1
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`VWGoA - Ex. 1011
`Volkswagen Group of America, Inc., Petitioner
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`U.S. Patent
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`Feb. 1, 1994
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`Sheet 1 of 5
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`5,283,559
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`2
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`

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`U.S. Patent
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`Feb. 1, 1994
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`Sheet 2 of 5
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`5,283,559
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`FIG. 2 '
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`TOUCH
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`SCREEN
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`CONTROLLER
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`3
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`U.S. Patent
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`Feb. 1,1994
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`Sheet 3 of5
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`-
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`5,283,559
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`FIG. 3
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`4
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`

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`U.S. Patent
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`Feb. 1,1994
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`Sheet 4 of5
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`5,283,559
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`FIG. 4
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`TO
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`SELECTING
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`MEANS 38
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`5
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`

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`U.S. Patent
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`Feb. 1, 1994
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`Sheet 5 of 5
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`5,283,559
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`FIG. 5
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`SWlTCH
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`CONTACTS
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`TO
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`CALIBRATION
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`REFERENCE
`60
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`FIRST
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`DECODER
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`52
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`LATCH
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`54
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` CONTROLLER
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` SECOND
`DECODER
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`5,283,559
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`AUTOMATIC CALIBRATION OF A CAPACITIVE
`TOUCH SCREEN USED WITH A FIXED ELEMENT
`FLAT SCREEN DISPLAY PANEL
`
`FIELD OF INVENTION
`
`The field of the invention is touch or pressure sensi-
`tive panels wherein the location, in a work area, of an
`applied force is employed as data in a computer system.
`The work area is usually the face of a touch sensitive
`panel overlaying a display screen and particularly, the
`field of the invention is directed to a means of automati-
`
`cally calibrating such an input device.
`BACKGROUND OF THE INVENTION
`
`Touch sensitive panels overlaying a display terminal
`screen are well known. The terminal responds to a
`touch at any location within a work area on the touch
`sensitive panel and identifies the location of the touched
`section. Such a system typically employs a capacitive
`sensing technique. Capacitive sensing systems typically
`have a controller which continually transmits a scan-
`ning signal across the touch panel and samples the work
`area until a touch is detected. When an area on the
`
`touch sensitive panel is touched by a user, the capaci-
`tance of the user’s body is added to the circuit. The
`controller senses the resulting change in capacitance
`and identifies the specific situs touched.
`As the reliability of touch sensitive input devices has
`improved, and diversity of application software ex-
`panded, touch sensitive devices, as a method of input,
`should be expected to be more widely used since no
`training is required to learn how to use such input de-
`vices. Thus, the computer user is not required to be a
`proficient typist or to know how to use an input device
`or computer. The hardware configuration is one that
`may be used without an alternate input device, such as
`a keyboard, offering flexibility in terms of space and
`portability. Applications using this sort of touch sensi-
`tive input device already include, and certainly are not
`limited to, diagnostic analysis, retail point of sale termi-
`nals, simulated aircraft flight controls, locator or infor-
`mational displays, interactive educational systems, ma-
`chine control, or keyboardless entry systems.
`Capacitive touch screen devices are sensitive to
`changes caused by component temperature, component
`age, and stray capacitances. The devices must therefore
`be calibrated before initial use and periodically thereaf-
`ter in order to maintain accuracy. The calibration pro-
`cess typically used with prior art technology involves
`displaying a mark in the active video area of the display
`screen, asking the user to touch the calibration mark as
`viewed on the overlaying touch sensitive panel, and
`then having an internal touch controller read and store
`touch position information. This is then repeated typi-
`cally 2 to 8 times. The results of the calibration measure-
`ments are quantified by the touch controller as devia-
`tions from a standard, or otherwise as a set of correction
`factors, and are stored within the touch controller cir-
`cuitry. After calibration, the touch controller automati-
`cally applies the correction factors to each new touch
`so that the coordinates sent to the host system are as
`accurate as can possibly be made. However, this pro-
`cess has the undesired step of external operator inter-
`vention in order to perform calibration.
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`2
`A need thus exists for an apparatus which provides a
`means to automatically calibrate a touch sensitive panel
`used in conjunction with a fixed element display system.
`OBJECTS OF THE INVENTION
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`An object of the present invention is to provide an
`apparatus to automatically calibrate a touch sensitive
`panel used in conjunction with a fixed element display
`system.
`Another object of the present invention is to provide
`an apparatus to automatically calibrate a touch sensitive
`panel used in conjunction with a fixed element display
`system periodically during active use.
`Still another object of the present invention is to
`provide an apparatus to automatically calibrate a touch
`sensitive panel used in conjunction with a fixed element
`display system after extended periods of non-use.
`A further object of the present invention is to provide
`an automatic touch screen calibration method which
`requires no operator contact or initiation.
`SUMMARY OF THE INVENTION
`
`The touch sensitive input device according to the
`present invention includes a fixed element display, a
`touch sensitive panel and a touch screen controller. The
`touch sensitive panel overlays the fixed element display
`in such a way that an image and/or target points are
`viewable through the touch sensitive panel. Further, a
`touch may be selectively applied to any location on the
`touch sensitive panel. The location or coordinates of an
`applied touch may be within a field, or in response to a
`choice, on the image provided on the underlying fixed
`element display and further serve as a method of data
`input or interactive use.
`The touch screen controller provides a means for
`translating the touch situs on the touch sensitive panel
`to an indicated coordinate on the fixed element display.
`The touch screen controller further provides a means
`for correcting the alignment of the touch sensitive panel
`with the fixed element display. As to this alignment
`correction means, the touch screen controller corrects,
`or otherwise adjusts, any misalignments between the
`touch situs or coordinates on the touch sensitive panel
`and the target situs or coordinates on the fixed element
`display.
`The invention uses calibration contacts either ce-
`mented to the surface of the capacitive touch sensitive
`panel or embedded into the product housing that will
`make contact with the surface of the touch sensitive
`panel when assembled. The invention further provides a
`means of selecting an individual calibration contact for
`grounding or otherwise connecting to a resistive, capac-
`itive, or inductive load. The selecting means is automat-
`ically enabled periodically during use, or during ex-
`tended periods of non-use. In so doing, the calibration
`contact and load may simulate a resistive, capacitive, or
`inductive load that otherwise would be introduced by
`an operator during a manual calibration procedure. As
`a result, the invention provides a completely automatic
`calibration by grounding, or otherwise selecting, indi-
`vidual calibration contacts with all the measurements
`required to compute correction factors.
`BRIEF DESCRIPTION OF DRAWINGS
`
`FIG. 1 illustrates the arrangement of the display
`screen, touch sensitive panel, and transducers.
`FIG. 2 is a front view of a touch sensitive panel in
`accordance with the .present invention.
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`FIG. 3 is a partial side view of the display terminal,
`illustrating a calibration contact embedded in the touch
`screen enclosure.
`FIG. 4 is a partial top view of the display screen,
`illustrating a calibration contact cemented to the touch
`sensitive panel.
`FIG. 5 is a block diagram of the selection means in
`accordance with the present invention.
`DETAILED DESCRIPTION OF THE
`INVENTION
`
`The assembly in FIG. 1 is used in a touch sensitive
`display terminal. It includes a display unit 12 having a
`display screen 14. The illustrated display unit 12 is a
`fixed element display terminal and accordingly the dis-
`play screen 14 is the face of the fixed element display
`terminal. An optically transparent touch sensitive panel
`16 is affixed to the terminal over the display screen 14 so
`that the screen is visible through the touch panel. The
`touch sensitive panel 16 has an electrically conductive
`coating 18 (as shown in FIG. 3) over its entire surface.
`The conductive coating is unpattemed in that it extends
`continuously over the entire display screen 14 or over
`whatever portion thereof is to display user selectable
`items.
`
`Four transducers 20, 22, 24, and 26 are affixed to the
`touch sensitive panel 16 and connected electrically to
`the conductive coating 18. The transducers 20 and 22
`are at the opposite, horizontally separated, peripheral
`side edges of the touch sensitive panel and are elongated
`to extend along the touch sensitive panel edges opposite
`to and parallel with one another. The other pair of
`transducers 24 and 26 likewise are vertically spaced
`apart at opposite peripheral side edges of the touch
`sensitive panel opposite and parallel with one another.
`When the touch screen 16 is mounted and calibrated,
`the transducers (20-26) are attached to the touch sensi-
`tive panel 16 at fixed locations relative to the terminal
`screen 14 so that the determination of a location on the
`touch sensitive panel 16 relative to the four transducers
`20-26 corresponds in a known manner to a location on
`the display terminal screen 14. Therefore, by determin-
`ing the location on the touch sensitive panel 16, a corre-
`sponding determination is made of the location on the
`display screen 14. FIG. 2 further illustrates the arrange-
`ment of the touch sensitive panel 16, transducers 20-26,
`and a touch screen controller 30 for providing a means
`for translating the physical touch situs on the touch
`sensitive panel 16 to an indicated coordinate on the.
`fixed element display, as hereinafter described.
`The method of determining X and Y coordinates for
`a touch situs on the touch sensitive panel 16 is disclosed,
`for example,
`in U.S. Pat. No. 4,680,429 and hereby
`incorporated by reference. In U.S. Pat. No. 4,680,429, a
`function generator or signal source (not shown) gener-
`ates an alternating current voltage touch panel scanning
`signal. The signal is amplified and applied to the pri-
`mary winding of a touch panel driving transformer (not
`shown). The amplified signal drives the secondary
`winding of the transformer and establishes an altemat-
`ing current voltage across the secondary winding of the
`transformer. A multiplexer or switching circuit (not
`shown) applies panel scanning signals from the outputs
`of the secondary winding of the driving transformer to
`selected transducers (20-26). In response to these scan-
`ning signals, panel output or touch current signals are
`generated at the center tap of the transformer when the
`touch sensitive panel is touched. The touch current
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`4
`signals are processed by a panel output signal means,
`filtered, rectified, integrated, and digitized. A micro-
`processor, for example, then computes the touch loca-
`tion and other information from the touch current sig-
`nals. The microprocessor (not shown) interacts with the
`host computer (not shown) which is connected to the
`display unit 12. For example, the host computer may
`cause selected information to be displayed on the screen
`14. Also, the computer may change the displayed infor-
`mation as determined by software in the computer,
`depending upon the location on the touch sensitive
`panel 16 which is touched by the user.
`FIG. 3 shows a side view of a partially disassembled
`portion of the present invention. The optically transpar-
`ent touch sensitive panel 16 overlays, and is affixed to,
`the display screen 14. The touch sensitive panel 16 has
`an electrically conductive coating 18 over its entire
`surface or whatever portion of the screen 14 which is
`used to display user-selectable items. Also shown is one
`of the transducers 20 (as representative) affixed to the
`touch sensitive panel 16. A calibration contact 32 may
`be either cemented to the surface of a capacitive touch
`sensitive panel, or embedded between an insulating
`enclosure 34 and touch sensitive panel 16, making
`contact with the surface of the touch sensitive panel
`when assembled. In either embodiment, the insulating
`enclosure 34 and a gasket or seal 36 are provided to
`electrically insulate the touch sensitive panel 16 and
`calibration contact 32 from undesired external sources
`or stray capacitance over the entire perimeter of the
`touch sensitive panel 16. Further, an insulated conduc-
`tor 38 is provided for each calibration contact so as to
`provide a single point of contact between any calibra-
`tion contact 32 and a selection means. The selection
`means may be a set of electromechanical or solid state
`relays and control logic which allows a desired calibra-
`tion contact 32 to make electrical contact to a reference
`60 (FIG. 5) by changing a set of control lines.
`Referring to FIG. 4, the display screen 14 offers an
`active video display area 42 as well as an inactive dis-
`play area 44 about the periphery of the active video
`display area 42. The active display area 42 comprising
`the area of the screen 14 which is used to view data or
`information displayed by the host system (not shown).
`In the preferred embodiment, each calibration contact
`32 is kept outside the active video area 42 so that a
`calibration contact 32 and conductor 38 leading to it
`does not interfere with the user’s view of the active
`video display area 42.
`Referring to FIG. 5, a selection means employing a
`microcontroller 50, first decoder 52, latch 54, second
`decoder 56 and analog switch 58 are connected to each
`calibration contact 32. The switch 58 employs, in effect,
`an independently operable contact for each calibration
`contact 32. The contacts may be a relay or solid state
`device such as a field effect transistor (FET) switch.
`The operation of the contacts is controlled by a signal
`from the first decoder 52. The signal which controls the
`individual contacts of the switch 58 is generated by the
`microcontroller 50 and applied to a data bus 51. The
`microcontroller’s circuitry places the desired data value
`on the data bus 51, a specified I/O address to the ad-
`dress bus 53, and a control signal to the control bus 55
`to indicate that a memory write or I/O cycle is taking
`place. The latch 54 allows the microcontroller 50 to
`store the signal applied to the data bus 51 by executing
`a memory write, or output,
`instruction. The second
`decoder 56, produces a latching pulse at the appropriate
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`time (upon proper control signal) to indicate that the
`data bus value should be stored in latch 54, thereby
`allowing the microcontroller to perform other func-
`tions while a desired state of the switch 58 contacts is
`maintained. In an alternate embodiment, the decoder 52 5
`may be eliminated and the individual contacts of the
`switch 58 may be controlled directly through latch 54.
`During calibration, when any of the contacts of the
`switch 58 are closed,
`the corresponding calibration
`contact 32 bonded to the surface of the touch sensitive
`screen 16 is electrically connected to a reference 60.
`The reference 60 provides a means for grounding, or
`otherwise connecting, the calibration contact 32 to a
`resistive, capacitive, or inductive load. The nature of
`the reference 60 potential is one that simulates a touch 15
`or force applied to the touch sensitive screen 16.
`When the touch screen controller 30 makes a touch
`screen measurement with the reference 60 electrically
`connected to the touch screen, it will arrive at a differ-
`ent result than it would have if the reference 60 had not
`been applied. Therefore, by connecting the reference 60
`and making a measurement of the indicated coordinates,
`the touch screen controller 30 is able to determine the
`effect of a simulated touch having specific, known coor-
`dinates on the touch screen. After each of the calibra-
`tion contacts 32 has been selected, a calibration correc-
`tion factor is developed based on the difference between
`the indicated coordinates and corresponding known
`coordinates for each calibration contact 32. The rela-
`tionship between the indicated coordinates and known
`coordinates is stored in the touch screen controller 30
`and applied as a correction factor.
`the
`In the preferred embodiment of the invention,
`selection means is placed under the control of the touch
`screen controller 30. The calibration process may begin
`at any time, without explicit intervention of the user or
`host computer. Typically, an automatic recalibration
`may be done each time the system is powered up, at
`periodic intervals during use (based upon a timer func-
`tion within the touch screen controller 30), or after
`extended periods of inactivity. In so doing, the inven-
`tion provides a completely automatic calibration proce-
`dure by grounding (or otherwise selecting) individual
`calibration contacts with all the measurements required
`to compute correction factors.
`If a user should happen to touch the screen while the
`recalibration process is taking place it will result in a
`new set of parameters which are drastically different
`from the desired set. The touch screen controller 30 is
`programmed to compare the difference between old
`and new parameters to a preset threshold and, finding
`that the new values are significantly different, would
`reject them and attempt to recalibrate itself at a later
`time. Repeated failures to recalibrate would be reported
`as a potential hardware failure.
`While the invention has been described above in con-
`nection with a preferred embodiment therefore as illus-
`trated by the drawings, those of skill in the art will
`readily recognize alternative embodiments of the inven-
`tion can be easily produced which do not depart from
`the spirit and scope of the invention as defined in the
`following claims.
`We claim:
`1. An automatic calibrating touch screen apparatus,
`for introducing data into a data processing device, said
`data being indicative of the location of a localized touch
`applied at a touch situs, comprising:
`a fixed element display;
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`a touch sensitive panel overlaid on said fixed element
`display, said touch sensitive panel having an elec-
`trically conductive coating;
`at least one calibration contact affixed to said touch
`sensitive panel on said electrically conductive coat-
`ing;
`means for controlling a translation of a set of touch
`coordinates to a set of target coordinates utilizing a
`correction factor;
`means, responsive to said controller means, for select-
`ing at least one of said calibration contacts, and for
`generating said correction factor;
`a reference, selectable by said selecting means, ap-
`plied to said calibration contact;
`an insulated wire for each said calibration contact, a
`first end of said wire terminating at said calibration
`contact on said touch sensitive panel, a second end
`of said wire terminating at said selecting means.
`2. The device as in claim 1, further comprising:
`a plurality of transducers, disposed on the front of
`said touch sensitive panel, for converting a physi-
`cal touch to an electrical signal.
`3. The device as in claim 1:
`an insulating enclosure for containing said touch sen-
`sitive panel; and
`a gasket interposed between the front of said touch
`sensitive panel and said insulating enclosure.
`4. Thedevice as in claim 2, wherein:
`said touch sensitive panel further comprises an active
`video area and an inactive video area, wherein said
`calibration contact
`is interposed in said inactive
`video area.
`‘
`5. The device as in claim 4, wherein:
`said selecting means is enabled periodically during
`active use.
`6. The device as in claim 4, wherein:
`said selecting means is enabled periodically during
`periods of non-use.
`7. An automatic calibrating touch sensitive input
`device having a fixed element display, a touch sensitive
`panel overlaid thereon, comprising:
`means for controlling the translation of the location
`of a touch situs on said touch sensitive panel with a
`corresponding target situs on said fixed element
`display to generate a set of target coordinates, said
`controller means including a correction factor;
`at least one calibration contact on said touch sensitive
`panel, each said calibration contact having a corre-
`sponding set of known coordinates on said fixed
`element display, and means for selecting any said
`calibration contact to simulate a touch applied to
`the front of said touch sensitive panel, said selec-
`tion means further generating said correction fac-
`tor to correct any variance between the location of
`any said calibration contact and said corresponding
`set of known coordinates.
`8. The device as in claim 7, further comprising:
`a plurality of transducers, disposed on the front of
`said touch sensitive panel, for converting a physi-
`cal touch to an electrical signal.
`9. The device as in claim 8, wherein:
`said touch sensitive panel further comprises an active
`video area and an inactive video area, wherein said
`calibration contact
`is interposed in said inactive
`video area.
`10. The device as in claim 9, further comprising:
`an insulated wire for each said calibration contact,
`said insulated wire having a first end and a second
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`end, the first end of said wire terminating at said
`calibration contact, the second end of said wire
`terminating at said selecting means.
`11. The device as in claim 9 further comprising:
`' an insulating enclosure for containing said touch sen-
`siiive panei; and
`a gasket interpolsed cbetviéeen U118 front olf said touch
`sensitive
`ane an sai
`insu atin enc osure.
`12‘-1-he devlice as in claim 10’ which
`said selecting means is enabled periodically during 10
`active use.
`13. The device as in claim 10, wherein:
`said selecting means is enabled periodically during
`.
`penods of n°n'use'
`14. A method for providing calibration information
`to a touch sensitive input device having a touch screen
`controller, which translates the location of a touch situs
`to a target situs having a set of target coordinates on a
`fixed element flat screen display, said method compris- 20
`ing the steps of:
`selecting a calibration contact from a plurality of
`known
`calibration
`contacts,
`said
`calibration
`contact having a set of known coordinates;
`providing a simulated touch by completing an‘elec'tri- 25
`031 Comaet between the Selected C311P1'_3t1°fl
`contact and a reference, said step of providing a
`simulated touch further providing a set of indicated
`touch coordinates;
`_
`establishing a correction factor to align said indicated 30
`touch coordinates with said known coordinates,
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`for each said known calibration contact selected,
`and
`
`providing said correction factor to said touch screen
`controller.
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`_
`is per-
`
`15- The method 35_i“ Claim ‘Ma “fhereini
`the step of selecting a calibration contact
`16f‘3l1::‘e°‘13_lnEflfgljd:3£lYc‘il;TI;ln§43C£}‘;’:r:;e:
`,
`‘
`'
`'
`is per-
`the step of selecting a calibration contact
`formed penodlcany dum.1g penodfs of .n°n'use'
`17_.'A method for automatically calibrating a touch
`sensitive input device having a touch screen controller,
`Sald mefliod cqmpnsmg the Steps of:
`.
`.
`providing a simulated touch by completing an electri-
`cal contact between a calibration contact, having a
`set of known coordinates, and a reference, said step
`of providing a simulated touch further providing a
`set of indicated touch coordinates;
`establishing a correction factor to align the location
`of said set of indicated touch coordinates with the
`location of said set of known coordinates, for each
`said known calibration contact selected, and
`providing said correction factor to said touch screen
`controller.
`
`13_ The method as in claim 17, wherein,
`the step of selecting a calibration contact
`formed periodically during active use
`19, The method as in claim 17, wherein;
`is per-
`the step of selecting a calibration contact
`formed periodically during periods of non-use.
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`is per-
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