null  null
United States Patent [191
Patent Number:
Adler et a1.
Date of Patent:
Aug. 22, 1989
[75] Inventors:
North?eld; Mark
Fogelson, Wilmette, both of BL; Sam
4/ 1980 Misek et a1. ....................... .. 340/365
4:346:376 8/1982
4,377,840 3/ 1983
Kaplan, Deer?eld Beach, Fla.
4,203,165 9/1983
4, 23,853 11/1986
(Z?nith'ElecItlrionics Corporation,
[21] A
l N
[22] Filed:
Jan. 20, 1987
Related [15- Application Data
Continuation-impart of Ser. No. 698,306, Feb. 5, 1985,
Pat. No. 4,700,176.
. .
4,700,176 10/1987 Adler et a1. ....................... .. 340/712
............................... "51677120395; /31/50le
. ............................
313 D‘ 510/313 R,
Japan ................................. .. 333/151
Chapman et al.,—“In-line Reflective Array Devices’
"Ultrasonics Symposium Preceedings IEEE-Sep/ 19'
78-pp. 728-733.
Judd and Thoss, “Use of Apodized Metal Grating in
Fabricating Low Cost Quartz RAG Filters”, 1980 UL
trasonics Symposium’ p‘ 343.
[58]. Field of Search ........................ .. 340/712- 178/18-
Adler “9 Desmafes, “An E¢°n°mi°a1 Touch Panel
333/150’ 151, 156’ 157’ 158’ 195,. 539, 248;
Using SAW Absorption”, Zenith ElCCtI‘OIllCS Corpora
310/313 D, 313 R
tlo n, Ultrasonics Symp osium P re c ee d in g s, v 01 . 1 , 1985 .
References Cited
'Primary Examiner-David K. Moore
Assistant Examiner-M. Fatahiyar
6/1966 Martin et a1. ....................... .. 106/47
3:707’489 12/1972 Teichmuner
Ebelling et a1.
5/ 1975 Williamson et al
'' ''
. .. .. .
.. . .. .. . .. ... . . .
termined coordinate axis includes a surface wave propa
. . . ..
gating substrate on which is disposed at least one sur
face wave transducer. An array of surface wave reflec
333/30 R
. . . . . ..
Sandy et a1 .................. .. 310/313 D
.... .. 310/313 D
.. .. . .. .. .
. . . . ..
. . . ..
3,916,099 10/1975 Hlady
.. . .. ..
A system for recognizing touch positions along a prede
tive elements directs the surface wave from the trans
ducer. The re?ective elements are composed of a frit
310/313 D
6 Claims, 7 Drawing Sheets
Aug. 22, 1989
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Aug. 22, 1989
Sheet 3 of7
US. Patent
Aug. 22, 1989
Sheet 4 of 7
US. Patent
Aug. 22, 1989
Sheet 5 of 7
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US. Patent
Aug. 22, 1989
Sheet 6 of7
US. Patent
Aug. 22, 1989
Sheet 7 of7
If?" 16
tered. A reflected wave that is detected is applied to
timing circuitry associated with the sensors, which cir
cuitry determines the geometric coordinates of the posi
tion of the ?nger or stylus. Again, as in Woo, two ar
rays, or banks, of transducers are required to create the
surface waves that propagate across the glass sheet.
U.S. Pat. No. 3,673,327—-Johnson, et al describes still
This application is a continuation-in-part of co-pend
ing application Ser. No. 698,306, ?led Feb. 5, 1985 (now
another SAW-type touch responsive panel assembly
U.S. Pat. No. 4,700,176) by Robert Adler, one of the
present inventors.
comprising a panel positioned over the faceplate of a
CRT and having a ?rst plurality of transmitters posi
tioned along a ?rst edge of the panel for generating a
This invention relates, in general, to a touch control
like plurality of Rayleigh (surface) beams that propa
gate across the surface of the panel in an X direction and
a like plurality of detectors positioned along the edge of
in particular, to a novel arrangement and system for
15 the panel opposite said ?rst edge for individually receiv
identifying the coordinates of a touch location.
ing an assigned one of said plurality of beams. In like’
Graphics display apparatus, of the type herein consid
ered, generally utilize a cathode ray tube (CRT), al
fashion, a second plurality of transmitters is positioned
though other types of display devices can be used. In a
_ along a second edge of the panel, adjacent the ?rst edge,
arrangement for use in graphics display apparatus and,
typical prior art arrangement, each of two adjacent
edges of the display surface (faceplate) is provided with
for simultaneously generating a second plurality of Ray
20 leigh wave beams that propagate across the panel in a Y
a bank of light sources arranged to develop a cluster of
parallel light paths which extend across the faceplate,
the clusters intersecting, preferably at right angles to
form a grid pattern of light paths overlying the display
direction, perpendicular to the X direction. A like sec
ond plurality of detectors is positioned along the edge
of the panel opposite said second edge for receiving an
assigned one of said second plurality of beams. Accord
surface. Like banks of light detectors ?ank those sides 25 ingly, to establish this X-Y grid of Wave beams, a trans
of the faceplate opposite the banks of light sources.
mitter is required for each wave beam and a separate
In practice, a particular graphic is delivered for dis
detector is required for each such transmitter.
play by a controller in response to an operator’s com—
Each transmitter, upon actuation, launches a beam of
mand, which command can take the form of a pointing
Rayleigh surface waves along the surface of the panel.
to one area of the faceplate. This pointing serves to
Thereafter, when a ?nger or other object is pressed
interrupt one or more of the light beams, which inter
against the panel, acoustical wave energy is absorbed,
ruption causes the beam’s assigned light detector to
thereby interrupting its transmission to its assigned de
develop a signal which is applied to the controller to
The absence or reduction of the normal signal at
select a particular graphic. U.S. Pat. No. 3,775,560, for
a speci?c detector constitutes a touch indication which
example, exempli?es this type of control for a graphics
display apparatus. A touch control arrangement of the
type adverted to above tends to be rather costly since a
separate light sensor is employed for each light source.
It is known to use surface acoustic wave'(SAW)
energy for touch control. Prior art U.S. Pat. No.
3,134,099-Woo teaches an arrangement in which a
plurality of piezoelectric transducers, electrically con
nected in parallel, is disposed along each of two adja
cent edges of a sheet of glass. The transducers are cou
pled to the sheet and, in response to a control signal,
create surface waves which propagate across the sur
face of the glass sheet. A writing pen, embodying a
piezoelectric component, is placed in contact with the '
glass sheet to sense a propagating disturbance and then
issue an appropriate signal to a control unit which mea
sures the elapsed time interval between the time the
control signal was applied to the transducer that initi
ated the disturbance and the time the signal was re
is applied to a computer.
However, a principal drawback of the Johnson et a1
touch control system like that of its optical counterpart,
resides in the requirement of a multiplicity of transmit
ters and detectors to establish the intersecting wave
energy paths that form the grid overlying the panel.
The mechanical considerations, and cost, involved in
the practice of utilizing dual pluralities of transmitters
and detectors, all of which must be separately wired,
are obvious shortcomings.
Other patents in the touch control art are set forth
U.S. Pat. Nos. 3,775,560
ceived by the pen. It is of signi?cance that, in the Woo
arrangement, a plurality of piezoelectric transducers is 55
Additionally, art in the ?eld of surface acoustic
required for each of two adjacent sides of the glass
waves which was considered included:
panel. Further, the Woo system requires the use of a
U.S. Pat. Nos. 3,883,831
special touch stylus capable of sensing surface acoustic
waves traveling across the panel.
“Use of Apodized Metal Gratings in Fabricating
U.S. Pat. No. 3,653,03l—-Hlady, et al is addressed to 60
Low Cost Quartz RAC Filters” by G. W. Judd and J.
a touch sensitive position encoder also employing elas
L. Thoss. Proceedings of the IEEE 1980 Ultrasonics
tic surface wave generating transducers positioned
along the edges of a sheet of transparent glass. The
transducers function as radiators, as well as sensors, and
thus serve to launch surface waves across the glass 65
sheet, as well as to receive such waves. In operation, a
?nger or stylus placed at a particular position on the
glass sheet serves to reflect the surface waves encoun
Symposium, p. 343.
It is therefore a general object of 'the invention to
provide an improved touch responsive graphics display
It is a speci?c object of the invention to provide an
improved touch responsive arrangement for, or for use
with, a graphics display CRT.
FIG. 15 depicts a variation of the waveform shown in
FIG. 14;
FIG. 16 is a schematic representation of another em
It is also an object of the invention to provide a touch
bodiment of the invention featuring an angular coordi
nate system;
responsive arrangement for use with graphics display
apparatus which imposes but minimal limitations on
cabinet and escutcheon designs.
It is another object of the invention to provide such a
touch responsive arrangement characterized by mini
mal mechanical and electrical complexity and reduced
FIG. 17 is a cross-section of an idealized pro?le of an
element of a re?ective grating;
FIG. 18 is a profile of a prior art re?ective grating
element; and
FIG. 19 is a pro?le of a re?ective grating element to
cost of manufacture.
which a nucleation-accelerating agent has been added.
FIG. 1 shows a graphics display apparatus 10 com
prising a graphics controller 12 and a display device 14
having a display surface 16. A CRT may be employed
The features of the present invention believed to be
novel are set forth with particularity in the appended
claims. The invention together with further objects and
to display graphics and the subject invention will be
described in that environment. However, it is to be
advantages thereof, may best be understood by refer
ence to the following description taken in conjunction
appreciated that the invention is readily applicable to
other display devices,'e.g., electroluminescent or liquid
with the accompanying drawings, in the several ?gures
crystal devices, or even displays as simple as an elevator
of which like reference numerals identify like elements,
number display, any of which can be employed in lieu
of a CRT. In some applications, a separate panel is
disposed over the faceplate of the display device.
The faceplate, or panel, is commonly designated a
“touch control panel” since graphics, or other informa
tion may be ordered up for display from controller 12 in
response to an operator’s command which can take the
and in which:
FIG. 1 illustrates, partially in schematic form, a
graphics display apparatus embodying the invention;
FIG. 2 is a plan view of the FIG. I touch responsive
display panel depicting, in some detail, re?ective grat
ing construction and placement;
FIG. 3 is a graphical plot representative of received
form of a touching of a particular area of a menu associ
surface acoustic wave energy traversing one coordinate
ated with the touch control panel. This display surface
of the touch panel of FIG. 2;
30 16, whether it can be a CRT faceplate or a separate
FIG. 4 is a graphical plot representative of received
panel, constitutes a substrate the surface of which is
surface acoustic wave energy traversing a second, or
capable of propagating surface acoustic waves. As will
be shown, the act of touching serves to interrupt or
reduce wave energy directed along one or more paths
thogonal, coordinate of the touch panel of FIG. 2;
FIG. 5 is a schematic representation of a reflection
grating and a series of reflected wave components de
veloped by that grating;
that form a grid overlying the panel. Detection and
analysis of such interruption serves to identify the X, Y,
FIG. 6 illustrates the waveform developed by an
output transducer responding to the re?ected wave
or other coordinates of the touched area, which infor
re?ected wave components;
FIG. 8 is a schematic representation of a rectified
predetermined sequence so that when a perturbation, or
interruption of acoustic wave energy is detected, con
verted to an electrical signal and fed back to the com
mation, in turn, is determinative of the graphics to be
components shown in FIG. 2;
delivered up for display or other response of the device.
FIG. 7 illustrates the waveform developed by an 40 To this end, apparatus 10 further includes a computer
output transducer responding to an elongated series of
22 for rendering an interface circuit 24 operative in a
version of the output signal of an output transducer
employed in a touch panel display apparatus con 45 puter, via interface circuit 24, the location of the inter
structed in accordance with the invention.
FIG. 9 is a schematic representation of a re?ective
array in which the pattern of elements results from
ruption is identi?able by the computer. Graphics con
troller 12 comprises the drive electronics for CRT 14
and, to that end, serves to amplify and otherwise condi
“finger withdrawal”;
tion the output of computer 22. To achieve its functions,
the computer comprises a clock (source of timing sig
FIG. 10 is a schematic representation of a re?ective
array in which individual elements are fragmented in a
nals), a source(s) of video information, as well as
sources of horizontal and vertical sync pulses. The out
patterned fashion;
FIG. 10A is a schematic representation of a re?ective
put of controller 12 is coupled to the control electrodes
array in which the length of individual elements in
of CRT 14, as well as to the CRT’s de?ection windings,
creases in the direction away from the adjoining trans 55 to display, under the direction of computer 22, selected
graphics. Accordingly, when the computer identifies
FIG. 11 is a schematic representation of a touch panel
arrangement in which a single device is utilized as the
the location, or address, of wave interruptions, it will
then output the appropriate information to controller 12
input and output transducers;
to change the video display to graphics associated with
FIG. 12 is a schematic representation of a touch panel 60 the address touched by the operator.
arrangement utilizing an output transducer coextensive
As shown in FIG. 1, interface circuit 24 has input
with one coordinate of the panel;
terminals coupled, via a buss 30, to receiver transducers
FIG. 13 is a schematic representation of a touch panel
R1, R2 and output terminals coupled to transmitter
arrangement in which the surface wave re?ective grat
transducers T1, T2 via the buss 32. Circuit 24 has addi
ing comprises discrete groups of re?ective elements;
FIG. 14 depicts the pulse-type waveform developed
tional input and output terminals coupled to computer
22 for interacting therewith. Circuit 24, in response to
by an output transducer responding to the burst compo
timing signals from computer 22, outputs ?ring signals
nents developed by the FIG. 13 embodiment;
that stimulate transducers T1, T2 in a timed sequence so
that the location of a subsequent interruption of a sur
face wave is identi?able.
ell-enn which are disposed along path P2 with the ele
ments effectively arranged at like angles of incidence to
Input transducers T1, T2, which are more particu
the axis of path P2. Grating G3 serves to extract from
the surface wave launched by transducer T2 a multi
larly described below, are mounted upon substrate sur
face 16 adjacent to edges 18 and 20, respectively, of
5 plicity of wave burst components and to direct such
FIG. 2. A source 25 in interface circuit 24 serves to
wave burst components across substrate surface 16
apply input signals S1, S2, via buss 32, to respective
transducers T1, T2, which transducers, in response
degree angle to the axis of path P2.
along a multiplicity of paths ph each disposed at a 90
A fourth re?ective grating G4, comprising an array
of reflective elements e'll-e’nn is disposed along path
P4,each element being arranged at a 45 degree angle to
the longitudinal axis of path P4. The re?ective elements
of grating G4 intercept the wave components directed
thereto by the elements of grating G3 along the paths
thereto, individually launch a burst of acoustic surface
waves along ?rst and second paths P1, P2, respectively
on surface 16.
Also as shown in FIG. 2, ?rst and second output
transducers R1, R2, are mounted upon substrate surface
16 adjacent to respective edges 18, 20 that is, the edges
receipt of the surface waves launched by their associ
ph and redirect these intercepted wave burst compo
nents along path P4 to receiving transducer R2.
Since transducers T1, T2 additionally launch surface
ated input transducers develop respective output signals
acoustic waves along paths P1, P2 in directions opposite
close to their associated input transducer T1, T2. In a
manner to‘be detailed below, transducers R1, R2, upon
from their respective adjoining gratings G1, G3, it is
S3, S4 which, upon analysis, will exhibit a characteristic
of thelaunched surface wave, e.g. a change in ampli 20 desirable to provide means for arresting such wave
energy. Accordingly, a pair of absorbers 33, 35, which
tude, attributable to a perturbation of a received surface
can be formed of a soft epoxy, are mounted upon the
wave burst.
display surface immediately behind respective transduc
A ?rst re?ective grating G1 comprising an array of
re?ective elements el-en is disposed along path P1 with
each of the aforesaid elements effectively arranged,
preferably, at like angles of incidence to the longitudinal
axis of path P1. Desirably, the angles of incidence'of the
ers T1 and T2.
In the manner just described, and as depicted in FIG.
2, display surface 16 is now provided with an overlying
grid comprising a multiplicity of intersecting paths of
re?ection elements, relative to the axis of path P1, are
acoustic surface wave bursts which surface waves are
approximately 45 degrees. Additionally, the longitudi
con?ned to predetermined paths, one series ph being
disposed parallel to what may be termed the horizontal
or major axis of display surface 16 while a second, inter
secting series of paths pv are disposed parallel to the
1 and 2.
vertical or minor axis of the display surface. In this
Re?ective elements el-en serve to extract from the
fashion intersecting wave energy paths traverse the
initially launched surface wave burst a multiplicity of
wave components and to direct such wave burst com 35 surface of the display device, forming a grid that over
lies display surface 16.
ponents across substrate surface 16 along a like multi
As described above, means, in the form of interface
plicity of paths pv each disposed at an angle to the axis
circuit 24 and buss 32, are coupled to the input transduc
of path P1. As depicted in FIGS. 1 and 2, these multi
ers T1, T2 for initiating the launching of bursts of sur
plicities of paths are each disposed at 90 degrees to the
nal axis of path P1 is preferably disposed parallel to the
upper edge of substrate surface 16, as viewed in FIGS.
axis of path P1.
face waves along paths P1, P2. The application of sig
A second reflective grating G2 likewise comprises an
array of re?ective elements 3’l-e’n which are disposed
along path P3 and are effectively arranged at like angles
,of incidence to the longitudinal ais of path P3 for inter
nals S1, S2 to transducers T1, T2 serve to generate and
launch across surface 16 elastic (ultrasonic) surface
waves having a substantially planar wavefront with
uniform amplitude and phase along lines parallel to the
cepting the wave components extracted from the wave 45 initiating transducer. Transducers T1, T2, (as well as R1
and R2) typically, are piezoelectric transducers com
traversing path P1 and directed across substrate surface
prised of a lead zirconate-titanate ceramic mounted
16 along the paths pv. Grating G2 intercepts the wave
upon a prism of lower velocity material, e.g., Lucite,
burst components arriving along paths pv and redirects
them along path P3 toward receiving transducer R1
which effects-an ef?cient electro-mechanical coupling
which converts the wave energy in a received burst to
to substrate surface 16.
an electrical output signal S3. In a fashion complemen
tary to that of the ?rst re?ective grating G1, the ele
ments of grating G2 are disposed at 45 degrees to the
longitudinal axis of path P3 to facilitate interception and
redirecting of wave components arriving from grating
The above-described transducer pair T1, R1 and
gratings G1, G2 serve to establish one portion of a grid
The generated surface waves launched along paths
P1, P2 are eventually received by transducers R1, R2,
respectively, and converted to electrical signals S3, S4.
Means comprising a signal processing circuit 23, in
cluded in interface circuit 24, see FIG. 1, is coupled to
the outputs of receiving transducers R1, R2 for deter
mining, by an analysis based on the transit time of the
perturbed surface wave burst, which of paths ph, pv the
touch-perturbed wave traversed and thereby establish
of surface wave burst paths pv which are disposed
across substrate surface 16. A second portion of that 60 the location of the touch along two coordinates of the
display surface. In one coordinate system, for example,
grid is established by a second pair of transducers T2,
in order to identify the Xcoordinate for the location of
R2 and associated gratings G3, G4. In a manner similar
the path of a perturbed wave burst along the horizontal
to that described above, transducer T2, in response to a
axis, as viewed in FIG. 2, the determining means is
?ring signal S2 from source 25 in interface circuit 24,
launches a burst of acoustic surface waves along the 65 arranged to make a time analysis of the surface wave
burst received by transducer R1. To this end, the deter
mining means analysis commences at the instant input
signal S1 is applied to transducer T1 to launch a surface
grating G3 comprises an array of re?ective element
path P2, which path is disposed perpendicular to the
previously described paths P1, P3. The third re?ective
wave. On the time scale of FIG. 3 there is plotted the
quently received by R1, occurred approximately 112
earliest time an acoustic wave burst from transmitter T1
could arrive at receiver R1.
T1 launched the surface wave under consideration. This
microseconds (2+2+64+22+22) after the transmitter
Assuming that the dimensions of the grid overlying
112 microsecond interval is analyzed by computer 22
display surface 16 are approximately 8"X l1", and as
suming further that the transit time required for a sur
which informs the controller 12 that a perturbation was
detected by receiver R1 at a particular instant in the
face wave burst to reach the ?rst reflective element el
time domain.
Preferably, a short time later, a surface wave burst is
on path P1 is approximately 2 microseconds, as is the
transit time required for the surface wave burst to travel
launched by transmitter T2 and re?ected by gratings
to receiver R1 from element e'l; to this is added the 0 G3 and G4 to return the components of that wave to
transit time of the surface wave from re?ective element
receiver R2. In the manner described above with refer
el across the display surface 16 to element en, which is
ence to a perturbation detected by R1, the surface wave
approximately 6 microseconds. Accordingly, the detec
tor will ignore any disturbance arriving within the ?rst
64 microseconds immediately following the triggering
of transmitter T1. Assuming for the moment, that no
components now traversing a path ph parallel to the
major axis of the display surface are detected by R2
which establishes, in like fashion, the occurrence and
time when the aforementioned perturbation of the
disturbance or perturbation of the instant surface wave -
wave, manifested in FIG. 4 as dip D2, was experienced
launched by T1 is experienced, the output of transducer
R2 might exhibit the solid line response shown in FIG.
3. Depicted therein is a waveform having a relatively
along the Y-axis. Applying this time-related information
to that developed relative to the other axis, the com
puter informs controller 12 of the coordinates of the
constant amplitude extending for approximately 176
perturbation (touching A1) so that the controller may
microseconds. This response is established by virtue of
the fact that for a period commencing at to surface
wave energy is continually received by the detector R1
for 176 microseconds that is until time tn. The 176 mi
deliver for display upon the CRT screen the particular
croseconds interval is the approximate time required for
a surface wave to traverse the entire length of reflective
grating G1 and return along the length of reflective
grating G2. In the absence of a perturbation the output
of receiver transducer R2, when analyzed by interface
circuit 24, will supply a signal to computer 24 which is
indicative of the fact that an uninterrupted burst of
graphics associated or assigned to the location at which '
the touching occurred.
It is recognized that simultaneous operations to iden
tify both coordinates are possible, but the preferred
mode of operation is to alternate between the two. The
latter practice eliminates crosstalk problems and makes
it possible to economize by switching certain circuit
elements (e.'g. a tuned ampli?er) between coordinate
identifying channels, instead of duplicating such ele
surface waves traversed substrate surface 16 without
interference. The computer relays this information to
In an embodiment successfully reduced to practice
the above-described gratings 61-64 were formed by
controller 12 which, in turn, maintains the graphics 35 resort to a silk-screening technique in which a frit (sol
display on the CRT undisturbed.
der glass) material, in accordance with one aspect of
Assuming now that an operator wished to select a
this invention, is substituted for the conventional ink in
graphic other than that being displayed. A menu, such
the otherwise well known printing process. Speci?
as a chart or other type of directory, would indicate
cally, a tensioned cloth or metal mesh screen is impreg
which particular area of display surface 16, should be
nated with photo-resist and photo-exposed to form a
touched to call up the desired graphic. Accordingly,
assuming that the particular area is that designated Al in
FIG. 2, the operator then inserts his ?nger into the grid
of intersecting surface waves by touching the display
negative of the desired reflector grating pattern. The
photo-resist is insolubilized by such exposure. Subse
quently the unexposed photo-resist material is dissolved
and washed away, and a paste of high density glass frit
surface at Al, which action causes a portion of the 45 in an organic binder material is printed onto the display
acoustic surface wave energy traversing the touched
surface 16 through the resist-free areas of the screen to
area to be absorbed. This act of touching is best ex
form a pattern corresponding to the gratings G1—G4. In
plained, and manifested, by reference again to FIG. 3
order to closely control the thickness, uniformity and
which depicts the effect upon the output waveform of
line width of the gratings, the frit is in the form of pow
R1 attributable to a perturbation of the surface wave
der particles milled to submicron size with a density of
traversing the display surface in the vicinity of area Al.
about 6 grams per cc. These frit particles are then mixed
This effect is manifested in the waveform as a dip D1
with an approximately 10% nitrocellulose-terpineol
along the time axis which corresponds to the point
solution to form a viscuous paste. This frit paste, when
where the operator touched the panel. Let us assume
printed, is in the form of a somewhat viscous liquid. The
that the point of touch occurred approximately one
latter must then be baked at temperatures of 400-500
fourth of the distance along the major axis of the display
surface commencing from the left side, as viewed in
FIG. 2. As previously noted, it was assumed that the
frit melts and then devitrifles, forming a solid mass and
becoming bonded to the display surface 16. This general
time entailed for a surface wave to travel the length of
procedure is set forth in an article entitled “An Eco
grating G1 was 88 microseconds. One-fourth of that
time would be 22 microseconds. Adding to that number
the 64 microseconds required for the wave to traverse
bert Adler and Peter J. Desmares, published in the 1985
degrees C. until the organic binder vaporizes and the
nomical Touch Panel Using SAW Absorption” by Ro
Ultrasonics Symposium Proceedings, Vol. 1.
the paths parallel to the minor axis of the surface, the 22
It has been found, however, that conventional high
microseconds entailed in traversing a corresponding
density frit formulations (which have high lead-concen
portion of array G2, and finally adding the 4 microsec 65 trations) are subject to certain disadvantages when used
onds (2+2) initial and terminal transit times, the detec
for printing the gratings Gl-G4. The viscocity of such
tor, output waveform would indicate that a perturba
formulations is not great enough to permit the printed
tion of the wave burst transmitted by T1 and subse
lines el, etc. to hold a sharp edge during the time that
the frit material is being baked.‘ Consequently, during
that period of time each of the frit lines el, etc. tends to
slump, spread, and ?ow; changing the shape of its
sound-re?ecting edge from a nearly vertical wall to a
gradual slope. This change of shape adversely affects
the sonic re?ectivity of the gratings G1-G4, and thus
impairs the performance of the SAW touch-screen sys
tem. Speci?cally, if the edges of the lines e1, etc. are not
sharp, the sonic re?ections therefrom are more diffuse,
and the strength of the re?ections is less because more
~ of the sound energy is lost.
One aspect of this invention, which was developed to
overcome the foregoing problem, is the addition of a
nucleation-accelerating agent to the frit composition to
enable the lines e1, etc. to hold a sharp edge. In order for
such an additive to retain its nucleation-accelerating
properties during the baking operation, it should be
refractory material. For example, if about 10% by
weight of zirconium oxide (ZrOg) powder is added to
The effect of adding the zirconium oxide to acceler
ate nucleation and to reduce ?ow during the frit heating
cycle is illustrated in FIGS. 17—19. FIG. 17 shows an
ideally sharp rectangular pro?le for each of the grating
elements, el etc. Such a pro?le, however, cannot be
achieved in practice. If conventional frit compositions
are used, viscous ?ow during the bake operation causes
the grating elements to slump into a gradual pro?le of
the kind seen in FIG. 18. A much better pro?le as illus
trated in FIG. 19 and this is achieved by means of the
10% ZrOZ additive. There is much less viscous ?ow
the frit composition to increase its viscosity, it enables 20 during bake, and therefore less slumping, resulting in
the much more nearly rectangular pro?le of FIG. 19.
the grating lines to hold a sharp edge during the baking
operation until the frit crystallizes and hardens. After
The frit re?ector grating was deposited in the pattern
that, slumping, spreading and ?owing can no longer
depicted in FIG. 2. More particularly, the actual con?g
uration and spacing of the grating element pattern was
The addition of 10% zirconium oxide to a frit compo 25 computer-generated utulizing the ?nger-withdrawal
sition is not in itself new. See Martin, US. Pat. No.
method. Consider ?rst a basic re?ective linear array
3,258,350, in which such an additive is disclosed, and its
comprising a multiplicity of surface wave re?ecting
nucleation-accelerating effects recognized. (See also
?ngers (elements) of equal width, equally spaced and
Mason, US. Pat. No. 3,707,489 and Nair, US. Pat. No.
4,377,840). The Martin patent, however, leads the art
away from the teaching of the present invention, be
collectively disposed at 45 degrees to the longitudinal
axis of the path they de?ne. Desirably, the spacing, or
cause Martin used zirconium oxide as an additive only
to modify the coef?cient of thermal expansion of a frit
composition, and regarded the concomitant increase in
pitch, between adjacent elements should be one wave
length of the frequency of the burst of acoustic waves
launched by the transmitting transducer. An acoustic
wave traversing such an array in which the re?ecting
nucleation as an undesirable side effect. In any event,
?ngers are uniformly spaced will experience an expo
the use of a zirconium-oxide-impregnated frit material
in the speci?c environment of a SAW touch-screen goes
nential attenuation of power with distance so that little,
far beyond the disclosure of the Martin patent.
Studies of grating lines formed with a 10% zirconi
um-oxide-impregnated frit composition according to
this invention have shown that the pro?les of such lines
are substantially sharper and the echoes therefrom sub
if any, acoustic wave energy is available for re?ection at
the terminus of the array. Moreover, a uniform array of
the type adverted to results, of necessity, in exponen
tially decreasing power density with distance in the
re?ected acoustic wave components directed across the
display surface. In other words, the power density of
the initially reflected wave components will be signi?
present SAW touch-screen system. The zirconium
cantly greater than that of subsequently re?ected wave
oxide additive may also increase the density of the frit 45 components. Desirably, the re?ected wave components
material, and the denser the material of the grating lines
traversing the display surface should be characterized
e1, etc. is, the less height they must have to return an
by a substantially constant power density, as graphi
echo of a given amplitude.
cally depicted in FIGS. 3 and 4, otherwise those plots
The following is a practical example of a method of
would depict an exponentially decreasing amplitude.
printing a SAW reflection grating in accordance with
The desired constant power density of the re?ected
this invention:
waves is achieved, in an execution that has been re
Step 1. Owens Illinois CV 810 HD frit powder is
duced to practice, by a patterned deletion of a grating’s
vibromilled to achieve approximately 0.5 micron
re?ective elements in which the percentage of deleted
average particle size.
elements decreases gradually from the launch point to
Step 2. A paste containing 100 parts by weight of the
the terminus of the grating. This results in a progres
milled frit, 35 parts by weight of 10% nitrocellu
stantially stronger, thus improving the operation of the
lose terpiniol binder, and 10 parts by weight of
sively increasing coef?cient of re?ectivity culminating
zirconium oxide (ZrO2) powder was made by mill
ing or roller-milling to achieve homogeneity.
Step 3. Using that paste as an ink, the array pattern
execution was designed from an initial array of approxi
was printed on a glass substrate by the silk-screen
ing method using a 260 mesh screen.
Step 4. The glass with the array pattern was baked at
a peak temperature of 430 deg. C. for 20 minutes.
in the sought for constant power density.
A re?ective grating tailored for the above-mentioned
mately 300 equally spaced elements having a pitch (in
the direction of wave propagation) of one wavelength
of a four MHz acoustic wave. In practice elements are
selectively deleted to the end that the spacing between
The ?nal frit pattern coating thickness after baking 65 remaining adjacent elements in the grating is a multiple
was approximately 0.2 mils. This thickness can be
of the above-mentioned one wavelength. In the subject
changed by adjusting the viscosity of the frit paste
execution array elements are selectively deleted in ac
through varying the binder content as follows:
cordance with the following formula:
on a separate strip for other reasons also, such as ease or
economy of manufacture.
In a broad sense, the invention may also be thought of
as an absorption ranging system, quite unlike the above
In the above expression, P is equal to the density of
elements at coordinate x, where x is the distance mea
sured from the far end of the array back toward the
launch end. When x equals zero, element density is
unity, which is the case for a uniform array with no
elements deleted. C and L are constants, the values of
which are determined by recourse to experimental data
and depend upon the material properties of the display
panel and the re?ective elements, the length, width and
thickness of the re?ective elements, etc. The resulting
grating comprised an array of approximately 130 ele
ments having a pattern determined by the above for
discussed re?ection-type ranging system shown in the
prior art Patent No. 3,653,031. In the present invention,
the absence of wave energy or the presence of wave,
energy at a reduced level, as results when a ?nger, or a
stylus reasonably capable of absorbing acoustic surface
wave energy, damps the amplitude of a surface wave
burst propagating through the region of the touch, is
sensed and the timing of that information is utilized to
determine which of the plurality of burst propagation
paths has been perturbed, and thus the location of the
touch. One will note that in the preferred embodiment,
the time required for the surface wave burst compo
nents to propagate across the panel is constant for all
burst paths. However, the time required for the surface
wave burst launched by the input transducer to propa
mula and in which individual elements were 07" long 20 gate to the point at which it is again redirected across
and 0.011" wide.
the panel, and from the point at which it is redirected to
Having described a preferred embodiment of the
the output transducer, varies along the coordinate axis
along which the touch may occur. It is this varying
invention, a number of the principles underlying the
invention and variants of the preferred embodiment will
distance, and the surface wave propagation time associ
be discussed. Whereas the preferred embodiment of the 25 ated therewith, which is used in the present invention to
locate the position of a touch along the coordinate axis.
invention is illustrated as providing for touch position
Unlike prior art systems which have a ?xed number
detection in Cartesian coordinates, it should be under
of emitters along one side of the touch panel and a
stood that the principles of the invention are applicable
corresponding ?xed number of detectors along the op
in devices having angular or other coordinate systems,
30 posed side thereof and which detect the position of a
or in devices having a single coordinate axis.
touch by determining which of the emitter-detector
The preferred embodiment has been described in the
pairs have been triggered, the present invention teaches
context of a system for launching a burst of surface
the formation of a continuous succession of surface
waves into a re?ective array or grating from which is
wave bursts which sweep across the panel and develop
derived a plurality of burst components. The array
at the output an analog output signal. With the present
redirects these components across the display surface.
invention, a touch panel system designer has a free
In a broader sense, the invention may be.thought of as
choice, by detection circuit design, to pick touch panel
surface acoustic wave scanning means including input
speci?cations conforming to the speci?cations of a de
surface wave transducer means coupled to a surface
vice driven by the display-a computer, for exam
wave propagating substrate for scanning the surface in
the direction of the coordinate axis with a timed succes
sion of surface wave bursts directed in substantially
parallel paths across the surface transversely to the said
coordinate axis. The plurality of paths are respectively
associated with different positions along the coordinate
axis of the display surface. As the touch position infor
mation is developed by timing the surface wave burst
component which is perturbed, the starting time of each
of the succession of surface wave bursts which are di
rected across the panel must be carefully controlled. In
the aforesaid preferred embodiment, the timing is inher
ent in the propagation velocity of the surface wave
burst as it travels through the re?ective grating. Other
embodiments are contemplated wherein the launching
of the bursts of surface waves or wave components 55
along parallel paths across the panel is determined by
other than the natural propagation velocity of surface
ple-without making mechanical changes. This subject
will be treated at length below.
FIG. 5 will further an understanding of certain prin
ciples underlying the present invention, and certain
desired optimizations. Whereas other means may be
devised for redirecting a burst of surface waves
launched by the input transducer across the display
surface, as in the preferred embodiment described
above, FIG. 5 shows a reflective grating 40 for this
purpose. The grating is shown as comprising re?ective
elements E1, E2, E3, E4, and E5 arranged in the direc
tion of the touch coordinate axis 41. In practice, the
grating would comprise additional elements as shown in
FIG. 2, however, in the interest of clarity of illustration,
only ?ve elements are shown. An input signal 42 for
application to the schematically represented input trans
ducer 44 is shown as comprising a ?ve cycle signal
burst, here depicted as a sine wave having cycles C1,
waves on the display surface. For example, in the em
C2, C3, C4 and C5.
bodiment wherein a re?ective array such as is shown in
_ Application of input signal 42 to the input transducer
FIG. 2 is used to launch the surface wave burst compo 60 44 results in a burst of equal-amplitude surface waves
nents across the panel, the re?ective array may be
from the transducer 44. The wavelength of the cycles
formed on a separate strip composed of a material hav
C1-C5 is selected to be equal to the period of the grat
ing a different wave propagation velocity, such as a
ing 40. The ?rst cycle C1 of signal 42 generates a ?rst
different glass or a metal, which is adhered to the dis
surface wave which is partially re?ected from the ?rst
play surface. Care must be taken to insure an efficient 65 element E1 of grating 40, here shown by way of exam
transition of the waves from the reflective grating onto
ple as being oriented at 45 degrees to axis 41. The re
the display surface, as by feathering the interfacing edge
?ected surface wave propagates at 90 degrees to the
of the strip. The wave re?ective array may be formed
direction of travel of the launched surface wave. The
represents the type of recti?ed output which would
result—namely an output signal having a dip 51 associ
ated with the perturbation which has a poorly de?ned
bottom and thus poor touch resolution. Conversely, if
the input burst of surface waves (the duration of the
?rst re?ected surface wave is labeled in FIG. 5 as C1El,
signifying the ?rst surface wave developed by input
signal cycle Cl, as re?ected from grating element E1.
The same ?rst wave re?ected from grating element
E2 is shown in FIG. 5 at C1E2. The surface waves
re?ected from elements E3~E5 are labeled C1E3, C1E4
input signal 42) is signi?cantly shorter than the opti
and C1E5, respectively. Similarly, the second cycle C2
mum length, a weak signal will result such as shown in
FIG. 8 at 52, with lower signal-to-noise ratio and thus a
of the input signal 42 develops a second surface wave
signal whose reliability and touch resolution is poor. It
which lags the first surface wave by one period, produc
ing a second pattern of surface waves of exactly the O is the signal-to-noise ratio of the signal developed at the
output transducer which determines the limiting touch
same con?guration as the pattern of waves produced by
resolution in the present system.
the ?rst cycle C1 of the input signal, but lagging in time
By way of example, the spacing of the grating ele
by one cycle. Similarly, input signal cycles C3-C5 pro
duce three more surface wave patterns. Thus, the appli
cation of input signal 42 results in a burst of surface
waves from the input transducer 44 which propagate
ments and the wavelength of the surface waves which
make up the surface wave bursts may, for example, be
through the re?ective grating 40. A plurality of surface
burst length in accordance with the present invention,
wave burst components are derived from the grating 40
one factor which must be taken into account is the
distance the surface waves will travel across the panel
thirty mils (0.030"). In determining the optimum input
which propagate across the display surface. As used
herein, ClEl, C2E1, C3E1, C4E1, C5E1 constitutes
without signi?cant spreading due to diffraction effects.
one burst component. Another would be C1E2, C2E2,
C3E2, C4E2, C5E2. It is preferred that the burst com
As a rule of thumb, a surface wave will propagate from
its launching transducer a distance roughly equal to the
square of the width of the transducer, measured in num
ponents be heavily overlapped to produce at the output
ber of wavelengths, without excessive spreading. By
a smooth analog signal, as will be discussed at length
25 way of example, to launch a surface wave across a
?fteen inch wide panel, the input transducer should be
The output developed by an output transducer 45,
about twenty-four wavelengths wide. Assuming a thirty
positioned as shown in FIG. 5, will take the form shown
mil wavelength, the surface wave burst will travel ap
schematically in FIG. 6 wherein the amplitude of the
proximately 576 wavelengths or about seventeen inches
detected signal will rise to a peak and then decay to
before signi?cant spreading occurs. In practice, how
zero. This can be easily understood from FIG. 5
ever, it has been found that for a ?fteen inch panel
wherein it can be seen that the burst of surface waves is
width, the transducer need only be about 16 wave
led by single wave C1E1, which is followed by a double
lengths (0.48 inches) wide; this favorable ?nding is ex
wave C1E2, C2E1 in turn followed by a triple wave,
and so on. After the peak is reached, the number of . plained by the simultaneous action of two gratings (e.g.
G1 and G2) in determining the wave paths across the
surface waves which add at the output progressively
display surface. Now, if the surface wave velocity on
decreases until the burst has passed and the detected
the display surface is 120 mil per microsecond (:3000
wave energy falls to zero.
It has been discovered that if signal/noise ratio is
meter/second), then w/c equals 4 microseconds, and
consequently the optimum burst duration is between 4
considered, there exists an optimum relationship of
and 8 microseconds, corresponding to the range of 16 to
surface wave burst length to input transducer width (or
32 cycles. The frequency corresponding to these ?g
more precisely, width of gratings G1, G2 etc.). Speci?
cally, in a preferred execution of the present invention,
the duration of the input surface wave burst (“T”)
emerging from the input transducer should be in the
ures, determined by the quotient of velocity c and
wavelength, equals 4 Megahertz.
It is important to note that with bursts as long as 32
range of 1.0 w/c to 2.0 w/c where “w” is the above 45
cycles passing through the grating, maintaining the
mentioned width and “c” is the velocity of propagation
correct relationship between the transmitted frequency
and the mutual spacing S of the re?ecting strips is im
portant. In the embodiment described so far, the strips
of surface waves on the conducting substrate.
The implications of the above can be better under
stood by reference to FIG. 8 which is a highly sche
matic representation of a recti?ed version of the wave
' form of a signal which might be produced at the output
are oriented at 45 degrees to the direction of the inci
dent wave, and the proper spacing for this case is one
wavelength or an integral number of wavelengths; the
correct frequency is f=C/S or an integral multiple
thereof, and the transmitted frequency should be very
close to the theoretical value; for shorter bursts, i.e.
of the output transducer in touch panel display appara
tus according to the present invention. FIG. 8 is a sche
matic illustration corresponding to FIG. 3 or 4 dis
those containing fewer cycles, frequency tolerance is
proportionately wider. Power reflectivity, to be de?ned
cussed above. Using an optimized con?guration, as
described above, an output signal 48 results in which the
amplitude dip 49 resulting from a damping of a burst of
surface waves in a particular burst path has substantial
amplitude. The signal to noise ratio of the signal 48 is
adequate. The clip 49 in the waveform of the recti?ed
signal 48 corresponding to the detected damping of the
later, must also be determined at the correct frequency.
For the same reason, it is important that the chosen
value of S be accurately maintained constant along the
entire grating, with the exception that integral multiples
of S are allowed.
wave has a well-de?ned bottom which can be located
As intimated above, the present invention is distin~
with extreme precision, as will be discussed below. If
the length of the input burst of surface waves is substan
guished from other touch panel systems, in its preferred
form, in its particular utilization of an analog output
tially above the optimum range, the output transducer
will develop an output signal having an envelope with
an excessively elongated trapezoidal shape, as shown
schematically in FIG. 7. In FIG. 8, the waveform 50
signal. In accordance with an aspect of this invention,
circuit means are provided which are coupled to the
input and output transducer means for initiating a timed
succession of surface wave bursts, or burst components,
on the display surface and for detecting touch-induced
ence of a contaminant (e.g., grease on the display sur
face) as a “touch”.
perturbations of received wave bursts, the circuit means
including means for rectifying the output from the out
‘ The above described preferred embodiment (FIG. 2)
lyzing the output signal to determine the timing of the
is shiown as having re?ective gratings G1, G2, G3 and
G4, the elements of which are non-uniformly spaced.
As already noted, in a practical embodiment this is
desirable since a grating whose elements are uniformly
spaced would re?ect uniformly and thus produce an
exponential fall-off in radiated power along its length.
That is to say, if for each unit of length along the ?xed
grating, a ?xed percentage of the power incident there
upon is radiated sideways, a smaller residue of power
wave burst perturbation. In a preferred embodiment,
remains. If the same ?xed percentage of that power is
put transducer means to develop an electrical character- ‘
ization of the perturbation and for developing an output
representing the timing of said characterization of said
perturbation. From that output, it is determined which
of the plurality of paths was traversed by the touch-per
turbed wave burst and thereby the location of the touch
along the coordinate axis of the display surface.
A number of arrangements are contemplated for ana
means are provided for sampling the amplitude of the
radiated in the succeeding section, it can be seen that the
recti?ed output from the output transducer at a plural 15 power decreases in a geometrical progression.
ity of time spaced points. Means are provided for stor
byway of review, desirably, a ?at response such as is
ing the amplitude samples for future reference. During
shown in FIG. 3, 4 or 8 is preferred. In accordance with
a touch of the display surface, means are provided for
an aspect of this invention, the re?ectivity of the re?ec
again sampling the amplitude of the output transducer
tive elements constituting the re?ective grating or grat
output and comparing the developed touch-related
amplitude samples with the stored reference samples.
that the initial elements have a relatively low re?ectiv
Means are provided for developing a signal represent
ing the point of greatest difference, or if desired the
tivity. Stated in another way, the re?ective array has an
greatest ratio, between the amplitudes of the reference
samples and the touch-related samples and thus the
timing of the touch-perturbed wave burst.
As mentioned above, a designer utilizing the present
ings which adjoin the input transducer is weighted such
ity and the succeeding elements have increasing re?ec
increasing coefficient of re?ection in the direction away
25 from the adjoining transducer so as to compensate for
the fall-off in wave amplitude which results from the
continuing diversion of wave energy into paths across
invention has a free choice in tailoring the touch panel
the panel. It should be understood that the re?ective
speci?cation to the standards of a device driven by the
array adjoining the input transducer should have in
panel. That is, the sampling means can be adjusted and
creasing re?ectivity in the direction of wave propaga
designed to sample at any selected time interval to cor
tion, but for the array adjoining the output transducer,
respond to the standards of the driven device. For ex
the array should have a corresponding decrease in re
ample, if the touch panel apparatus drives a computer,
?ectivity in the direction of wave propagation. Thus, in
the sampling frequency may desirably be selected to
both cases, the re?ectivity should increase in the direc
correspond to every character or every other character 35 tion away from the adjoining transducer. This desirable
for which the computer is programmed. Typical com
attribute is realizable in the FIG. 2 embodiment by
puters today have 640 matrix points along a horizontal
virtue of the depicted non-uniform spacing of the re?ec
' line, corresponding to 80 characters. One would like to
have touch resolution elements that have some integral
tive elements constituting each of gratings Gl-G4.
For perfect uniformity of the transversely radiated
relationship to the number 640, if the driven computer
has 640 horizontal matrix points. There is nothing inher
40 surface wave power, and assuming no power loss by
ent in the output signal developed in accordance with
the present invention that needs to be changed if one
wishes to drive a computer having, instead, 512 matrix
array must decrease linearly with distance. For this to
points (64 characters) along its horizontal axis. All that
is required is that the timing of the electronic sampling
signal be changed. This is not true of prior art ?xed
‘emitter systems because they cannot readily be changed
dissipation anywhere in the array, the power along the
occur, the power re?ectivity must increase inversely
with the distance remaining to the point beyond the
array where the linearly decreasing power would drop
to‘zero. (As used herein, re?ectivity is the fraction of
the longitudinally incident power diverted transversely
per unit length.) In other words, power re?ectivity K
to meet a different standard. Thus, in such priorart
must increase with the distance x from the transducer in
systems, a physically different touch panel would have 50 accordance with
to be provided for every standard desired to be met.
With the present invention, only the timing of the sam
pling signal need be changed to accommodate a variety
of different standards in the driven devices.
Yet another approach to analyzing the output from 55 where 'Ke is the maximum re?ectivity actually used at
the far end where x=G, the symbol G representing the
the output transducer to determine the timing of the
perturbed wave burst is to provide differentiating
means for differentiating the recti?ed output of the
length of the grating. Note that K and Ke have the
dimension of a reciprocal length (fraction of power
diversion per unit length).
output transducer means. The zero crossing of the re
sulting signal represents the timing of the touch-per
turbed wave burst. While the differentiating approach
There are a number of ways the re?ectivity of the
grating can be increased in the direction away from the
has the advantage that relatively inexpensive electron
adjoining transducer so as to ?atten out the output
waveform of the output transducer. One way would be
to increase the thickness of the re?ective elements in the
burst components issuing from and intercepted by 65 direction away from the adjoining transducer, as the
themwill enable the output transducer to produce a
power re?ectivity is proportional to the square of the
ics can be utilized, the gratings employed in such a
system must be very carefully tailored to insure that the
substantially ?at output signal. Moreover, the differenti
ating approach is vulnerable to interpreting the pres
thickness of the re?ective elements. This could be done,
in theory, by screen printing or etching (where grooves
extends in the direction of the coordinate axis 69 and is
of such length as to intercept each of the plurality of
are used), however in practice this approach might
prove to be difficult to execute.
A second, more practical, approach is to remove
selected ones of the re?ective elements in accordance
with a formula which yields the desired increase in
burst component paths. Circuit means (not shown) may
re?ectivity along the array. See FIG. 9, also FIG. 2 and
the earlier discussion concerning tailoring a re?ective
of received wave burst components. It will be under
stood that unlike the other embodiments described, the
be provided for initiating surface wave bursts on the
surface and for detecting touch-induced perturbations
varying component of the transit time of each of the
surface wave burst components will only be half that in
the aforedescribed embodiments. In the aforedescribed
embodiments the variable part of the transit time of the
grating. For example, if one wished to cover a range of
power re?ectivity variation of 9 to 1 (an amplitude ratio
of about 3 to 1), one would eliminate two of every three
strips at the beginning of the array. Strips would be
surface wave burst component had an outgoing compo
nent and a returning component, whereas in the FIG. 12
gradually added (fewer strips eliminated) along the
length of the array until at the end of the array, no strips
would be eliminated. This is a practical method and has
embodiment, the surface wave burst component transit
15 time has only an outgoing component. It is, of course,
been reduced to practice successfully.
understood that the functions of input and output trans
Yet another method involves weighting the re?ectiv
ducer may be interchanged.
Yet another embodiment of the invention is shown
schematically in FIG. 13. Whereas in each of the afore
described embodiments, the wave redirecting means, or
ity of each of the individual re?ective elements, as
shown schematically in FIG. 10 by fragmenting indi
vidual elements of an array G’l. The elements have
greater interruptions (which may be produced accord
re?ective grating, is continuous, producing an analog
ing to a random formula) at the end of the array nearest
output signal, in the FIG. 13 embodiment the wave
redirecting means comprises discrete groups of wave
of the array.
re?ective elements, two of which groups are shown at
In yet another embodiment (FIG. 10A), the re?ective
array G"1 has array elements whose individual length 25 72 and 74. The groups are spaced in the direction of the
coordinate axis such that the paths of the surface wave
increases in the direction away from the adjoining trans
burst components, shown schematically at 76, 78, are
ducer and whose individual position in a direction along
the transducer (input or output) than at the opposite end
the length of the element is varied within the side
boundaries of the array. With all these methods, the
reduction in element length p corresponds to an equal
reduction in amplitude of the re?ected burst, and the
power reduction, above referred to as K/Ke, equals p2.
The same technique can be used, that is, weighting
the re?ective elements according to a prescribed re?ec
tivity shading formula, to compensate for energy dissi
discrete and non-overlapping.
The output of the output transducer (not shown),
rather than being an analog signal as shown for example
at 48 in FIG. 8, will have a pulse characteristic as
shown, for example, in FIG. 14. in FIG. 14 the pulses 80
have a height which de?nes an envelope corresponding
to the wave form 48 in FIG. 8. In FIG. 14, a pulse 82 of
35 reduced height corresponds in time to the timing of a
surface wave burst component which has been per
turbed by its passage through a touched region on the
pation in the re?ective array or other factors for which
compensation may be desirable. The equation previ
surface of the touch panel apparatus.
ously mentioned in connection with the preferred em
bodiment allows for uniform dissipation. Various other
In the FIG. 13 embodiment, circuit means (not
shown) includes processing means for processingthe
applications of the principles of the present invention
pulses and may develop a waveform such as shown in
FIG. 15 consisting of a series of pulses 84 wherever the
will now be discussed.
Whereas the preferred embodiment is described as
having separate input and output transducer means and
pulse height exceeds a predetermined threshold and a
by the common input/output transducer 61 back across
the panel where they are redirected by a grating 62 back
to the input/output transducer 61.
mining, by an analysis based on the timing of the de
tected pulse void associated with a perturbed wave
pulse void 86 corresponding to the missing pulse 82 (less
means redirecting a burst of surface waves launched
from an input transducer to a different output trans 45 than the threshold). The circuit means aforedescribed
for initiating surface wave bursts on the surface and for
ducer, it is contemplated that the input transducer may
touch-induced perturbations of received
also be the output transducer. See FIG. 11 wherein a
wave burst components may include means for deter
re?ector 60 is employed to re?ect the waves launched
burst component or by counting the pulses preceding
the void, which of the plurality of paths was traversed
by the touch-perturbed wave burst component and thus
the location of the touch along the coordinate axis of
The re?ector 60 may consist of a series of half
wavelength spaced re?ecting elements-either raised
or depressed grooves—as is well known in the surface
wave art.
FIG, 12 illustrates yet another embodiment of the
invention comprising a substrate 64 to which is coupled
an input transducer 66 for launching a burst of surface
waves on the surface of the substrate 64. Surface wave
the display surface.
FIG. 16 illustrates yet another embodiment of the
invention in which the coordinate axis is not linear, but
rather is angular. Such a one-coordinate system (angle
only) could be used, for example, on the cover of a
redirecting means includes a grating 68 of the character 60 conventional meter to initiate an action in response to
the meter reading. The FIG. 16 embodiment, which
of the gratings described above for redirecting surface
shows such a system in highly schematic form, com
wave burst components derived therefrom across the
prises a display substrate 88 coupled to which is an input
surface of the substrate 64 to output transducer means
transducer 90 for launching circular surface waves
70 along a plurality of paths of different lengths which
are respectively associated with different positions 65 which radiate outwardly across a display surface hav
ing angular coordinate markings 92 from the apparent
along a coordinate axis on the display surface.
center point of the angular coordinate system. Surface
The FIG. 12 embodiment differs from other embodi
wave redirecting means in the form of a series of dis
ments described in that the output transducer means 70
other touch-controlled device which is capable of reci
ognizing touch positions along a predetermined coordi
plurality of paths of different lengths which are respec
tively associated with different angular positions on the
display surface. Circuit means similar to that described 5
means 90, 96 for initiating surface wave bursts on the
propagating through the region of the touch;
surface of the substrate 88 may be provided. As for the
input surface wave transducer means acoustically
coupled to said touch surface of said substrate and
above described embodiment, the circuit means in
cludes means for determining by an analysis of the tran
sit time of a detected perturbed wave burst component,
which of the plurality of radial paths was traversed by
the touch-perturbed wave burst component, and thus
of the display surface.
nate axis on a touch surface, the apparatus comprising:
a substrate having a touch surface capable of propa
gating surface acoustic waves such that a touch on
said surface causes a perturbation of a surface wave
above, coupled to the input and output transducer
the angular location of the touch along the angular axis
1. In a touch control system for a display panel or
crete re?ectors 94 redirect the wave components de
rived from the burst to an output transducer 96 along a
utilizable, when excited, for launching surface
acoustic waves on said touch surface along a ?rst
path on said surface; and
means including an array of surface wave reflective
elements formed on said touch surface of said sub
strate along said ?rst path for deriving from said
The FIG. 16 embodiment illustrates that the princi
ples of the invention may be employed in a system in
surface acoustic waves a plurality of different wave
components, each component being reflected from
which the redirecting means does not redirect the sur
face waves across the display surface for detecting a
said array at a different location along the array,
and for directing said components across said
touch surface of said substrate in a progression of
paths transverse to said coordinate axis;
said array of elements comprising strips of a frit com
touch, but rather intercepts the surface waves after they
have traversed the display (touch) surface. It is, how
ever, understood that the functions of input and output
transducers may be interchanged, and if that is done, the
position deposited on said touch surface.
redirecting means 94 functions to redirect the surface 25
2. A display device comprising an image viewing
waves, now generated by transducer 96, onto radial
surface and at least one raised SAW-reflecting element
paths across the display surface toward transducer 90.
formed of a frit composition and secured to said surface.
As in each of the above embodiments, an output signal
3. Apparatus as in claim 2 wherein said frit composi
will be developed which reveals a perturbation associ
ated with a touch of the display surface, and the timing
of which perturbation signi?es, or can be processed to
tion comprises about 10% by weight of a nucleation
accelerating additive.
4. Apparatus as in claim 3 wherein said nucleation
accelerating additive is a refractory material.
5. Apparatus as in claim 4 wherein said refractory
material is a powder.
signify, the position of the touch on the panel along the
predetermined coordinate axis.
Still other embodiments and implementations of the
present invention are contemplated and are within the 35
6. Apparatus as in claim 5 wherein said refractory
powder is zirconium oxide.
spirit and scope of this invention.
We claim:
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