Apple Inc. v. Samsung Electronics Co. Ltd. et al
Filing
561
Declaration in Support of #559 Declaration in Support, filed byApple Inc.. (Attachments: #1 Exhibit 3.02, #2 Exhibit 3.03, #3 Exhibit 3.04, #4 Exhibit 3.05, #5 Exhibit 3.06, #6 Exhibit 3.07, #7 Exhibit 3.08, #8 Exhibit 3.09, #9 Exhibit 3.10, #10 Exhibit 3.11, #11 Exhibit 3.12, #12 Exhibit 3.13, #13 Exhibit 3.14, #14 Exhibit 3.15, #15 Exhibit 3.16, #16 Exhibit 3,17, #17 Exhibit 3.18, #18 Exhibit 3.19, #19 Exhibit 3.20, #20 Exhibit 3.21, #21 Exhibit 3.22, #22 Exhibit 3.23, #23 Exhibit 3.24)(Related document(s) #559 ) (Jacobs, Michael) (Filed on 12/29/2011)
EXHIBIT 3.15
.
initiated
by
a
touch
on the surface.
oetween the arrival ož the echo and
transmission
of
the
the
The time intervals
beginning
of
the
source signal, measured in two direc-
tions as shown Fig. 2.3 give the information on the position
of
the
object.
The touch sensor shown Fig. 2.3, developed
by T.S.D Limited (ref 2.4], actually provides outputs of x+y
and 2y enabling the derivation of x and y where x and y are
the distance horizontally from .a vertical
edge
and
verti-
cally from a horizontal edge respectively.
Video Technique:
The video approach to the touch input device uses a T.V
camera
to
is placed.
scan a translucent plate on which the finger tip
The signal from the TV camera is then
processed
to obtain one bit of information per pixel.
Using a pro-
grammable threshold voltage, one bit per pixel
is
to determine
the plate.
obtained
the shape of a 2-D projection of an object on
The data resulting from this process are
stored
in a memory to which access by a dedicated processor is
allowed. This processor implements further processes such as
determining non-zero locations in the memory (that is, the
position of the object) and identifying shapes (groupíng the
pixels for an object).
Nimish Metha presented such a system
[ref 2.5) whose basic configuration is shown in Fig.
2.4.
Capacitive:
2-5
APLNDC00026340
CURVED GLASS SCREEN
ACTivE AREA
PIEZOELECTRIC TRANSDucERS
RECEtVER
--
- -3
CONTROL LINES
PARALLEL OUTPUT
X-Y POSITIONS
PARALLEL OUTPUT)
TIMING
OtGITAL
CONTROLLER
ECHO OUTI
SERIAL OUTPUT
I
\·
\
\
POWER
L..-OP1tONAL
TIMING
PtEZOELECTRIC
TRANSDUCERS
TRANSMITTER
Fig. 2.) Block Diagram of Touch Screen Digitizer
APLNDC00026341
att Eitt AT
t(i Y
sirit 11 .
'KL YtinAhll'
AkiA
I
\.
\ \
\ \
/
I
/
/
/
/
TV CAMENA
un iPUT
lit.V itt
il Ni i
COMPUTER
Fig. 2,4
Video System for Touch Tablet
APLNDC00026342
Capacitive sensors are
such
as
used
in
various
single touch switches and touch tablets. Two kinds
of touch tablet using capacitive sensors
here.
applications
The
be
examined
one developed by TASA (ref 2.6) shown in Fig 2.5
measures the capacitance between
covered
will
by
the
plate
and
the
area
the touch. This measured datum is then compared
with a previous reading stored in a shift register. In order
to reduce the
size of
the shift
register, a tablet is
divided into many sub-regions in which the position
touch
is
uniquely
located.
the .
One· such sub-region is much
larger than the maximum size of a
avoid
of
single
touch
so
as
to
an overflow. TASA utilizes the sensor to detect rela-
tive movements of a.finger rather than
its
absolute
posi-
tion.
Another capacitance tablet developed by Sasaki,
kow
and
others at the University of Toronto (ref 2.8] uses
sensors for the rows and columns which
shown
in
Fedor-
Fig 2.6.
are
interleaved
as
It uses analog multiplexors to select a
row or a column sensor.
In order to find the capacitance of
a row or a column, it counts the time to charge up the capa-
citive sensor.
the
Because the capacitance of
the
sensors
on
tablet without a touch is not constant, and the capaci-
tance change produced by a touch is
pared
to
the
capacitance
relatively small
com-
of the surroundings, the system
uses a neasure of the initial capacitances of the sensors
without
touch
)
(
whose values are stored in the memory.for
2-6
APLNDC00026343
The couch point is determined by finding
ereancemaximum difference
a
sec
values (current value less the
reference value) for the rows and columns.
2.3 SHORTCOMINGS OF EKISTING DEVICES
The scanning properties of the devices described in the
previous
section
can
be
distinguished depending on their
position, pressure and multiple touch sensing
All
the
devices
or
capabilities.
transducers referenced are capable of
locating the position of a touch, with a resolution which is
characteristic of each device.
Only capacitive sensors and
the MIT resistive sensor provide pressure of
touch whereas
the video system and the MIT tesistive sensor give a multiple touch capability.
Projective sensors, that is, all of the sensors
duced
intro-
in the previous section except the video system and
the HIT high resolution resistive sensor, cannot detect multiple touches without ambiguity since the detection of touchby two horizontal and two vertical
sensors
can be
inter-
preted in seven possible ways as shown in Fig, 2.7.
In general, the missing data may be retrieved by intro-
ducing more axes, as is done in a tomographic imaging system.
Using this scheme, if the upper limit of the number of
touch points is
tWor
the
introduction of one more axis
2-7
APLNDC00026344
.L
herial In Shift
2egister (Previous)
Pattern Comparison Motion
Detection
Parallel Load Shift Register
(Present)
Etc
Etc
Touch Surface Sensor
Touch Jensitive Circuitry
Down Count
Up Count
Finger not Moving
Finger Moving U
Finger Loving Down
Fig. 2.5
Block and Time Diagram of TASA Touch Tablet
APLNDC00026345
I
SENSORS
COLUMN SEliSORS
Fig. 2.6 Capacitive Sensor Configuration
of the U of T Touch Tablet
5
APLNDC00026346
ciearly òistinguishes at least two points as shown
in
to
the
number
to
an
of touches is not assumed.
which the number of touches is more than two
(c)
anò
Fig 2,7. .At least two additional axes are required
istinguish two points without ambiguity if
limit
(a)
(g) in Fig. 2,7,
are
upper
Cases in
shown
in
But as soon as the number of axes
is increased, the attraction of any scheme of 2-d projection
diminishes .because the cost of implementation rises greatly.
For example the.capacitive tablet may
mentable
an
unimple-
number of wire layers whereas introduction.of sen-
sors and sources
extremely
require
for
diffidult.
IR
and
Moreover
Ultrasound
schemes
may
be
as the number of the touch
points increase, additional axes do not help in resolving
.
basic
shortcoming
a
of the sensor from which only on and off
information is available.
This is the existence..of a region
for which identification of points inside is not possible as
shown Fig. 2.8.
The video technique
seems to solve
all
the
problems
embedded in all of the "projective sensor" systems.including.
pressure if
corresponds
"area of -touch" by a
to
the
pressure.
compressible finger
But a video system is quite
bulky due to the optical enclosure and it is slow because it
has
to
access the data stored in memory by the camera pro-
cessing unit. The maximum speed is limited by the scan
rate
of the camera(30 per second) even though this maximum can be
achieved only by pipelining all the processes required.
2-8
APLNDC00026347
(¿.)
Éetection of touch by row
sensors (c), (b) :.nd colue:n
sensors (c), (d) can be
.interpreted in 7 possible a ye
(b)
r.s shown below.
I
(c)
(d)
A
e
C
D
I
E
F
ig. 2.7 i ossible sets of points whose e::istenev :.: y 40
implied by two sensors on both row r na coluran.
APLNDC00026348
Fig. 2.8 Concave touch points that block the points inside.
Any point or g,roup of points within the shaded
region cannot be identified by any number of
projections.
APLNDC00026349
AGES TO THE PROBLENS
Dae concludes from the previous discussion that
ing
systens and devices òo not provide an appropriate means
to reach our goal.
sor
exist-
is
The major problem of the projective sen-
generally
the ambiguity on multiple points,
As a
solution to this problemt multiple axes are required.
however,
This
increases the cost as well .as the number of points
to be scanned.
guity within
Furthermore it cannot
regions of
reasonable number of axis.
eliminate
the
ambi-
"concave touch points" using any
On this basis,
all
projective
methods must be discarded.
One idea of some significance that can be introduced is
to avoid scanning all the pixels in the tablet which contain
no information.
For example, scanning all 2048 points of
a
tablet having a resolution 64 by 32 for fewer than 10 points
is really quite a ridiculous
number of
approach.
In
fact,
if
the
the points to be searched is comparably small,
then an improved algorithm, here called binary scanning, can
be used. .It is described as follows.
Consider a plane of a tablet with resolution 8 by 8
be searched
for
a
to
touch point as shown in the Fig. 2.9.
First, check the tablet for touch as a whole region as shown
by the area ABCD in the figure. If touch is detected, divide
the tablet into two equal regions shown by the line
EF
and
check each of the two regions ABEF anã EFCD žor toucheòness.
2-9
APLNDC00026350
region, region EFCD
c:t ©
in
this
case,
and
coucha two equal regions as shown by the divisi.on
enis into
Continue this PEO~
aavido
the touched regio •
Isac Ug, select arther division is Possible, that is, until a
cess until
designated as the region PKNO in gig.
2.9,
16
"gg sensorThe figure also shows the sequence of suodivisi
reached•
eration. Rote details Of.this algo
in the binary scanning CP
githm are given in chapter 4.
Using this algor
tablet
e aon
6a4 bhy- 3
r gneires tntentyn
a
having
scanning times:
2*1092(64*32)=22
el
dn
p
e1 s a
9
Une
o
Bethe time that it would take to detect one
touch
if
all pixels are scanned one by one linearly is
64*32
N=-----=186.
22
This shows immediately that the binar he nanm eDr Ofmethond
is
much a Pacior to linear scanning
be scanned is fewer than 186.
2-10
APLNDC00026351
s
s
(1)
N
t
‡x
L
c
(2)
Fig. 2.9 Binary scanning operation.
(n)-Sequence of subdivision in binary operation.
APLNDC00026352
-ror example the speed gain.over
cae nu
linear
scanning
when
i of points is ten is
64*32
-----=9.3
22*10
That is, for 10 points binary scanning is
-
about
9,3
times
faster than linear scanning.
Now compare such a 64*32 binary scanning tablet with a
2-d projective touch tablet such as used in the HP Personal
Computer Input Screen, or with the capacitive
single
touch
tablet with 64 by 32 resolution. In each case the speed gain
for detection of a single touch is -
64+32
22
-4.36
or a'oout 4.3. That is, the binary scanning tablet is
tially
4.3
poten-
times žaster than one žor which only sequential
scan is possible.
Even if the binary scanning algorithm is applied to the
projective
tablet, the speed for the projective tablet will
not exceed the speed of the 2-d image tablet.
The
scanning
time for a projective tablet having the same resolution is
found as follows; Since there are 64 + 32 sensors only,
and
the binary scanning algorithm is.applied to the row and the
colu¤n sensors separately, the scanning time is
2-11
APLNDC00026353
-
;•1oß2(64)+2*lo92(32)=22
Thus the binary scanning algorithm seems to be
attractive
one
tot
application to the FHTSID.
a
very
However it
necessitates two special hardware features:
--
1. Unlike the projective sensor system which allows to
address only a group of positions in a column or a row,
all individual positions of m by
n
tablet
should
be
addressable.
-- 2. It should be able to group
a
numbet
of
adjacent
The first requirement is to permit sensing of
multiple
sensors as one larger sensor region.
touches,
cithm.
of the
the
second
allows
for the binary scanning algo-
In addition to these necessary features,
intensity
a measure
of touch should be considered as a third
requirement to increase the capability of the FMTSID.
The sensors
that can possibly
accommodate , these
requirements are many. However the degree of dižficulty in
implementation varies one to
various
sensor
types
another.
In
the
following,
are examined in view of the require-
ments identified above.
A resistive image sensor can
modification
of
the
be
used
with
a
slight
multiplexor as shown in the Fig. 2.1,
2-12
APLNDC00026354
. .
novever far too much time-is required to evaluate the resistance
using
two port parameter calculations.
Besides, the
basic approach requires that all the row resistances have to
be
evaluated
once
using
linear scanning; that is, binary
scanning is not applicable to rowwise scanning. .
For the video system, the row and the
registers
column
scanning
are not accessible and with the video data stored
in memory, it is not possible to satisfy the second requirement,
Bowever the third requirement may be met by the addi-
tion of a little more hardware.
In general,
therefore,
it
is not a good choice.
None of the other devices presented
section
satisfy
in
the
previous .
the requirements.. Thus it is necessary to
identify further sensor types.
A resistive polymer (J.S,R) was examined (ref 2.7]. The
polymer
changes
resistivity with applied pressure. One of
the applications shown by J.S.R has two closely-placed,
separated,
metal coated plates on the PC board on which the
rubber sheet lies such .that if the rubber is
the
but
two plates are connected.
pressed
down,
This unit may 'oe used with a
lot of multiplexors to select one
of
all
sensors
on
the
board. However a problem with this sensor is that it takes a
very long time žor the material to recover
the
original
electrically
to
state after the žinger is released (about 100
maec).
2-13
APLNDC00026355
Piezoelectric material was also examined. One
approach
is
to
apply
the same hardware technique used in
keyboard applications.
inate
the
possible
However this approach does not elim-
multiplexing
problem.
Unfortunately during the
time required for multiplexing, the charge developed by
the
impact of the touch can be lost.
Finally, it seemed that the capacitive
the
greatest
sensor
offered
potential of all available approaches for the
following reasons:
-- 1. Capacitive sensors
ment,
that
is,
the
do not need
additional
equip-
basic insulating sheet and touch
plate are sufficient.
-- 2. Multiplexors for individual sensors can be
or
.are
degenerately
simple
using
row
and
avoided
column
addressing methods described in chapter 3
--
3,
Capacitive
sensors
features identified above.
can
accommodate
all
three
In particular, a measure of
intensity is available since the area ož finger contact
and
corresponding
capacitance
increases
with finger
pressure.
-- 4. Capacitive sensors are very durable since no additional
elements
are
needed
and there is no recovery
2-14
APLNDC00026356
time
phenomenon
involved
as
exists
with
resistive
rubber.
However there are some drawbacks to capacitive sensors.
First
they
require
time
to charge and.discharge. However
these times can be reasonably well controlled.
drawback
is
that
The
second
a capacitive sensor generates radio fre-
quency noise when the tablet is touched. The third
drawback
is low resolution. However the low resolution can be compensated by software technique as discussed in chapter 4. Noise
in
the
radio
problem in
frequency
spectrum,
some .environments,
operation of the tablet.
does
which is potentially a
not
deteriorate
the
Since level of the.noise could not
be known at the time of design, it was not considered
as
a
factor in the choice of sensor.
2.5 CONCLUSION
In this chapter, severai kinds of touch sensitive input
device
have
been
examined
as
a
part
of the process of
developing a flexible multi-purpose input device. Many devices
and
sensor
types
have been analyzed from different
points of view in order to achieve the desired goals.
With respect to the initial .goals of developing a flex-
ible multi-purpose input device,
it seems that the touch
tablet as
does. not žulfill the
conventionally defined,
2-15
APLNDC00026357
requiremenes
of
flexibility
and
aòaptability, out räther
that a fast multiple touch sensitive input
device
(E'MTSID)
must be pursued to meet the real requirements.
In oròer to reach this goal,
hardware
with
a
binary
capacitive
sensor
based
scanning algorithm was chosen for
development.
2-16
APLNDC00026358
•
cuan ER 3
HARDWARE DESIGN AND IMPLDIENTATION
3.1 INTRODUCTION
This
chapter
implementation
of
describes
a
the details of
the
hardware
fast multiple-touch-sensitive input
device ( FMTSID ). The design of the hardware
is
based
on
the hardware requirements identified in the previous chapter
and
on
hardware
and
tradeoffs
between
software
and
basically consists of a sensor
hardware.
The
matrix board,
cow
column selection registers, A/D converting circuits and
a dedicated CPU.
The design of the sensor matrix is based on
nique of
capacitance
measurement between a
and a metal plate. Row selection
more
registers
the
tech-
finger
select
one
tip
or
rows by setting the corresponding bits to a high state
in order to charge up the sensors while the column selection
registers
select
corresponding
one
analog
through
timing
selected
cows
selected
sensors
or
switches
resistors.
and
the
as
more
a
columns
to
by
discharge
turning
the
on
sensors
The intersecting region of the
selected
unit.
columns
A/D
represents
converting
the
circuits
3-1
APLNDC00026359
ce ene discharging time interval of the
selected
sen-
A University of Toronto 6809 board was used as dediced CPU.
The details of the sensor matrix design
section
3.2,
section 3.3.
used
in
with
the
are
given
in
rest of the hardware described in
Section 3.4 describes
the
scanning
sequence
conjunction with the hardware development process
while.section 3.5
concludes
with
a description
of
the
hardware implementation.
3.2 THE SENSOR HATRIX
The design and construction of the sensor matrix board
is
straightforward.
The touch surface of the sensor board
consists of number of small metal-coated
rectangular-shaped
areas serving as sensor plate capacitors.
The design of the
metal plate area of a unit sensor depends on the
capacitance
measurable
change that results when the area is covered by
a finger .tip, and on the resolution thaè.can be implemented.
A 12" by 16" sensor matrix area with a resolution of 32
by
64
sensor.
and
a
was
chosen, resulting in 7 mm by 4 mm area for each.
The estimated capacitance between the sensor
touching
plate
finger separated by 3 mil (0.075 mm) Mylar
insulating coversheet is
3-2
APLNDC00026360
A
-12
7mm*4mm
Cs=e-=3*.8.85*10
[F/m]
=10pF
d
0.075mu·
where
e
is
coversheet,
the
A
dielectric
is
the
area
constant
of
of
the
insulating
the unit sensor and d the .
thickness ož the insulating sheet.
The charge associated with
the
touch
capacitance -is
stored between the sensor plate and the touching finger act-
ing as ground.
sidered
to
be
For this purpose human beings
a
large
charge
can be con-
reservoir. For the static
charge case, a suitable model of a human being is an approximate
100 pF
capacitor with one plate connected to ground.
[tef 3.1] Therefore, it is safe to assume a touch as
ground
reference for measurement of relatively small capacitances.
The 10 pF of sensor capacitance
small
but measurable.
change
is
relatively
For a timing resistor of 100 k, the
time change due to the sensor capacitance change is about
micro-second.
The
tradeoff
between the time taken for the
measurement of the capacitance and the ease
seems
to
bé
obvious.
If
"easy" to measure but it
scanning
procedure.
The
1
the
takes
clock
of
measurement
capacitance is high, it is
longer,
cycle
slowing
used
down
the
to count the
discharging time is also limited by noise in the analog circuits
as
well as by timing limitations ož the TTL circuits
used. With these limitations in
mind,
the
period
of
the
counter clock was chosen to be 100 nano-seconds.
3-3
APLNDC00026361
n order to select a sensor by row and
òiodes
It is referred to
in Fig. 3.2.
ing
back
access,
were used for.each sensor. One diode, connected
: the row line, is used to charge uP
row.
column
to
The CD
the
dropped to zero. The
the
sensors
in
as the Charging Diode (CD) as shown
also serves to block the charge
row
the
line
other
when
diode
flow-
the row line voltage is
called
the
Discharging
Diode(DD), connected to the column.line, enables discharging
of the selected row sensors to a virtual ground. Also the DD
blocks charge flow from the sensors in the selected row to
the sensors in the unselected row during the discharging
period·
The
selection
of roWS, by the row selection pro-
cedure, causes the sensors to be charged. The sensors in the
column
are then discharged through associated timing resis-
tors connected to the column selection switches.
Fig 3.1 (a) shows the components associated with a
selected sensor.
There are two related time periods: One
for the selection of rows ( that i
and
the
other
'
s, tne charging period )
for the selection of columns ( that is, the
discharging period.).. The capacitance is.measured while the
sensor discharges. The signal output during discharging is
shown in Fig. 3.1 (b).
Analytic equations can be derived for the model
ing .that
the
assum-
reverse diode resistance is much higher than
the discharge resistor R and the forward resistance is
muca
3-4
APLNDC00026362
Charging diode
Discharging diode
(C)
a row line
SENSOR
a column line
a column selection
switch
Fig. 3.1 a. A model of a selected sensor in the
sensor agtrix
(A)
(8)
i
i
'
Vt
i
(O
hreshold
Voltage
Pl
P2
y-
instÅntaneous discharging
voltage
... ,
·¯¯¯" - - ---·
'
75 P3
hg. 3.1 b. The timing diagram for discharging time
measurement of a selected sensor as shown above.
APLNDC00026363
column lines
row lines
To
row
selection
register
sensor plates
harging diode
discharging diode
To
column
switch
selection
r
· --
4-timing resistor
--
... ...
column. selection
switches .
To adder
Fig. 3.2 A small sectio¤ of sensor matrix.
APLNDC00026364
n the discharge resistor R.
The derivation is as
a discaarging voltage ( V ) is given by
-t
V=Vi*exP(--1
T
where
Vi
is
the .instantaneous
initial
voltage
of
the
discharging period and T is the time constant.
T is given by
T=R(Cs+Cr)
where Cs is the sensor capacitance and Cr
is
the
reverse
bias capacitance of the diode.
The voltage Vi can be found from
Cs
Vi=(
Os-Of
)(
Cs+Cr
)(Vcc-Vd)
Os
where Os and Of are respectively the charges stored
sensor
and
the
forward
biased
diode
discharging period begins, and Vcc and Vd
the
just
are
in
the
before
the
respectively
high state voltage for CHOS and the diode voltage drop.
In the equation for Vi, the first factor is associated with
charging
up a reverse biased diode while the second factor
results from the charge in the forward biased diode
stored
3-5
APLNDC00026365
the charging period.
The.discharge time is measured by the comparison with a
chgeshold voltage ( Vt ) and it is given by
Vt
Ts=-T1n(---)
Vi
From these analytic equations,
sions
the
following
conclu-
relating to the selection of appropriate voltage lev-
els and .the diode type can be made.
-- 1. The higher the Vec, the less sensitive is the measurement to the threshold voltage at V = Vt where the Vt
= aVcc and the sensitivity,that is the derivative of
with respect to t,
V
is -avec/T.
-- 2. The smaller the reverse bias diode capacitance,
the
higher the resulting Vi and the less time it takes to
measure the same sensor capacitance.
-- 3. The smaller Of can be made,-the higher Vi will be.
The first implication is the choice of
interface
the
sensor
to
To use CMOS logic directly connected
board which is prone to high static voltage
from touch, the circuitry must be protected.
High
voltage
to
bypass
logic
sensor matrix using high logic voltages with
Vec equal to 15 volts.
to the
CMOS
diodes
are
connected
negative
each
row
3-6
APLNDC00026366
f
line(charging source) for this reason.
The second implication is the use of diodes with
reverse
capacitance.
small
The diode IN 4148 was chosen for low .
capacitance, low cost, and
availability. The
reverse
clas
capacitance of this dioòe is specified as 4 pF.
The third implication relates directly to
the
forward
current of the diode since Of = Cf.* Vd = k * Id * Vd, where
Cf is the forward capacitance, Vd is the diode voltage drop,
Id
is
the
diode
forward
current and k is some constant.
Furthermore, since Id = (Vcc - 2*Vd)/R, the Id selected
is
then interrelated with the timing resistor chosen.
Further analysis of the sensor matrix is
there
are
board.
2048
such
Accordingly
the
unit
of
interest:
sensors implemented on the P.C
analysis
is
rather
complicated
oecause the rows and columns are electrically not completely
separated. A small section of the sensor
tion
is
shown
in
matrix
Fig. 3.2 for illustration.
bias capacitance couples the sensors in a
configuraThe reverse
column.
Moreover
there exist capacitances between columns due to the physical
configuration of the sensor plates and wires and due to
parasitic
the
capacitances in the circuit, and these couple the
sensors in a row.
The first of these coupling is seen to be
unavoidable while effort was taken to reduce the second.
A simple
column sensor
array
has
been
analyzed. as
APLNDC00026367
shown
in
here.
The analysis is based on an effort to obtain Vi,
instant
appendix
initial
A.
Only the results will be discussed
voltage
in
the discharge period, r,
the
the
ratio of the sensor capacitance over the surrounding capacitance, and m, the separation parameter in the rows.
The instantaneous discharging voltage Vi for a case
when
a
selected sensor.is touched, is given by
st*a÷0.5*(n-1)-f*b
Vi-
(Vcc-2*Vd)
st+0.S*(n+3)
where a = (Vcc-Vd)/(Vcc-2*Vd), b=Vd/(Vcc-2*Vd), f=Cf/Cr, and
st=Cal\Ct/Cr.
The ratio of the sensor capacitance to the intrinsic capaci-
tance of the surroundings, r, is
st
n+1
.st
2
The separation parameter m
sensors
is the
number
which must be touched, to cause
selecteä, sensor to report as "touched".
equations
for
of
non-selected
a non-touched, but
Appendix
A shows
derivation of this parameter and its evalua-
tion by computer iteration in terms of variables such as t'ne
ratio
of
Cs/Cr
and
Cf/Cr.
When Cs/Cr = 2.5 and Cf/Cr =
12.5, the separation parameter m is about 8, and when
Cs/Cr
3-8
APLNDC00026368
5.ô and Ci/Cr = 12.5 the m is about,25.
The firse result
oplies that if more than 8 sensors are touched in a column,
caen
the result will be a wrong report that all the sensors
in the column have been touched.
that if more
The second result
implies
than 25 sensors are touched in a column, the
result will be a report that all the sensors in
have been touched.
the column
Nevertheless, all of the analysis for .
the single selected sensor model is still
valid with some
complication.
The analysis becomes more complicated when the
ters
for
rows
and
column
are incluòed in the equations.
Since the operational amplifier adds currents from
columns
and
oy
selecteä
consequently the discharging time increases by
l+1n(2)/a, where a = ln(Vi/Vt), when the number
increases
parame-
factor
of
two,
the
of
columns
režerence values
of
expected to be increased by the
factor
In(10/3) = 1.2 correspondingly.
However, an increase in-the
number of rows in a group is not expected
reference
values
because
selected reverse bias diodes
charge stored
the
charge
becomes
1.57
to
stored
smaller
žor a
are
increase
=
the
in ene nonwhereas
the
in the selected forward bias diodes remain
constant during charging period and consequently Vi
becomes
smaller.
Efforts have been made to separate the columns as much
as possible. However there still will be some coupling capa-
3-9
APLNDC00026369
ces between columns
due
to
physical
adjacency;
but
effects are considered to be minimal.
3.3 INTERFACE CIRCUIT DESIGN AND INPLEMENTATION
Interfacing between the sensor matrix and the dedicated
CPU requires three main circuit blocks: row selection registers, column switch selection registers and A/D
converting
circuits. The CPU selects the row or rows of a sensor group,
initiating charging of all the associated sensors.
After
a
charging interval, the CPU discharges the selected column or
columns corresponding to a
group
of
sensor
group
by
connecting
a
discharge resistors whose current is summed via a
high slew rate operational amplifier.
There is tradeožf between the scheme using a.single bit
for
each
row
and one using decoding circuits to implement
binary addressing suited to the.binary
The .bit
per
scanning
row scheme requires 32 bits of register while
binary coding needs 6 bits of register since only
.
patterns
of
algorithm.
sensor
scanning algorithm.
grouping
32 * 2 -1
exit according to the binary
However, the first scheme was chosen
because it is ultimately flexible, that is, it allows one to
i¤plement "all" scanning ¤odes by means
enanges
can
be
implementation of
L
of
software.
Thus
easily made in the case of difficulty with
a
particular
software
algorithm.
The
3-10
APLNDC00026370
oced
prototype uses fout 8 bit registers with a com-
reset signal for row selection.
For the same reasons sufficient column switch selection
agisters
are
provided
pattern through software.
so that one can generate any group
However, to reduce the number
of
chips on the board, four switches are controlled by each bit
resulting in žour simultaneous analog signals
tating
four
counters.
However
and
as a result
latches are needed to control 64 swicches.
necessi-
only 2 8-bit
The four sets of
data are provided to the CPU after each scan. These data are
manipulated by software in.correspondence with the
resolution mode.
selected
This implies the hardware itself acts as
an array of 32 by 16 bits while the software emulates 32
64
bits
of
by
scanning resolution. The scanning algorithm is
explained in chapter 4.
The charges stored in the
through
the
selected
cow(a)
ilow
down
selected switches to the virtual ground of the
fast operational amplifier. All the discharging currents are
correspondingly added to produce a signal from which the
discharging time of all the selected sensors can be found by
comparison with a threshold voltage. The output of the nega-
tive voltage comparator is fed to the enable signal
counter
of
the
and to the data bus as a status bit for the counter
readiness. All the counters are reset when the row selection
registers
are
deselected in order to initiate tae counting
APLNDC00026371
process.
The clock rate (10
correspond
But,
of
MHz)
allows
about
10
counts
to
to the sensor capacitance change due to a touch.
course,
the
capacitance
of
all
the
circuitry
attached to the column line during the discharging period is
much larger than the sensor capacitance. Before scanning the
tablet for a touch, the dedicated CPU scans it completely in
all possible resolution modes
so
obtained
when not touched. The
are stored as references.
values
Touches are identi-
fied by the differences between the reference values and the
values measured during use.
The capacitance change corresponding to
the
touch
by
more than one finger when the resolution is very small, that
is, when the area of the sensors selected is large, is
very
large..
Thus the number of bits in the counter should
be enough to measure the maximum capacitance.
unnecessary
also
However it is
either to have enough number of oita to measure
the entire capacitance
including
tances,
the corresponding "complete" counter
or
to
store
values as references.
bit
the
the
capaci-
It is necessary to have only one more
than the number of bits required
change in
surrounding
capacitance
rather
to count the value of
than
complete
counter
values in order to measure difference of the capacitance due
to touch.
space
Thus only an 8 bit counter was
allowed
for
an
extra
implemented
with
4 bit counter in case that a
3-12
APLNDC00026372
eater number of bits is found to be necessary.
counter
(
eaa'oles
the
measurement
of
a
The 8
7 bit capacitance
caange regardless of the degree of overflow in tae
This
means
127, the difference can be obtained without
For exampler a counter value 4 is larger than £8
if the difference is less than 7f in hexadecimal;
words,
an
ate.
counter.
that if the difference, touched to non-touched,
does not exceed
ambiguity.
bit
in
other
unsigned 8 bit comparison would not be appropri-
Therefore the counter does not need to accommodace the
entire
discharging
time including the time due to the aur-
rounding capacitance, which may require more
Some
manipulation
above.
than
8
bits.
is done in software to utilize the žacts
A complete analysis is given in appendix B.
The remaining circuits are for-shifting CMOS levels
TTL
level
and
for òecoding addresses. Eight addresses are
decoded with a R/W signal. One write address is used
single
to
register
for
a
whose output controls the discharge of all
the senbor matrix at once, the grounding of the ground strip
on
the
board
for
template
recognition
applications
as
described below, and as well as controls three LED outputs.
A metal strip is located on one side of the touch
face
of
the
board.
This
strip is a programmable ground
strip which can be grounded to allow a metal-coated
on .the
scanned.
back
side
sur-
of the template shown in Fig.3.3
pattern
to be
It can be angrounded for normal binary scanning so
3-13
APLNDC00026373
•.et 1 co. til
°2dot pattern
Template
touch Frees
pr ogre mmt ble
ground strip
----· sensor vret
Touch sensitive tablet
"ig. 3.5 Template and touch sensitive tablet.
The template pattern lies on the sensor cre:.
Its metal coating touches the ground strip
which is grounded .to initie te recognition of
the template.
APLNDC00026374
esat the "touch" by tae pattera can be ignored. Otherwise it
increases the time to scan all the poir.ts.on the touch
sur-
face including the unneeded points from che template because
the binary scanning time is
directly
proporcional
to
tÂe
numoer of points on the tablet.
3.4 THE HARDWARE SCANNING SEQUENCE
This section describes the reading
sequence
for
data
from the sensor matrix board.
A block diagram of the
hardware circuit is shown in Fig. 3.4 to aSSist the reaâer.
The sequence is as follows.
-- 1. Reset the row selection registers. That
is,
ground
the inPuts.to the sensor matrix.
¯- 2. Discharge all the sensors directly
to
ground
(out
noc through R) for aoout 2 microseconds.
-- 3. Select the row selection registers with an appropriate bit pattern,
-- 4. Select column switches by turning on the appropriate
bit
pattern
in
the column switch selection registers
about 4 micro-seconds to stabilize the sensor charge.
-- 5. Roset the row selection registers and the une output
counters together to initiate counting of the discha g-
3-14
APLNDC00026375
SENSOR
ROW
SELEC'JIGE
f
REGISSERS
MATRIX
COMMON RESET &
RE0ISTER SELECT SI
COLUMN
SWITCHES
·
¿L...
LS
OUNTE S
COLUW SETCH SELECHON
RJGISTERS
COUNTER SELECT S I:GHAM
2
SENSOR DISCHARGE SIGNAL
ADDRESS
DECODER
DDRESS BUS
'
DATA BUS
CPU
ADDRESS ggg
Fig. 3.4 Block diagram of the hardware.
APLNDC00026376
ing time.
-- 6. Wait until the counters are ready
oy
reading
the
status bits.
-- 7. Read the counters.
The bit patterns in the row selection register
the
column
in
switch selection register represent the row and
column addresses respectively. These, however,
converted
and
to
a convenient
routine.
to
be
form corresponäing to physical
placement which is understandable to
interfacing
have
the
user
or
to
the
This process is described in the next
chapter,
3.5 CONCLUSIONS
In
this
chapter,
tradeoffs
between
software
and
hardware have been discussed while introducing the design of
the sensor board and its interfacing circuits.
A prototype
tablet has been implemented .and tested. There were difficalties but all have been sufmounted.
The detailed results
ož
performance testing are described in the chapter 5.
3-15
APLNDC00026377
for(i=0; i<3; i÷÷)
switen(i) (
case 0: bs(coladr+1,cowadt,1eveltelevelc);
break;
case.1: bs(coladt,cowadr+1,levelr,1evelc)i
break;
case 2: bs(coladr+1,cowadr+1,1evelt,levelc);
break;
default: break;
The oinary scanning algorithm is
in assembler
actually
im'plemented
in a non-recursive way; however the structure
and the algoritna have not been cha¤ged from the representaclon aoove.
This algorithm and the modified linear scanning
algorithm are very sensitive to the values of the thresholds
for each level. Thus detecting very small contact areas over
a large sensor group area is rather difficult.
if
the
threshöld
for
the
top level is high then a small
intensity of touch may not be detected;
low,
then
the
search
whereas
iž it
is
may not be successful. Consequently
this would slow down.the scanning procedure
number
Accordingly
sinco
a
large
of unsuccessful trys at the bottom level ( caused by
low threshold in the higher levels ) delays the scan of
the
actual touch points.
4.6 COMPENSATION FOR LOW RESOLUTION HARDWARE
It may seem that the resolution of the hardware is .too
low
for
use
in
graphics
applications.
However
touch
4-10
APLNDC00026378
incensity and multi-touch sensitivity òan be used to enhance
resolution.
.This is possible because the conter 0ž a touch
can be most accurately estimated by an interpolation utilizing
the
values
of the adjacent sensor intensities.
For a
simple example, consider the estimation of'the center of the
touch by an interpolation method as follows:
SupPose the touched point is (i,j) and its
is
z(irj).
Let
intensity
the dx and dy be the relative position of
the interpolation to the integer position (irj).
dx,
and
value
Then
the
dy can be ottained from the values of the adjacent
intensities as follows.
I(-1,+1) (z(i+k,j+1) -z(i+krj-1)
(-1,+1)I(-1,+1)(=(i+k,j+1))
dy-
(-1,÷l)(z(i+1,j+k)-z(i-1,j+k))
T.(-1,+1) Ji(-1,+l)(z(i+k,j+1))
Thus the estimated center of touch is (i+dx, j+dy).
A simple case is shown in Fig 4.5 where possible inter-
polation
points
are
shown when
1, 2, 3, 4, or 5 bits of
intensity are provided from two adjacent sensors.
ture shows that
The pic-
incerpolation points are not evenly popu-
lated and that tne scheme does not give good resolution even
if
a
fairly
high
number
Therefore it may be good
point
of intensity bits are provided.
idea
to
map
each
interpolation
to another domain which gives eve ly populated points
4-11
APLNDC00026379
.
0.0
liid
.o
1 bit
intensity
2 bits
intensity
3 bits
intensity
4 bits
intensity
5 bito
intensity
Fig. 4.5 Centers of pressure interpolated from two sensors with
the number of available bits for pressure being 1, 2, 3,
4, and 5 from left to right.
Each line represents a possible interpoletion point.
APLNDC00026380
for possible combinations of the intensities from two
cent
sensors.
adja-
However such an interpolacion mapping scheme
has not been implemented due to complications
involved
for
more than two sensors.
However the interpolation should be performed in
of
terms
the physical center of the touch shape. Since the .inten-
sity given by the capacitance measurement
is
dependent
of
tae area of touch on the cover of sensor plate, the accurate
center of a touch is more dependent of the size of the touch
relative to the size of the sensor area as well as the shape
of sensor plate.
For the implementation, however, it uses direct
polation
scheme for a few.cases.
One of interest is inter-
polating 3 by 3 sensors with a touched point in
and
inter-
the
center
the other is interpolation of all points on the tablet.
The later one obviously gives highest resolution but it simply emulates a single touch tablet with a high resolution.
The .software in the.dedicated CPU utilizes the communication with the host computer to accommodate the interpolation scheme in the host computer.
4.7 SEQUENCE OF OPERATIONS
The programs in the .dedicated processor
are
sequenced
4-12
APLNDC00026381
.
REFERENCES
Touch Sensitive Tablet as E·acensible Devicû"
di
W.Buxton,
G.Fedorkow,
L.Sasaki,
and
X.C.Smith,
Computer
Systems
Research
Group,
1983
.:1.2
"A Touc'n-Sensitive InPut Device".,
of
Proceedings
the Fifth International Conference on Com-
Puter Music, North Texas State University, Denton, Texas, November, 1981,
of2.0]
"Why Touch Sensing" by Louise
C.Shaw,
Datama-
tion, August 1980, p138-p141
222.1]
United State Patent
3,798,370
Electrographic .Sensor
for
March
19,1974,
Determini¤9 Planar
Coordinates and 3,911,215 October, 7, 1975,
Discriminating Contact Sensor by George S.
Hurstr Elographics, Incorporated,
22.3)
"New Touch Screen Computer" by George Mitchell,
ComPuters and Electronics, December,1983, p57 p66
R-1
APLNDC00026382
yef2.4]
Touch Screen
19iti2er
Data
Sheet· from
TSD
Display Product Inc•, 1982
(ref2.5] .
A Flexible
Thesis,
Human
Machi e
Interfacer
M.A.Sc.
University of Toronto, 1982 by Nimish
Hetha
(ref2.6J
TASA Model: x-y 3600 and X-y controller, Model:
FR-105 Data Sheet 1980
(ref2.7J
Pressure-Sensitive Conductive Rubber Data Sheet
by JSR PCR 1981
ref2.8J
A circuit diagram drawn by FedockoW
in
March,
1981, University ©2 Toronto
ref3.1]
:ef5.l]
Curing
Static
Electricity"
by
Elliott
S.Kanter, Raðio Electronics, Sept•· 1984
Manipulating Simulated Objects With
Gestures
Real-world
Si¤9 a Force and Position Sensitive
Screen by Margaret R.Mi SkY, ComPuter
Volume 18, Number 3 JulY 1984
ef6.l]
Graphics
Solders and Soldering by Howard H.
McGraW-Hill, 1979, p252 - p257
Hanko,
R-2
APLNDC00026383
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APLNDC00026384
Application Serial No. 11/278,080 filed on 03/30/2006
DOCKET NO: P3764US1
(119-0077US)
APPLICATION
FOR
UNITED STATES Lt-
TITLE:
ERS PATENT
Force Imaging Input Device and System
INVENTORS: Steve Hotelling and Brian Q. Huppi
Date: March 30, 2006
Preoared bv
WONG, CABELLO, LUTSCH, RUTHERFORD & BRucCULERI, L.L.P.
Houston, Texas
(VOICE) 832 i ll 2400
(FACSIMILE)832-446-2424
Austin, Texas
(VolcE) 512-473-2550
(FACSIMILE) 512-473-2555
BEST AVAILABLE COPY
APLNDC00026385
Application Serial No. 11/278,080 filed on 03/30/2006
DOCKET NO: P3764US1
(119-0077US)
FORCE IMAGING INPUT DEVICE AND SYSTEM
Backgroppd
[0001]
The invention relates generally to electronic system input devices and,
more particularly, to force imaging and location-and-force imaging mutual capacitance
systems.
[0002]
Numerous touch sensing devices are available for use in computer
systems, personal digital assistants, mobile phones, game systems, music systems and
the like (Le., electronic systems). Perhaps the best known are resistive-membrane
position sensors which have been used as keyboards and position indicators for a
number of years. Other types of touch sensing devices include resistive tablets, surface
acoustic wave devices, touch sensors based on resistance, capacitance, strain gages,
electromagnetic sensors or pressure sensors, and optical sensors. Pressure sensitive
position sensors have historically offered little benefit for use as a pointing device (as
opposed to a data entry or writing device) because the pressure needed to make them
operate inherently creates stiction between the finger and the sensor surface. Such
stiction has, in large measure, prevented such devices from becoming popular.
[0003]
Owing to the growing popularity of portable .devices and the attendant
need to integrate all input functions into a single form factor, the touch pad is now one
of the most popular and widely used types of input device. Operationally, touch pads
may be categorized as either "resistive" or "capacitive." In resistive touch pads, the pad
is coated with a thin metallic electrically conductive layer and resistive layer. When the
-1-
APLNDC00026386
Application Serial No. 11/278,080 filed on 03/30/2006
DOCKET NO: P3764US1
(119-0077US)
pad is touched, the conductive layers come into contact through the resistive layer
causing a change in resistance (typically measured as a change in current) that is used
to identify where on the pad the touch event occurred. In capacitive touch pads, a first
set of conductive traces run in a first direction and are insulated by a dielectric insulator
from a second set of conductive traces running in a second direction (generally
orthogonal to the first direction). The grid formed by the overlapping conductive traces
create an array of capacitors that can store electrical charge. When an object is brought
into proximity or contact with the touch pad, the capacitance of the capacitors at that
location change. This change can be used to identify the location of the touch event.
[0004]
One drawback to using touch pads as input devices is that they do not
generally provide pressure or force information. Force information may be used to
obtain a more robust indication of how a user is manipulating a device. That is, force
information may be used as another input dimension for purposes of providing
command and control signals to an associated electronic device. Thus, it would be
beneficial to provide a force measurement system as part of a touch pad input device.
Summarv
[0005]
In one embodiment the invention provides a force sensitive touch pad
that includes first and second sets of conductive traces separated by a spring
membrane. When a force is applied, the spring membrane deforms moving the two sets
of traces closer together. The resulting change in mutual capacitance is used to
generate an image indicative of the location (relative to the surface of the touch pad)
-2-
APLNDC00026387
Application Serial No. 11/278,080 filed on 03/30/2006
DOCKEY NO: P3764US1
(119-007705)
and strength or intensity of an applied force. In another embodiment, the invention
provides a combined location and force sensitive touch pad that includes two sets of
drive traces, one set of sense traces and a spring membrane. In operation, one of the
drive traces is used in combination with the set of sense traces to generate an image of
where one or more objects touch the touch pad. The second set of drive traces is used
in combination with the sense traces and spring membrane to generate an image of the
applied force's strength or intensity and its location relative to the touch pad's surface.
Force touch pads and location and force touch pads in accordance with the invention
may be incorporated in a variety of electronic devices to facilitate recognition of an
increased array of user manipulation.
[0006]
In yet another embodiment, the described force sensing architectures
may be used to implement a display capable of detecting the amount of force a user
applies to a display (e.g., a liquid crystal display unit). Display units in accordance with
this embodiment of the invention may be used to facilitate recognition of an increased
array of user input.
Brief pewr!Rtion of the Drawings
[0007]
.
Figure 1 shows, in exploded perspective view, a force detector in
accordance with one embodiment of the invention.
[0008]
Figures 2A and 28 show, in cross-section, an unloaded (A) and loaded (B)
force detector in accordance with FIG. 1.
-3-
APLNDC00026388
Application Serial No. 11/278,080 filed on 03/30/2006
DOCKET NO: P3764US1
(119-007705)
[0009]
Figure 3 shows, in block diagram form, a force detection system in
accordance with one embodiment of the invention.
[0010]
Figure 4 shows, in block diagram form, a more detailed view of the force
detection system in accordance with FIG. 3.
[0011]
Figure 5 shows, in cross-section, a location and force detection device in
accordance with one embodiment of the invention.
[0012]
Figure 6 shows, in cross section, a location and force detection device in
accordance with another embodiment of the invention.
[0013]
Figure 7 shows an exploded view of drive and sense traces in accordance
with FIG. 6.
[0014]
Figures 8A-8C show various views of a location and force detection device
in accordance with still another embodiment of the invention.
[0015]
Figures 9A-9C show various views of a location and force detection device
in accordance with yet another embodiment of the invention.
[0016]
Figures 10A and 10B show, in cross section, a location and force detection
device in accordance with another embodiment of the invention.
[0017]
Figures 11A-11C show various views of a spring membrane in accordance
with another embodiment of the invention.
[0018]
Figures 12A and 128 show, in block diagram form, a force detection
display system in accordance with one embodiment of the invention.
.4.
APLNDC00026389
Application Serial No. 11/278,080 filed on 03/30/2006
DOCKET NO: P3764US1
(119-0077US)
Detailed Descriotion
[0019]
The following description is presented to enable any person skilled in the
art to make and use the invention as claimed and is provided in the context of the
particular examples discussed below (touch pad input devices for personal computer
systems), variations of which will be readily apparent to those skilled in the art.
Accordingly, the claims appended hereto are not intended to be limited by the disclosed
embodiments, but are to be accorded their widest scope consistent with the principles
and features disclosed herein. By way of example only, force imaging systems in
accordance with the invention are equally applicable to electronic devices other than
personal computer systems such as computer workstations, mobile phones, hand-held
digital assistants and digital control panels for various machinery and systems
(mechanical, electrical and electronic).
[0020]
Referring to FIG. 1, the general concept of a force detector in accordance
with the invention is illustrated as it may be embodied in touch pad device 100. As
illustrated, force detector 100 comprises cosmetic layer 105, sense layer 110
(including conductive paths 115 and electrical connector 120), dielectric spring layer
125 (including spatially offset raised structures 130), drive layer 135 (including
conductive paths 140 and electrical connector 145) and base or support 150. (It will
be understood by those of ordinary skill in the art that connectors 120 and 145
provide unique connections for each conductive trace on layers 110 and 135
respectively.)
-5-
APLNDC00026390
Application Serial No. 11/278,080 filed on 03/30/2006
DOCKET NO: P3764US1
(119-0077US)
[0021]
Cosmetic layer 105 acts to protect other elements of the system from
ambient conditions (e.g., dust and moisture) and, further, provides a surface through
which users interact with detector 100. Conductive paths 115 on sense layer 110 are
arranged so that they overlap conductive paths 140 on drive layer 135, thereby
forming capacitors whose plates (conductive paths 115 and 140) are separated by
sense layer substrate 110, dielectric spring layer 125 and raised structures 130.
Dielectric spring layer 125 and raised structures 130 together create a mechanism by
which sense layer 110's conductive paths 115 are brought into closer proximity to
drive layer 135's conductive paths 140 when a force is applied to cosmetic layer 105.
It will be recognized that this change in separation causes the mutual capacitance
between sense layer and drive layer conductive paths (115 and 140) to change
(increase) - a change indicative of the amount, intensity or strength of the force
applied to cosmetic layer 105. Base or support layer 150 provides structural integrity
for force detector 100.
[0022]
Referring to FIG. 2A, a cross-sectional view of force detector 100 is
shown in its unloaded or "no force" state. In this state, the mutual capacitance between
sense layer 110 and drive layer 135 conductive paths (115 and 140) results in a
steady-state or quiescent capacitance signal (as measured via connectors 120 and 145
in FIG. 1). Referring to FIG. 2B, when external force 200 is applied to cosmetic layer
105, dielectric spring layer 125 is deformed so that sense layer 110 moves closer to
drive layer 135. This, in tum, results in a change (increase) in the mutual capacitance
between the sense and drive layers - a change that is approximately monotonically
-6-
APLNDC00026391
Application Serial No. 11/278,080 filed on 03/30/2006
DOCKET NO: P3764US1
(119-007705)
related to the distance between the two and, therefore, to the intensity or strength of
applied force 200. More specifically, during operation traces 140 (on drive layer 135)
are electrically stimulated one at a time and the mutual capacitance associated with the
stimulated trace and each of traces 115 (on sense layer 110) is measured. In this way
an image of the strength or intensity of force 200 applied to cosmetic layer 105 is
obtained. As previously noted, this change in mutual capacitance may be determined
though appropriate circuitry.
[0023]
Referring to FIG. 3, a block diagram of force imaging system 300 utilizing
force detector touch pad 100 is shown. As illustrated, force imaging system 300
comprises force detector 100 coupled to touch pad controller 305 through connectors
120 (for sense signals 310) and 145 (for drive signals 315). Touch pad controller
305, in turn, periodically sends signals to host processor 320 that represent the
(spatial) distribution of force applied to detector 100. Host processor 320 may
interpret the force information to perform specified command and control actions (e.g.,
select an object displayed on display unit 325).
[0024]
Referring to FIG. 4, during operation drive circuit 400 in touch pad
controller 305 sends ("drives") a current through drive signals 315 and connector 145
to each of the plurality of drive layer conductive paths 140 (see FIG. 1) in turn.
Because of capacitive coupling, some of this current is carried through to each of the
plurality of sense layer conductive paths 115 (see FIG. 1). Sensing circuits 405 (e.g.,
charge amplifiers) detect the analog signal from sense signals 310 (via connector 120)
and send them to analysis circuit 410. One function of analysis circuit 410 is to convert
-7-
APLNDC00026392
Application Serial No. 11/278,080 filed on 03/30/2006
DOCKET NO: P3764US1
(119-0077US)
the detected analog capacitance values to digital form (e.g., through A-to-D
converters). Another function of analysis circuit is to queue up a plurality of digitized
capacitance values for transmission to host processor 320 (see FIG. 3). Yet another
function of analysis circuit is to control drive circuit 400 and, perhaps, to dynamically
adjust operation of sense circuits 405 (e.g., such as by changing the threshold value at
which a "change" in capacitance is detected). One embodiment of controller 305
suitable for use in the present invention is described in US patent application entitled
"Multipoint Touch Screen Controller," serial number 10/999,999 by Steve Hotelling,
Christoph Krah and Brian Huppi, filed 15 March 2006 and which is hereby incorporated
in its entirety.
[0025]
In another embodiment, a force detector in accordance with the invention
is combined with a capacitive location detector to create a touch pad device that
provides both location and force detection. Referring to FIG. 5, combined location and
force detector 500 comprises cosmetic layer 505, circuit board or substrate 510
(including a first plurality of conductive drive paths 515 on a first surface and a plurality
of sense paths 520 on a second surface), dielectric spring layer 525 (including
alternating, or spatially offset, raised structures 530), drive layer 535 (including a
second plurality of conductive drive paths) and base or support 540. In one
embodiment, conductive drive paths 515 and 535 are laid down on substrate 510 and
support 540 respectively to form rows and sense conductive paths are laid down on
substrate 510 to form columns. Accordingly, during operation first drive paths 515 are
driven (one at a time) during a first time period and, during this same time, sense paths
-8-
APLNDC00026393
Application Serial No. 11/278,080 filed on 03/30/2006
DOCKET NO: P3764US1
(119-0077US)
520 are interrogated to obtain an image representing the location of one or more
cosmetic layer touches. Similarly, second drive paths 535 are driven (one at a time)
during a second time period and, during this same time, sense paths 520 are again
interrogated to obtain an image representing, this time, the strength or intensity of the
force applied to cosmetic layer 505. The operation of computer input devices (e.g.,
touch pads) for touch detection based on the principle of mutual capacitance is
described in US patent application entitled "Multipoint Touchscreen" by Steve Hotelling,
Joshua A. Strickon and Brian Q. Huppi, serial number 10/840,862 and which is hereby
incorporated in its entirety.
[0026]
Referring to FIG. 6, location and force touch pad 600 in accordance with
another embodiment of the invention is shown in cross section. In this embodiment,
cosmetic layer 605 comprises a polyester or polycarbonate film. Layer 610 comprises
an acrylic-based pressure sensitive or ultraviolet light cured adhesive. Layer 615
functions as a two-sided circuit board that has a first plurality of conductive drive traces
620 oriented in a first direction on a "top" surface (Le., toward cosmetic layer 605)
and a plurality of conductive sense traces 625 oriented in a second direction on a
"bottom" surface. In one embodiment, circuit substrate layer 615 comprises a low
temperature plastic or thermoplastic resin such as polyethylene terephthalate ("PET").
In this embodiment, drive traces 620 and sense traces 625 may comprise printed
silver ink. In another embodiment, circuit substrate layer 615 comprises a flexible
circuit board, or fiberglass or glass and drive and sense traces (620 and 625) comprise
Indium tin oxide ("ITO") or copper. Layer 630, in one embodiment, comprises a
APLNDC00026394
Application Serial No. 11/278,080 filed on 03/30/2006
DOCKET NO: P3764US1
(119-OO77US)
layered combination consisting of adhesive-PET-adhesive, where the adhesive
components are as described above with respect to layer 610. Layers 635, 640 and
645 comprise PET of varying thicknesses. As shown, the "bottom" surface of layer 640
has affixed thereon a second plurality of conductive drive traces 650 oriented in
substantially the same orientation as first conductive drive traces 620. Raised and
spatially offset support structures 655 and layer 660 also comprise a layered
combination consisting of adhesive-PET-adhesive (similar to layer 630, see above).
Layers 605-660 are affixed to and supported by base or stiffener plate 665. For
example, in a portable or notebook computer system, base 665 could be formed from a
rigid material such as a metal stamping that is part of the computer system's frame.
Similarly, base 665 could be the internal framing within a personal digital assist and or
mobile telephone. Table 1 identifies the thickness for each of layers 600-660 for one
embodiment of touch pad 600.
Table 1: Dimensions for Illustrative Touch Pad 600
Layer
Material
Thickness (mm)
605
Polyester, polycarbonate film, glass or ceramic
0.3
610
Pressure sensitive adhesive ("PSA") or ultraviolet
("UV") light cured adhesive
0.05
615
PET
620
Silver ink, copper, Indium tin oxide
0.006
625
Silver ink, copper, Indium tin oxide
0.006
630
Layered PSA-PET-PET
0.075 ± 0.02
0.03 ± 0.01
- 10 -
APLNDC00026395
Application Serial No. 11/278,080 filed on 03/30/2006
DOCKET NO: P3764US1
(119-0077US)
Table 1: Dimensions for Illustrative Touch Pad 600
Layer
Material
Thickness (mm)
635
PET
0.075 ± 0.02
640
PET
0.1 ± 0.02
645
PET
0.125 ± 0.02
650
Silver ink, copper, Indium tin oxide
Layered:
0.006
0.025 ± 0.01
PET
0.1 ± 0.02
PSA
655
PSA
0.025 ± 0.01
Active touch pad surface: 271 mm × 69 mm
No of drive traces (620 and 650): 13
Number of sense traces (625): 54
Pixel separation: 5 mm
[0027]
In operation touch pad 600 measures the change (e.g., decrease) in
capacitance due to cosmetic layer 605 being touched at one or more locations through
the mutual capacitance between drive traces 620 and sense traces 625. In a manner
as described above, touch pad 600 also measures forces applied to cosmetic layer as
sense traces 625 and drive traces 650 are brought into closer proximity through the
measured change (e.g., increase) in mutual capacitance between them. In this
embodiment, raised structures 655 are used on both sides of the second layer of drive
traces (650) to provide additional movement detection capability.
[0028]
During measurement operations, each of drive traces 620 are stimulated
in turn and, simultaneously, the change in mutual capacitance between drive traces
- 11 -
APLNDC00026396
Application Serial No. 11/278,080 filed on 03/30/2006
DOCKET NO: P3764US1
(119-0077US)
620 and sense traces 625 is measured. Once each of drive traces 620 have been
stimulated (and the corresponding change in capacitance measured via sense traces
625), each of drive traces 650 are driven in turn and sense traces 625 are used to
determine the change in mutual capacitance related to force (that is, the mutual
capacitance change between traces 625 and 650 due to an applied force). In this
manner, images of both the "touch" input and "force" input to cosmetic layer 605 can
be obtained.
[0029]
One of ordinary skill in the art will recognize that the above-described
"scanning" sequence is not required. For example, drive traces 620 and 650 could be
stimulated in overlapping fashion such that a first trace in drive traces 620 is
stimulated, followed by a first trace in drive traces 650, followed by a second trace in
drive traces 620 and so on. Alternatively, groups of traces in drive traces 620 could be
stimulated first, followed by a group of traces in drive traces 650, and so on.
[0030]
In one embodiment drive traces 620 (associated with touch location
measurement operations) use a different geometry from drive traces 650 (associated
with force measurement operations) and sense traces 625 (used during both location
and force measurement operations). Referring to FIG. 7, it can be seen that drive
traces 620 utilize conductive traces that employ internal floating plate structures 700
and, in addition, are physically larger than either the conductive traces used in sense
625 and drive traces 650 (both of which, in the illustrated embodiment, have the same
physical size/structure). It has been found that this configuration provides increased
- 12 -
APLNDC00026397
Application Serial No. 11/278,080 filed on 03/30/2006
DOCKET NO: P3764US1
(119-0077US)
sensitivity for determining where one or more objects (e.g., a finger of stylus) touch, or
come into close proximity to, cosmetic surface 605.
[0031]
Referring to FIG. 8A, in another embodiment of a combined touch and
force sensitive touch pad in accordance.with the invention (touch pad 800), raised
structures 655 may be replaced by beads or polymer dots 805 (also referred to as
rubber or elastomer dots). In this embodiment, beads 805 operate in a manner similar
to that of raised structures 655 (see FIG. 6). As shown, beads 805 rest on a thin
adhesive layer 810 and are sized to keep layers 630 and 640 at a specified distance
when no applied force is present. One illustrative layout and spacing of beads 805 is
shown in FIGS. 8B (lop view) and 8C (cross-section). Table 2 identifies the approximate
dimensions for each component of touch pad 800 that is different from prior illustrated
touch pad 600.
Layer
Table 2: Dimensions for Illustrative Touch Pad 800
Material
Thickness (mm)
805
Rubber or polymer (e.g., elastomer)
810
Pressure sensitive adhesive ("PSA") or ultraviolet
("UV") light cured adhesive
0.015
a
Column bead separation
1.0
b
Row bead separation
5.0
c
Bead offset
2.5 ± 0.15
d
Bead height
0.15
Active touch pad surface: 271 mm × 69 mm
- 13 -
APLNDC00026398
Application Serial No. 11/278,080 filed on 03/30/2006
DOCKET NO: P3764US1
(119-0077US)
Table 2: Dimensions for Illustrative Touch Pad 800
Layer
Material
Thickness (mm)
No of drive traces (620 and 650): 13
Number of sense traces (625): 54
Pixel separation: 5 mm
[0032]
Referring to FIG. 9A, in yet another embodiment of a combined touch and
force sensitive touch pad in accordance with the invention (touch pad 900), a single
layer of deformable beads or elastomer dots 905 are used. In touch pad 900, thin
adhesive layers 910 are used to mechanically couple the beads to the rest of the touch
pad structure and the structure itself to base 665. One illustrative layout and spacing of
deformable beads 905 is shown in FIGS. 9B (lop view) and 9C (cross-section). Table 3
identifies the approximate dimensions for each component of touch pad 900 that is
different from prior illustrated touch pad 600.
Table 3: Dimensions for Illustrative Touch Pad 900
Layer
Material
905
Rubber or polymer (e.g., elastomer)
910
Pressure sensitive adhesive ("PSA") or ultraviolet
Thickness (mm)
0.015
("UV") light cured adhesive
a
Column bead separation
1.0
b
Row bead separation
1.0
c
Bead offset
0.5
d
Bead width
0.5
- 14 -
APLNDC00026399
Application Serial No. 11/278,080 filed on 03/30/2006
DOCKET NO: P3764US1
(119-007705)
Table 3: Dimensions for Illustrative Touch Pad 900
Layer ¡
e
Material
' Bead height
Thickness (mm)
0.15
Active touch pad surface: 271 mm × 69 mm
No of drive traces (620 and 650): 13
Number of sense traces (625): 54
Pixel separation: 5 mm
[0033]
Referring to FIG. 10A, in another embodiment of a combined touch and
force sensitive touch pad in accordance with the invention (touch pad 1000), spring
membrane 1005 is used instead of raised structures (e.g., 530 and 655) or
deformable beads (e.g., 805 and 905). In touch pad 1000, thin adhesive layers 1010
are used to mechanically couple PET spring 1005 to layers 635 and 640 as well as to
mechanically couple layer 645 to base 665. Referring to FIG. 10B, in one embodiment
spring membrane comprises a single rippled sheet of PET whose run-to-rise ratio (i.e.,
a/b) is typically in the range of approximately 10:1 to 50:1. One of ordinary skill in the
art will recognize that the exact value used in any given embodiment may change due
to a variety of factors such as, for example, the physical size of the touch pad surface,
the amount of weight specified for full deflection (e.g., 200 grams) and the desired
sense of "stiffness" presented to the user. Table 4 identifies the approximate
dimensions for each component of touch pad 1000 that is different from prior
illustrated touch pad 600.
- 15 -
APLNDC00026400
Application Serial No. 11/278,080 filed on 03/30/2006
DOCKET NO: P3764US1
(119-0077US)
Table 4: Dimensions for Illustrative Touch Pad 1000
Layer
Material
Thickness(mm)
1005
PET
0.75
1010
Pressure sensitive adhesive ("PSA") or ultraviolet
("UV") light cured adhesive
0.025
a/b
Spring run-to-rise ratio
10:1 a 50:1
Active touch pad surface: 271 mm × 69 mm
No of drive traces (620 and 650): 13
Number of sense traces (625): 54
Pixel separation: 5 mm
[0034]
Referring to FIG. 11A, in another embodiment rippled spring membrane
1005 may be replaced by dimpled spring membrane 1105. In this implementation,
spring membrane 1105 is a single sheet of deformable material (e.g., PET) that has
dimples formed in it by, for example, thermal or vacuum forming techniques. Figures
11B and 11C show top views of two possible dimple arrangements. Two illustrative
layouts (lop view) for dimpled membrane 1105 are shown in FIGS. 11B and 11C. As
used in FIGS. 11A-11C, the "+" symbol represents a raised region and a "-" symbol
represents a depressed region. Table 5 identifies the approximate dimensions "a"
through "e" specified in FIG. 11A.
- 16 -
APLNDC00026401
Application Serial No. 11/278,080 filed on 03/30/2006
DOCKET NO: P3764US1
(119-0077US)
Table 5: Dimensions for Illustrative Spring Membrane 1100
Layer
Material
Thickness(mm)
1105
a
0.075
1.0
b
Dimple width
1.25
c
Dimple separation
2.5
d
[0035]
PET
Dimple top length
Dimple rise and fall length
0.075
Various changes in the materials, components and circuit elements are
possible without departing from the scope of the following claims. For example, drive
traces and sense traces in accordance with FIGS. 1-10 have been described as being
orthogonal. The manner in which drive traces and cut across or intersect with sense
traces, however, generally depends on the coordinate system used. In a Cartesian
coordinate system, for example, sense traces are orthogonal to the driving traces
thereby forming nodes with distinct x and y coordinates. Alternatively, in a polar
coordinate system, sense traces may be concentric circles while drive traces may be
radially extending lines (or vice versa).
[0036]
In addition, in the embodiments of FIGS. 1 and 2, drive layer 135 and
drive traces 140 (and, therefore, connector 145) may be incorporated within and on
spring membrane 125. That is, drive traces 140 could be laid down or etched on a
surface of flexible membrane 125. Similarly, drive traces 535 could be incorporated into
and as part of flexible membrane 525 (see FIG. 5).
- 17 -
APLNDC00026402
Application Serial No. 11/278,080 filed on 03/30/2006
DOCKET NO: P3764US1
(119-0077US)
[0037]
One of ordinary skill in the art will also recognize that beads in accordance
with FIGS. 8 and 9 (see FIGS. 8 and 9) could also be used in place of raised structures
130, 530 and 655 (see FIGS. 1, 2A, 2B, 5 and 6). Similarly, spring mechanisms 1005
(see FIG. 10) and 1105 (see FIG. 11) could be used in place of beads 805 (see FIG.
8), deformable beads 805 and 905 (see FIGS. 8 and 9) or raised structures 130, 530
and 655 (see FIGS. 1, 5 and 6).
[0038]
Referring to FIG. 12A, in another embodiment force detection in
accordance with the invention may be incorporated within a display unit rather than a
touchpad. For example, system 1200 includes processor 1205, standard input-output
("I/O") devices 1210 (e.g., keyboard, mouse, touch pad, joy stick and voice input) and
display 1215 incorporating force detection capability in accordance with the invention.
Referring to FIG. 12B, in this embodiment, display 1215 includes display element
1220, display element electronics 1225, force element 1230 and force electronics
1235. In this manner, user 1240 views display element 1220 of display 1200 through
force element 1230. By way of example, display element 1220 and electronics 125
may comprise a conventional liquid crystal display ("LCD") display. Force element 1230
may comprise a force-only sensor (e.g., similar to the embodiments of FIGS. 1 and 2)
or a force and location sensor (e.g., similar to the embodiments of FIGS. 5-11). Force
electronics 1235 may compose processing circuitry as described in FIG. 4. That is,
force electronics 1235 is capable of driving and sensing mutual capacitance signals as
described in connection with a touch pad in accordance with the invention.
- 18 -
APLNDC00026403
Application Serial No. 11/278,080 filed on 03/30/2006
DOCKET NO: P3764US1
(119-0077US)
[0039]
It will be recognized by those of ordinary skill in the art that use of the
described force detection technology should, when applied to display 1215, utilize
transparent or substantially transparent drive and sense traces such as that provided by
ITO (Le., rather than copper which is opaque). Similarly, the gap between the first layer
of traces (e.g., drive traces) and a second layer of traces (e.g., sense traces) used to
detect an applied force (see discussion above) should be transparent or substantially
transparent. For example, compressible transparent spacers could be used to embody
offset raised structures 130, support structures 655, deformable beads 805, 905 or
spring membranes 1005, 1105.
-19 -
APLNDC00026404
Application Serial No. 11/278,080 filed on 03/30/2006
DOCKET NO: P3764US1
(119-0077US)
Claims
1.
A force imaging touch pad, comprising:
a first layer having a first plurality of conductive traces oriented in a first
direction on a first surface thereof;
a second layer having a second plurality of conductive traces oriented in a
second direction on a first surface thereof; and
a deformable dielectric membrane juxtaposed between the first and second
layers,
wherein the first and second plurality of conductive traces are adapted to create
a capacitance image when a force is applied to the first layer, the capacitance image
indicative of an intensity of the applied force.
2.
The force imaging touch pad of claim 1, wherein the first plurality of conductive
traces and the second plurality of conductive traces are substantially orthogonal.
- 20 -
APLNDC00026405
Application Serial No. 11/278,080 filed on 03/30/2006
DOCKET NO: P3764US1
(119-0077US)
3.
The force imaging touch pad of claim 1, wherein the deformable dielectric
membrane comprises:
a substantially flat membrane having a first surface oriented toward the first
layer and a second surface oriented toward the second layer;
a first plurality of raised structures coupled to the first surface of the
substantially flat membrane; and
a second plurality of raised structures coupled to the second surface of the
substantially flat membrane, wherein the second plurality of raised structures are
substantially offset from the first plurality of raised structures.
4.
The force imaging touch pad of claim 1, wherein the deformable dielectric
membrane comprises:
a substantially flat membrane; and
a plurality of deformable beads affixed to one surface of the substantially flat
membrane, wherein the deformable beads are adapted to compress when a force is
applied to the first layer toward the second layer.
5.
The force imaging touch pad of claim 1, wherein the deformable dielectric
membrane comprises one or more thermoplastic springs.
6.
The force imaging touch pad of claim 1, wherein the deformable dielectric
membrane comprises a dimpled deformable membrane.
- 21 -
APLNDC00026406
Application Serial No. 11/278,080 filed on 03/30/2006
Dume i NO: P3764US1
(119-0077US)
7.
The force imaging touch pad of claim 5, wherein the thermoplastic springs
comprise Polyethylene terephthalate.
8.
The force imaging touch pad of claim 1, further comprising a mutual capacitance
measurement circuit electrically coupled to the first and second plurality of conductive
traces.
- 22 -
APLNDC00026407
Application Serial No. 11/278,080 filed on 03/30/2006
DOCKET NO: P3764US1
(119-0077US)
9.
A force and location imaging touch pad, comprising:
a first layer having a first plurality of conductive traces oriented in a first
direction on a first surface thereof and a second plurality of conductive traces oriented
in a second direction on a second surface thereof;
a second layer having a third plurality of conductive traces oriented in
substantially the first direction;
a base layer;
a first deformable membrane juxtaposed between the first and second layers;
and
a second deformable membrane juxtaposed between the second layer and the
base layer,
wherein the first and second plurality of conductive traces are adapted to create
a first capacitance image when one or more objects come into close proximity to the
first surface, the first capacitance image indicative of where the one or more objects are
located relative to the first surface,
wherein the second and third plurality of conductive traces are adapted to create
a second capacitance image when a force is applied to the first layer, the second
capacitance image indicative of an intensity of the applied force.
10.
The force and location imaging touch pad of claim 9, wherein the first layer
comprises a flexible circuit board.
- 23 -
APLNDC00026408
Application Serial No. 11/278,080 filed on 03/30/2006
DOCKET NO: P3764US1
(119-0077US)
11.
The force and location imaging touch pad of claim 9, wherein the first layer
comprises one or more layers of thermoplastic resin.
12.
The force and location imaging touch pad of claim 9, wherein the first plurality of
conductive traces and the second plurality of conductive traces are substantially
orthogonal.
13.
The force and location imaging touch pad of claim 9, wherein the second layer
comprises a flexible circuit board.
14.
The force and location imaging touch pad of claim 9, wherein the second layer
comprises one or more layers of thermoplastic resin.
15.
The force and location imaging touch pad of claim 9, wherein the first
deformable membrane comprises a first plurality of raised structures, the second
deformable membrane comprises a second plurality of raised structures and the first
and second raised structures are substantially spatially offset from one another.
16.
The force and location imaging touch pad of claim 15, wherein the first and
second plurality of raised structures comprise thermoplastic resin.
- 24 -
APLNDC00026409
Application Serial No. 11/278,080 filed on 03/30/2006
DOCKET NO: P3764US1
(119-0077US)
17.
The force and location imaging touch pad of claim 9, wherein the first
deformable membrane comprises a first plurality deformable beads, the second
deformable membrane comprises a second plurality of deformable beads and the first
and second plurality of deformable beads are substantially spatially offset from one
another.
18.
The force and location imaging touch pad of claim 17, wherein the deformable
beads comprise elastomer beads.
19.
The force and location imaging touch pad of claim 9, wherein each of the first
and second plurality of raised structures comprise one or more thermoplastic springs.
20.
The force and location imaging touch pad of claim 19, wherein the thermoplastic
springs comprise Polyethylene terephthalate.
21.
The force and location imaging touch pad of claim 9, further comprising a mutual
capacitance measurement circuit electrically coupled to the first, second and third
plurality of conductive traces.
- 25 -
APLNDC00026410
Application Serial No. 11/278,080 filed on 03/30/2006
DOCKET NO: P3764US1
(119-0077US)
22.
A force and location imaging touch pad, comprising:
a first surface having a first plurality of conductive traces oriented in a first
direction;
a second surface having a second plurality of conductive traces oriented in a
second direction, the first and second surfaces juxtaposed to and electrically isolated
from one another;
a third surface having a third plurality of conductive traces oriented in
substantially the first direction; and
a deformable membrane between the second and third layers,
wherein the first and second plurality of conductive traces are adapted to create
a first capacitance image when one or more objects come into close proximity to the
first surface, the first capacitance image indicative of where the one or more objects are
located relative to the first surface,
wherein the second and third plurality of conductive traces are adapted to create
a second capacitance image when a force is applied to the first surface, the second
capacitance image indicative of an intensity of the applied force.
23.
The force and location imaging touch pad of claim 22, wherein the first and
second surfaces are surfaces of a common layer.
24.
The force and location imaging touch pad of claim 23, wherein the common layer
comprises a flexible circuit board.
- 26 -
APLNDC00026411
Application Serial No. 11/278,080 filed on 03/30/2006
DOCKET NO: P3764US1
(119-0077US)
25.
The force and location imaging touch pad of claim 23, wherein the common layer
comprises one or more layers of thermoplastic resin.
26.
The force and location imaging touch pad of claim 22, wherein the first plurality
of conductive traces and the second plurality of conductive traces are substantially
orthogonal.
27.
The force and location imaging touch pad of claim 22, wherein the third surface
comprises thermoplastic resin.
28.
The force and location imaging touch pad of claim 22, wherein the deformable
membrane comprises:
a substantially flat membrane having a first surface oriented toward the first
plurality of conductive traces and a second surface oriented toward the third plurality of
conductive traces;
a first plurality of raised structures coupled to the first surface of the
substantially flat membrane; and
a second plurality of raised structures coupled to the second surface of the
substantially flat membrane, wherein the second plurality of raised structures are
substantially spatially offset from the first plurality of raised structures.
- 27 -
APLNDC00026412
Application Serial No. 11/278,080 filed on 03/30/2006
DOCKET NO: P3764US1
(119-0077US)
29.
The force and location imaging touch pad of claim 22, wherein the deformable
membrane comprises:
a substantially flat membrane; and
a plurality of deformable beads affixed to one surface of the substantially flat
membrane, wherein the deformable beads are adapted to compress when a force is
applied to the first layer toward the second layer.
30.
The force and location imaging touch pad of claim 22, wherein the deformable
membrane comprises a dimpled deformable membrane.
31.
The force and location imaging touch pad of claim 29, wherein the deformable
beads comprise polymer.
32.
The force and location imaging touch pad of claim 22, wherein the deformable
membrane comprises one or more thermoplastic springs.
33.
The force and location imaging touch pad of claim 32, wherein the thermoplastic
springs comprise Polyethylene terephthalate.
34.
The force and location imaging touch pad of claim 22, further comprising a
mutual capacitance measurement circuit electrically coupled to the first, second and
third plurality of conductive traces.
- 28 -
APLNDC00026413
Application Serial No. 11/278,080 filed on 03/30/2006
DOCKET NO: P3764US1
(119-0077US)
35.
An electronic device, comprising:
a pm-sing unit;
a display unit operatively coupled to the processing unit;
a mutual capacitance measurement circuit operatively coupled to the processing
unit; and
a force and location imaging touch pad in accordance with one of claims 9 and
22 and operatively coupled to the mutual capacitance measurement circuit.
36.
The electronic device of claim 35, wherein the electronic device comprises a
computer system.
37.
The electronic device of claim 35, wherein the electronic device comprises a
mobile telephone.
38.
The electronic device of claim 35, wherein the electronic device comprises a
personal digital assistant.
- 29 -
APLNDC00026414
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