JPH05181595A - Coordinate input device - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a highly accurate coordinate input device capable of stable input. In a coordinate input device that includes a vibrating pen having a vibration generating unit, a propagation member that propagates an elastic wave, and a vibration sensor, the coordinate input device determines coordinates based on the propagation delay time of the elastic wave. The present invention is characterized by including time detection means for detecting the phase difference of the vibration of the sensor, and recognizing the coordinate input position by using a plurality of frequencies of the sinusoidal vibration of the vibrating pen. [Effect] Since only the phase signal of the signal waveform is used and only the signal of the specific frequency is used, it is difficult to be influenced by noise and easy to remove. Further, since the amplitude information is not used, there is an effect that it is less susceptible to the influence of placing a hand on the vibration transmission plate and the influence of natural damping.

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 inputting handwritten characters, graphics, etc. into a processing device such as a computer.

[0002]

2. Description of the Related Art A conventional coordinate input device is disclosed in Japanese Patent Laid-Open No. 2-17.
There is a sensor using sensors arranged in a matrix in the XY directions as described in Japanese Patent No. 1819.
In this method, the resolution is determined by the processing accuracy of the sensor array. The larger the area of the coordinate input device, the easier it is to use, but the larger the size and the higher the resolution, the higher the processing cost, and there is a limit in manufacturing a product.

As an improved device thereof, Japanese Patent Application Laid-Open No. 3-4271 is known.
There is a device as described in Japanese Patent Publication No. 2 which emits ultrasonic waves from a signal generating pen and recognizes the position with three sensors. In this method, in order to transmit ultrasonic waves, several pulses are emitted to generate a transmission signal, the propagation time of ultrasonic waves is measured,
The distance between the vibration source and the vibration sensor is calculated. For example, it is assumed that glass is used for the propagation member and a high-speed drive type IC is used for time measurement, and measurement is performed at 50 MHz. The velocity of the transverse wave of ultrasonic waves is 5440 m / s, and the time measurement resolution is 20 n.
s. The measurement resolution of the distance between the vibrating pen and the vibration sensor is about 0.11 mm, which is a level with no practical problems.

However, when ultrasonic waves are used as a signal medium, there is a problem of attenuation of vibration energy. Since the vibration energy attenuates in proportion to the square of the distance, the amplitude of the wave sharply decreases. The efficiency with which the energy is transmitted changes depending on the force (writing pressure) applied to the propagating member and the angle (pen shape of the pen). Since the hand holding the vibrating pen is placed on the propagation member, ultrasonic energy is absorbed by the support of the hand and the propagation member.

As described above, the ultrasonic method deals with a signal whose waveform amplitude is easily varied. As countermeasures, it is necessary to take various measures such as automatic gain control of the input signal of the vibration sensor, adjusting the output of the vibration pen by measuring the writing pressure with the pressure sensor, and controlling the undulation and surface roughness of the propagation member. Is becoming

Further, in this method, the envelope shape of amplitude in the input signal waveform of the vibration sensor is used,
The time of ultrasonic waves is measured. Therefore, the fluctuation of the amplitude greatly affects the position recognition accuracy.

[0007]

In the prior art of the ultrasonic system described above, the fluctuation of the signal level greatly affects the position recognition accuracy, and it is necessary to control the signal processing in a complicated manner.

An object of the present invention is to provide a coordinate input device,
An object of the present invention is to provide a device having high resolution recognition accuracy and capable of coping with signal attenuation and disturbance.

[0009]

A coordinate input device of the present invention is provided with a vibrating pen having a vibration generating means, a propagating member for generating and propagating an elastic wave by bringing the vibrating pen into contact, and the propagating member. In a coordinate input device for determining coordinates from the propagation delay time of the elastic wave, the filter means for outputting a sinusoidal vibration of a specific frequency from a vibration pen and filtering the detection signal of the vibration sensor. And a phase detecting means for detecting a phase difference between the sine wave vibration of the vibration pen and the vibration of the vibration sensor.

Further, the present invention is characterized in that the coordinate input position is recognized by using a plurality of frequencies of sinusoidal vibration of the vibrating pen.

Further, the filter means is a bandpass filter means whose center frequency is the frequency of the vibrating pen.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a main block diagram of an embodiment of the present invention. The sine wave signal of the specific frequency specified by the arithmetic and control circuit 1 is output from the drive signal generation circuit, and the vibrator drive circuit 2
And horn 5 placed at the tip of the vibration pen 3 by the vibrator 4
Vibrate. When the vibration pen 3 is brought into contact with the vibration transmission plate 8, the vibration is transmitted to the vibration sensor 6. Since the vibration propagation speed is constant in a material having a constant density, the distance from the sensor changes depending on the position of the vibrating pen, and the time required for propagation changes. Then, the phase when reaching the sensor changes depending on the position of the vibrating pen.

The signal phase measuring circuit 9 measures the phase of the waveform and sends it to the arithmetic and control circuit 1. In the arithmetic and control circuit 1,
The frequency and phase of the vibration pen 3 are stored. Next, another frequency is output and the phase is measured. This operation is repeated several times to calculate the distance between the vibration pen and the vibration sensor.

The method of calculating the distance from the phase is as follows. The size of the vibration transmission plate 8 determines the maximum value of the distance between the vibration pen 3 and the vibration sensor 6. It is temporarily set to 200 mm. If the distance between the vibration pen 3 and the vibration sensor 6 is L
0 <L <200 mm. The propagation velocity of the ultrasonic wave that continues on the vibration transmission plate 8 is 5000 m / S.

The vibration pen 3 is brought into contact with the vibration transmission plate 8 and
It is assumed that when vibration is sent at a frequency of 167 kHz and a wavelength of 30 mm for the second time, the phase difference at the vibration sensor 6 is 300 degrees, which is 25 mm in terms of wavelength. In addition, frequency 2
It is assumed that when vibration is sent at 00 kHz and a wavelength of 25 mm, the phase difference at the vibration sensor 6 is 72 degrees, which is 5 mm in terms of wavelength.

It can be seen from the first measurement that the distance L is the sum of the integer multiple of the wavelength of 30 mm and 25 mm. Therefore, 25
mm, 55 mm, 83 mm, 115 mm, 145 mm,
It is either 175 mm.

From the second measurement, it can be seen that the distance L is the sum of the integer multiple of the wavelength of 25 mm and 5 mm. The remainders obtained by dividing the six distance candidates raised in the first time by 25 mm are:
0mm, 5mm, 10mm, 15mm, 20mm, 0m
m. Among these, the second measured value matches when the distance L = 55 mm.

For finer measurement, phase measurement may be performed at a shorter wavelength.

In this system, as can be seen from FIG. 2, the position can be determined if there are two sensors. This is because when two adjacent sensors are selected from the four corners of the rectangular vibration transmission plate 8 and the sensors are arranged, only one point is obtained when the distance from each sensor is specified. However, it is effective to arrange three sensors and obtain an average value in order to correct the fluctuation of the propagation velocity due to temperature.

Next, the method of measuring the phase signal will be described with reference to FIG. There are several methods to measure the phase, but this time we took the method of performing the Fourier transform to determine the phase. This has the advantage that the average phase of the waveform can be obtained and the accuracy is high. First, the signal of the drive signal generation circuit 12 and the signal of the vibration sensor 6 are amplified to a voltage that is easy to analyze, and passed through band pass filters 17 and 18 that pass only the vicinity of the frequency of the signal. Next, each signal is A / D converted into a digital signal. The A / D conversion data of the vibration sensor is monitored to detect whether or not an ultrasonic signal has come,
Sample and hold the required number of data. The frequency of each data is decomposed by the Fourier transform circuit, and the phase of the signal frequency is obtained. Fourier transform is digital.
High-speed operation was performed using a signal processor.

The calculation / control circuit stores the vibration wavelength and phase data, examines the phase for several kinds of wavelengths, and estimates the position of the vibration pen.

The above contents are shown in a flow chart in FIG.

As the method of obtaining the phase, other than the method by the Fourier transform described above, a method of directly measuring the time of the phase difference, a method of adding the waveforms to be compared and measuring the amplitude change of the waveform, and a mutual method There is a method of checking by correlation.

Although ultrasonic waves are used as the medium for transmitting signals in this embodiment, if the calculation speed can be increased, electromagnetic waves,
Light, etc. can be considered.

[0025]

As described above, according to the present invention, since only the phase signal of the signal waveform is used and only the signal of the specific frequency is used, it is difficult to be influenced by noise.
Easy to remove. Further, since the amplitude information is not used, there is an effect that it is less susceptible to the influence of placing a hand on the vibration transmission plate and the influence of natural damping.

[Brief description of drawings]

FIG. 1 is a block diagram of a coordinate input device according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating coordinate calculation processing according to an embodiment of the present invention.

FIG. 3 is a block diagram of a signal phase measuring circuit according to an embodiment of the present invention.

FIG. 4 is a flowchart diagram of a signal processing process according to an embodiment of the present invention.

FIG. 5 is a block diagram of a conventional coordinate input device.

[Explanation of symbols]

 1 operation control circuit 2 vibrator drive circuit 3 vibrating pen 4 vibrator 5 horn 6a vibration sensor A 6b vibration sensor B 6c vibration sensor C 7 antireflection material 8 vibration transmission plate 9 signal phase measurement circuit 10 display drive circuit 11 display 12 Drive signal generation circuit 13 I / O port 14 External circuit 15 Amplification circuit 16 Amplification circuit 17 Bandpass filter 18 Bandpass filter 19 A / D converter 20 A / D converter 21 Fourier transform circuit 22 Fourier transform circuit 23 Signal waveform detection circuit 24 Timing circuit 25 Distance between vibration sensor A and vibration pen 26 Distance between vibration sensor B and vibration pen 30 Start 31 Determine frequency of vibration pen 32 Vibration of vibration pen 33 Detection by vibration sensor 34 Cut unnecessary signal with filter 35 A / D conversion 36 Fourier transform 39 computes the distance to obtain 38 pen and sensor data 37 number necessary to calculate the phase end

Claims (3)

[Claims] 1. A vibrating pen having a vibration generating means, a propagating member for generating and propagating an elastic wave by bringing the vibrating pen into contact with each other, and a vibration sensor provided on the propagating member. In the coordinate input device that determines the coordinates of the touch point of the vibrating pen from the delay time, generate a sinusoidal vibration of a certain specific frequency from the vibrating pen,
A coordinate input device comprising: filter means for filtering a detection signal of the vibration sensor; and phase detection means for detecting a phase difference between the sine wave vibration of the vibration pen and the vibration of the vibration sensor. 2. The coordinate input device according to claim 1, wherein the coordinate input position is recognized by using a plurality of frequencies of sinusoidal vibration of the vibrating pen. 3. The coordinate input device according to claim 1, wherein the filter means is bandpass filter means having a center frequency of a vibration frequency of the vibrating pen.