JPH01124016A - Coordinate input device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a coordinate input device that detects a position using ultrasonic waves.

[Conventional technology]

Conventionally, coordinate input devices using ultrasonic waves (for example,
1-149742) uses a piezoelectric element (No. 1-149742) as a sensor.
PZT) is used, and each sensor has the same characteristics and a detection circuit such as a preamplifier is configured.

[Problem that the invention is trying to solve] However,
In the conventional example described above, each sensor actually has variations depending on the resonance characteristics or the state of the PZT device, and the detection signals are amplified by the preamplifier with a difference in level. Therefore, there were the following drawbacks.

(1) When the pen pressure is detected based on the amplitude level of the detection signal (Japanese Patent Application No. 61-249737), there is a drawback that the pen pressure is erroneously detected, resulting in poor writing quality.

(2) When a signal is detected at a lower level than originally due to variations, etc., the signal-to-noise ratio of the signal deteriorates and the accuracy of the propagation delay time deteriorates.

[Means (and effects) for solving the problem] According to the present invention, by providing a gain adjustment volume (hereinafter referred to as VR) in the preamplifier, detection due to variations between each sensor, etc. The amplitude level difference between the signals is adjusted using VR to eliminate it.

〔Example〕

The present invention will be described below with reference to embodiments.

FIG. 1 is a circuit diagram for each sensor 6 of the preamplifier circuit in the signal waveform detection circuit shown in FIG. The adjustment method is, for example, by inputting the pen 3 at the same distance from each sensor with a certain writing pressure, and adjusting each VR 12 of each sensor 6 while measuring the detected waveform with an oscilloscope etc. to adjust the amplitude level. to make them the same. The VR 12 is not limited to this location as long as the gain can be adjusted.

FIG. 2 is a configuration diagram of an embodiment of the present invention.

1 is a calculation control block that controls each block and calculates coordinate values, etc.

3 is a pen for generating elastic waves in the propagation medium 8 for transmitting the elastic waves, 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 signal that specifies a certain point of the signal obtained from this sensor and generates a detection signal depending on the delay time. It is a detection circuit.

7 is an anti-reflection material for preventing reflection at the end of the propagator 8.

Reference numeral 11 is a display for displaying points input with the pen 3, and reference numeral 10 is a driving circuit thereof.

The operation of each block will be explained below. FIG. 3 is a block diagram of the configuration of the arithmetic control section 1. 1-1
is a microcomputer and in this example has an internal counter, ROM and RAM.

In this configuration, first, a reset signal is sent to the delay time measurement counter 1-3 and the detection signal input port 1-5, 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 drive signal generation circuit 1-2 generates a pulse train having a repetition period of the resonant frequency of the vibrator in the pen 3, and outputs it to the vibrator drive circuit 1-2. Further, the counter circuit 1-3 starts counting with respect to a clock selected from the required resolution.

The pen is driven by the signal output from the drive signal generation circuit 1-2, and the elastic waves generated thereby are transmitted to the sensor 6,
It is detected by the detection circuit 9, and the detection signal is input to the detection signal input ports 1-5. According to 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 determination circuit 1-6 determines that when all necessary data is available,
Outputs a signal to microcomputer 1-1.

The microcomputer 1-1 receives this signal, sequentially takes in the data held in the latches in the latch circuit 1-4, and calculates coordinate values 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 I10 port 1-7. If the data set signal from the determination circuit 1-6 is not output even after the time determined from the circuit delay time, maximum delay time, etc., the microcomputer 1
-1 repeats the operation from the reset without performing any calculation.

The coordinates of the indicated point are determined by repeating the above-mentioned operations. FIG. 4 is a configuration diagram of the pen 3.

In the same configuration, a drive signal output from the arithmetic control section 1 is amplified to a predetermined voltage by a vibrator drive circuit 2 capable of low impedance driving, and is applied to the vibrator 4. The drive signal is electro-mechanically converted by the vibrator 4 (a piezoelectric element in this embodiment), and vibration is excited and transmitted to the horn 5. The horn 5 amplifies the vibrations generated by the vibrator and transmits the vibrations by contacting the propagation body 8.

As the vibration frequency of the vibrator 4, a frequency that can generate a plate wave in the propagation body 8 is selected.

Further, as the vibration mode of the vibrator 4, a mode in which the vibrator 4 mainly vibrates in a direction perpendicular to the propagation body 8 is selected.

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

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

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 waves propagating within the propagation body 8 reach the sensor 6 with a time delay depending on the distance.

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

FIG. 5 is an explanatory diagram of signals input to the signal detection circuit.

4-1 is a drive signal waveform, which consists of several pulses. 4-2 is a waveform detected by the sensor 6;
The drive signal 4-1 is transmitted according 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. The speed at which this envelope advances is defined as group velocity v2, and the velocity of the phase is defined as phase velocity Vp. The coordinates are determined using this group and phase velocity. First, if we focus only on the envelope, its speed is v2, and when a certain point, for example the peak of the envelope, is detected, the distance d between the pen and the sensor is d2V (tt), where the delay time is tt. 1) is given by. Similarly, the position of the pen coordinates can be determined by finding the distance for other sensors.

However, in order to determine highly accurate coordinate values, we also focus on the phase. If the delay time of a certain point in the phase, for example, a zero-crossing point after passing the peak, is tp, then it is given as d=nλp+Vptp (2). Here, λp is a wavelength and n is an integer. From equations (1) and (2), the integer n is: Integerization within [] Here, N is a real number other than 0, and an appropriate numerical value is used.

For example, if N=2, if the envelope detection accuracy is within 10% wavelength, n is determined.

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

FIG. 6 is a block diagram of the signal detection circuit.

The signal obtained from sensor 6 is F)T? Detection signal, Tp
Generates a detection signal and sends it to the arithmetic control section.

The signal mechanically-electrically converted by the sensor 6 is amplified by the preamplifier circuit 5-2, and the envelope peak is detected through the envelope detection circuit 5-2 and the envelope peak detection circuit 5-3, and this is the JTr signal detection circuit. 5-4 to T
1 detection signal is output.

Also, from this T2 signal and the original signal delayed by the delay time adjustment circuit 5-7, the comparator 5-7
8 outputs a Tp detection signal.

Each sensor has a circuit like the one above, and the number of sensors is n.
Tr1-n + Tp1-n detection signals 1: Send to the arithmetic control section.

5-9 fd is a pen pressure detection circuit that sets a threshold for the envelope o signal and sets the level to 0N10FF of the pen pressure.

In the arithmetic control unit 1, latches take in counter values for each of Tg1-n and Tp+-n signals.

The microcomputer calculates each sensor 6 based on this value.
Then, the distances d1 to n between the pens 3 are calculated from the above equations (2) and (3). The number of sensors 6 can be two or more, but when three sensors are used as in this embodiment, if they are arranged as shown in FIG. For P(x, y), it is given by (X, Y is the distance between the sensors), and the coordinates can be determined.

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

[Example 2] The resistor 12 in FIG. 1 is a fixed resistor, and the resistor 13 is set to V.
The present invention can be realized even if the gain can be adjusted as R.

[Embodiment 3] In the embodiment described above, each gain adjustment VR was adjusted to match the level for each sensor 6, but
In principle, all that is required is to match the level relative to each sensor, so for example, if there are three sensors, the gain of one preamplifier is fixed, and the gain of the remaining two preamplifiers is fixed. It is also possible to match the sensitivity of the three sensors by adjusting the gain of the amplifier.

〔Effect of the invention〕

As explained above, by providing a gain adjustment VR in the preamplifier and adjusting it, the poor writing quality affected by erroneous detection of writing pressure, uneven signal level, deterioration of S/N, etc.
This has the effect of preventing deterioration of accuracy and making it possible to construct a high-precision device with good writing quality.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram using the preamplifier gain adjustment circuit shown in Fig. 5; Fig. 2 is a block diagram of an embodiment of the present invention; Fig. 3 is a block diagram of the arithmetic/control section; FIG. 4 is a pen configuration diagram, - FIG. 5 is a detection waveform explanatory diagram, FIG. 6 is a signal detection plane block configuration diagram, and FIG. 7 is a coordinate determination explanatory diagram.

Claims (2)

[Claims] (1) A vibrating pen having a vibration generating means, a propagation member that generates and propagates an elastic wave by bringing the vibrating pen into contact, and a plurality of sensor means attached to the propagation member, and has a propagation delay of the elastic wave. A coordinate input device for determining coordinates based on time, the coordinate input device comprising means for adjusting sensitivity differences between the sensors. (2) The coordinate input device according to claim (1), characterized in that each sensor has its own sensitivity adjustment means.