Elan Microelectronics Corporation v. Apple, Inc.

Filing 377

EXHIBITS 2-8 to the Declaration of Dr. Ravin Balakrishnan In Support of Apple Inc.'s Motion for Summary Judgment of Noninfringement filed byApple, Inc.. (Attachments: # 1 Exhibit 3, # 2 Exhibit 4, # 3 Exhibit 5, # 4 Exhibit 6, # 5 Exhibit 7, # 6 Exhibit 8)(Greenblatt, Nathan) (Filed on 8/4/2011)

EXHIBIT 3

United States Patent

[11]

[19]

Greanias et al.
[54]

[45]

COMBINED FINGER TOUCH AND STYLUS
DETECTION SYSTEM FOR USE ON THE
VIEWING SURFACE OF A VISUAL DISPLAY
DEVICE

[75]

Inventors: Evon C. Greanias, Chevy Chase,
Md.; C. Richard Guarnieri, Somers,
N.Y.; John J. Seeland, Jr., Oakland
Park, Fla.; Guy F. Verrier, Reston,
Va.; Robert L. Donaldson, Annapolis,
Md.

[73]

Assignee:

[21]

Appl. No.: 878,949

[22]

Filed:

[51]
[52]
[58]

Int. Cl.4
G08C 21/00
U.S. Cl•....................................... 178/19; 340/706
Field of Search
178/18, 19, 20;
340/706, 709; 324/207

[56]

International Business Machines
Corporation, Armonk, N.Y.
Jun. 26, 1986

References Cited
U.S. PATENT DOCUMENTS
3,696,409
3,757,322
3,992,597
3,999,012
4,009,338
4,103,252
4,398,181

10/1972
9/1973
11/1976
12/1976
2/1977
7/1978
8/1983

Braaten
Barkan et al.
Hannula
Dym
Lowy et al.
Bobick
Yamamoto

340/365
340/365 C
200/61.39
178/18
178/18
331/48
340/365 S

Patent Number:
Date of Patent:

4,582,955

4/1986 Blesser

178/19

[57]

ABSTRACT

A combined finger touch and stylus detection system is
disclosed for use on the viewing surface of the visual
display device. Transparent conductors arranged in
horizontal and vertical grid are supported on a flexible,
transparent overlay membrane which is adaptable to a
variety of displays. A unique interconnection pattern is
provided between the transparent conductors in the
array and buses which interconnect the conductors
with the supporting electronics, whereby a minimum
number of bus wires can be employed to service the
array conductors and yet both unique finger touch location sensing and unique stylus location sensing can be
accomplished. The system includes a control processor
which operates on stored program instructions which,
in a first embodiment provides for the alternate detection of either finger touch location or stylus location
and, in a second embodiment, provides for the simultaneous detection of both finger touch location and stylus
location. The resulting system provides the unique function of combined finger touch and stylus detection, is
adaptable to a variety of display surfaces, is provided
with a structure which is easily manufacturable, and
which has an inherent long-term reliability.

10 Claims, 25 Drawing Figures

PROCESSOR

X-BUS BO

Aug. 11, 1987

Primary Examiner-Stafford D. Schreyer
Attorney, Agent. or Firm-John E. Hoel

ADDRESSI
DATA BUS 110

STYWS 60

4,686,332

3~22

FIG. 2.
SEC 2-2\

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FIG. I.
(OVERLAY AND MOUNTING FRAME)

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a
STYLUS 60

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LOCATE THRESHOLD DISTANCE 62

tI.:l

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INNER SUBSTRATE 50

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u. S. Patent

Aug. 11, 1987

4,686,332

Sheet 3 of 17

FIG. 4.
USING THE WIRE PAIR CONCEPT. THERE ARE THREE MEASUREMENTS THAT ARE
NEEDED TO DETERMINE THE PEN'S HEIGHT AND POSITION. THESE MEASUREMENTS ARE
CALLED PO, PI, AND P2.
TO MEASURE

PAIR~O

P~

CONSIDER THE DRIVE PATTERN FOR AWIRE PAIR:

~60

~-o-------o----~~------'--X---~----X--------X---~
X2
~.
~
X5
Xs
(THE NUMBERS ARE FOR WIRE REFERENCE ONLY)

XI

0'" GROUNDED WIRE
X=DRIVEN WIRE

FIG. 5.
IF THE PEN WERE MOVED ACROSS THE TABLET ALONG THIS AXIS WITH THIS DRIVE
PATTERN CONSTANT, THE MEASURED SIGNAL WOULD BE:
PO
INCREASING
SIGNAL
MAGNITUDE

A
I
I

I

NOTE THAT WITHIN AND AROUND THE WIRE PAIR.l THE PEN SIGNAL VARIES LINEARLY
WITH POSITION. THIS LINEARITY IS THE BA~IS FOR ACCURATE INTERPOLATION
CALCULATIONS.

u. S. Patent

Sheet 4 of17

Aug. 11, 1987

4,686,332

FIG. 6.
THE NEXT DATA, PI, IS FORMED BY SHIFTING THE PREVIOUS PO PLOT TO THE
RIGHT BY ONE WIRE:
PI
INCREASING
SIGNAL
MAGNITUDE

A
I

I
I

FIG.

~

THE FINAL DATA. P2, IS THE INVERSE OF PO. THAT IS. ALL OF THE WIRES
BEING DRIVEN FOR PO ARE GROUNDED FOR P2. SIMILARLY. THE GROUNDED WIRES
FOR PO ARE DRIVEN FOR P2. AS ARESULT. THE SIGNAL PATTERN FOR P2 IS THE
MIRROR IMAGE OF PO ABOUT THE WIRE PAIR MIDPOINT:

****

u*******

P2

*****

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SIGNAL
MAGNITUDE

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FIG. 8.

a

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u.s. Patent

Sheet 9 of17

Aug. 11, 1987

4,686,332

FIG. 12.
OVERLAY 20
(DISPLAY AREA IBB)
SEC.12-lt

rr-----------

A
......- - - - - - - - - - - " ,

INNER LAMINATE 56
54 OUTER SUBSTRATE
Y3 TRANSPARENT WIRE
5t INSULATION LAYER

CRT 24

ANTIGLARE
&ABRASION
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OUTER LAMINATE 5B

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52'
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TRANSPARENT WIRE X2
INNER SUBSTRATE 50
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ANTI-NEWTON RING COAT 53
CRT GLASS FACE 32

FIG. 13X-BUS 80

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VERTICAL X-CONDUCTORS XI TO XII2 --"
ARRANGED IN SEVEN GROUPS OF 16 ARRAY
CONDUCTORS PER GROUP

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FIG.15C
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u. S. Patent

Aug. 11, 1987

Sheet 13 of 17

4,686,332

FIG. 16A.
PROXIMITY LOOP 200

REMOTE PROXIMITY STYLUS .-------,
SENSING 202

204'\
NO

FINGER TOUCH
SENSING
206

FIG./6.

OUTPUT
FINGER
LOCATION
YES

FIG. IIAo
YES

FIG. 168.
B'

FIG. 16&.

u.s. Patent

Aug. 11,1987

FIG. /68.

FIG. 16C.

r_-----'A----_,
LOCATE CYCLE 220

4,686,332

Sheet 14 of 17

TRACKING LOOP 240

B

C'

TRACK STYWS
X-LOCATION
242

LOCATE STYLUS
X-LOCATION
222

~---,

TRACK STYLUS
V-LOCATION
244

LOCATE STYLUS
Y-LOCATION
224

FINGER TOUCH
SENSING
246

FINGER TOUCH
SENSING
226

OUTPUT
FINGER
LOCATION
YES

OUTPUT
FINGER
LOCATION
YES

NO

NO
YES
C

C'
STYLUS LOST

~

STYillS PROXIMITY LOOP 200
MEASURE
CAPACITANCE
OF X-BUS)
WIRE
#1

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ARRAY WIRES
XI X2

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X-BUS

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ARRAY WIRES
YI Y2

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F1NG I
I FING I
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~YCLE 220

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STYLUS TRACKING LOOP 240

~ING I

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SAME

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----. i

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TIMING DIAGRAM SECOND EMBODIMENT

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SIGNAL

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FIG. I"Z

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I STY I

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MEMORY ORGANIZATION SECOND EMBODIMENT

SEQUENlL
CONTROL
ROUTINE
MUX. CTL.
REG.

I

STYWS
PROXIMITY
ROUTINE

I I STYLUS
LOCATE

II

2 3
V-BUS WIRE CAPACITANCE VALUES FILE

16 1

16 1

ROUTINE

MEAS. CTL.I
REG.

UTILIZATIONI
ROUTINE

FINGER
X-LOC
2-WIRE
TABLE

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FINGER
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u.s. Patent

Aug. 11,1987

Sheet 17 of17

4,686,332

FIG. 19.
DISPLAY AS SEEN
THROUGH OVERLAY
SHOWING SIMULTANEOUS
FINGER TOUCH
AND STYLUS
DETECTION

TOUCH CURSOR 270 .J

-

I-

20

- -, ' - STYLUS CURSOR 260-

22

1

4,686,332

COMBINED FINGER TOUCH AND STYLUS
DETECTION SYSTEM FOR USE ON THE
VIEWING SURFACE OF A VISUAL DISPLAY
DEVICE
BACKGROUND OF THE INVENTION
1. Technical Field
The invention disclosed broadly relates to data processing technology and more particularly relates to
input devices for use in conjunction with visual displays.
2. Background Art
In data processing systems, a central processor executes a sequence of stored program instructions to process data provided by an input device and to present the
resuits of the data processing operations to an output
device. Data processing results can be presented in
either alphanumeric text or in graphical form and a
universal mechanism for manifesting those results is by
means of a visual display device such as a cathode ray
tube monitor, a gas panel display, an array oflight emitting diodes, or other types of visual display devices.
Frequently, the results presented to the user on a visual
display device, will require the user to provide additional data to the data processing system. Various types
of data input devices have been employed in data processing systems, for example keyboard input, graphical
tablet input, and various forms of display surface inputs.
Human factors studies have shown that by providing a
means for inputting data on the visual display screen
itself, the user can achieve the most closely coupled
interactive operations with the data processing system.
When the user responds to visual signals output at the
face of the visual display device, by inputting signals at
that same visual display surface, an accuracy and immediacy in the interaction between man and machine can
be achieved. This form of input device is easy to learn to
use and seems the most natural and user-friendly to the
~~m

5

10

15

20

25

30

35

~

2

which is electromagnetically radiated from the surface
of the tablet and which is received by a pickup stylus
connected to a signal detector. In one type of opaque
graphics tablet, a field gradient is imposed from one side
to the other side of the tablet and the strength of the
field as picked up by the stylus, is correlated with the
position attributed to the stylus. Another approach has
been described by H. Dym, et al. in U.S. Pat. Nos.
3,992,579; 3,999,012; and 4,009,338, those patents being
assigned to the IBM Corporation. Dym, et al. describe
driving the conductors embedded in the opaque graphics tablets so that they are selectively energized with 40
kilohertz signals in a multiple stage operation to first
determine the stylus proximity to the surface of the
tablet and then to track the position of the stylus along
the surface of the tablet in the horizontal and vertical
directions. During the proximity stage of operation, the
conductors in all regions of the tablet surface emit signals which are detected by the stylus as it approaches
the surface. When the amplitude of the received signals
is great enough, the operation then changes into the
locate and tracking mode which is programmed to produce periodic indications of the stylus position with
respect to the horizontal and vertical conductors embedded in the tablet.
The popularity of the Personal Computer can be
attributed, in part, to the enhanced productivity which
can be achieved by applying data processing techniques
to the execution of tasks which were previously done
manually. Typical applications employing an interactive input at the display surface of the monitor in a
Personal Computer, require the operator to make control selections at the keyboard, perhaps selecting the
mode of operation or particular image to be displayed,
prior to using the interactive input device for inputting
data to the system. Fm example, in hotel management
applications, the operator would enter control information at the keyboard to select either a first displayed
image for a room assignment application or a second
displayed image for entering billing information. Only
after having made the control input at the keyboard,
will the operator be able to make data entries by means
of the interactive input at the display surface.

Various types of interactive input devices for use at
the display surface have been provided in the prior art.
One of the first forms of interactive devices was the
light pen, which is an optical detector provided in a
hand-held pen, which is placed against the display sur- 45
OBJECTS OF THE INVENTION
face of a cathode ray tube screen. When the dot of light
It is therefore an object of the invention to provide an
represented by the scanning raster is detected by the
improved interactive input device for a display surface.
light pen, the coordinates of the raster dot are attributed
It is another object of the invention to provide an
as the location of the hand-held pen. Another type of
interactive input device for use on a display surface is 50 interactive input device which permits either finger
touch input or stylus detection input modes.
the mechanical deformation membrane, which is a
It is yet a further object of the invention to provide an
transparent laminate placed over the display surface.
improved interactive input for a display surface which
The laminate consists of two conductor planes respeccan be adapted to a variety of surface contours.
tively deposited on a flexible medium so that when the
It is yet a further object of the invention to provide an
user mechanically displaces one of the conductor planes 55
improved interactive input for a display surface which
by a finger touch, the conductors are brought into elecis reliable and is inexpensive to manufacture.
trical contact with the conductors in the second plane.
It is yet a further object of the invention to provide an
The electrical resistance of the conductor plane is
interactive input device for use at a display surface,
changed as a function of the position of the finger touch
on the membrane and appropriate electronics are pro- 60 which permits the simultaneous detection of both a
finger touch and a stylus position.
vided to translate that resistance value into the position
attributed to the finger touch.
DISCLOSURE OF THE INVENTION
Opaque graphics tablets, upon which a sheet of drawA combined finger touch and stylus detection system
ing paper can be supported for tracing with an electronic stylus, have been provided in the prior art. In 65 is disclosed for use on the viewing surface of a visual
display device. The system includes an array of horiopaque graphics tablets, a horizontal wire grid and a
zontal and vertical conductors arranged on the viewing
vertical wire grid are embedded in the surface of the
surface of the visual display device, having an I/O tertablet. The wires in the tablet are driven with a signal

3

4,686,332

minal coupled thereto, for conducting electrical signals
between the terminal and the vicinity of the viewing
surface. A radiative pickup stylus is also included, having an output terminal, for receiving electromagnetic
5
signals radiated from the array.
The system includes a selection means having a
switchable path connected to the I/O terminal of the
array and having a control input, for connecting selected patterns of a plurality of the horizontal and vertical conductors to the switchable path in response to 10
control signals applied to the control input. A capacitance measuring means is also included, having an input
coupled to the switchable path of the selection means,
for measuring the capacitance of selected ones of the
conductors in the array, in response to the control sig- 15
nals applied to the control input.
The system further includes a radiative signal source
having an output coupled to the switchable path of the
selection means, for driving selected ones of the conductors in the array, in response to the control signals 20
applied to the control input. A radiative signal measuring means is also included, coupled to the radiative
pickup stylus, for measuring the electromagnetic signals
received by the stylus.
In addition, the system includes a control processor 25
connected to the control input of the selection means,
for executing a sequence of stored program instructions
to sequentially output the control signals to the selection means. The control processor is connected to the
capacitance measuring means, for receiving measured 30
capacitance values of the conductors when the selection
•.means, in response to the control signals, has connected
a first pattern of a plurality of the conductors in the
array to the capacitance measuring means, to detect the
location of a finger touch with respect to the viewing 35
surface of the display device. The control processor is
also connected to the radiative signal measuring means,
for receiving measured radiative signal values when the
selection means, in response to the control signals, has
connected a second pattern of a plurality of the conduc- 40
tors in the array to the radiative signal source, to detect
the location of the stylus with respect to the viewing
surface of the display device.
In this manner, both finger touch location and stylus
location with respect to the viewing surface of the dis- 45
play, can be detected.
The system can be used for both sequential and simultaneous detection of finger touch and stylus position.
The system makes use of a unique interconnection arrangement for the horizontal and vertical conductors to 50
respective buses which are of a reduced size, thereby
saving space and driver electronics. A unique overlay
membrane structure supports the horizontal and vertical conductors of the array and has sufficient mechanical flexibility to enable it to conform to the surface 55
contour of a variety of display surfaces.

4

FIG. 4 is a schematic view of the overlay for stylus
detection.
FIG. 5 illustrates the radiative signal amplitude for
measuring pair PO in stylus detection.
FIG. 6 shows the measurement for the pair PI for
stylus detection.
FIG. 7 shows the measurement for the pair P2 for
stylus detection.
FIG. 8 is a cross-sectional view of the overlay 20 and
the finger 70 for finger touch detection.
FIG. 9 is an architectural diagram of the detection
system.
FIG. 10 is a flow diagram of the operation of the first
embodiment of the invention for detecting either finger
touch or stylus position.
FIG. 11 is a rear view of the general layout of the
overlay 20.
FIG. 12 is a side cross-sectional view of the overlay
20 along the section line 12-12' of FIG. 11, showing
the detail of the display input area.
FIG. 13 is a front breakaway view of the overlay 20
in the bus region.
FIG. 14 is a side cross-sectional view along the section line 14-14' of FIG. 13.
FIGS. 15A; 15B; 15C are a front view of the layout of
the X bus for the overlay 20.
FIGS. 16A, B, & C are a flow diagram of a second
embodiment of the invention, when both finger touch
and stylus detection can be simultaneously carried out.
FIG. 17 is a timing diagram for the second embodiment of the invention, for the simultaneous detection of
both finger touch and stylus location.
FIG. 18 is a diagram of the memory organization for
the RAM 102 in the second embodiment of the invention.
FIG. 19 is a front view of the display as seen through
the overlay 20, showing the simultaneous finger touch
and stylus detection, in accordance with the second
embodiment of the invention.
DESCRIPTION OF THE BEST MODE FOR
CARRYING OUT THE INVENTION

The combined finger touch and stylus detection system is shown in a front view in FIG. 1 and in a side
cross-sectional view in FIG. 2, in association with a
cathode ray tube display. The overlay 20 consists of
two sheets of durable, transparent plastic, with an array
of horizontal transparent conductors embedded in the
first sheet and an array of vertical transparent conductors embedded in the second sheet. The overlay 20 can
be mounted by means of the frame 22 onto the display
surface 32 of the cathode ray tube 24. The mounting
frame 22 consists of a base portion 28 which attaches to
the sidewall 26 of the cathode ray tube (CRT) 24. The
front facing surface 30 of the base portion 28 can have
a curvature substantially the same as the curvature of
the display surface 32. The overlay 20 is mechanically
BRIEF DESCRIPTION OF THE DRAWINGS
flexible and can be laid directly upon the surface 32 of
The foregoing and other advantages of the invention
the CRT so that its edges overlap the surface 30 of the
will be more fully, understood with reference to the 60 base portion 28 for the mounting frame 22. The clampdescription of the best mode and the drawing wherein:
ing member 34 can then be placed over the edges of the
FIG. 1 is a front view of the overlay 20 and the
overlay 20 so that the mating surface 38, which has a
mounting frame 22.
curvature similar to that of the surface 30, clamps the
FIG. 2 is a side cross-sectional, breakaway view of
edges of the overlay 20. The mounting bolts 36 secure
the overlay and mounting frame of FIG. 1, along with 65 the member 34 to the base portion 28.
section line 2-2'.
FIG. 2 shows a cross-sectional view of the overlay 20
FIG. 3 is a side view of the overlay 20 and the stylus
positioned on the display surface 32 of the CRT. The
60 for stylus detection.
overlay is stretched slightly by the mounting frame, to

5

4,686,332

provide a smooth, tight and well supported surface for
finger touch and stylus detection. The overlay shown in
FIG. 3 consists of the inner substrate 50 which is a sheet
of polyethylene terephthalate which is transparent,
electrically insulative, and has a thickness of approximately 0.002 inches. An array of horizontal transparent
conductors is deposited on the surface of the inner substrate 50 and are designated as Yl, Y2, Y3, etc., with the
Y3 wire being shown in FIG. 3. The transparent conductors can be composed of indium tin oxide, for exampie, which is a well-known transparent conductor material. The thickness of the transparent conductor can be
approximately 1000 angstroms. The conductors are
approximately 0.025 inches wide and are spaced approximately 0.125 inches on a center-to-center spacing.
An insulation layer 52 covers the horizontal Y wires
and can be composed of a transparent adhesive such as
ultraviolet initiated vinyl acrylic polymer having a
thickness of approximately 0.002 inches. The upper
portion of the overlay 20 shown in FIG. 3 consists of
the outer substrate 54 which is a sheet of polyethylene
terephthalate which is optically transparent, electrically
insulative and has a thickness of approximately 0.002
inches. Deposited on the surface of the outer substrate
54 is a vertical array of transparent conductors designated Xl, X2, X3 ... X6 .... The conductors Xl, etc.
are also composed of indium tin oxide and have a thickness of approximately 1000 angstroms, a width of approximately 0.025 inches and a spacing of approximately 0.125 inches, center-to-center. The outer substrate 54 and the vertical conductors X are joined by the
adhesive insulation layer 52 to the inner substrate 50 and
the horizontal wires Y. The X and the Y transparent
conductors can also be composed of gold and silver or
other suitable materials. The thickness of the conductors is adjusted to provide resistance below 50 ohms per
square and an optical transmission which is greater than
80 percent.
FIG. 3 depicts the arrangement for detection of the
stylus 60 when it is closer than the locate threshold
distance 62. The principle of operation in the stylus
detection mode is that the X and/or Y conductors are
driven by a 40 kilohertz oscillator driver so that the X
and/or Y conductors act as a transmitter of electromagnetic radiation and the stylus 60 acts as a receiver of that
radiation. To transmit a signal, the oscillator selectively
drives either the X conductors or the Y conductors.
The stylus 60 detects the signal and electronics connected to the stylus digitizes the magnitude of the signal. The magnitude of the signal detected by the stylus
is a function of the height of the stylus above the overlay 20. By comparing this magnitude to known thresholds, the height of the stylus above the overlay can be
determined. When the stylus signal has reached the
contact threshold corresponding to the locate threshold
distance 62, the operation of stylus detection can shift
from proximity detection to a location and tracking
mode. The object of tracking the stylus is to have the X
conductors and the Y conductors in the overlay driven
in such a manner that the radiation picked up by the
stylus 60 can enable the attribution of an instantaneous
position for the stylus.
The basic drive pattern for determining the stylus
position is schematically shown in FIG. 4. A wire pair
is defined as two adjacent X conductors, for example,
with the left-hand conductor aIJd several conductors to
the left thereof being either grounded or connected to a
first reference potential and the right-hand conductor

5

10

15

20

25

30

35

40

45

50

55

60

65

6

and several conductors to the right thereof being driven
by the oscillator driver. FIG. 4 shows the wire pair PO
located beneath the stylus 60, with the conductor X3
being the left-handed conductor and the conductor X4
being the right-handed conductor. The conductors Xl,
X2 and X3 are connected to ground potential whereas
the conductors X4, X5 and X6 are connected to the
oscillator driver. FIG. 5 shows the amplitudl': of the
signal received by the stylus 60 as it would pass from
left to right from above the conductor Xl to a position
above the conductor X6. Note that within and around
the wire pair X3 and X4, the stylus signal varies linearly
with position. This linearity is the basis for an accurate
interpolation technique for providing a precise measure
of the position of the stylus 60 based upon the measurement of radiation from three wire pairs. The first stage
in the measurement is measuring the amplitude for the
wire pair PO. FIG. 6 shows the second stage in the
measurement where the wire pair PI is formed with the
conductors X4 and X5. The plot of the magnitude of the
signal received by the stylus 60 which remains fixed at
its location shown in FIGS. 4 and 5, would indicate a
lower relative measured amplitude for the wire pair PI
measurement. The final data in the three stage operation
of locating the position of the stylus 60 is shown in FIG.
7, where the wire pair P2 is the inverse of the wire pair
PO. That is, the conductors Xl, X2 and X3 are driven
with the oscillator driver, whereas the conductors X4,
X5 and X6 are connected to ground or reference potential. The signal amplitude is shown for the wire pair P2
in FIG. 7. Once again, with the stylus 60 remaining in
the same position that it had for FIGS. 4, 5 and 6, the
magnitude of this signal for the wire pair P2 will be
measured.
The calculation of the horizontal position of the stylus 60 with respect to the vertical X conductors Xl, X2,
X3, etc. is done in two stages. First, the base coordinate
is calculated and then second an offset coordinate is
calculated which is added to the base coordinate to
form the resultant measured position. To calculate the
base coordinate, the system calculates the number of
wires between the origin of coordinates at the left-hand
edge of the overlay and the first wire adjacent to the
axis of the stylus 60. This number of wires is multiplied
times the pitch of the X conductor separation, in this
case 0.125 inches, to obtain the base coordinate value.
The base coordinate produced is the midpoint between
the wire pair X3 and X4 in this example.
The offset coordinate is the coordinate of the stylus
relative to the midpoint of the wire pair X3 and X4. The
offset coordinate is equal to the wire separation pitch in
the horizontal direction times (PO-P2) divided by
2x(PO-PI). The numerator of this expression is a linear
expression within a wire pair whereas the denominator
is a constant. Both of these terms depend upon the angle
of the stylus with respect to the tablet which can vary
during normal operation. The division operation cancels this dependence, allowing the expression to be
invariant as to the angle at which the stylus is held. The
resulting ratio varies linearly between approximately
- 1 and + I and, when multiplied times the pitch, gives
an additive factor which, when added to the base coordinate, results in the interpolated value for the horizontal position of the stylus with respect to the vertical X
conductors. The resolution for this measurement is
typically 0.01 inches. A similar operation is conducted
for the horizontal conductors YI, Y2, etc. to establish

4,686,332

7
the vertical position of the stylus with respect to the
horizontal conductors.
It is seen that in order to locate position of the stylus
with respect to the vertical conductors, the vertical
conductors must be arranged with each conductor in 5
any group of at least six adjacent conductors, uniquely
connected to the oscillator driver. A similar condition
must also prevail for the horizontal Y conductors. As
was previously mentioned, in order to obtain an approximately 0.01 inch resolution, a grid pitch of approxi- 10
mately 0.125 inches must be maintained for the conductors in both the horizontal direction and in the vertical
direction. If a display area of 12-13 inches in the horizontal and the vertical direction is to be covered by the
overlay, then approximately 100 vertical X conductors 15
and 100 horizontal Y conductors will be required in the
overlay 20. If 200 different drivers were required to
drive all 200 conductors, the mechanical and electrical
complexity necessary to make that connection would be
prohibitive. It is clearly advantageous to provide some 20
means for reducing the number of driver wires which
interconnect the conductor wires in the array to the
oscillator driver. Dym, et aJ. have provided in their
above cited patents, a busing technique which employs 25
a horizontal bus having 24 separate driver wires each of
which are respectively connected to several vertical
conductors in the opaque graphics tablet disclosed
therein. The horizontal conductors are similarly arranged and are connected through a vertical bus also 30
having 24 wires. Taking the vertical array conductors
for example, the 24 wires in the horizontal bus feeding
the vertical array conductors were classified into three
sets of eight wires each. The vertical array conductors
were divided into groups. To make the individual 35
groups of array conductors unique for the purposes of
detection by the stylus, the order of the array conduc. . tors is changed for every group. This reduced the number of drive wires in the bus since each wire in the bus
was connected to and drove multiple array conductors. 40
The separation between array conductors connected to
the same bus wire has to be large enough so that signals
sensed in one region of the array are not influenced by
the other conductors in the array connected to the same
bus wire.
45
The problem with the arrangement of the array conductors as described by Dym, et aJ. for their opaque
graphics tablet, is that it cannot be used for the capacitive detection of a finger touch such as is illustrated in
FIG. 8. The finger 70, when touching the surface of the 50
outer substrate 54 in FIG. 8, will, at best, approximately
cover only two adjacent array conductors, in the case
illustrated, X3 and X4. If the location of the finger 70 is
to be measured with the resolution equivalent to the
pitch of the conductors, in this case 0.125 inches, then 55
the capacitance change for a first conductor and for an
adjacent second conductor must be measured. In the
case of FIG. 8, the capacitance CF3 between the finger
70 and the X3 conductor must be measured and the
capacitance CF4 between the finger 70 and the conduc- 60
tor X4 must be measured. The capacitance of all the X
conductors XI-X5 and all of the Y conductors can be
measured, but the finger location is determined by identifying the two adjacent vertical X conductors and the
two adjacent horizontal Y conductors having the maxi- 65
mum change in their capacitance. The array conductors
must be connected to their bus drive wires in such a
manner that each adjacent pair of array conductors

8

constitutes a unique combination which is never duplicated elsewhere on the array. One of the problems
solved by the invention disclosed herein is how to combine both finger touch detection and stylus location
detection using the same array of horizontal and vertical conductors connected through their respective
drive buses.
FIG. 11 is a rear view over the overlay 20 showing
the general layout of the overlay. The X bus 80 consists
of 16 drive wires 1, 2, ... 16 and similarly the Y bus 90
consists of 16 bus wires. The X bus 80 is connected

through the X connector 182 to the drive electronics.
Similarly, the Y bus connector 184 connects the Y bus
90 to the drive electronics. The display input area 188
has the transparent array conductors arranged therein
with the vertical transparent conductors XI-X112 selectively connected to the bus wires 1-16 in the X bus
80. Correspondingly, the horizontal transparent conductors Yl-Y112 are selectively connected to the 16
bus wires of the Y bus 90. FIG. 13 is a front detailed
view of the X bus 80, showing the bus wires 1, 2, 3, 4
and 5 of the X bus 80. Two vertical transparent array
wires Xl and X2 are shown respectively connected to
the X bus wires 1 and 3, for example. FIG. 14 is a crosssectional view of FIG. 13, showing how the horizontal
bus wire 3 connects through an aperture 180 in the
insulation layer 52 to make connection to the transparent wire X2. The actual pattern for interconnecting the
16 bus wires 1-16 the X bus 80 to the 112 vertical, transparent array conductors XI-X112, is shown for the X
bus layout in FIG. 15. The order of connection is also
given in Table I.
In the preferred embodiment, the number of vertical
array conductors Xl, X2, ... , which must be capable of
independent control, is a function of the pitch of the
wires in the array (the number per unit distance in the
horizontal direction), the number of position determinations per unit time (the sampling rate of the wires in the
array), and the maximum speed of the stylus movement
which is desired to be accommodated. Using the wire
pair concept shown in FIGS. 4-7, let the number of
wires to the left of the wire pair (including the left-hand
member of the pair) be the quantity M and let there also
the same number M of wires to the right of the wire pair
(including the right-hand member of the pair). The total
quantity of 2M adjacent wires represents a group,
which must span a horizontal distance great enough to
exceed the maximum allowable distance which will be
displaced by the stylus during one interval between
successive position determinations (the sampling interval). In each group of adjacent 2M wires, each wire
must be uniquely connected to one of the plurality of
bus wires in the horizontal bus 80. The same is equally
true for the horizontal array conductors Yl, Y2, ....
For example, if the maximum speed of the stylus is 48
inches per second, the sampling rate is 100 position
determinations per second, the pitch of the wires is
0.125 inches, then the quantity of M will be four wires
on each side of the wire pair. In this example, the array
must be organized so that each group of eight adjacent
wires has each wire therein uniquely connected to the
bus wires in its corresponding bus, in order to accurately track the position of the stylus moving at up to 48
inches per second. A wiring pattern which will accommodate this example is shown in Table I and in FIG. 15.

4,686,332

9

10

TABLE I
Sequence With Four-Wires-On
Drive No.
16
2
I 14
Occurrence
I
I
I
I
N to Self
N to Four
Drive No.
3 14
Occurrence
2
2
2
N to Self
12 15 12 16
N to Four
10
9 10
9
4
Drive No.
16
I
2
Occurrence
2
3
3
3
N to Self
31 16 13 17
N to Four
11 10 II 10
Drive No.
4
2
3
5
4
4
Occurrence
4
4
N to Self
13 17 12 17
10 10 II 10
N to Four
Drive No.
16
4
6
3
Occurrence

N to Self
N to Four
Drive No.

4
31

II

Occurrence

N to Self
N to Four
Drive No.

6
6
13

II

Occurrence

N to Self
N to Four

16
6
31
11

5
14
10
5
6
17
10
6
7
16

10

Tracking
13
I

3
I

4
2
12
10
5
3
13
II
6
4
13

13
2
16
9
14

12
I

4
I

II
I

5

6
2
12
10
7
3
13
II
8
4
13
II
9
5
13
II
10
6
13
11
II
7
13
11

6
13

12
2
16
9
13
3
17
10
14
4
17
10
I
5
17
10
2
6
17

2
12
10
6
3
13
II
7
4
13

7
6
13

5
17
10
4
6
17

8
6
13

17
10
I
4
17
10
2
5
17
10
3
6
17

II

10 II

10

II

10

4
7
17

10

3
7
17

5
13

II

8
7
13
11

5
7

17
10

II
7
5
13

II

9
7
13
11

10

II
8
5
13

II
9

7
13
11

10

10
I

11
2
16
10
12
3
17
12
13
4
17
10
14
5
17
11
I
6
17

10
2
7
17
11

6
I

9
I

7
2
12
II
8
3
13
9
9
4
13
II
10
5
13
9

10
2
16
II
II
3
17
10
12
4
17
II
13
5
17
10
14
6
17

8
2
13
9
9
3
16
II
10
4
13
9
II
5
14
II
12
6
13
9
13
7
14

II
6
13
11
12
7
13
9

10
1
7
17
10

II

To reduce the number of elements in the X bus 80,
each bus wire 1-16 drives multiple X array conductors
XI-X112. The separation between those X array conductors which are attached to the same bus wire, must
be large enough so that signals sensed in one region of
the overlay 20 are not affected by the other conductors
connected to that same bus wire. The bus attachment
pattern must isolate conductors attached to the same
bus wire, by a sufficient distance to avoid confusion
errors in the stylus locate mode and the stylus tracking
mode. In the locate mode, the distance between any
three adjacent vertical array conductors and the next
occurrence of any of those conductors that is attached
to the same bus wire, must be greater than the maximum
height 62 at which a locate operation can begin, as is
shown in FIG. 3. For the tracking mode, the distance
between any group of adjacent wires that are driven
simultaneously during the tracking operation, as shown
in FIGS. 4-7, with respect to the next occurrence of
another conductor connected to the same bus wire,
must be greater than the expected displacement of the
stylus which may occur during one complete tracking
position determination cycle. This is typically approximately 0.75 inches. Added to this is the constraint necessary to accomplish capacitance finger touch sensing.
Fingers are sensed by the change in capacitance when
the fingers cover the transparent array conductors.
Low force touches only change the capacitance of two
adjacent conductors. The bus wire attachment sequence
must be patterned so that the finger sensing portion of
the system can identify capacitance changes in two
adjacent conductors as a touch, which is unique and
will not occur for any other combination of adjacent
conductor pairs in the array. The essential finger sensing constraint is that only one pair of adjacent conductors in the array should be connected to the same pair of
bus wires. In a 16 wire bus such as the X bus 80, there
are 120 unique combinations of adjacent pairs of wires
which will satisfy this condition. If there were a quantity of N bus wires in the bus, then there would be
N(N -1) divided by 2 unique combinations of adjacent
pairs of conductors which will satisfy this condition.

15
I

9
2
16
10
16
3
12
10
11
4
17
10
16
5
12
10
13
6
17

10
16
7
12
12

15
2
14
10
10
3
18
II
15
4
14
11
12
5
18
11
15
6
13
11
14
7
18
15

3
3
12
10
15
3
16
9
5
5
12
10
15
5
16
10
7
7
12

10
15
7
16
16

The bus wire attachment pattern requirement is to se30 lect a sequence that meets these adjacent conductor
constraints and which maintains an adequate grid distance between groups of wires which are attached to
the same bus wire. The allowable bus wire attachment
sequences will differ for different numbers of bus wire
35 elements N and for different numbers of array conductors X for vertical conductors. The greater the number
of bus wires, the easier it is to meet the physical constraints on tracking speed and the threshold distance for
stylus detection, for a given size overlay. All of the
40 above considerations apply equally to the horizontal Y
array conductors as they do for the vertical X array
conductors.
Table I and FIG. 15 represent an optimum bus connection sequence for the condition that the bus contains
45 16 bus wires which are connected to 112 transparent
array conductors. The pattern was created by interleaving ascending and descending sequences of bus wires
for most of the array conductors and then making special adjustments at the end to fill out the set of 112 array
50 conductors in either the horizontal or the vertical direction.
FIG. 11 shows the general layout of the overlay 20
and shows the relative position of the four bolt holes
186 through which the bolts 36 of FIG. 2 pass, enabling
55 the mounting of the overlay 20 onto the face of the
CRT 24. ,The display input area 188 is shown in crosssectional view in FIG. 12. The overlay is comprised of
two major portions, the inner laminate 56 and the outer
laminate 58 which are attached as shown in FIG. 12 by
60 the adhesive layer 52'. The inner laminate 56 is
stretched upon the outer surface of the glass face 32 of
the CRT 24. The inner laminate 56 has an anti-newton
ring coating 53 which is applied to the display side of
the overlay to eliminate newton rings when the inner
65 laminate comes into contact with the glass face 32. An
electrostatic shield layer 51 consists of a full panel coating of indium tin oxide which is grounded. This coating
shields the vertical X conductors and horizontal Y con-

11

4,686,332

12

connected through the gate 120 to the radiative pickup
ductors from electrostatic noise generated by the cathmeasurement device 122. The wire selection multiode ray tube 24. The electrostatic shield layer 51 must
plexer 112 is connected through the mode multiplexer
be less than 100 ohms per square and must exceed an
116 to the capacitance measurement device 128 which is
optical transmissivity of 80 percent. The inner substrate
layer 50 is an optically clear layer of polyethylene tere- 5 used for capacitance finger touch detection. The wire
selection multiplexer 112 is also connected through the
phthalate onto which is magnetron sputtered the transparent wire coating of indium tin oxide which will remode multiplexer 116 to the 40 kilohertz oscillator
sult in the vertical transparent conductors Xl, X2, etc.
driver 126 which is used to drive the X bus 80 and the
Y bus 90 for the stylus detection operation. The mode
The indium tin oxide coating is etched to provide 0.025
inch wide lines on 0.125 inch center line spacing. The 10 multiplexer 116 also has an enabling output to the gate
resistance of the indium tin oxide layer must not exceed
120 to selectively connect the output of the stylus 60 to
the radiative pickup measurement device 122, for stylus
80 ohms per square. There are 112 transparent, vertical
conductors Xl, X2, ... X112. The outer substrate layer
detection operations. The output of the capacitance
measurement device is connected through the analog54 of the outer laminate 58 is substantially the same as
the inner substrate 50 and the indium tin oxide transpar- 15 to-digital converter 130 to the processor address/data
bus 110. The output of the radiative pickup measureent conductor layer deposited on the outer substrate 54
ment device 122 is connected through the analog-tohas the same properties as the indium tin oxide transparent wire layer deposited on the inner substrate 50. The
digital converter 124 to the bus 110. A control input 114
horizontal Y conductors Y1, Y2, ... Y112 on the outer
to the wire selection multiplexer 112 is connected to the
substrate 54 are oriented at right angles with respect to 20 bus 110 and the control input 118 to the mode multiplexer 116 is connected to the bus 110. The processor
the vertical X conductors deposited on the inner substrate 50. During manufacture, the inner laminate 56 is
address/data bus 110 interconnects the control processor 100 with the read only memory (ROM) 104, the
built up as a composite and is coated with the insulation
layer 52 which is a thin layer of ultraviolet initiated
random access memory (RAM) 102, and the I/O convinyl acrylic polymer. Similarly, during manufacture, 25 troller 106. The I/O controller 106 has an I/O bus 108
the outer laminate 58 is coated with the insulation layer
which connects to a host processing system such as the
52" which is identical in composition with the insulation
I/O bus of an IBM Personal Computer.
The wire selection multiplexer 112 and the mode
layer 52. After the inner laminate 56 and the outer laminate 58 have been respectively constructed as separate
multiplexer 116 connects selected patterns of a plurality
composites, they are joined with the adhesive layer 52' 30 of the horizontal and vertical conductors in the overlay
which has the same composition as the insulation layer
20 to either the capacitance measurement device 128 or
.. 52. The resulting overlay composite 20 has an overall
the 40 kilohertz oscillator driver 126, in response to
control signals applied over the control inputs 114 and
thickness in the display input area 188 of approximately
118 from the bus 110 by the control processor 100.
0.005 inches, has a high optical transparency, and has a
durable mechanical quality. The overlay 20 can be 35 During finger touch operations, the capacitance meastretched and bent within limits to conform to the cursuring device 128 has its input coupled through the
vature of the cathode ray tube display surface, without
mode multiplexer 116 and the wire selection multiplexer
112 to selected ones of the horizontal and vertical conrupturing the electrical continuity of the transparent
conductors in the array. In an alternate embodiment,
ductors in the overlay 20 in response to control signals
·the X and Y array conductors could be deposited on the 40 from the control processor 100. The output of the capacitance measurement device 128 is converted to digiouter laminate 54 and the inner laminate 56, respec,tively.
tal values by the converter 130 and is applied over the
bus 110 to the control processor 100, which executes a
FIG. 13 shows a front view of the X bus 80 for the
overlay 20 and FIG. 14 shows a side cross-sectional
sequence of stored program instructions to detect the
view, illustrating how the bus wire 3 is electrically 45 horizontal array conductor pair and the vertical array
conductor pair in the overlay 20 which are being
connected to the transparent array conductor X2.
touched by the operator's finger. In the stylus detection
When the insulation layer 52 is applied to the surface of
mode, the 40 kilohertz output of the oscillator driver
the inner laminate 56, it is deposited in a printing operation such as silk screening so that the array of apertures
126 is connected through the mode multiplexer 116 and
180 and 180' as shown in FIGS. 13 and 15 are left open 50 the wire selection multiplexer 112 to selected ones of
exposing selected transparent conductors. Thereafter,
the conductors in the overlay 20, in response to control
silver ink bus wires 1-16 are deposited on the outer
signals applied over the control inputs 114 and 118 from
surface of the insulation layer 52 so that they pass over
the control processor 100. The electromagnetic signals
selected ones of the apertures 180 and 180', thereby
received from the overlay 20 by the stylus 60 are passed
making electrical contact with the selected, exposed 55 through the gate 120 to the radiative pickup measurearray conductors. For example, as is shown in FIG. 13
ment device 122, which measures those signals and
and FIG. 14, the bus wire 3 passes through the aperture
provides an output which is digitized by the converter
180 in the insulation layer 52 and makes electrical
124 and output to the control processor 100. The concontact with the vertical transparent conductor X2.
trol processor 100 executes a sequence of stored proThe resistance of the silver ink bus wires 1-16 does not 60 gram instructions to detect the proximity of the stylus to
exceed 20 ohms per inch for a 0.015 width line. The
the overlay 20 in the proximity detection mode and then
thickness of the bus wires does not exceed 0.001 inches.
to locate and track the horizontal and vertical position
FIG. 9 shows an architectural diagram of the detecof the stylus with respect to the overlay 20 in the location system. The vertical conductors X1-X112 are contion and tracking mode. The stored program instrucnected through the X bus 80 to the wire select multi- 65 tions for carrying out these operations can be stored in
plexer 112 and the horizontal Y conductors Y1-Y112
the read only memory 104 and/or the RAM 102, for
are connected through the Y bus 90 to the wire selecexecution by the control processor 100. Positional valtion multiplexer 112. The radiative pickup stylus 60 is
ues and other result information can be output through

13

4,686,332

the I/O controller 106 on the I/O bus 108 to the host
processor for further analysis and use in applications
software.
FIG. 10 is a flow diagram of a first embodiment of the
invention where either finger touch operations or alternately stylus detection operations can be carried out,
one to the exclusion of the other during a particular
sensing interval. During the proximity search mode, the
capacitance finger touch operations are interleaved
with the radiative stylus pickup operations to determine
whether either a finger touch has been initiated or a
stylus has been brought into threshold proximity to the
overlay 20. When either of these conditions are found,
the stored program instructions represented by the flow
diagram of FIG. 10, will lock out the opposite search
sequence and will proceed to the locate sequence for
the finger touch or for the stylus detection, whichever
has been sensed.
This alternate scanning for either the initiation of a
finger touch or the beginning of stylus detection is carried out by steps 140-148 and 154-160 of the flow diagram of FIG. 10. In step 140, the X-drive sequence is
updated followed by step 142 where the touch sensing
function of the capacitance measurement device 128 is
turned on by appropriate control signals to the mode
multiplexer 116 and the wire selection multiplexer 112.
Then in step 144 the X axis conductors in the overlay 20
are sensed by the capacitance measurement device 128.
In step 146 the signal strength for capacitive coupling
by a finger touch is determined by the control processor
100. Control processor 100 then determines whether the
touch threshold has been crossed in step 148. If the
touch threshold has been crossed, the program transfers
to step 150 to the touch locate mode. If the touch
threshold has not been crossed, the program transfers to
step 154 to determine whether the stylus has come into
close proximity to the overlay 20. In step 154, the mode
multiplexer 116 disconnects the capacitance measurement device 128 and connects the 40 kilohertz oscillator
driver 126 to the overlay 20 through the wire selection
multiplexer 112. The mode multiplexer 116 also enables
the gate 120 so that the received signals by the stylus 60
can be passed to the radiative pickup measurement device 122. In step 156, proximity sensing operations are
carried out by the oscillator driver 126 driving a plurality of either the X conductors or the Y conductors or
both X and Y conductors in the overlay 20 and by the
radiative pickup measurement device 122 determining
whether the stylus 60 has received a sufficiently large
magnitude signal to indicate close proximity of the styIus to the overlay. In step 158, the signal strength measured by the radiative pickup measurement device 122
is analyzed by the control processor 100 and in step 160
the control processor 100 determines whether the stylus
threshold has been crossed. If the stylus threshold has
not been crossed, then the program returns to step 140
to check again as to whether a finger touch has been
initiated. If the stylus threshold has been crossed in step
160, then the program passes to step 162 for the stylus
locate and tracking mode to begin.
When the touch threshold has been crossed, as determined by step 148, the program passes to step 150 where
the touch locate mode begins. The capacitance measurement device 128 is connected through the mode
multiplexer 116 and the wire select multiplexer 112 and
the capacitance of each respective vertical bus wire
1-16 in Y-bus 90 and each respective horizontal bus
wire 1-16 in X-bus 80 is measured and their values

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digitized by the converter 130 and output over the bus
110 to the control processor 100. The control processor
100 identifies the unique pair of the 112 vertical X conductors XI and XI + 1 having the highest capacitance
and that is attributed as the horizontal position of the
finger touch. Correspondingly, the unique pair of the
112 horizontal Y conductors Yl and Yl + 1 having the
highest capacitance values are identified and those are
attril:iuted as the vertical location for the finger touch.
This information is output by the control processor 100
through the I/O controller 106 to the I/O bus 108.
If the stylus detection threshold is crossed in step 160,
then the stylus locate and tracking mode in step 162
commences. The vertical X conductors X1-X112 are
energized in groups of at least six conductors in a manner previously described for FIGS. 4-7, and the magnitude of the electromagnetic signals radiated therefrom
are picked up by the stylus 60, measured by the radiative pickup measurement device 122 and the digital
values output from the converter 124 are passed to the
control processor 100. A similar operation takes place
for the horizontal Y conductors Y1-Y112 in the overlay
20. The control processor 100 then processes these
signals to locate the horizontal and vertical position of
the stylus with respect to the overlay 20 and this resultant information is output through the I/O controller
106 to the I/O bus 108. The operation of tracking the
consecutive positions of the stylus 60 with respect to the
overlay 20 then takes place by sequentially updating the
position of the stylus 60. If the magnitude of the signals
received by the stylus 60 diminishes as determined in
step 166, the program then passes back to step 140
where the finger touch initiation and stylus proximity
detection operations are alternately carried out.
A second embodiment of the invention is shown in
FIGS. 16-19 where, instead of locking out either the
finger touch operation or the stylus detection operation
when the other is being conducted, in the second embodiment both finger touch and stylus detection operations can be carried out simultaneously. This is achieved
by multiplexing stylus detection and finger touch sensing in the proximity loop 200, multiplexing stylus location and finger touch sensing in the locate cycle 220,
and multiplexing track stylus location detection and
finger touch sensing in the tracking loop 240, as shown
in the flow diagram of FIG. 16.
FIG. 16 shows the proximity loop 200 including steps
202-210 and FIG. 17 shows the timing diagram which
includes the stylus proximity loop 200. As was previously mentioned, stylus proximity is determined by
radiating a uniform 40 kilohertz signal from the overlay
20 and determining whether the stylus 60 is picking up
a sufficiently large amplitude representation of that
signal to pass a threshold value. This is represented by
step 202 of the proximity loop 200. In step 204, the
control processor 100 determines if the threshold has
been passed and if so, the control processor 100 sets a
flag Sl. Whether the stylus proximity threshold has
been exceeded or not, the program then passes to step
206 where the finger touch sensing operation takes
place, during which the capacitance measurement device 128 is sequentially connected to each of the 16 bus
wires in the X bus 80 and each of the 16 bus wires in the
Y bus 90. The control processor 100 determines in step
208 whether the capacitance for any of the vertical
array conductors X1-X112 or any of the horizontal Y
conductors Y1-Y112 is greater than a threshold value
and if it is, then the adjacent pair of vertical array con-

15

4,686,332

16

tal and vertical coordinates attributed to the position of
ductors and the adjacent pair of horizontal array conthe finger touch can both be output, substantially simulductors which have the highest measured capacitance,
taneously, by the control processor 100 to the I/O bus
are identified by the control processor 100 and attrib108. In step 250, the control processor 100 determines
uted as the location of a finger touch which is output by
the I/O controller 106, as previously described. The 5 whether the amplitude of the signal received by the
stylus 60 is less than the threshold value for proximity
program then passes to step 210 to test whether the flag
detection. If the magnitude is greater than the threshold
Sl is on or off indicating whether the proximity threshvalue, then the program passes to step 242, continuing
old for stylus detection was passed in step 202. If Sl is
the tracking loop cycle: If the magnitude of the signal
still off, then the program returns to step 202 to once
again test for the proximity of the stylus. This operation 10 detected by the stylus 60 is less than the threshold value,
then the program passes back to the proximity loop 200
for the stylus proximity loop 200 is shown in the timing
diagram of FIG. 17. The control processor 100 can
and restarts step 202 for the remote proximity stylus
sensing operation. This is shown for the stylus tracking
access a table stored in the RAM 102 and perform a
loop 240 as depicted in the timing diagram of FIG. 17.
table lookup to determine the correlation between the
16 bus wires in the X bus 80 and the corresponding 15
Thus it is seen that in the second embodiment of the
invention, the system can be operated so as to provide
vertical conductor adjacent pairs and also the 16 bus
wires in the Y bus 90 and the corresponding horizontal
the simultaneous detection of both the pickup stylus 60
adjacent conductor pairs, thereby speeding up the operand a finger touch. This is depicted in FIG. 19, which is
a view of the display as seen through the overlay 20,
ation of finger touch location.
If step 202 detected that the stylus had come within 20 showing the simultaneous display of the touch cursor
the threshold proximity distance to the overlay 20, then
270 whose location is produced by the host computer
the flag Sl would have been turned on and step 210
based upon the coordinates for the finger touch output
would have passed program control to the locate cycle
over the I/O bus 108 by the control processor 100. Also
depicted in FIG. 19 is the display of the stylus cursor
220. This would involve the passage of the program to
step 222 where the stylus location procedure, as de- 25 260, whose image is produced by the host processor,
based upon coordinates for the stylus which are output
scribed above, would be carried out for the vertical
array conductors X1-X112 and then the program
over the I/O bus 108 by the control processor 100.
would pass to step 224 to perform a similar stylus locaFIG. 18 depicts an example memory organization for
tion operation for the horizontal array conductors
the RAM 102 in the second embodiment of the invenY1-Y112. Here again, tables can be stored in the RAM 30 tion, where the RAM 102 is connected by the processor
bus 110 to the control processor 100, as is seen in FIG.
102 which correlate detected amplitude maximum by
the stylus 60 with the position attributable to the stylus
9. The RAM 102 can be partitioned into a sequence
control routine which is a sequence of stored program
in the horizontal and vertical directions. In step 222, the
control processor 100 will output the X location attribinstructions which carries out the operation depicted in
uted to the stylus 60 and in step 224 the control proces- 35 the flow diagram of FIG. 16. The stylus proximity routine, the stylus locate routine and the stylus tracking
sor 100 will output the Y location attributed to the
routine are each a sequence of stored program instrucstylus 60, in the same manner as was described above.
tions for carrying out the respective operations of proxThe locate cycle 220 then passes control to step 226
imity detection, location and tracking of the stylus, as
. where, once again, the finger touch sensing operation
'takes place in a manner similar to that described for step 40 previously described. A finger locate routine is a sequence of stored program instructions to carry out the
.206. If an increased capacitance for the array conductors is detected in step 226, then the control processor
operation of locating the coordinates of a finger touch,
100 in step 228, will output the coordinates for the finas previously described. Multiplex control registers and
ger touch through the I/O controller 106 to the I/O bus
measurement control registers can be provided in the
108, as previously described for step 208. Note that both 45 RAM 102. Optionally, a cursor shape table can be included in the RAM 102 to define the shape of the. touch
the stylus location and the finger touch location can be
separately and substantially simultaneously output by
cursor 270 and the stylus cursor 260, or alternatHy the
function of the cursor shape table can be carried out in
the control processor 100 over the I/O bus 108 during
the locate cycle 220. This can be seen for the representathe host processor. The X bus wire capacitance value
tion of the stylus locate cycle 220 in FIG. 17.
50 file and the Y bus wire capacitance value file will provide temporary storage for the measured values of each
The program then passes to the tracking loop 240 as
shown in FIG. 16 and for which a timing diagram is
of the respective 16 bus wires in the X bus 80 and the Y
bus 90 during the finger touch sensing operations of
shown in FIG. 17. Step 242 tracks the stylus X location,
computing the offset distance in the X direction, folsteps 206, 226 and/or 246 of FIG. 16. After those stored
lowed by step 244 which tracks the stylus in a similar 55 capacitance values are processed by the control processor 100, the identity ofthe two bus wires in the X bus 80
manner for the Y direction. In steps 242 and 244, the
control processor 100 outputs over the I/O bus 108, the
and the two bus wires in the Y bus 90 corresponding to
periodically updated horizontal and vertical position
the maximum measured capacitance can be stored in the
attributed to the stylus 60 with respect to the overlay
bus files partitioned in RAM 102 of FIG. 18. The finger
20. The program passes to step 246 which conducts 60 X location table and the finger Y location table are also
another finger touch sensing operation in a manner
shown partitioned in the RAM 102. After the operation
similar to that described for step 206. In step 246, if a
of the control processor 100 in conducting the table
finger touch is sensed, step 248 has the control proceslookup for the X location and the Y location of the
sor 100 outputting the coordinates of the finger touch
finger touch, the X and Y coordinates for the finger
on the I/O bus 108, in a manner similar to that described 65 touch can be temporarily stored in the RAM 102 before
for step 208. Note that during each cycle of the tracking
being output over the I/O bus 108. Similarly, an X bus
loop 240, horizontal and vertical coordinates representwire radiation value file and a Y bus wire radiation
ing the position attributed to the stylus 60 and horizonvalue file is provided for the temporary storage of mea-

17

4,686,332

sured values of radiation received by the stylus 60 corresponding to three bus wire pairs, as previously described. Bus file partitions, stylus X location and stylus
Y location lookup tables, and array files are provided in
the RAM 102 to facilitate the control processor 100 5
carrying out the stylus location and tracking operations.
The final computed value for the X and Y coordinates
of the stylus can then be temporarily stored in the RAM
102 before being output over the I/O bus 108, as previ10
ously described.
A utilization routine can also be included in a partition in the RAM 102, which consists of a sequence of
stored program instructions for carrying out cooperative operations between the finger touch detection and
stylus detection operations described above. For exam- 15
pIe, a utilization routine can be provided to identify
when finger touches occur in a region vertically below
the coordinates for stylus detection, with the finger
touch being in an otherwise prohibited area. This may
indicate that the user has rested the palm of his hand on 20
the surface of the overlay 20 while positioning the stylus 60 at the desired point. The utilization routine can be
selectively controlled to mask outputting the finger
touch coordinates in such a situation, if desired by the 25
operator.
The resulting combined finger touch and stylus detection system provides an enhanced man-machine interface, enabling either the sequential or simultaneous
detection of both stylus position and finger touch, 30
thereby increasing the range of applications for interactive input devices. The resulting invention has a reduced bus size and is adaptable for use with a variety of
display types having both flat and convex display surfaces. The structure of the overlay permits low cost 35
manufacture and long-term reliability.
Although specific embodiments of the invention have
been disclosed, it will be understood by those having
skill in the art that minor changes can be made to the
form and details of the specific embodiments disclosed 40
herein, without departing from the spirit and the scope
of the invention.
What is claimed is:
1. A combined finger touch and stylus detection system for use on the viewing surface of a visual device, 45
comprising:
an array of horizontal and vertical conductors arranged on the viewing surface of the visual display
device, having an I/O terminal coupled thereto, for
conducting electrical signals between said terminal 50
and the vicinity of said viewing surface;
a radiative pickup stylus, having an output terminal,
for receiving electromagnetic signals radiated from
said array;
a selection means having a switchable path connected 55
to said I/O terminal of said array and having a
control input, for connecting selected patterns of a
plurality of said horizontal and vertical conductors
to said switchable path in response to control signals applied to said control input;
60
a capacitance measuring means having an input coupled to said switchable path of said selection
means, for measuring the capacitance of selected
ones of said conductors in said array, in response to
said control signals applied to said control inputs; 65
a radiative signal source having an output coupled to
said switchable path of said selection means, for
driving selected ones of said conductors in said

18

array, in response to said control signals applied to
said control input;
a radiative signal measuring means coupled to said
radiative pickup stylus, for measuring said electromagnetic signals received by said stylus;
a control processor connected to said control input of
said selection means, for executing a sequence of
stored program instructions to sequentially output
said control signals to said selection means;
said control processor connected to said capacitance
measuring means, for receiving measured capacitance values of said conductors when said selection
means, in response to said control signals, has connected a first pattern of a plurality of said conductors in said array to said capacitance measuring
means, to detect the location of a finger touch with
respect to said viewing surface of said display device;
said control processor connected to said radiative
signal measuring means, for receiving measured
radiative signal values when said selection means,
in response to said control signals, has connected a
second pattern of a plurality of said conductors in
said array to said radiative signal source, to detect
the location of said stylus with respect to said viewing surface of said display device;
whereby, both finger touch location and stylus location with respect to said viewing surface of said
display, can be detected.
2. The apparatus of claim 1, which further comprises:
an overlay membrane upon which is mounted said
array of horizontal and vertical conductors;
a horizontal bus mounted on said overlay for interconnecting said vertical conductors to said I/O
terminal of said array;
said horizontal bus having a plurality of N bus wires
and said vertical conductors being a plurality of no
more than N(N -1)/2 vertical conductors;
said plurality of vertical conductors being arranged
with each adjacent conductor pair thereof being
connected to a unique combination of two of said
plurality of horizontal bus wires, the distance separating adjacent ones of said vertical conductors
being approximately the width of a human finger
tip;
said control processor receiving from said capacitance measuring means, said measured capacitance
values of two adjacent ones of said vertical conductors which are juxtaposed with said human
finger tip, thereby detecting the horizontal location
of said finger tip with respect to said viewing surface of said display.
3. The apparatus of claim 2, which further comprises:
said plurality of vertical conductors being further
arranged with each conductor of any group of a
subplurality of adjacent conductors thereof being
connected to a unique one of said N horizontal bus
wires;
said control processor controlling said selection
means to connect selected ones of said vertical
conductors in said group to said radiative signal
source;
said radiative pickup stylus, when proximate to said
group, receiving electromagnetic signals radiated
from said selected ones of said vertical conductors
in said group, said received signals being distinguishable by said radiative signal measuring means
over signals radiating from more distant ones of

4,686,332

19
said vertical conductors located outside of said
group in said array, thereby detecting the horizontal location of said stylus with respect to said viewing surface of said display.
4. The apparatus of claim 3, which further comprises: 5
a vertical bus mounted on said overlay for interconnecting said horizontal conductors to said I/O
terminal of said array;
said vertical bus having a plurality of N bus wires and
said horizontal conductors being a plurality of no 10
more than N(N -1)/2 horizontal conductors;
said plurality of horizontal conductors being arranged with each adjacent conductor pair thereof
being connected to a unique combination of two of
said plurality of vertical bus wires, the distance 15
separating adjacent ones of said horizontal conductors being approximately the width of a human
finger tip;
said control processor receiving from said capacitance measuring means, said measured capacitance 20
values of two adjacent ones of said horizontal conductors which are juxtaposed with said human
finger tip, thereby detecting the vertical location of
said finger tip with respect to said viewing surface
of said display.
25
5. The apparatus of claim 4, which further comprises:
said plurality of horizontal conductors being further
arranged with each conductor of any group of a
subplurality of adjacent conductors thereof being
connected to a unique one of said N vertical bus 30
wires;
said control processor controlling said selection
means to connect selected ones of said horizontal
conductors in said group to said radiative signal
35
source;
said radiative pickup stylus, when proximate to said
group, receiving electromagnetic signals· radiated
from said selected ones of said horizontal conductors in said group, said received signals being distinguishable by said radiated signal measuring 40
means over signals radiating from more distant
ones of said horizontal conductors located outside
of said group in said array, thereby detecting the
vertical location of said stylus with respect to said
viewing surface of said display.
45
6. The apparatus of claim 5, wherein N = 16 and said
subplurality is 8.
7. The apparatus of claim 5, which comprises:
said overlay membrane including an inner laminate
and an outer laminate;
50
said inner laminate including an inner substrate consisting of a sheet of polyethylene terephthalate
upon which is deposited said plurality of vertical
conductors;
said plurality of vertical conductors being composed 55
of a group consisting of indium tin oxide, gold and
silver;
said inner laminate further including an insulation
layer composed of vinyl acrylic polymer deposited
over the surface of said vertical conductors, with a 60
plurality of apertures therein selectively positioned
over each of said vertical conductors;
said horizontal bus having said N bus wires composed
of silver deposited on the surface of said insulation
layer and penetrating through selected ones of said 65
apertures in said insulation layer to make electrical
contact with selected ones of said vertical conductors;

20

said outer laminate including an outer substrate consisting of a sheet of polyethylene terephthalate
upon which is deposited said horizontal conductors
and over which is deposited a second insulation
layer including apertures therein exposing selected
ones of said horizontal conductors, and further
including said vertical bus having said N bus wires
thereof formed by silver deposited on said second
insulation layer and penetrating selected ones of
said apertures therein to make electrical contact
with selected ones of said horizontal conductors;
said inner laminate and said outer laminate being
joined by an adhesive material, forming a unitary
flexible transparent membrane.
8. The apparatus of claim 5, which further comprises:
said overlay membrane including an inner laminate
and an outer laminate;
said inner laminate including an inner substrate consisting of a sheet of polyethylene terephthalate
upon which is deposited said plurality of horizontal
conductors;
said plurality of horizontal conductors being composed of a group consisting of indium tin oxide,
gold and silver;
said inner laminate further including an insulation
layer composed of vinyl acrylic polymer deposited
over the surface of said horizontal conductors,
with a plurality of apertures therein selectively
positioned over each of said horizontal conductors;
said vertical bus having said N bus wires composed of
silver deposited on the surface of said insulation
layer and penetrating through selected ones of said
apertures in said insulation layer to make electrical
contact with selected ones of said horizontal conductors;
said outer laminate including an outer substrate consisting of a sheet of polyethylene terephthalate
upon which is deposited said vertical conductors
and over which is deposited a second insulation
layer including apertures therein exposing selected
ones of said vertical conductors, and further including said horizontal bus having said N bus wires
thereof formed by silver deposited on said second
insulation layer and penetrating selected ones of
said apertures therein to make electrical contact
with selected ones of said vertical conductors;
said inner laminate and· said outer laminate being
joined by an adhesive material, forming a unitary
flexible transparent membrane.
9. A method for detecting either finger touch or stylus location in an overlay membrane having horizontal
conductors and vertical conductors selectively connected to a capacitance measuring device, a radiative
source, and further including a stylus pickup connected
to a radiative signal measurement device for measuring
the strength of electromagnetic signals radiated from
the conductors on the overlay as picked up by the stylus, the steps comprising:
determining whether a finger touch threshold has
been exceeded;
locating the finger touch if said touch threshold is
exceeded;
determining whether a stylus threshold is exceeded, if
said touch threshold was determined not to have
been exceeded;
locating the position of the stylus if said stylus threshold has been exceeded;

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4,686,332

repeating said step of determining whether said touch
threshold has been exceeded, if said stylus threshold has not been exceeded;
whereby both finger touch and stylus detection can
be alternately carried out for said overlay membrane.
10. A method for simultaneously detecting both finger touch location and stylus location on an overlay
membrane including an array of horizontal conductors
and vertical conductors which are selectively connected to a capacitance measuring means, a signal
source, and which includes a stylus connected to a radiative pickup measurement means for measuring the
electromagnetic radiation emitted by said conductors in
said overlay and picked up by said stylus; the steps
comprising:

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cyclically detecting the remote proximity of the stylus from the overlay and detecting the finger touch
on said overlay in a proximity loop;
passing control to a stylus location step to identify the
coordinates for the location of said stylus with
respect to said overlay, followed by sensing any
possible finger touch to said overlay;
starting a tracking loop to cyclically update the coordinates for the location of said stylus with respect
to said overlay and detecting any possible finger
touch to said overlay;
repeating said tracking and said finger touch sensing
steps in said tracking loop until the detected magnitude of said signals picked up by said stylus become
less than a threshold value;
passing control to said proximity loop;
whereby coordinates for both stylus location and
finger touch location on said overlay can be output
during said locate cycle and said tracking loop.

* * * * *