U.S. patent application number 09/864833 was filed with the patent office on 2002-12-12 for multi-user touch surface.
This patent application is currently assigned to Mitsubishi Electric Research Laboratories, Inc.. Invention is credited to Dietz, Paul H., Leigh, Darren L..
Application Number | 20020185981 09/864833 |
Document ID | / |
Family ID | 25344172 |
Filed Date | 2002-12-12 |
United States Patent
Application |
20020185981 |
Kind Code |
A1 |
Dietz, Paul H. ; et
al. |
December 12, 2002 |
MULTI-USER TOUCH SURFACE
Abstract
A multi-user touch system includes a surface on which are a
pattern of mounted antennas. A transmitter transmits uniquely
identifiable signals to each antenna. Receivers are capacitively
coupled to different users, the receivers are configured to receive
the uniquely identifiable signals. A processor then associates a
specific antenna with a particular users when multiple users
simultaneously touch any of the antennas.
Inventors: |
Dietz, Paul H.; (Hopkinton,
MA) ; Leigh, Darren L.; (Belmont, MA) |
Correspondence
Address: |
Patent Department
Mitsubishi Electric Research Laboratories, Inc.
201 Broadway
Cambridge
MA
02139
US
|
Assignee: |
Mitsubishi Electric Research
Laboratories, Inc.
|
Family ID: |
25344172 |
Appl. No.: |
09/864833 |
Filed: |
May 24, 2001 |
Current U.S.
Class: |
315/169.3 |
Current CPC
Class: |
G06F 3/038 20130101;
Y10S 323/904 20130101; G06F 3/0445 20190501; G06F 3/0446
20190501 |
Class at
Publication: |
315/169.3 |
International
Class: |
G09G 003/10 |
Claims
We claim:
1. A multi-user touch system, comprising: a surface including a
plurality of antennas mounted thereon; a transmitter configured to
transmit uniquely identifiable signals to each antenna; a plurality
of receivers, each receiver capacitively coupled to a different
user, the receivers configured to receive the uniquely identifiable
signals; means for associating a specific antenna with a particular
users when multiple users simultaneously touch any of the plurality
of antennas.
2. The system of claim 1 wherein the touch sensitive surface
further comprises: a plurality of conductive pads arranged in rows
and columns.
3. The system of claim 1 wherein the plurality of conductive pads
are arranged on a laminated substrate.
4. The system of claim 1 wherein each receiver further comprises:
an amplifier connected to a synchronous demodulator; an
analog-to-digital converter coupled an output of the synchronous
demodulator; and
5. The system of claim 1 wherein the transmitter and each receiver
are connected to a processor for associating the specific antenna
with each particular users
6. The system of claim 1 wherein the surface is disposed on a table
top.
7. The system of claim 1 wherein the surface is mounted on a
wall.
8. The system of claim 1 wherein the surface conforms to an
arbitrary shaped object.
9. The system of claim 1 wherein the antennas are arranged in a
regular pattern.
10. The system of claim 1 wherein the antennas are arranged in an
irregular pattern.
11. The system of claim 1 further comprising: means for associating
two antennas with the particular user when the particular user
simultaneously touches two antennas.
12. The system of claim 11 wherein the two antennas define a
bounding box.
13. The system of claim 1 wherein the particular user
simultaneously couples multiple antennas, and further comprising:
means for estimating a centroid of the multiple antennas.
14. The system of claim 1 wherein the capacitive coupling uses near
field coupling, and frequencies of the uniquely identifiable
signals are substantially under 1 MHz to maximize a signal to noise
ratio at the receivers.
15. The system of claim 1 wherein another user touches the
particular user while the particular user touches any of the
plurality of antennas, and further comprising: means for
associating the specific antenna with the particular user and the
other user.
16. The system of claim 2 wherein the means for associating further
comprises: means for driving the uniquely identifiable signals to
each antenna in turn; and means for measuring times when the
transmitted signals are present at the receivers to differentiate
the antennas.
17. The system of claim 1 wherein the means for associating further
comprises; means for generating orthogonal spreading codes in the
transmitter; means for modifying the transmitted signals according
to the spreading codes; and means for separating the transmitted
signals according by correlation with the spreading codes.
18. The system of claim 17 further comprising: means for generating
a pseudo random noise bit sequence using a polynomial function; a
shift register coupled to the means for generating; and a plurality
of taps coupled to the shift register to provide time delays of the
pseudo random noise bit sequence and to modify the transmitted
signals according to the time delayed pseudo random noise bit
sequence.
19. The system of claim 1 wherein the plurality of antennas are a
single resistive substrate, and a plurality of transmitters are
coupled to the resistive substrate.
20. The system of claim 1 wherein the transmitted signals are
driven in reverse by coupling one transmitter to each user, and
coupling the antennas to a single receiver.
21. The system of claim 1 wherein each antenna is coupled to a
unique transmitter and associated unique receiver to differentiate
multiple simultaneous touches by a single user.
22. The system of claim 1 further including timing signals to
differentiate multiple simultaneous touches by a single user.
23. A method for operating a multi-user touch system, comprising:
transmitting uniquely identifiable signals to a plurality of
antennas mounted on a surface; receiving the uniquely identifiable
signals when users capacitively coupled the transmitted signal by
touching the antennas; and associating specific touched antennas
with particular users when multiple users simultaneously touch any
of the plurality of antennas.
24. The method of claim 14 wherein the receivers are capacitively
coupled to the users via conductive chairs.
25. The method of claim 14 wherein the capacitive coupling uses
near field coupling, and frequencies of the uniquely identifiable
signals are under 1 MHz to maximize a signal to noise ratio at the
receivers.
26. The method of claim 23 wherein the plurality of antennas are
mounted on a tabletop, and further comprising: projecting an image
onto the tabletop.
Description
FIELD OF THE INVENTION
[0001] The present invention relates generally to the field of
touch sensitive surfaces, and more particularly to large-scale,
multi-user touch surfaces.
BACKGROUND OF THE INVENTION
[0002] Touch screens are widely used to present a user with an
intuitive pointing interface. For example, touch screens are used
in automatic teller machines, scientific and industrial control
devices, public kiosks, and hand held computing devices, to name
but a few common touch applications. Touch screens can use
resistive, capacitive, acoustic, or infrared sensors. In most touch
screen applications, the touch sensitive surface is permanently
mounted on a display device such as a cathode ray tube (CRT), or a
liquid crystal display (LCD).
[0003] During operation of most prior art touch screens, a
formatted image is rear projected through the touch screen while a
transmitter drives signals across the x- and y-axis of the touch
screen. As the user touches the screen with a finger or stylus,
pointing out specific parts of the image, receivers detect the
location of specific x- and y-coordinates of where the screen is
touched. The receivers are coupled to processes that can then take
appropriate actions in response to the touching and the currently
displayed image.
[0004] Recently, there has been interest in extending touch
technologies to electronic whiteboard applications. There, the main
difference is one of scale. As stated above, traditional touch
screen are designed for use with small displays and a single user,
whereas whiteboards are large displays, generally used in group
situations.
[0005] While it is possible to scale up touch screen, specifically
with acoustic signals, prior art touch screens do not differentiate
among the touches by multiple users. Also, most prior art touch
screen cannot distinguish multiple, none identify simultaneous
touches by one or multiple users.
[0006] While electronic whiteboards are useful for group
discussions, turning the interactive surface into a table that a
number of users can be seated around would facilitate longer work
sessions. A problem with this arrangement is that users tend to put
items on tables, such as books, paper, and cups. For pressure
sensitive surfaces, static objects generate spurious touch points.
In a single touch system, any such object causes the surface to
malfunction.
[0007] Therefore, an improved interactive touch surface should have
the following characteristics: detects multiple, simultaneous
touches, detects which user is touching each location, objects left
on the touch surface should not interfere with normal operation,
withstand normal use without frequent repair or recalibration, not
require additional devices, e.g. no special stylus, body
transmitters, and the like, and be inexpensive.
SUMMARY OF THE INVENTION
[0008] It is an object of the invention to provide a multi-user,
large-scale touch surface. It is another object of the invention to
provide a touch system that can uniquely associate multiple
simultaneous touches with multiple users. It is also an object of
the invention to differentiate multiple simultaneous touches by a
single user. It is also desired to have a touch surface that can
operate independent of a display device.
[0009] The invention provides a multi-user touch system that
includes a touch sensitive surface with touch sensitive locations.
The basic idea behind the invention is to have the users complete a
capacitively coupled circuit running from the touch point on the
touch surface to devices embedded in the environment. For example,
an interactive display table contains an array of antennas, each
transmitting a unique signal. When a user touches near a particular
antenna, the transmitted signal is capacitively coupled to that
user. If the user is sitting or standing on a conducting electrode,
the signal will also be capacitively coupled to that electrode. A
receiver connected to that electrode can thus detect which antennas
the user is touching near. Of course, the system can also work in
reverse, with the table being an array of receiving antennas and
the user coupling signal from a unique transmitter in a chair or
floor plate.
[0010] With proper design, capacitive coupling through the human
body is reliable. One consideration is to operate via "near field,"
i.e., capacitive, coupling. By limiting the transmitting
frequencies so that the antennas are very short compared with a
quarter wavelength, very little energy is radiated. Thus, for
reasonable sized tables, frequencies are in the sub-MHz. range to
prevent EMI compatibility problems.
[0011] More particularly, a transmitter is coupled to multiple
antennas mounted on a surface to transmit uniquely identifiable
signals to the antennas. Receivers are capacitively coupled to
different users, and configured to receive the uniquely
identifiable signals. When multiple users simultaneously touch any
of the antennas, each touched antenna is associated with a
particular user.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a schematic of a multi-user touch screen according
to the invention.
[0013] FIG. 2 a block diagram of a receiver according to the
invention;
[0014] FIG. 3 is a block diagram of a touch screen used in one
embodiment of the present invention; and
[0015] FIG. 4 is a schematic of the capacitive coupling according
to the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0016] Our invention provides a touch sensitive system that enables
multiple users to simultaneously touch a surface, and to associate
the location of each touch or multiple simultaneous touches with a
specific user. Our touch system capacitively couples a signal
between locations on the touch surface and users so that unique
touched locations can be identified with specific users. Thus,
multiple users can simultaneously interact with a touch
surface.
[0017] System Structure
[0018] As shown in FIG. 1, a preferred embodiment of our invention
can use a tabletop 101 to display an arbitrary image, not shown.
The tabletop is fitted with conductive rows 102 and columns 103 of
touch sensitive pads 105. The pads, as will be described in greater
detail act as antennas. The conductive touch pads 105 form a touch
sensitive surface 300 that coincides with the displayed image. In
the arrangement shown, the rows and columns are arranged in a
diamond pattern, although it should be understood that other
geometric patterns are also possible, as described below.
[0019] The conductive rows and columns of pads can be deposited on,
for example, a laminated substrate using techniques similar to
those used to fabricate printed circuit boards. The size and
separation of the touch pads determine the effective resolution of
the touch locations.
[0020] A transmitter 120 individually supplies uniquely
identifiable electronic signals, described below, to the rows and
columns of touch pads. As shown, the transmitter 120 includes a
microprocessor 110, shift registers 111, latches 112, and drivers
113. There is a set of registers, latches, and drivers for the for
the rows and columns of touch pads 105.
[0021] In addition, there are chairs 121-122 arranged around the
table, one for each user. The chairs include conductive parts, for
example, the arms, legs, or seat. The conductive parts of each
chairs are electrically connected to individual receivers 200. It
should be understood that other conductive items can also be used
to identify users, e.g. conductive floor mats, wristbands, belts,
etc. However, we prefer conductive chairs because they form a
non-obtrusive, natural setting where users can easily operate the
system in comfort. The receivers 200 are coupled to a processor 150
that controls the overall operation of the system 100. See FIG. 4
for a simplified schematic of the system of FIG. 1.
[0022] FIG. 2 shows the receiver 200 in greater detail. The
receiver 200 includes an amplifier 210 connected to a synchronous
demodulator 220. The output of the demodulator is coupled to an
analog-to-digital convertor 200, which in turn is coupled to a
microprocessor 240. The microprocessor receives synchronization
signals 119 from the microcontroller 110 of the transmitter, and
produces location coordinates for the processor via a serial, e.g.,
RS-232, interface 250.
[0023] FIG. 3 shows the details of the touch sensitive surface 300.
In one embodiment of the invention, the touch surface is
constructed as a two-layer printer circuit board with edge
connectors 311-312 connected to the respective drivers 113. The
layers include a first insulator layer 301, a row layer 302, a
second insulator layer 303, a column layer 304, and a mechanical
support layer 305.
[0024] Antenna Patterns
[0025] There are a number of antenna patterns possible for the
touch sensitive surface or antennas. Here we describe the more
interesting ones. In a "full matrix" pattern, there are a very
large number of antennas arranged in a regular grid. Such a matrix
of individually driven antenna "pixels" allows an unambiguous
determination of multiple touch locations, even for a single
user.
[0026] Minor variations on the full matrix include the use of
hexagons, triangles or some other tessellating geometry. There is
no reason why the antennas must be on a flat surface. For some
applications, the surface can conform to any appropriately shaped
object. It such cases irregular patterns of antennas may be
desired. Highly irregular patterns might also be useful for some
applications where the pattern corresponds to some arbitrary
image.
[0027] In practice, the full matrix pattern may not be needed for
many applications. Although the simultaneous, multi-user feature is
desired, perhaps it is sufficient for each user to indicate at most
a single touch point, or a bounding box. This functionality can be
obtained with a simple row and column pattern, as shown in FIG. 1,
that drastically reduces the number of antennas.
[0028] Designing a row/column pattern is not trivial. The problem
is that antennas also shield. So arranging a sheet of row
conductors (antennas) and then covering the conductors with a sheet
of column conductors will shield the row conductors anywhere they
overlap. We have found the connected diamond pattern shown in FIG.
1 to be a good choice. This pattern has the interesting property
that the row conductors are identical to the column conductors,
rotated by ninety degrees. This allowed us to design a single
conductor pattern and use it for both rows and columns, saving
manufacturing costs.
[0029] In practice, a user's touch will most likely span multiple
rows and multiple columns with different degrees of coupling. These
can be used to estimate a centroid for the point of touch, to
obtain location with a higher resolution than the row and column
spacing. However, an alternative way of using this information is
to present a bounding box for the touch event, defined by the min
and max rows and columns of antennas significantly coupled.
[0030] This leads to an interesting use of the device. A single
user can touch two points to define a bounding box. This is a very
natural way of selecting a rectangular area in graphics design
systems. In practice, we suggest using two modes of operation: when
the coupled area is small, presume the user is indicating a point,
when the coupled area it large, presume that the user is trying to
specify a bounding box. The end result is that even this simplified
row/column design allows simultaneous multi-touch use for all
users.
[0031] Of course, it would be an advantage when the row/column
pattern can distinguish multiple touches from a single user. The
problem is that given two X and two Y coordinates, the system
cannot tell if the intended touches are (X1, Y1) and (X2, Y2) or
(X1, Y2) and (X2, Y1). In most cases, timing information can be
used to disambiguate the two cases. If (X1, Y1) and (X2, Y2) are
coupled successively, we can estimate the pairings.
[0032] Analog Antennas
[0033] The purpose of the antenna arrays (conductive touch pads) is
to generate coupling patterns that are location dependent in a
simple manner. Alternatively, this can be accomplished using
resistive sheets driven from multiple points.
[0034] The easiest way to think about this is to consider a
one-dimensional case. A resistive strip is driven by an oscillator,
first on one end, and then on the opposite end, each time grounding
the undriven side. This produces a signal that linearly decreases
in amplitude moving towards ground. Switching the driven side flips
the direction of this linear drop. By looking at the ratio of the
coupled signal during the two cases, touch locations can be
determined.
[0035] This can be extended to multiple dimensions. Signals can be
applied so as to drop linearly in the X dimension and then in the Y
dimension. However, this cannot be accomplished by merely putting
strip conductors on the edge of a resistive sheet--the unused
conductors will short along the desired dimension. One partial
solution is to break the strip conductors into a series of small
connection points that can be disconnected when driving the other
axis. A more practical approach places the conductors in the four
corners, and calibrate for the non-linear field patterns that
result.
[0036] System Operation
[0037] During operation, images can be projected onto the table.
The projection can be overhead projection, or rear projection when
the touch surface is transparent or translucent. For many
applications, such as, games or industrial control, the image can
be fixed on the touch sensitive surface by other means, or a mix of
fixed and projected images can be used. If the touch surface is
mounted on a wall, as described below, the projection can be
conventional, or any other projection means can be used.
[0038] In the case the surface is mounted on a table top, users
sitting in the conductive chairs 121-122 cause a capacitive
coupling between the transmitter and the receivers 200 when the
touch surface is touched by a body part, e.g., fingers or toes, or
a conductive pointers held by the users. In effect, the user
couples the transmitter to the receivers via the touch screen.
[0039] The coupled signal is analyzed to determine the locations
that are capacitively coupled to each chair and hence the unique
locations pointed at by each seated user can be identified.
[0040] The system can be understood with the aid of a simplified
equivalent circuit as shown in FIG. 4. C.sub.table 401 represents
the capacitance between the user's finger and a transmitting
antenna of the surface. C.sub.chair 402 represents the capacitance
between the user and a conducting chair. The coupling capacitance
is the series combination of these two capacitances:
C.sub.coupling=(C.sub.table*C.sub.chair)/(C.sub.table+C.sub.chair)
[0041] Because the coupling area of a finger is very small compared
to the entire upper torso in a conducting chair, C.sub.table tends
to be very small compared to C.sub.chair. Thus, the C.sub.coupling
is approximately equal to C.sub.table. This means that the precise
capacitive coupling via the chair is inconsequential. In the case
the coupling is via a conducting floor plate, the coupling area of
feet is far smaller, but still very large compared to a finger. One
might think that thick-soled shoes might be problematic because
they dramatically increase the spacing between the conductors.
However, we have found that we get more than sufficient coupling,
partially because the thick rubber soles have a high dielectric
constant increasing the capacitance.
[0042] For the system to work well, we prefer fairly independent
coupling paths among the users. This constraint is violated if two
or more users, or their chairs are touching, or are in very close
physical proximity. In this regard, social norms of "personal
space" are sufficient to keep the inter-user coupling acceptably
small.
[0043] However, this behavior can be explicitly exploited. By
touching another user, or the user's chair, the touches of either
user are interpreted as touches for both users. Typically, the
coupling "through" a second user is considerably weaker, and thus
it is possible to determine a "primary" user versus "shared" users.
This provides a simple and intuitive mechanism for users to jointly
indicate a selection.
[0044] As noted above, the system can work in one of two ways--the
touch surface can be a large array of antennas transmitting
uniquely identifiable signals to a small number of receivers
associated with particular users, or a large array of antennas
receiving a small number of uniquely identifiable signals from
transmitters associated with particular users. We have found the
former to be a superior configuration for a number of reasons.
Primary, the transmitter can be driven with logic level signals
that are easy to generate in large number. Receivers are somewhat
more complex to implement. Thus, we chose the configuration that
minimizes the number of receivers.
[0045] There are many ways of generating uniquely identifiable
signals, as described in detail below. In signal processing terms,
we can use an orthogonal set of signals. For example, every antenna
is driven at a different frequency. A receiver that is coupled to a
number of antennas then identifies a particular user by examining
the spectrum of the received signal. However, generating the
numerous frequencies required for a large array can be relatively
expensive.
[0046] Time division multiplexing is another option. In this case,
each antenna is separately driven in turn by a fixed frequency, and
the timing of the received signals is used to determine which
antennas are presently coupled. This system is very simple to
implement because the receivers are particularly simple because
they are looking for a single frequency. However, this technique
may not be appropriate for very large arrays. The problem is a
fairly subtle one caused by the interplay of the various
constraints.
[0047] For high responsivity, the entire array must be scanned ten
to a hundred times per second. However, as noted above, practical
modulating frequencies are limited to the sub-MHz. range. This
leaves very few modulation cycles per antenna, making receiver
design difficult, especially considering of other interfering
sources of noise.
[0048] There are ways of reducing the scan time that help to extend
the practicality of time division multiplexing schemes. Large
numbers of antennas can be driven simultaneously to see if there is
coupling from any of them. Thus, binary search patterns may be used
to locate particular touch points in roughly logarithmic time.
However, this is not as straight forward as at first implied. In
general, there will be degrees of coupling to multiple antennas, so
in practice, these searches narrow down the candidate areas, which
are then searched exhaustively.
[0049] As anyone familiar with telephone systems will note, in
addition to time and frequency division multiplexing, code division
multiplexing can be considered. In fact, this turns out to be a
particularly elegant approach for large arrays. A simple generating
polynomial is used to generate a pseudo random bit sequence with
the property that the autocorrelation of this sequence is extremely
small everywhere except at zero. This sequence is then fed into a
long shift register to generate a binary tapped delay line with one
tap per an antenna. The taps directly modulate the antennas. The
receiver then cross-correlates the received signal with the
original sequence. Each lag in the cross-correlation signal
corresponds to the coupling from a particular antenna. This allows
all of the couplings to be determined by a single calculation.
[0050] The advantage of this code division multiplexing scheme is
that it scales extremely well to large numbers of antennas. Adding
antennas merely requires adding extra taps on the shift register.
On the receiver side, FFT and other techniques can dramatically
decrease the difficulty of the cross-correlation calculation.
Unlike time division multiplexing, the effective antenna
integration time remains long and constant with increasing number
of antennas, avoiding noise issues.
[0051] Transmitting and Receiving
[0052] The capacitive coupling of our system relies on near field
coupling. Therefore, far field radiation by the touch sensitive
screen should be minimized to maximize the signal to noise ratio
(SNR) at the receivers 200. For this reason, the frequencies of the
transmitted signals are kept low, e.g., under 1 MHz for practical
table sizes. This has an important impact on the design of the
system. At lower frequencies, integration time required at the
receiver increases to achieve a usable SNR. As an advantage the
frequencies are well below frequencies of the radio spectrum,
making our system useable in environments where RF signals could
interfere with the operation of other equipment.
[0053] Time Division Multiplexing
[0054] In a time division multiplexed transmitting scheme, each row
and then each column of pads is individually driven, in turn, so
that the number of individual transmitters can be relatively small.
By measuring the times when the transmitted signals are present at
the receivers 200, the rows and columns coupled are readily
differentiated. This can be accomplished with the synchronization
signals 119.
[0055] Code Division Multiplexing
[0056] Time synchronized signals are not the only easily separable
signals. With code division multiplexing, orthogonal spreading
codes at the transmitter allow multiple signals to occupy the same
frequency bandwidth. In the receivers 200, the multiple signals are
then separated by correlating them with the original spreading
code. With a properly chosen pseudo random noise (PRN) bit
sequence, the autocorrelation function is very small everywhere
except at zero.
[0057] Thus, by driving each row and column of pads by the same PRN
bit sequence, but each sequence with a unique time delay, received
signals can easily be separated by cross-correlating with the
original sequence.
[0058] Therefore, a single PRN bit sequence is generated for the
transmitter using a polynomial function. The PRN sequence is passed
through a shift register to provide time delays. Then, the
transmitted signals are spread by the PRN sequence from taps off
the shift register and transmitted by the different receivers.
[0059] The code division multiplexed scheme has many advantages.
First, locations on the entire table can be determined by one
cross-correlation per receiver. Second, the effective integration
time can be very long compared to the time division scheme. Third,
the system is robust to many types of interference due to the
spread spectrum operation.
[0060] Resistive Touch Screen
[0061] Rather than using detailed patterns of rows and columns
pads, a single resistive substrate can also be used as the touch
sensitive surface, as described above. In this case, a very small
number of transmitters are used, for example one at each corner, or
one at each side. The resistive drop across the substrate is
different for each transmitter, so the relative amounts of signal
capacitively coupled up to a user can be used to determine the
touch location.
[0062] Alternative Embodiments
[0063] In an alternative embodiment, the electrical signals are
driven in reverse so that the chairs 121-122 are coupled to unique
transmitters, and the rows and columns are coupled to a single
receiver.
[0064] In yet another embodiment, each unique location on the table
can be individually coupled to a transmitter or a receiver. This
arrangement enables the identification of multiple touch points by
a single user.
[0065] In this design with individually addressable locations,
there may not be sufficient time to integrate the signal over each
location while still maintaining a reasonable overall update rate.
In this case, we use a code division multiplexed scheme. By
analyzing the received codes, the touch locations can be
determined. Code division multiplexing allows sufficient
integration time because time sliced integration for each location
is not required.
[0066] Timing signals can also be used to disambiguate multiple
simultaneous touches. Other geometric patters, such as a triangular
mesh, also allow for multiple unambiguous touch locations. Note
that the mesh spacing should be sufficiently small so that a
fingertip spans at least one row and one column, yet large enough
to maximize capacitive coupling.
[0067] Applications
[0068] The system according to our invention can be used in any of
the interactive applications described above, but now we enable
multiple users to operate the system simultaneously. In addition,
the system can be used for a whole new genre of interactive games
where multiple users either compete with each other, or collaborate
to solve an unknown problem.
[0069] One of the key features of the system is its ability to
detect multiple touches allowing a number of people to
simultaneously interact with the system. For some cases, the
identity of the user may be unimportant. Thus a single receiver can
be used. A whimsical example can be a digital finger paint mural--a
wall that allows users to finger paint messages and art that slowly
change color and decay with time.
[0070] This system works by projecting digital video onto a full
matrix of touch pads, with the adjacent floor being a single
receiving electrode. Interestingly, the system can also be
implemented with a row/column touch wall. In this case, the floor
is partitioned into many separate receivers so as to provide each
user with an independent coupling path. The system can scan all of
these receivers for coupling, so that users can walk freely
about.
[0071] The other key feature of the system according to the
invention is the ability to determine which user is currently
touching near the antennas. This is a very powerful feature that
can be used many ways. For example, we generated a multi-player
game where different colored objects appear on the surface, often
simultaneously, and the player must quickly touch the objects that
are a particular color. The first player to do this correctly for
each object gets points credited to his or her score. Hitting the
wrong color deletes points. This game is only possible via the
identification feature of our invention.
[0072] The ability for simultaneous, identifying interaction opens
some interesting possibilities. One of the more intriguing ideas is
the ability to generate virtual personal work areas. Although the
system is designed for group collaboration on a common surface, in
practice, individuals may want to "break away" to briefly address
some subset of the problem, and then wish to integrate their result
into the whole. When these situations arise, the system can
generate a virtual personal work area in front of the appropriate
user that only responds to that user. The user can then manipulate
objects in this space, without impacting the larger work effort of
other users but for the loss of some screen space. Because these
virtual personal work areas are software defined, they can be
generated and destroyed on the fly, in any shape as desired.
[0073] The concept of virtual personal work areas can be extended
to special "privileged objects." A privileged object is an icon
that allows only certain classes of users to perform certain
operations with that object. For example, a plumber and an
electrician may be viewing the same house plan, but only the
plumber can modify the piping and only the electrician can modify
the wiring.
[0074] Although the invention has been described by way of examples
of preferred embodiments, it is to be understood that various other
adaptations and modifications may be made within the spirit and
scope of the invention. Therefore, it is the object of the appended
claims to cover all such variations and modifications as come
within the true spirit and scope of the invention.
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