Abstract:
Described is a sensing device of a surface acoustic wave (SAW) touch panel having a new reflector columns and rows arrangement. As compared to the conventional design in the art where each of the reflector columns and rows are arranged from thinness to thickness, each of the arrangements of the reflector columns and rows herein is composed of a plurality of uniformly disposed reflectors having several sub-reflectors isolated with a gap or gaps. In this manner, a vibration wave transmitted through each of the reflector columns or rows can be reflected and then collected at a target transducer in an uniform pattern with respect to each portion of each of the reflecting columns and rows, thereby avoiding the problem encountered in the prior art.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of Invention 
         [0002]    The present invention relates to a touch panel and particularly to a sensing device of a surface acoustic wave (SAW) touch panel in which the reflector columns and rows are each formed by uniformly arranged reflectors having a gap or gaps therein. 
         [0003]    2. Description of the Related Art 
         [0004]    Surface acoustic wave (SAW) touch panel is a touch panel which determines a touch position thereon by detecting a vibration signal at a target position. Specifically, a transducer having a piezoelectric material therein is utilized to converse an electric signal into the vibration signal and whether the vibration signal is blocked from transmission by a touch at the touch position is judged for the touch position determination by referring to the received vibration signal, generally an output electric signal conversed from the received vibration signal, at the target position of the touch panel. 
         [0005]      FIG. 1A  is a schematic diagram of a structure of a conventional SAW touch panel. As shown in  FIG. 1A , the touch panel  10  comprises a screen area  11  and a reflecting area  12  having a sensing device  13  therein. The sensing device  13  has a first and second X-axis transducers  14   a ,  14   b  and a first and second Y-axis transducers  15   a ,  15   b . The second X-axis and Y-axis transducers  14   b ,  15   b  are used to receive vibration signals Signal_V 1  and Signal_V 2  conversed from input electric signals Signal_Ei 1  and Signal_Ei 2  emitted from the first X-axis and Y-axis transducers  14   a ,  15   a , respectively. In addition, the sensing device  13  also includes a first and second Y-axis reflecting units  16   a ,  16   b  and a first and second X-axis reflecting units  17   a ,  17   b . Each of the first and second X-axis and Y-axis reflecting units  16   a ,  16   b ,  17   a ,  17   b  includes a plurality of reflector r each having the reflecting-in-part and transmitting-in-part characteristic. In this case, the vibration signals Signal V 1  and Signal V 2  required for detecting a touch position P on the X- and Y-axes of the screen area  11  can proceed along each of the first and second X-axis and Y-axis reflecting units  16   a ,  16   b ,  17   a ,  17   b . In general, each of the reflectors r in the first and second X-axis and Y-axis reflecting units  16   a ,  16   b ,  17   a ,  17   b  is a line layer printed on a glass substrate of the touch panel  10  and thus has a low cost. In addition, the reflectors r in the first and second X-axis and Y-axis reflecting units  16   a ,  16   b ,  17   a ,  17   b  are arranged from thinnest to thickness (viewed from the proceeding directions of the vibrations Signal_V 1  and Signal_V 2 , respectively), respectively. This is simply because when the thinness to thickness configuration of the reflecting units  16   a ,  16   b ,  17   a ,  17   b  is absent, the intensity of the vibration signals Signal_V 1  and Signal_V 2 , undesirably becomes smaller as the vibration signals Signal_V 1  and Signal_V 2  proceed longer along a single respective X- or Y-axis reflecting units  16   a ,  16   b ,  17   a ,  17   b , and thus the touch position sensing ability becomes weaker for the touch point P associated with the farer side of the single respective X- or Y-axis reflecting units  16   a ,  16   b ,  17   a ,  17   b . Therefore, the thinness to thickness configuration is provided to each of the reflecting units  16   a ,  16   b ,  17   a ,  17   b  for compensation for this effect.  FIG. 1B  and  FIG. 1C  are waveform plots of Signal_Eo 1  and Signal_Eo 2  when the touch point P exists on and is absent from the SAW touch panel shown in  FIG. 1A , respectively. As shown in  FIG. 1B  and  FIG. 1C , Vy is the waveform of the output electric signal Signal_Eo 1  and corresponds to an X-axis coordinate of the touch point P on the SAW touch panel  10 . On the other hand, Vx is the waveform of the output electric signal Signal_Eo 2  and corresponds to a Y-axis coordinate of the touch point P. It can be seen that the output electric signal Vx has a longer signal span than that of the output electric signal Vy. This is because the vibration signal Signal_V 2  corresponding to the output electric signal Vx experiences a longer path than that of the vibration signal Signal_V 1  corresponding to the output electric signal Vy. In  FIG. 1C , there is a notch on the waveform of the output electric signal Vx and Vy, respectively, with which the touch position P may be determined. In addition, at the beginning of both the output electric signals Vy and Vx, there is a spike, which is resulted from the fact that the vibration signals Signal_V 1  and Signal_V 2  from the input electric signals Signal_Ei 1  and Signal_Ei 2  are directly received by the second X-axis transducer  14   b  and the second Y-axis transducer  15   b  via the second X-axis reflecting unit  17   b  and second Y-axis reflecting unit  16   b.    
         [0006]    However, the SAW touch panel  10  having the thinness to thickness configuration also has its demerits. Owing to the thinner arrangement portion of the reflectors at each of the reflecting units  16   a ,  16   b ,  17   a ,  17   b , the touch position P may sometimes associate with between two neighboring reflectors in a single reflecting units  16   a ,  16   b ,  17   a ,  17   b . In this case, the determination of the touch position P on the SAW touch panel  10  is not ideal enough. 
         [0007]    In this regard, the present invention sets forth a sensing device of a SAW touch panel, which may well overcome the problem encountered in the prior art. 
       SUMMARY OF THE INVENTION 
       [0008]    It is, therefore, an object of the present invention to provide a sensing device of a surface acoustic wave (SAW) touch panel, so as to overcome the problem encountered in the prior art. 
         [0009]    In accordance with an aspect of the present invention, the sensing device of a surface acoustic wave (SAW) touch panel comprises a transparent substrate taking a substantially rectangular shape, having a screen area and a reflecting area, and having a first X-axis and a second X-axis substantially parallel therewith and a first Y-axis and a second Y-axis substantially parallel therewith, the first and second X-axis and Y-axis each having two ends; a first X-axis transducer and a second X-axis transducer disposed at the reflecting area on the two ends of the first X-axis, respectively, and a first Y-axis transducer and a second Y-axis transducer disposed at the reflecting area on the two ends of the first Y-axis, respectively; and a first Y-axis reflecting unit, a second Y-axis reflecting unit, a first X-axis reflecting unit and a second X-axis reflecting unit, disposed on the reflecting area along the first X-axis, the second Y-axis, the first X-axis and the second X-axis, respectively, each of the first and second Y-axis reflecting units including a first number of reflectors and each of the first and second X-axis reflecting units including a second number of reflectors, wherein each reflector of the first and second X-axis and Y-axis reflecting units has a gap or gaps, so as to form a plurality of sub-reflectors therein. 
         [0010]    In an embodiment, wherein the gap between the neighboring sub-reflectors of each reflector of the first and second X-axis and Y-axis reflecting units is dependent upon a material forming the first and second X-axis and Y-axis reflecting units, a relationship among the gaps of the sub-reflectors of the neighboring reflectors of the first and second X-axis and Y-axis reflecting units is also dependent upon the material forming the first and second X-axis and Y-axis reflecting units, and a relationship among the gaps of the sub-reflectors of the reflectors of the first and second X-axis and Y-axis reflecting units is determined by experiment. 
         [0011]    Since the reflectors in the first and second X-axis and Y-axis reflecting units of the sensing area of the SAW touch panel are uniformly arranged, the problem which a touch point can not be effectively sensed on the same touch panel associated with the thinly distributed reflectors can be overcome. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The above and other objects of the present invention will become readily apparent by reference to the following detailed description when considered in conjunction with the accompanying drawings, wherein: 
           [0013]      FIG. 1A  is a schematic structure for illustrating how a touch position made on a conventional surface acoustic wave (SAW) touch panel is detected; 
           [0014]      FIG. 1B  is waveform plots of two output electric signals from the SAW touch panel shown in  FIG. 1A  when no touch input is impinged on the same, respectively; 
           [0015]      FIG. 1C  is waveform plots of two output electric signals from the SAW touch panel shown in  FIG. 1A  when there is a touch input impinged on the same; 
           [0016]      FIG. 2A  is a schematic structure for illustrating how a touch position on a SAW touch panel according to the presenting invention is detected; 
           [0017]      FIG. 2B  is waveform plots of two output electric signals from the SAW touch panel shown in  FIG. 2A  when no touch input is impinged on the same, respectively; and 
           [0018]      FIG. 2C  is waveform plots of two output electric signals from the SAW touch panel shown in  FIG. 2A  when there is a touch input impinged on the same, respectively. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0019]    The present invention is a sensing device of a surface acoustic wave (SAW) touch panel according to the present invention, and will be described taken in the preferred embodiments with reference to the accompanying drawings. 
         [0020]    Referring to  FIG. 2A , which a schematic structure for illustrating how a touch position on a SAW touch panel according to the present invention is detected. As shown, the SAW touch panel  20  is a rectangular device which may be measured with an X-axis and a Y-axis and has a screen area  21  and a reflecting area  22  at which a sensing device  23  is disposed. The sensing device  23  includes a first and second X-axis transducers  24   a  and  24   b  and a first and second Y-axis transducers  25   a  and  25   b . The sensing area  23  further includes a first and second Y-axis reflecting units  26   a  and  26   b  and a first and second X-axis reflecting units  27   a  and  27   b . The first and second Y-axis and X-axis reflecting units  26   a ,  26   a ,  27   a ,  27   b  are vertically or horizontally arranged circumferentially with respect to the screen area  21 . The first and second Y-axis reflecting units  26   a  and  26   b  (also termed as the first and second reflecting columns herein) each includes a first number of reflectors r while the first and second X-axis reflecting units  27   a  and  27   b  (also termed as the first and second reflecting rows herein) each includes a second number of reflectors r. In addition, all the reflectors r each has the transmitting-in-part and reflecting-in-part characteristic and each has a plurality of sub-reflectors r s  each separated from the neighboring one or ones among the plurality of sub-reflectors r s  with a gap g. 
         [0021]    In real operation, an electric signal Signal_Ei 1  is inputted into the first X-axis transducer  24   a  of the SAW touch panel  20 , in which the electric signal Signal_Ei 1  is conversed into a vibration signal Signal_V 1 . The vibration signal Signal_V 1  thus obtained then proceeds along the first Y-axis reflecting unit  26   a  where the vibration signal Signal_V 1  is transmitted in part and reflected in part. The reflected portion of the vibration signal Signal_V 1  is then further reflected by a corresponding reflector r in the second Y-axis reflecting unit  16   b  and finally received by the second X-axis transducer  24   b  after a proceeding path of the reflected vibration signal portion Signal_V 1 , depicted in  FIG. 2A  as A 1 , in which the vibration signal portion Signal_V 1  is conversed into an output electric signal Signal_Eo 1 . Similarly but unconcurrently, an electric signal Signal_Ei 2  is inputted to the SAW touch panel  20  at the first Y-axis transducer  25   a , in which the input electric signal Signal_Ei 2  is conversed into a vibration signal Signal_V 2 . The reflected portion of the vibration signal Signal_V 2  is then further reflected by a corresponding reflector r in the second X-axis reflecting unit  17   b  and finally received by the second Y_axis transducer  25   b  after a proceeding path of the reflected vibration signal portion Signal_V 2 , depicted in  FIG. 2A  as A 2 , in which the vibration signal portion Signal_V 2  is conversed into an output electric signal Signal_Eo 2 . Finally, the output electric signals Signal_Eo 1  and Signal_Eo 2  are relied upon to determine where the touch point P is located on the SAW touch panel  20  by referring to the input electric signals Signal_Ei 1  and Signal_Ei 2 . 
         [0022]    In the above, that the transducers  24   a  and  24   b  are operated at different time from that of the transducers  25   a  and  25   b  is made to prevent the vibration signals Signal_V 1  and Signal_V 2  from interfering with each other. Correspondingly, the first and second input electric signals Signal_Ei 1  and Signal_Ei 2  are supplied alternatively to the first X-axis and Y-axis transducers  24   a  and  25   a . As such, any possible touch position on the SAW touch panel  20  can be continuously detected. 
         [0023]    In addition, the output electric signals Signal_Eo 1  and Signal_Eo 2  above mentioned have the waveforms Vy and Vx shown in  FIG. 2B , respectively. 
         [0024]    When a touch position P appears on and contacts with the screen area  21  of the SAW touch panel  20 , the proceeding paths of the first and vibration signals Signal_V 1  and Signal_V 2  associated with the touch position P are blocked, the first and second output electric signals Signal_V 1  and Signal_V 2  each has a decreased level Vy and Vx, respectively, shown in  FIG. 2C . By referring to the point of time the decreased levels Vy and Vx appears, a coordinate (X, Y) of the touch position P contacted with the screen area  21  of the SAW touch panel  20  can be determined. 
         [0025]    Since the sub-reflectors rs is present, the vibration signals Signal_V 1  and Signal_V 2  which may be reflected by the reflectors r located at a rear part of each of the first and second Y-axis and X-axis reflecting units  26   a ,  26   a ,  27   a ,  27   b  (viewed from the directions that the vibration signals Signal_V 1  and Signal_V 2  outputted from the transducers  24   a  and  25   a , respectively) do not decrease. Namely, the vibration signals Signal_V 1  and Signal_V 2  reflected by the reflectors r located at the rear part of each of the first and second Y-axis and X-axis reflecting units  26   a ,  26   a ,  27   a ,  27   b  (viewed from the same directions) do not decrease is simply because the reflectors r of each of the first and second Y-axis and X-axis reflecting units  26   a ,  26   a ,  27   a ,  27   b  each has the gaps g and the vibration signals Signal_V 1  and Signal_V 2  can better transmit through a fore part of each of the first and second Y-axis and X-axis reflecting units  26   a ,  26   a ,  27   a ,  27   b  to the rear part of the same. 
         [0026]    Furthermore, the neighboring reflectors r of each of the first and second Y-axis and X-axis reflecting units  26   a ,  26   a ,  27   a ,  27   b  may be arranged with an equidistance, such as a separation sep, without losing the ability to detect the touch position P on the SAW touch panel  20 , owing to the provision of the sub-reflectors r s . In this manner, all the possible touch positions P on the SAW touch panel  20  can be located at the proceeding paths of the reflected portions of the vibration signals Signal_V 1  and Signal_V 2 , respectively. Accordingly, any possible touch position P on the SAW touch panel  20  can be well detected, as contrasted to the case in the prior art where some possible touch positions P may appear between the two neighboring proceeding paths A 1  or/and A 2  with a relatively larger separation and thus can not be perfectly detected. 
         [0027]    In a preferred embodiment, the separation sep of each of the neighboring reflectors of the first and second Y-axis and X-axis reflecting units  26   a ,  26   a ,  27   a ,  27   b  is set to be equal. Each of the neighboring sub-reflectors r s  of each of the first and second Y-axis and X-axis reflecting units  26   a ,  26   a ,  27   a ,  27   b  and a relationship of the gaps among each of the sub-reflectors r s  of the reflectors r of the first and second Y-axis and X-axis reflecting units  26   a ,  26   a ,  27   a ,  27   b  are dependent upon a material forming each of the reflectors r. Further, any one of all the gaps g has an optimal relationship with the other gaps of the reflectors r in the first and second Y-axis and X-axis reflecting units  26   a ,  26   a ,  27   a ,  27   b  obtained by experiment. 
         [0028]    In addition, each of the reflectors r has generally the form of a reflecting line layer made of ink. The reflecting line layer is fabricated on a transparent substrate (now shown), like the sensing device  23  by a printing method. In a preferred embodiment, the transparent substrate is a transparent glass substrate. 
         [0029]    In addition, the first and second input electric signals Signal_Ei 1  and Signal_Ei 2  can be supplied by a single external signal source (now shown). At this time, a switch may be provided to switch alternatively the signal external signal source to be the first and second input electric signals Signal_Ei 1  and Signal_Ei 2 . In addition, each of the first and second input electric signals Signal_Ei 1  and Signal_Ei 2  takes the form of a signal consisting of bursts. 
         [0030]    It is readily apparent that the above-described embodiments have the advantage of wide commercial utility. It should be understood that the specific form of the invention hereinabove described is intended to be representative only, as certain modifications within the scope of these teachings will be apparent to those skilled in the art. Accordingly, reference should be made to the following claims in determining the full scope of the invention.