JPH01126716A - Device for inputting coordinate - Google Patents

Abstract

PURPOSE:To prevent the mixing of a noise, to increase a detecting signal level, to attain transmission in a low impedance condition and to improve an S/N by closely arranging a sensor and a preamplifier in a coordinate input device to detect vibration, which is inputted from a vibrating pen, with the sensor. CONSTITUTION:An arithmetic and control block 1 executes the control of respective blocks and the operation of a coordinate value, etc. A vibrating pen 3, which is composed of a piezoelectric element 4 for vibration generation and a phone 5, generates an elastic wave in a propagating medium 8 to transmits the elastic wave. The elastic wave is detected by a sensor 6 and a signal detecting circuit 9 generates a detecting signal to depend on a delay time. In a display 11, which displays a point to be pen-inputted, and a member 12 to set a propagating body, etc., a preamplifier 13 is arranged and connected to the sensor 6 by the line material of several tens mms around. The output buffer of an emitter follower, etc., is assembled from the preamplifier 13 to a signal waveform detecting circuit 9 and connected with the low impedance.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a coordinate input device that detects a position using ultrasonic waves.

[Conventional technology]

Conventionally, in general, coordinate input devices using ultrasonic waves,
The configuration is such that a sensor is attached to a propagating body, and a long wire is routed from the sensor to a signal waveform product circuit for signal transmission and signal processing.

[Problem that the invention is trying to solve] However,
In the conventional example described above, the impedance of the sensor (P Z 'r) is low near the resonance frequency, and high impedance in other frequency regions, resulting in the following drawbacks.

(1) The input impedance of the preamplifier is generally
Set to high input impedance, thus the sensor (
When connected to PZT), the high impedance area on the sensor side is maintained, so if you route it with a long wire,
This method has disadvantages in that noise easily enters the system, and since the detection signal is a small signal of several mV or less, the signal-to-noise ratio deteriorates, resulting in false detection or decreased accuracy.

(2) When using a signal frequency of several tens of KH2 to several hundred KH2 or more, the wire from the PZT to the preamplifier is generally a wire with ion protection such as a Seared wire for the detection signal. use. Such a wire has the drawback that the gain of the device amplifier must be increased to compensate for the loss caused by stray capacitance, etc., and therefore the S/N ratio deteriorates and the accuracy decreases.

[Means for solving the problem (and effect)] The present invention connects the sensor and the preamplifier with the shortest wire possible, and installs them so that the high impedance part is kept within the minimum range, thereby reducing noise. However, there is almost no loss of the detection signal, there is no false detection, and the propagation delay time can be detected with high accuracy.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a configuration diagram of an embodiment of the present invention.

Reference numeral 1 denotes an arithmetic control block that controls each block and calculates coordinate values and the like.

3 is a pen for generating elastic waves in the propagation medium for transmitting the elastic waves 8, and is composed of a piezoelectric element 4 for generating vibrations and a horn 5 and its support. 2 is a drive circuit for this pen.

6 is a sensor for detecting the elastic wave propagating through the propagation medium 8, and 9 is a sensor for identifying a certain point in the signal obtained by the sensor 8 and detecting a detection signal depending on the delay time. This is a signal detection circuit.

7 is an anti-reflection material that prevents reflection at the end of the propagator 8.

Reference numeral 11 is a display that displays the points input by the pen 3, and 10 is a driving circuit thereof.

Reference numeral 12 denotes a member in which the propagating body 8, display 11, etc. are installed, and a preamplifier 13 of the present invention is installed in this member as shown in FIG.
It is connected with a wire of about 0 mm. Furthermore, preamplifier 1
3 to the signal waveform detection circuit 9, an output buffer such as an emitter follower is built into the preamplifier 13 and connected in a low impedance state.

The operation of each block will be explained step by step below.

FIG. 2 shows 1: a block diagram of the configuration of the arithmetic control section. 1
-1 is a microcomputer. In this example, it has an internal counter, 11 (, OM and RAM).

In this configuration, a reset signal is first sent to the 1-3 delay time measurement counter and the 1-5 detection signal input port, each of which is cleared and enters a state of waiting for input.

Next, a start signal is sent from the microcomputer 1-1 to the drive signal generation circuit 1-2 and the counter 1-3. In response to this start signal, the 1-2 drive signal generation circuit generates a pulse train having a repetition period of 3: the resonance frequency of the in-pen vibrator, and outputs it to the 2: vibrator drive circuit. Further, the 1-3 power counter circuit starts counting with respect to a clock selected from the required resolution.

The pen is driven by this vibrator drive circuit with the signal output from the drive signal generation circuit 1-2, and the elastic waves generated by this are detected by the sensor 6 and the detection circuit 9, and a detection signal is generated. is input to the 1-5 detection signal input port. According to this detection signal, the latch corresponding to each sensor in the 1-4 latch circuit receives the counter value and holds the value.

The determination circuit 1-6 outputs a signal to the microcomputer 1-1 when all the necessary data are available.

The 1-1 microcomputer receives this signal and processes the 1-1 microcomputer.
The data held in the latches in the four latch circuits are sequentially fetched and coordinate values are calculated from this data.

The obtained coordinate values are transferred to an external circuit, such as a display drive circuit or a host computer, via the 1-7I10 port.

If the data set signal from the judgment circuit 1-6 is not output even after the time determined by the circuit delay time - maximum delay time, etc., the microcomputer 1-1 does not perform any calculation and repeats the operation from the reset. I'll return it.

The above-described operations are repeated to determine the coordinates of the indicated point.

FIG. 3 is a configuration diagram of 3: Pen.

In the same configuration, a drive signal outputted from 1: the arithmetic/control unit is amplified to a predetermined voltage by the 2: vibrator drive circuit capable of low impedance driving, and is applied to the 4: vibrator. Ru. The drive signal is electro-mechanically converted by four vibrators (piezoelectric elements in this example), and vibration is excited.
5: Conveyed to the horn. 5: The horn amplifies the vibrations generated by the vibrator, and 8: The horn transmits the vibrations by contacting the propagating body. The vibration frequencies of the four oscillators are selected to be those that can generate plate waves in the eight propagators.

Further, as the vibration mode of the four oscillators, a mode in which the four vibrators mainly vibrate in a direction perpendicular to the eight propagators is selected.

By setting the vibration frequency of the 4: vibrator to the resonance frequency of the 4: vibrator, vibration can be generated more efficiently.

3: Vibrations excited in the 8-propagating body by the pen propagate within the 8-propagating body as elastic waves.

This elastic wave has the advantage that it is less susceptible to surface scratches and obstacles than waves called plate waves or surface waves.

8: The wave propagating within the propagating body reaches the 6: sensor with a time delay depending on the distance.

6: This wave is subjected to mechanical-electrical conversion by a sensor (for example a piezoelectric element) and 9: sent to a signal detection circuit.

FIG. 4 is an explanatory diagram of signals input to the signal detection circuit.

Figure 4-1 shows the drive signal waveform, which consists of several pulses.

Figure 4-2 shows 6: the waveform detected by the sensor,
It lags behind the 4-1 drive signal by an amount 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) and the phase (4-2-2) of the detected waveform changes with respect to the propagation distance. Let the advancing speed of this envelope be the group velocity Vr, and the velocity of the phase be the phase velocity Vp. The coordinates are determined using this group and phase velocity. First, if we focus only on the envelope, its speed is Vt, and when a certain point, for example, the peak of the envelope, is detected, the distance d between the pen and sensor is determined by the delay time t2 (Figure 4-3) d = vr
It is given by tr (1). Similarly,
Also, by finding the distance for other sensors,
The position of the key coordinates can be determined twice.

However, in order to determine coordinate values with higher precision, we also pay attention to the phase. If the delay time of a certain point in the phase, for example, the zero crossing point after passing the peak, is tp, then (4-4,
4-5) d = nλp+vptp (2)
given as. Here, λp is a wavelength and n is an integer.

From equations (1) and (2), the integer n is :[] Integer conversion Here, N is a real number other than 0, and an appropriate value is used.

For example, if N22 is used, n is determined if the envelope detection accuracy is within 10% of the wavelength.

By substituting n found in equation (3) above into equation (2),
The distance between pen sensors can be accurately determined.

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

A T2 detection signal and a Tp detection signal are generated from the signals obtained from the six sensors and sent to the calculation control section.

The signal mechanically-electrically converted by the 6 sensor is amplified by the 5-2 preamplifier circuit, passes through 5-2.5-3, the envelope peak is detected, and from this, 5-4T? A T2 detection signal is output from the signal detection circuit.

Further, a Tp detection signal is outputted from the Tf multiplied signal and the original signal delayed by the 5-7 delay time adjustment circuit by the 5-8 comparator.

A circuit as described above is provided for each sensor, and for n sensors, detection signals of Tf1 to n and Tp1 to n are sent to the 1: arithmetic control section.

In the 1 arithmetic control section, a latch takes in a counter value for each of the TlP1-n and Tp1-n signals.

The microcomputer calculates each sensor based on this value,
The distances d1 to n between the pens are shown in (2) above.

Calculate using formula (3). The number of sensors on the back side is arbitrary, but when three sensors are used as in this embodiment, if they are arranged as shown in FIG. ) is given by and the coordinates can be determined.

By repeating the above operation, coordinate points can be detected in real time.

FIG. 7 shows an embodiment of the invention. Here, 6 is a sensor, 13 is a preamplifier, and 201 is a printed circuit board.

〔Example〕

In the above embodiment, the preamplifier 13 was installed near the sensor 6, but it is also possible to install only a buffer such as an emitter follower near the sensor 6 and connect it to the signal waveform detection circuit with a low output ispidance. Effective against noise.

[Embodiment 3] In the previous embodiment, the signal waveform detection circuit was not installed near the sensor.
,． 5-4.5-5.5-6.

5-7. All circuits for forming detection signal pulses with delay times tg and tp up to 5-8 are installed at the positions of preamplifiers 1 and 3 in FIG. 1 for each sensor, and the arithmetic control circuit 1 and It is also possible to connect only the 120 members, and if there is enough space in the 120 member, the wires to be connected are Also, there is no need to use expensive shielded wires, and inexpensive vinyl wires can be used, making it possible to realize a highly accurate and inexpensive device.

[Example 4] Instead of connecting each circuit installed near the sensor 6 described in Example 1.2.3 with a wire, the circuits were installed on the same board as the sensor 6 as shown in FIG. A similar effect can be obtained by the configuration.

[Embodiment 5] As shown in FIG. 9, a preamplifier 13 is placed near each sensor 6, and other circuit blocks such as 1, 2, 9, and 10 in FIG. 1 are all placed on the same board. Even if configured, similar effects can be obtained.

〔Effect of the invention〕

As explained above, installing a preamplifier near the sensor can reduce the part where noise enters, and by raising the level of the detection signal and transmitting it in a low impedance state, the S/N can be reduced. A highly accurate input device can be realized without deterioration. Furthermore, if only digital signals are transmitted as in the third embodiment, the structure can be configured without the influence of loss of the detection signal due to the wire, and there is an effect that a highly accurate and inexpensive coordinate input device can be realized.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a block diagram of an arithmetic/control unit, FIG. 3 is a pen configuration diagram, and FIG. 4 is an explanatory diagram of detected waveforms. FIG. 5 is a block diagram of a signal detection circuit, FIG. 6 is a diagram explaining coordinate determination, FIG. 7 is a diagram showing an implementation example of the present invention, and FIG. 8 is an implementation example of another embodiment. FIG. 9 is a diagram showing an example of implementation in another embodiment.

Claims (3)

[Claims] (1) A coordinate input device that detects the coordinates of the vibrating pen on the vibration transmission plate by detecting the vibration input from the vibration pen with a vibration sensor provided on the vibration transmission plate, the coordinate input device being adjacent to the sensor support member. A coordinate input device characterized by having a sensor impedance conversion means in a member. (2) The impedance conversion means includes a detection signal amplification means.
The coordinate input device described in item 1). (3) The coordinate input device according to claim (1), wherein the sensor support member, the impedance conversion means, and the amplification means are constructed in the same member.