JPS6041764B2 - coordinate input device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a coordinate input device, and particularly to a coordinate input device of a type that coordinates transforms the amount of delay of an elastic surface wave.

Several coordinate input devices of this type have been proposed in the past.

``wedge''-shaped transducers are placed on the surface of an optically transparent isotropic substrate such as glass; This type of device transmits and receives surface waves using magnetic means or the like on the surface of a substrate on which a surface wave is placed. However, the latter may be caused by optical problems such as the substrate being optically opaque or extremely poor, or manufacturing problems such as difficulty in manufacturing a large effective die die area; Even if this problem were solved, there were cost issues such as extremely high manufacturing costs, making it extremely difficult to put it into practical use. Regarding the former, among the proposals to date, A.M. Halladay: 'A Tatsuchi Sensitive Position Encoder for Computer Input', Full Joint Computer Conference, 1
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The most excellent representative example is the method proposed by N1969). However, it includes many problems. Below, with reference to FIG. 1 and FIGS. 2a and 2b, the problems of the conventional method will be clarified.

Fig. 1 shows an example of the conventional method, Fig. 2 a and b show the piezoelectric plate 1
A conventional drive waveform consisting of a plurality of waveforms that excites 51;
This figure shows a received signal of a reflected wave in a conventional method. In FIG. 1, the electro-mechanical converter D is a ``wedge'' made of acrylic or the like having a different sound velocity than the substrate 102 and having a predetermined angle.
A layer 155 for bonding a piezoelectric plate 151 that vibrates through its thickness on the 150 plane, a layer 106 for bonding the other side of the "wedge" 150 to the surface of the substrate 102, and an absorbing material for removing noise ultrasonic components. 154, a longitudinal wave 152 propagates through the "wedge" 150, is converted into a surface wave 153 on the surface of the substrate 102, propagates on the surface of the substrate 102 as an incident wave 104, and is transmitted to the contact body 107. (
For example, the reflected wave 105 generated by a felt-tip pen, finger, etc.) was received and the amount of delay was counted.
In addition, as shown in Figure 2a, multiple drive waveforms are used to improve energy concentration, and a signal with a nearly constant peak value including noise components as shown in Figure 2b is received. Because this method measures the signal that reaches the comparison circuit fastest via an amplifier circuit or the like as the amount of delay, several problems arise due to the above method and affect the performance of the device. Specifically, the conversion efficiency of the transducer is low, the shortest time is used as the delay amount, so it is susceptible to one-off noise, the drive voltage is high, and the absorption material 154 is used to reduce the influence of longitudinal wave reflection from the substrate. that is necessary,
The problem was that the machining accuracy of the wedge 150 had to be increased in order to increase the resolution.

The first problem is the low conversion efficiency of transducers.
A transducer using a 2° wedge 150 requires at least two adhesive layers. That is, there is a layer 155 that adheres the piezoelectric plate 151 and a layer 106 that adheres the wedge 150 on the substrate 102.The conversion efficiency varies greatly depending on the adhesive strength of the adhesive and the thickness of the adhesive layer. It is not possible to obtain a material with very good adhesive strength, and we will have to wait for future development.Therefore, countermeasures such as making the adhesive layer as thin as possible are necessary, but even if it is made well, it will only be a few μm thick. There is a limit to the extent of the problem, and improvement is extremely difficult.Furthermore, as shown in FIG.
It is a type that utilizes the difference in sound speed with the wedge 150, and is made of inexpensive "wedge" material that has a difference in sound speed with the substrate 102, has relatively good workability, has a small attenuation coefficient, and does not generate unnecessary noise. Although it is necessary to make a selection, no material has been found that fully satisfies the conditions, and acrylic materials have been used as an example. Next, the problem with the detection method that uses the shortest time as the delay amount is that when excited with the driving waveform shown in FIG. The level decreases, and a reflected wave containing many noise components as shown in FIG. 2b is detected. The noise includes a component based on the longitudinal wave 152, a component transmitted near the surface, a component due to an electric circuit system generated during detection, a component due to a power supply line or a ground line, etc., and its appearance is extremely complicated.
The signal received for communication is several tens of μ in the piezoelectric plate 151.
Because the level is low, from ■ to several meters, the power line,
Even a single noise superimposed on a ground line or the like is affected, and the method in which the comparator circuit measures and detects the signal that arrives the fastest as the amount of delay causes malfunctions and requires improvement. Regarding the problem of high drive voltage, ``In the method of converting the longitudinal wave 152 propagating in the wedge 150, or vice versa, only the compression wave formed by the drive signal propagates continuously. Therefore, if you want to make the signal component larger than the noise component, you will have to rely on a method of increasing the drive voltage.
Devices have become complex and inconvenient to handle.

Furthermore, regarding the problem of adding the absorbing material 154, even if an excellent absorbing material with a large absorption coefficient is added to the wedge 150 surface, unnecessary ultrasonic components will be mixed in the transmitted and received signals, and the sufficient effect will not be achieved. The configuration has become complicated.

In addition, regarding the problem of machining accuracy of the wedge 150, in order to generate the surface waves 153 most efficiently, it is necessary to use the wedge 150 near the critical angle determined by the difference in sound speed between the wedge 150 and the substrate 102. If you want to increase the resolution, you need to increase the driving frequency.
Because the angle of the wedge 150 had to be so accurate, machining became difficult.

From the above, it is difficult to obtain a high-quality input device that has high efficiency, can be driven at low voltage, is highly reliable, has a simple configuration, and does not require high processing precision with conventional coordinate input devices. It was extremely difficult.

SUMMARY OF THE INVENTION An object of the present invention is to provide a coordinate input device that improves the above-mentioned drawbacks.

According to the present invention, an optical fiber that travels on an optically transparent substrate surface. A coordinate input device that receives a reflected wave from a specified position by a contacting body during the propagation path of an elastic surface wave, and converts the coordinates of the specified position according to the amount of delay from the time of excitation of the surface wave. , an interdigital transducer consisting of a plurality of pairs arranged on the substrate surface for transmitting and receiving the surface waves, and a received signal of the reflected wave received by the transducer at a predetermined follow-up time. An envelope detector that detects an envelope and a means for extracting the delay amount with respect to the peak value of the detected envelope, which enables high efficiency and low voltage driving and is highly reliable.
A coordinate input device with easy device configuration can be obtained.

Next, the configuration, structure, and operation of the present invention will be explained in detail with reference to the drawings.

The support frame and the like will not be shown explicitly as it is sufficient to use conventional techniques and there is no need for illustration or explanation thereof.
FIG. 3 shows a configuration diagram of a coordinate input device showing the first embodiment. In the figure, interdigital transducers 101 for transmitting and receiving are arranged one-dimensionally in the same direction.
an optically transparent substrate 1 having a surface wave absorber 108;
02 at a predetermined position and orientation via an adhesive layer 106.

The transducer 101 is excited through the lead wire 103, and an incident surface wave 1 is generated on the surface of the substrate 102.
04, and when the contact body 107 is brought into contact with any specified position in the propagation path of the incident wave 104, the reflected wave 105 is received by the transducer 101. The received signal is amplified and switched by the amplification and transmission/reception switching means 158 and outputted as a detection signal 159 . For the detection signal 159, an envelope with a relatively gentle slope is detected in a predetermined follow-up time that does not reduce the resolution and is not affected by one-off steep noises that may cause malfunctions. The delay amount of the detected envelope is detected by the means 160 for detecting the delay amount corresponding to its peak value, and is output as an input coordinate signal 163. In addition,
Interdige as a transducer. Since the adhesive layer 106 is barrel-shaped, it can be efficiently converted into surface waves, so it can be made sufficiently thin using conventional techniques.

The reception of reflected waves 105 may be detected by the same transducer 101 or by others. Figure 4 shows a plurality of pairs of electrodes 135 on the surface of a piezoelectric material with predetermined polarization, which have predetermined intervals and lengths, allowing for the most efficient conversion in accordance with the driving frequency. There is a formal electrode pattern 116, and a predetermined low voltage driving waveform can be applied between the A and B electrodes.

FIG. 5 is a circuit diagram showing an example of means 160 for detecting the amount of delay. When a detection signal 159 that is larger than the previous one is input to an operational amplifier 175 for a voltage follower, it is amplified by the operational amplifier 175, and a diode A capacitor 177 is charged through a capacitor 176, and an output signal 179 is output from an impedance converter 178.

Note that at this time, the output signal 179 is connected to the operational amplifier 175 and the inverting input terminal of the impedance converter 178, and while the diode 176 is conducting, the detection signal 15
9. The charging voltage of the capacitor 177 and the output signal 179 are equal. Next, when a signal smaller than the aforementioned detection signal 159 is input, the diode 176 becomes non-conductive, the aforementioned detection signal 159 is held in the capacitor 177, and a predetermined signal having a time constant larger than the driving frequency is input. The envelope 161 is detected at the follow-up time. The output signal 179 is also input to the peak detector 185 of the envelope 161, and if the output signal 179 does not increase within a predetermined period, it is determined to be the peak value of the envelope 161, and by subtracting a predetermined time, the peak value is detected. A value signal 186 is determined and input to a delay amount calculator 187. The input coordinate signal 163 is output as the delay amount calculator 187 output signal. Further, after detecting the input coordinate signal 163, the reset switch 188 returns to the initial state and the same operation is repeated. FIG. 6a shows a driving waveform applied to the transducer 101, in which a signal consisting of a low voltage having approximately the same peak value on one or more panels is applied.

FIG. 6b shows that when the reflected waves 105 are received by the interdigital transducer 101, they are modulated and the reflected waves 105 have the same phase depending on the arrangement of each comb 135.
are superimposed, a large part of the signal component is generated, and the means 160 for detecting the amount of delay obtains an envelope 161 shown by a dotted line.Furthermore, the time at the center of the drive waveform is taken as the time b at the time of excitation, and the envelope 161 is The figure shows how the delay amount t-ω is output as the input coordinate signal 163 when the time t indicating the peak value of the line 161 is detected.

As is clear from FIGS. 2 to 6 above, this embodiment uses an interdigital transducer 101 in the surface wave transmitting/receiving section, and uses a method to detect the amount of delay corresponding to the peak value of the envelope. The following effects can be obtained from:

In other words, in terms of high efficiency, since only one adhesive layer is required, the loss in the adhesive layer is small, and since the wedge 150 is not required, the loss due to the wedge 150 is eliminated. Furthermore, since the interdigital transducer consists of a plurality of '4 combs' 5135, it undergoes phase modulation during transmission and reception, and the same phase components are superimposed, so even a small signal can be output as a large signal. A great effect can be obtained.As for lower voltage driving, it is clear from the above-mentioned phase modulation relationship, and it has been confirmed that the driving voltage is only a few tens of V compared to the conventional peak voltage of ~150 V. If you want to lower the ゜゛ lottery 135, you can do so by increasing the number of ゜゛ lots 135.As for the structural issues, the ``wedge'' 150 is not required, the longitudinal waves reflected from the substrate 102 and the ゜゛ wedge can be lowered. There is no need for the absorbing material 154 that absorbs the noisy ultrasonic waves from the 150, etc., and since the level of the received signal is high, it is not affected by external noise, which simplifies the circuit configuration. Regarding processing accuracy, it goes without saying that the ゜゜wedge 150 is not used, and the electrode pattern 116 can be made relatively easily with chemical etching, etc. Regarding reliability, in the conventional method, multiple Since the amount of delay is determined by the signal that reaches the fastest among the reflected waves 105, noise caused by the damping ultrasonic waves, noise caused by the constituent circuits, etc.
Due to noise mixed in the power line etc., it was not possible to accurately detect the specified amount of delay, but according to the envelope detection method,
Since the envelope 161 is detected using a predetermined follow-up time having a time constant larger than the driving frequency, problems such as those caused by detecting the delay amount due to white noise or other single unnecessary noise do not occur. . Furthermore, since the peak value signal 186 is obtained by subtraction, it is accurate and has high resolution. Furthermore, since only one adhesive layer is required, there is an effect that the influence of temperature, humidity, etc. is small. Therefore, it is possible to obtain a coordinate input device of high efficiency, low voltage drive, simple configuration, and good quality that does not require high processing precision, and the object of the present invention can be achieved.

FIG. 7 illustrates a second embodiment of the invention.

This example shows that the arrangement of the transducers 101 is two-dimensional. As is clear from FIG. 7, in this embodiment, by arranging the transducers 101 two-dimensionally, two-dimensional coordinate input is possible, and the range of application of the device is widened.

The embodiments of the present invention have been described above, and the efficiency can be improved by changing the electrode arrangement of the transducer and the adhesive surface, as well as a method of encoding it as an electrode pattern, a method of attaching a grating, etc. The substrate is not limited to a flat surface, and may have a curved surface. Furthermore, by using a sampling method, etc., it is possible to sufficiently analogize the detection of the delay amount corresponding to the peak value. It is clear that the present invention can be applied to any coordinate input device having a configuration or structure in which each component is modified as long as the present invention is characterized by the following effects.

[Brief explanation of the drawing]

FIG. 1 is a structural conceptual diagram illustrating an example of a conventional method, FIG. 2 a is a diagram showing a driving waveform, and FIG. 2 b is a diagram showing a received signal waveform.
FIG. 3 is a diagram showing an embodiment of the present invention, FIG. 4 is a diagram showing an electrode pattern of an interdigital transducer, FIG. 5 is an example of means for detecting the amount of delay, and FIG. 6a is a diagram showing a transducer. FIG. 6b shows the envelope and delay amount, and FIG. 7 shows the second embodiment.

Claims (1)

[Claims] 1. During the propagation path of an elastic surface wave traveling on an optically transparent substrate surface, a reflected wave from a specified position by a contact body is received, and the specified position is determined based on the amount of delay from the time of excitation of the surface wave. A coordinate input device of a type that converts a position into coordinates, comprising: an interdigital transducer arranged on the substrate surface and comprising a plurality of pairs for transmitting and receiving the surface waves; and a received signal of the reflected wave received by the transducer. A coordinate input device comprising: means for detecting an envelope at a predetermined follow-up time and detecting the delay amount corresponding to the peak of the detected envelope.