Elan Microelectronics Corporation v. Apple, Inc.

Filing 236

Declaration of Derek Walter IN SUPPORT OF APPLE INC'S OPPOSITION TO ELAN MICROELECTRONICS CORPORATION'S MOTION FOR PARTIAL SUMMARY JUDGMENT OF INFRINGEMENT OF U.S. PATENT 5,825,352] filed byApple, Inc.. (Attachments: # 1 Exhibit B, # 2 Exhibit C, # 3 Exhibit E, # 4 Exhibit F, # 5 Exhibit I, # 6 Exhibit J, # 7 Exhibit K)(Greenblatt, Nathan) (Filed on 6/2/2011)

Exhibit B

111111111111111111111111111111111111111111111111111111111111111111111111111
US005825352A

United States Patent

[19]

Bisset et al.

[45]

[54]

[75]

Inventors: Stephen J. Bisset, Palo Alto; Bernard
Kasser, Menlo Park, both of Calif.

[73]

Assignee: Logitech, Inc., Fremont, Calif.

[21]

Appl. No.: 608,116

[22]

Filed:

5,016,008
5,203,704
5,327,161
5,365,461
5,376,946
5,432,531
5,442,376
5,463,388
5,495,077
5,528,266
5,543,591
5,565,658
5,648,642

MULTIPLE FINGERS CONTACT SENSING
METHOD FOR EMULATING MOUSE
BUTTONS AND MOUSE OPERATIONS ON A
TOUCH SENSOR PAD

Feb. 28, 1996

5/1991
4/1993
7/1994
11/1994
12/1994
7/1995
8/1995
10/1995
2/1996
6/1996
8/1996
10/1996
7/1997

5,825,352
Oct. 20, 1998

Gruaz et al.
McCloud
Logan et al.
Stein et al.
Mikan
Calder et al.
Tannenbaum et al.
Boie et al.
Miller et al.
Arbeitman et al.
Gillespie et al.
Gerpheide et al.
Miller et al.

345/173
434/156
345/173
364/550
345/173
345/173
345/156
341/33
345/173
345/173
178/18
345/174
178/18

FOREIGN PATENT DOCUMENTS

Related U.S. Application Data
[63]

Continuation of Ser. No. 582,768, Jan. 4, 1996, abandoned.

[51]
[52]
[58]

Int. C1. 6
G09G 5/00; G09G 5/08
U.S. Cl.
345/173; 345/157
Field of Search
345/156, 157,
345/160,173,174,145; 178/18; 341/33

[56]

Patent Number:
Date of Patent:

[11]

References Cited
U.S. PATENT DOCUMENTS

WO 91/03039
WO 97/18508

3/1991
5/1997

345/174
345/173
345/173
345/174
345/173
341/33
345/157
345/173

Synaptics Brochure, "Synaptics Touch Pad," pp. 1-39.

Primary Examiner-Jeffery Brier
Assistant Examiner-Paul A. Bell
Attorney, Agent, or Firm-Townsend and Townsend and
Crew

31 Claims, 17 Drawing Sheets

I ENU

HURSOR
posmON

C

oA

TOUCH PAD

FINGER IN CONTACT
WITH TOUCH SENSOR

110,
ENU

VIDEO DISPLAY
I BUTTON I

ABSTRACT

Method and apparatus for detecting an operative coupling
between one or more fingers or other appropriate objects and
a touch pad includes processes for detection of multiple
maxima with intermediate minima in appropriate sequences
to emulate the operations of cursor control and button
actuations in a pointing and control device.

VIDED DISPLAY
I BUTTONI

~

~

VIDEO DISPLAY
IBUTTON I

2 C
3

YPROFilE :==~~~=~

I', :,l

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moo. ..

720,

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YPROFilE

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AA

PRO~llEI

__-

G06F 3/033

OTHER PUBLICATIONS

[57]

3,921,166 11/1975 Volpe.
4,103,252 7/1978 Bobick
4,455,452 6/1984 Schuyler
4,550,221 10/1985 Mabusth
4,639,720 1/1987 Rympalski et al.
4,686,332 8/1987 Greanias et al.
4,733,222 3/1988 Evans
4,736,191 4/1988 Matzke et al.
4,914,624 4/1990 Dunthorn

WIPO.
WIPO

PRO~llEI

An
TOUCH PAD

FINGER NOT IN
CONTACT
WITH TOUCH
SENSOR

u.s.

Patent

Oct. 20, 1998

Sheet 1 of 17

IDA

FIG. I.

5,825,352

u.s. Patent

Oct. 20, 1998

5,825,352

Sheet 2 of 17

SENSOR

t- 30

"-

YDIRECTION

CONDUCTORS

rr1:

DIRECTION CONDUCTORS {
... f- 45

ANALOG MULTIPLEXOR

CIRCUIT TO MEASURE
f-70
CHANGES IN CAPACITANCE ...
OF SENSOR CONDUCTORS

ANALOG-TO- DIGITAL
CONVERTER

MICROCONTROLLER

... >.-

80

.. ~60

INTERFACE TO PC OR OTHER DEVICE

FIG. 2.

u.s.

Patent

Oct. 20, 1998

Sheet 3 of 17

8S:\..

FIG.

3.

FIG. 4.

5,825,352

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'0
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Xmotion AND Ymotion

465

'JJ.

495

SET XobsolutePrevious =XObSOlute1560
SET YobsolutePrevious=Yobsolute, 570
SET XbuttonPrevious= Xbutton,
580
SET YbuttonPrevious· Ybutton
590

=-

~
~

....

~

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....,

'-..J
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595
Xmotion =Xobsolute - XobsolutePrevious
Ymotion =Yobsolute- YobsolutePrevious

5/0

Ul
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520

FIG. 5.

Ul
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Ul

N

u.s. Patent

Oct. 20, 1998

Sheet 5 of 17

200
.----:':1N=IT::-:-:'A~lIZ=E-!-V~AR~JA~Bl-=E SO:--,/' 205
SET Xstote =Peak I
r - - - - - - ' - - - - - " , 2/0
Xloop Start
2/5

N=N+I
Xsum =Xsum of' X(N)
..----

-..L.

---.

XweighfSum =Xweight Sum'" N* X(N)

Xpeak2= X(N-f)
Xstafe • Tail

NO

FIG.

6-1.

220

5,825,352

u.s. Patent

Oct. 20, 1998

Sheet 6 of 17

5,825,352

NO
295
Set Xobsolute =
XweightSum / Xsum

305

NO
315

(Xpeakl-XValley) >
(Xpeak f) /4? and
(Xpeak2-XValley) > (Xpeak2)/41 and
Xpeakl> Fthresh? and
Xpeok2 >Fthresh?

310
Xbutton =Down

Xbutton= Up

320

FIG. 6-2.

d

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5,825,352

Sheet 8 of 17

Oct. 20, 1998

II

AA
I- -

x
PROFILE __- -_- -

YPROALE

An

TOUCH PAD

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FIG. 78.

FINGER NOT IN
CONTACT
WITH TOUCH
SENSOR

u.s. Patent
130",

740,

VIDEO DISPLAY
ICBUTTONJ

~ENU

2select

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select

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5,825,352

Sheet 9 of 17

Oct. 20, 1998

:1

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YPROFILE

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TO UCHPAD

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PI (9

nn
FIG. 7C.

-_I

u.s. Patent

Oct. 20, 1998

760,

VIDEO DISPLAY

MENU
I

2se1ect

2seleCi II BUTTON:1
C ACTIVATE

/CBUTTONI

'J

YPROFILE

II

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770,

MENU
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13

5,825,352

Sheet 10 of 17

----I
780,

790,

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2seleet
3

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BUTTON

2select ICBUTTONI MENU
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TOUCH PAD

I
I

I

II

PROF~lEI~

nnn

AAA
=-_1

-_-_-_-_-_-_
_

FIG.

u.s.

Patent

BOO

"'

Oct. 20, 1998

BUTTON
MENU
ICBUTTON
I

I

I

MENU
II

2select
3

I

AAR

II
I

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2
3

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3

5,825,352

Sheet 11 of 17

I-============FIG. 7£

-_-_-_-_--II

u.s. Patent

Ir I

5,825,352

Sheet 12 of 17

Oct. 20, 1998

VIDEO DISPLAY

U

VIDEO DISPLAY

IOOTTON I
C= CURSOR
POSITION

C
YPROFILE '---

II
I

J

fiNGER IN CONTACT

WITH TOUCH SENSOR

I I

BUTTON UP

TOUCH PAD

II

A

I

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I

1

I

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II
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PROF~LEI __- - -

FIG. 7F-1.

- __

u.s.

Patent

Oct. 20, 1998

825B",
G=GURSOR
POSITION

YPROFILE
,)

A

II
I

BUTTON DOWN

rUGI
TDUGHPAD

I I

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5,825,352

Sheet 13 of 17

I

I

AA

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J'"'=BU=n=ON]
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HA

AA

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\

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... -.1

1'---_-- _-_-_-___

PROF~LE[

FIG. 7F-2.

BUTTON UP

_

u.s. Patent

Oct. 20, 1998

Sheet 14 of 17

.-------..A-------,/875
Xmotion =Xabsolute - XabsolutePrevious
Ymotion= Yabsolute -Yabsolute Previous

YES

YES

FIG. 8-l

5,825,352

u.s. Patent

Oct. 20, 1998

5,825,352

Sheet 15 of 17

YES

915
Report Button: Down
Set ButtonPrevious=D

9/0
ButtonPrevious =Down
AND [Finger = 0
OR (Finger =/
AND Motion= Yes)]

YES

925
Report Button: Up
Set ButtonPrevious =Up

NO

930
Report Xmotion
Report Ymotion

..--

--L.

-{

935

Set XabsolutePrevious = Xabsolute t
Set YabsolutePrevious = Yabsolute,
Set Finger Previous = Finger

940

FIG. 8-2.

u.s. Patent

Oct. 20, 1998

Sheet 16 of 17

200

.....---:-:,N=IT""""IA""""lIZ=E~V~AR::-:-:IA:-=B L~E-:-S --V" 205
SET Xstate =Peakl
..----~---y

Xloop Start

215

N=N+I
Xsum :: Xsum + X(N)
..--'-

---L.

2/0

---,

XweightSum =XweightSum +N*X(N)

FIG. 9-1.

220

5,825,352

u.s. Patent

Oct. 20, 1998

5,825,352

Sheet 17 of 17

NO
295
Set Xabsolufe =
XweightSum / Xsum

970
Xfinger= 0

305
(Xpeakl-XValley) >
(Xpeak f) /4? and
(Xpeak2-XValley)> (Xpeak2)/4? and
Xpeakl> Fthresh? and
975
Xpeok2 >Fthresh?
Xfinger= I

980
Xfinger=2

320

FIG. 9-2.

5,825,352
1

2

MULTIPLE FINGERS CONTACT SENSING
METHOD FOR EMULATING MOUSE
BUTTONS AND MOUSE OPERATIONS ON A
TOUCH SENSOR PAD

This requires an up-down-up-down finger motion to do the
same thing as simply the "down-up" motion of the mouse
button. In general, any touchpad equivalent to a mouse
button-clicking function requires an extra "up . . . up"
motion of the finger, because the finger must be lifted off the
pad before and after the tap.
The time and stress associated with the extra motion is
significant. Human factors studies have shown that such
touchpads yield lower productivity than a mouse in many
applications. This somewhat limits touchpads to those
applications, such as portable computing, where use of a
mouse is inconvenient due to space or other considerations.
There is therefore a need for a touchpad capable of yielding
the same productivity as a mouse.

5

RELATED APPLICATION
This application is a continuation of U.S. patent application Ser. No. 08/582,768, filed Jan. 4, 1996, abandoned.
FIELD OF THE INVENTION

10

The present invention relates generally to touchpad
devices, and more particularly relates to touchpad devices
which detect at least the presence of one or more objects
such as fingers to effectuate preselected control functions. 15

SUMMARY OF THE INVENTION

BACKGROUND OF THE INVENTION
Touch sensing devices are well known, and take a number
of different forms. Perhaps the best known are resistivemembrane position sensors, which have been used in a
number of different applications for many years. Such
devices have been used as keyboards, position indicators,
and so forth. Other types of touch sensing devices include
resistive tablets, surface acoustic wave devices, touch sensors based on strain gages or pressure sensors, and optical
sensors.
Yet another touch sensing technology is capacitive
sensing, in which the location of a finger (or in some
instances another object such as a stylus) over a sensing
device is determined by virtue of variations in capacitance
under and around the location of the finger. Typical of
capacitive touch sensing devices are touch screens and
capacitive pads which employ a matrix of row and column
electrodes and detect, for example, either the transcapacitance between row and column electrodes or the effective
capacitance to virtual ground. Other capacitive techniques
are also known. Some touch sensitive devices are known to
use interpolation for more precisely identifying the location
of a finger or stylus.
Typical of each of these prior art devices is that each of
them senses any contact as that of only one finger at a time.
Cursor movement is straightforward with one finger, and
tapping of a finger on the surface of the pad can be detected
and acted upon in a manner similar to detecting the actuation
of a button on a mouse. Single and double taps can be used
as simple equivalents of single and double mouse clicks.
With a single-finger touchpad, the click and drag function
is more difficult. With single finger detection, dragging has
been implemented with schemes such as uptap (finger lifted
and placed down again quickly), tap-and-a-half, and sticky
drag (drag lock turns on automatically after the finger is
placed in one location without moving for more than a
certain time, such as one second). All of these methods take
more time and/or more finger motions than it takes to
perform the equivalent function with a mouse, and are not
intuitive to users familiar with electronic mice. Prior art
touch pads are thus less attractive for general use than a
mouse.
Another commonly used function in the prior art is that of
clicking a box (or icon or displayed "button") or series of
boxes (such as "connecting the dots"). With a mouse, the
cursor is moved into position by moving the mouse, then the
click occurs with a down-up motion of the finger to actuate
a button or switch. With a touchpad typical of the prior art,
the cursor is moved into position with the finger, then the
click occurs with a tap of the finger which moved the cursor.

20

25

30

35

40

45

50

55

60

65

The present invention provides a novel method and apparatus for sensing the proximity of multiple simultaneous
fingers or other appropriate objects to a touch sensor. The
present invention may be implemented based on any conventional touch sensing technology, although an exemplary
embodiment involves the use of a capacitive touch sensing
device similar to that described in U.S. patent application
Ser. No. 08,478,290, entitled Touch Sensing Method and
Apparatus, filed Jun. 7, 1995, and assigned to the assignee
of the present application. The numerous modifications to
such a basic device required to implement the present
invention are described generally below, and in detail hereinafter. Alternatively, the present invention may be used with
the method and apparatus described in the U.S. patent
application Ser. No. 08/582,769, entitled Touch Pad Sensing
Method and Apparatus, having as inventors Bemi Joss,
Bernard Kasser and Stephen Bisset, filed on Jan. 4, 1996,
and assigned to the assignee of the present invention, the
relevant portions of which are incorporated herein by reference.
Operation of the present invention includes two aspects:
detection of multiple objects, typically fingers, and assignment of various functions to particular actions by the movement of one or both fingers. The detection function can be
general, but in a simple, exemplary implementation can be
limited to a two-finger function such as the combination of
the index finger and middle finger. In general, these are the
two most dextrous fingers, and they work well together. As
a result, for this exemplary embodiment, the touchpad need
only distinguish between the two fingers in one dimension
since the two fingers are typically side by side. In addition,
the touchpad need only detect the second finger in reasonably close proximity to the first finger. In most situations, the
distance between finger centers will be less than five centimeters. Additional combinations of fingers, such as three
fingers tapping simultaneously or other combinations, may
also be implemented in accordance with the methodology of
the present invention.
For clarity of explanation, the present invention can be
described in most of its applications by establishing one
finger as controlling movement of the cursor, and the second
finger as controlling functions equivalent to a mouse button
or switch. In this context, one finger may be considered the
"point" finger, while the other is the "click" finger. Various
conventional functions may then be defined accordingly. For
example, "drag" may be effected by moving the two fingers
in unison, "point and click" may be effected by moving the
cursor with the first finger and tapping with the second
finger, "point and double click" may be effected by moving
the cursor with the first finger and double tapping with the

5,825,352

3

4

second finger, and so on. "Click and Drag" may be performed simply by moving the cursor to the appropriate
position with the first finger, placing both first and second
fingers on the pad, and moving both fingers together. The
function may be concluded by simply raising one or both
fingers. Similarly, connecting the dots may be performed
simply by moving the cursor from dot to dot with the first
finger, and then clicking on the dot by tapping with the
second finger. It will be apparent to those skilled in the art
that these functions may be defined differently and still fall
within the scope of the present invention. It will also be
apparent that many of these operations will be intuitive to
experienced mouse users, as soon as the correspondence
between mouse functions and the two fingers is demonstated
to the user, and thus their implementation in a touchpad
context makes them especially desirable.
In addition to the foregoing functions, which can be
performed (albeit awkwardly and less intuitively) with conventional touch pads, there are additional functions that can
be performed with two fingers and which can have substantial analogs to the use of a mouse or even go beyond
conventional mouse functions. For example, detection and
location of two fingers will permit the touchpad to report to
a host system the distance between the two fingers. This can
be used, for example, in paint or other programs to determine line width or other spacing functions, or any other
"variable value" function. Similarly, tapping with both fingers at the same time may be defined as an alternate,
shorthand method for a double tap (such as may be defined
for the middle button in a Logitech mouse) or may be
defined as a special function, similar to the "right button"
functions of a mouse. Such special functions may have
particular value in operating systems such as Windows 95
where, for example, implementation of the Object Viewer
function is an important special function. Such functions can
be implemented readily with a triple finger tap, a double tap
of two fingers, or other convenient combination.
Another function which may be implemented with two
finger detection is "drag lock". This function may be used
when a drag function is underway, but at least one of the
fingers reaches the edge of the pad before the drag function
is complete. Touchpad operation may be controlled to maintain the drag mode if, for example, both fingers are lifted off
the pad within a threshold period of one another, and are
then placed down on the pad again within a suitable time
period. In some implementations, highly extended time
periods may be suitable in this context.
A further function which may be readily implemented
with the present invention is the ability to operate in relative
mode, where a first finger performs a key function, and a
second finger controls some attribute of the operation performed by the first finger. For example, a first finger contacting a touch pad may cause a cursor to move across a
screen, while contact (and removal) of a second finger with
the screen may turn an image, or "ink" on (and off). The
resulting image, or "ink," is defined by the motion of the first
finger during the period when the second finger is also in
contact with the pad; gaps in the "ink" occur when the
second finger is lifted away from the pad. The function may,
in some ways, be thought of as electronic finger painting, but
has the additional advantage of allowing multiple characters
to be written on a touch pad. Thus, with the use of two
fingers, hand printing of text with gaps between the letters
and words becomes feasible and convenient, whereas it is
impractical with the prior art "tap and a half' method of
turning on the ink.
Yet another function which may be implemented with the
present invention is use of the touchpad in absolute mode.

Most prior art touchpad devices operate, like mice, in
relative mode by indicating the distance travelled relative to
the starting point of the motion. Touchpads, on the other
hand, can also be operated in absolute mode, where the
absolute position of the finger on the pad is detected and
reported to the host system or application. In absolute mode,
multi-finger detection allows the first finger to point to the
desired absolute position, while the second finger performs
whatever "click" operation is desired without requiring a
removal of the first finger which might lessen accuracy or
resolution.
Also included within the present invention is the detection
and location of more than two fingers, with accompanying
functional definitions permitting such multiple contacts to
indicate pointing device or other control operations, such as
musical keyboards.
It is therefore one object of the present invention to
provide a touchpad system capable of detecting a plurality of
contacts such as fingers.
It is a further object of the present invention to provide a
touchpad device capable of locating a plurality of contacts
such as fingers.
It is a further object of the present invention to provide a
method for detecting the presence of more than one finger on
a touch pad device.
It is a still further object of the present invention to
provide a method for locating each of a plurality of fingers
on a touch pad device.
It is yet another object of the present invention to provide
a method for effecting the "point and click" function on a
touchpad through the use of multiple fingers.
Yet a further object of the present invention is to provide
a method for effecting the "click and drag" function on a
touchpad through the use of multiple fingers.
A still further object of the present invention is to provide
a method for effecting on a touchpad, through the use of
multiple finger contacts, a plurality of conventional mouse
button functions.
Yet another object of the present invention is to provide a
method and apparatus for effecting on a touchpad, through
the use of multiple finger contacts, a plurality of enhanced
functions.
Yet a further object of the present invention is to provide
a method and apparatus for electronic finger painting.
These and other objects of the invention may be better
appreciated from the following detailed description of the
invention, taken together with the appended figures.

5

10

15

20

25

30

35

40

45

50

55

60

65

THE FIGURES
FIG. 1 shows a perspective view of a device according to
the present invention.
FIG. 2 shows in block diagram form the electronics of the
present invention.
FIG. 3 shows a finger profile for two non-overlapping
fingers as sensed by the present invention.
FIG. 4 shows a finger profile for two closely-spaced
fingers as sensed by the present invention.
FIG. 5 shows in flow diagram form the steps for a high
level algorithm for a pointing device according to the
present invention.
FIG. 6 shows in flow diagram form the steps for computing motion and "button" states.
FIGS. 7A-7F2 show in diagrammatic form an exemplary
sequence of finger contacts and movements across a touch
sensor.

5,825,352

5
FIG. 8 shows a more generalized case of FIG. 5.
FIG. 9 shows a more generalized case of FIG. 6.

6

capacitance when no finger is present. This "no-finger"
capacitance is measured and stored at a time previous to the
beginning of the cycle described herein, and is described
DETAILED DESCRIPTION OF IRE
more fully in U.S. patent application Ser. No. 08/478,290,
INVENTION
5 filed 7 Jun. 1995 and commonly assigned.
It has also been found by applicant that it is not necessary,
Referring first to FIG. 1, a plurality of a user's fingers lOA
in all embodiments, to subtract the "no-finger" capacitance
and lOB are shown positioned over a touchpad 20 in
if techniques other than calculation of a centroid are used to
sufficiently close proximity to be operatively connected
locate the position of the fingers, and such subtraction is not
thereto. Movement of a single finger over the touchpad
causes the cursor to move in a now-conventional manner. 10 required even in all instances in which a centroid is calculated. However, in at least some embodiments the sensitivity
However, unlike prior art devices, various control functions
and hence the resolution of the calculated finger location is
may be performed by the use of the second finger, typically
enhanced by such subtraction.
in combination with the same or a related operation of the
Referring again to the exemplary embodiment, the values
first finger. Operations involving more than two fingers may
also be performed. In an exemplary embodiment, the touch- 15 of finger-induced capacitance are then processed to calculate
a position, detect whether one or more fingers is in operative
pad of the present invention reports to a host either the
contact with the pad surface, and to detect any changes in the
relative motion of a finger across the touchpad or changes in
number of fingers operatively coupled to the pad. If the cycle
"button" status.
is repeated rapidly enough to update a graphical user interReferring next to FIG. 2, the operation of the touchpad 20
may be better appreciated. In particular, FIG. 2 shows in 20 face approximately 30 times per second or more, the appearance of smooth and instantaneous response is provided to
block diagram form the electronics implemented to form an
the user. For functions other than pointing, such as handexemplary touchpad 20. A touchpad matrix 30 is composed
writing with the finger, a faster scan rate may be required
of a plurality of rows 35 and columns 40 of wires or traces
and may, for example, be on the order of 200 scans per
arranged in a conventional manner; see U.S. patent application Ser. No. 08/321,987, filed 12 Oct. 1994, entitled 25 second.
Referring next to FIG. 3, a finger profile is shown indicaTouch Pad Sensor with Simultaneous Sensing, commonly
tive of the presence of two fingers, spaced apart from one
assigned with the present application. The rows and columns
another. In particular, the circuitry, software or firmware of
are connected to an analog multiplexor 45 through a plurality of X (row) direction conductors 50 and a plurality of 30 the touchpad circuitry, such as that shown in FIG. 2, detects
a first maxima 85 indicative of a first finger in operative
Y (column) direction conductors 55, one conductor for each
proximity to the touchpad 30, followed by a minima 90
row and each column. Under the control of a microcontroller
indicative of a space between the fingers, and further fol60, the analog multiplexor 45 selects which traces of the
lowed by another maxima 95 indicative of a second finger
matrix 30 will be sampled, and the output of those traces is
then provided to a capacitance measuring circuit 70. One 35 operatively coupled to the touchpad 30. It will be appreciated that, for operations involving more than two fingers,
suitable capacitance measuring circuit is described in aforemore maxima will be detected with an appropriate number
mentioned U.S. patent application Ser. No. 08/321,987,
of intermediate minima.
commonly assigned with the present invention and incorporated herein by reference; another is described in U.S.
Although the finger profile shown in FIG. 3 suggests that
patent application Ser. No. 08/478,290, filed 7 Jun. 1995, 40 the intermediate minima separating the two fingers is a zero
entitled Touch Sensing Method and Apparatus and also
value, it is not necessary in all instances that the minima be
commonly assigned with the present invention and incorzero. Thus, for example, FIG. 4 reflects a finger profile with
porated herein by reference.
a nonzero local minima 100 intermediate the two maxima
105 and 110 indicative of two fingers operatively coupled to
The output of the capacitance measuring circuit is then
provided to an analog to digital converter 80, which operates 45 the touchpad. This finger profile simply reflects two fingers
placed closely to one another, but still yields a valley for
as described in either of the above-referenced patent applimeasurement of the minima.
cations to convert the capacitance values from the circuit 70
into a digital representation. The analog to digital converter
To operate effectively, the present invention must detect
and distinguish the presence of a single finger, and the
80 then supplies the signals to the microcontroller 60, which
operates to form, among other things, a finger profile for one 50 presence of multiple fingers. As noted previously, the second
or more fingers, X-Y cursor data, and control signals.
or additional fingers are typically involved to provide "button" or control functions, similar to actuation of the buttons
Depending on the operation being performed at the particular time, the output of microcontroller 60 is then supplied to
or switches on a mouse. Although the following example
an interface to a PC or other device, such as a PS/2 interface,
describes in detail the use of only two fingers, one for cursor
an RS-232 interface, or an Apple Desktop Bus (ADB).
55 control and a second as a button, the teachings herein are
believed sufficient to permit those skilled in the art to
A key feature of the present invention is its ability to
construct apparata using multiple fingers for additional
distinguish the presence of multiple fingers either touching
buttons.
or in operative proximity to the touchpad 30. In a typical
embodiment, the operation of the circuit of FIG. 2 cycles
To avoid artifacts, a threshold may be applied to the both
continuously. As noted above, the cycle begins by scanning 60 the maximum and minimum distance between the maxima
the traces and measuring the capacitance on each trace. Then
representative of multiple fingers. For example, a threshold
the portion of each measured capacitance that is induced by
requiring the maxima to be within five centimeters of one
another may be used to limit the maximum distance between
the presence of a finger is extracted, and this finger-induced
the fingers; other thresholds may be appropriate in some
capacitance is stored in RAM, as X(I) through X(Xcon) and
Y(I) through Y(Ycon), as described below. The finger- 65 embodiments. A threshold representative of the minimum
induced portion of the measured capacitance is determined
distance may be configured by establishing a maximum
by subtracting a value, for each trace, representing the
value of the local minima 100.

5,825,352
7

8

In an exemplary embodiment, the operation of the system
as checked at step 490, the state of Ybutton is up and
of FIG. 2 is controlled in either firmware, software or
YbuttonPrevious is Down, then the variable Button is set to
hardware. Shown in FIG. 5 is a flow diagram showing the
Up at step 495.
general operation of such software or firmware which is
If the button was set to Down at state 465, or Up at step
capable of detecting multiple fingers, and which uses the 5 495, or if the results at steps 480 and 490 are NO, the process
algorithm of FIG. 6, discussed hereinafter. The variables
advances to step 510.
found in the flow diagram of FIG. 5 are defined below:
At step 510, Xmotion is set to the sum of Xabsolute less
XabsolutePrevious, and at step 520, Ymotion is set to the
sum ofYabsolute less YabsolutePrevious. Then, at step 530,
Name
Definition
10 the state of Button is checked and, if it is changed by being
Xabsolute
Finger position in X direction, calculated during the
either Up or Down, both Xmotion and Ymotion are set to
current cycle relative to the sensor pad.
zero at step 535, indicating that the user has actuated a
The value above stored from the previous cycle.
XabsolutePrevious
button and no cursor movement should occur.
Yabsolute
Similar to Xabsolute.
In addition, if Button equals Up or Down, the state of
YabsolutePrevious
Similar to XabsolutePrevious.
Xbutton
Has value Up or Down (regardless of previous
15 Button is reported at step 540. At step 550, Xmotion and
state).
Ymotion are compared to zero, and if either is not zero then
XbuttonPrevious
The value above stored from the previous cycle.
both Xmotion and Ymotion are reported to the microconYbutton
Similar to Xbutton.
troller. It will be apparent that this indicates a cursor
Similar to XbuttonPrevious.
YbuttonPrevious
Xmotion
Cursor motion in the X direction, relative to the
movement, typically reflective of the movement of a single
cursor position of the previous cycle (only reported
20 finger over the touchpad, or two fingers in some modes such
if either or both Xmotion and Ymotion are
as Click-and-Drag.
non-zero).
Ymotion
Similar to Xmotion.
Further, at step 560, whether there is motion reported or
May be Up or Down (only reported if a change
Button
not, the variable XabsolutePrevious is set to the value of
from the previous cycle).
Xabsolute, and at step 570 the variable YabsolutePrevious is
25 set to the value ofYabsolute. Similarly, at step 580 the value
It will be understood by those skilled in the art that a "report"
of XbuttonPrevious is set to Xbutton, and at step 590 the
means transmitting information to an application process
value of YabsolutePrevious is set to Yabsolute. The cycle
executing on a host, such that the cursor is moved or a
then repeats by returning to step 400. It will be apparent that
function is performed. In some instances, driver software
the foregoing algorithm can be readily extended to include
executing on the host may ascertain the existence of finger 30 additional fingers beyond two, representative of additional
movement, while in other instances including the exemplary
buttons. In such an instance, compare steps for current and
embodiment described herein the determination of finger
previous states of each button would be conducted, and
movement occurs in the firmware in the pointing device.
"up," or "down" conditions would be reported for each such
Referring still to FIG. 5, the cyclical process begins at step
button. In some embodiments it may be desired to report "no
400, and continues at step 410 by scanning the conductor 35 change" conditions, and the foregoing algorithm could be
sensors. The sensors may be scanned sequentially or
readily modified to provide such reporting.
concurrently, depending on the hardware implementation.
Depending on the desired configuration, second and third
The scan process measures the values of finger-induced
buttons may be implemented, for example, either by requircapacitance for each of the conductors, and stores the values
ing a combination of two or more fingers to indicate operain RAM at step 420. The cycle process continues by 40 tion of a second button, or by the independent movement of
performing the Xcompute loop of FIG. 6 discussed
additional fingers or other objects. In this latter embodiment,
hereinafter, and also the Ycompute loop analogous to FIG.
it may be desirable to implement distance thresholding, to
6, at step 430 and 440, respectively. In general, the function
ensure that movement of a second or additional button finger
of the Xcompute and Ycompute processes is simply to
is not mistaken for movement of the first or other button
evaluate the current measurements by calculating the cen- 45 finger.
troid of the finger measurement, and by detecting whether a
Set forth in FIG. 6 is a flow diagram setting forth the steps
second finger is touching the pad-which determines the
for computing motion and "button" states in the X direction,
button state.
or what may be referred to as "Xcompute." An analogous
In the exemplary embodiment, only a change in the button
calculation is performed for the Y direction, or what may be
state is reported. As a result, at step 450 the value of Button 50 referred to as "Ycompute." The algorithm uses the following
is set to No Change. In addition, in the exemplary embodivariables and constants:
ment a tap or double click by only a first finger is not acted
upon, although a tap by a second finger or by multiple
fingers is acted upon. In the exemplary arrangement, a
Name
Definition
"button down" condition is only reported if both fingers are 55
X(N)
Values, stored in memory, of finger-induced portion of
in operative contact with the touchpad.
capacitance measured on each conductor. N varies from
The process continues by comparing the current and
1 to Xcon. [When no finger is contacting the pad above
a conductor, the value is approximately zero. In addition,
previous button states of the X and Y conductors. First, at
X(O) is initialized to a value of 0.]
step 460, the state of Xbutton is checked to see if it is Down
X(N-1)
Value of finger-induced sensor conductor capacitance
and the state of XbuttonPrevious is checked to see if it is Up. 60
for the previous conductor.
If both compares are true, then the variable Button is set to
Xcon
The number of sensor conductors in the X direction.
Fthresh
The minimum threshold that X must reach before a finger is
Down at step 465. In addition, at step 470, the state of
considered to be present. [Sets the touch sensitivity of
Ybutton is checked to see if it is Down and the state of
the pad.]
YbuttonPrevious is checked to see if it is Up. If both
Variable to store the value of the first peak X value.
Xpeak1
compares are true, the variable Button is also set to Down. 65 Xvalley
Variable to store the value of a local minimum (if any)
between 2 peaks.
Alternatively, as determined at step 480, if the state of
Xbutton is Up and the state of XbuttonPrevious is Down, or,

5,825,352
9
Name

10

-continued

235 and a repeat with an incrementally higher N. If a second
finger is touching the pad then eventually the value of
X(N-l) will be geater than or equal to the value of X(N),
such that the valley is detected. At this point, at step 262, the
value of Xvalley is set to X(N-l) and Xstate is set to Peak2.
The process then jumps to step 235, where it repeats from
step 215 unless the last conductor in the matrix has been
evaluated.
On the next cycle, a NO result is reached at both step 225
and step 250, causing a jump to step 270. At step 270 the
state of Xstate is compared to Peak2, and a YES result will
occur. This results in a compare between X(N) and X(N-l)
at step 275, to look for a second peak, in a manner substantially identical to the process by which the first peak was
found. As long as X(N) is greater than or equal to X(N-l),
the peak has not been found, so the process jumps to step
235, and then to step 215 until the change measured at the
last conductor has been evaluated.
As before, the value of X(N) will eventually start to
decrease, such that X(N) will be less than X(N-l). At this
point, at step 278, the value of Xpeak2 is set to the value of
X(N-1) and the state of Xstate is set to Tail. The "tail" is the
remaining portion of FIG. 4 following the second peak.
While a Tail state is used in the exemplary embodiment,
such a state may not be necessary in all embodiments.
The process then cycles through until the last conductor
measurement has been considered, at which point N does
equal Xcon when the check at step 235 is made. With a YES
result, the process branches to a thresholding comparison at
step 290.
In an exemplary embodiment, the Xcompute process then
continues by calculating the centroid for the fingers
detected, so long as the maxima exceed a threshold value. In
accordance with the present invention, two approaches may
be used in calculating centroid values. In a first
implementation, only a single centroid value is calculated
for the combination of one or more fingers. In this
arrangement, it will be apparent that, when a second finger
contacts the touchpad, the centroid "jumps" laterally
approximately to the midpoint of the two fingers. In a second
implementation, a centroid value may be calculated for each
maxima, yielding multiple centroid values when multiple
fingers interact with the pad. For purposes of clarity, the
following description will be limited to the first implementation.
Thus, at step 290 the values of Xpeakl and Xpeak2 are
compared to Fthresh, and if either or both are greater then
Xabsolute is set to the value of XweightSumlXsum at step
295, which causes the X centroid to be calculated. If neither
peak exceeds Fthresh, then no finger is deemed present and
Xbutton is set to Up at step 315.
If both Xpeakl and Xpeak2 were greater than Fthresh, the
Xcompute process continues at step 305 by comparing the
difference between Xpeakl and Valley to the value of
Xpeakl divided, for example, by four. If the difference is the
greater of the two, then the difference between Xpeak2 and
Valley is compared to the value of Xpeak2 divided, for
example, by four. If the difference is greater than the
dividend, the Xbutton is set to Down at step 310. Otherwise,
the value of Xbutton is set to Up at step 315. The comparison
described above is provided to ensure that a legitimate
valley and two legitimate peaks have been detected, to avoid
artifacts. It will be appreciated, given the teachings herein,
that other comparison methods or divisors other than four
may be used for this purpose.
The Xcompute loop then ends at step 320. It will be
appreciated by those skilled in the art that the foregoing is

Definition

Xpeak2

Variable ta stare the value af the secand peak X value
(if any).
Xsum
Variable to accumulate the sum of the X values, for
centroid calculation.
XweightSum Variable ta accumulate the sum af the X values, weighted
by N (the pasitian af the canductor), for centroid
calculation.
Xstate
A variable which can have values Peak1, Valley, Peak2 or
Tail, ta indicate which part af the finger profile we are
currently searching far. The Tail state is simply the
remainder af the scan after a secand peak (in the exemplary
embadiment) has been identified.

It will be apparent to those skilled in the art that the
"Ycompute" variables and constants differ only in replacing
X by Y.
The algorithm for Xcompute starts at step 200, followed
by initialization of variables at step 205. For Xcompute, the
variables initialized are N, which is set to zero, and the value
of X(O), which is also set to zero. In addition, Xpeakl,
Xvalley, Xpeak2, Xsum and XweightSum, are all set to zero.
In addition, the state of Xstate is set to Peakl.
At step 210 a loop, referred to as "Xloop" starts. The
purpose of Xloop is to calculate the X centroid, by accumulating the sum and weighted sum of the X values for all
the X conductors from one to Xcon. Thus, the loop typically
starts with the value of N=O and increments by one at the
beginning of each cycle until the value of N=Xcon. The
steps of the loop include step 215, where N is incremented
to N + 1 and the value X(N) of the current conductor is added
to the prior accumulated value, Xsum, which then becomes
the new value of Xsum. The loop then continues at step 220,
where the prior value of XweightSum is added to a weighted
value of X(N), where the weighting is done by multiplying
X(N) by the number N of the conductor being sampled. The
sum of XweightSum and N*X(N) then becomes the new
value of XweightSum.
The XLoop continues at step 225, where one of a series
of subloops is selected depending on the value of Xstate.
Since Xstate is initially set to Peakl, the first subloop
entered is the Peakl subloop, beginning at step 230. At step
230 the value of X(N) is compared to the value of X(N-l)
and, if X(N) is greater than or equal to the value of X(N-1),
the first peak has not yet been reached. As a result, the loop
jumps to step 235, at which points the value of N is
compared to the value of Xcon. If the finger-induced capacitance measured at the last conductor has not been evaluated,
the result is a NO and the process jumps to step 215 to repeat
with an incremented value of N.
At some value of N the value of X(N) is less than the
value of X(N-1), at which point the check at step 230 yields
a NO. At this point, the peak has been found and at step 232
the value of Xpeakl is set to X(N-1) and the value of Xstate
is set to Valley. The system then jumps to step 235, where a
check is made to see if the last conductor has been measured
by comparing N to Xcon. As before, if the capacitance
change measured at the last conductor has not been checked,
the result is a NO, and the process loops to step 215 and
repeats.
When the process begins with the next increment of N, a
NO will result at step 225, so that the process will jump to
step 250, where a check is made to see if Xstate equal
Xvalley. Since it now does, a YES results and the process
branches to step 255. At step 255 a X(N) is compared to
X(N-l). If X(N-l) is not greater than or equal to X(N), the
valley has not yet been found, causing a further jump to step

5

10

15

20

25

30

35

40

45

50

55

60

65

5,825,352
11

12

example, relative movement of the first finger, together with
a simplified algorithm and does not include compensation
a tap of the second or more fingers at some point, followed
for settling, moisture and noise. Noise thresholding may be
either by removal of both fingers, further movement of the
provided in at least some embodiments, if noise causes the
first finger, or further movement of both fingers. Such
curve to be non-monotonic; settling and moisture may be
5 sequences can, essentially, be viewed as a series of scans in
dealt with in a similar manner.
which one or more fingers were found to be either present or
The Ycompute loop is performed similarly, as noted
absent in any given scan, with motion, or lack thereof, of the
above. Depending on the particular arrangement desired,
finger or fingers across the touch sensor interspersed
and the associated hardware, the X and Y compute processes
between changes in the number of fingers in contact with the
may be performed sequentially in either order or concur10 touchpad. The specific sequence can then be analyzed to
rently.
determine whether only a cursor movement is involved or
While the foregoing example describes identification of
whether a control function is intended. If a control function
minima and maxima in the X and Y directions, it will be
is intended, the specific control function can then be idenapparent that an analysis along a diagonal or some other
tified.
angular direction may be preferred in some instances, and is
Referring to FIGS. 7A-7F, there is shown in diagramstill within the scope of the present invention.
15 matic form an exemplary sequence involving operative
It will be appreciated that the foregoing describes a new
coupling of a plurality of fingers with a touch sensor to cause
and useful method and apparatus for detecting a plurality of
both a cursor movement and a control function. More
fingers operatively coupled to a touch pad sensor for
specifically, FIG. 7Ashows a series of movements of one or
enabling a variety of mouse-like operations. A second pormore fingers across a touch sensor, including various finger
tion of the invention involves using the previously detection 20 taps. FIGS. 7B-7F show, for each of the numeric references
methodology to perform various cursor movement and conin FIG. 7A, an exemplary video display, an exemplary
trol functions similar to those well known to users of
position of one or more fingers on the touchpad, and X and
Y finger profiles appropriate to that finger contact. It will be
electronic mice and trackballs.
helpful to define certain conventions used in FIGS. 7A-7F
As previously noted, the first finger is most commonly
associated, in the prior art, with cursor movement, while 25 before discussing these figures. In FIG. 7A-7F, contact
various tapping motions [e.g., tap and tap-and-a half] of that
between a finger and the touch pad is indicated by a solid
first finger have been implemented to perform various
circle within the fingertip; an absence of contact between a
fingertip and the touch sensor is indicated by the absence of
control functions. Unlike such prior art, however, various
movements (including sequences of taps) of additional fincircle within the finger tip. A tap-i.e., an up and down
gers or combinations of the first and additional fingers are 30 motion-by a finger is indicated by a dashed circle. Moveprovided to enable such control functions in the present
ment of the fingers from a first to a second point while in
contact with the touch sensor is indicated by a solid arrow.
invention. Depending on the implementation desired, it is
also possible to implement a superset of the prior art control
Movement of the fingers from a first to a second point with
functions together with the more robust control function set
the fingers not in contact is indicated by a dashed arrow.
35 With these conventions in mind, FIGS. 7A-7F can be better
available with the present invention.
Note that in the preferred embodiment, the user may
understood.
arbitrarily choose which finger he or she uses as the "first"
In particular, and with reference to FIG. 7A in combinaor "second" or additional fingers. Thus, for example, one
tion with FIG. 7B, an initial series of scans 700 indicates the
user may choose the index finger as the first finger and the
presence of a single finger in contact with the touch sensor,
middle finger as the second finger, while another user may 40 with the changing X,Y location between 700 and 705
prefer the reverse or some different combination. In the
indicating relative motion by the finger across the touch
preferred embodiment, the only distinction between the first,
sensor. At 710, a second finger is detected in contact with the
second and additional fingers is the sequence in which they
touch sensor, and continues to be operatively coupled to the
are placed in contact with the touchpad surface, or removed
sensor for several more scans without significant relative
from it. In any case where a second or additional finger or 45 motion across the sensor. At 720, the second finger is
fingers is placed down after a first finger, or multiple fingers,
removed, while the first finger remains. From 720 until 730
is already in contact with the pad, the newly placed fingers
(shown in FIG. 7C) the first finger continues its relative
can be in any relationship to those already in contact with the
motion, while at 740 the second finger is again placed down.
pad, such as to the left, to the right, above or below. The only
The scans of the sensor then detect both the first and second
requirement is that, in the profile of finger-induced 50 finger being moved together across the sensor until the scan
capacitances, the profile of the newly placed finger exhibits
at 750, then both fingers are removed at 755. Thereafter,
a zero value or a local minimum on each side of its peak
both fingers are again placed on the sensor at 760 (shown in
value, in at least one of the X or Y directions, so that it may
FIG. 7D), where they remain for a few more scans until 770,
be distinguished from the other finger(s) in contact with the
at which time they are both removed. Three fingers are
touchpad.
55 placed on the sensor at 780, and removed a few scans later
In particular, the ability of the previously described methat 790. Thereafter, three fingers are placed on the sensor at
odology to recognize multiple fingers allows the first finger
800 (FIG. 7E), moved across the touch sensor for a few
to serve, essentially, as the "point" finger, while additional
scans from 800 to 805, and are then removed at 810. Finally,
fingers serve as the "click" finger(s). Combinations of the
as shown at 820 (FIGS. 7FI-2), one finger is placed down
first, second, and perhaps additional fingers can then enable 60 while the adjacent finger is moved, such as might be
numerous conventional functions to be performed based on
desirable for marking text or other functions. When the
the mapping of a variety of sequences of taps or finger
finger is moved as far as is practicable, the moving finger is
picked up at 825 and placed down again at 830 for further
movements to a set of conventional pointing device
functions, where the pointing device could be a touchpad,
movement. The moving finger can be picked up and placed
mouse, trackball, joystick, or stylus, for example. It will be 65 down again as often as desired. Eventually the other, subapparent to those skilled in the art, given the foregoing
stantially fixed finger is lifted at 835, causing a "button up"
description, that the present invention can detect, for
condition.

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14

While the foregoing sequence can be programmed to
define any number of cursor movement and control
functions, an exemplary definition of the functions associated with such sequences can be the following: For the
period from 700 through 705 the relative motion of a single
finger can be defined to mean cursor movement for that
period, from the beginning point until the relative ending
point. During the period 710 to 720, a second finger is
detected and then removed, which is defined in an exemplary embodiment as a single finger tap which may be a
"select" function such as selecting one item from a screen
menu. During the period 720 until 730, the single finger
again moves the cursor, while at 740 the second finger
reappears to enable a different function. The second finger
moves across the sensor, together with the first finger, until
at 755 both fingers are removed. Again, such sequences-all
of which may be regarded as gestures-can be mapped to
control functions in numerous ways, but one reasonable
definition is that the presence of two fingers engaged in
relative motion is a "drag function," such as where an entity
was selected by the first tap and dragged to a new location,
where it is dropped by the removal of both fingers at 750.
Then, at 760, both fingers reappear and remain for a few
additional scans until both are removed at 770. This gesture,
which may be considered a "two finger tap," can enable
numerous functions, but an exemplary definition is the
classical "double-click" of a standard left mouse button, or
the click of a middle button on some three button mice, such
as those sold by Logitech, Inc., and could, for example,
activate a function or application associated with the item to
which the cursor is pointing.
Next, the sequence from 780 to 790, when the three
fingers reappear and are then removed, is a "three finger
tap", and can be regarded, for example, as a right mouse
button click which may, for example, activate a menu
specific to the item to which the cursor is pointing. Finally,
the sequence from 800 until 810, in which three fingers
reappear, move across the touch sensor and are then
removed, may in an exemplary embodiment be seen as a
shortcut to a multi-sequence function. For example, such a
movement might be defined as a scroll function, which
might otherwise require the user to move the cursor to a
scroll bar, drag and drop a scroll box, and return the cursor
to the working area of the screen. Finally, the sequence from
820 through 830 can be analogized to holding down a mouse
button (for example the left mouse button), rolling a mouse
whatever distance is convenient for the user, then picking up
the mouse (while continuing to hold down the button) and
placing the mouse down again at a position convenient for
further movement of the mouse. One example of the use of
such a sequence is the marking of text. The algorithm for
recognizing movement by one "cursor" finger while the
other "button" finger is maintained in position is a generalized case of the algorithm shown in FIGS. 5 and 6, and is
described in greater detail in FIGS. 8 and 9. Other functions
which can be implemented with such gestures include an
"ink" function (mentioned above), entry of variable values,
and use of the sensor in absolute mode.
Referring next to FIGS. 8 and 9, the generalized case
associated with FIGS. 7FI-2, but also applicable to the
remaining functions, may be better appreciated. In the
exemplary algorithm shown in FIGS. 8 and 9, a determination is made whether zero, one or two fingers are in contact
with the touchpad. Depending on how many fingers are
identified, various operations are permitted. It will be appreciated that FIG. 8 is analogous to FIG. 5, while FIG. 9 is
analogous to FIG. 6. For convenience, steps unchanged from

FIGS. 5 and 6 are in most cases referred to by the reference
numerals used in those figures.
In FIG. 8, the process begins in a manner identical to FIG.
5, starting at step 400 and followed by scanning the conductors and storing the results of the scan in memory at step
405, followed by Xcompute and Ycompute at steps 430 and
440, respectively. For this embodiment, Xcompute is shown
in FIG. 9, and Ycompute is identical to Xcompute. At step
850, a determination is made whether two fingers are in
contact with the touchpad by evaluating both Xcompute and
Ycompute. If neither Xcompute nor Ycompute indicate the
presence of two fingers, the answer is NO and the process
drops to step 855. However, if either the Xcompute routine
or the Ycompute routine indicates the presence of two
fingers, the answer at step 850 is YES and the process moves
to step 860, where the value of the variable FINGER is set
to 2.
If the answer at step 850 was NO, then a determination
has to be made at step 855 whether one or no fingers are in
contact with the touch sensor. If variables Xfinger and
Yfinger do not both equal 1, then the comparison at step 850
is a NO and it is determined that no fingers are in contact
with the touch sensor. In this case, the variable FINGER is
set to 0 at step 865. However, if the variables both yield a 1,
then a determination is made that one finger is in contact
with the sensor, and the variable FINGER is set to 1 at step
870.
In either event, the process then moves to step 875, where
Xmotion and Ymotion are calculated in a manner identical
with FIG. 5. The process then continues at step 880, where
the variable Finger is compared to the value of FingerPrevious. If the value of Finger differs from the value of
FingerPrevious, then a button actuation is assumed to have
occurred, and Xmotion and Ymotion are set to zero at step
885. However, if the value of Finger equals the value of
FingerPrevious (i.e., the current number of fingers contacting the pad is the same as in the previous state), then the
comparison of step 880 yields a YES, and the process moves
to step 890. At step 890 a comparison is made to determine
whether there has been motion in either the X or Y directions. If neither Xmotion nor Ymotion is nonzero, a NO
results and the process moves to step 895 where the variable
Motion is set to NO. The same results obtains if the process
goes through step 885. However, if either Xmotion or
Ymotion is nonzero, a YES results at step 890, and the
process moves to step 900 where the variable Motion is set
to YES.
From either step 895 or step 900, the process moves to
step 905, where a check is made to determine whether
ButtonPrevious was up and the number of fingers detected
is two. If the answer is NO, the process moves to step 910.
However, if a YES is obtained, the process moves to step
915 where the state of the Button variable is reported to the
host as DOWN, and the variable ButtonPrevious is set to
Down.
Referring again to step 910, a check is made to determine
whether either of two groups of conditions exist. A YES
result may be obtained if ButtonPrevious is DOWN and and
the value of the Finger variable is zero; or if ButtonPrevious
is Down and the variable Motion is set to YES and the
variable Finger is set to one. If none of these conditions
exist, a NO result is obtained and the process moves to step
920. However, if a YES does result, then the process moves
to step 925 and reports to the host that Button is Up, while
also setting the variable ButtonPrevious to Up.
If a NO resulted at step 910, at step 920 a comparison is
made between variables FingerPrevious and Finger, and the

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5,825,352
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state of the Motion variable. If FingerPrevious is the same
finger or fingers across the touch sensor, to evaluate those
value as Finger, and Motion has occurred (i.e., Motion is
sequences either locally or via software on the host, and to
Yes), the process moves to step 930 and both Xmotion and
report appropriate signals to cause cursor movements or
Ymotion are reported. The process then moves to step 935.
control functions to occur in applications programs or operHowever, if the comparison at step 920 yields a No, the 5 ating environments.
process moves directly to step 935. At step 935, the value of
Having fully described various embodiments of the
XabsolutePrevious is set to the value of Xabsolute, the value
present invention, numerous alternatives and equivalents
ofYabsolutePrevious is set to the value ofYabsolute, and the
which do not depart from the invention will be apparent to
value of FingerPrevious is set to the value of Finger. The
those skilled in the art. It is therefore intended that the
process then moves to step 940, where it recycles by 10
invention not be limited by the foregoing description, but
jumping back to start.
only by the appended claims.
Referring next to FIG. 9, the Xcompute process is shown
What is claimed is:
in detail for the generalized case shown in FIG. 8. As noted
1. A method for detecting the operative coupling of
previously, the Ycompute process is identical and is therefore not shown separately. The process of FIG. 9 is identical 15 multiple fingers to a touch sensor involving the steps of
to that shown in FIG. 6 up through step 290, and the
scanning the touch sensor to (a) identify a first maxima in
preceding steps will therefore not be discussed again.
a signal corresponding to a first finger, (b) identify a
However, if a No results from the comparison at step 290, a
minima following the first maxima, (c) identify a
determination is made that no fingers are in contact with the
second maxima in a signal corresponding to a second
pad. This causes the variable Xfinger to be set to zero at step 20
finger following said minima, and
970.
providing an indication of the simultaneous presence of
Steps 295 and 305 are unchanged from FIG. 6 and will not
two fingers in response to identification of said first and
be discussed further. However, if a No results from the
second maxima.
comparison at step 305, then a determination is made that
2. The method of claim 1 further including the step of
one finger is in contact with the sensor, and the value of the 25 causing a pointing device click function to occur in response
variable Xfinger is set to one at step 975. By contrast, if the
to the detection of at least a second maxima.
result at step 305 is a Yes, then a determination is made that
3. The method of claim 1 further including the step of
two fingers are in contact with the sensor and the variable
enabling a "drag" function to occur in response to the
Xfinger is set to two at step 980. Regardless of the number
detection of at least a second maxima.
of fingers in contact with the sensor, the process moves to 30
4. The method of claim 1 further including the step of
step 320 and ends until the next cycle.
enabling a "select" function in response to the detection of
Another function achievable with the detection method
at least a second maxima.
and apparatus of the present invention may be referred to as
5. The method of claim 1 further including the step of
edge lock. Because a touch sensor can detect, in absolute
enabling an "ink" function in response to the detection of at
terms, where on the sensor the operative coupling occurs, it 35 least a second maxima.
is possible to detect that one or more fingers have reached
6. The method of claim 1 wherein said touch sensor
the edge of the sensor. In some instances, the user intends to
includes a plurality of lines, said maxima being a largest
continue the movement he was engaged in when he hit the
local variation in a signal value on one of said lines due to
edge; for example, a drag function involving two fingers, in
capacitive coupling of a finger.
which the two fingers hit the edge before the object being 40
7. The method of claim 6 wherein said maxima are peaks.
dragged has reached its destination. In the environment of a
8. The method of claim 1 further comprising the step of
mouse, the user simply picks up the mouse while holding the
comparing a distance between said first maxima and said
button down, puts it back down and moves again. In the
second maxima to a predefined threshold.
context of a touchpad, however, removal of the two fingers
9. The method of claim 1 further comprising the steps of:
may be perceived as termination of the function even though 45
providing a first control function in response to the
such termination was not intended. To avoid such problems,
detection of the movement of two fingers:
the function in which the user was engaged at the time the
detecting the reaching of an edge of said touch sensor by
fingers hit the edge may remain active-i.e., locked in-for
said two fingers;
a delay period. If the fingers are placed down on the
touchpad within the delay period, the user continues with the 50
detecting a first time corresponding to the removal of said
earlier function. If the user does not place down the fingers
fingers from said touch sensor;
within a predefined delay, the function is terminated and a
detecting a second time corresponding to the replacement
new function begins when the user again places the fingers
of said two fingers on said touch sensor; and
in operative contact with the sensor.
continuing said first control function if said first and
It will be appreciated from the foregoing that the present 55
second times are within a predetermined time limit of
invention allows numerous multi-finger gestures to be
each other.
detected and converted to mouse-related functions for mov10. The method of claim 1 further comprising the step of:
ing a cursor and control of operating environments or
detecting a distance between said first and second
applications programs. However, while some exemplary
maXIma.
functions and exemplary definitions for particular sequences 60
11. The method of claim 1 further comprising the step of:
have been provided above, it is to be understood that the
providing a drag control function in response to detecting
present invention is not limited to the association of a
a movement in substantial unison of two said fingers.
particular function with a particular sequence or to any
12. The method of claim 1 further comprising the step of:
particular set of functions. Instead this aspect of the invention is directed to the ability to identify and process various 65
providing a click function in response to the removal and
sequences in which one or more fingers are either absent or
reappearance of said second maxima within a predepresent, interspersed with motion or lack of motion of the
termined period of time.

5,825,352
17

18

13. The method of claim 1 further comprising the steps of:
23. The touch sensor of claim 18 further comprising:
means for providing a first control function in response to
detecting a movement of said first maxima;
the detection of the movement of two fingers:
detecting a removal and replacement of said maxima
means for detecting the reaching of an edge of said touch
within a predetermined time period;
sensor by said two fingers;
5
controlling a cursor function in response to said movemeans for detecting a first time corresponding to the
ment of said first maxima; and
removal of said fingers from said touch sensor;
providing a control function in response to said removal
means for detecting a second time corresponding to the
and replacement of said second maxima.
replacement of said two fingers on said touch sensor;
and
14. The method of claim 1 further comprising the step of: 10
means for continuing said first control function if said first
selecting an appropriate control function based on a
and second times are within a predetermined time limit
combination of a number of fingers detected, an
of each other.
amount of time said fingers are detected, and any
24. The touch sensor of claim 18 further comprising:
movement of said fingers.
15
means for detecting a distance between said first and
15. The method of claim 1 further comprising the step of
second maxima.
determining if said first and second maxima are within 5
25. The touch sensor of claim 18 further comprising:
centimeters, and only providing said indication of the presmeans for providing a drag control function in response to
ence of two fingers if said first and second maxima are
detecting a movement in substantial unison of two said
within 5 centimeters.
20
fingers.
16. The method of claim 1 further comprising the step of
26. The touch sensor of claim 18 further comprising:
calculating first and second centroids corresponding to said
means for providing a click function in response to the
first and second fingers.
removal and reappearance of said second maxima
17. The method of claim 1 wherein said first and second
within a predetermined period of time.
maxima are required to be higher than a first threshold, and 25
27. The touch sensor of claim 18 further comprising:
said minima is required to be less than a second threshold.
means for detecting a movement of said first maxima;
18. A touch sensor for detecting the operative coupling of
means for detecting a removal and replacement of said
multiple fingers comprising:
maxima within a predetermined time period;
means for scanning the touch sensor to (a) identify a first 30
means for controlling a cursor function in response to said
maxima in a signal corresponding to a first finger, (b)
movement of said first maxima; and
identify a minima following the first maxima, and (c)
means for providing a control function in response to said
identify a second maxima in a signal corresponding to
removal and replacement of said second maxima.
a second finger following said minima, and
28. The touch sensor of claim 18 further comprising:
means for providing an indication of the simultaneous 35
means for selecting an appropriate control function based
presence of two fingers in response to identification of
on a combination of a number of fingers detected, an
said first and second maxima.
amount of time said fingers are detected, and any
19. The touch sensor of claim 18 further comprising:
movement of said fingers.
29. The sensor of claim 18 further comprising means for
means for selecting an appropriate control function based
on a combination of a number of fingers detected, an 40 determining if said first and second maxima are within 5
centimeters, and only providing said indication of the presamount of time said fingers are detected, and any
movement of said fingers.
ence of two fingers if said first and second maxima are
20. The touch sensor of claim 18 wherein said touch
within 5 centimeters.
sensor includes a plurality of lines, said maxima being a
30. The sensor of claim 18 further comprising means for
largest local variation in a signal value on one of said lines 45 calculating first and second centroids corresponding to said
first and second fingers.
due to capacitive coupling of a finger.
21. The touch sensor of claim 18 wherein said maxima are
31. The sensor of claim 18 wherein said first and second
peaks.
maxima are required to be higher than a first threshold, and
22. The touch sensor of claim 18 further comprising
said minima is required to be less than a second threshold.
means for comparing a distance from said first maxima to 50
said second maxima to a predefined threshold.
* * * * *