SEO, Yong Woon (601-106 Jugong Apt, Byeoryang-dong Gwacheon-si, Gyeonggi-do 427-708, KR)
JEONG, Heui Seob (202 ArtVill, 965-32 Bangbae 2-dong Seocho-gu, iSeoul 137-846, KR)
SEO, Yong Woon (601-106 Jugong Apt, Byeoryang-dong Gwacheon-si, Gyeonggi-do 427-708, KR)
[CLAIMS]
[Claim l]
A touch screen using multiplexed Surface Acoustic Waves (SAWs) , comprising: a substrate made of a medium through which SAWs can be propagated; a first SAW Interdigital Transducer (IDT) array, arranged on one edge of the substrate to generate SAWs having different center frequencies; and a second SAW IDT array, arranged on an opposite edge of the substrate to receive the SAWs generated by the first SAW IDT array, wherein the touch screen is constructed so that the SAWs generated by the first SAW IDT array are respectively received by the second SAW IDT array through the medium of the substrate.
[Claim 2]
The touch screen according to claim 1, wherein the first SAW IDT array for generating the SAWs is arranged on two edges of the substrate, and the second SAW IDT array for receiving the SAWs is arranged to be opposite the first
SAW IDT array.
[Claim 3]
The touch screen according to claim 1 or 2, wherein the first SAW IDT array comprises a plurality of SAW IDTs designed to have different center frequencies, and the second SAW IDT array comprises a plurality of SAW IDTs designed to have center frequencies identical to those of respective SAW IDTs constituting the first SAW IDT array, thus detecting a location of a touch depending on frequency characteristics of the SAWs received by the second SAW IDT array.
[Claim 4] The touch screen according to claim 1, further comprising: a first frequency generator for applying operation timing signals having predetermined delay times to respective SAW IDTs, constituting the first SAW IDT array, the first frequency generator being connected to respective
SAW IDTs of the first SAW IDT array; and a second frequency generator for applying operation timing signals having delay times corresponding to the operation timing signals of the first frequency generator to respective SAW IDTs, constituting the second SAW IDT array, the second frequency generator being connected to respective SAW IDTs of the second SAW IDT array, and wherein the touch screen detects a location of a touch and intensity of pressure depending on time and frequency characteristics of the SAWs received by the second SAW IDT array.
[Claim 5]
The touch screen according to claim 1 or 2, further comprising a SAW absorber attached to edges of the substrate, on which electrodes of the plurality of SAW IDTs are arranged, as a structure for suppressing reflection of
SAWs.
[Claim β]
The touch screen according to claim 5, wherein the SAW absorber is implemented using an insulator to apply signals to input electrodes of the SAW IDTs .
[Claim 7]
A method of implementing a touch screen using Surface Acoustic Waves (SAWs) on a substrate made of a medium through which SAWs can be propagated, comprising: a first step of constructing a first SAW IDT array using a plurality of SAW Interdigital Transducers (IDTs) designed to have different center frequencies, and constructing a second SAW IDT array using a plurality of SAW IDTs designed to have center frequencies identical to those of the SAW IDTs, constituting the first SAW IDT array; a second step of arranging the first SAW IDT array and the second SAW IDT array on edges of the substrate so that they are arranged to be laterally or vertically opposite each other on the touch screen; a third step of connecting the SAW IDTs, constituting the first SAW IDT array, to a first frequency generator for individually providing operation timing signals to the SAW IDTs of the first SAW IDT array, and connecting the SAW IDTs, constituting the second SAW IDT array, to a second frequency generator for individually providing operation timing signals, corresponding to the operation timing signals of the first frequency generator, to the SAW IDTs of the second SAW IDT array; and a fourth step of the first SAW IDT array differently allocating frequencies to respective locations on the screen by driving the two frequency generators, thus generating SAWs, and the second SAW IDT array individually receiving the SAWs having frequency characteristics identical to those of the generated SAWs, thus obtaining an output signal required to detect a location of a touch and intensity of pressure.
[Claim 8]
The method according to claim 7, wherein: the third step is performed such that the first frequency generator for providing the operation timing signals, which are sequentially delayed by a predetermined time, is connected to respective SAW IDTs constituting the first SAW IDT array, and the second frequency generator for providing the operation timing signals corresponding to those of the first frequency generator is connected to respective SAW IDTs constituting the second SAW IDT array; and the fourth step is performed such that the first SAW IDT array differently allocates time-varying frequencies to respective locations on the touch screen by driving the two frequency generators, thus generating SAWs, and such that the second SAW IDT array individually receives the SAWs having the time-varying frequencies, thus obtaining an output signal required to detect a location of a touch and intensity of pressure. |
[DESCRIPTION]
[invention Title]
TOUCH SCREEN USING MULTIPLEX SURFACE ACOUSTIC WAVES AND ITS EMBODIMENT METHOD
[Technical Field]
The present invention relates, in general, to a pressure recognition touch screen using multiplexed surface acoustic waves and, more particularly, to a touch screen using surface acoustic waves and a method of implementing the touch screen, in which Interdigital Transducers (IDTs) having different frequency characteristics are arranged on the edges of the touch screen using a surface acoustic wave filter, so that location values can be converted into frequency characteristics, and these characteristic values can be analyzed to detect locations on the touch screen, thus enabling a small-sized touch screen to be manufactured, and improving the reliability of the touch screen against noise.
[Background Art] Generally, as shown in FIG. 1, a touch screen using ultrasonic waves is implemented using technology based on the principle in which ultrasonic oscillators 3a and 3b are provided at the corners of a thick glass substrate 1 to
generate ultrasonic waves, and in which a plurality of reflective mirrors 4 is provided in the travel path of the ultrasonic waves to cause the ultrasonic waves to be perpendicularly reflected through the reflective mirrors toward the opposite sides, and thus the ultrasonic waves, which have reached the opposite sides, are perpendicularly reflected again to reach receivers 6a and 6b. Further, the touch screen uses the principles in which the position at which ultrasonic waves are attenuated is detected when a touching object, such as the hand or a pen, intercepts the travel path of ultrasonic waves, and thus the position is converted into a location on the touch screen.
However, such a conventional ultrasonic touch screen is problematic in that, since design technology for reflective mirrors, the location of ultrasonic oscillators, etc. are important factors, a large area is occupied by the reflective mirrors, in that, since a thick glass substrate having a thickness of about 5 mm is used as the glass substrate due to the arrangement for taking the transmission efficiency of ultrasonic oscillators into account, it is difficult to miniaturize the touch screen, and in that, since the glass substrate is too heavy for models of 40 or more inches, the weight thereof becomes a disadvantage.
[Disclosure]
[Technical Problem]
Accordingly, the present invention has been made keeping in mind the above problems occurring in the conventional ultrasonic touch screen, and an object of the present invention is to provide a touch screen using multiplexed surface acoustic waves and a method of implementing the touch screen, which can precisely detect a touched location on the touch screen using multiplexed surface acoustic waves, or surface acoustic waves having time-varying frequencies, thus also precisely detecting the intensity of pressure while realizing the miniaturization of surface acoustic wave oscillators.
[Technical Solution]
In order to accomplish the above object, the present invention provides a touch screen using multiplexed Surface
Acoustic Waves (SAWs), comprising a substrate made of a medium through which SAWs can be propagated, a first SAW
Interdigital Transducer (IDT) array, arranged on one edge of the substrate to generate SAWs having different center frequencies, and a second SAW IDT array, arranged on an opposite edge of the substrate to receive the SAWs generated by the first SAW IDT array, wherein the touch screen is constructed so that the SAWs generated by the first SAW IDT array are respectively received by the second SAW IDT array through the medium of the substrate.
In another embodiment of the present invention, the first SAW IDT array for generating the SAWs may be arranged on two edges of the substrate, and the second SAW IDT array for receiving the SAWs may be arranged to be opposite the first SAW IDT array.
In each embodiment of the present invention, the first SAW IDT array may comprise a plurality of SAW IDTs designed to have different center frequencies, and the second SAW IDT array may comprise a plurality of SAW IDTs designed to have center frequencies identical to those of respective SAW IDTs constituting the first SAW IDT array and designed to form respective pairs with the SAW DTs constituting the first SAW IDT array.
Further, in each of the present invention, a first frequency generator for applying operation timing signals having predetermined delay times is connected to respective SAW IDTs, constituting the first SAW IDT array, and a second frequency generator for applying operation timing signals having delay times corresponding to the operation timing signals of the first frequency generator is connected to respective SAW IDTs, constituting the second SAW IDT array, so that SAWs having time-varying frequencies can be allocated to respective locations on the touch screen. In each embodiment of the present invention, the touch screen may further comprise a SAW absorber attached
to edges of the substrate, on which electrodes of the plurality of SAW IDTs are arranged, as a structure for suppressing reflection of SAWs. In particular, the SAW absorber may be implemented using an insulator to apply signals to input electrodes of the SAW IDTs .
Further, in order to accomplish the above object, the present invention provides a method of implementing a touch screen using Surface Acoustic Waves (SAWs) on a substrate made of a medium through which SAWs can be propagated, comprising a first step of constructing a first SAW IDT array using a plurality of SAW Interdigital Transducers (IDTs) designed to have different center frequencies, and constructing a second SAW IDT array using a plurality of SAW IDTs designed to have center frequencies identical to those of the SAW IDTs, constituting the first SAW IDT array; a second step of arranging the first SAW IDT array and the second SAW IDT array on edges of the substrate so that they are arranged to be laterally or vertically opposite each other on the touch screen; a third step of connecting the SAW IDTs, constituting the first SAW IDT array, to a first frequency generator for individually providing operation timing signals to the SAW IDTs of the first SAW IDT array, and connecting the SAW IDTs, constituting the second SAW IDT array, to a second frequency generator for individually providing operation timing signals, corresponding to the operation timing
signals of the first frequency generator, to the SAW IDTs of the second SAW IDT array; and a fourth step of the first SAW IDT array differently allocating frequencies to respective locations on the screen by driving the two frequency generators, thus generating SAWs, and the second SAW IDT array individually receiving the SAWs having frequency characteristics identical to those of the generated SAWs, thus obtaining an output signal required to detect a location of a touch and intensity of pressure. In another embodiment of the present invention, the third step may be performed such that the first frequency generator for providing the operation timing signals, which are sequentially delayed by a predetermined time, is connected to respective SAW IDTs constituting the first SAW IDT array, and the second frequency generator for providing the operation timing signals corresponding to those of the first frequency generator is connected to respective SAW IDTs constituting the second SAW IDT array, and the fourth step may be performed such that the first SAW IDT array differently allocates time-varying frequencies to respective locations on the touch screen by driving the two frequency generators, thus generating SAWs, and such that the second SAW IDT array individually receives the SAWs having the time-varying frequencies, thus obtaining an output signal required to detect a location of a touch and intensity of pressure.
[Advantageous Effects]
According to the touch screen using surface acoustic waves of the present invention, there is an advantage in that surface acoustic wave oscillators can be easily miniaturized, so that Interdigital Transducers (IDTs) can be designed on a thin substrate, and can thus be applied to a substrate having a thickness of less than lmm.
Further, the present invention can generate surface acoustic waves by differently allocating time-varying frequencies to respective locations, so that the location of a touch can be simultaneously detected both in time and in frequency, thus precisely recognizing the pressure level and thus detecting the intensity of the pressure. Further, the present invention can be satisfactorily applied to small-sized touch screens having a size of 10 inches or less if frequencies are increased and used.
[Description of Drawings]
FIG. 1 is a schematic diagram of a conventional ultrasonic touch screen; FIG. 2 is a plan view showing an embodiment of a touch screen using time-division multiplexed surface acoustic waves according to the present invention;
FIG, 3 is a plan view showing another embodiment of a touch screen using time-division multiplexed surface
acoustic waves according to the present invention;
FIG. 4 is a schematic diagram showing one of the IDT devices constituting first and second surface acoustic wave
IDT arrays used in a touch screen using time-division multiplexed surface acoustic waves according to the present invention; and
FIGS. 5 and 6 are schematic diagrams showing time- varying frequency spectrums, formed when Surface Acoustic Waves (SAWs) , generated by a transmitting IDT, are received by a receiving IDT, in respective embodiments of the present invention.
[Best Mode]
A touch screen using multiplexed Surface Acoustic Waves (SAWs) according to the present invention is constructed so that a first SAW Interdigital Transducer (IDT) array for generating SAWs having different center frequencies is arranged on one of left/right edges or upper/lower edges of the substrate, a second SAW IDT array for receiving the SAWs generated by the first SAW IDT array is arranged on an opposite edge of the substrate, thus allowing the SAWs generated by the first SAW IDT array to be respectively received by the second SAW IDT array through the substrate.
A method of implementing a touch screen using Surface Acoustic Waves (SAWs) according to the present invention is
performed to implement the touch screen on a substrate made of a medium through which SAWs can be propagated, and comprises a first step of constructing a first SAW IDT array using a plurality of SAW Interdigital Transducers (IDTs) designed to have different center frequencies, and constructing a second SAW IDT array using a plurality of SAW IDTs designed to have center frequencies identical to those of the SAW IDTs, constituting the first SAW IDT array; a second step of arranging the first SAW IDT array and the second SAW IDT array on edges of the substrate so that they are arranged to be laterally or vertically opposite each other on the touch screen; a third step of connecting the SAW IDTs, constituting the first SAW IDT array, to a first frequency generator for individually providing operation timing signals to the SAW IDTs of the first SAW IDT array, and connecting the SAW IDTs, constituting the second SAW IDT array, to a second frequency generator for individually providing operation timing signals, corresponding to the operation timing signals of the first frequency generator, to the SAW IDTs of the second SAW IDT array; and a fourth step of the first SAW IDT array differently allocating frequencies to respective locations on the screen by driving the two frequency generators, thus generating SAWs, and the second SAW IDT array individually receiving the SAWs having frequency characteristics identical to those of the
generated SAWs, thus obtaining an output signal required to detect a location of a touch and intensity of pressure.
[Mode for Invention]
Hereinafter, the construction and operation of embodiments of the present invention will be described in detail with reference to the attached drawings .
FIG. 2 is a plan view showing an embodiment of a touch screen using time-division multiplexed Surface Acoustic Waves (SAWs) , to which the present invention is applied, and schematically illustrates a rectangular SAW touch screen formed on a substrate 10 made of a medium capable of propagating SAWs.
As shown in FIG. 2, the SAW touch screen is constructed so that a first SAW Interdigital Transducer (IDT) array 20 for generating SAW signals having different center frequencies is arranged on one of the left/right edges or the upper/lower edges of the substrate (in the drawing, the left edge is shown as an example) , and a second SAW IDT array 30 for receiving the SAW signals generated by the first SAW IDT array 20 is arranged on the opposite edge of the substrate (in the drawing, the right edge is shown as an example) , thus allowing the SAWs generated by the first SAW IDT array to be respectively received by the second SAW IDT array through the substrate. As shown in FIG. 2, the first SAW IDT array 20 is
constructed so that a plurality of SAW IDTs, designed to have different center frequencies fi to f n , is sequentially arranged in a line. The second SAW IDT array 30 is constructed so that a plurality of SAW IDTs designed to have center frequencies identical to those of the IDTs that constitute the first SAW IDT array 20, and designed to form corresponding pairs together with respective SAW IDTs, which constitute the first SAT IDT array, is sequentially arranged in a line. Accordingly, the second SAW IDT array can precisely detect only signals matching the frequency characteristics thereof from the SAW signals transmitted from the first SAW IDT array, thus generating output signals .
Further, respective SAW IDTs, constituting the first SAW IDT array 20, are connected to a first frequency generator 60 for applying operation timing signals having predetermined delay times. Accordingly, the first SAW IDT array 20 allocates time-varying frequencies to respective locations on the touch screen, thus generating SAWs, and transmitting the SAWs to a medium for propagating SAWs (for example, a material forming the substrate, or another material coated on the substrate to improve performance) . Respective SAW IDTs, constituting the second SAW IDT array 30, are connected to a second frequency generator 70 for applying operation timing signals having the delay times corresponding to the those of the first frequency generator
60. Accordingly, the second SAW IDT array 30 is constructed to precisely receive only a signal generated by a transmitting IDT, forming a pair with a given IDT, among the signals generated by respective transmitting IDTs. FIG. 3 is a plan view showing another embodiment of a touch screen using time-division multiplexed SAWs to which the present invention is applied. In FIG. 3, the touch screen is constructed so that first SAW IDT arrays 20 and 21 for generating SAW signals having different center frequencies are respectively arranged on one of the left/right edges and one of the upper/lower edges of a substrate (in the drawing, left and upper edges are shown as an example) , and so that second SAW IDT arrays 30 and 31 for receiving the SAW signals generated by the first SAW IDT arrays 20 and 21 are arranged on the opposite edges of the substrate (in the drawing, the right and lower edges are shown as an example) , thus allowing the SAW signals generated by the first SAW IDT arrays 20 and 21 to be respectively received by the second SAW IDT arrays 30 and 31 through the substrate. Of course, first and second frequency generators 60a and 70a are additionally implemented together with the SAW IDT arrays.
As shown in the embodiments of FIGS. 2 and 3, the present invention is constructed so that an insulator 40, also functioning as an absorber for SAWs, is attached to respective edges of the substrate on which the electrodes
of the plurality of SAW IDTs, constituting the arrays, is arranged. Such an insulator can not only be used as a structure for suppressing the reflection of surface acoustic waves, but also perform an insulating function for applying signals to the input electrodes of the SAW IDTs.
FIG. 4 is a schematic diagram showing one of IDT devices constituting the first and second SAW IDT arrays used in the time-division multiplexed SAW touch screen according to the present invention. In each embodiment of the present invention, the SAW IDTs having, in particular, center frequencies fi to f n , can be designed by the following method.
First, when a center frequency is fo, and the bandwidth of a filter is δF, N = 2af o /δF, a = 0.6 -0.8
Further, the interval between IDT fingers is A = vs/2f 0 , where vs is the speed of a SAW.
Further, the thickness d of each electrode of the IDT fingers is generally half the interval between the fingers, that is, d = A/2.
The length W of a portion in which the IDT fingers
overlap each other is at least W mm
distance between input and the output IDTs, and λ s is the wavelength of a SAW.
Therefore, the length of the IDT L k = Nδ - δ/2 can be set.
The above description relates to design values for a basic IDT structure having a center frequency of fo. Through these principles, various IDTs can be designed for frequency characteristics of fi to f n , used in respective embodiments of the present invention.
FIGS. 5 and 6 are schematic diagrams showing time- varying frequency spectrums formed when SAWs, generated by the transmitting IDTs used respectively in the embodiments of FIGS. 2 and 3 and adapted to vary from fi to f n over time, are received by the receiving IDTs placed on the right sides. As shown in FIG. 5, fi indicates that a leakage SAW (LSAW) is generated, and thus output intensity corresponding to f± is decreased at an output terminal when a finger or pen touches the substrate. The value corresponding to fi is converted into a location.
Further, as shown in FIG. 6, a SAW, which is a Rayleigh wave, is converted into an LSAW according to the intensity of pressure applied to the touch screen and the area of the touch screen, so that variation in intensities ranging from Pi to P k appears. The pressure level can be set depending on the intensity variation. In this case, the
value corresponding to Pi can be set to a threshold value required to recognize a touch.
The SAW touch screen according to the present invention can be implemented using a method performing the following processing steps.
First, in the first step, a first SAW IDT array is constructed using a plurality of SAW IDTs designed to have different center frequencies, and a second SAW IDT array is constructed using a plurality of SAW IDTs designed to have center frequencies identical to those of the SAW IDTs, constituting the first SAW IDT array.
In the second step, the first SAW IDT array and the second SAW IDT array are arranged to be laterally or vertically opposite each other on the touch screen, and are thus arranged on corresponding edges of the substrate.
In the third step, respective SAW IDTs constituting the first SAW IDT array are connected to the first frequency generator for individually providing operation timing signals to the SAW IDTs, and respective SAW IDTs constituting the second SAW IDT array are connected to the second frequency generator for individually providing operation timing signals corresponding to the operation timing signals of the first frequency generator to the SAW IDTs. In the fourth step, the first SAW IDT array allocates different frequencies to respective locations on the touch
screen by driving the two frequency generators, thus generating SAWs. The second SAW IDT array individually receives SAWs having frequency characteristics identical to those of the generated SAWs, thus obtaining an output signal required to detect the location of a touch and the intensity of pressure.
In particular, the third step may include the step of connecting the SAW IDTs constituting the first SAW IDT array, to the first frequency generator for providing operation timing signals, which are sequentially delayed by a predetermined time, and connecting the SAW IDTs constituting the second SAW IDT array, to the second frequency generator for providing operation timing signals corresponding to the operation timing signals of the first frequency generator.
In the fourth step, the first SAW IDT array differently allocates time-varying frequencies to respective locations on the touch screen by driving the two frequency generators, thus generating SAWs. The second SAW IDT array individually receives the SAWs having the time- varying frequencies, thus obtaining an output signal required to detect the location of a touch and the intensity of pressure.
According to the touch screen using the SAWs of the present invention, having the above construction, when a SAW is absorbed due to the touch of a finger or pen, the
signal corresponding to the frequency of the SAW is attenuated, and thus the location of the touch can be calculated. Further, the location between the SAW IDTs, that is, the value between neighboring center frequencies (f x and t 2 , t 2 and £ ■ $, ..., or f n _i and f n ) , can be obtained by calculating the degree of attenuation of the two center frequency outputs and obtaining the intermediate location value therebetween.
Further, unlike the conventional ultrasonic touch screen (ELO touch) , which uses a method of examining the intensities of SAWs according to the difference between the distances of SAWs, that is, time, of detecting the location at which the intensities of the SAWs are attenuated due to the touch, and of analyzing the location on the screen, the present invention generates SAWs by differently allocating time-varying frequencies to respective locations, thus simultaneously detecting the location of the touch both in time and in frequency. Therefore, the present invention is advantageous in that it is robust to noise or the like which may occur due to harmonic waves.
[industrial Applicability]
According to the above-described touch screen using surface acoustic waves of the present invention, there is an advantage in that SAW oscillators can be easily miniaturized, so that IDTs can be designed on a thin
substrate and can be applied to a substrate having a thickness of less than lmm.
Further, the present invention generates surface acoustic waves by differently allocating time-varying frequencies to respective locations, so that the location of a touch can be simultaneously detected both in time and in frequency, thus precisely recognizing a pressure level to detect the intensity of the pressure. Further, the present invention can be sufficiently applied to small- sized touch screens having a size of 10 inches or less if frequencies are increased and used.
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