United States Patent [19J
`Bisset et al.
`
`111111111111111111111111111111111111111111111111111111111111111111111111111
`US005543588A
`[llJ Patent Number:
`[45] Date of Patent:
`
`5,543,588
`Aug. 6, 1996
`
`[54] TOUCH PAD DRIVEN HANDHELD
`COMPUTING DEVICE
`
`[56]
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`[75]
`
`Inventors: Stephen Bisset, Palo Alto; Robert J,
`Miller, Fremont; Timothy P. Allen, Los
`Gatos; Giinter Steinbach, Palo Alto, all
`of Calif.
`
`[73] Assignee: Synaptics, Incorporated, San Jose,
`Calif.
`
`[21] Appl. No.: 161,671
`
`[22] Filed:
`
`Dec. 3,1993
`
`(Under 37 CFR 1.47)
`
`Related U.S. Application Data
`
`[63] Continuation-in-part of Ser. No. 895,934, Jun. 8, 1992, and
`a continuation-in-part of Ser. No. 115,743, Aug. 31, 1993,
`Pat. No. 5,374,787.
`Int. C1.6
`.............................. G08C 21/00; G09G 5/00
`[51]
`[52] U.S. Cl ................................................ 178/18; 345/173
`[58] Field of Search .......................... 178/18, 19; 341133,
`341/34; 3451173, 174
`
`5,327,163
`
`7/1994 Hashimoto eta!. .................. 178/18 X
`
`FOREIGN PATENT DOCUMENTS
`
`2662528 1111991 European Pat. Off ..
`
`Primary Examiner-Stephen Chin
`Assistant Examiner-Kevin Kim
`Attorney, Agent, or Firm-D' Alessandro & Ritchie
`
`[57]
`
`ABSTRACT
`
`A handheld computing device comprises a thin enclosure
`having two opposing major faces. A display screen is
`disposed on a first one of the major opposing faces of the
`enclosure and a touch-sensitive object position detector
`input device is disposed on a second one of the major
`opposing faces of the enclosure. Computing device circuitry,
`circuitry for interfacing the touch-sensitive object position
`detector to the computing device circuitry, and circuitry for
`driving the display screen are all disposed within the enclo(cid:173)
`sure.
`
`4 Claims, 15 Drawing Sheets
`
`EXHIBIT 1008
`IPR Petition for U.S. Patent No. 8,519,973
`
`

`

`U.S. Patent
`
`Aug. 6, 1996
`
`Sheet 1 of 15
`
`5,543,588
`
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`

`

`U.S. Patent
`
`Aug. 6, 1996
`
`Sheet 2 of 15
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`5,543,588
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`
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`
`

`

`U.S. Patent
`
`Aug. 6, 1996
`
`Sheet 4 of 15
`
`5,543,588
`
`32
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`

`

`U.S. Patent
`
`Aug. 6, 1996
`
`Sheet 5 of 15
`
`5,543,588
`
`IN
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`

`

`U.S. Patent
`
`Aug. 6, 1996
`
`Sheet 6 of 15
`
`5,543,588
`
`120
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`

`

`U.S. Patent
`
`Aug. 6, 1996
`
`Sheet 7 of 15
`
`5,543,588
`
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`
`

`

`U.S. Patent
`US. Patent
`
`Aug. 6, 1996
`Aug. 6, 1996
`
`Sheet 8 of 15
`Sheet 8 of 15
`
`5,543,588
`5,543,588
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`

`U.S. Patent
`
`Aug. 6, 1996
`
`Sheet 9 of 15
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`5,543,588
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`

`

`U.S. Patent
`
`Aug. 6, 1996
`
`Sheet 10 of 15
`
`5,543,588
`
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`

`

`U.S. Patent
`
`Aug. 6, 1996
`
`Sheet 11 of 15
`
`5,543,588
`
`258
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`

`

`U.S. Patent
`
`Aug. 6, 1996
`
`Sheet 12 of 15
`
`5,543,588
`
`42
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`

`U.S. Patent
`
`Aug. 6, 1996
`
`Sheet 13 of 15
`
`5,543,588
`
`l,-0
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`
`304
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`

`

`U.S. Patent
`
`Aug. 6, 1996
`
`Sheet 14 of 15
`
`5,543,588
`
`SWITCH
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`f--r-308
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`
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`
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`
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`
`318
`
`

`

`U.S. Patent
`
`Aug. 6, 1996
`
`Sheet 15 of 15
`
`5,543,588
`
`TOUCH PAD
`AREA
`
`312
`
`FIG. 15
`
`FIG. 16
`
`300~
`
`

`

`5,543,588
`
`1
`TOUCH PAD DRIVEN HANDHELD
`COMPUTING DEVICE
`
`RELATED APPLICATIONS
`
`This application is a continuation-in-part of application
`Scr. No. 07/895,934, filed Jun. 8, 1992, and of application
`Scr. No. 08/115,743, filed Aug. 31, 1993, now U.S. Pat. No.
`5,374,787 entitled OBJECT POSITION DETECTOR.
`
`BACKGROUND OF THE INVENTION
`
`15
`
`25
`
`30
`
`2
`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
`5 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
`10 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(cid:173)
`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
`20 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
`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.
`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
`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 XIY
`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
`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
`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
`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
`55 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
`60 zeroing technique that allows "no-finger" levels to be can(cid:173)
`celled 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
`65 Evans relies on the attenuation effect of a finger to modulate
`the drive signal. The touch matrix is sequentially scanned to
`read each matrix lines response. An interpolation program
`
`1. Field of the Invention
`The present invention relates to handheld computing
`devices such as personal digital assistants, pocket calendars,
`communicators, home remote control units and calculators.
`In particular, the present invention relates to computing
`devices that arc meant to be very compact and possibly
`carried in a pocket or purse and which employ touch sensing
`technology as the major means of data input. Personal digital
`assistants arc computing devices that will include all of these
`areas and maintain personal schedulers, telephone books,
`etc.
`2. The Prior Art
`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
`UnMousc product by MicroTouch, of Wilmington, Mass. A 35
`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 40
`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,
`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 50
`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 arc a somewhat expensive because special sen(cid:173)
`sors 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 thumb or other finger for use as
`a pointing device to replace a mouse or trackball. Desirable
`attributes of such a device are low power, low profile, high
`resolution, low cost, fast response, and ability to operate
`
`45
`
`

`

`3
`then selects the two largest adjacent signals in both dimen(cid:173)
`sions to determine the finger location, and ratiometrically
`determines the effective position from those 4 numbers. ·
`Gerpheide, PCT application U.S. Ser. No. 90/04584,
`publication No. W091/03039, applies to a touch pad system 5
`a variation of the virtual dipole approach of Greanias.
`Gerpheide teaches the application of an oscillating potential
`of a given frequency and phase to all electrodes on one side
`of the virtual dipole, and an oscillating potential of the same
`frequency and opposite phase to those on the other side. 10
`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, and
`the opposite polarity if the finger is on the opposite side. To
`acquire the position of the finger initially, the virtual dipole 15
`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 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
`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
`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
`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 35
`scheme to develop their signal. Gruaz and Gerpheide use a
`two signal drive and sense set. In the present invention the
`driving and sensing is done on the same line. This allows the
`row and column sections to be symmetric and equivalent.
`This in tum allows independent calibration of all signal 40
`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
`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
`Gerpheide assume, such approaches are limited in the 60
`amount of interpolation they can perform.
`The touch sensing technology of the present invention
`may be particularly useful when employed as an input
`transducer for a handheld computing device. Numerous
`handheld computing devices such as personal digital assis- 65
`tants have been appearing on the market. Examples are
`Sharp's Wizard, Apple's Newton and similar Hewlett Pack-
`
`50
`
`55
`
`5,543,588
`
`4
`ard products. Presently most of these devices use either a
`miniature keypad input or some type of stylus on top of an
`LCD display.
`In all cases the market push is for smaller and more
`compact systems that eventually fit easily into ones pocket
`or purse. High levels of integration have driven down the
`size of computing devices to the level where a reasonably
`powerful computing device can fit in the volume of a credit
`card. One of the significant obstacles in reducing the size of
`such computing devices has been the size of the user input
`interface. A keypad input or stylus/finger on top of an LCD
`display, which is the industry-standard input paradigm, is
`currently a limiting factor.
`As will be appreciated by those of ordinary skill in the art,
`keypads obviously have a certain minimum size below
`which they are no longer useful. The input regime wherein
`a stylus/finger is moved across the surface of an LCD
`display will suffer from interference of view. Because the
`display screens must necessarily be small, the presence of a
`20 stylus or finger writing on the screen tends to block the
`user's view of a large portion of the screen.
`It is thus an object of the present invention to provide a
`two-dimensional capacitive sensing system equipped with a
`25 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
`30 electronic system that is sensitive to the entire area of
`contact of a finger with a capacitive 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 with a capacitive tablet.
`Yet another object of the present invention to provide a
`handheld computing device where almost the entire surface
`area of one face of the device can be used as a display and
`where the main means for data entry by a user is disposed
`on a second face of the device.
`Yet another object of this invention to provide a low-cost,
`low-parts-count input transducer for a handheld computing
`45 device using a touch pad technology such as the one
`described in co-pending application Ser. Nos. 07/895,934
`and 08/115,743, now U.S. Pat. No. 5,734,787.
`
`BRIEF DESCRIPTION OF THE INVENTION
`
`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-
`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
`
`

`

`5,543,588
`
`5
`"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 5
`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
`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 15
`disposed over the first and second sets of conductive lines.
`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 to 20
`translate the capacitance changes of the conductors caused
`by finger proximity into position and touch pressure infor(cid:173)
`mation. Its output is a simple X, Y and pressure value of the
`one object on its surface.
`Different prior art pad scan techniques have different 25
`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. 30
`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 the Y lines are 35
`held at a constant voltage, with the complete set of sampled
`points simultaneously giving a profile of the finger in the X
`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 40
`complete set of sampled points simultaneously giving a
`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 45
`moved in a positive direction, while the voltages of the Y
`lines arc moved in a negative direction. Next, the voltages on
`all of the X lines of the sensor matrix are simultaneously
`moved in a negative direction, while the voltages of the Y
`lines arc moved in a positive direction. This technique 50
`doubles the effect of any transcapacitance between the two
`dimensions, or conversely, halves the effect of any parasitic
`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. 55
`Both embodiments then take these profiles and calculate
`the centroid for X and Y position and integrate under the
`curve for the Z pressure information. 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 60
`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 ges(cid:173)
`tures 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
`
`6
`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, noise
`reduction techniques that are focused on reducing noise
`produced in typical computer environments are integrated
`into the system.
`According to yet another aspect of the present invention,
`10 a capacitance measurement technique which is easier to
`calibrate and implement is employed.
`A handheld computing device according to the present
`invention may be packaged in a small enclosure wherein a
`display is disposed on a first face of the device and a touch
`pad input device is disposed on a second face of the device.
`The touch pad input device is mapped one-to-one into the
`display on the front side of the module. Computing circuitry
`is contained in the enclosure and coupled to the visual
`display and to the touch panel. The computing circuitry
`accepts input information from the touch panel and displays
`visual information developed from the input information on
`the visual display.
`The present invention uses the very dense touch pad input
`technology disclosed herein in a novel way to make the
`development of a credit card size handheld computing
`device practical. The space layout efficiency of this touch
`pad technology results from the use of printed circuit board
`traces as sensors and thereby doesn't require a special
`transducer. The present invention takes advantage of this by
`providing a novel arrangement whereby the input sensor is
`mounted on a face of the device opposite to the face upon
`which the display is disposed. By so positioning these
`elements of the invention, there is no interference between
`the display and the input touch pad, and the device may be
`configured in a minimum sized enclosure.
`As a non-limiting illustration of a presently preferred
`embodiment of the invention, the handheld computing
`device of the present invention may, for example, take the
`form of a personal digital assistant. Such devices are known
`in the art and are used for such purposes as tracking personal
`schedules, maintaining a personal calendar and/or notepad,
`and providing a calculator. The output is displayed on an
`LCD display and may be organized in a menu driven
`fashion. For alphanumeric input a small keyboard would be
`displayed from which the user would select the characters
`needed by touching appropriate areas on the touchpad on the
`underside of the enclosure.
`To use the device, the user would hold the unit in one hand
`(left hand for example/while sliding the index finger of the
`right hand under the display to select the items of interest.
`The left hand would also be used to operate a select switch
`on the upper or lower edge of the module, to allow for the
`click and select or click and drag idioms employed in mouse
`input to computers.
`The benefits of the handheld computing device of the
`present invention are that it permits direct one-to-one control
`of cursor position, allows almost the full surface to be used
`for the display, and employs very inexpensive input tech(cid:173)
`nology. In addition, the finger or stylus does not obscure the
`view of the display, the finger can stay in contact with the
`cursor so that the cursor positi