Computer graphics processing and selective visual display system – Display peripheral interface input device – Touch panel
Reexamination Certificate
1997-10-10
2001-04-10
Shankar, Vijay (Department: 2673)
Computer graphics processing and selective visual display system
Display peripheral interface input device
Touch panel
C345S179000, C345S156000, C178S019010, C178S018010
Reexamination Certificate
active
06215476
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to a display screen of a computer system. More specifically, the present invention relates to an electromagnetic pen digitizer that is integrated into a flat panel display.
BACKGROUND OF THE INVENTION
Within a computer system, numerous techniques exist for inputting data and commands from a user to the computer system. One technique is to use a special computer “pen” for entering information via a display screen of a computer system. A user moves the pen around on the screen, inputting or selecting information to be transmitted to the computer system.
A variety of technologies exist for inputting information to a computer system using a pen. One such technique uses a special pen in conjunction with an electromagnetic pen digitizer that is placed behind the display unit of a computer system. By moving the pen around on the glass screen of a display unit, and/or by pressing the pen against the glass screen, the electromagnetic pen digitizer is able to receive information from the pen and transmit this information to the computer system. The pen is able to transmit information using electromagnetic signals that are picked up by antenna on the digitizer. One advantage of using an electromagnetic pen digitizer is that this technology is able to input information from the pen such as its X, Y coordinates on the display, pen button status, the tilt of the pen and the pressure of the pen on the glass screen. Such electromagnetic pen digitizers are especially useful in (but not limited to) flat panel display assemblies of a portable computer.
As shown in
FIG. 1
, electromagnetic pen digitizers to date have been assembled with flat panel displays simply by placing a discrete digitizer implemented using standard printed circuit board technology completely behind the flat panel display (including being behind the diffuser backlight and behind the active display electronics).
FIG. 1
shows a display unit
10
of a computer system having a flat panel display assembly
12
and an electromagnetic pen digitizer
14
. Digitizer
14
is a standard electromagnetic pen digitizer. Display
12
includes viewable area
16
through which information is presented to the user and through which the user may input information, and an outside side area
18
that is not used for presenting or inputting information. In older generations of flat panel displays, side area
18
is relatively large compared to viewable area
16
and incorporates the active display electronics
20
that control the presentation of information on viewable area
16
of display
12
.
As can be seen in
FIG. 2
, active display electronics
20
are located in side area
18
outside of viewable area
16
of display
12
. Thus, because side area
18
is relatively large compared to viewable area
16
, electronics
20
are easily incorporated to the side of viewable area
16
. Thus, electronics
20
do not interfere with the interaction between a special pen moving on viewable area
16
and electromagnetic pen digitizer
14
located behind display
12
. In other words, having electronics
20
to the side of area
16
prevents electronics
20
from interfering with electromagnetic signals between the pen and the digitizer. Such a design for a display unit is workable, although viewable area
16
may be relatively small.
As flat panel display technology moves forward, the overall size of a display unit has been shrinking due to designs in which the active display electronics are located directly behind the viewable area of the display. By locating the active electronics behind the viewable area, space is saved at the sides of a flat panel display assembly and allows for an overall smaller package. Also, as the side areas of a flat panel display assembly are no longer needed to incorporate the active display electronics, the viewable area of the display may also be made larger, with attendant advantages for a user.
FIG. 3
illustrates an example of a display unit in which the active display electronics are placed behind the viewable area of the display. Shown is a display unit
30
having a flat panel display assembly
32
, a viewable area
36
, side area
38
and active display electronics
40
. As electronics
40
are now located directly behind viewable area
36
, side area
38
may now be made much smaller relative to viewable area
36
. Thus, the overall size of display unit
30
may be reduced, or alternatively, the size of viewable area
36
may be increased. Each of these alternatives has various advantages. One technique for locating electronics
40
behind viewable area
36
literally “folds” the electronics in behind viewable area
36
. This technique, often referred to as “bent TAB” or “folded TAB”, uses a printed circuit board attached via flexible ribbon cable (“flex cable”) to the mother glass of the flat panel display assembly. Attached to the flex cable are a number of integrated circuit drivers that are attached using tape-automated bonding (TAB) construction technology. This “bent TAB” technique allows active electronics
40
to be placed behind viewable area
36
. Of course, other techniques aside from “bent TAB” may be used in order to place the active electronics behind a viewable area.
Unfortunately, attempting to place a discrete electromagnetic pen digitizer behind a flat panel display assembly that includes active electronics behind the viewable area is not possible due to the interference of the electromagnetic energy and the electromagnetic shielding induced by the active electronics. In other words, when the active electronics are located directly in front of a discrete electromagnetic pen digitizer, the electromagnetic signals between a pen on the display screen and the digitizer are blocked or distorted by the electronics.
FIG. 4
illustrates a display unit
50
in which this situation occurs. Flat panel display assembly
32
has a viewable area
36
, side areas
38
and active display electronics
40
. Active electronics
40
are located in between viewable area
36
and an electromagnetic pen digitizer
34
. Electronics
40
interfere with communication between pen
52
and digitizer
34
.
Digitizer
34
is basically a sensor panel that includes numerous antenna for receiving a signal from pen
52
, and may also serve as a power source for pen
52
. In operation, digitizer
34
sends an energy pulse to pen
52
which receives power for operation from the energy pulse, or is triggered by the energy pulse to transmit for pen battery systems. Pen
52
is then able to transmit information such as pen button status and pressure to digitizer
34
by broadcasting a relatively weak electromagnetic signal. Digitizer
34
derives location and tilt of the pen by looking at the relative signal strengths from the antennas in the digitizer. Because the signal is relatively weak, electronics
40
create interference. Although various manufacturers have attempted to solve this problem (such as by changing the frequency of the pen, by increasing signal strength via a pen battery, by decreasing maximum pen resolution or by reducing the active pen area), a workable solution for this type of display assembly is yet to be found. Therefore, display units that include a flat panel display assembly along with an electromagnetic pen digitizer are typically only implemented with a small viewable area and a large side area in which the active electronics are incorporated. Large viewable areas of display units such as is shown in
FIG. 3
that are made possible with technologies such as “bent TAB” have proven extremely difficult to use with an electromagnetic pen digitizer.
Other types of digitizers for detecting the location of a pen on a screen are in use, but these have a variety of disadvantages. For example, a resistive membrane may be placed on top of a flat panel display assembly. However, because this membrane is placed on top of the display, less light is transmitted, and more power is needed to increase light from the backlight unit. However, this technique is
Depew John M.
Northway David C.
Apple Computer Inc.
Beyer Weaver & Thomas LLP
Said Mansour M.
Shankar Vijay
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