JPS5949610B2 - coordinate input device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a coordinate input device, and particularly to a five-type coordinate input device in which the delay time of transmission and reception of surface acoustic waves and coordinates are in one-to-one correspondence.

Conventionally, this type of coordinate input device is based on the principle that the surface acoustic wave transducer uses both transmission and reception to receive reflected waves from a contact object, so there are several problems caused by the signal transmission and reception method. There is.

In other words, in order for the reflected waves of the surface waves and the piezoelectrically converted electrical signals to have good quality, high resolution, and a wide effective die surface, there should be little interaction between the driving signal and the received signal. The S/N ratio of the received signal must be high, and if this is to be achieved at least electrically and acoustically, very complex electrical circuits and acoustic means must be used.

In conventional technology, in order to obtain high quality, especially a good VN ratio of the received signal, the signal level of the received signal is sufficient compared to noise components such as ringing noise or white noise during transmission. Although it must be large, the reflectance of the contacting object is not large enough, and the level of the effective received signal component detected by the surface acoustic wave transducer is reduced due to angular dispersion due to the shape of the contacting object. However, since the loss increases, if the noise component is limited to white noise, it is necessary to increase the signal level.

At present, the conversion efficiency of surface acoustic wave transducers is several tens of percent, and the attenuation rate of propagation media is approximately 0.6 for a driving frequency of 4 MHz for non-piezoelectric materials such as glass.
neper/inch attenuation rate, the angular dispersion of the reflected wave based on the shape of the surface of the contacting object, and the distance-dependent loss of the effective signal received by the surface acoustic wave transducer;
The loss depending on the reflectance is very large. As a countermeasure, surface acoustic wave transducers must be made of materials and structures with large electromechanical coupling coefficients.
caandUltrasonics3Vol, SU-2
2, Haruka 6, pp. 415-420 (1975), etc., the machining accuracy of the wedge angle, the adhesive material, and the bonding method are extremely complicated and difficult in the wedge-shaped surface acoustic wave transducer, etc. For example, on the surface of a piezoelectric material or as a propagation medium, for example, the Acoustical Society of Japan, Vol. 30, No. 10, P.
541-548 (1974), the shape, precision, and
It is difficult to obtain a highly efficient, low-cost surface acoustic wave transducer due to difficulties in the manufacturing method. Regarding the propagation medium, it is difficult to satisfy all the requirements such as having a small surface unevenness, low attenuation in the propagation path, good stability against temperature, good reproducibility of the material, and low cost. be. The problem of the shape and reflectance of the contact surface of a contacting object depends on the surface condition of the contact surface at the time of contact, and depends on the selection of materials, selection of the optimal shape, and contact method, etc., and many improvements have been made. However, even if it were possible, it would have the disadvantage of reducing the degree of freedom in selecting the contact object and the contact method.
Therefore, the method of improving the S/N ratio by increasing the signal level cannot be said to be a good method, so instead we devised a method of reducing the white noise component by band limiting etc. without increasing the signal level. Even so, problems such as a decrease in the frequency of the drive signal and a decrease in resolution occur, so it cannot be said to be an effective means. Next, when considering the noise component as a component due to linking, it is possible to improve the S/N ratio by increasing the signal level, but even if it is improved, the amount is small and D1 is essentially This cannot be dismissed as a significant improvement. Normally, this type of problem is solved by limiting the band or adding a matching circuit, but the above-mentioned resolution problem occurs with the band limiting method, so it is necessary to improve the resolution using a matching circuit, etc. However, it requires a circuit that shapes the drive waveform using a filter or the like and allows only a predetermined frequency component to pass, which has the disadvantage of complicating the circuit. Next, in terms of resolution, a 6-wedge type surface acoustic wave transducer requires a high excitation frequency.

It is necessary to improve the machining accuracy of the wedge angle, which causes problems in machining. . In the case of zero blind electrodes, it depends on the pitch, electrode width, material, etc., and the higher the frequency, the more highly accurate pattern manufacturing means will be required. Furthermore, in order to widen the effective digitizing area, the duration of ringing during transmission must be shortened, and a method similar to the ringing prevention measures described above must be taken, which is a difficult problem.

In any case, in order to obtain a coordinate input device with good quality, high resolution, and a wide effective digitizing surface by receiving reflected waves, it is necessary to use a surface acoustic wave transducer, its drive circuit, propagation medium, contact medium, etc. It is necessary to improve the characteristics of each related component,9 and it becomes necessary to use more advanced technology and a more complicated structure. Therefore, it is an object of the present invention to solve the problems of the conventional methods such as the method described above, and to solve the problem of the received signal due to the combined use of a surface acoustic wave transducer for transmitting and receiving in order to receive reflected waves. It is an object of the present invention to provide a coordinate input device that prevents or eliminates a drop in level, has good quality, high resolution, and has a wide effective digitizing surface.

According to the present invention, a surface wave having a predetermined period excited by a surface acoustic wave transducer (hereinafter referred to as a transducer) is transmitted to a predetermined propagation path of a propagation medium, and an arbitrary point on the propagation path is transmitted. In a coordinate input device of the type that detects a change in the surface wave caused by contacting a contact object with the surface wave and correlates a transmission/reception delay time with a coordinate point, a transmitting transducer and a receiving transducer are connected to the propagation medium. and has means for detecting the time of contact of the contact object on or near the surface of the propagation path, the contact time and the detection time of a change in the surface wave detected by the receiving transducer. The above objective can be achieved by counting the delay time between b and b.

Next, while referring to the drawings regarding the present invention, the configuration, structure,
Detailed explanation of effects, operations, and effects.

Note that the matching circuit and the like are not shown in the drawings because it is sufficient to use conventional techniques and there is no need for special explanation of b1. FIG. 1 is a diagram showing a first embodiment of the present invention.

In the figure, a transmitting transducer 101 and a receiving transducer (+). 102 are disposed facing each other at a predetermined position and attitude on the surface of a propagation medium 106 having means 105 for detecting the point of contact of the contact object 103.

The coordinate input method involves exciting the transmitting transducer 101 from the drive circuit 109 via the lead wire 110 at a period corresponding to a predetermined resolution, and transmitting a surface wave 111 to the surface of the propagation medium 106. B. When the contact object 103 contacts any point on the propagation path of the surface wave 111, the receiving transducer 102
Received waves? Since the signal level of the surface wave 111 is weak, that is, the intensity of the surface wave 111 changes, the signal 116 from the detection means 105 at the time of contact of the contact object 103 is detected,
The counter 117 for measuring the delay time is operated, and the reception lead wire 118 detects a signal 119 in which the intensity of the surface wave 111 that exists between the required input coordinate point and the reception transducer 102 does not change at the time of contact. The delay time is counted and the delay time output signal 121 is inputted to the counter 117 via the circuit system 120.
is the coordinate signal 123 from the correspondence system 122 between delay time and coordinates.
is outputting. Note that the detection means 105 at the time of contact of the contact object 103 may be any method as long as it has a response speed that does not reduce the resolution.
Optical methods, methods using microwaves, etc. are applicable.

Furthermore, if the detection means 105 is in close contact with the propagation medium 106 and is sufficiently thin so as not to reveal the properties of the surface wave 111, the transmitting transducer 101 and the receiving transducer 102 are 105.

As is clear from the above explanation with reference to FIG. 1, the use of the surface acoustic wave transducer for transmission and reception is avoided, and the transmission transducer 101 and the reception transducer 102 are separated. By doing so, it is possible to avoid noise such as white noise or ringing noise that depends on the level difference between the transmitting and receiving signals due to the low efficiency of the entire system from directly affecting the receiving system, and the S/N is
An improvement in the ratio is made.

In addition, since there is no need to receive the reflection from the contact object 103 as in the conventional case, a decrease in the received signal component received by the surface acoustic wave transducer due to angular dispersion, reflectance, etc. of the reflected wave can be avoided. , the level of the received signal is high, so
It has the advantage that signal processing can be done very easily. Therefore, as a result, it is possible to easily obtain a coordinate input device of good quality, high resolution, and a wide effective digitizing surface. FIG. 2 illustrates a second embodiment of the invention.

In this embodiment, a plurality of transmitting transducers 101 and receiving transducers 102 in the first embodiment are arrayed, and a transmitting transducer group 101' and a receiving transducer group 102' are connected to a propagation medium 106. The transmitting transducer groups 10V are arranged facing each other in the same direction on the plane, and the lead wire group 110' is connected to the drive circuit group 1.
09', receiving transducer group 102'
1 and 2 show how they are connected to a detection circuit system group 120' via a reception lead wire group 102', respectively.

According to this embodiment, since a plurality of points are arranged in the arraying direction, it is possible to compensate for the disadvantage that the number of input coordinate points 112 due to one propagation path is small as in the first embodiment, and furthermore, There is an advantage that coordinate signals 123 in a direction perpendicular to the direction of array formation can also be extracted by scanning the arrayed transmitting transducers at predetermined time intervals.

The configuration of other parts, operating principles, functions, effects, etc. other than this embodiment are the same as those of the first embodiment, so explanations thereof will be omitted. FIG. 3 illustrates a third embodiment of the invention.

In this embodiment, a plurality of transmitting transducers 101 and receiving transducers 102 in the first embodiment are arrayed, and a transmitting transducer group 10V1 and a receiving transducer group 10γ are arranged on the surface of the propagation medium 106. The Y-direction transmitting transducer group 101'' and the Y-direction receiving transducer group 1 are arranged facing each other in the same direction.
02'' are similarly arranged, and the lead wire group 110' of the transmission transducer group 101' is connected to the drive circuit group 1.
09', and the Y-direction transducer group 101''
The Y-direction lead wire group 110I is connected to the Y-direction drive circuit group 109I, and the receiving transducer group 10
2' are connected to the detection circuit group 120' via the receiving lead wire group 102', and the Y-direction receiving transducer group 102'' is connected to the Y-direction receiving lead wire group 1, respectively.
18/! It is connected to the Y-direction detection circuit group 120'' through
7', and a Y-direction delay time output signal 121" and a Y-direction coordinate code 123" are output from a Y-direction coordinate correspondence system 122".

According to this embodiment, in the method of the second embodiment, the contact object 1
This solves the problem of poor resolution in the Y direction due to diffraction of the surface wave 111 from 03.

The configuration of other parts, operating principles, functions, effects, etc. other than this embodiment are the same as those of the first embodiment, so explanations thereof will be omitted. The first to third embodiments of the present invention have been described above, but any limitation that is characterized by the basic operating principle, operation, and effect of the present invention. It is clear that the present invention can also be applied to coordinate input devices.

[Brief explanation of the drawing]

FIG. 1 shows a first embodiment of the present invention, and FIG. 2 shows a second embodiment of the present invention.
FIG. 3 shows a third embodiment of the present invention. In each figure, 101 is a transmitting transducer;
2 is a receiving transducer, 103 is a contact object, 10
5 is a detection means, 106 is a propagation medium, 109 is a drive circuit,
110 is a lead wire, 111 is a surface wave, 116 is a signal from the detection means 105, 117 is a counter, 118 is a receiving lead wire, 119 is a signal with no change in intensity, 120 is a detection circuit system, 121 is a delay time output 122 is a correspondence system between delay time and coordinates, 123 is a coordinate signal, 101' is a group of transmitting transducers, 110' is a group of lead wires, 1
09' is a drive circuit group, 102' is a receiving transducer group, 118' is a receiving lead wire group, 12V is a detection circuit group 120', 1011' is a Y-direction transmitting transducer group, 102'' is a transducer group for Y direction transmission. Y-direction receiving transducer group,
110'' is a Y direction lead wire group, 109'' is a Y direction drive circuit group, 118 is a group of cage Y direction receiving lead wires, 120'' is a Y direction
direction detection circuit group, 119 signal with no change in intensity in the cage Y direction, 121 cage Y direction delay time output signal, 122 cage Y direction coordinate correspondence system, 123 // indicates a Y direction coordinate signal.

Claims (1)

[Claims] 1 A surface acoustic wave transducer excites a surface wave having a predetermined period and transmits it to a predetermined propagation path of a propagation medium, and detects a change in the surface wave caused by bringing a contact object into contact with an arbitrary point on the propagation path. In a coordinate input device of a type in which transmission and reception delay times correspond to coordinate points, a transmitting transducer and a receiving transducer are placed facing each other on the propagation medium, and the transmitting transducer and the receiving transducer are arranged facing each other on the propagation medium, and the A coordinate input device comprising means for detecting a contact point of a contact object, and counting a delay time between the contact point and a detection point of a change in the surface wave detected by the receiving transducer.