Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
2001-09-06
2004-10-05
Mengistu, Amare (Department: 2673)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S096000, C345S690000, C348S254000, C348S255000
Reexamination Certificate
active
06801179
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to video display devices. The present invention specifically relates to a construction of gamma lookup tables for providing inversion flicker compensation to a liquid crystal display device.
2. Description of the Related Art
FIG. 1
illustrates a conventional LCD device
13
for transmitting a luminous output
14
in response to voltage drive signals V
AS4-AS6
in analog form.
FIG. 2
illustrates an exemplary luminance transmission percentage of luminous output
14
in terms of a red color component, a green color component, and a blue color component as a function of various levels of voltage drive signals V
AS4-AS6
. As known in the art, each drive voltage signal V
AS4-AS6
is applied to each column (not shown) of corresponding LCD panels (not shown) of LCD device
13
. Each column is connected via a transistor (not shown) to each pixel (not shown) in each row (not shown) of each LCD panel. LCD device
13
also includes a top plate (not shown) known as a counter electrode for each LCD panel. Each counter electrode receives a voltage reference signal V
REF
in analog form.
For the liquid crystal material within each pixel of each LCD panel to operate properly, the level of drive voltage signals V
AS4-AS6
are modulated relative to voltage reference signal V
REF
. For example, if voltage reference signal V
REF
has a level of six (6) volts, then the levels of voltage drive signals V
AS4-AS6
traverse a range from zero (0) volts to twelve (12) volts as shown in
FIG. 2. A
low inversion polarity range for voltage drive signals V
AS4-AS6
is between zero (0) volts and six (6) volts. A high inversion polarity range for voltage drive signals V
AS4-AS6
is between six (6) volts and twelve (12) volts. Frame inversion implies the levels of voltage drive signals V
AS4-AS6
are within the low inversion polarity range for one video frame, the levels of voltage drive signals V
AS4-AS6
are within the high inversion polarity range for a successive video frame, and so on, and so on.
Gamma circuit
10
includes conventional gamma lookup tables (not shown) for facilitating a reception of voltage drive signals V
AS4-AS6
by LCD device
13
whereby, as shown in
FIG. 3
, LCD device
13
transmits luminous output
14
at a desired luminance response as related to voltage data signal V
DS1-DS3
in digital form. Voltage data signal V
DS1-DS3
are indicative of a particular gray level input from a conventional video source (not shown) as related to the red color component, the green color component, and the blue color component, respectively. For example, voltage data signal V
DS1-DS3
can consist of eight bits representing 256 gray levels over a range of 00000000 (normalized as 0 in
FIG. 3
) to 11111111 (normalized as 1 in FIG.
3
).
In response to a reception of voltage data signal V
DS1-DS3
, gamma circuit
10
obtains levels for voltage drive signals V
AS4-AS6
for the low inversion polarity range that corresponds to the levels of voltage data signal V
DS1-DS3
, respectively. A digital-to-analog converter (DAC)
11
transform voltage data signal V
DS1-DS3
to voltage drive signals V
AS1-AS3
, respectively, in analog form that is only provided with levels within the low inversion polarity range based on an average luminance response of luminous output
14
in both inversion polarity ranges. Thus, to achieve frame inversion, a voltage inversion circuit
12
provides voltage drive signals V
AS4-AS6
in response to voltage drive signals V
AS1-AS3
, respectively, with the levels of voltage drive signals V
AS4-AS6
being within the low inversion polarity range (e.g., equating control voltage V
AS1
) for one video frame, the levels of voltage drive signals V
AS4-AS6
being within the high inversion polarity range (e.g., (2*V
REF
)−V
AS1
) for a successive video frame, and so on, and so on.
Luminous output
14
experiences an inversion flicker whenever one or more voltage drive signals V
AS4-AS6
are attenuated prior to being applied to the appropriate pixels with LCD device
13
. As known in the art, such attenuation typically occurs within conventional LCD device
13
whenever levels of voltage drive signals V
AS4-AS6
are within the high inversion polarity range. Consequently, as exemplary illustrated in
FIG. 4
, a time-based amplitude measurement of luminous output
14
as related to each gray level input indicated by the levels of the voltage data signals V
DS1-DS3
would exhibit uneven peaks relative to an average luminous response of luminous output
14
with the uneven peaks being representative of the inversion flicker.
Clearly, a disadvantage of employing gamma circuit
10
, DAC
11
, and voltage inversion circuit
12
to drive LCD device
13
is the failure to compensate for any occurrence of an inversion flicker of luminous output
14
. Therefore, there is a need to provide a method and a device for eliminating inversion flicker within LCD device
13
. The present invention addresses this need.
SUMMARY OF THE INVENTION
The present invention relates to a method and a device for eliminating inversion flicker within a LCD device. Various aspects of the present invention are novel, non-obvious, and provide various advantages. While the actual nature of the present invention covered herein can only be determined with reference to the claims appended hereto, certain features, which are characteristic of the embodiments disclosed herein, are described briefly as follows.
A first form of the present invention is a device comprising a LCD device operable to emit a luminous output in response to a reception of a voltage drive signal and a voltage reference signal. The device further comprises a display driver operable to provide the voltage drive signal to the LCD device in response to a reception of a voltage data signal having a data voltage level indicative of a gray level. The display driver includes a gamma lookup table for the voltage drive signal with the gamma lookup table listing a pair of drive voltage levels for the voltage drive signal that correspond to the gray level as indicated by a data voltage level of the voltage data signal. The drive voltage levels for the voltage drive signal have opposing polarities relative to a reference voltage level of the voltage reference signal.
A second form of the present invention is a method for applying an inversion flicker compensation to a luminous output being emitted by a liquid crystal display device in response to a reception of a voltage drive signal and a voltage reference signal. First, a display driver is operated to receive a voltage data signal having a data voltage level indicative of a first gray level. Second, the display driver is operated to obtain a pair of drive voltage levels for the voltage drive signal in response to the reception of the voltage data signal having the data voltage level. The pair of drive voltage levels having opposing polarities relative to a reference voltage level of the voltage reference signal. Finally, the display driver is operated to provide the voltage drive signal to the liquid crystal display device in a frame inversion manner involving the pair of drive voltage levels during a duration of the data voltage level indicating the first gray level.
The foregoing forms and other forms, features and advantages of the present invention will become further apparent from the following detailed description of the presently preferred embodiments, read in conjunction with the accompanying drawings. The detailed description and drawings are merely illustrative of the present invention rather than limiting, the scope of the present invention being defined by the appended claims and equivalents thereof.
REFERENCES:
patent: 5604511 (1997-02-01), Ohi
patent: 5748171 (1998-05-01), Ishizaki et al.
patent: 5754150 (1998-05-01), Matsui
patent: 5847688 (1998-12-01), Ohi et al.
patent: 6049321 (2000-04-01), Sasaki
patent: 6144354 (2000-11-01), Koyama et al.
patent: 0915453 (1999-05-01), None
patent: 0917128 (1999-05-0
Koninklijke Philips Electronics , N.V.
Mengistu Amare
Sheng Tom
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