Computer graphics processing and selective visual display system – Display peripheral interface input device – Touch panel
Reexamination Certificate
2000-05-19
2003-12-09
Chow, Dennis-Doon (Department: 2675)
Computer graphics processing and selective visual display system
Display peripheral interface input device
Touch panel
C345S169000
Reexamination Certificate
active
06661405
ABSTRACT:
BACKGROUND OF THE INVENTION
There are a variety of games, toys, and interactive learning devices in which a stylus is used to point to a region on a surface in order to input data or questions. There are several technologies to determine the position of a stylus on a sensing surface. One approach is to embed an array of pressure sensitive switches in the sensing surface, such as membrane switches. However, conventional membrane switches have limited resolution. Another approach consists of arrays of capacitive or inductive elements whose impedance is altered by bringing the stylus into contact with the surface. However, a disadvantage of this approach is that a large number of pixel elements are required to achieve a high resolution. Moreover, since capacitive and inductive effects are typically small, the stylus must be brought into close proximity to the pixel in order to obtain a strong position signal.
In many applications it is desirable to be able to determine the position of a stylus disposed a short distance away (e.g., 1 mm to 2 cm) from an electrically active surface. In many consumer products it is desirable to protect electrically active elements with a protective layer of plastic which is thick enough to provide both mechanical and electrical insulation. The insulating material, such as a layer of plastic, may also be patterned with numbers, indicia, symbols, and drawings which facilitate the user inputting data by pointing to a number, indicia, symbol, or drawing disposed on the surface of the plastic. Other applications include systems in which the number, indicia, symbol, or drawing is disposed on a top (open) page of a booklet. The position of a pointer disposed on the open page of the booklet may be sensed even though the pointer is separated from the active surface by the thickness of the booklet.
An electrographic sensor unit and method based upon a geometric algorithm that is described in U.S. Pat. No. 5,686,705 “Surface Position Location System and Method” and U.S. Pat. No. 5,877,458 “Surface Position Location System And Method,” which is assigned to the assignee of the present invention. According to the teachings of U.S. Pat. Nos. 5,877,458 and 5,686,705 the position of a stylus is determined by calculating the intersection point of equipotential lines based upon the measured signal strength received by the stylus. The contents of U.S. Pat. Nos. 5,686,705 and 5,877,458 are hereby incorporated by reference in the present application.
FIGS. 1-4
show the general principals of the geometric location method of U.S. Pat. Nos. 5,686,705 and 5,877,458.
FIG. 1
is a simplified geometry illustrating the basic principles of operation. As shown in
FIG. 1
, a two or three dimensional conductive surface has a selected resistivity. In the embodiment of
FIG. 1
, three electrical contacts
12
,
14
, and
16
are connected to conductors
24
,
26
, and
28
, respectively, to a processor
30
. Also connected to processor
30
is conductor
18
with stylus
20
having a tip
22
for the user to indicate a position on the surface
10
that is of interest to the user. As shown in
FIG. 2
, when a user selects a point, P, on resistive surface
10
, a series of field potential measurements are performed to calculate the position of the stylus. A DC offset value is determined with no radio-frequency (rf) signals applied to any of the contacts
12
,
14
, and
16
. A second measurement is made by applying an equal amplitude rf signal to all three contacts
12
,
14
, and
16
, and processor
30
measures the full-scale signal value via stylus
20
. A third measurement is made by applying an rf signal to one of the contacts, such as contact
12
, with a second contact grounded, such as contact
14
. The signal measurement made by stylus
20
will lie somewhere along an equipotential line between those two contacts (i.e., line X in FIG.
2
). A fourth measurement is made by applying the signal to, and grounding a different pair of contacts, say
12
and
16
, and the signal measurement made with stylus
20
which will be somewhere along an equipotential line between those two contacts (i.e., line Y in
FIG. 2
) with the position of the stylus
20
being the intersection of lines X and Y. For the. purposes of illustration, lines X and Y are shown as straight lines. More generally the actual position of the stylus on the surface can be determined using mathematically or empirically determined models of the signal level gradients for the surface material with curved equipotential lines.
FIG. 3
illustrates an embodiment of an electrographic sensor system of U.S. Pat. No. 5,877,458 having a rectangular shaped piece of conductive material as sheet
100
. Afixed near the edge of sheet
100
, and making electrical contact thereto, are contacts
102
,
104
, and
106
. Connected between contacts
102
,
104
, and
106
on sheet
100
and contacts
126
,
128
, and
130
of signal generator
122
, respectively, are electrically conductive leads
108
,
110
, and
112
. Signal generator
122
includes an rf generator
124
, amplifier
134
, and switches
132
and
136
to determine which signals are fed to contacts
126
,
128
, and
130
. The position of switches
132
and
136
is controlled via cables
138
and
140
, respectively, from microprocessor
142
to select which contacts
102
,
104
, and
106
receive an normal or inverted rf signal.
Stylus
116
contains a receiving antenna and is coupled to signal measurement stage
120
via cable
118
. The signal is demodulated and turned into a digital signal via demodulator
144
and analog to digital converter (ADC)
146
. ADC
146
presents the digitized signal to microprocessor
142
. Microprocessor
142
includes RAM
145
, ROM
147
, a clock
148
to contain information related to the position that has been pre-stored along with an audio card
150
and speaker
154
or monitor
152
to output information on the selected area.
When an rf signal is coupled to one or more of the contacts
102
,
104
, and
106
the signal radiates through the conductive material of sheet
100
. Between a given set of energized contacts, such as contacts
102
and
104
, a signal level equipotential map
114
A exists because of the distributed resistance in the conductive material of sheet
100
. The signal level equipotential map includes the shape and values of the equipotential lines and may be stored in the memory of the microprocessor or the ROM
147
. The shape of the these equipotential lines may, in principal, be calculated by finding the unique solution of mathematical equations or may be determined empirically. Additionally, there will be a signal equipotential map for other sets of energized contacts, such as equipotential map
114
B for energized contacts
102
and
106
. The measurement of the signal strength received at the stylus for a particular set of energized contacts may be used to calculate which equipotential line the stylus lies on. The measurement of two sets of energized contacts with substantially orthogonal equipotential lines permits the position of the stylus to be calculated, as indicated by point P of FIG.
3
.
FIG. 4
has similar elements as for
FIG. 3
as applied to a globe having two hemispherical conducting surfaces
701
and
702
. Insulating map surfaces
601
and
602
, containing details of world geography, are shaped to house hemispherical surfaces
701
and
702
. Hemisphere
701
has contacts
710
,
711
, and
712
. Hemisphere
702
has contacts
740
,
741
, and
742
. Switches
770
,
771
,
772
, and
773
along with cables
730
,
750
and leads
760
,
761
of signal generator
722
are configured so that each hemisphere
701
and
701
is driven in a manner similar to that of sheet
100
. However, the equipotential maps for a hemispherical surface energized by two contacts, such as contacts
710
and
711
, is typically more complex than for sheet
100
because of the spherical geometry. Additionally the mathematical algorithms must be calculated in spherical coordinates.
The electrographic appara
Chow Dennis-Doon
LeapFrog Enterprises, Inc.
Nelson Alecia D.
Ross Pepi
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