US009 104277B2
`
`(12) United States Patent
`Wang et al.
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 9,104.277 B2
`Aug. 11, 2015
`
`(54) SENSING METHOD AND CALIBRATION
`METHOD FOR A CAPACTIVE TOUCH
`PANEL
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`(75) Inventors: Tsun-Min Wang, Miaoli County (TW);
`Chun-Chung Huang, Hsinchu (TW)
`
`(73) Assignee: ELAN MICROELECTRONICS
`CORPORATION, Hsinchu (TW)
`
`(*) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 775 days.
`
`(21) Appl. No.: 12/946,230
`
`(22) Filed:
`
`Nov. 15, 2010
`
`(65)
`
`Prior Publication Data
`US 2011 FO115743 A1
`May 19, 2011
`
`(30)
`
`Foreign Application Priority Data
`
`Nov. 19, 2009 (TW) ............................. O981 39327A
`
`(2006.01)
`(2006.01)
`
`(51) Int. Cl.
`G06F 3/04
`G06F 3/044
`(52) U.S. Cl.
`CPC ...................................... G06F 3/044 (2013.01)
`(58) Field of Classification Search
`CPC ............................... G06F 3/044: G06F 3/0418
`USPC .................................................. 345/173, 178
`See application file for complete search history.
`
`8,378.981 B2 * 2/2013 Yilmaz et al. ................. 345,173
`2002/001 1991 A1
`1/2002 Iwasaki et al. .
`... 345,173
`2002/0070926 A1* 6/2002 Kavanagh ......
`... 345,173
`2003/0098858 A1* 5, 2003 Perski et al. .......
`... 345,173
`2004/0217945 A1 * 1 1/2004 Miyamoto et al. ............ 345,173
`2006.01258O1 A1
`6/2006 Hsu et al.
`2006/0267953 A1* 11/2006 Peterson et al. .............. 345,173
`2008/0042994 A1* 2/2008 Gillespie et al. ...
`... 345,174
`2008/0158172 A1* 7/2008 Hotelling et al. .
`... 345,173
`2008. O158174 A1* 7, 2008 Land et al. .....
`... 345,173
`2008. O158182 A1* 7, 2008 Westerman ....
`... 345,173
`2011 0115717 A1* 5, 2011 Hable et al. ....
`... 345,173
`2013/0147732 A1* 6, 2013 Peterson et al. .............. 345,173
`
`
`
`FOREIGN PATENT DOCUMENTS
`
`6, 2006
`20062O122
`TW
`8, 2009
`200933463 A
`TW
`200945151 A 11, 2009
`TW
`* cited by examiner
`Primary Examiner — Roy Rabindranath
`(74) Attorney, Agent, or Firm — Muncy, Geissler, Olds &
`Lowe, P.C.
`ABSTRACT
`(57)
`Stimulus regions are defined based on the traces of a capaci
`tive touchpanel. A first signal is applied to a first trace in a first
`direction under a second signal applied to a second trace in a
`second direction to stimulate the second trace, to sense a
`stimulus region for an ADC value thereof. Calibration param
`eters for the traces are determined according to the ADC
`values of the traces without being touched, and are stored for
`later sensing the traces for position calculation and multi
`finger calculation.
`74 Claims, 14 Drawing Sheets
`
`Yn
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`Stimulated
`
`a
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`a.
`
`DELL EXHIBIT 1034 PAGE 1
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`U.S. Patent
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`Aug. 11, 2015
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`Sheet 1 of 14
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`US 9,104.277 B2
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`st
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`DELL EXHIBIT 1034 PAGE 2
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`U.S. Patent
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`Aug. 11, 2015
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`Sheet 2 of 14
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`US 9,104.277 B2
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`DELL EXHIBIT 1034 PAGE 3
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`U.S. Patent
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`Aug. 11, 2015
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`Sheet 3 of 14
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`DELL EXHIBIT 1034 PAGE 4
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`U.S. Patent
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`Aug. 11, 2015
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`Sheet 4 of 14
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`US 9,104.277 B2
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`DELL EXHIBIT 1034 PAGE 5
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`U.S. Patent
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`Aug. 11, 2015
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`Sheet 5 of 14
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`US 9,104.277 B2
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`Yn
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`or Y1, Y2Y3.Yn
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`Fig. 5
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`DELL EXHIBIT 1034 PAGE 6
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`U.S. Patent
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`Aug. 11, 2015
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`Sheet 6 of 14
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`US 9,104.277 B2
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`Stimulated
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`Fig. 6
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`DELL EXHIBIT 1034 PAGE 7
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`U.S. Patent
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`Aug. 11, 2015
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`Sheet 7 of 14
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`US 9,104.277 B2
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`DELL EXHIBIT 1034 PAGE 8
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`U.S. Patent
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`Aug. 11, 2015
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`Sheet 8 of 14
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`US 9,104.277 B2
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`U.S. Patent
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`Aug. 11, 2015
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`Sheet 9 of 14
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`DELL EXHIBIT 1034 PAGE 10
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`U.S. Patent
`U.S. Patent
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`Aug. 11, 2015
`Aug. 11, 2015
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`Sheet 10 of 14
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`DELL EXHIBIT 1034 PAGE 11
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`U.S. Patent
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`Aug. 11, 2015
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`Sheet 11 of 14
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`US 9,104,277 B2
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`DELL EXHIBIT 1034 PAGE 12
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`DELL EXHIBIT 1034 PAGE 12
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`Aug. 11, 2015
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`Sheet 12 of 14
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`US 9,104.277 B2
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`DELL EXHIBIT 1034 PAGE 13
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`U.S. Patent
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`Aug. 11, 2015
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`Sheet 13 of 14
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`US 9,104.277 B2
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`V
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`Stimulus and Sensed
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`DELL EXHIBIT 1034 PAGE 14
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`U.S. Patent
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`Aug. 11, 2015
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`Sheet 14 of 14
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`US 9,104,277 B2
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`DELL EXHIBIT 1034 PAGE 15
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`DELL EXHIBIT 1034 PAGE 15
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`US 9,104,277 B2
`
`1.
`SENSING METHOD AND CALIBRATION
`METHOD FOR A CAPACTIVE TOUCH
`PANEL
`
`FIELD OF THE INVENTION
`
`The present invention is related generally to a capacitive
`touch panel and, more particularly, to a sensing method and
`calibration method for a capacitive touch panel.
`
`10
`
`BACKGROUND OF THE INVENTION
`
`15
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`25
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`30
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`35
`
`Sensing a capacitive touch panel is achieved by coopera
`tion between the capacitive touch panel and the hardware,
`firmware and software of the touch circuit. For example, a
`capacitive touch panel having a two-dimensional trace layout
`requires a two-dimensional touch circuit to sense therewith
`and to convert the sensed capacitance variation of each trace
`into a digital value, called analog-to-digital conversion
`(ADC) value, for position detection of the object thereon.
`FIG. 1 is a schematic diagram of a typical capacitive touch
`panel module, which includes a component carrier 10, a
`capacitive touch panel 12 and a capacitive touch sensor 14
`printed on the capacitive touch panel 12. The component
`carrier 10 is typically a flexible printed circuit (FPC) board,
`with a chip of integrated circuit (IC) including a detector
`circuit deposited thereon and connected to the capacitive
`touch sensor 14 through the metal wires printed on the com
`ponent carrier 10.
`In terms of object detection, a two-dimensional capacitive
`touchpanel requires much less computation than an all-point
`array capacitive touch panel. However, for multi-finger appli
`cations, a two-dimensional capacitive touch panel has its
`congenital defect, the ghost phenomenon, that is not found in
`an all-point-array capacitive touch panel. FIG. 2 is a sche
`matic diagram showing the ghost phenomenon, and as it is
`shown, a two-dimensional capacitive touch panel 12 has X
`traces X1-Xm and Y traces Y1-Yn, and the conventional
`two-dimensional object detection includes sequential scan of
`all the traces X1-Xm and Y1-Yn one by one to extract the X
`40
`and Y ADC values, and combination of the X and Y ADC
`values to locate the object position. In single-finger applica
`tions, for example, only one finger touching at the position 20,
`the X and Y traces are sequentially scanned for their ADC
`values which indicate the capacitance variations thereof, and
`45
`it will find that the traces where the position 20 is have
`significant capacitance variations, i.e., the Xtrace having the
`largest capacitance variation is the trace X3 and the Y trace
`having the largest capacitance variation is the trace Y3. Thus,
`it is easy to identify the finger position (X3.Y3), called “real
`point. However, if there are two fingers touching at the
`positions 20 and 22 respectively, then it will find two peaks on
`the Xtraces X3 and X10 and two peaks on the Y traces Y3 and
`Y10 after scanning all the X and Y traces. Therefore, from the
`combination of the peak ADC values, it will obtain four
`positions (X3, Y3), (X10, Y7), (X3,Y7) and (X10, Y3), indi
`cated by the numerals 20, 22, 24 and 26, of which, however,
`the positions 24 and 26 have no fingers thereon and are called
`“ghost points'. Obviously, the ghost points will lead to incor
`rect location of the fingers.
`With the gradual popularization of multi-finger applica
`tions in capacitive touch panels, the modern capacitive touch
`panels are required to satisfy the needs of two or more finger
`detection. For the ghost issue on the two-dimensional object
`detection, a multi-touch sensing method is proposed to obtain
`all-point-array data from a two-dimensional structure, which
`may distinguish between real points and ghost points based
`
`50
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`60
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`65
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`2
`on the characteristic that the trace of a real point will have a
`significantly greater or Smaller self capacitance to ground
`than the trace of a ghost point. FIG. 3 is a schematic diagram
`showing a conventional two-step sensing method and FIG. 4
`is a flowchart thereof. This method still includes the step S30
`to sequentially scan the X and Y traces to get all the X and Y
`ADC values. However, the next step S32 will identify if there
`is a multi-finger touch, and if it does not find any multi-finger
`touch, then step S34 will be performed for position calcula
`tion with the X and Y ADC values whenever the capacitive
`touch panel is touched. If the step 32 does find a multi-finger
`touch, then step S36 will be performed to carry out a multi
`finger scan which includes an inphase crisscross sensing pro
`cess applied to the four positions 20, 22, 24 and 26, as shown
`in FIG.3 for example. In further detail, the trace Y3 is stimu
`lated by a current signal when sensing the trace X3 to detect
`the self capacitance variation of the position 20; the trace Y7
`is stimulated by a current signal when sensing the trace X3 to
`detect the self capacitance variation of the position 24; the
`trace Y3 is stimulated by a current signal when sensing the
`trace X10 to detect the self capacitance variation of the posi
`tion 26; and the trace Y7 is stimulated by a current signal
`when sensing the trace X10 to detect the self capacitance
`variation of the position 22. Then, step S38 is performed to get
`the ADC values from the real and ghost points 20, 22, 24 and
`26, and step S40 compares the ADC values to distinguish
`between the real points 20, 22 and the ghost points 24, 26.
`As illustrated in the above description, the conventional
`two-step sensing method first identifies a multi-finger touch
`and then senses the self capacitance variation of each possible
`position again with particular sensing process in the latter
`multi-finger scan. Unfortunately, the intersection points on a
`capacitive touch panel may be different in self capacitance.
`Thus, before the sensing process of FIG. 4, it is necessary to
`perform the inphase crisscross sensing process for each inter
`section point without being touched to get the ADC values
`thereof, in order to determine the calibration parameter of
`each intersection point for its analog-to-digital conversion.
`The calibration parameters are to make the ADC values of all
`the intersection points without being touched fall in a same
`level range, and are stored in advance for application to the
`sensing of the capacitive touch panel to calibrate the sensed
`data each time in the future. Therefore, when the capacitive
`touchpanel is in practice, the ADC value detected from a trace
`will indicate the self capacitance variation of the trace, and
`can be used to distinguish between real points and ghost
`points correctly. For a two-dimensional capacitive touch
`panel, if the number of the Xtraces is mand the number of the
`Y traces is n, then the conventional two-step sensing method
`needs to store mxn calibration parameters in advance, which
`requires relatively large memory.
`
`SUMMARY OF THE INVENTION
`
`An object of the present invention is to provide a sensing
`method for a capacitive touch panel.
`Another object of the present invention is to provide a
`calibration method for a capacitive touch panel.
`A further object of the present invention is to reduce the
`memory requirement for storing the calibration parameters of
`a capacitive touch panel.
`According to the present invention, stimulus regions are
`defined based on the traces of a capacitive touch panel. When
`sensing a first trace in a first direction, a first signal is applied
`to the first trace and a second signal is applied to a second
`trace in a second direction to stimulate the second trace, and
`an ADC value is detected from a stimulus region on the first
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`3
`trace and the second trace. The ADC value of a stimulus
`region on a sensed trace without being touched is used to
`determine the calibration parameters for the traces, such that
`the ADC values of the stimulus regions on a trace without
`being touched will fall within a level range. The calibration
`parameters are stored for later position calculation and multi
`finger calculation. The second signal may be in phase or out
`of phase with the first signal, or a common Voltage. In object
`detection, the traces are sensed for variation of their self
`capacitance but not mutual capacitance. The real points can
`be identified by scanning only the traces in either of the first
`direction and the second direction. By sensing the ADC val
`ues of the stimulus regions, the scan time of the capacitive
`touch panel is shorter, and the volume of the calibration
`parameters is less. The combination of the traces to define the
`stimulus regions is adjustable, and thus the sensing of the
`capacitive touch panel is adaptive to different applications for
`saving of power and time.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`4
`tially applied to the traces Y1, Y2. . . . . Yn to stimulate them
`one by one. In this embodiment, each intersection point
`between the trace X1 and the traces Y1-Yn is defined as a
`stimulus region. By sensing the trace X1 under the traces
`Y1-Yn stimulated one by one, the ADC values of then stimu
`lus regions defined on the trace X1 are obtained. Then, the
`ADC values of then stimulus regions defined on the trace X2
`are obtained in the same way, i.e., sensing the trace X2 under
`the traces Y1-Yn sequentially stimulated. In the same man
`ner, the ADC values of all the traces are obtained for later
`position calculation for real points. The crisscross sensing
`process of detecting the ADC value of a stimulus region on a
`trace can be performed in other ways. For example, as shown
`in the table of FIG.5, when sensing the trace X1, each time the
`second signal is simultaneously applied to two of the Y traces,
`e.g. Y1 and Y2. In this case, the stimulus region is defined
`larger, including two intersection points of an X trace with
`two of the Y traces, as indicated by the dash circle shown in
`FIG. 5. This approach will reduce the number of the total
`stimulus regions. For example, if defining a stimulus region to
`include only an intersection point results in n stimulus
`regions, then the number of the stimulus regions will be n/2 by
`defining a stimulus region to include two intersection points.
`In other embodiments, it is feasible to sense two of the X
`traces, e.g. X1 and X2 or X1 and X3, at a same time by using
`two detectors under stimulating the Y traces, to shorten the
`sensing time. In this way, for the crisscross sensing process,
`the Xtraces to be sensed and the Y traces to be stimulated may
`be combined one-to-one, one-to-many, many-to-one or
`many-to-many to define a group of stimulus regions, and by
`sensing each of the stimulus regions, the process of detecting
`the ADC values of the Xtraces will be completed with shorter
`time and less operation.
`FIG. 6 is a schematic diagram showing sensing stimulus
`regions along the Y traces, which is the same as that illustrated
`in FIG. 5, combining the Ytraces to be sensed and the Xtraces
`to be stimulated in one-to-one, one-to-many, many-to-one or
`many-to-many manner to define a group of stimulus regions
`for the crisscross sensing process. The ADC values of the
`stimulus regions defined on the X and Y traces are stored for
`later position calculation for real points. The stimulus regions
`as depicted in FIGS. 5 and 6 may be adjusted according to the
`system required resolution. Preferably, several groups of
`stimulus regions defined with different combinations of
`traces to be sensed and traces to be stimulated are pre-stored
`in the system, to be selected for use depending on the appli
`cation modes to reduce power and time consumption for the
`crisscross sensing process.
`FIG. 7 is a flowchart of a sensing method using the stimulus
`region sensing scheme according to the present invention. In
`object detection, step S42 stimulates the Y traces and senses
`the X traces to extract a first ADC value of each stimulus
`region defined on the X traces, for example by the process
`illustrated in FIG. 5, and step S44 stimulates the Xtraces and
`senses the Y traces to extract a second ADC value of each
`stimulus region defined on the Y traces, for example by the
`process illustrated in FIG. 6. In other embodiments, the
`sequence of the steps S42 and S44 is exchanged without
`departing from the purpose of getting the ADC values of all
`stimulus regions. After the steps S42 and S44, the first and
`second ADC values obtained by sensing all the stimulus
`regions will provide Sufficient information for position cal
`culation S46 for single-finger applications and for multi
`finger calculation S48. In the multi-finger calculation S48,
`depending on the algorithm used, it is possible to obtain the
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`These and other objects, features and advantages of the
`present invention will become apparent to those skilled in the
`art upon consideration of the following description of the
`preferred embodiments of the present invention taken in con
`junction with the accompanying drawings, in which:
`FIG. 1 is a schematic diagram of a typical capacitive touch
`panel module:
`FIG. 2 is a schematic diagram showing the ghost phenom
`enon of a two-dimensional capacitive touch panel;
`FIG. 3 is a schematic diagram showing a conventional
`two-step sensing method;
`FIG. 4 is a flowchart of a conventional two-step sensing
`method;
`FIG. 5 is a schematic diagram showing sensing stimulus
`regions along the X traces;
`FIG. 6 is a schematic diagram showing sensing stimulus
`regions along the Y traces:
`FIG. 7 is a flowchart of a sensing method using the stimulus
`region sensing scheme according to the present invention;
`40
`FIG. 8 shows a distribution of the ADC values of two Y
`traces obtained by using the one-to-one scheme to sense all
`the stimulus regions defined thereon;
`FIG. 9 is a schematic diagram showing a multi-finger cal
`culation in an embodiment according to the present invention;
`FIG. 10 is a 3-dimensional view of the ADC values of all
`the intersection points obtained by Scanning the Y traces
`using the process of FIG. 7:
`FIG. 11 is a flowchart of another embodiment for sensing
`stimulus regions according to the present invention;
`FIG. 12 is a schematic diagram showing the operation
`when using the sensing method of FIG. 11;
`FIG. 13 is waveform diagram of the signals to be applied to
`the sensed trace and the stimulated trace when a Voltage type
`detector circuit is used for sensing the self capacitance varia
`tion of the sensed trace; and
`FIG. 14 is a schematic diagram showing another stimulus
`scheme for sensing a stimulus region.
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`DETAILED DESCRIPTION OF THE INVENTION
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`60
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`FIG. 5 is a schematic diagram showing sensing stimulus
`regions along the X traces to detect the ADC values of the
`entire capacitive touch panel in advance as the reference for
`position calculation in the later object detection. When sens
`ing the trace X1, a first signal is applied to the trace X1 to
`detect the ADC value thereof, and a second signal is sequen
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`65
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`information of the entire capacitive touch panel sufficient to
`locate all the objects by merely sensing either the Xtraces or
`the Y traces.
`For example, by using the one-to-one scheme in the step
`S44 to sense all the stimulus regions on the trace Y3 and Y 7
`shown in FIG. 6, a distribution of ADC values is obtained as
`shown in FIG. 8, in which the triangles represent the ADC
`values of the stimulus regions when the traces Y3 and Y7 are
`not touched, and the rounds represent the ADC values of the
`stimulus regions when the traces Y3 and Y7 are touched.
`Since the capacitive touch panel have been calibrated in
`advance, the object-absent ADC values sensed from the traces
`Y3 andY7 will fall within a range around a level 52 and a level
`54 respectively, and the object-present ADC values sensed
`from the traces Y3 and Y7 will obviously apart from the level
`52 and the level 54 respectively. In the position calculation
`S46 of FIG. 7, an algorithm Such as accumulation, averaging
`and weighted averaging may be used or a digital filter may be
`used, to determine the representative values of the traces Y3
`and Y7 respectively. For the trace Y3, the object-absent rep
`resentative value is near the level 52, and the object-present
`representative value 56 is apart from the level 52 by an obvi
`ous difference D, which indicates the self capacitance
`variation of the trace Y3 caused by the touch thereon. Like
`wise, the difference D, between the object-present represen
`tative value 58 and the object-absent representative value 54
`indicates the self capacitance variation of the trace Y7 caused
`by the touch thereon.
`In single-finger applications, through the position calcula
`tion S46 shown in FIG. 7, the real point can be located with
`the representative values of the X and Y traces. However, in
`multi-finger applications, it is necessary to further use the
`steps S42 and S44 to sense the first and second ADC values of
`all the stimulus regions and the step S48 to locate the real
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`points. FIG. 9 is a schematic diagram showing a multi-finger
`calculation in an embodiment according to the present inven
`tion. After the steps S42 and S44 of FIG.7 to extract the ADC
`values of all the stimulus regions based on the calibration
`parameters of the traces, and the position calculation S46 to
`obtain the positions 20, 22, 24 and 26 that may be include one
`or more ghost points, the ADC values of the traces X3 and
`X10 or the ADC values of the traces Y3 and Y7 where the
`positions 20, 22, 24 and 26 are located are used to generate the
`distribution curves of the ADC values of the traces X3, X10,
`Y3 andY7, as shown in the left part and the lower part of FIG.
`9. Then, according to the varying level of the ADC values, the
`really real points 20 and 22 and the ghost points 24 and 26 are
`discriminated, thereby accomplishing the object positioning.
`If using the process of FIG. 7 to perform the steps S42 and
`S44 with the one-to-one scheme for sensing all the stimulus
`regions for the ADC values of all the intersection points, the
`multi-finger calculation S48 may be directly performed with
`only the ADC values of one axis. As shown in FIG. 10, the
`ADC values of all the intersection points obtained by scan
`ning the Y traces are plotted in a 3-dimensional (3D) view,
`which clearly shows the difference of self capacitance varia
`tion between real points and ghost points. Therefore, after
`sensing for an entire frame, since the self capacitance varia
`tion of each point on the capacitive touch panel has been
`extracted, finer multi-finger applications can be achieved
`later, by using multi-finger calculation Such as an image pro
`cessing algorithm. In addition, this method also helps to rec
`ognize the level of the pressure caused by the fingers. Thus,
`for the multi-finger calculation S48 alone, it can be easily
`accomplished by performing only one of the steps S42 and
`S44.
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`Although the above embodiment solves the ghost problem,
`it may be limited to the stable time of the analog frontend and
`thus take relatively long time for scanning all the stimulus
`regions. When applied to a large-size touch screen, this
`method may impact the frame rate. FIG. 11 is a flowchart of
`another embodiment for sensing stimulus regions according
`to the present invention, which uses hybrid scan to reduce the
`scanning time of a capacitive touch panel. In step S60, the
`traces in a direction are selected to be sensed, by which the
`ADC value of a stimulus region on one of the traces is
`detected, and then the detected ADC value is compared with
`a threshold value in step S62. If the detected ADC value is less
`than the threshold value, the process will return to the step
`S60 to sense the next one of the traces. If the detected ADC
`value is greater than the threshold value, it is indicated that
`there is a finger touching the sensed trace, and the process will
`go to step S64 to sense the ADC values of all the stimulus
`regions defined on the sensed trace. Then, the process returns
`to the step S60 to sense the next one of the traces. Step S66
`identifies whether the scan to the traces in the selected direc
`tion has been finished. If yes, according to the ADC values of
`all the stimulus regions on the touched traces, step S68 is
`performed to locate the real points. In another embodiment,
`when the ADC value of a stimulus region on a trace is detected
`greater than the threshold value, it will directly sense all the
`other stimulus regions on the trace and all the stimulus
`regions on the next several traces to speed up the process by
`saving the comparison of the step S62. In yet another embodi
`ment, the step S60 selects a direction to sense the stimulus
`region of the traces thereof in a jumping manner, e.g. the first
`trace, the third trace, the fifth trace and so on, by which the
`scan time for the entire capacitive touch panel will be dra
`matically reduced. Moreover, when the ADC value of a
`stimulus region on a sensed trace is greater than the threshold
`value, it will directly sense all the other stimulus regions on
`the sensed trace and all the stimulus regions on the next
`several traces in the jumping manner to further speed up the
`process by saving the comparison of the step S62.
`FIG. 12 is a schematic diagram showing the operation
`when using the sensing method of FIG. 11. At the beginning,
`the step S60 selects the Xtraces on the capacitive touch panel
`12 to sense for ADC values. Foe example, the stimulus region
`defined at the intersection point (X1, Y5) between the traces
`X1 and Y5 is first sensed and then, from the detected ADC
`value, the step S62 identifies no fingers touching thereon.
`After the step S66 identifies that the scan to the Xtraces is not
`finished, the process returns to the step S60 for sensing the
`stimulus region defined at the intersection point (X2, Y5)
`between the next trace X2 and the trace Y5. Following the
`same procedure, the process will finally find that the ADC
`value of the stimulus region at the intersection point (X10.
`Y5) between the trace X10 and the trace Y5 is greater than the
`threshold value, since the trace X10 is touched. Therefore, the
`step S64 will sense all the other stimulus regions defined on
`the trace X10, i.e. at the intersection points (X10, Y1), (X10.
`Y2), (X10, Y3) and so on. Then, the next traces X11 and X12
`may be sensed in the same way, i.e., sensing all the other
`stimulus regions thereof after the step S62. In another
`embodiment, after sensing all the other stimulus regions
`defined on the trace X10, it will directly sense all the stimulus
`regions defined on the next traces X11 and X12, without
`performing the step S62 for the traces X11 and X12, to
`achieve the same result. In still another embodiment, the step
`S60 selects the odd traces X1,X3,Y5... to sense. In this case,
`the process will first find the intersection point (X11, Y5)
`having an ADC value greater than the threshold value, and
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`thus directly sense all the stimulus regions on the traces X10
`and X12 Subsequently to sensing all the other stimulus
`regions on trace X11.
`Taking a Voltage type detector circuit for example, refer
`ring to FIG. 13, when the first signal to be applied to the
`sensed traces for sensing for the ADC value thereof has a
`waveform 70, the second signal for stimulating the related
`trace or traces with a stimulus region may have an inphase
`waveform 72, an out-of-phase waveform 74 or a common
`voltage waveform 76. In other embodiments, for sensing and
`stimulating the traces, current signals or combination of a
`Voltage signal and a current signal may be used instead to
`apply to the sensed trace and the stimulated trace. In addition,
`as shown in FIG. 14, it may use another stimulus scheme to
`sense the stimulus region at the intersection point (X3.Y2), in
`which in addition to a first signal applied to the trace Y2 for
`sensing the ADC value of the stimulus region and a second
`signal applied to the trace X3 for stimulating the trace X3, a
`third signal is also simultaneously applied to the traces Y1 and
`Y3 adjacent to the sensed trace Y2 for stimulating the traces
`Y1 and Y3. For example, as shown in FIG. 14, the second
`signal applied to the trace X3 is out of phase with the first
`signal applied to the trace Y2, and the third signal applied to
`the traces Y1 and Y3 is in phase with the first signal applied to
`the tracey 2. When sensing the trace Y2, stimulating the traces
`Y1 and Y3 with the third signal will reduce the influence
`caused by the lateral capacitances, i.e. mutual capacitances
`between traces, and thus allows the obtained ADC value
`representing the real self capacitance variation more pre
`cisely. Alternatively, all the traces other than the sensed trace
`Y2 and the stimulated trace X3 are simultaneously applied
`with a third signal having either of the waveforms 72, 74 and
`76 shown in FIG. 13 and in this case, the common voltage
`waveform 76 is preferred for the trace X3; or all the traces
`other than the sensed trace Y2 and the stimulated trace X3 are
`simultaneously applied with a third signal having the inphase
`waveform 72, and the second signal applied to the trace X3
`has the out-of-phase waveform 74.
`In the calibration for the sensing method according to the
`present invention, it may sense only the ADC value of a
`stimulus region on the trace to be sensed, by which it will get
`a set of calibration parameters for analog-to-digital conver
`sion to calibrate the ADC values of the sensed stimulus
`regions without being touched fall within a same level range.
`The calibration parameters of the stimulus regions are stored
`as the calibration parameters of the traces and for use when
`sensing each stimulus region in future. For a capacitive touch
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`panel having m traces in the X direction and n traces in the Y
`direction, where m and n are positive integers, if it is desired
`to sense the traces in both the X and Y directions, the calibra
`tion parameters of the disclosed sensing method only requires
`memory space for m+n data; if it uses merely the traces in the
`X direction, the calibration parameters consume only space
`for storing m data; and if it uses merely the traces in the Y
`direction, the calibration parameters consume only space for
`storing n data.
`While the present invention has been described in conjunc
`tion with preferred embodiments thereof, it is evident that
`many alternatives, modifications and variations will be appar
`ent to those skilled in the art. Accordingly, it is intended to
`embrace all Such alternatives, modifications and variations
`that fall within the spirit and scope thereofas set forth in the
`appended claims.
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`US 9,104,2