JPH0758456B2 - 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 and tablets has been known as a device for inputting handwritten characters, graphics and the like into a processing device such as a computer. Among them, as a coordinate input device that utilizes ultrasonic vibration, a coordinate input device that detects the propagation time of ultrasonic vibration transmitted from the input pen to the vibration transmission plate and detects the coordinate position of the input pen is the fourth. The structure shown in the figure has been devised.

The vibrating pen 143 is a pen for generating elastic waves in a vibration transmitting plate 146 that transmits elastic waves, and has a vibration generating piezoelectric element (vibrator) 142 inside. Reference numeral 141 is a drive circuit for this pen. Reference numeral 144 is a vibration sensor including a piezoelectric element for detecting the elastic wave transmitted through the vibration transmission plate 146. Reference numeral 145 is a vibration isolator that prevents reflection at the end surface of the vibration transmission plate 146.

Next, in FIG. 5, reference numeral 149 is a pen drive waveform.
Reference numeral 150 denotes a detection waveform in the sensor, which is amplified by the preamplifier circuits 130 to 132 of FIG. 4 with a predetermined gain for each sensor and then input to the vibration waveform detection circuits 133, 134 and 135. The vibration waveform detecting circuit extracts the envelope waveform 153 of FIG. 5, detects the peak point 151 of the envelope and the zero-cross point 152 of the first detected waveform after the peak point, and outputs the detection signal to the latch circuits 136 and 137 of FIG. , 138 to enter. The latch circuit latches the timing result of the timing counter 139 started in synchronization with the drive signal by the detection signal and outputs it to the control device 140 as the phase delay time tp and the group delay time tg in FIG. The control device detects the coordinates of the pen input position P (x, y) by the following calculation based on the above tp and tg.

FIG. 6 schematically shows the arrangement of the vibration sensor 144 shown in FIG. In FIG. 6, the distance between the vibration sensor positions S0 and S1, S2 is rx, ry, S0, S1, and the distance between S2 and P (x, y) is d0,
d1, d2, Vp is the phase velocity of the elastic wave measured in advance Given in. Here, τ0, τ1, and τ2 are the above tp, and the frequency of the elastic wave measured in advance is f, (Subscript i = 0 to 2 indicates a sensor).

N in the above equation is based on the previously measured group velocity Vg of the elastic wave and the above tg. Is an integer given by (INT [] indicates integerization).

Therefore, conventionally, the coordinate value is calculated by making the envelope waveform 153 of FIG. 5 and measuring tgi and tpi.

[Problems to be Solved by the Invention] However, in the above-described embodiment, there is no means for knowing the frequency at the detection point of the transmission vibration, and it is treated as a constant calculated from the frequency measured by another means in advance. When the frequency of the elastic wave propagating in the vibration transmitting plate changes, the detected coordinates (x, y) may deviate from the coordinates of the actual input point.

[Means for Solving the Problems] In order to solve the above problems, in the present invention, vibration input from the vibrating pen is detected by a plurality of vibration sensors provided on a vibration transmitting plate to transmit the vibration of the vibrating pen. In the coordinate input device for detecting the coordinates on the plate, from the transmission time measuring means for measuring the transmission time of the vibration transmitted to the vibration transmission plate, and the time interval of the zero cross point of the vibration transmitted to the vibration transmission plate. Derivation for deriving the coordinates of the vibration input point by the vibrating pen on the vibration transmission plate using the period measurement means for measuring the period, and the vibration transmission time and period measured by the transmission time measurement means and the period measurement means. A structure provided with means is adopted.

[Operation] According to the above configuration, when performing coordinate calculation, the coordinate calculation is performed based on the actually measured vibration cycle instead of using the vibration frequency of the fixed value as in the conventional case. Will be possible.

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

FIG. 1 shows the structure of an information input device adopting the present invention. The information input device shown in FIG. 1 is a device for inputting coordinates by a vibrating pen 118 to an input tablet composed of a vibration transmission plate 122.

In FIG. 1, reference numeral 122 is a vibration transmission plate made of acrylic, glass plate or the like, and transmits the vibration transmitted from the vibration pen 118 to three vibration sensors 123 provided at the corners thereof.
In this embodiment, the coordinates of the vibration pen 118 on the vibration transmission plate 122 are detected by measuring the transmission time and the vibration cycle of the ultrasonic vibration transmitted from the vibration pen 118 to the vibration sensor 123 via the vibration transmission plate 122. To do.

The vibration transmitting plate 122 has its peripheral portion supported by an antireflection material 121 made of silicon rubber or the like in order to prevent the vibration transmitted from the vibrating pen 118 from being reflected in the peripheral portion and returning toward the central portion. It

A vibrating pen 118 that transmits ultrasonic vibrations to the vibration transmitting plate 122 has a vibrator 119 formed of a piezoelectric element or the like inside, and a ultrasonic wave generated by the vibrator 119 has a horn portion 120 with a sharp tip. The vibration is transmitted to the vibration transmission plate 119 via the vibration transmission plate 119.

The vibrator 119 built in the vibrating pen 118 is a vibrator driving circuit 11
Driven by 7. The drive signal for the oscillator 119 is a control circuit
It is supplied as a low-level pulse signal from 116, amplified by a predetermined gain by a vibrator driving circuit 117 capable of low impedance driving, and then applied to a vibrator 119.

The electric drive signal is converted into mechanical ultrasonic vibration by the vibrator 119 and transmitted to the diaphragm 122 via the horn unit 120.

The vibration frequency of the vibrator 119 is selected to a value capable of generating a plate wave on the vibration transmission plate 122 such as acrylic or glass. Further, when the vibrator is driven, a vibration mode is selected in which the vibrator 119 mainly vibrates in the direction perpendicular to the vibration transmission plate 122. Also, set the vibration frequency of the vibrator 119 to the vibrator 1
With a resonance frequency of 19, efficient vibration conversion is possible.

The elastic wave transmitted to the vibration transmission plate 122 as described above is a plate wave, and has an advantage that it is less susceptible to scratches and obstacles on the surface of the vibration transmission plate 122 as compared to surface waves.

Further, in FIG. 1, the vibration sensor 123 having the vibration transmission plate 122 provided at the corner portion is also constituted by a mechanical / electrical conversion element such as a piezoelectric element. The output signals of the three vibration sensors 123 are input to the preamplifier circuits 100, 101, and 102, and after being amplified by a predetermined gain, each of the vibration waveform detection circuits 10
5, 108, 111 and the delay circuits 104, 107, 110.

The vibration waveform detection circuit is configured as shown in FIG.

FIG. 2 shows only one system of the vibration waveform detection circuit. In FIG. 2, the signal input from the preamplifier circuit 100 is input to the envelope detection circuit 205, and only the envelope of the detection signal is extracted. The timing of the peak of the extracted envelope is detected by the envelope peak detection circuit 204. The peak detection signal is a signal detection circuit composed of a mono multivibrator, etc.
By 203, the envelope delay time detection signal T of a predetermined waveform
g is formed and input to the latch circuit 113.

Further, a phase delay time detection signal Tp is formed by the comparator detection circuit 206 from this Tg signal and the original signal delayed by the delay time adjustment circuit 200, and is input to the latch circuit 113.

The circuit shown above is for one of the vibration sensors 123,
The same circuit is provided for each of the other sensors. If the number of sensors is generalized to h, the envelope delay time Tg0 to (h-1) and the phase delay time TP0 to (h-
The h detection signals of 1) are input to the latch circuit.

In FIG. 1 again, the latch circuits 113 to 115 fetch the clocked values of the clocking circuit 112 into the latch circuits 113 to 115 by using the above detection signals Tg0 to Tg as triggers, respectively. Since the clock circuit 112 is started in synchronism with the driving of the vibrating pen, the latch circuits 113 to 115 fetch data indicating the delay time of each envelope and phase of the vibration waveform of each sensor.

On the other hand, the output signals from the preamplifier circuits 100 to 102 are input to the delay circuits 104, 107, and 110 separately from the above-mentioned vibration waveform detection circuit, and only for a time equivalent to the time required for processing by each vibration waveform detection circuit. After being delayed, the vibration period measurement circuit 103, 1
Entered in 06, 109.

FIG. 3 is a block diagram showing a vibration cycle detection circuit, showing one of the three systems. The detection waveform input from the delay circuit 110 is input to the comparator 301, and when the center of the amplitude of the waveform is used as the zero reference, the detection waveform increases from the negative side and crosses the zero line.

This detection signal is input to the counter 302 and the one-shot pulse generation circuit 303 as a zero-cross signal. The counter 302 operates the counter based on oscillation sufficiently faster than the oscillation cycle of the input signal to perform the counting operation. The counter clears the count value by the zero-cross signal input from the comparator 301 and starts counting up from zero.

The count value is always output to the latch circuit 304. In the one-shot pulse generation circuit 303, the comparator 3
The output of 01 generates a pulse signal for latching the count value in the latch circuit 304. By the above operation, the time each time the input signal increases from the negative side and crosses the zero line, that is, the oscillation period is latched in the latch circuit 304 one after another.

The output of the latch circuit 304 is input to the latch circuit 305, and the latch circuit 305 latches the output of the latch circuit 304 by using the phase delay time detection signal Tp of this system as a trigger.

The output of the latch circuit 305 is output to the control device 116.
Since this count value is the vibration period at the time of detecting the phase of the detection signal, the reciprocal is obtained by the control device 116 and the frequency f of the vibration detection signal is calculated.
You can ask for 2. Similarly, the detection signals f1 and f0 relating to other sensors can be obtained.

From Tgi, Tpi and fi obtained by the above method, the controller 116 performs the following calculation to determine the coordinates.

However, INT is an integer, Vg is a group velocity, Vp is a phase velocity, i is the number of each sensor, and 0 to 2 in this embodiment. The apparent phase delay time τi, which has a linear relationship with the distance di from n, is the distance between the pen and the sensor. The coordinate value is obtained from this τi. In FIG. 6, the distance between S0 and S1 is rx, and the distance between S0 and S2 is ry.
It is calculated by the following formula.

The coordinate value calculated by this formula is calculated based on the frequency at the coordinate detection point.

As described above, by calculating the coordinates of the vibrating pen using the actually measured values of the vibration wave propagating through the vibration transmission plate, it is possible to accurately detect the coordinates with few errors.

EFFECTS OF THE INVENTION As is apparent from the above description, according to the present invention, the vibration input from the vibrating pen is detected by the vibration sensors provided on the vibration transmitting plate, and the vibration transmitting plate of the vibrating pen is detected. In the coordinate input device for detecting the coordinates at, the transmission time measuring means for measuring the transmission time of the vibration transmitted to the vibration transmission plate, and the period from the time interval of the zero cross point of the vibration transmitted to the vibration transmission plate Cycle measuring means for measuring, and deriving means for deriving the coordinates of the vibration input point by the vibration pen on the vibration transmitting plate using the vibration transmitting time and the cycle measured by the transmitting time measuring means and the period measuring means. Since the configuration provided is used, when performing coordinate calculation, the coordinate calculation is performed based on the actually measured vibration cycle instead of using a fixed value vibration frequency as in the past. There is an excellent effect that accurate coordinate detection processing becomes possible.

[Brief description of drawings]

FIG. 1 is a block diagram of a coordinate input device adopting the present invention,
2 is a block diagram of the waveform detection circuit of FIG. 1, FIG. 3 is a block diagram of the vibration period measuring circuit of FIG. 1, FIG. 4 is a block diagram of a conventional ultrasonic coordinate input device, and FIG. Is a waveform diagram showing a driving waveform and a detection waveform, and FIG. 6 is an explanatory diagram showing a distance relationship between a pen and a sensor. 100 to 102 …… Preamplifier circuit 105, 108, 111 …… Vibration waveform detection circuit 103, 106, 109 …… Vibration period measurement circuit 116 …… Control circuit 117 …… Oscillator drive circuit 118 …… Vibration pen 122… … Vibration transmission plate 123 …… Sensor

Claims (1)

[Claims] 1. A coordinate input device for detecting vibrations input from a vibrating pen by a plurality of vibration sensors provided on the vibration transmitting plate to detect coordinates of the vibrating pen on the vibration transmitting plate. Transmission time measuring means for measuring the transmission time of the vibration transmitted to the vibration transmission plate, cycle measuring means for measuring the cycle from the time interval of the zero cross points of the vibration transmitted to the vibration transmission plate, the transmission time measuring means and the cycle A coordinate input device comprising: deriving means for deriving the coordinates of a vibration input point of the vibration pen on the vibration transmission plate, using the vibration transmission time and period measured by the measuring means.