Patent Publication Number: US-2013234980-A1

Title: Touch Sensing Apparatus and Method

Description:
RELATED APPLICATIONS 
     This application claims priority to Taiwan Patent Application Serial Number 101107506, filed Mar. 6, 2012, which is herein incorporated by reference. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a sensing device and a sensing method. More particularly, the present disclosure relates to a touch sensing apparatus and a touch sensing method. 
     2. Description of Related Art 
     For high technology nowadays, user interfaces of more and more electronic products have already employed touch panels, such that demands for touch sensing apparatuses have increasingly matured. Touch sensing apparatuses have already become the basis of any kind of user interface, and replacing traditional keyboard interface touch sensing interface with touch sensing interface undoubtedly makes the user interface become more intuitional and easier for use. 
     Moreover, one of ordinary skill in the art can use the touch sensing interface to substitute mechanical keys necessary in various applications such as access control, mobile phone, MP3 player, personal computer peripherals, remote controller, etc., and costs for manufacturing products can thus be saved. 
     However, in touch sensing apparatuses, touch sensing panels usually may generate noise such that sensing signals outputted according to touch operations are often interfered, thereby resulting in that following operations based on the sensing signals may have errors. Thus, a touch sensing apparatus which is free from noise interference is necessary. 
     SUMMARY 
     An aspect of the present disclosure is to provide a touch sensing apparatus comprising a touch sensing trace and a signal processing circuit. The touch sensing trace is configured for generating a sensing signal including a noise signal associated with the touch sensing trace, the touch sensing trace comprises a plurality of first electrodes and a plurality of second electrodes, and the first electrodes are interlaced or interleaved with the second electrodes. The signal processing circuit comprises a first input terminal and a second input terminal, the first input terminal is configured for receiving the sensing signal, and the second input terminal is electrically coupled to a reference voltage source for generating a reference voltage signal, in which the second input terminal is selectively coupled to at least one of the first electrodes and the second electrodes, such that the second input terminal synchronously receives the reference voltage signal and the noise signal associated with the touch sensing trace. 
     Another aspect of the present disclosure is to provide a touch sensing apparatus comprising a touch sensing trace and an analog-to-digital converter circuit. The touch sensing trace comprises a sensing array formed by a plurality of first electrodes and a plurality of second electrodes, in which at least one of the first electrodes is driven to couple with at least one of the second electrodes to form a sensing capacitance, the sensing array generates a sensing signal according to variations of the sensing capacitance, and the sensing signal includes a noise signal associated with the touch sensing trace. The analog-to-digital converter circuit comprises a first input terminal and a second input terminal, the first input terminal is configured for receiving the sensing signal, and the second input terminal is configured for receiving a reference voltage signal and selectively coupled to at least one of the first electrodes which are not driven, and at least one of the second electrodes, such that the noise signal associated with the touch sensing trace is superimposed on the reference voltage signal, in which the analog-to-digital converter circuit is configured for differentially processing the sensing signal and the reference voltage signal superimposed with the noise signal. 
     Still another aspect of the present disclosure is to provide a touch sensing method comprising the steps as described below. A sensing signal is generated according to sensing states of a touch sensing trace, in which the sensing signal includes a noise signal, and the noise signal is associated with the touch sensing trace. The noise signal is superimposed on a reference voltage signal. The sensing signal and the reference voltage signal superimposed with the noise signal are differentially processed to generate a differential voltage signal corresponding to the sensing states of the touch sensing trace. 
     It is to be understood that both the foregoing general description and the following detailed description are by examples, and are intended to provide further explanation of the disclosure as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure can be more fully understood by reading the following detailed description of the embodiments, with reference to the accompanying drawings as follows: 
         FIG. 1  is a schematic diagram illustrating a touch sensing apparatus according to one embodiment of the present disclosure; 
         FIG. 2  is a schematic diagram illustrating a touch sensing apparatus according to another embodiment of the present disclosure; and 
         FIG. 3  is a flowchart illustrating a touch sensing method according to one embodiment of the present disclosure. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     In the following description, specific details are presented to provide a thorough understanding of the embodiments of the present disclosure. Persons of ordinary skill in the art will recognize, however, that the present disclosure can be practiced without one or more of the specific details, or in combination with other components. Well-known implementations or operations are not shown or described in detail to avoid obscuring aspects of various embodiments of the present disclosure. 
     The terms used in this specification generally have their ordinary meanings in the art and in the specific context where each term is used. The use of examples anywhere in this specification, including examples of any terms discussed herein, is illustrative only, and in no way limits the scope and meaning of the disclosure or of any exemplified term. Likewise, the present disclosure is not limited to various embodiments given in this specification. 
     As used herein, “around”, “about” or “approximately” shall generally mean within 20 percent, preferably within 10 percent, and more preferably within 5 percent of a given value or range. Numerical quantities given herein are approximate, meaning that the term “around”, “about” or “approximately” can be inferred if not expressly stated, or meaning other approximate values. 
     It will be understood that, although the terms “first,” “second,” etc., may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of the embodiments. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     As used herein, the terms “comprising,” “including,” “having,” “containing,” “involving,” and the like are to be understood to be open-ended, i.e., to mean including but not limited to. 
     Reference throughout the specification to “one embodiment” or “an embodiment” means that a particular feature, structure, implementation, or characteristic described in connection with the embodiment is included in at least one embodiment of the present disclosure. Thus, uses of the phrases “in one embodiment” or “in an embodiment” in various places throughout the specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, implementation, or characteristics may be combined in any suitable manner in one or more embodiments. 
     In the following description and claims, the terms “coupled” and “connected”, along with their derivatives, may be used. In particular embodiments, “connected” and “coupled” may be used to indicate that two or more elements are in direct physical or electrical contact with each other, or may also mean that two or more elements may not be in direct contact with each other. “Coupled” may still be used to indicate that two or more elements cooperate or interact with each other. 
     The terms “in perpendicular to” and “in parallel with” regarding the vibrating directions also include “substantially in perpendicular to” and “substantially in parallel with”, respectively, throughout the specification and the claims of the present application. 
       FIG. 1  is a schematic diagram illustrating a touch sensing apparatus according to one embodiment of the present disclosure. The touch sensing apparatus  100  includes a substrate  108 , a touch sensing trace  110  and a signal processing circuit  120 , in which the substrate  108  further includes a thin film transistor (TFT) liquid crystal panel, an organic light-emitting diode (OLED) panel, an electronic paper panel, a micro electromechanical (MEMS) panel, a glass substrate or a transparent substrate. If the touch sensing trace  110  in the present disclosure is disposed on a glass substrate, the touch sensing apparatus  100  is a touch panel. In addition, the touch sensing trace  110  also may be in a form of a thin film layer to be attached to the TFT liquid crystal panel, the OLED panel, the electronic paper panel or the MEMS panel, and the touch sensing apparatus  100  is an integrated touch panel or OGS (one glass solution) touch panel. Furthermore, the touch sensing trace  110  also may be integrated into display cells of the TFT liquid crystal panel or the OLED panel. 
     The touch sensing trace  110  is electrically coupled to the signal processing circuit  120 . The touch sensing trace  110  includes a plurality of first electrodes  112  and a plurality of second electrodes  114 , and the first electrodes  112  are interlaced or interleaved with the second electrodes  114 . In one embodiment, the first electrodes  112  are in perpendicular to the second electrodes  114  to be interlaced with each other , in which the first electrodes  112  are Y-axis electrodes, and the second electrodes  114  are X-axis electrodes. In another embodiment, the first electrodes  112  and the second electrodes  114  also can be arranged in an interdigital way on a same horizontal plane (not shown). In still another embodiment, the first electrodes  112  and the second electrodes  114  also can be arranged without being perpendicular to each other. Moreover, the touch sensing trace  110  is configured for generating a sensing signal SS corresponding to touch events (i.e., the touch sensing trace  110  is touched or untouched), in which the sensing signal SS includes a noise signal, and the noise signal is associated with the touch sensing trace  110 . The aforementioned disclosure that the noise signal is associated with the touch sensing trace  110  indicates that the touch sensing trace  110  itself has electrical interferences which may exist in conventional devices such that the outputted signal has disturbances and the noise signal is thus generated. However, it is not limited thereto; that is, any factor which is related to the touch sensing trace  110  and results in generating the noise signal is included. 
     In addition, the signal processing circuit  120  includes a first input terminal  122  and a second input terminal  124 , in which the first input terminal  122  is configured for receiving the sensing signal SS generated by the touch sensing trace  110 , the second input terminal  124  is electrically coupled to a reference voltage source  130 , and the reference voltage source  130  is configured for generating a reference voltage signal Vref. Moreover, the second input terminal  124  is selectively coupled to at least one of the first electrodes  112  and the second electrodes  114 , such that the noise signal associated with the touch sensing trace  110  is superimposed on the reference voltage signal Vref, and the second input terminal  124  synchronously receives the reference voltage signal Vref and the noise signal. 
     In one embodiment, the amount or the way of the first electrodes  112  and the second electrodes  114  being coupled to the second input terminal  124  can be modified fixedly or dynamically according to practical needs or designs, and also can be modified dynamically during the touch sensing operation by employing a programmable mechanism according to the touch sensing trace  110  itself and the noise signal associated therewith; however, it is not limited thereto. 
     In one embodiment, the first electrodes  112  are interlaced or interleaved with the second electrodes  114  to form a sensing array, at least one of the first electrodes  112  is driven to couple with at least one of the second electrodes  114  to form a sensing capacitance, and the sensing array generates the sensing signal SS according to variations of the sensing capacitance. 
     In another embodiment, in a sensing state, at least one of the first electrodes  112  is driven (for example, at least one of the first electrodes  112  is driven by driving signals L+ and L− shown in  FIG. 1 ), and at least one of the undriven rest of the first electrodes  112  and at least one of the second electrodes  114  are coupled to the second input terminal  124 . 
     In yet another embodiment, in the sensing state, two of the first electrodes  112  are driven by the driving signals L+ and L− respectively, and the rest of the first electrodes  112  and all of the second electrodes  114  are coupled to the second input terminal  124 . On the other hand, the aforementioned driving signals L+ and L− also can selectively drive the first electrodes  112  through switches (e.g., switches SW as shown in  FIG. 1 ). 
     It is noted that the aforementioned operation of the first electrodes  112  being driven by the driving signals L+ and L− is not performed by fixedly driving specific electrodes but dynamically driving the first electrodes  112 , for example from left to right, with the driving signals L+ and L−. 
     In practice, the signal processing circuit  120  can be an analog-to-digital converter (ADC) circuit which is configured for converting the sensing signal SS generated by the touch sensing trace  110  into a digital data signal for other elements in the touch sensing apparatus  100  to perform related operations accordingly, and users may obtain results produced based on the operations on the touch sensing trace  110 . 
     Furthermore, a voltage level of the reference voltage signal Vref may be set between a level of a power supply voltage and a level of a ground voltage. Moreover, an operation voltage for the signal processing circuit  120  can be the power supply voltage, and the level of the power supply voltage can be about twice the voltage level of the reference voltage signal Vref. 
     In one embodiment, the signal processing circuit  120  is configured for differentially processing the sensing signal SS received by the first input terminal  122  and the reference voltage signal Vref and the noise signal received by the second input terminal  124 . Since the sensing signal SS is generated according to users&#39; touch operations on the touch sensing trace  110 , the sensing signal SS thus also includes the noise signal corresponding to the touch sensing trace  110 . Moreover, the noise signal received by the second input terminal  124  is associated with the touch sensing trace  110 , so when the signal processing circuit  120  differentially processes the sensing signal SS and the reference voltage signal Vref superimposed with the noise signal, the noise signals included in signals received by the first input terminal  122  and the second input terminal  124  can be cancelled (i.e., noise cancellation), such that the digital data signal outputted by the signal processing circuit  120  would not be affected by the noise signal, so as to improve the signal-to-noise ratio (SNR) and to prevent the subsequent circuits from being affected by the noise signal causing false actions. 
       FIG. 2  is a schematic diagram illustrating a touch sensing apparatus according to another embodiment of the present disclosure. As shown in  FIG. 2 , the touch sensing apparatus  200  includes a substrate  208 , a touch sensing trace  210  and a signal processing circuit  220 , in which the substrate  208  includes a thin film transistor (TFT) liquid crystal panel, an organic light-emitting diode (OLED) panel, an electronic paper panel, a micro electromechanical (MEMS) panel, a glass substrate or a transparent substrate, the arrangements of the substrate  208  and the touch sensing trace  210  can be similar to those as mentioned above, and thus they are not further detailed herein. 
     The touch sensing trace  210  is electrically coupled to the signal processing circuit  220 , and the touch sensing trace  210  includes a plurality of first electrodes  212  and a plurality of second electrodes  214 . The arrangement and the operation of the touch sensing trace  210  are similar to the embodiment shown in  FIG. 1 , and thus they are not further detailed herein. 
     In addition, the signal processing circuit  220  may further include a comparator  240 , and the comparator  240  includes a first comparator input  242 , a second comparator input  244  and a comparator output  246 . The first comparator input  242  is configured for receiving the sensing signal SS generated by the touch sensing trace  210 . The second comparator input  244  is electrically coupled to a reference voltage source  230  and selectively coupled to at least one of the first electrodes  212  and the second electrodes  214 , for receiving the reference voltage signal Vref and the noise signal associated with the touch sensing trace  210 . The comparator output  246  is configured for outputting a differential voltage signal DVS. 
     Since the sensing signal SS is generated according to users&#39; touch operations on the touch sensing trace  210 , the sensing signal SS thus also includes the noise signal corresponding to the touch sensing trace  210 . By using the comparator  240  to differentially process the sensing signal SS and the reference voltage signal Vref superimposed with the noise signal, the noise signal included in the sensing signal SS and the noise signal received by the second comparator input  244  can be counterbalanced (or canceled), such that the differential voltage signal DVS outputted by the comparator  240  can be free from being affected by the noise signal, so as to improve the signal-to-noise ratio (SNR) and to prevent the subsequent circuits from being affected by the noise signal causing false actions. 
     Moreover, the signal processing circuit  220  may further include a controller  250 , and the controller  250  is configured for converting the differential voltage signal DVS into the digital data signal to be outputted for other elements in the touch sensing apparatus  200  to perform related operations accordingly. 
     In addition, the signal processing circuit  220  may further include a variable capacitor  260 , in which the variable capacitor  260  is electrically coupled to the first comparator input  242  and the controller  250  and configured to be controlled by the controller  250 . Furthermore, the variable capacitor  260  can have different equivalent capacitances according to the driving signals L+ and L− (i.e., the signals for dynamically driving the first electrodes  212 ) so as to perform capacitive compensation for the first comparator input  242  receiving the sensing signal SS, such that the variation of the sensing capacitance corresponding to the sensing signal SS can be obtained, and the subsequent corresponding digital data signal can be generated accordingly. 
     Moreover, in one embodiment, the reference voltage source  230  can be disposed in the signal processing circuit  220  and electrically coupled to the second comparator input  244 . In another embodiment, the reference voltage source  230  is disposed outside the signal processing circuit  220  and electrically coupled to the second comparator input  244 . 
     Furthermore, as shown in  FIG. 2 , the signal processing circuit  220  can further include a first switch  272  and a second switch  274 , in which the first switch  272  is coupled between the first comparator input  242  and the second comparator input  244 , and the second switch  274  is coupled between the first comparator input  242  and the touch sensing trace  210 . 
     In one embodiment, in an initial state (e.g., the touch sensing apparatus  200  cannot perform touch sensing operations), the first switch  272  turns on to conduct the first comparator input  242  with the second comparator input  244  and the second switch  274  turns off, and in a sensing state (e.g., the touch sensing apparatus  200  can perform touch sensing operations), the first switch  272  turns off and the second switch  274  turns on to conduct the first comparator input  242  with the touch sensing trace  210 . 
     On the other hand, the driving signals L+ and L− also can selectively drive the first electrodes  212  through switches respectively through switches (e.g., switches SW as shown in  FIG. 2 ) and be selectively transmitted to the variable capacitor  260  for operations. 
       FIG. 3  is a flowchart illustrating a touch sensing method according to one embodiment of the present disclosure. The touch sensing method is applicable to the touch sensing apparatuses as shown in  FIG. 1  and  FIG. 2 . For clear descriptions, the touch sensing method in the present embodiment is described in conjunction with the touch sensing apparatus  200  shown in  FIG. 2 , and however, it is not limited thereto. 
     As shown in  FIG. 2  and  FIG. 3 , the sensing signal SS is first generated according to sensing states of the touch sensing trace  210  (Step  301 ), in which the sensing signal SS includes a noise signal, and the noise signal is associated with the touch sensing trace  210 . Then, the noise signal is superimposed on a reference voltage signal Vref (Step  302 ). Thereafter, the sensing signal SS and the reference voltage signal Vref superimposed with the noise signal are differentially processed to generate a differential voltage signal DVS corresponding to the sensing states of the touch sensing trace (Step  303 ), such that the noise signal in the sensing signal SS and the noise signal superimposed with the reference voltage signal Vref can be counterbalanced (or canceled), and the generated differential voltage signal DVS thus can be free from being affected by the noise signal, so as to improve the signal-to-noise ratio (SNR) and to prevent the subsequent circuits from being affected by the noise signal causing false actions. 
     In another embodiment, the operation of differentially processing the sensing signal SS and the reference voltage signal Vref superimposed with the noise signal, as mentioned at the Step  303 , can be performed by a comparator (e.g., the comparator  240  shown in  FIG. 2 ) for comparing the sensing signal SS and the reference voltage signal Vref superimposed with the noise signal. 
     Furthermore, the touch sensing method can further include converting the differential voltage signal DVS into a digital data signal (Step  304 ) (for example, by the controller  250  shown in  FIG. 2 ), such that the digital data signal can be provided for other elements in the touch sensing apparatus  200  to perform related operations accordingly. 
     For the aforementioned embodiments of the present disclosure, in the touch sensing apparatus, the signal processing circuit (e.g., the analog-to-digital converter circuit) is coupled to both of the touch sensing trace and the undriven electrodes therein, and thus the signal processing circuit synchronously receives the corresponding sensing signal generated by the touch sensing trace and the reference voltage signal superimposed with the noise signal and differentially processes the same signals (or further compares the same signals), such that the noise signals can be counterbalanced (or canceled). Therefore, compared to conventional skills, the digital data signal correspondingly outputted by the signal processing circuit in the embodiments of the present disclosure would not be affected by the noise signal, so as to improve the signal-to-noise ratio (SNR) and to prevent the subsequent circuits from being affected by the noise signal causing false actions. 
     The steps are not necessarily recited in the sequence in which the steps are performed. That is, unless the sequence of the steps is expressly indicated, the sequence of the steps is interchangeable, and all or part of the steps may be simultaneously, partially simultaneously, or sequentially performed. 
     As is understood by a person skilled in the art, the foregoing embodiments of the present disclosure are illustrative of the present disclosure rather than limiting of the present disclosure. It is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims, the scope of which should be accorded with the broadest interpretation so as to encompass all such modifications and similar structures.