and the delay time adjusting circuit 5-7 is used without using a special circuit, the temperature characteristic of the propagation delay time described above is used. It is possible to perform temperature correction by providing a temperature characteristic of circuit delay that cancels out.

[0036]

As described above, it is possible to provide a coordinate input device which has a simple structure and which corrects a coordinate detection deviation due to a change in the outside air temperature and improves the coordinate detection accuracy.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment.

[Fig. 2] Block diagram of arithmetic control unit

[Fig. 3] Vibration pen configuration diagram

FIG. 4 is an explanatory diagram of detected waveforms.

FIG. 5: Block diagram of signal detection circuit

FIG. 6 is an explanatory diagram of determining coordinates.

FIG. 7 is a basic configuration diagram of a coordinate input device.

FIG. 8 Temperature correction circuit

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Katsuyuki Kobayashi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Masaki Tokioka 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Within the corporation

Claims (2)

[Claims] 1. A coordinate input device for detecting the vibration of the vibration transmitting body by means of a vibration detecting means arranged on the vibration transmitting body to detect the coordinates of a vibration source on the vibration transmitting body. A coordinate input device comprising: a vibration transmitter and a compensating means for compensating the temperature characteristic of the vibration transmission speed in the vibration transmission path. 2. The coordinate input device according to claim 1, wherein the compensating means is a delay circuit provided in the vibration detecting means for performing temperature compensation of a delay time.