JPH0648456B2 - Coordinate input device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a coordinate input device, and particularly to a vibration transmission plate of the vibration pen by detecting vibration input from a vibration pen by a plurality of sensors provided on the vibration transmission plate. The present invention relates to a coordinate input device that detects the above coordinates.

[Prior Art] Conventionally, a coordinate input device using various input pens, tablets and the like has been known as a device for inputting handwritten characters, graphics and the like into a processing device such as a computer. The following various methods are known for detecting the coordinates of the tablet of this type of device.

1) A method that detects changes in the resistance value of the sheet material that is placed opposite to the resistance film.

2) A method to detect electromagnetic or electrostatic induction of conductive sheets that are placed opposite to each other.

3) A method to detect ultrasonic vibration transmitted from the input pen to the tablet.

[Problems to be Solved by the Invention] Each of the above conventional methods has the following problems.

First, the resistance film method of 1) requires an expensive resistance film with high uniformity because the uniformity of the resistance film determines the detection accuracy, or because the tablet cannot be made transparent, it can be used by overlapping it on the display etc. There are drawbacks such as not being possible.

The inductive method of 2) is also difficult to be transparent, and it is difficult to construct a large tablet because a large number of matrix electrodes are provided.

On the other hand, in the ultrasonic method 3), a vibration transmission plate made of a transparent material such as acrylic or a glass plate provided with a vibration sensor such as a piezoelectric element can be used as the tablet. In addition, in the methods 1) and 2), the operator has to specify the input state and non-input state by a switch operation, but in the ultrasonic method, this is not the case and the manuscript is written by hand. Just move the vibrating pen up and down on the tablet as you would at any time.

However, this ultrasonic method has a problem that the detection accuracy is lowered due to scratches or obstacles on the vibration transmission plate of the tablet. Further, in the method of transmitting ultrasonic vibration as an elastic wave on the vibration transmission plate, there is a problem that the group velocity and the phase velocity of the plate wave deviate depending on the threshold value of the detection signal, and a wavelength-dependent detection error occurs. there were.

Further, in this method, the input / non-input state is switched only by the upper and lower sides of the input pen as described above, but there is a problem that an error occurs in the vibration detection during a transitional period when the input pen comes in contact with or separates from the vibration transmission plate. .

An object of the present invention is to improve the above-mentioned problem of the detection error in the ultrasonic method, which has various advantages that it can be easily made transparent and can be constructed relatively inexpensively as compared with other methods.

[Means for Solving Problems] In order to solve the above problems, in the present invention, the vibration transmitted to the vibration transmission member by contacting the vibration input means is provided in the vibration transmission member. In a coordinate input device for deriving a contact coordinate position of the vibration input means with respect to the vibration transmitting member, which is detected by a plurality of vibration detecting means, a plurality of peak holding detection signal levels of the plurality of vibration detecting means are held. The peak pressure holding means, the writing pressure detection means for obtaining writing pressure information by adding the peak level values held in the plurality of peak level holding means, and the writing pressure information detected by the writing pressure detection means. In comparison with a predetermined threshold value, when the writing pressure information is equal to or more than a predetermined threshold value, a deriving means for deriving the coordinates of the vibration input point by the vibration input means is adopted. .

[Operation] According to the above configuration, the writing pressure information is obtained by adding the peak level value of the detection signal level of each of the plurality of vibration detecting means, and the vibration input is performed when the writing pressure information is equal to or more than a predetermined threshold value. By capturing the input of means, prevent false detection,
Highly accurate coordinate input is possible.

[Examples] Hereinafter, details of the present invention will be described based on Examples shown in the drawings.

FIG. 1 shows the structure of a coordinate input device adopting the present invention. The coordinate input device shown in FIG. 1 constitutes an input / output device for characters, figures, images and the like together with a display 11 'which is a liquid crystal display of the dot matrix type or the like.

In the figure, reference numeral 8 is a vibration transmission plate made of acrylic, glass plate, or the like, which is made of silicon rubber or the like in order to prevent the vibration transmitted from the vibration pen 3 from being reflected at the peripheral portion. It is supported by the preventive material 7. Three vibration sensors 6 are attached to the corners of the vibration transmission plate 8 to detect elastic waves transmitted from the vibration pen 3.

The vibration transmission plate 8 is arranged on a display 11 'composed of a liquid crystal display or the like, and constitutes an information input / output device. On the display 11 ', characters and figures input via the vibration transmission plate 8 are fed back, or a prompt for input operation to the vibration transmission plate is displayed.

The vibration pen 3 that transmits ultrasonic vibrations to the vibration transmission plate 8 is
It has a vibrator 4 composed of a piezoelectric element or the like inside, and transmits the ultrasonic vibration generated by the vibrator 4 to the vibration transmission plate 8 via the horn portion 5 having a sharp tip. FIG. 2 shows the structure of the vibrating pen 3. The vibrator 4 built in the vibrating pen 3 is driven by the vibrator driving circuit 2. The drive signal of the oscillator 4 is supplied as a low level pulse signal from the arithmetic and control circuit 1 of FIG. 1, amplified by the oscillator drive circuit 2 capable of low impedance drive with a predetermined gain, and then supplied to the oscillator 4. Is applied. The electrical drive signal is
It is converted into mechanical vibration by the oscillator 4, and the horn unit 5
Is transmitted to the vibration transmission plate 8 via.

As the vibration frequency of the vibrator 4, a frequency for generating a plate wave on the vibration transmission plate 8 such as acrylic or glass is selected. Further, the operation mode of the vibrator 4 is selected with respect to the vibration transmission plate 8 so as to mainly vibrate in the vertical direction of FIG. The vibration frequency of the vibrator can be efficiently generated by selecting the resonance frequency of the vibrator 4.

The elastic wave transmitted to the vibration transmission plate 8 as described above is a wave called a plate wave, and has a scratch on the surface as compared with a surface wave.
It has the advantage of being less susceptible to obstacles. The wave propagating in the vibration transmission plate 8 is delayed by time according to the distance, and the vibration sensors 6 provided at the three corners of the vibration transmission plate 8 are delayed.
To reach. Therefore, the position of the vibration pen 3 on the vibration transmission plate 8 can be detected by detecting the vibration by the vibration sensor 6 and measuring the delay time thereof.

Referring again to FIG. 1, the output signal of the vibration sensor 6 composed of a piezoelectric element or the like is input to the waveform detection circuit 9 and converted into a detection signal which can be processed by the arithmetic control circuit 1 composed of a microcomputer and a memory. To be done.
The arithmetic control circuit 1 detects the position of the vibrating pen 3 on the vibration transmission plate 8 based on the above-described delay time arithmetic processing.
The display 11 ′ in FIG. 1 is driven by the arithmetic and control circuit 1 via the display drive circuit 10.

FIG. 3 shows the structure of the arithmetic control circuit shown in FIG. Here, except for the control system of the drive circuit of the display 11 'of FIG. 1, only the circuit for processing the vibration generation of the vibration pen and the vibration detection from the vibration transmission plate is shown.

The microcomputer 11 has an internal counter, ROM and RAM built therein. The drive signal generation circuit 12 generates a drive pulse for the vibrator drive circuit 2 shown in FIG. 1, and is started by the microcomputer 11 in synchronization with the arithmetic circuit. The count value of the counter 13 is
It is latched in the latch circuit 14 by the microcomputer 11.

The detection signal input from the waveform detection circuit 9 is input to the input port 15, is compared with the count value in the latch circuit 14 by the determination circuit 16, and the result is transmitted to the microcomputer 11. The driving of the display 11 ′ and the input / output with other processing devices such as a computer system are performed via the input / output port 17.

FIG. 4 illustrates a detected waveform input to the waveform detection circuit 9 of FIG. 1 and a delay time measurement process based on the detected waveform. In FIG. 4, reference numeral 41 is a drive signal pulse applied to the vibrating pen 3. With such a waveform, the ultrasonic signal generated by the driven vibrating pen 3 is transmitted as an elastic wave in the vibration transmitting plate 8 and is detected by the vibration sensor 6 to be detected as indicated by reference numeral 42 in FIG. Form a waveform. The detected waveform is delayed by the time tg before being transmitted from the vibrating pen to the vibration sensor via the vibration transmission plate 8. In the plate wave used in this embodiment, the relationship between the envelope 421 and the phase 422 of the detected waveform changes with the propagation distance in the vibration transmission plate.

Let the velocity of the envelope be the group velocity Vg and the velocity of the phase be the phase velocity vp.

The distance between the vibration pen 3 and the sensor can be detected from the group velocity and the phase velocity. First, focusing only on the envelope 421, its speed is vg, and a certain point, for example, the peak of the envelope is denoted by reference numeral 4 in FIG.
3 is detected, the distance d between the vibration pen and the vibration sensor 6 is given by d = vg · tg (1) with the delay time being tg. Although the above equation relates to one of the vibration sensors 6, the same equation can measure the distance between the other two vibration sensors and the vibrating pen.

Further, in order to determine the coordinate value with higher accuracy, processing based on the detection of the phase signal is performed. Phase waveform 42 of FIG.
Assuming that the delay time of two specific detection points, for example, the zero cross point after passing the peak is tp as shown in FIG. 4, the distance d between the vibration sensor and the vibration pen is d = n · λp + vp · tp ... (2) Here, λp is the wavelength of the elastic wave, and n is an integer.

From the equations (1) and (2), the integer n is Is shown. Here, N is a real number other than 0, and an appropriate value is used. For example, if N = 2, then n can be determined if the detection accuracy of the envelope is within ± 1/2 wavelength. The distance between the vibrating pen and the sensor can be accurately measured by substituting n obtained as described above into the equation (2).

The distance measurement based on the two delay times tg and tp shown in FIG. 4 is performed by the waveform detection circuit 9 shown in FIG. The waveform detection circuit is constructed as shown in FIG. In FIG. 5, the output signal of the vibration sensor 6 is amplified by the preamplifier circuit 51 and amplified to a low level. The amplified signal is input to the envelope detection circuit 52, only the envelope is extracted, and the envelope peak detection circuit 53 further detects the timing of the peak of the envelope of the detection signal. In the peak signal detection, a Tg signal having a predetermined waveform is formed by the signal detection circuit 54 composed of a mono-multivibrator or the like and input to the arithmetic control circuit 1. The comparator detection circuit 58 forms a phase delay time Tp detection signal from the Tg signal and the original signal delayed by the delay time adjustment circuit 57.
Entered in. The circuit shown above is for one vibration sensor 6, and similar circuits are provided for the other vibration sensors. When the number of sensors is generalized to h, the detection signals of the envelope delay times Tg _{1 to} h and Tp _{1 to} h are input to the arithmetic control unit 1.

In the arithmetic control circuit of FIG. 3, the above Tg _{1 to} h and Tp _{1 to} h signals are input from the input port 15, and the count value of the counter 13 is latched by the respective timings as a trigger.
Take in. As described above, since the counter 13 is started in synchronization with the driving of the vibrator, the latch circuit 14 receives the data of the delay time of each of the envelope and the phase.

When three vibration sensors are arranged at the corners of the vibration transmission plate 8 as shown in FIG. 6 as shown by reference symbols S _{1 to} S ₃ , the positions described above with reference to FIG. The linear distances d _{1 to} d ₃ to the vibration sensor can be obtained. The coordinate (x, y) of the position P of the vibrating pen 3 is based on the Pythagorean theorem, Becomes Here, X and Y are the distances from the sensor of the origin of the vibration sensor at the positions of S ₂ and S ₃ .

As described above, the position control of the vibrating pen can be detected in real time by performing the calculation by the calculation control circuit 1.

As described above, in the conventional coordinate detection method, it is necessary to switch between input and non-input states by switch operation,
There was a problem that the operation feeling was not good. Basically, in the above-mentioned ultrasonic method, the input or non-input state can be switched without vibration, but erroneous detection occurs in the transient device where the vibration pen 3 comes in contact with the vibration transmission plate 8 or separates from it. there is a possibility.

FIG. 7 shows the writing pressure and the amplitude of the detection signal by the single vibration sensor 6 during the transition period when the vibration pen 3 contacts the vibration transmission plate 8. Region A in FIG. 7 shows a state in which the vibration pen 3 makes contact and the amplitude of the detection signal rises, region B shows a state in which the writing pressure and the detection signal rise, and region C shows a state in which the writing pressure and the detection signal have entered a stable period. Is shown.

Since the level of the detection signal is not stable in the area A or B, there is a possibility of erroneous detection. Therefore, in this embodiment, a writing pressure detection circuit is provided as indicated by reference numeral 59 in FIG.
The coordinate detection of the arithmetic processing circuit 1 is prohibited when a sufficient writing pressure of the vibrating pen 3 is not applied.

FIG. 8 illustrates the processing of the writing pressure detection circuit 59. Here, in order to simplify the explanation, a case where the vibration sensor 6 is single is considered. The upper third row of FIG. 8 shows the drive signal of the vibration pen 3, the detection signal of the vibration sensor 6, and the envelope of the detection signal separated by the envelope detection circuit 52, as in the upper third row of FIG. Here, the writing pressure is detected through the amplitude of the detection signal of the vibration sensor 6 using the relationship shown in FIG.

In the present embodiment, as shown in the third row of FIG. 8, the extracted envelope is sliced at a predetermined threshold value VT to produce an eighth slice.
A writing pressure detection signal 81 as shown in the fourth row of FIG. 4 is formed. This writing pressure detection signal is sent to the arithmetic control circuit 1, and the arithmetic control circuit 1 performs the aforementioned coordinate calculation only when the writing pressure detection signal 81 is at a high level.

Regarding the level of the threshold value VT, in the relationship between the writing pressure and the amplitude in FIG. 7, the closer to the region C, the more reliable detection can be performed, but the detection signal is attenuated as the distance between the vibrating pen and the sensor is increased. It is preferable to set it in the area B as indicated by.

FIG. 9 shows an embodiment in which the writing pressure is detected from the outputs of the plurality of vibration sensors 6. The configuration other than the writing pressure detection circuit of FIG. 9 is exactly the same as that of FIG.

In the configuration of FIG. 9, the detection signal of the vibration sensor 6 is extracted from the output of the preamplifier 51 or the output of the envelope detection circuit 52 as shown by the broken line, and is input to the peak hold circuit 91 of the writing pressure detection circuit 59. . The peak hold detection circuit is another vibration sensor 6 provided on the vibration transmission plate 8.
A plurality of outputs are provided to input the outputs in parallel.

The outputs of the respective peak hold circuits 91 are added by an adder circuit 92, and the added signal level is compared with a predetermined threshold value by a comparator 93 to form a writing pressure detection signal, which is given to the arithmetic control circuit 1. To be In this case, the threshold value is the threshold value VT in the case of the above single sensor.
Set to the sum of.

With such a configuration, writing pressure information can be obtained from the plurality of vibration sensors 6. The outputs of the plurality of vibration sensors 6 may be combined by a method other than addition.

According to the above-described embodiment, since ultrasonic vibration is transmitted to the vibration transmission plate 8 as a plate wave of elastic wave, it is possible to reduce the interference of the vibration transmission plate 8 due to scratches or obstacles and to perform highly accurate coordinate detection. You can

Further, since the pen pressure is detected and the coordinate calculation is performed only in the pen pressure area equal to or larger than a predetermined value, accurate coordinate detection can be performed. Therefore, by merely moving the vibrating pen up and down on the vibration transmitting plate, handwriting input can be performed with a feeling of operation that is no different from normal handwriting work.

[Effect] As is apparent from the above, according to the present invention, the writing pressure information is obtained by adding the peak level value of the detection signal level of each of the plurality of vibration detecting means, and this writing pressure information is a predetermined threshold value. Since the input of the vibration input means is taken in the above case, erroneous detection can be prevented, highly accurate coordinate input can be performed, and an excellent coordinate input device having an operation feeling that does not change from ordinary handwriting work. In particular, there is an excellent effect that erroneous detection can be prevented during the transitional period when the vibration input means is moved up and down, or erroneous detection due to the influence of the attenuation of the vibration level due to the distance from the input point to the detection point.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing the configuration of a coordinate input device adopting the present invention, FIG. 2 is an explanatory diagram showing the structure of the vibrating pen of FIG. 1, and FIG. 3 is a diagram of the arithmetic control circuit of FIG. FIG. 4 is a block diagram showing the structure, FIG. 4 is a waveform diagram showing a detection waveform for explaining the distance measurement between the vibrating pen and the vibration sensor, and FIG. 5 is a block diagram showing the configuration of the waveform detection circuit of FIG. , FIG. 6 is an explanatory view showing the arrangement of the vibration sensor, FIG. 7 is a diagram showing the relationship between the pen pressure of the vibrating pen and the amplitude of the detection signal, and FIG. 8 is a waveform diagram showing the pen pressure detection process. , FIG. 9 is a block diagram showing the overall configuration of the writing pressure detection circuit and the waveform detection circuit. 1 ... Arithmetic control circuit, 3 ... Vibration pen 4 ... Oscillator, 6 ... Vibration sensor 8 ... Vibration transmission plate, 51 ... Preamplifier 52 ... Envelope detection circuit 54, 58 ... Signal detection circuit 91 ... Peak hold circuit 92 ... Addition Circuit, 93 ... Comparator

Claims (1)

[Claims] 1. Vibrations transmitted to a vibration transmission member by contacting the vibration input means are detected by a plurality of vibration detection means provided on the vibration transmission member, and are transmitted to the vibration transmission member of the vibration input means. In the coordinate input device for deriving the contact coordinate position of, the plurality of peak level holding means for holding the peak level of the detection signal level of each of the plurality of vibration detection means, and the peaks held by the plurality of peak level holding means. The writing pressure detection means for obtaining writing pressure information by adding the level value and the writing pressure information detected by the writing pressure detection means are compared with a predetermined threshold value, and the writing pressure information is compared with a predetermined threshold value. A coordinate input device having deriving means for deriving the coordinates of the vibration input point by the vibration input means when the above is the case.