(12) United States Patent
`Land et al.
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 8,482.544 B2
`Jul. 9, 2013
`
`USOO8482544B2
`
`(54) NEGATIVE PIXEL COMPENSATION
`
`(75) Inventors: Brian Richards Land, Redwood City,
`CA (US); Marduke Yousefpor, San
`S. S. Steven Porter Hotelling,
`an JOSe,
`(US)
`(73) Assignee: Apple Inc., Cupertino, CA (US)
`
`(*) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 732 days.
`
`(21) Appl. No.: 12/500,870
`
`(22) Filed:
`(65)
`
`Jul. 10, 2009
`Prior Publication Data
`US 2011 FOOO6832A1
`Jan. 13, 2011
`an. 13,
`
`(51) Int. Cl
`irokiz/96
`(52) U.S. Cl
`345/174: 345/173: 178/18.06
`USPG
`58) Field fo - - - - - ificati- - - - - S
`h s
`s
`(58) t
`SS cation, Star 174: 178/1801, 1803
`
`(2006.01)
`
`s
`- - - - - - - - - - - - - - - - - - - -
`hhi
`1
`lication file f
`S
`ee application file for complete search history.
`References Cited
`
`s
`
`1 7sf 18 O6
`
`(56)
`
`U.S. PATENT DOCUMENTS
`5,483.261 A
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`6, 2000 Inoue
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`1 1/2001 Westerman et al.
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`3, 2006 Morohoshi
`
`EP
`EP
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`7,184,064 B2
`7,372.455 B2
`7,663,607 B2
`
`2/2007 Zimmerman et al.
`5/2008 Perski et al.
`2/2010 Hotelling et al.
`(Continued)
`FOREIGN PATENT DOCUMENTS
`2 196889 A2
`6, 2010
`2 196889 A3
`6, 2010
`(Continued)
`OTHER PUBLICATIONS
`International Search Report mailed Sep. 14, 2010, for PCT Applica
`tion No. PCT/US2010/041247, four pages.
`(Continued)
`
`Primary Examiner — Amare Mengistu
`Assistant Examiner — Jennifer Zubailo
`(74) Attorney, Agent, or Firm — Morrison & Foerster LLP
`
`ABSTRACT
`(57)
`Negative pixel compensation in a touch sensitive device is
`disclosed. The device can compensate for a negative pixel
`effect in touch signal outputs due to poor grounding of an
`object touching the device. To do so, the device can switch to
`a configuration to measure the grounding condition of the
`
`touching object and use the measurement to compensate the
`touch output values from the device accordingly. In the
`switched configuration, a first set of lines of the device can be
`Switched between a coupling to a stimulation signal input to
`drive the device, a coupling to a capacitance signal output to
`output a signal indicative of the object's grounding condition,
`and a coupling to ground. A second set of lines of the device
`can be coupled to a touch signal output to output a signal
`indicative of the objects touch at the device. In addition or
`alternatively, in the switched configuration, the first set of
`lines of the device can be switched to function as the second
`set of lines and Vice versa. The grounding signal can be
`applied to the touch signal to compensate for the negative
`pixel effect.
`
`24 Claims, 10 Drawing Sheets
`
`MAKENEGATIVEPIXEL
`CONFIGURATION
`
`PERFORMSCAN
`
`-705
`
`-710
`
`--
`CAPTURESENSELNEOUCH
`OUTPUTS8 AUXLARY
`SENSE
`LINE OUTPUS
`
`OETAINS&m
`
`--
`CALCULATERATIOSTO2m
`
`--
`DETERMINE COMPENSATION
`FACTORR
`
`H
`-
`COMPENSATFORNEGATIVE
`PXELEFFECTUSNEGR
`
`DELL EXHIBIT 1016 PAGE 1
`
`DELL EXHIBIT 1016 PAGE 1
`
`

`

`US 8,482.544 B2
`Page 2
`
`U.S. PATENT DOCUMENTS
`2004/O155871 A1
`Perski et al.
`8, 2004
`Baker et al.
`2005/025.9085 A1 11/2005
`Hotelling et al.
`2006, 0026521 A1,
`2, 2006
`Hotelling et al.
`2006/0097991 A1
`5, 2006
`Hotelling
`2006/O197753 A1
`9, 2006
`Hotelling et al. ............. 345,173
`2008. O158167 A1* 7, 2008
`2008, 0208324 A1
`8, 2008
`Glithero et al.
`2009/O16O787 A1* 6, 2009
`Westerman et al. .......... 345,173
`2009/O174676 A1
`T/2009
`Westerman
`2009/017.4688 A1
`T/2009
`Westerman
`Yousefpor
`2010 OO60608 A1
`3, 2010
`Fang ............................. 345,174
`2010, OO97343 A1* 4, 2010
`Gray
`2010, O14911.0 A1
`6, 2010
`2012,0081335 A1
`4, 2012
`Land
`
`FOREIGN PATENT DOCUMENTS
`6, 2011
`2335 140 A1
`EP
`6, 2000
`2000-163031 A
`JP
`11, 2002
`2002-342033. A
`JP
`WO WO-2004/070396 A2
`8, 2004
`WO WO-2004/070396 A3
`8, 2004
`WO WO-2011 (0.05884 A1
`1, 2011
`
`OTHER PUBLICATIONS
`Lee, S.K. et al. (Apr. 1985). "A Multi-Touch Three Dimensional
`Touch-Sensitive Tablet.” Proceedings of CHI: ACM Conference On
`Human Factors in Computing Systems, pp. 21-25.
`Rubine, D.H. (Dec. 1991). “The Automatic Recognition of Ges
`tures. CMU-CS-91-202, Submitted in Partial Fulfillment of the
`Requirements for the Degree of Doctor of Philosophy in Computer
`Science at Carnegie Mellon University, 285 pages.
`Rubine, D.H. (May 1992). “Combining Gestures and DirectManipu
`lation.” CHI '92, pp. 659-660.
`Westerman, W. (Spring 1999). “Hand Tracking, Finger Identifica
`tion, and Chordic Manipulation on a Multi-Touch Surface.” A Dis
`sertation Submitted to the Faculty of the University of Delaware in
`Partial Fulfillment of the Requirements for the Degree of Doctor of
`Philosophy in Electrical Engineering, 364 pages.
`U.S. Appl. No. 12/208,324, filed Sep. 10, 2008, by M. Yousefpor.
`U.S. Appl. No. 12/234,520, filed Sep. 19, 2008, by M.Yousefpor et al.
`Great Britain Search Report mailed Dec. 21, 2011, for GB Patent
`Application No. GB11 19963.5, two pages.
`Non-Final Office Action mailed Mar. 21, 2012, for U.S. Appl. No.
`13/251,049, filed Sep. 30, 2011, 16 pages.
`* cited by examiner
`
`DELL EXHIBIT 1016 PAGE 2
`
`DELL EXHIBIT 1016 PAGE 2
`
`

`

`U.S. Patent
`
`Jul. 9, 2013
`
`Sheet 1 of 10
`
`US 8,482.544 B2
`
`TOUCHSENSOR
`PANEL
`
`te,
`
`E
`
`
`
`SENSELNE
`104
`
`PXEL
`O6
`
`101
`STIMULATION
`SIGNAL
`
`into TOUCH SIGNALS
`
`FIG. 1
`
`DELL EXHIBIT 1016 PAGE 3
`
`DELL EXHIBIT 1016 PAGE 3
`
`

`

`U.S. Patent
`
`Jul. 9, 2013
`
`Sheet 2 of 10
`
`US 8,482.544 B2
`
`TOUCHSENSOR
`PANEL
`
`2,
`
`NEGATIVE
`PXEL
`206c
`
`C
`90
`
`y\\
`
`E.
`
`202a
`
`PXE
`
`G.
`
`Y
`
`CSIG. ACSIG
`2026
`
`
`
`NEGATIVE
`PXEL 6. PIXELId
`-
`206b 2s
`
`
`
`FINGER
`O 2
`
`204a
`SENSE LINE
`
`204b
`
`2040
`
`FIG 2
`
`DELL EXHIBIT 1016 PAGE 4
`
`DELL EXHIBIT 1016 PAGE 4
`
`

`

`U.S. Patent
`
`Jul. 9, 2013
`
`Sheet 3 of 10
`
`US 8,482.544 B2
`
`TOUCHSENSOR
`PANEL
`
`',
`
`DRIVE
`LINE
`
`PXEL
`396
`
`30
`STIMULATION
`SIGNAL
`
`302b
`
`
`
`AUXLIARY
`SENSE LINE
`
`-,-
`318
`NEGATIVE
`PXEL
`EFFECT
`SIGNAL
`
`
`
`304
`SENSE LINE
`N--
`a TOUCH SIGNAL
`FIG. 3
`
`DELL EXHIBIT 1016 PAGE 5
`
`DELL EXHIBIT 1016 PAGE 5
`
`

`

`U.S. Patent
`
`Jul. 9, 2013
`
`Sheet 4 of 10
`
`US 8,482.544 B2
`
`TOUCHSENSOR
`PANEL
`4OO
`N
`
`422SWITCH
`
`402
`DRIVE
`LINE
`
`-, -
`42
`STIMULATION
`SIGNAL INPUT
`- 7-
`49
`NEGATIVEPIXEL
`EFFECT OUTPUT
`- -
`428
`GROUND
`
`FIG. 4
`
`DELL EXHIBIT 1016 PAGE 6
`
`DELL EXHIBIT 1016 PAGE 6
`
`

`

`U.S. Patent
`
`Jul. 9, 2013
`
`Sheet 5 of 10
`
`US 8,482.544 B2
`
`TOUCHSENSOR
`PANEL
`5OO
`
`
`
`LINE
`
`h;
`
`STIMULATION
`SIGNAL
`
`AUXLARY
`SENSE
`LINE
`
`NEGATIVE
`PXEL EFFECT
`SIGNAL
`
`|
`FIG. 5
`
`DELL EXHIBIT 1016 PAGE 7
`
`DELL EXHIBIT 1016 PAGE 7
`
`

`

`U.S. Patent
`
`Jul. 9, 2013
`
`Sheet 6 of 10
`
`US 8,482.544 B2
`
`TOUCH SENSOR
`PANEL
`
`,
`
`SWITCH
`622
`
`
`
`ROWLINE
`
`-606 PIXEL
`
`7
`62
`STIMULATION
`SIGNAL INPUT
`
`619
`NEGATIVE PXEL
`EFFECT OUTPUT
`
`628
`GROUND
`
`
`
`604 COLUMN LINE
`
`
`
`624 SWITCH
`
`62 . i. i.
`
`GROUND
`
`TOUCH
`SIGNAL
`OUTPUT
`
`STIMULATION
`SIGNAL
`INPUT
`
`NEGATIVE
`PXEL
`EFFECT
`OUTPUT
`F.G. 6
`
`DELL EXHIBIT 1016 PAGE 8
`
`DELL EXHIBIT 1016 PAGE 8
`
`

`

`U.S. Patent
`
`Jul. 9, 2013
`
`Sheet 7 of 10
`
`US 8,482.544 B2
`
`
`
`
`
`
`
`
`
`
`
`
`
`MAKENEGATIVEPXEL
`CONFIGURATION
`
`705
`
`PERFORMSCAN
`
`
`
`710
`
`CAPTURESENSE LINE TOUCH
`OUTPUTS & AUXLIARY SENSE
`LINE OUTPUTS
`
`OBTAIN S&Zm
`
`CALCULATERATIO STOZm
`
`DETERMINE COMPENSATION
`FACTORR
`
`COMPENSATE FORNEGATIVE
`PXELEFFECTUSINGR
`
`715
`
`720
`
`725
`
`730
`
`735
`
`DELL EXHIBIT 1016 PAGE 9
`
`DELL EXHIBIT 1016 PAGE 9
`
`

`

`U.S. Patent
`
`Jul. 9, 2013
`
`Sheet 8 of 10
`
`US 8,482.544 B2
`
`745
`
`750
`
`755
`
`760
`
`765
`
`770
`
`775
`
`780
`
`785
`
`790
`
`795
`
`MAKETOUCH CONFIGURATION
`
`PERFORM TOUCH
`DETECTION SCAN
`
`CAPTURE SENSE LINE
`TOUCHOUTPUTS
`
`OBTANZm
`
`MAKE NEGATIVEPXEL
`CONFIGURATION
`
`PERFORMNEGATIVE PIXELSCAN
`
`CAPTUREAUXILARY SENSE
`LINE OUTPUTS
`
`OBTAINS
`
`CALCULATERATO STOZm
`
`DETERMINE COMPENSATION
`FACTORR
`
`COMPENSATE FOR NEGATIVE
`PXELEFFECTUSINGR
`
`F G. 7 B
`
`DELL EXHIBIT 1016 PAGE 10
`
`DELL EXHIBIT 1016 PAGE 10
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`

`

`U.S. Patent
`
`Jul. 9, 2013
`
`Sheet 9 of 10
`
`US 8,482.544 B2
`
`COMPUTING SYSTEM
`8OO
`
`
`
`830
`
`828
`
`832
`
`DISPLAY
`DEVICE
`
`HOST
`PROCESSOR
`
`PROGRAM
`STORAGE
`
`
`
`
`
`
`
`PROCESSOR-802
`SUBSYSTEM
`812
`
`806
`TOUCH
`CONTROLLER
`
`815
`
`CHARGE
`PUMP
`
`84
`
`
`
`STMULATION
`SIGNALS
`86
`
`
`
`
`
`
`
`
`
`808
`CONTROLSIGNALS
`
`TOUCHSENSOR
`PANEL
`TOUCHSIGNALS
`824 CSIG
`
`826 PIXEL
`
`FIG. 8
`
`DELL EXHIBIT 1016 PAGE 11
`
`DELL EXHIBIT 1016 PAGE 11
`
`

`

`U.S. Patent
`
`Jul. 9, 2013
`
`Sheet 10 of 10
`
`US 8,482.544 B2
`
`MOBILE
`TELEPHONE
`
`
`
`DISPLAY
`SENSOR. --936
`PANEL
`
`FIG. 9
`
`
`
`MEDIA
`PLAYER
`1OOO
`
`TOUCH
`SENSORPANEL
`
`DISPLAY
`DEVICE
`1036
`
`
`
`PERSONAL
`COMPUTER
`1100
`
`DISPLAY
`
`TRACKPAD
`1124
`
`DELL EXHIBIT 1016 PAGE 12
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`DELL EXHIBIT 1016 PAGE 12
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`

`

`1.
`NEGATIVE PXEL COMPENSATION
`
`US 8,482,544 B2
`
`FIELD
`
`This relates generally to touch sensitive devices and, more
`particularly, to compensating for negative pixel effects on
`touch sensitive devices.
`
`BACKGROUND
`
`Many types of input devices are presently available for
`performing operations in a computing system, Such as buttons
`or keys, mice, trackballs, joysticks, touch sensor panels,
`touch screens and the like. Touch sensitive devices, such as
`touch screens, in particular, are becoming increasingly popu
`lar because of their ease and versatility of operation as well as
`their declining price. A touch sensitive device can include a
`touch sensor panel, which can be a clear panel with a touch
`sensitive Surface, and a display device Such as a liquid crystal
`display (LCD) that can be positioned partially or fully behind
`the panel so that the touch-sensitive surface can cover at least
`a portion of the viewable area of the display device. The touch
`sensitive device can allow a user to perform various functions
`by touching the touch sensor panel using a finger, stylus or
`other object at a location often dictated by a user interface
`(UI) being displayed by the display device. In general, the
`touch sensitive device can recognize a touch event and the
`position of the touch event on the touch sensor panel, and the
`computing system can then interpret the touch event in accor
`dance with the display appearing at the time of the touch
`event, and thereafter can perform one or more actions based
`on the touch event.
`When the object touching the touch sensor panel is poorly
`grounded, touch output values indicative of a touch event can
`be erroneous or otherwise distorted. The possibility of such
`erroneous or distorted values can further increase when two
`or more simultaneous touch events occur at the touch sensor
`panel.
`
`SUMMARY
`
`10
`
`15
`
`25
`
`30
`
`35
`
`40
`
`This relates to compensating touch signals indicative of a
`touch at a touch sensitive device for errors that can be caused
`by poor grounding of a user or other objects touching the
`device. One such error can be a negative pixel effect, in which
`an apparent negative amount of touch can be sensed by the
`device during multiple simultaneous touches. To compensate
`for this effect, the device can obtain measurements that can be
`used to determine and apply a compensation factor to the
`touch signals. For example, the device can Switch to a con
`figuration for concurrently measuring the grounding condi
`tion of the touching object and the objects touch at the
`device. The device can then calculate the compensation factor
`based on a ratio between the grounding measurement and the
`touch measurement and apply the factor to the touch signals
`to compensate for the negative pixel effect. Alternatively, the
`device can Switch to a first configuration to measure the
`grounding condition of the touching object and to a second
`configuration to measure the objects touch at the device.
`The touch sensitive device can include multiple pixels
`formed by crossings of a first set of lines and a second set of
`lines, where the first set of lines can be drive lines configured
`to drive the device and the second set of lines can be sense
`lines configured to sense a touch at the pixels of the device.
`Alternatively, the first and second sets of lines can switch
`positions so that the first lines function as the sense lines and
`the second lines function as the drive lines. To configure the
`
`45
`
`50
`
`55
`
`60
`
`65
`
`2
`device to compensate for the negative pixel effect, the drive
`and senselines of the device can be switched between various
`coupling states in order to measure the objects touch and
`grounding condition. The coupling states can include a cou
`pling to a stimulation signal input to drive the device, a
`coupling to a capacitance signal output to output a signal
`indicative of the object's grounding condition, a coupling to
`ground, and a coupling to a touch signal output to output a
`signal indicative of the objects touch at the device. The
`device can apply an outputted grounding signal to an output
`ted touch signal to compensate for the negative pixel effect.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 illustrates an exemplary touch sensor panel in a
`normal touch detection configuration according to various
`embodiments.
`FIG. 2 illustrates an exemplary negative pixel effect in a
`touch sensor panel receiving multiple simultaneous touches
`of poorly grounded fingers according to various embodi
`mentS.
`FIG. 3 illustrates an exemplary touch sensor panel in a
`negative pixel effect detection configuration according to
`various embodiments.
`FIG. 4 illustrates exemplary switching circuitry of a touch
`sensor panel according to various embodiments.
`FIG. 5 illustrates another exemplary touch sensor panel in
`a negative pixel effect detection configuration according to
`various embodiments.
`FIG. 6 illustrates exemplary switching circuitry of a touch
`sensor panel according to various embodiments.
`FIG. 7A illustrates an exemplary method for compensating
`for negative pixel effects on a touch sensor panel according to
`various embodiments.
`FIG. 7B illustrates another exemplary method for compen
`sating for negative pixel effects on a touch sensor panel
`according to various embodiments.
`FIG. 8 illustrates an exemplary computing system that can
`compensate for negative pixel effects according to various
`embodiments.
`FIG. 9 illustrates an exemplary mobile telephone that can
`compensate for negative pixel effects according to various
`embodiments.
`FIG. 10 illustrates an exemplary digital media player that
`can compensate for negative pixel effects according to vari
`ous embodiments.
`FIG. 11 illustrates an exemplary personal computer that
`can compensate for negative pixel effects according to vari
`ous embodiments.
`
`DETAILED DESCRIPTION
`
`In the following description of various embodiments, ref
`erence is made to the accompanying drawings which form a
`part hereof, and in which it is shown by way of illustration
`specific embodiments which can be practiced. It is to be
`understood that other embodiments can be used and structural
`changes can be made without departing from the scope of the
`various embodiments.
`This relates to compensating for a negative pixel effect in a
`touch sensitive device due to poor grounding of a user or other
`objects touching the device. The device can be configured to
`concurrently measure a touching object's grounding condi
`tion and the objects touch at the device. In addition or alter
`natively, the device can be configured to sequentially measure
`the touching object's grounding condition and the objects
`touch at the device. The device can calculate a compensation
`
`DELL EXHIBIT 1016 PAGE 13
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`DELL EXHIBIT 1016 PAGE 13
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`

`US 8,482,544 B2
`
`3
`factor based on a ratio between the grounding measurement
`and the touch measurement and use the factor to compensate
`for erroneous or distorted touch output values from the
`device. Various components of the device can be switchably
`configured according to the particular configuration.
`In some embodiments, a configuration can include one or
`more drive lines of the device being switched to couple to a
`stimulation signal to drive the device, other drive lines being
`Switched to couple to a sensor to measure a grounding con
`dition of the touching object, the remaining drive lines being
`Switched to couple to ground, and one or more sense lines of
`the device being Switched to couple to a sensor to measure a
`touch at the device. In this configuration, the device can
`concurrently measure the grounding condition and the touch
`at the device. Alternatively, the device can just measure the
`grounding condition.
`In some embodiments, another configuration can include
`one or more of the drive lines being switched to couple to a
`stimulation signal to drive the device, the other drive lines
`being Switched to couple to ground, and one or more sense
`lines being Switched to couple to a sensor to measure a touch
`at the device. In this configuration, the device can measure the
`objects touch.
`In some embodiments, another configuration can include
`the drive lines of the device being switched to function as the
`sense lines of the device and vice versa, where one or more
`drive lines can be switched to couple to a stimulation signal to
`drive the device, other drive lines can be switched to couple to
`a sensor to measure a grounding condition, the remaining
`drive lines can be Switched to couple to ground, and the sense
`lines can be switched to couple to ground. In this configura
`tion, the device can measure the grounding condition.
`The ability to measure a negative pixel effect in a touch
`sensitive device can advantageously provide more accurate
`and faster touch detection by not having to repeat measure
`ments Subject to poor grounding conditions. Power savings
`can also be realized by not having to repeat measurements.
`Additionally, the device can more robustly adapt to various
`grounding conditions of a user or other object.
`The terms “poorly grounded,” “ungrounded,” “not
`grounded,” “not well grounded,” “improperly grounded.”
`"isolated,” and “floating can be used interchangeably to refer
`to poor grounding conditions that can exist when an object is
`not making a low impedance electrical coupling to the ground
`of the touch sensitive device.
`The terms “grounded,” “properly grounded,” and “well
`grounded can be used interchangeably to refer to good
`grounding conditions that can exist when an object is making
`a low impedance electrical coupling to the ground of the
`touch sensitive
`Although various embodiments can be described and illus
`trated herein in terms of mutual capacitance touch sensor
`panels, it should be understood that the various embodiments
`are not so limited, but can be additionally applicable to self
`capacitance sensor panels, both single and multi-touch sensor
`panels, and other sensors in which single stimulation signals
`can be used to generate a touch signal and in which multiple
`simultaneous stimulation signals can be used to generate a
`composite touch signal. Moreover, although various embodi
`ments can be described and illustrated herein in terms of
`double-sided ITO (DITO) touch sensor panels, it should be
`understood that the various embodiments can be also appli
`cable to other touch sensor panels configurations, including
`opaque touch sensor panels, such as configurations in which
`the drive and senselines can beformed on different substrates
`or on the back of a cover glass, and configurations in which
`the drive and sense lines can be formed on the same side of a
`
`40
`
`45
`
`4
`single Substrate. Furthermore, although various embodiments
`can be described and illustrated herein in terms of rows and
`columns of conductive lines orthogonal to each other, it
`should be understood that the various embodiments are not so
`limited, but additionally encompass other geometric configu
`rations, such as concentric and radial lines of a polar-coordi
`nate configuration, diagonal lines of an oblique configuration,
`non-orthogonal lines, and so on.
`FIG. 1 illustrates an exemplary touch sensor panel in a
`normal touch detection configuration according to various
`embodiments. In the example of FIG. 1, touch sensor panel
`100 can include an array of pixels 106 that can be formed at
`the crossing points of row lines 102 and column lines 104.
`Each pixel 106 can have an associated mutual capacitance
`Csig 114 formed between the crossing row lines 102 and
`column lines 104. As illustrated in FIG. 1, the row lines 102
`can function as drive lines and the column lines 104 can
`function as sense lines, where the drive lines can be stimu
`lated by stimulation signals 101 provided by drive circuitry
`(not shown) that can include an alternating current (AC)
`waveform and the sense lines can transmit touch or sense
`signals 103, indicative of a touch at the panel 100, to sense
`circuitry (not shown) that can include a sense amplifier for
`each sense line.
`To sense a touch at the panel 100, in some embodiments,
`multiple drive lines 102 can be substantially simultaneously
`stimulated by the stimulation signals 101 to capacitively
`couple with the crossing sense lines 104, thereby forming a
`capacitive path for coupling charge from the drive line to the
`sense line. The crossing sense lines 104 can output signals
`representing the coupled charge or current. While some drive
`lines 102 are being stimulated, the other drive lines can be
`coupled to ground. In other embodiments, each drive line 102
`can be sequentially stimulated by the stimulation signals 101
`to capacitively couple with the crossing sense lines 104.
`which can output signals representing the coupled charge or
`current, while the other drive lines can be coupled to ground.
`In still other embodiments, there can be a combination of
`multiple drive lines 102 being substantially simultaneously
`stimulated and single drive lines being sequentially stimu
`lated.
`When a well grounded user's finger (or other object)
`touches the panel 100, the finger can cause the capacitance
`Csig 114 to reduce by an amount ACsig at the touch location.
`This capacitance change ACsig can be caused by charge or
`current from the stimulated drive line 102 being shunted
`through the touching finger to ground rather than being
`coupled to the crossing sense line 104 at the touch location.
`The touch signals 103 representative of the capacitance
`change ACsig can be transmitted by the sense lines 104 to the
`sense circuitry for processing. The touch signals 103 can
`indicate the pixel where the touch occurred and the amount of
`touch that occurred at that pixel location.
`When a poorly grounded user's finger (or other object)
`touches the panel 100, a finger capacitance Cfd to the stimu
`lated drive line 102, a finger capacitance Cfs to the crossing
`sense line 104 at the touch location, and a finger capacitance
`Cgnd to user ground can form a secondary capacitive path for
`coupling charge from the drive line to the sense line. Some of
`the charge generated by the stimulated drive line 102 and
`transmitted through the finger can be coupled via the second
`ary capacitive path back into the crossing sense line 104.
`rather than to ground. As a result, instead of the capacitance
`Csig 114 of the pixel at the touch location being reduced by
`ACsig, Csig may only be reduced by (ACsig-Cneg), where
`Cneg can represent a so-called “negative capacitance' result
`ing from the charge coupled into the crossing sense line due to
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`the finger's poor grounding. The touch signals 103 can still
`generally indicate the pixel where the touch occurred but with
`an indication of a lesser amount of touch than actually
`occurred.
`When multiple poorly grounded user's fingers (or other
`objects) simultaneously touch the panel 100 at different loca
`tions, the first finger capacitances Cfd and Cfs can form as
`described above at the first finger's touch location, i.e., a
`crossing of a stimulated drive line 102 and a sense line 104.
`Some of the charge from the first finger can also be coupled
`through the second finger back into the panel 100 so that the
`second finger capacitances Cfd and Cfs can form at the sec
`ond fingers touch location, i.e., at a crossing of an unstimu
`lated drive line 102 and a sense line 104. The capacitance to
`user ground Cgnd can also form as described above. As a
`result, the touch signals 103 can indicate the pixel where the
`first finger touched but with an indication of a lesser amount
`of touch than actually occurred, as described previously. The
`touch signals 103 can also indicate a phantom touch at the
`pixel formed by the crossing of the stimulated drive line 102
`and the second finger's sense line 104 and/or at the pixel
`formed by the crossing of the second fingers unstimulated
`drive line and the first finger's sense line. The touch signals
`103 can indicate an apparent negative amount of touch at
`these pixels, due to the charge coupled back into the panel by
`the second finger. This can be the so-called “negative pixel
`effect.
`Similarly, when the drive line 102 at the touch location of
`the second finger is stimulated, the second finger capacitances
`Cfd and Cfs can form as described above at that touch loca
`tion. Some of the charge from the second finger can also be
`coupled through the first finger back into the panel 100 so that
`the first finger capacitances Cfd and Cfs can form at the first
`fingers touch location, i.e., at the crossing of its now
`unstimulated drive line 102 and a sense line 104. The capaci
`tance to user ground Cgnd can also form. As a result, the touch
`signals 103 can indicate the pixel where the second finger
`touched but with an indication of a lesser amount of touch
`than actually occurred, as described previously. The touch
`signals 103 can also indicate a phantom touch at the pixel
`formed by the crossing of the stimulated drive line 102 and the
`first finger's sense line 104 and/or at the pixel formed by the
`crossing of the first finger's unstimulated drive line and the
`second finger's sense line and an apparent negative amount of
`touch at these pixels, due to the charge coupled back into the
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`panel 100 by the first finger, thereby generating the negative
`pixel effect.
`As an alternate embodiment to the row lines as drive lines
`and the column lines as sense lines described previously, the
`row lines 102 can function as sense lines and the column lines
`104 can function as drive lines. When well grounded or
`poorly grounded fingers touch the panel, the column lines can
`perform as the drive lines described above and the row lines
`can perform as the sense lines described above.
`FIG. 2 illustrates an exemplary negative pixel effect in a
`touch sensor panel receiving multiple simultaneous touches
`of poorly grounded fingers according to various embodi
`ments. As illustrated in FIG. 2, the row lines 202 can function
`as drive lines and the column lines 204 can function as sense
`lines. In other embodiments, the row lines 202 can function as
`sense lines and the column lines 204 can function as drive
`lines. In the example of FIG. 2, a poorly grounded first finger
`(symbolically illustrated by a circle and identified as “finger
`1') can touch at pixel 206a of touch sensor panel 200 and a
`poorly grounded second finger (symbolically illustrated by a
`circle and identified as “finger 2) can touch at pixel 206b of
`the panel. When drive (or row) line 202a of the panel 200 is
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`stimulated, the capacitance along a first path between the
`drive line 202a and sense (or column) line 204a can be (Csig
`ACsig). Because the fingers are poorly grounded, a second
`capacitive path can form between the drive line 202a and the
`sense line 204a, having capacitances Cfd (between the drive
`line 202a and the first finger) and Cfs (between the senseline
`204a and the first finger), and a third capacitive path can form
`via the second finger between the drive line 202c and the
`sense line 204b, having capacitances Cfd (between the drive
`line 202c and the second finger) and Cfs (between the sense
`line 204b and the second finger). A capacitance Cgnd can also
`form between the fingers and user ground. The capacitances
`can be due to charge or current acquired by the first finger
`from the stimulated drive line 202a being coupled back into
`the panel 200 at pixels 206a and 206b, rather than being
`shunted to ground. Similar capacitances can form at the first
`and second fingers when drive line 202c is stimulated. As a
`result, pixels 206c and 206d, which are proximate to the
`touched pixels 206a and 206b but did not receive touches, can
`indicate a negative amount of touch (“negative pixels).
`Accordingly, detecting the negative pixel effect and com
`pensating the touch signals for the effect can improve touch
`sensing of the touch sensor panel in poor grounding condi
`tions.
`FIG. 3 illustrates an exemplary touch sensor panel in a
`negative pixel effect detection configuration according to
`various embodiments. Touch sensor panel 300 of FIG. 3 can
`be similar to the touch sensor panel 100 of FIG. 1 with the
`following additions. Rather than all unstimulated drive (or
`row) lines 302b coupling to ground, some unstimulated drive
`lines 302c can switchably couple to sensors (not shown) to
`detect a capacitance Cfd on these drive lines that can contrib
`ute to the negative pixel effect. The capacitance can be due to
`charge or current coupled into these drive lines from poorly
`grounded fingers touching the panel 300 and can be represen
`tative of the user's grounding condition. The sensors for
`sensing the capacitances Cfd can include sense amplifiers.
`These drive lines can be switched and can change function to
`become auxiliary sense lines 302c.
`To detect the capacitances Cfd, multiple drive lines 302 can
`be substantially simultaneously stimulated by the stimulation
`signals 301 (as in drive line 302a), some of the unstimulated
`drive lines can be coupled to ground (as in drive line 302b),
`and others of the unstimulated drive lines can be switched to
`function as auxiliary sense lines coupled to sensors to sense
`negative pixel effect signal 318, indicative of the capacitances
`Cfd (as in drive lines 302c). An auxiliary sense line 302c can
`form a capacitance Cfd from a second (third, fourth, or fifth)
`poorly grounded finger touching at that auxiliary sense line,
`thereby allowing charge or current to couple with that auxil
`iary sense line to form the capacitance Cfd, as described
`previously. Conversely, when a finger is not touching at an
`auxiliary sense line 302c, that auxiliary sense line may not
`form a capacitance Cfd to be sensed. The negative pixel effect
`signals 318 can be transmitted to sense circuitry for further
`processing in compensating for the negative pixel effect. In
`some embodiments, touch signals 303 from the sense lines
`304 can be transmitted to sense circuitry for further process
`ing. As such, both touch signals 303 and negative pixel effect
`signals 318 can be captured concurrently. In some embodi
`ments, touch signals 303 from the sense lines 304 can be
`transmitted to ground.
`In other embodiments, each drive line 302 can be sequen
`tially stimulated by the stimulation signals 301 to capacitively
`couple with the crossing sense lines 304, which can output
`signals representing the coupled charge or current, while the
`other drive lines can be either switched to function as auxil
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`US 8,482,544 B2
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`iary sense lines or coupled to ground. In still other embodi
`ments, there can be a combination of multiple drive lines 302
`being Substantially simultaneously stimulated and single
`drive lines being sequentially stimulated.
`Although FIG. 3 illustrates the row lines as drive lines and 5
`auxiliary sense lines and the column lines as sense lines, it is
`to be understood that the row lines can function as sense lines
`and the column lines can function as drive lines and auxiliary
`sense lines.
`Selection of which unstimulated drive lines 302 to use as 10
`auxiliary sense lines 302c can be made to insure that a suffi
`cient number of quality capacitance Cfd measurements are
`captured so that the negative pixel effect can be adequately
`compensated for