United States Patent [19]
`Mead et al.
`
`lllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllll
`US005488204A
`5,488,204
`[11] Patent Number:
`Jan. 30, 1996
`[45] Date of Patent:
`
`[54] PAINTBRUSH STYLUS FOR CAPACITIVE
`TOUCH SENSOR PAD
`
`[75]
`
`Inventors: Carver A. Mead, Pasadena; Ralph
`Wolf, Palo Alto; Timothy P. Allen, Los
`Gatos, all of Calif.
`
`[73] Assignee: Synaptics, Incorporated, San Jose,
`Calif.
`
`[21] Appl. No.: 324,438
`
`[22] Filed:
`
`Oct. 17, 1994
`
`Related U.S. Application Data
`
`[63] Continuation-in-part of Ser. No. 300,630, Sep. 2, 1994,
`which is a continuation-in-part of Ser. No. 300,387, Sep. 2,
`1994, which is a continuation-in-part of Ser. No. 115,743,
`Aug. 31, 1993, Pat. No. 5,374,787, which is a continuation(cid:173)
`in-part of Ser. No. 895,934, Jun. 8, 1992, abandoned.
`Int. Cl.6
`..................................................... G08C 21100
`[51]
`[52] U.S. Cl . ............................................... 178/18; 3451179
`[58] Field of Search .................................. 178/12, 19, 20,
`178/87; 345/173, 174, 175, 179, 180, 181;
`341/5; 382/3, 13; 355/27, 266; 3951117,
`118, 122
`
`[56]
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`5,369,227 1111994 Stone ........................................ 178/18
`5,373,118 12/1994 Uktson .................................. 178/18 X
`411995 Kotaki et al ............................ 395/122
`5,408,593
`
`Primary Examiner-Stephen Chin
`Assistant Examiner-Paul Loomis
`Attorney, Agent, or Firm-D' Alessandro & Ritchie
`
`[57]
`
`ABSTRACT
`
`A proximity sensor system includes a touch-sensor pad with
`a sensor matrix array having a characteristic capacitance on
`horizontal and vertical conductors connected to sensor pads.
`The capacitance changes as a function of the proximity of an
`object or objects to the sensor matrix. The change in
`capacitance of each node in both the X and Y directions of
`the matrix due to the approach of an object is converted to
`a set of voltages in the X and Y directions. These voltages
`are processed by circuitry to develop electrical signals
`representative of the centroid of the profile of the object, i.e,
`its position in the X andY dimensions. Noise reduction and
`background level setting techniques inherently available in
`the architecture are employed. A conductive paintbrush-type
`stylus is used to produce paint-like strokes on a display
`associated with the touch-sensor pad.
`
`5,231,450
`
`7/1993 Daniels ..................................... 355/27
`
`11 Claims, 17 Drawing Sheets
`
`APPLE INC.
`EXHIBIT 1108 - PAGE 1
`
`

`

`U.S. Patent
`
`Jan. 30, 1996
`
`Sheet 1 of 17
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`5,488,204
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`APPLE INC.
`EXHIBIT 1108 - PAGE 2
`
`

`

`U.S. Patent
`
`Jan.30, 1996
`
`Sheet 2 of 17
`
`5,488,204
`
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`
`APPLE INC.
`EXHIBIT 1108 - PAGE 3
`
`

`

`U.S. Patent
`
`Jan.30, 1996
`
`Sheet 3 of 17
`
`5,488,204
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`
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`
`APPLE INC.
`EXHIBIT 1108 - PAGE 4
`
`

`

`Jan. 30, 1996
`
`Sheet 4 of 17
`
`5,488,204
`
`U.S. Patent
`40 l
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`
`APPLE INC.
`EXHIBIT 1108 - PAGE 5
`
`

`

`U.S. Patent
`
`Jan. 30, 1996
`
`Sheet 5 of 17
`
`5,488,204
`
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`
`APPLE INC.
`EXHIBIT 1108 - PAGE 6
`
`

`

`U.S. Patent
`
`Jan.30, 1996
`
`Sheet 6 of 17
`
`5,488,204
`
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`
`APPLE INC.
`EXHIBIT 1108 - PAGE 7
`
`

`

`U.S. Patent
`
`Jan.30, 1996
`
`Sheet 7 of 17
`
`5,488,204
`
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`APPLE INC.
`EXHIBIT 1108 - PAGE 8
`
`

`

`U.S. Patent
`
`Jan. 30, 1996
`
`Sheet 8 of 17
`
`5,488,204
`
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`APPLE INC.
`EXHIBIT 1108 - PAGE 9
`
`

`

`U.S. Patent
`
`Jan.30, 1996
`
`Sheet 9 of !"7
`
`5,488,204
`
`184
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`APPLE INC.
`EXHIBIT 1108 - PAGE 10
`
`

`

`U.S. Patent
`
`Jan. 30, 1996
`
`Sheet 10 of 17
`
`5,488,204
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`APPLE INC.
`EXHIBIT 1108 - PAGE 11
`
`

`

`U.S. Patent
`
`Jan. 30, 1996
`
`Sheet 11 of 17
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`5,488,204
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`APPLE INC.
`EXHIBIT 1108 - PAGE 12
`
`

`

`U.S. Patent
`
`Jan.30, 1996
`
`Sheet 12 of i 7
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`5,488,204
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`APPLE INC.
`EXHIBIT 1108 - PAGE 13
`
`

`

`U.S. Patent
`
`Jan. 30, 1996
`
`Sheet 13 of 17
`
`5,488,204
`
`280
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`
`APPLE INC.
`EXHIBIT 1108 - PAGE 14
`
`

`

`U.S. Patent
`
`Jan.30, 1996
`
`Sheet 14 of 17
`
`5,488,204
`
`y
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`
`APPLE INC.
`EXHIBIT 1108 - PAGE 15
`
`

`

`U.S. Patent
`
`Jan. 30, 1996
`
`Sheet 15 of 17
`
`5,488,204
`
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`318
`
`END
`
`FIG. 14C
`
`APPLE INC.
`EXHIBIT 1108 - PAGE 16
`
`

`

`U.S. Patent
`
`Jan.JO, 1996
`
`Sheet 16 o f 1 7
`
`5,488,204
`
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`
`APPLE INC.
`EXHIBIT 1108 - PAGE 17
`
`

`

`U.S. Patent
`
`Jan.30, 1996
`
`Sheet 17 of 17
`
`5,488,204
`
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`
`APPLE INC.
`EXHIBIT 1108 - PAGE 18
`
`

`

`5,488,204
`
`1
`PAINTBRUSH STYLUS FOR CAPACITIVE
`TOUCH SENSOR PAD
`
`RELATED APPLICATIONS
`
`This application is a continuation in part of co-pending
`application Ser. No. 08/300,630, filed Sep. 2, 1994, which is
`a continuation-in-part of application Ser. No. 08/300,387,
`filed Sep. 2, 1994, which is a continuation-in-part of co(cid:173)
`pending application Ser. No. 08/115,743, filed Aug. 31,
`1993, now U.S. Pat. No. 5,374,787, which is a continuation(cid:173)
`in-part of co-pending application Ser. No. 07/895,934, filed
`Jun. 8, 1992, now abandoned.
`
`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`The present invention relates to object position sensing
`transducers and systems. More particularly, the present
`invention relates
`to object position recognition with
`enhanced edge-motion features useful in applications such
`as cursor movement for computing devices and other appli(cid:173)
`cations, and especially to a paintbrush-like stylus for use
`with a capacitive touch sensor pad to create brush-like
`strokes on a display screen.
`2. The Prior Art
`Numerous devices are available or have been proposed
`for use as object position detectors for use in computer
`systems and other applications. The most familiar of such
`devices is the computer "mouse". While extremely popular
`as a position indicating device, a mouse has mechanical pans
`and requires a surface upon which to roll its position ball.
`Furthermore, a mouse usually needs to be moved over long
`distances for reasonable resolution. Finally, a mouse
`requires the user to lift a hand from the keyboard to make the
`cursor movement, thereby upsetting the prime purpose,
`which is usually typing on the computer.
`Trackball devices are similar to mouse devices. A major
`difference, however is that, unlike a mouse device, a track(cid:173)
`ball device does not require a surface across which it must
`be rolled. Trackball devices are still expensive, have moving
`parts, and require a relatively heavy touch as do the mouse
`devices. They are also large in size and do not fit well in a
`volume-sensitive application like a laptop computer.
`There are several available touch-sense technologies
`which may be employed for use as a position indicator.
`Resistive-membrane position sensors are known and used in
`several applications. However, they generally suffer from
`poor resolution, the sensor surface is exposed to the user and
`is thus subject to wear. In addition, resistive-membrane
`touch sensors are relatively expensive. A one-surface
`approach requires a user to be grounded to the sensor for
`reliable operation. This cannot be guaranteed in portable
`computers. An example of a one-surface approach is the
`UnMouse product by MicroTouch, of Wilmington, Mass. A
`two-surface approach has poorer resolution and potentially
`will wear out very quickly in time.
`Resistive tablets are taught by U.S. Pat. No. 4,680,430 to
`Yoshikawa, U.S. Pat. No. 3,497,617 to Ellis and many
`others. The drawback of all such approaches is the high
`power consumption and the high cost of the resistive mem(cid:173)
`brane employed.
`Surface Acoustic Wave (SAW) devices have potential use
`as position indicators. However, this sensor technology is
`expensive and is not sensitive to light touch. In addition.
`
`15
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`25
`
`2
`SAW devices are sensitive to residue buildup on the touch
`surfaces and generally have poor resolution.
`Strain gauge or pressure plate approaches are an interest(cid:173)
`ing position sensing technology, but suffer from several
`5 drawbacks. This approach may employ piezoelectric trans(cid:173)
`ducers. One drawback is that the piezo phenomena is an AC
`phenomena and may be sensitive to the user's rate of
`movement. In addition, strain gauge or pressure plate
`approaches are somewhat expensive because special sensors
`10 are required.
`Optical approaches are also possible but are somewhat
`limited for several reasons. All would require light genera(cid:173)
`tion which will require external components and increase
`cost and power drain. For example, a "finger-breaking"
`infra-red matrix position detector consumes high power and
`suffers from relatively poor resolution.
`There have been numerous attempts to provide a device
`for sensing the position of a thumb or other finger for use as
`a pointing device to replace a mouse or trackball. Desirable
`20 attributes of such a device are low power, low profile, high
`resolution, low cost, fast response, and ability to operate
`reliably when the finger carries electrical noise, or when the
`touch surface is contaminated with dirt or moisture.
`Because of the drawbacks of resistive devices, many
`attempts have been made to provide pointing capability
`based on capacitively sensing the position of the finger. U.S.
`Pat. No. 3,921,166 to Volpe teaches a capacitive matrix in
`which the finger changes the transcapacitance between row
`and column electrodes. U.S. Pat. No. 4,103,252 to Bobick
`employs four oscillating signals to interpolate x and y
`positions between four capacitive electrodes. U.S. Pat. No.
`4,455,452 to Schuyler teaches a capacitive tablet wherein
`the finger attenuates the capacitive coupling between elec-
`trodes.
`U.S. Pat. No. 4,550,221 to Mabusth teaches a capacitive
`tablet wherein the effective capacitance to "virtual ground"
`is measured by an oscillating signal. Each row or column is
`polled sequentially, and a rudimentary form of interpolation
`is applied to resolve the position between two rows or
`columns. An attempt is made to address the problem of
`electrical interference by averaging over many cycles of the
`oscillating waveform. The problem of contamination is
`addressed by sensing when no finger was present, and
`45 applying a periodic calibration during such no-finger-present
`periods. U.S. Pat. No. 4,639,720 to Rympalski teaches a
`tablet for sensing the position of a stylus. The stylus alters
`the transcapacitance coupling between row and column
`electrodes, which are scanned sequentially. U.S. Pat. No.
`50 4,736,191 to Matzke teaches a radial electrode arrangement
`under the space bar of a keyboard, to be activated by
`touching with a thumb. This patent teaches the use of total
`touch capacitance, as an indication of the touch pressure, to
`control the velocity of cursor motion. Pulsed sequential
`55 polling is employed to address the effects of electrical
`interference.
`U.S. Pat. Nos. 4,686,332 and 5,149,919, to Greanias,
`teaches a stylus and finger detection system meant to be
`mounted on a CRT. As a finger detection system, its XfY
`60 sensor matrix is used to locate the two matrix wires carrying
`the maximum signal. With a coding scheme these two wires
`uniquely determine the location of the finger position to the
`resolution of the wire stepping. For stylus detection, Gre(cid:173)
`anias first coarsely locates it, then develops a virtual dipole
`65 by driving all lines on one side of the object in one direction
`and all lines on the opposite side in the opposite direction.
`This is done three times with different dipole phases and
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`30
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`35
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`40
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`5,488,204
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`10
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`3
`signal polarities. Assuming a predetermined matrix response
`to the object, the three measurements present a set of
`simultaneous equations that can be solved for position.
`U.S. Pat. No. 4,733,222 to Evans is the first to teach a
`capacitance touch measurement system that interpolates to a 5
`high degree. Evans teaches a three terminal measurement
`system that uses a drive, sense and electrode signal set (3
`signals) in its matrix, and bases the measurement on the
`attenuation effect of a finger on the electrode node signal
`(uses a capacitive divider phenomena). Evans sequentially
`scans through each drive set to measure the capacitance.
`From the three largest responses an interpolation routine is
`applied to determine finger position. Evans also teaches a
`zeroing technique that allows "no-finger" levels to be can(cid:173)
`celed out as part of the measurement.
`U.S. Pat. No. 5,016,008 to Gruaz describes a touch
`sensitive pad that also uses interpolation. Gruaz uses a drive
`and sense signal set (2 signals) in the touch matrix and like
`Evans relies on the attenuation effect of a finger to modulate
`the drive signal. The touch matrix is sequentially scanned to
`read the response of each matrix line. An interpolation
`program then selects the two largest adjacent signals in both
`dimensions to determine the finger location, and ratiometri(cid:173)
`cally determines the effective position from those four
`numbers.
`Gerpheide, PCT application US90/04584, publication No.
`W091/03039, U.S. Pat. No. 5,305,017 applies to a touch pad
`system a variation of the virtual dipole approach of Grean(cid:173)
`ias. Gerpheide teaches the application of an oscillating
`potential of a given frequency and phase to all electrodes on 30
`one side of the virtual dipole, and an oscillating potential of
`the same frequency and opposite phase to those on the other
`side. Electronic circuits develop a "balance signal" which is
`zero when no finger is present, and which has one polarity
`if a finger is on one side of the center of the virtual dipole, 35
`and the opposite polarity if the finger is on the opposite side.
`To acquire the position of the finger initially, the virtual
`dipole is scanned sequentially across the tablet. Once the
`finger is located, it is "tracked" by moving the virtual dipole
`toward the finger once the finger has moved more than one 40
`row or column.
`Because the virtual dipole method operates by generating
`a balance signal that is zero when the capacitance does not
`vary with distance, it only senses the perimeter of the finger 45
`contact area, rather than the entire contact area. Because the
`method relies on synchronous detection of the exciting
`signal, it must average for long periods to reject electrical
`interference, and hence it is slow. The averaging time
`required by this method, together with the necessity to 50
`search sequentially for a new finger contact once a previous
`contact is lost, makes this method, like those before it, fall
`short of the requirements for a fast pointing device that is not
`affected by electrical interference.
`It should also be noted that all previous touch pad 55
`inventions that used interpolation placed rigorous design
`requirements on their sensing pad. Greanias and Evans use
`a complicated and expensive drive, sense and electrode line
`scheme to develop their signal. Gruaz and Gerpheide use a
`two signal drive and sense set. In the present invention the 60
`driving and sensing is done on the same line. This allows the
`row and column sections to be symmetric and equivalent.
`This in turn allows independent calibration of all signal
`paths, which makes board layout simpler and less constrain(cid:173)
`ing, and allows for more unique sensor topologies.
`The shortcomings of the inventions and techniques
`described in the prior art can also be traced to the use of only
`
`4
`one set of driving and sensing electronics, which was
`multiplexed sequentially over the electrodes in the tablet.
`This arrangement was cost effective in the days of discrete
`components, and avoided offset and scale differences among
`circuits.
`The sequential scanning approach of previous systems
`also made them more susceptible to noise. Noise levels
`could change between successive measurements, thus
`changing the measured signal and the assumptions used in
`interpolation routines.
`Finally, all previous approaches assumed a particular
`signal response for finger position versus matrix position.
`Because the transfer curve is very sensitive to many param(cid:173)
`eters and is not a smooth linear curve as Greanias and
`15 Gerpheide assume, such approaches are limited in the
`amount of interpolation they can perform.
`In prior co-pending application Ser. No. 08/115,743, filed
`Aug. 31, 1993, now U.S. Pat. No. 5,374,787 a two-dimen-
`20 sional capacitive sensing system equipped with a separate
`set of drive/sense electronics for each row and for each
`column of a capacitive tablet is disclosed. All row electrodes
`are sensed simultaneously, and all column electrodes are
`sensed simultaneously. The sensed signals are processed by
`25 analog circuitry.
`Electronic styli for use in "drawing" on touch-pad posi(cid:173)
`tion sensors are known in the art. Such styli resemble a
`pencil in appearance and operation. Because of limited
`ability to sense "pressure" information, a stylus for imitating
`the action of a paintbrush is not practical using such tech(cid:173)
`nology.
`It is thus an object of the present invention to provide a
`two-dimensional capacitive sensing system equipped with a
`separate set of drive/sense electronics for each row and for
`each column of a capacitive tablet, wherein all row elec(cid:173)
`trodes are sensed simultaneously, and all column electrodes
`are sensed simultaneously.
`It is a further object of the present invention to provide an
`electronic system that is sensitive to the entire area of
`contact of a finger or other conductive object with a capaci(cid:173)
`tive tablet, and to provide as output the coordinates of some
`measure of the center of this contact area while remaining
`insensitive to the characteristic profile of the object being
`detected.
`It is a further object of the present invention to provide an
`electronic system that provides as output some measure of
`area of contact of a finger or other conductive object with a
`capacitive tablet.
`Yet another object of the present invention is to provide a
`two-dimensional capacitive sensing system equipped with a
`separate set of drive/sense electronics for each row and for
`each column of a capacitive tablet, wherein all row elec(cid:173)
`trodes are sensed simultaneously, and all column electrodes
`are sensed simultaneously and wherein the information
`defining the location of a finger or other conductive object
`is processed in digital form.
`It is a further object of the present invention to provide a
`two-dimensional capacitive sensing system wherein all row
`electrodes are sensed simultaneously, and all column elec(cid:173)
`trodes are sensed simultaneously and wherein the location of
`a finger or other conductive object within a peripheral region
`of a sensing plane can optionally cause cursor "edge
`motion" on a display screen allowing control of large cursor
`65 excursions from a small sensing plane with a single gesture.
`Yet another object of the present invention is to provide a
`two-dimensional capacitive touch sensing system which
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`5,488,204
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`5
`may be used along with a "paintbrush" type conductive
`stylus which may be used to "paint" with paintbrush-like
`strokes on a capacitive touch sensor pad for display on a
`display screen.
`
`BRIEF DESCRIPTION OF THE INVENTION
`
`25
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`30
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`6
`dimension. Next, the voltages on all of the Y lines of the
`sensor matrix are simultaneously moved, while the voltages
`of the X lines are held at a constant voltage to obtain a
`complete set of sampled points simultaneously giving a
`5 profile of the finger in the other dimension.
`According to a second drive/sense method, the voltages
`on all of the X lines of the sensor matrix are simultaneously
`moved in a positive direction, while the voltages of the Y
`lines are moved in a negative direction. Next, the voltages on
`10 all of the X lines of the sensor matrix are simultaneously
`moved in a negative direction, while the voltages of the Y
`lines are moved in a positive direction. This technique
`doubles the effect of any transcapacitance between the two
`dimensions, or conversely, halves the effect of any parasitic
`15 capacitance to ground. In both methods, the capacitive
`information from the sensing process provides a profile of
`the proximity of the finger to the sensor in each dimension.
`As presently preferred, both embodiments then take these
`profiles and derive a digital value representing the centroid
`20 for X andY position and derive a second digital value for the
`Z pressure information. The digital information may be
`directly used by a host computer. Analog processing of the
`capacitive information may also be used according to the
`present invention.
`The position sensor of these embodiments can only report
`the position of one object on its sensor surface. If more than
`one object is present, the position sensor of this embodiment
`computes the centroid position of the combined set of
`objects. However, unlike prior art, because the entire pad is
`being profiled, enough information is available to discern
`simple multi-finger gestures to allow for a more powerful
`user interface.
`According to another aspect of the present invention,
`several power reduction techniques which can shut down the
`circuit between measurements have been integrated into the
`system. This is possible because the parallel measurement
`technique according to the present invention is so much
`faster than prior art techniques.
`According to a further aspect of the invention, a variety of
`noise reduction techniques are integrated into the system.
`According to yet another aspect of the present invention,
`a capacitance measurement technique which is easier to
`calibrate and implement is employed.
`According to another aspect of the present invention,
`when the presence of a finger or other conductive object is
`sensed within a defined peripheral region of the sensing
`plane, the control of cursor motion may be changed to
`provide "edge motion" to allow control of large cursor
`excursions on a display screen from a single gesture
`executed on a small sensing plane.
`According to yet a further aspect of the present invention,
`a paintbrush-like conductive stylus may be employed by a
`user to "paint" with brush-like strokes on a display screen.
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`With the advent of very high levels of integration, it has
`become possible to integrate many channels of driving/
`sensing electronics into one integrated circuit, along with the
`control logic for operating them, and the interface electron(cid:173)
`ics to allow the pointing device to communicate directly
`with a host microprocessor. The present invention uses
`adaptive analog techniques to overcome offset and scale
`differences between channels, and can thus sense either
`transcapacitance or self-capacitance of all tablet rows or
`columns in parallel. This parallel-sensing capability, made
`possible by providing one set of electronics per row or
`column, allows the sensing cycle to be extremely short, thus
`allowing fast response while still maintaining immunity to
`very high levels of electrical interference.
`The present invention comprises a position-sensing tech(cid:173)
`nology particularly useful for applications where finger
`position information is needed, such as in computer
`"mouse" or trackball environments. However the position(cid:173)
`sensing technology of the present invention has much more
`general application than a computer mouse, because its
`sensor can detect and report if one or more points are being
`touched. In addition, the detector can sense the pressure of
`the touch.
`According to a preferred embodiment of the present
`invention, referred to herein as a "finger pointer" embodi(cid:173)
`ment, a position sensing system includes a position sensing
`transducer comprising a touch-sensitive surface disposed on
`a substrate, such as a printed circuit board, including a 35
`matrix of conductive lines. A first set of conductive lines
`runs in a first direction and is insulated from a second set of
`conductive lines running in a second direction generally
`perpendicular to the first direction. An insulating layer is
`disposed over the first and second sets of conductive lines. 40
`The insulating layer is thin enough to promote significant
`capacitive coupling between a finger placed on its surface
`and the first and second sets of conductive lines.
`Sensing electronics respond to the proximity of a finger, 45
`conductive object, or an object of high dielectric constant
`(i.e., greater than about 5) to translate the capacitance
`changes of the conductors caused by object proximity into
`digital information which is processed to derive position and
`touch pressure information. Its output is a simple X, Y and
`pressure value of the one object on its surface. In all
`descriptions herein, fingers are to be considered interchange(cid:173)
`able with conductive objects and objects of high dielectric
`constant.
`Different prior art pad scan techniques have different 55
`advantages in different environments. Parallel drive/sense
`techniques according to the present invention allow input
`samples to be taken simultaneously, thus all channels are
`affected by the same phase of an interfering electrical signal,
`greatly simplifying the signal processing and noise filtering. 60
`There are two drive/sense methods employed in the touch
`sensing technology of the present invention. According to a
`first and presently preferred embodiment of the invention,
`the voltages on all of the X lines of the sensor matrix are
`simultaneously moved, while the voltages of theY lines are 65
`held at a constant voltage, with the complete set of sampled
`points simultaneously giving a profile of the finger in the X
`
`50
`
`FIG. 1 is an ove