Liquid crystal display

Details Liquid crystal display Liquid crystal display

2000-09-19

2003-06-17

Wu, Xiao (Department: 2674)

Computer graphics processing and selective visual display system

Plural physical display element control system

Display elements arranged in matrix

C345S088000, C345S690000

Reexamination Certificate

active

06580410

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid crystal display used for a display screen of a computer and the like.
2. Description of the Related Art
FIG. 15
is a circuit diagram of a conventional liquid crystal display which includes a control signal generation circuit
1
, a grayscale voltage generation circuit
2
, source driving circuits
3
, gate driving circuits
4
, a liquid crystal panel
5
and TFTs
6
. The liquid crystal panel
5
has a plurality of source lines
5
a
and a plurality of gate lines
5
b
. The control signal generation circuit
1
receives color signal inputs Ri, Gi and Bi, a clock input CLKi and a synchronization signal input Synci and provides color signal outputs Ro, Go and Bo, a clock output CLKo and a synchronization signal output Synco. For example, each of the color signal inputs Ri, Gi and Bi and color signal outputs Ro, Go and Bo is constituted by four bits and is illustrated with an indication “<
3
;
0
>” to represent the four bits. “<
3
;
0
>” represents four bits from a third bit through a 0-th bit. The grayscale voltage generation circuit
2
generates grayscale voltages Vref. The source driving circuits
3
drive the source lines
5
a
in accordance with the color signal outputs Ro, Go and Bo from the control signal generation circuit
1
and the grayscale voltages Vref from the grayscale voltage generation circuit
2
. The gate driving circuits
5
drive the gate lines
5
b
in accordance with the synchronization signal output Synco from the control signal generation circuit
1
. The liquid crystal panel
5
has the multiplicity of TFTs
6
in the form of a matrix which are connected to each of the plurality of gate lines
5
b
and the plurality of source lines
5
a
provided in an intersecting relationship with the gate lines
5
b.
FIG. 16
is a characteristic diagram showing the relationship between the grayscale voltages and luminance of the conventional liquid crystal display, and a characteristic A
0
represents the relationship between the grayscale voltages Vref from the grayscale voltage generation circuit
2
and the luminance of the liquid crystal panel
5
.
FIG. 17
is a characteristic diagram showing the relationship between grayscale data and the grayscale voltages of the conventional liquid crystal display, and a characteristic BO represents the relationship between grayscale data represented by the color signal outputs Ro, Bo and Go from the control signal generation circuit
1
and the grayscale voltages Vref. In this example, each of the color signal outputs Ro, Go and Bo is constituted by four bits, and the 4-bit configuration provides 16 types of grayscale data and the grayscale voltage Vref at 16 levels associated therewith.
FIG. 18
is a characteristic diagram showing the relationship between the grayscale data and the luminance of the liquid crystal panel of the conventional liquid crystal display, and a characteristic C
0
represents such a relationship.
FIG. 19
is a characteristic diagram showing an example of a modification of the relationship between the grayscale data and luminance of the conventional liquid crystal display, in which the characteristic C
0
is changed to a characteristic C
1
or C
2
.
FIG. 20
is a characteristic diagram-showing the relationship between the grayscale data and grayscale voltages of the conventional liquid crystal display and, for example, it shows the relationship between the grayscale data and grayscale voltage Vref when the characteristic B
0
is changed to a characteristic B
1
.
FIG. 21
shows another example of a conventional liquid crystal display which includes a plurality of grayscale voltage generation circuits
2
a
,
2
b
and
2
c.
Referring to
FIG. 21
, the parts represented by the reference number
1
and the reference numbers
3
through
6
are identical to those in FIG.
15
. The grayscale voltage generation circuit
2
includes three grayscale voltage generation circuits
2
a
,
2
b
and
2
c
for changing the relationship between the grayscale voltage and luminance of the liquid crystal display. Reference number
7
represents a selection circuit which selects one of the outputs of the plurality of grayscale voltage generation circuits
2
a
,
2
b
and
2
c.
In the conventional liquid crystal display as shown in
FIG. 15
, in order to achieve multi-level color display, grayscale voltages at predetermined levels are selected from among grayscale voltages at a plurality of levels generated by the grayscale voltage generation circuit
2
based on input digital image data; the grayscale voltages are supplied to the TFTs
6
at the liquid crystal panel
6
through the source driving circuits
3
; and an image is displayed by applying the grayscale voltages to the liquid crystal.
For example, in the case of a normally white liquid crystal, an increase in the grayscale voltage applied to the liquid crystal results in a reduction in luminance as indicated by the characteristic A
0
in FIG.
16
. The grayscale data are digital data, and the grayscale voltages are selected on a digital basis.
FIG. 17
represents the relationship between grayscale data at 16 levels and grayscale voltages as the characteristic B
0
in order to provide a simple description of the selection of grayscale voltages on a digital basis. The grayscale voltage generation circuit
2
generates grayscale signals V
0
through V
15
which are selected based on grayscale data. As a result, the grayscale display characteristic C
0
shown in
FIG. 18
is provided which is represented by a grayscale data-luminance curve.
FIG. 18
omits representation on a digital basis and schematically shows a grayscale display characteristic relative to input grayscale data.
Most conventional liquid crystal displays have a fixed grayscale display characteristic. However, there is a need for a capability of arbitrarily changing the grayscale display characteristic of a display as shown in
FIG. 19
to achieve optimum display in accordance with the preference of the user of the display and the environment in which the display is used.
In the case of a liquid crystal display in which grayscale voltages are selected based on digital data, however, the grayscale voltages must be changed, for example, as shown in
FIG. 20
, which results in a need for a complicated analog circuit for generating the voltages.
Further, a plurality of grayscale voltage generation circuits
2
may be provided to allow grayscale display characteristics to be changed based on selection at a selection circuit
7
, as shown in FIG.
21
. However, this also results in a complicated circuit and can increase the cost.
The invention was made in order to solve the abovedescribed problems, and it is an object of the invention to provide a liquid crystal display whose grayscale display characteristic can be arbitrarily changed to achieve optimum display in accordance with the preference of the user and the environment in which the display is used.
SUMMARY OF THE INVENTION
A liquid crystal display according to the invention has: a circuit which includes a data conversion circuit for converting digital image input data based on arbitrary algorithm and which outputs digital image output data based on the output of the data conversion circuit; a grayscale voltage generation circuit which outputs grayscale voltages at a plurality of levels; source driving circuits which receive the digital image output data and grayscale voltages and which select and output a grayscale voltage at one level from among the grayscale voltages in accordance with the digital image output data; and a display portion which is configured so as to display an image as a result of the application of the grayscale voltage output by the source driving circuits to a liquid crystal thereof. The data conversion circuit converts the digital image input data so as to change a grayscale display characteristic of the image displayed at the display portion.
There may be provided a plurality,of algorithm defining circuits each of

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