ABSTRACT OF THE DISCLOSURE
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`Keyboards, keypads and other data entry devices can suffer from a keying
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`ambiguity problem. In a small keyboard, for example, a user's finger is
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`likely to overlap from a desired key to onto adjacent ones. An iterative
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`method of removing keying ambiguity from a keyboard comprising an
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`array of capacitive keys involves measuring a signal strength associated
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`with each key in the array, comparing the measured signal strengths to
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`find a maximum, determining that the key having the maximum signal
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`strength is the unique user-selected key, and maintaining that selection
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`until either the initially selected key's signal strength drops below some
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`threshold level or a second key's signal strength exceeds the first key's
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`signal strength.
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`IPR2020-00778
`Apple EX1002 Page 1
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`[0001] This application is a continuation-in-part of the inventor's US
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`11 /160,885, filed on July 14, 2005, which is a continuation of the
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`inventor's US Patent 6,993,607, filed on July 11, 2003, which claimed the
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`priority of his US provisional application 60/395,368, filed July 12, 2002.
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`Moreover, this application claims the priority of the inventor's provisional
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`application 60/597,851, filed December 21, 2005.
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`BACKGROUND INFORMATION
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`[0002] The invention relates to method and apparatus for controlling
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`an array of non-bistable keys, such as capacitive position sensors, and,
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`more specifically for preventing accidental false inputs from keys
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`adjacent to a selected key in a capacitive keyboard.
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`[0003] Arrays of capacitive proximity sensors are often used in
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`keyboards, keypads and other touch-input apparatus. Two characteristics
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`of capacitive sensors that lead to their use instead of conventional
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`metallic switches are: l) Capacitive sensors can be made in small sizes,
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`which is desirable if a small, tightly packed keyboard is required; and 2)
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`Capacitive sensors are particularly easy to environmentally seal, which is
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`desirable if the keyboard is to be used in a wet environment or where
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`there is a concern that contaminants may be spilled on the keyboard.
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`[0004] Conventional capacitive sensors, when tightly packed, or when
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`used in the presence of conductive liquid films, suffer a keying ambiguity
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`problem. In a small keyboard, for example, a user's finger is likely to
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`overlap from a desired key to onto adjacent ones. This is especially
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`problematic if the user has large fingers or if he or she presses on the
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`keyboard surface hard enough to deform his or her finger. The same sort
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`of effect is found when a conducting film is spilled on a keyboard, in
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`IPR2020-00778
`Apple EX1002 Page 2
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`which case the user's finger is sensed as though it were the size of the
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`puddle. Problems of this sort are particularly acute in cash register
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`keyboards used in food service establishments where beverage and food
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`sauce spills are a frequent occurrence.
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`[0005] In his US Patent 5,730,165, the inventor teaches a capacitive
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`field sensor employing a single coupling plate and a method of detecting
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`a change in capacitance of the coupling plate, Cx, to ground. The
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`apparatus taught in US 5,730,165 comprises pulse circuitry for charging
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`the coupling plate and for subsequently transferring the charge from the
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`plate into a charge detector, which may be a sampling capacitor, Cs. The
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`transferring operation is carried out by means of a transfer switch
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`electrically connected between the coupling plate and the charge
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`detector. The disclosure of US 5,730,165 is herein incorporated by
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`reference.
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`[0006] In his US patent 6,466,036 the inventor teaches pulse circuitry
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`for measuring capacitance to ground, the circuitry comprising a plurality
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`of electrical switching elements, each of which has one side electrically
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`connected to either a power supply voltage or to a circuit ground point.
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`This circuit arrangement, which may be used with a keyboard as well as
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`for many other applications, is more compatible with available integrated
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`circuit design and manufacturing practices than is prior art pulse
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`circuitry, which commonly had one side of at least one switching element
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`floating. These improved arrangements thereby provide superior
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`performance at a lower manufacturing cost. The disclosure of US patent
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`6,466,036 is herein incorporated by reference.
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`SUMMARY OF THE INVENTION
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`Apple EX1002 Page 3
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`[0007] One aspect of the invention is that it may provide an iterative
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`method of removing keying ambiguity by measuring a detected signal
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`strength associated with each key in an array, comparing the measured
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`signal strengths to find a maximum, determining that the key having the
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`maximum signal strength is the unique user-selected first key, and
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`maintaining that selection until either the first key's signal strength drops
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`below some threshold level or a second key's signal strength exceeds the
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`first key's signal strength. When any key is selected its signal strength
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`value may enhanced relative to all the other keys so as to deselect all
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`other keys. In this aspect, the array under consideration may be a
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`keyboard, or any convenient subset thereof.
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`[0008] A particular preferred embodiment of the invention is an array
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`of capacitive keys in which each key has a respective detection integrator
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`counter (DI) associated with it. Each DI is a clocked counter that counts
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`up by one incremental value on each capacitive acquisition cycle during
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`which a signal strength from the associated key is above some nominal
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`threshold value, and that counts down toward zero if the signal strength
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`is less than the nominal value. A controller receives a respective input
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`from each DI and determines that one of the keys is selected, e.g., wins,
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`when the detection integration (DI) count associated with that key meets
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`a respectively selected terminal count value, TC. The incremental
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`magnitude used for counting down can be the same as that for counting
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`up, e.g., l, or it can be different, e.g., 2, to preferentially accelerate the
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`count-down 'losing' process over the winning process, in order to
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`facilitate better suppression of noise. The rate of counting down any of
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`the DI counters can also be the complete value, i.e., the DI can be cleared
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`in one cycle. In this embodiment, when two or more keys have signal
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`strengths above their nominal thresholds, the key with the lesser signal
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`strength will have its associated DI decremented or cleared each cycle
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`Apple EX1002 Page 4
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`while this condition exists. If any two or more keys have equal and
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`maximal signal strengths, such keys' Di's will continue to increment until
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`the first to reach its TC 'wins' and is set as the unique user-selected key.
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`[0009] In another aspect of the invention, the DI of a key selected at a
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`first instant may be decremented or cleared and that key deselected even
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`if the signal strength of that key is above the threshold value and its DI
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`equals its associated TC value, if second key becomes selected at a later
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`instant by virtue of its signal strength being greater than the signal
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`strength of the first key while also being above its own threshold value
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`and having its associated DI equal its associated TC. If there are multiple
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`keys with signal strengths above their associated threshold values, their
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`associated Dis will count up and down in competition, until one key's DI
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`finally equals its TC and wins over all others including over the previously
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`selected key.
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`[001 0] In the above discussions, it should be understood that the
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`principle of having one signal greater than another has been somewhat
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`simplified for explanatory purposes. In order to avoid indecisiveness and
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`eliminate oscillation between two or more keys having more or less the
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`same signal strengths, the winning key may preferably be given a slight
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`advantage in subsequent repetitions of the decision process. This may be
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`done, for example, by requiring a non-selected key's signal to exceed the
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`currently selected key's signal by a small amount. This can be done by
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`subtracting a small amount off the signals of non-selected keys, or by
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`adding a small amount onto the selected key's signal.
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`[0011] An advantage of this method over those disclosed in my US
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`Patent 6,993,607 is that the method disclosed herein permits the smooth
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`rollover of key selection as a finger slides from one key to the next, while
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`Apple EX1002 Page 5
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`still reducing key ambiguity. In the aforementioned patent, the first key
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`to win remains selected even if the maximal signal strength has shifted to
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`a new key, provided that the first key has enough signal strength left to
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`retain its state, i.e., by having its signal strength in excess of its
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`associated threshold value. Therefore the instant invention may be
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`referred to as 'non-locking' key ambiguity reduction.
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`[0012] In yet another aspect of the invention, if the signal strengths of
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`two keys that are approaching a detection threshold value and that are
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`both in a defined keyboard neighborhood both exceed the threshold
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`value and their signal strengths are equal to each other (or are within a
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`selected tolerance value) at the same time, an algorithm executed by a
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`controller may be used to declare one of the two keys to be active and
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`the other to be inactive. It will be recognized that a wide variety of
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`algorithms are possible and include, but are not limited to, a random, or
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`pseudo-random selection of the active key, or a declaration of activity
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`based on which key was scanned first.
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`[0013] The principle also applies in the minimal case where the Di's
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`terminal count (TC) is chosen to be equal to one. This is functionally the
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`same as though there were no DI, but rather just a simple signal
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`comparison function with an inhibiting logic gate following it. Here, the
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`inputs to the inhibiting gate also includes the logical comparisons of the
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`signal strengths among the keys in a neighborhood in order to skew
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`subsequent comparisons to favor the already selected key over
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`competing keys having respective output signals above respective
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`threshold values.
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`[0014] Those skilled in the keyboard arts will understand that the
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`above-mentioned neighborhoods can be defined in a wide variety of
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`Apple EX1002 Page 6
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`ways. In some cases, a neighborhood of a given key may consist of all the
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`keys immediately adjacent the given key, or may comprise all the keys
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`having no more than one key between them and the given key. In other
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`cases, the neighborhood may comprise all the keys in a matrix array -­
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`e.g., in a keyboard for use in a numerical data entry application in which
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`only one key is to be active at a time so that the sequence of input digits
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`is uniquely determined. In other cases, such as in a typing or computer­
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`input keyboard, the neighborhood of a key may comprise all other keys in
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`the keyboard except for special purpose keys, such as a capitalization
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`shift key, a control key, and the like. Moreover, some embodiments of the
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`invention provide a keyboard that is configurable by a user who programs
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`a controller to selectively consider or ignore various keys in an array. In
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`some cases there might be two neighborhoods, each acting
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`independently of the other for key ambiguity resolution purposes.
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`[001 5] Although it is believed that the foregoing rather broad summary
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`description may be of use to one who is skilled in the art and who wishes
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`to learn how to practice the invention, it will be recognized that the
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`foregoing recital is not intended to list all of the features and advantages.
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`Those skilled in the art will appreciate that they may readily use both the
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`underlying ideas and the specific embodiments disclosed in the following
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`Detailed Description as a basis for designing other arrangements for
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`carrying out the same purposes of the present invention and that such
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`equivalent constructions are within the spirit and scope of the invention
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`in its broadest form. Moreover, it may be noted that different
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`embodiments of the invention may provide various combinations of the
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`recited features and advantages of the invention, and that less than all of
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`the recited features and advantages may be provided by some
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`embodiments.
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`Apple EX1002 Page 7
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`DESCRIPTION OF THE DRAWING
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`[0016] Figures la to l c show an array of tightly spaced capacitive
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`buttons.
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`[0017] Figure 2 shows a 2-D touch surface such as a capacitive mouse
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`surface or a capacitive touch screen, with buttons around it.
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`[0018] Figure 3 shows a 2-D touch surface such as a capacitive mouse
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`surface or a capacitive touch screen, with a guard ring disposed around it
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`to suppress activation of the touch screen area when a finger strays just
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`outside the 2-D mouse or screen area.
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`[0019] Figure 4 is a schematic block diagram of a preferred apparatus
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`[0020] Figure Sa is a flow chart showing logical operations carried out
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`in a preferred method of the invention when Key l is initially active.
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`[0021] Figure Sb is a flow chart showing logical operations carried out
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`in a preferred method of the invention when Key l is initially inactive.
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`DETAILED DESCRIPTION
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`[0022] In studying this Detailed Description, the reader may be aided
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`by noting definitions of certain words and phrases used throughout this
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`patent document. Wherever those definitions are provided, those of
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`ordinary skill in the art should understand that in many, if not most
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`instances, such definitions apply to both preceding and following uses of
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`such defined words and phrases. At the outset of this Description, one
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`may note that the terms "include" and "comprise," as well as derivatives
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`thereof, mean inclusion without limitation; the term "or," is inclusive,
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`meaning and/or. The word 'key' as generally used in this Disclosure and
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`as specifically used in the Claims attached hereto refers to a touchable
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`portion of a mechanical to electrical transducing device that is non­
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`bistable in nature. This term specifically excludes conventional
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`mechanical switches in which two or more electrical conductors are
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`moved into or away from contact with each other to make or break an
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`electrical connection. The terms 'keyboard', 'key pad' and the like all
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`refer to arrays of keys for data input without limitation as to the size or
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`configuration of the array. A 'key' can also be a dimensional sensing
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`surface such as an XY touch screen or a 'trackpad', or a sensing zone not
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`intended for normal human data entry such as an object or body part
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`sensor. 'Touch' can mean either human or mechanical contact or
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`proximity to a key. 'User' can mean either a human or a mechanical
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`object. A 'finger' can be, inter alia, a human finger, a mechanical finger
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`or a stylus.
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`[0023] Capacitive sensors, unlike bistable electromechanical switches
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`which are either open or closed, provide a signal that varies with the
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`degree of touch or extent or coupling between a user's finger and a
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`sensing element of a keyboard. Other non-bistable touch sensors, such as
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`an array of piezoelectric sensors in which the output from a given sensor
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`increases with increasing activation force, share many of the properties of
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`capacitive keys. Thus, much of the subsequent disclosure should be
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`understood as being relevant to non-capacitive keys that also provide an
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`output signal responsive to a degree of coupling between the key and a
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`user's finger, stylus, or other key-activating or pointing implement that is
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`proximate the key.
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`IPR2020-00778
`Apple EX1002 Page 9
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`[0024] Turning now to Fig. l A, one finds an array of 'N' tightly spaced
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`capacitive keys in a key panel 11 which would benefit from the invention.
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`When using such small key panels it is inevitable that a finger will
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`encompass much more than the intended key. A finger touching a
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`principle desired key electrode l could easily create a 'fingerprint' outline
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`3, as shown in dashed lines, where the fingerprint has a centroid location
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`A.This fingerprint also encompasses keys other than the intended key.
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`The amount of intersecting surface area between the dashed line and
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`each key area is a reasonable representation of the amount of signal level
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`change each intersected key will receive due to the touch, although even
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`non-touched keys will also see an increase in signal due to mere finger
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`proximity and to fringe-field effects within the touch panel.
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`[0025] In this case, the desire is to select the one and only one key
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`which is intended by the user while suppressing outputs from adjacent
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`keys intersected by the fingerprint. In this 'non-locking' key suppression
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`invention, if the finger slides to a new key location 4, shown dotted with
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`its centroid at location B, where the movement is shown by the arrow
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`from A to B, this movement will not cause the first key l to remain solely
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`active even though it has sufficient signal to still retain its state, i.e., its
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`signal still lies above its threshold level despite being reduced by the
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`movement to a new key. Instead, the invention provides that the newly
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`intended key 2, having a larger signal level due to a higher degree of
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`fingerprint intersection than key l, becomes the solely active key by
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`switching off the active state of key l.
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`[0026] Figures lb and l c further detail the change in signals on the
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`keys of Fig. la by virtue of the relative electrode surface intersections
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`with the fingerprint first at location A (Fig. lb) and then at location B (Fig
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`l c). The signal strengths are shown in the bar plots in the lower portions
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`IPR2020-00778
`Apple EX1002 Page 10
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`

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`of the respective figures. It is desired that in order for a key to 'win' the
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`status of user-selected key, its signal change must exceed a threshold
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`value, and its signal has to be the largest. In Fig. lb, key l wins. In Fig.
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`l c, key 2 wins.
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`[0027] If the key selection method operates solely by picking a
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`maximum signal strength, the keyboard may be subject to an undesirable
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`rapid switching back and forth between two keys having nearly-identical
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`signal strengths (e.g., fingerprint areas). This sort of 'chatter' is
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`preferably prevented by biasing or skewing the key selection method to
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`favor an already selected key. That is, the switchover process is made
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`slightly more difficult than would occur with straight equivalence. This
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`bias may be provided in many ways in subsequent key selection
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`decisions. These ways may be equivalent to adding an incremental value
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`to the signal associated with the selected key; multiplying the signal
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`strength of the selected key by a value greater than one in subsequent
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`selections; subtracting a respective incremental value from the signal
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`strengths associated with each of the non-selected keys; or multiplying
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`the signal strength of each of the non-selected keys by a respective value
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`less than one.
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`[0028] Fig. 2 shows a configuration of a capacitive mouse or capacitive
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`touch screen area 6 with surrounding buttons 7. The principles of
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`operation described in conjunction with Fig. l a-c apply similarly to Fig. 2,
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`in that the area 6 can be treated as a single key with a single signal
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`strength for purposes of key suppression. Fig. 2 applies when the keys 7
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`are very close to pointing surface 6 and fingerprints 3 and 4 can overlap
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`both the capacitive screen and one or more capacitive buttons. Moreover,
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`it should be recognized that although the drawing depicts a two­
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`dimensional touch surface, the same considerations apply to a one-
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`IPR2020-00778
`Apple EX1002 Page 11
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`

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`dimensional touch surface of the sort commonly referred to as a slider,
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`scroll-wheel, or the like.
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`[0029] Fig 3. shows a configuration of a capacitive touch input area 6
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`with a surrounding 'key' 8. The principles of operation described in
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`conjunction with Fig. l apply similarly to Fig. 3, in that the area 6 can be
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`treated as a single key with a single signal strength for purposes of key
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`suppression, while the outer 'key' 8 acts to detect errant touch which
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`falls partially on both 6 and 8. The area 6 can comprise any suitable input
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`arrangement such as a capacitive mouse surface, a capacitive touch
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`screen or a keypad comprising discrete keys.
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`[0030] In this example, the guard electrode 8 is not necessarily
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`intended as an actual control key. A finger sliding from 3 to 4 would still
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`potentially leave the active screen 6, but in fact the touch would not be
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`legal since its areal centroid at 'B' lies principally outside the input area.
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`'Key' 8 detects this out-of-position fingerprint and appropriate logic
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`causes the screen 6 to fall out of detection or to be ignored by further
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`processing. It may be noted that some uses of the guard ring structure
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`do not involve having a finger touching the keypad. For example, one
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`could arrange a guard ring around a capacitive cell phone keypad and use
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`the guard ring output to suppress readings from all the keys in the
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`keypad while the user was talking on the cell phone and holding the
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`keypad of the phone against his or her head.
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`[0031] The guard electrode 'key' 8 in the latter case can also be a
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`discrete solid electrode shape, for example a rectangle, disk, arc, or
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`stripe or other shape, placed in some other location reasonably
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`proximate input area 6. This guard electrode would be activated by
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`placing the product against the user's head or other body part (for
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`IPR2020-00778
`Apple EX1002 Page 12
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`

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`example placing the product in a clothing pocket with the keypad side
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`towards the user's body) in order to suppress further output from the
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`keypad under such adverse conditions. A suitable position for such a
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`'key' might be near the earpiece of a cell phone, some distance away
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`from the keypad or touchscreen.
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`[0032] The guard electrode 'key' 8 can also be either a ring as shown in
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`Fig. 3, or a discrete solid electrode shape, such as a rectangle, disk, arc,
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`or stripe or other shape, placed in some other location reasonably
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`proximate the input area 6 so as to be activated by a mechanical closure.
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`This could provide a cover which, when closed, would cause the guard
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`key 8 to induce the suppression of input area 6.
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`[0033] In order to make the determination of an out-of-position
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`fingerprint for use with the apparatus shown in Fig. 3, the same sorts of
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`biasing arrangements can be used to prevent chatter as discussed supra.
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`However, relationships described above with respect to Fig. 2 presume
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`the gain of the sensing channels with respect to finger surface area to be
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`comparable, so that equivalent fingerprint surface areas on different keys
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`produce comparable signal changes. This is not always the case in any of
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`the instances described with respect to Figs. l a-c, 2 or 3. The electrode
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`sizes of different keys may not be equal, and for various reasons (such as
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`stray loading capacitance variations, etc.) the electrical gains among the
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`various keys can differ. In these instances the incremental values added
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`might be negative. Alternatively, signals from competing keys could be
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`scaled into a state of equivalence by using scaling constants that are
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`experimentally determined to accord with a particular configuration. In
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`any event, one can scale and/or offset the signals into equivalence for
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`comparison purposes and thereby create the desired suppression effect
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`without chatter.
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`IPR2020-00778
`Apple EX1002 Page 13
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`[0034] Turning now to Fig. 4, one finds a schematic representation of
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`apparatus of the invention l 0, comprising an array of N capacitive
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`proximity sensors 12 labeled "Keyl", ... , "Key N". Each of the sensors
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`12 has an output to a respective counter logic 14 that supplies data to
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`and is controlled by suitable control logic l 6. Those skilled in the
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`electronic arts will appreciate that although the counters 14 and control
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`logic l 6 are depicted with discrete blocks in the schematic diagram,
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`these features could be provided either by separate physical circuit
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`elements, or could all be provided by a single microcontroller, as
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`depicted by the dashed phantom line l 8 in Fig. 4. Moreover, although the
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`array of keys l 2 is depicted as being a simple linear array, it will be
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`appreciated by one who reads the complete disclosure contained herein
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`that many other sorts of arrays can be used and will encompass, without
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`being limited to, arrays used as computer keyboards, keypads of the sort
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`commonly used in telephony and automated banking, cash register data
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`input keyboards, etc., as well as various other configurations discussed in
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`conjunction with Fig. 3.
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`[0035] The addition of counters 14, or of the logical function
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`equivalent thereof, when used in the accordance with the teachings of
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`this disclosure, can remove or resolve ambiguities by methods involving
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`comparison of signal strengths from various keys 12. This process
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`involves examining the differences over one or more sequential signal
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`samples.
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`[0036] Turning now to Figs. Sa and Sb, one finds flow charts depicting
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`a preferred method of the invention for operating the apparatus l O so as
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`to suppress extraneous key signals or to otherwise resolve keying
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`ambiguities. This method may be carried out by a microprocessor l 8
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`IPR2020-00778
`Apple EX1002 Page 14
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`

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`operating under control of a program stored in a, preferably, non-volatile
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`memory, or may be carried out by means of discrete circuit elements
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`connected to provide hardwired logic. Although the flowcharts of Figs. Sa
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`and Sb depict operation in terms of a single sensor key l (variously
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`labeled "K eyl" or "Kl") with associated signal level 51 and associated
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`Detection Integrator Oil, it will be understood that this simplification is
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`solely in the interest of clarity of presentation and that an algorithm
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`controlling an actual keyboard could carry out substantially the depicted
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`method for each of the N keys in a parallel fashion.
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`[0037] The depicted method relies on iterated comparisons of sensor
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`outputs, and selects a single sensor output to become active or 'on'
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`based on that sensor both having an output in excess of a detection
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`threshold for some selected number of counter cycles (which may be one)
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`and thereafter having the highest output of all the sensors in the array
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`that have also exceeded the detection threshold for the selected number
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`of cycles of the counters. It will be recognized that one could choose to
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`clock all the counters in parallel in order to achieve this, or that one could
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`scan through the counters and operate them one at a time in rapid
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`succession so as to provide the selected number of counter cycles for
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`each sensor within a sufficiently short time period that a user could not
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`perceive a delay in operation of the keyboard.
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`[0038] A signal 51, acquired from sensor key Kl (Step 24), is compared
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`with a selected signal threshold value (Step 26). If S l is less than the
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`threshold value, the value, DI l, in the DI associated with Kl is
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`decremented by a selected amount (Z) or otherwise reduced (Step 28) if it
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`is greater than zero. If the value 51 is at or above its detection threshold,
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`it is then compared against all other signals Sj in Step 29. If it has the
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`strongest change in signal due to touch, subject to a possible non-
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`IPR2020-00778
`Apple EX1002 Page 15
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`

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`dithering bias value 'k' if another key is active (Step 30) then counter Oil
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`can increment (Step 31). If the condition of Step 30 is not met, DI l is
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`decremented or otherwise reduced (Step 28). Only if the counter Oil
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`equals terminal count value TC (Step 32) does the key become active or
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`ON in Step 33. When it does so the control logic forces all other active
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`keys to become inactive and resets their respective DI counters. In
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`keyboards comprising a large number of keys, only one of which should
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`be active at a time, this OFF status will, of course, be the predominant
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`result of an analysis of the output of any given key. The action of
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`incrementing or decrementing of counter values as described supra can
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`be numerically reversed to achieve the same effect and should be
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`considered to be logically equivalent to the above explanation.
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`[0039] Note that in Fig. Sa, in order for a key to gain dominance over
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`an already active key, it must exceed the active key's last measured
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`signal level by a small added amount 'k', as shown in Step 30 to prevent
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`selection dithering. Although the value k is depicted as an additive
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`constant, it can also be determined as a percentage of the signal level of
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`the active key, or by any of a number of other methods. The incremental
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`value 'k' can also be zero, i.e., nothing is added or subtracted, although
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`this would tend to make the decision process unstable should there be
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`any small amount of signal noise which would introduce dithering
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`between two competing keys. Finally the key Kl can gain dominance in
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`Step 3 3 if the TC is reached, and when it does so it forces all other active
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`keys to become inactive and resets their DI counters.
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`key winning in its [0040] Turning off a key can be forced via a different
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`Step 33, as shown in Fig. Sa, or it can be carried out according to the
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`method depicted in Fig. Sb. Whether a key remains on, in the absence of
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`any other keys with larger signals (Fig. Sa), is determined by whether the
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`IPR2020-00778
`Apple EX1002 Page 16
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`

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`key's signal change remains above a hysteresis level. In Step 35, the
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`determination is made if the signal is below the hysteresis point, and if so
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`the DI is reduced in value by some known amount 'Z' (Step 36). If the DI
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`count falls to zero, the key is made inactive (Step 38). On the other hand,
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`if the signal change remains above the threshold level, the DI counter is
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`increased again to its limit