Electric lamp and discharge devices: systems – Plural power supplies – Plural cathode and/or anode load device
Reexamination Certificate
2001-05-15
2002-07-23
Wong, Don (Department: 2831)
Electric lamp and discharge devices: systems
Plural power supplies
Plural cathode and/or anode load device
C340S870030, C345S173000, C345S206000
Reexamination Certificate
active
06424094
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to color flat panel displays and, more particularly, to an electroluminescent flat panel display with a resistive touch sensitive panel.
BACKGROUND OF THE INVENTION
Modern electronic devices provide an increasing amount of functionality with a decreasing size. By continually integrating more and more capabilities within electronic devices, costs are reduced and reliability increased. Touch screens are frequently used in combination with conventional soft displays such as cathode ray tubes (CRTs), liquid crystal displays (LCDs), plasma displays and electroluminescent displays. The touch screens are manufactured as separate devices and mechanically mated to the viewing surfaces of the displays.
There are three common types of resistive touch screens, 4-wire, 5-wire, and 8-wire. The three types share similar structures.
FIG. 1
a
shows a top view of a resistive touch screen
10
and the external circuitry to which it is connected.
FIG. 1
b
shows a side view of the resistive touch screen
10
. The touch sensitive elements
14
of the resistive touch screen
10
includes a lower circuit layer
20
; a flexible spacer layer
22
containing a matrix of spacer dots
24
; a flexible upper circuit layer
26
; and a flexible top protective layer
28
. All of these layers are transparent. The lower circuit layer
20
comprises conductive materials placed on a substrate
12
, forming a circuit pattern.
The main difference between 4-wire, 5-wire, and 8-wire touch screens is the circuit pattern in the lower circuit layer
20
and in the upper circuit layer
26
, and the means for making resistance measurements. An external controller
18
is connected to the touch screen circuitry via cable
16
. Conductors in cable
16
are connected to the circuitry within the lower circuit layer
20
and the upper circuit layer
26
. The external controller
18
coordinates the application of voltages to the touch screen circuit elements. When a resistive touch screen is pressed, the pressing object, whether a finger, a stylus, or some other object, deforms the top protective layer
28
, the upper circuit layer
26
, and the spacer layer
22
, forming a conductive path at the point of the touch between the lower circuit layer
20
and the upper circuit layer
26
. A voltage, called a touch coordinate voltage, is formed in proportion to the relative resistances in the circuit at the point of touch, and is measured by the external controller
18
connected to the other end of the cable
16
. The controller
18
then computes the (X,Y) coordinates of the point of touch. For more information on the operation of resistive touch screens, see “Touch Screen Controller Tips” by Osgood et al., Application Bulletin AB-158, Burr-Brown, Inc. (Tucson, Arizona).
The external controller
18
is typically an integrated circuit soldered to a printed circuit board
30
. Cable
16
is plugged into a connector
32
that is also soldered to the printed circuit board
30
. The conductors in the cable
16
connect to the external controller
18
via traces that are placed on the printed circuit board
30
that run between the external controller
18
and the connector
32
.
External controller
18
consists of three sub-circuits: a voltage application circuit
34
, a touch detection circuit
36
, and a multiplexing circuit
38
.
The voltage application circuit
34
selects the placement of voltages on the touch screen's electrodes. The touch detection circuit
36
monitors the voltage read from the touch screen, decides when a touch has been performed, and computes the (X, Y) coordinates of the touch point. The (X, Y) coordinates of the touch point are then transferred to another integrated circuit
39
on the circuit board, often a microprocessor. External controllers are available commercially, for example, the ADS7846 by Texas Instruments (Dallas, Tex.).
As shown in
FIG. 2
, the touch detection circuit
36
often contains an analog-to-digital converter
40
and a computation circuit
42
. Analog-to-digital converter
40
converts the analog voltage measured at the point of touch to a digital value. The computation circuit
42
is often an embedded processor or other circuit that can monitor the digital voltage value, detect the presence of a touch based on the voltage value, and compute the coordinate of the touch based on the magnitude of the digital voltage value. Other processing may be performed, such as averaging to minimize noise.
The multiplexing circuit
38
in
FIG. 1
a
determines which conductors in the cable
16
are routed to the voltage application circuit
34
and to the touch detection circuit
36
. This routing changes for determining the X and Y coordinates. The external controller
18
is usually responsive to a clock generated on the printed circuit board
30
, and also has voltage inputs. The cable
16
would contain four conductors for 4-wire touch screens, five conductors for 5-wire touch screens, and eight conductors for 8-wire touch screens. The multiplexing circuit
38
would have two wires going to the voltage application circuit
34
and two wires going to the touch detection circuit
36
for 4-wire touch screens. The multiplexing circuit
38
would have four wires going to the voltage application circuit
34
and one wire going to the touch detection circuit
36
for 5-wire touch screens.
FIG. 3
shows a cross section view of a typical prior art electroluminescent display such as an organic light emitting diode (OLED) flat panel display
70
of the type shown in U.S. Pat. No. 5,937,272, issued Aug. 10, 1999 to Tang. The OLED display includes a substrate
72
that provides mechanical support for the display device, a transistor switching matrix layer
74
, a light emission layer
78
containing materials forming organic light emitting diodes, and a cable
80
for connecting circuitry within the flat panel display to external controller
81
. The substrate
72
is typically glass, but other materials, such as plastic, may be used. The transistor switching matrix layer
74
contains a two-dimensional matrix of thin film transistors (TFTs)
76
that are used to select which pixel in the OLED display that receives image data at a given time. The thin film transistors
76
are manufactured using conventional semiconductor manufacturing processes, and therefore extra thin film transistors
76
may be used to form circuitry for a variety of uses. As mentioned in U.S. Serial No. 09/774,221 filed Jan. 30, 2001, by Peldman et al., the presence of TFTs within an active matrix flat panel display allow functions other than display functions to be implemented on the same substrate as the display function, producing a system-on-panel. The OLED display is responsive to control signals generated by external controller
81
. These control signals typically include a pixel clock (sometimes called a dot clock), a vertical synchronization signal (VSYNC), and a horizontal synchronization (HSYNC) signal.
Conventionally, when a touch screen is used with a flat panel display, the touch screen is simply placed over the flat panel display, and the two are held together by a mechanical mounting means such as a frame.
FIG. 4
shows such an arrangement with a touch screen mounted on an OLED flat panel display. After the touch screen and the OLED display are assembled, the two substrates
12
and
72
are placed together in a frame
82
, often separated by a mechanical separator
84
. The resulting assembly contains two cables
16
and
80
that connect the touch screen and the flat panel display to external controllers
18
(see
FIG. 1
a
) and
81
(see FIG.
3
).
U.S. Serial No. 09/826,194, filed Apr. 4, 2001 by Siwinski et al. proposes a device in which an organic electroluminescent flat panel display is integrated with a touch screen, sharing a common substrate. This invention has advantages over existing touch screen and flat panel display combinations with decreased cost, no integration steps, decreased weight and thickness, and improved optical quality.
As
Close Thomas H.
Tran Thuy Vinh
Wong Don
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