Patent Publication Number: US-2015062058-A1

Title: Touch panel capable of detecting a stylus and a method of using the same

Description:
BACKGROUND OF THE INVENTION  
     1. Field of the Invention 
     The present invention generally relates to a touch panel, and more particularly to a touch panel capable of detecting a stylus. 
     2. Description of Related Art 
     A stylus is an accessory tool that is ordinarily used to assist in navigation when using a touch screen. The stylus tip is normally too small to be sensed by a common touch screen. A specially made stylus or capacitive stylus is therefore required when using a common touch screen. 
     A conventional stylus such as a capacitive stylus, however, requires substantive manufacture process and associated cost. Moreover, the capacitive stylus cannot be easily replaced in case of malfunction, being left behind or circumstances involving loss. 
     For the foregoing reasons, a need has arisen to propose a novel scheme to detect a stylus, particularly a stylus that is not specially made, to provide more convenience for a user using a common touch screen. 
     SUMMARY OF THE INVENTION  
     In view of the foregoing, it is an object of the embodiment of the present invention to provide a touch panel and an associated method capable of detecting a stylus in a manner more effectively and accurately than a conventional touch panel. 
     According to one embodiment, a touch panel capable of detecting a stylus includes a plurality of row electrodes disposed along a first axis, and a plurality of column electrodes disposed along a second axis. Mutual capacitance is at every intersection of each row electrode and each column electrode, and self capacitance is at each row electrode and each column electrode. A voltage is applied to the column electrode or row electrode during a self scan cycle, and the stylus touching on a surface of the touch panel is measured on the same column electrode or row electrode. A voltage is applied to one axis during a mutual scan cycle, and the stylus touching on the surface of the touch panel is measured on the other axis. At least one self scan cycle and at least one mutual scan cycle are performed in each scan frame, and touch identification of the stylus is affirmed when both touch identifications via the self scan cycle and the mutual scan cycle are detected. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         FIG. 1  shows a schematic diagram illustrative of a touch panel according to one embodiment of the present invention; 
         FIG. 2  shows a schematic diagram exemplifying a series of scan frames; 
         FIG. 3A  shows self raw data with respect to a predetermined self touch threshold; 
         FIG. 3B  shows mutual raw data with respect to a predetermined mutual touch threshold; 
         FIG. 4  shows a flow diagram of identifying touch action of a stylus according to one embodiment of the present invention; 
         FIG. 5  shows a flow diagram of relieving touch action of a stylus according to one embodiment of the present invention; and 
         FIG. 6  shows an alternative flow diagram of relieving touch action of a stylus according to another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       FIG. 1  shows a schematic diagram illustrative of a touch panel  100  according to one embodiment of the present invention. The touch panel  100  of the embodiment may be employed in an electronic device, such as a mobile phone. The touch panel  100 , for example, a capacitive touch panel, is composed of row electrodes  11  and column electrodes  12 . There is mutual capacitance C m  at every intersection of each row electrode  11  and each column electrode  12 ; and there is self capacitance C s  at each row electrode  11  and each column electrode  12 . The touch panel  100  of the embodiment is capable of detecting a stylus to perform an associated function in a manner more effectively and accurately than a conventional touch panel. The stylus mentioned in the embodiment may be referred to a general stylus that need not be a specifically made or tailor-made capacitive stylus. 
     Still referring to  FIG. 1 , regarding the self capacitance C s , a voltage may be applied to the column electrode  12  or row electrode  11  during a self scan cycle, and a stylus touching on a front (or touch) surface of the touch panel  100  may thus be measured on the same column electrode  12  or row electrode  11  by a detect circuit (not shown). Regarding the mutual capacitance C m , a voltage may be applied to one axis (e.g., a column electrode  12 ) during a mutual scan cycle, and the stylus touching on the front surface of the touch panel  100  may thus be measured on the other axis (e.g., a row electrode  11 ) by the detect circuit. 
       FIG. 2  shows a schematic diagram exemplifying a series of scan (or measurement) frames. According to one aspect of the embodiment, self raw data (associated with the self capacitance C s ) of a plurality of preceding scan frames (e.g., 10 scan frames as exemplified in  FIG. 2 ) may be accumulated. As intensity of the self raw data is commonly weak while detecting a stylus, the accumulation of the self raw data of the scan frames may thus enhance touch sensitivity. 
     According to another aspect of the embodiment, still referring to  FIG. 2 , a plurality of same self scan cycles (e.g., two self scan cycles as exemplified in  FIG. 2 ) may be performed in each scan frame, and self raw data of the self scan cycles are then added. Accordingly, the added self raw data of the self scan cycles may capably enhance detecting sensitivity of the touch panel  100 . 
     According to a further aspect of the embodiment, still referring to  FIG. 2 , in addition to one or more self scan cycles performed in each scan frame, at least one mutual scan cycle is also performed in each scan frame as exemplified in  FIG. 2 . Mutual raw data (associated with the mutual capacitance C m ) of the performed mutual scan cycle may be utilized to affirm the touch identification of a stylus touching on a surface of the touch panel  100 . For example, in the embodiment, touch identification may be affirmed only when both touch identifications via the self scan cycle(s) and the mutual scan cycle(s) are detected. That is, in the embodiment, failure of either self scan cycle(s) or mutual scan cycle(s) defeats the touch identification. The performances of both the self scan cycle(s) and the mutual scan cycle(s) may be used to resist influence on the touch panel  100  due to environment change. 
     In the embodiment, regarding the self capacitance C s , the touch identification is detected when self raw data (of one or more self scan cycles in a scan frame) is greater than a predetermined self touch threshold TH s  as illustrated in  FIG. 3A . Regarding the mutual capacitance C m , the touch identification is detected when mutual raw data (of at least one scan cycle in a scan frame) is greater than a predetermined mutual touch threshold TH m  as illustrated in  FIG. 3B . 
       FIG. 4  shows a flow diagram of identifying touch action of a stylus according to one embodiment of the present invention. In step  41 , self raw data associated with the self capacitance C s  (of one or more self scan cycles in a scan frame) is compared with the self touch threshold TH s . If the result of step  41  is negative (i.e., the self raw data is not greater than TH s ), the touch action is ignored (step  42 ). Otherwise, the flow goes to step  43 , in which the mutual raw data (in a scan frame) is compared with the mutual touch threshold TH m . If the result of step  43  is negative (i.e., the mutual raw data is not greater than TH m ), the touch action is ignored (step  44 ); otherwise, in step  45 , a count value is incremented. When the count value is not greater than a predetermined set value (a No branch of step  46 ), the flow goes back to step  41  for processing a succeeding scan frame. When the count value exceeds the predetermined set value (a Yes branch of step  46 ), a touch action is thus identified and the touch panel  100  enters into a stylus mode (step  47 ). As exemplified in  FIG. 3A  or  FIG. 3B , the use of the count value in companion with the set value may prevent false touch identification due to spurious raw data. In the embodiment, according to the flow of  FIG. 4 , touch action is affirmatively identified only when the raw data becomes stable, that is, a predetermined times of larger-than-touch-threshold raw data has been met. After entering the stylus mode (alternatively speaking, exiting from a finger mode), some parameters may be adjusted. For example, the predetermined times of larger-than-touch-threshold raw data may be increased to enhance accuracy of touch identification. Moreover, in the stylus mode, algorithm may be restricted to single-touch identification instead of multi-touch identification in the finger mode. 
       FIG. 5  shows a flow diagram of relieving touch action of a stylus (exiting from a stylus mode) according to one embodiment of the present invention. In step  51 , self raw data associated with the self capacitance C s  (of one or more self scan cycles in a scan frame) is compared with the self touch threshold TH s . If the self raw data is not less than TH s , the self raw data is ignored (step  52 ). Otherwise, the flow goes to step  53 , in which the mutual raw data (in a scan frame) is compared with the mutual touch threshold TH m . If the mutual raw data is not less than TH m , the mutual raw data is ignored (step  54 ); otherwise, in step  55 , a count value is incremented. When the count value is not greater than a predetermined set value (a No branch of step  56 ), the flow goes back to step  51  for processing a succeeding scan frame. When the count value exceeds the predetermined set value (a Yes branch of step  56 ), a touch action of a stylus is thus relieved and the touch panel  100  leaves the stylus mode (step  57 ). As exemplified in  FIG. 3A  or  FIG. 3B , the use of the count value in companion with the set value may prevent false touch action relief due to spurious raw data. In the embodiment, according to the flow of  FIG. 5 , touch action is affirmatively relieved only when the raw data becomes stable, that is, a predetermined times of less-than-touch-threshold raw data has been met. 
       FIG. 6  shows an alternative flow diagram of relieving touch action of a stylus (exiting from a stylus mode) according to another embodiment of the present invention. In step  61 , mutual raw data (in a scan frame) associated with the mutual capacitance C m  is compared with a mutual threshold TH for finger touch in the finger mode. It is noted that the mutual threshold TH for finger touch may usually be greater than the mutual touch threshold TH m  for stylus touch in the stylus mode. If the mutual raw data is not greater than TH, the mutual raw data is ignored (step  62 ). Otherwise, if the mutual raw data is greater than TH, indicating a finger may probably touch the touch panel  100 , a touch action of a stylus is thus relieved and the touch panel  100  leaves the stylus mode (step  63 ). 
     Although specific embodiments have been illustrated and described, it will be appreciated by those skilled in the art that various modifications may be made without departing from the scope of the present invention, which is intended to be limited solely by the appended claims.