Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
2002-05-21
2004-10-26
Shalwala, Bipin (Department: 2673)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S100000, C345S098000, C345S087000
Reexamination Certificate
active
06809719
ABSTRACT:
BACKGROUND OF INVENTION
1. Field of the Invention
The present invention relates to a scan line driving method for a thin film transistor liquid crystal display (TFT LCD). More particularly, the present invention discloses a method that enables the simultaneous driving of two scan lines in a TFT LCD.
2. Description of the Prior Art
Thin film transistor liquid crystal displays (TFT LCD) are thin, flat panel display devices that can be found in a plethora of electronic goods, ranging from notebook computers and digital cameras, to flight avionics and medical diagnostic tools. TFT LCDs offer crisp, high-resolution images, and have the primary advantage of offering relatively low power-consumption rates while still maintaining good color contrast and screen refresh rates.
Please refer to FIG.
1
.
FIG. 1
is a simple block diagram of a TFT LCD
10
. The TFT LCD
10
is composed of a plurality of pixels
12
that are regularly arrayed in a rectangular manner, forming rows
10
R and columns
10
C of pixels
12
. A particular pixel
12
consequently has a location within the TFT LCD
10
that may be referenced in a Cartesian manner by the row
10
R and column
10
C in which that particular pixel
12
is located.
Please refer to
FIG. 2
with reference to FIG.
1
.
FIG. 2
is an equivalent circuit diagram
20
for the TFT LCD
10
. Each pixel
12
has a circuit equivalent of a driving transistor (TFT)
24
and two capacitors
22
a
and
22
b
, which are electrically connected between the driving transistor
24
and a common electrode
26
. The common electrodes
26
may be thought of as a sort of ground, common to all of the pixels
12
. Capacitor
22
a
is a circuit equivalent of the TFT array substrate that is used to form the pixels
12
. Generally speaking, the capacitor
22
a
is insufficiently large to maintain a driving voltage of the pixel
12
for a suitable length of time. Hence, capacitor
22
b
is provided so that the liquid crystal in the pixel
12
is able to retain the charge associated with a first driving signal until a second driving signal is received. Each driving transistor
24
is further connected to a scan line
28
R and to a data line
28
C. Each row
10
R has a respective scan line
28
R, and each column
10
C has a respective data line
28
C. All driving transistors
24
in the same row
10
R are connected to the same respective scan line
28
R. Similarly, all driving transistors
24
in the same column
28
C are connected to the same respective data line
28
C. As noted above, each pixel
12
has a unique address given in row
10
R and column
10
C coordinates. To turn on or turn off a pixel
12
, an appropriate voltage is placed upon the data line
28
C corresponding to the column
10
C in which the pixel
12
is located, and a scanning voltage is placed upon the scan line
28
R corresponding to the row
10
R in which the pixel
12
is located, which activates the driving transistor
24
of the pixel
12
to charge or discharge the capacitors
22
a
and
22
b
according to the voltage placed upon the data line
28
C. Changing the voltage across the capacitors
22
a
and
22
b
attenuates the visual characteristics of the pixel
12
, and in this manner the entire display
10
may be changed at will on a pixel-by-pixel basis.
Due to leakage currents, the capacitors
22
a
and
22
b
must be regularly refreshed to maintain their appropriate voltages, and hence maintain the display integrity of the TFT LCD
10
. Typically, this is performed at something like 60 times per second, and is performed a row
10
R at a time. Data line drivers
29
C are energized according to the display characteristics of each respective pixel
12
in a selected row
10
R to activate the data lines
28
C. The scan line
28
R for the row
10
R is then activated by scan line circuitry
29
R, while all other scan lines
28
R are kept in an inactive state. An entire row
10
R is thus written to at once, and the process is repeated for a succeeding row. Note that it is not possible to simultaneously write to two or more rows
10
R at a time, as a single signal data line
28
C is used to drive a plurality of column pixels
12
. When performing the refreshing process, sufficient time must not only be allowed for the charging/discharging of the capacitors
22
a
and
22
b
, but also for the settling of the data drivers
29
C. Rapid activation of scan lines
28
R before the data lines
29
C have settled can lead to inappropriate values being written into the capacitors
22
a
and
22
b
within a row
10
R, leading to image degradation of the TFT LCD
10
. Similarly, allowing insufficient time for the charging of the capacitors
22
a
,
22
b
will lead to an inappropriate voltage across the capacitors
22
a
,
22
b
, and thus to image degradation. Consequently, signal timing for the data lines
28
C and scan lines
28
R is very important.
As resolutions increase (i.e., the number of rows
10
R and columns
10
C increases), it becomes more and more difficult to refresh the TFT LCD
10
, as the same amount of time (i.e., {fraction (1/60)}
th
of a second) must be divided over more and more rows
10
R. This leaves less and less time for the settling of the data drivers
29
C (which have to drive greater numbers of pixels
12
), and for the actual refreshing of the capacitors
22
a
,
22
b
. Several solutions have been proposed that have enabled TFT LCDs to support increasingly higher numbers of pixels, such as U.S. Pat. No. 6,081,250, which is incorporated herein by reference. However, in the proposal of U.S. Pat. No. 6,081,250, the data driving circuit has a special design that is not compatible with conventional data drivers.
SUMMARY OF INVENTION
It is therefore a primary objective of this invention to provide a driving method and associated TFT LCD that enables extended row scanning durations. It is a further objective of this invention to provide simplified scan line circuitry in a TFT LCD.
Briefly summarized, the preferred embodiment of the present invention discloses a driving method and an associated thin film transistor liquid crystal display (TFT LCD). The driving method utilizes a TFT LCD comprising a plurality of pixels arrayed as a plurality of rows and a plurality of columns. For a first pixel located at a first row, first column position (R
1
, C
1
), and a second pixel located at a second row, the first column position (R
2
, C
1
), the first pixel is addressable by a first scan line corresponding to the first row (R
1
), and a first data line corresponding to the first column (C
1
), and the second pixel is addressable by a second scan line corresponding to the second row (R
2
), and a second data line corresponding to the first column (C
1
). The method comprises setting the first data line to a first pre-determined voltage corresponding to a desired display state of the first pixel. The second data line is set to a second pre-determined voltage corresponding to a desired display state of the second pixel. Subsequently, the first scan line and the second scan line are simultaneously set to a scan voltage. To effect this, the first scan line and the second scan line share the same scan line driver.
It is an advantage of the present invention that by providing for the simultaneous activation of two scan lines, extended row scan line durations are made possible, while also simplifying the scan line driving circuitry.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment, which is illustrated in the various figures and drawings.
REFERENCES:
patent: 4842371 (1989-06-01), Yasuda et al.
patent: 6081250 (2000-06-01), Shimada et al.
patent: 6380919 (2002-04-01), Koyama et al.
patent: 6545655 (2003-04-01), Fujikawa
patent: 6583777 (2003-06-01), Hebiguchi et al.
patent: 6630921 (2003-10-01), Janssen et al.
patent: 2001/0052888 (2001-12-01), Hebiguchi
patent: 2002/0140691 (2002-10-01), Sato et al.
patent: 2002/0180670 (2002-12-01), Kim
Ting Chin-Lung
Wu Cheng-I
Chi Mei Optoelectronics Corporation
Hsu Winston
Osorio Ricardo
Shalwala Bipin
LandOfFree
Simultaneous scan line driving method for a TFT LCD display does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Simultaneous scan line driving method for a TFT LCD display, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Simultaneous scan line driving method for a TFT LCD display will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3322554