(19) United States
`(12) Patent Application Publication (10) Pub. No.: US 2011/0175835 A1
`Wang
`(43) Pub. Date:
`Jul. 21, 2011
`
`US 2011 0175835A1
`
`(54) METHOD FORSCANNING PROJECTIVE
`CAPACITIVE TOUCH PANEL, STORAGE
`MEDIUMAND APPARATUS FORSCANNING
`PROJECTIVE CAPACTIVE TOUCH PANEL
`
`(75) Inventor:
`
`Wanqiu Wang, Singapore (SG)
`
`(73) Assignee:
`
`TPK TOUCH SOLUTIONS
`(XIAMEN) INC
`
`(21) Appl. No.:
`
`13/009,847
`
`(22) Filed:
`
`Jan. 19, 2011
`
`(30)
`
`Foreign Application Priority Data
`
`Jan. 21, 2010 (CN) ......................... 201010103956.6
`
`
`
`Publication Classification
`
`(51) Int. Cl.
`(2006.01)
`G06F 3/04
`(52) U.S. Cl. ........................................................ 345/173
`(57)
`ABSTRACT
`The present invention relates to a method for Scanning a
`projective capacitive touch panel including: A. Scanning each
`first-axis electrode arranged along a first-axis and each sec
`ond-axis electrode arranged along a second-axis, then obtain
`ing the first-axis electrode and the second-axis electrode
`whose self capacitance changes; B. detecting the mutual
`capacitance at each intersection between the first-axis elec
`trode and the second-axis electrode whose self capacitance
`changes to determine whether the mutual capacitance
`changes, then the area where the mutual capacitance changes
`being taken as a touched area. The present invention also
`relates to a storage medium storing instructions of imple
`menting above method and an apparatus that implements the
`above method.
`
`DELL EXHIBIT 1043 PAGE 1
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`

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`Patent Application Publication
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`Patent Application Publication
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`Jul. 21, 2011 Sheet 2 of 6
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`DELL EXHIBIT 1043 PAGE 3
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`Patent Application Publication
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`Jul. 21, 2011 Sheet 3 of 6
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`DELL EXHIBIT 1043 PAGE 4
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`Patent Application Publication
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`Jul. 21, 2011 Sheet 4 of 6
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`DELL EXHIBIT 1043 PAGE 5
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`Jul. 21, 2011
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`DELL EXHIBIT 1043 PAGE 6
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`Jul. 21, 2011
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`DELL EXHIBIT 1043 PAGE 7
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`

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`US 2011/0175835 A1
`
`Jul. 21, 2011
`
`METHOD FORSCANNING PROJECTIVE
`CAPACITIVE TOUCH PANEL, STORAGE
`MEDUMANDAPPARATUS FORSCANNING
`PROJECTIVE CAPACTIVE TOUCH PANEL
`
`BACKGROUND OF THE INVENTION
`0001. This application claims the benefit of People's
`Republic of China Application No. 201010103956.6, filed on
`Jan. 21, 2010.
`
`FIELD OF THE INVENTION
`0002 The present invention generally relates to a capaci
`tive touch panel, and more particularly, to a method for scan
`ning a projective capacitive touch panel, a storage medium
`and an apparatus for Scanning a projective capacitive touch
`panel.
`
`DESCRIPTION OF THE RELATED ART
`0003 Capacitive touch panels are divided into projective
`capacitive touch panels and Surface capacitive touch panels.
`The projective capacitive touch panel includes two layers of
`conductive electrodes orthogonally placed. One layer of con
`ductive electrodes includes M (M21) first-axis electrodes
`parallelly arranged along a first-axis (electrode X). The other
`layer of conductive electrodes includes N (N21) second-axis
`electrodes parallelly arranged along a second-axis (electrode
`Y).
`0004. A conventional method to determine the position of
`the touch point is to scan all the MXN capacitances based on
`the fact that the position of the intersections in the electrode
`matrix can determine the position on the screen. As the size of
`the touch screen increases, a time period for Scanning the
`electrode matrix becomes longer accordingly for the same
`scanning accuracy. For a 42-inch touch panel, if M is 170, N
`is 100 and the Scanning time of each capacitance is 30 us, the
`time period for scanning the electrode matrix is 170x100x30
`us=0.51s In other words, the scanning frequency is 1/0.51 =1.
`96 Hz. That is a very low scanning frequency, which will
`cause a delay in determining a touch point. If the touch panel
`is a multi-touch panel then the time delay will get worse
`leading to a loss of touch points.
`0005 Thus, it is desired to provide a method for scanning
`a projective capacitive touch panel that overcomes the above
`drawbacks of the conventional scanning method.
`
`SUMMARY OF THE INVENTION
`0006. In one aspect, a method for scanning a projective
`capacitive touch panel is provided including: A. Scanning
`each first-axis electrode arranged along a first-axis and each
`second-axis electrode arranged along a second-axis, then
`obtaining the first-axis electrode and the second-axis elec
`trode whose self capacitance changes; B. detecting the mutual
`capacitance at each intersection between the first-axis elec
`trode and the second-axis electrode which electrodes self
`capacitance changes to determine whether the mutual capaci
`tance changes, then taking an area where the mutual capaci
`tance changes as a touched area. Also provided are storage
`medium for storing instructions of implementing the above
`described method and an apparatus that implements the
`above-described method.
`0007 Thus, by combining detecting self capacitance and
`mutual capacitance, the method of present invention can sig
`
`nificantly reduce the scanning time and boost the scanning
`frequency while the scanning accuracy is also guaranteed in a
`large touch panel.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`0008 Skilled persons in the art will understand that the
`drawings, described below, are for illustration purposes only
`and do not limit the scope of the present invention in any way.
`It is appreciated that the quantity of the disclosed components
`could be more or less than what is disclosed unless expressly
`specified otherwise.
`0009 FIG. 1 shows a projective capacitive touch panel
`connecting to a controller according to the present invention;
`0010 FIG. 2 illustrates scanning the self capacitance of
`first-axis electrodes along a first-axis according to the present
`invention;
`0011
`FIG. 3 illustrates scanning the self capacitance of
`second-axis electrodes along a second-axis according to the
`present invention;
`0012 FIG. 4 shows a single touch on a touch panel accord
`ing to a first embodiment of the present invention;
`0013 FIG. 5 is a plan view of a single touch on a touch
`panel according to a preferred embodiment of the present
`invention;
`0014 FIG. 6 shows a double touch on a touch panel
`according to the first embodiment of the present invention;
`0015
`FIG. 7 shows a view of one of the electrodes in FIG.
`6;
`0016 FIG.8 shows the touched area and ghost area in FIG.
`6.
`
`DETAILED DESCRIPTION OF THE INVENTION
`
`0017. In accordance with the usual meaning of “a” and
`“the in patents, reference, for example, to “an electrode or
`“the electrode is inclusive of one or more electrodes. In this
`application, the use of the singular includes the plural and
`Vice versa unless specifically stated otherwise, for example,
`the term “mutual capacitance' includes singular and plural
`forms,. The section headings used herein are for organiza
`tional purposes only, and are not to be construed as limiting
`the subject matter described.
`0018. The detailed description of the present invention
`will be discussed in the following embodiments, which are
`not intended to limit the scope of the present invention, but
`still can be adapted for other applications. While drawings are
`illustrated in details, it is appreciated that the quantity of the
`disclosed components could be greater or less than disclosed,
`except those components with express restricting amount.
`0019. The method of the present invention is performed by
`a touch screen including a projective capacitive touch panel
`13 and a controller 14, which is shown in FIG. 1, the control
`ler 14 is electrically connected to the projective capacitive
`touch panel 13 to drive the projective capacitive touch panel
`13. The projective capacitive touch panel 13 includes M first
`axis electrodes parallelly arranged along a first-axis (defined
`as X-axis) and N Second-axis electrodes parallelly arranged
`along a second-axis (defined as y-axis). The first-axis and the
`second-axis are orthogonal to each other. There are M+N self
`capacitances measured as relative to ground. There are also
`MxN mutual capacitance formed at intersections between the
`first-axis electrodes and the second-axis electrodes.
`
`DELL EXHIBIT 1043 PAGE 8
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`

`

`US 2011/0175835 A1
`
`Jul. 21, 2011
`
`0020. The method for scanning a projective capacitive
`touch panel includes the following steps:
`A. Scanning each first-axis electrode and each second-axis
`electrode to get the first-axis electrodes and the second-axis
`electrodes whose self capacitance change;
`B. detecting the mutual capacitance at each intersection
`between the first-axis electrode and the second-axis electrode
`which electrodes self capacitance changes to determine
`whether the mutual capacitance changes, then the area where
`the mutual capacitance changes being taken as a touched area.
`0021
`FIG. 4 shows a single touch on a touch panel accord
`ing to a first embodiment of the present invention. A single
`touch affects the first-axis electrode(s) and the second-axis
`electrode(s) that pass through the touched area 133. In some
`embodiments, the width of the first-axis electrode or the
`second-axis electrode may be wider than the touched area
`133, thus the single touch may only involves one first-axis
`electrode and one second-axis electrode. If changes of the self
`capacitance of the first-axis electrode and second-axis elec
`trode are detected in the case of the single touch according to
`step A mentioned above, the position of a touch point can be
`determined by obtaining the x-coordinate (Xi, 1 sisM) of
`the first-axis electrode and the y-coordinate (Yi, 1 sisN) of
`the second-axis electrode. The mutual capacitance at the
`intersection between the first-axis electrode and the second
`axis electrode is further detected to confirm the position of the
`touched area which has only one touch point.
`0022. In other embodiments, the touched area is generally
`wider than the width of the electrodes. FIG.5 is a plan view of
`a single touch on a touch panel according to another embodi
`ment of the present invention, the width of the electrodes is
`half of the touched area 134, thus the touched area 134 of the
`single touch affects two first-axis electrodes and two second
`axis electrodes that pass through the touched area 134. There
`are four intersections having different coordinates located in
`the touched area, and a centroid can be further calculated
`according to the coordinates of the four intersections. ASSum
`ing that the X-coordinates of the touch-relevant first-axis elec
`trodes are X, X (1sisM-1), the voltage difference of the
`touched first-axis electrodes are U U (1sis M-1) respec
`tively; the y-coordinates of the touch-relevant second-axis
`electrodes are Y.Y. (1sisN-1), and the voltage difference
`of the touched second-axis electrodes are U U (1sjsN
`1) respectively. The x-coordinates of the centroid is X=(X,x
`U+XXU)/(U+U), and the y-coordinates of the cen
`troid is Y-(YXU+YXU)/(U+U), then the position of
`the touch point is determined by the centroid (X,Y). In other
`embodiments, the single touch may involves more than two
`first-axis electrodes or two second-axis electrodes, and the
`calculation method of the centroid is similar to the above
`mentioned method.
`0023. A more complicated situation is that there may be
`more than one touched area. A touch with more than one
`touched area will lead to forming ghost areas which are not
`really touched, but just a theoretically calculated result. If the
`ghost areas are not eliminated, they will be regarded as real
`touched areas in Subsequent process, definitely causing fake
`locating. FIG. 6 shows a double touch on a touch panel
`according to another embodiment of the present invention.
`The touch-relevant first-axis electrodes and second-axis elec
`trodes form intersections grouped in four areas 135a, 135b,
`135c and 135d(as shown in FIG. 7), of which areas 135a and
`135b are touched areas and areas 135c and 135d are ghost
`areas (as shown in FIG. 8). Since the ghost areas can not be
`
`recognized only by determining changes of the self capaci
`tance of the first-axis electrodes and the second-axis elec
`trodes, the mutual capacitance at the intersections in the areas
`135a, 135b, 135c and 135d will be further detected to deter
`mine the touched areas 135a and 135b according to step B.
`And the touch points are determined by calculating the cen
`troid of the touched areas.
`0024. According to the above embodiments, it needs to
`scan M-N--(p1xp2) times comparing to the conventional M
`X N times to get a touched area in a period of Scanning,
`wherein M and N are the number of the first-axis electrodes
`and the second-axis electrodes respectively, p1 and p2 are the
`number of the touch-relevant first-axis electrodes and second
`axis electrodes. When M and N are significantly greater than
`2 and p1, p2 are very Small, MxN is significantly greater than
`M+N+(p1xp2). In the case of a touch that two first-axis elec
`trodes and two second-axis electrodes are involved, if M and
`N are both greater than 4, MxN will be greater than M--N30
`2x2. In addition, if a touch involves 10 first-axis electrodes
`and 10 second-axis electrodes (this number is generally the
`maximum number of a multi-touch system can Support), M
`and N are both much greater than 11 in most touch panel
`applications, thus MxN will be much greater than M--N+10x
`10.
`0025. The calculation for a 42-inch touch screen which
`has 170 first-axis electrodes and 100 second-axis electrodes is
`described in detail as follows: referring to FIG.4, in the case
`of a single touch, only one first-axis electrode and one sec
`ond-axis electrode are touched, scanning the 170 first-axis
`electrodes and 100 second-axis electrodes will immediately
`get the first-axis electrodes and second-axis electrodes whose
`self capacitance changes, and get the unique intersection 133,
`thus conclude the touch point. Each scanning costs about 30
`us, therefore the total scanning time in a scanning period is
`(170+100)x30 us+ 1x1x30 us=8.13 ms, that is, the scanning
`frequency is 123 frames per second, which is greater than the
`conventional 1.96 frames per second. Referring to FIG. 6, in
`the case of a double touch and each touch with only one
`first-axis electrode and one second-axis electrode being
`touched, two first-axis electrodes (131a, 131b) and two sec
`ond-axis electrodes (132a, 132b) will be detected. The
`mutual capacitance at the four intersections will be detected
`according to step B, so the total scanning time in a scanning
`period is (170+100)+30 us+2x2x30 us=8.22 ms, that is, the
`scanning frequency is 121 frames per second, which is also
`greater than the conventional 1.96 frames per second.
`0026. It is obvious that the method for scanning a projec
`tive capacitive touch panel of the present invention can sig
`nificantly reduce the scanning time and boost the scanning
`frequency while the scanning accuracy is also guaranteed for
`a large touch panel.
`0027. The process of obtaining the first-axis electrode and
`the second-axis electrode whose self capacitance changes
`according to step A includes more detailed steps as follows:
`comparing a current self capacitance of each first-axis elec
`trode and second-axis electrode with a preset reference self
`capacitance;
`obtaining the first-axis electrode and the second-axis elec
`trode whose current self capacitance satisfies a preset condi
`tion defined by a preset threshold value to be exceeded by the
`difference of the self capacitance to the preset reference self
`capacitance.
`0028 Self capacitance can be obtained by charging an
`electrode (first-axis electrode or second-axis electrode) to a
`
`DELL EXHIBIT 1043 PAGE 9
`
`

`

`US 2011/0175835 A1
`
`Jul. 21, 2011
`
`preset capacitance and then connecting a reference capacitor
`to the electrode to charge the reference capacitor, the elec
`trode will discharge and its Voltage will decrease. The time
`that the Voltage decreases to a preset Voltage value can be
`measured and used to represent the self capacitance of the
`electrode.
`0029. There are two ways of setting the preset reference
`self capacitance of each first-axis electrode and second-axis
`electrode: the first way is directly writing the empirical value
`in the controller 14, the second way is getting an average
`value of multiple initial self capacitance correspondingly
`obtained from initialization scanning of the first-axis elec
`trode and second-axis electrode repeatedly. Since each elec
`trode has a preset reference self capacitance, there will be
`M+N preset reference self capacitance.
`0030 The initialization scanning includes: charging each
`of the first-axis electrode and second-axis electrode; dis
`charging the reference capacitor connected to each of the
`first-axis electrode and second-axis electrode; obtaining the
`initial self capacitance of each of the first-axis electrode and
`the second-axis electrode according to the time of discharg
`ing when the discharging process is completed.
`0031
`FIG. 2 illustrates scanning the self capacitance of
`first-axis electrodes along a first-axis according to the present
`invention. The controller 14 charges each first-axis electrode
`arranged along the first-axis (X-axis) and then discharge each
`of the first-axis electrode to the reference capacitor corre
`spondingly connected to each of the first-axis electrode.
`When the discharging process of the first-axis electrode is
`completed, the current self capacitance of the first-axis elec
`trode can be calculated. FIG. 3 illustrates scanning the self
`capacitance of second-axis electrodes along a second-axis
`according to the present invention. The current self capaci
`tance of the second-axis electrode can be obtained by the
`same method.
`0032. The process of determining whether the mutual
`capacitance changes includes: comparing a current mutual
`capacitance at each intersection with a preset reference
`mutual capacitance at the intersection; obtaining the current
`mutual capacitance that satisfies a preset condition.
`0033. There are also two ways of setting the reference
`mutual capacitance at the intersections: the first way is
`directly writing the empirical value in the controller 14; the
`second way is calculating an average value of multiple initial
`mutual capacitance obtained from initialization scanning of
`the intersections repeatedly. Since there is a reference mutual
`capacitance for each intersection, there will be MXN preset
`reference mutual capacitance totally.
`0034. The initialization scanning includes: charging each
`second-axis electrode; collecting the electric charges induced
`in the first-axis electrode and converting the electric charges
`to Voltage value, according to which obtain the initial mutual
`capacitance at each intersection. In an alternative embodi
`ment, the first-axis electrode may be firstly charged.
`0035. The self capacitance or mutual capacitance may
`change in many situations, not only by touch, but also such as
`insufficient charge of the electrodes. In order to distinguish
`the capacitance change caused by a real touch or other events,
`the change of the current self capacitance or the current
`mutual capacitance should satisfy a preset condition. Gener
`ally, the preset condition is defined by a preset threshold
`value. For detecting the self capacitance, the difference of the
`self capacitance to the preset reference self capacitance must
`be greater than a corresponding preset threshold value, when
`
`this condition is satisfied, a touch on the electrode can be
`confirmed. Similarly, for detecting the mutual capacitance
`change, the difference of the current mutual capacitance to
`the reference mutual capacitance at an intersection must be
`greater than another corresponding preset threshold value,
`when this condition is satisfied, a touch on the intersection
`can be confirmed.
`0036) A storage medium is provided as well. The storage
`medium is used for storing a set of instructions capable of
`being executed by a processor to perform a method for scan
`ning a projective capacitive touch panel. The method com
`prises:
`A. Scanning each first-axis electrode arranged along a first
`axis and each second-axis electrode arranged along a second
`axis, then obtaining the first-axis electrode and the second
`axis electrode whose self capacitance changes;
`B. detecting the mutual capacitance at each intersection
`between the first-axis electrode and the second-axis electrode
`whose self capacitance changes to determine whether the
`mutual capacitance changes, then taking an area where the
`mutual capacitance changes as a touched area.
`0037. A system for scanning a projective capacitive touch
`panel is also provided. The system includes a scanning mod
`ule and a controlling module. The scanning module is used
`for detecting self capacitances of first-axis electrodes and
`second-axis electrodes. The controlling module is used for
`determining whether the self capacitances change and con
`trolling the scanning module to detecting a mutual capaci
`tance at an intersection between a first-axis electrode and a
`second-axis electrode if the self capacitance of the first-axis
`electrode and the second-axis electrode changes and deter
`mining a touched area defined by the intersection having a
`changed mutual capacitance.
`0038. While certain embodiments have been shown and
`described, various modifications and Substitutions may be
`made thereto without departing from the spirit and scope of
`the invention. Accordingly, it is to be understood that the
`present invention has been described by way of illustration
`and not limitations.
`What is claimed is:
`1. A method for Scanning a projective capacitive touch
`panel, comprising:
`A-Scanning each first-axis electrode arranged along a first
`axis and each second-axis electrode arranged along a
`second-axis by a controller, then obtaining the first-axis
`electrode and the second-axis electrode whose self
`capacitance changes;
`B- detecting mutual capacitance at each intersection
`between the first-axis electrode and the second-axis
`electrode which electrodes self capacitance changes to
`determine whether the mutual capacitance changes, then
`area where the mutual capacitance changes being taken
`as a touched area.
`2. The method according to claim 1, wherein the process of
`obtaining the first-axis electrode and the second-axis elec
`trode whose self capacitance changes according to step A
`comprises:
`comparing a current self capacitance of each of the first
`axis electrode and the second-axis electrode with a pre
`set reference self capacitance of the respective first-axis
`electrode and second-axis electrode:
`obtaining the first-axis electrode and the second-axis elec
`trode whose current self capacitance satisfies a preset
`condition.
`
`DELL EXHIBIT 1043 PAGE 10
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`US 2011/0175835 A1
`
`Jul. 21, 2011
`
`3. The method according to claim 2, wherein the process of
`obtaining the current self capacitance comprises:
`charging each of the first-axis electrode and the second
`axis electrode;
`discharging each of the first-axis electrode and the second
`axis electrode to a reference capacitor correspondingly
`connected to the first-axis electrode and the second-axis
`electrode:
`obtaining the current self capacitance of the first-axis elec
`trode and the second-axis electrode when the process of
`discharging is completed.
`4. The method according to claim 2, wherein the preset
`reference self capacitance of each of the first-axis electrode
`and the second-axis electrode is an average value of multiple
`initial self capacitance obtained from repeated initialization
`scanning of each of the first-axis electrode and the second
`axis electrode correspondingly.
`5. The method according to claim 4, wherein the initializa
`tion Scanning comprises:
`charging each of the first-axis electrode and the second
`axis electrode;
`discharging each of the first-axis electrode and the second
`axis electrode to a reference capacitor correspondingly
`connected to each of the first-axis electrode and the
`second-axis electrode:
`obtaining the initial self capacitance of each of the first
`axis electrode and the second-axis electrode when the
`process of discharging is completed.
`6. The method according to claim 2, wherein the preset
`condition is difference of the self capacitance to the preset
`reference self capacitance is greater than a preset threshold
`value.
`7. The method according to claim 1, wherein the process of
`determining whether the mutual capacitance changes com
`prises:
`comparing a current mutual capacitance at each intersec
`tion with a preset reference mutual capacitance at the
`intersection;
`obtaining the area where the current mutual capacitance
`satisfies a preset condition.
`8. The method according to claim 7, wherein the process of
`obtaining the current mutual capacitance comprises:
`charging each of the second-axis electrode whose self
`capacitance changes;
`collecting electric charges induced in the first-axis elec
`trode and converting the electric charges to Voltage
`value, according to which obtaining the current mutual
`capacitance at the intersection.
`
`9. The method according to claim 7, wherein the preset
`reference mutual capacitance at the intersection is an average
`value of multiple initial mutual capacitance obtained from
`initialization scanning of the intersection repeatedly.
`10. The method according to claim 9, wherein the initial
`ization scanning comprises:
`charging each of the second-axis electrode:
`collecting electric charges induced in the first-axis elec
`trode and converting the electric charges to Voltage
`value, according to which obtaining the initial mutual
`capacitance at the intersection.
`11. The method according to claim 7, wherein the preset
`condition is difference of the current mutual capacitance to
`the preset reference mutual capacitance at the intersection is
`greater than a preset threshold value.
`12. The method according to claim 1 further comprising:
`calculating centroid of the touched area.
`13. The method according to claim 1, wherein if the self
`capacitance of any of the first-axis electrode or the second
`axis electrode does not change, repeat step A.
`14. A storage medium for storing a set of instructions to
`perform a method for Scanning a projective capacitive touch
`panel, the method comprising:
`A-Scanning each first-axis electrode arranged along a first
`axis and each second-axis electrode arranged along a
`second-axis, then obtaining the first-axis electrode and
`the second-axis electrode whose self capacitance
`changes;
`B- detecting mutual capacitance at each intersection
`between the first-axis electrode and the second-axis
`electrode whose self capacitance changes to determine
`whether the mutual capacitance changes, then area
`where the mutual capacitance changes being taken as a
`touched area.
`15. A system for Scanning a projective capacitive touch
`panel, comprising:
`a scanning module for detecting self capacitances of first
`axis electrodes and second-axis electrodes;
`a controlling module for determining whether the self
`capacitances change and controlling the scanning mod
`ule to detect a mutual capacitance at an intersection
`between the first-axis electrode and the second-axis
`electrode if the self capacitance of the first-axis elec
`trode and the second-axis electrode changes and deter
`mining a touched area defined by the intersection having
`a changed mutual capacitance.
`
`c
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`c
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`c
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`c
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`c
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`DELL EXHIBIT 1043 PAGE 11
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