U.S. patent application number 12/039807 was filed with the patent office on 2008-10-02 for hold type image display system.
This patent application is currently assigned to NEC LCD TECHNOLOGIES, LTD.. Invention is credited to Hiroaki KIMURA.
Application Number | 20080238897 12/039807 |
Document ID | / |
Family ID | 39995934 |
Filed Date | 2008-10-02 |
United States Patent
Application |
20080238897 |
Kind Code |
A1 |
KIMURA; Hiroaki |
October 2, 2008 |
HOLD TYPE IMAGE DISPLAY SYSTEM
Abstract
The present invention aims to prevent display luminance
difference and burning with a line at which the polarity inversion
switches when the order of inversion of black and video changes in
the middle of the screen by a frame polarity inversion drive in a
liquid crystal display device for performing black insertion drive.
An enable signal (VOE) to each gate driver 5A to 5N is
independently controlled, a start pulse (VSP) input to write a
black signal is performed at an arbitrary timing within one frame
period with respect to the gate driver 5A to insert a black image
within one frame period, a write polarity of the video signal is
inverted in frame cycle with the video display start pulse as a
base point, and a write polarity of the black image signal is
inverted in frame cycle with the black display start pulse as a
base point.
Inventors: |
KIMURA; Hiroaki; (Kanagawa,
JP) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W., SUITE 800
WASHINGTON
DC
20037
US
|
Assignee: |
NEC LCD TECHNOLOGIES, LTD.
Kanagawa
JP
|
Family ID: |
39995934 |
Appl. No.: |
12/039807 |
Filed: |
February 29, 2008 |
Current U.S.
Class: |
345/204 ;
345/87 |
Current CPC
Class: |
G09G 3/3666 20130101;
G09G 2320/0257 20130101; G09G 2320/062 20130101; G09G 2320/046
20130101; G09G 3/3614 20130101; G09G 2310/024 20130101; G09G 3/36
20130101; G09G 3/342 20130101; H04N 5/66 20130101; G09G 2320/0261
20130101; G09G 2320/106 20130101; G09G 2310/061 20130101 |
Class at
Publication: |
345/204 ;
345/87 |
International
Class: |
G09G 5/00 20060101
G09G005/00; G09G 3/36 20060101 G09G003/36 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 29, 2007 |
JP |
2007-086191 |
Feb 20, 2008 |
JP |
2007-039352 |
Claims
1. A hold type image display system for displaying a video on a
display panel by controlling a video signal to be input to a source
line and a gate line of the display panel, the hold type image
display system comprising: a source driver for outputting a video
signal to the source line; a gate driver for outputting a scanning
signal to the gate line; and a controller for receiving an input
video signal and thereby controlling the source driver and the gate
driver; wherein the controller outputs a video signal in which a
black or gray line is inserted between video lines to the source
driver, outputs a start pulse signal for writing the video lines
for one or more times and a start pulse signal for writing black or
gray lines for one or more times to the gate driver within one
frame period, and inverts a write polarity of the video signal and
a write polarity of the black or gray signal in frame cycle; and
the controller scrolls a black band in a screen of the display
panel during one frame.
2. The hold type image display system according to claim 1, wherein
the controller inverts the write polarity of the video signal with
a point of writing the video signal to a first line of the frame as
a base point, and inverts the write polarity of the black or gray
signal with a point of writing the black or gray signal to the
first line of the frame as a base point.
3. The hold type image display system according to claim 1, wherein
the controller changes a timing of input of the start pulse signal
to the gate driver to write the black or gray lines with respect to
input of the start pulse signal to the gate driver to write the
video signal based on black or gray insertion rate information.
4. The hold type image display system according to claim 1, wherein
the controller determines a black or gray insertion rate according
to a display, and changes a timing of input of the start pulse
signal to the gate driver to write the black or gray lines with
respect to input of the start pulse signal to the gate driver to
write the video lines based on the determined black or gray
insertion rate.
5. The hold type image display system according to claim 1, wherein
the controller outputs the black or gray line signals to the source
driver during a blanking period existing between preceding and
following frame periods.
6. The hold type image display system according to claim 1, further
comprising a backlight on a rear surface of the display panel;
wherein the controller compares the preceding and following video
signals in one frame unit, and adjusts a relationship between a
black or gray insertion rate and a light control luminance of the
backlight based on the comparison result.
7. A control system of a hold type image display system for drive
displaying a video on a display panel by controlling a video signal
to a source line of the display panel in a source driver and
controlling a signal to a gate line of the display panel in a gate
driver; the control system comprising: a controller for receiving
an input video signal and thereby controlling the source driver and
the gate driver; wherein the controller outputs a video signal in
which a black or gray line is inserted between video lines to the
source driver, outputs a start pulse signal for writing the video
lines for one or more times and a start pulse signal for writing
black or gray lines for one or more times to the gate driver within
one frame period, and inverts a write polarity of the video signal
and a write polarity of the black or gray signal in frame cycle;
and the controller scrolls a black band in a screen of the display
panel during one frame.
8. The control system of the hold type image display system
according to claim 7, wherein the controller inverts the write
polarity of the video signal with a point of writing the video
signal to a first line of the frame as a base point, and inverts
the write polarity of the black or gray signal with a point of
writing the black or gray signal to the first line of the frame as
a base point.
9. The control device of the hold type image display system
according to claim 7, wherein the controller changes a timing of
input of the start pulse signal to the gate driver to write the
black or gray lines with respect to input of the start pulse signal
to the gate driver to write the video lines based on black or gray
insertion rate information.
10. The control device of the hold type image display system
according to claim 7, wherein the controller determines a black or
gray insertion rate according to a display, and changes a timing of
input of the start pulse signal to the gate driver to write the
black or gray lines with respect to input of the start pulse signal
to the gate driver to write the video lines based on the determined
black or gray insertion rate.
11. The control device of the hold type image display system
according to claim 10, wherein the controller outputs the black or
gray line signals to the source driver during a blanking period
existing between preceding and following frame periods.
12. The control device of the hold type image display system
according to claim 7, wherein the controller compares the preceding
and following image signals in one frame unit, and adjusts a
relationship between a light control luminance of a backlight
arranged on a rear surface of the display panel and the black or
gray insertion rate based on the comparison result.
13. A hold type image display method for displaying a video on a
display panel by controlling a video signal to a source line of a
display panel in a source driver and controlling a signal to a gate
line of the display panel in a gate driver, the hold type image
display method comprising: outputting a video signal in which a
black or gray line is inserted between video lines to the source
driver; outputting a start pulse signal for writing the video lines
for one or more times and a start pulse signal for writing black or
gray lines for one or more times to the gate driver within one
frame period; scrolling a black band in a screen of the display
panel during one frame; and inverting a write polarity of the video
signal and a write polarity of the black or gray signal in frame
cycle.
14. The hold type image display method according to claim 13,
wherein the write polarity of the video signal is inverted with a
point of writing the video signal to a first line of the frame as a
base point, and the write polarity of the black or gray signal is
inverted with a point of writing the black or gray signal to the
first line of the frame as a base point.
15. The hold type image display method according to claim 13,
wherein a timing of input of the start pulse signal to the gate
driver to write the black or gray lines with respect to input of
the start pulse signal to the gate driver to write the video lines
is changed based on black or gray insertion rate information.
16. The hold type image display method according to claim 13,
wherein a black or gray insertion rate is determined according to a
display, and a timing of input of the start pulse signal to the
gate driver to write the black or gray lines with respect to input
of the start pulse signal to the gate driver to write the video
lines is changed based on the determined black or gray insertion
rate.
17. The hold type image display method according to claim 13,
wherein the black or gray line signals are output to the source
driver during a blanking period existing between preceding and
following frames periods.
18. The hold type image display method according to claim 13, the
preceding and following video signals of one frame unit are
compared, and a relationship between a light control luminance of
backlight arranged on a rear surface of the display panel and a
black or gray insertion rate is adjusted based on the comparison
result.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from Japanese patent application No. 2007-086191, filed on
Mar. 29, 2007, and Japanese patent application No. 2008-039352,
filed on Feb. 20, 2008, the disclosure of which is incorporated
herein in its entirety by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to image display devices and
image display methods thereof, and image display programs, in
particular, to a hold type image display system.
[0004] 2. Description of the Related Art
[0005] A liquid crystal display (LCD) is being widely used since it
is thin and does not occupy as much installation area compared to a
CRT (Cathode Ray Tube) display. However, in the hold type display
device such as LCD, an image is continued through a frame period as
opposed to an impulse type display device such as CRT display, and
thus a moving image tends to become unclear.
[0006] In the case of the impulse type display device, an image is
displayed as a pulse at an early stage in the frame and a black
display is displayed until the next frame, and thus the afterimage
occurrence is adjusted not to be recognized by the user's eyes. In
the case of the hold type display device, on the other hand, the
image is held and displayed as a still image within the frame
period, and the moving image is displayed by switching the screen
for every frame, and thus the still image is seamlessly switched
from one frame to another, whereby the user recognizes the previous
frame image as an afterimage, senses a double image in which the
shifted images are overlapped and recognizes a moving image blur.
In order to reduce the moving image blur in the hold type display
device, a hold type display device for pseudo-driving in an impulse
type display is disclosed in Japanese Patent Publication No.
3385530 (patent document 1) and Japanese Laid-Open Patent
Publication No. 2001-166280 (patent document 2).
[0007] Since the liquid crystal generally deteriorates when a
direct current component is applied to the liquid crystal over a
long period of time in the liquid crystal display device, a frame
inversion drive of inverting the voltage polarity applied to the
pixel for every frame is performed.
[0008] However, in most liquid crystal display devices
pseudo-driven in the impulse type display, a black signal and a
video signal are alternately written to each pixel at a constant
cycle, and thus only the black signal is written in one polarity
and only the video signal is written in the other polarity if the
cycle of inversion drive and the cycle of black insertion coincide,
whereby the DC component is applied to the liquid crystal panel
causing burning of the liquid crystal panel and degradation in
lifetime.
[0009] In the method disclosed in patent document 1, in order to
improve such drawbacks, the polarity is inverted at a cycle of
double the cycle of black insertion in the black insertion drive of
alternately repeating the black signal and the video signal for
every frame. In the case of the black insertion drive repeated for
every frame, to which pixel of the display screen each black signal
is used can be easily defined, and thus burning of the liquid
crystal panel and degradation in lifetime can be avoided by forming
a sequence with the switching of the frames of the video signal as
a base point.
[0010] However, in the display device of patent document 2
configured as shown in FIG. 18, since the black insertion drive of
inserting the black image at a specific proportion within one frame
is performed, to which pixel of the display screen the black signal
is used differs depending on a black insertion rate, and the black
signal is positioned in the middle of the display screen at the
switching of the frames of the video signal, whereby it is
difficult to form a sequence of inversion with the switching of the
frames of the video signal as the base point.
[0011] Patent document 1 discloses a method of inverting the
polarity for every two outputs of the video signal and the black
signal following thereto, where if such method is used in the
device of patent document 2, the order of inversion of the black
signal and the video signal changes at the middle of the screen, as
shown in FIG. 19, whereby luminance difference and burning might
occur at the display with a line as a boundary at which the
polarity inversion switches according to variation in field through
of the panel surface and variation in positive and negative of the
application voltage (see FIG. 20).
[0012] It is an exemplary object of the present invention to
provide a hold type image display system capable of flexibly
responding to switching of black insertion rate, and capable of
preventing display luminance difference and burning at the line at
which the polarity inversion switches as a boundary.
SUMMARY OF THE INVENTION
[0013] To achieve the exemplary object, a hold type image display
system according to an exemplary aspect of the invention relates to
a hold type image display system for displaying a video on a
display panel by controlling a video signal to be input to a source
line and a gate line of the display panel, the hold type image
display system including a source driver for outputting a video
signal to the source line; a gate driver for outputting a scanning
signal to the gate line; and a controller for receiving an input
video signal and thereby controlling the source driver and the gate
driver; wherein the controller outputs a video signal in which a
black or gray line is inserted between video lines to the source
driver, outputs a start pulse signal for writing the video lines
for one or more times and a start pulse signal for writing black or
gray lines for one or more times to the gate driver within one
frame period, inverts a write polarity of the video signal and a
write polarity of the black or gray signal in frame cycle, and
scrolls a black band in a screen of the display panel during one
frame.
[0014] A control system of the hold type image display system
according to another exemplary aspect of the invention relates to a
control system of a hold type image display system for displaying a
video on a display panel by controlling a video signal to a source
line of the display panel in a source driver and controlling a
signal to a gate line of the display panel in a gate driver; the
control system including a controller for receiving an input video
signal and thereby controlling the source driver and the gate
driver; wherein the controller outputs a video signal in which a
black or gray line is inserted between video lines to the source
driver, outputs a start pulse signal for writing the video lines
for one or more times and a start pulse signal for writing black or
gray lines for one or more times to the gate driver within one
frame period, inverts a write polarity of the video signal and a
write polarity of the black or gray signal in frame cycle, and
scrolls a black band in a screen of the display panel during one
frame.
[0015] A hold type image display method according to still another
exemplary aspect of the invention relates to a hold type image
display method for displaying a video on a display panel by
controlling a video signal to a source line of a display panel in a
source driver and controlling a signal to a gate line of the
display panel in a gate driver, the hold type image display method
including the steps of outputting a video signal in which a black
or gray line is inserted between video lines to the source driver;
outputting a start pulse signal for writing the video lines for one
or more times and a start pulse signal for writing black or gray
lines for one or more times to the gate driver within one frame
period; scrolling a black band in a screen of the display panel
during one frame; and inverting a write polarity of the video
signal and a write polarity of the black or gray signal in frame
cycle.
[0016] A control program of the hold type image display system
according to still another exemplary aspect of the invention
relates to a control program of a hold type image display system
for displaying a video on a display panel by controlling a signal
to a source line of a display panel in a source driver and
controlling a signal to a gate line of the display panel in a gate
driver, the control program of the hold type image display causing
a computer to execute a function of outputting a video signal in
which a black or gray line is inserted between video lines to the
source driver; a function of outputting a start pulse signal for
writing the video lines and a start pulse signal for writing black
or gray lines to the gate driver; a function of inverting a write
polarity of the video signal and a write polarity of the black or
gray signal in frame cycle; and a function of scrolling a black
band in a screen of the display panel during one frame.
[0017] As an exemplary advantage according to the invention, the
present invention can finely adjust the black image insertion rate
with respect to one frame period while taking into consideration
the balance between the merit of reducing the moving image blur and
the demerit of lowering in luminance in the hold type display
device, and display luminance difference and burning having a line
at which the polarity inversion switches as a boundary caused by
variation in field through of the display panel surface and
variation in positive and negative of application voltage are
prevented.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1A is a view showing a configuration of an image
display device of a first exemplary embodiment according to the
present invention, FIG. 1B is a cross sectional view showing a
configuration of a pixel, and FIG. 1C is a view showing another
configuration example of a controller;
[0019] FIG. 2 is an explanatory view showing a step of creating a
black insertion image signal in the exemplary embodiment shown in
FIG. 1A;
[0020] FIG. 3 is a view showing a polarity of each pixel when a dot
inversion drive is adopted;
[0021] FIG. 4 is a view showing a polarity of each pixel when a
vertical 2-dot inversion drive is adopted;
[0022] FIG. 5 is a view showing a polarity of each pixel when
another example of the vertical 2-dot inversion drive is
adopted;
[0023] FIG. 6 is a timing chart showing one example of a frame
polarity inversion drive in the image display device of the
exemplary embodiment shown in FIG. 1A;
[0024] FIGS. 7A and 7B are timing charts of a signal propagating
through the image display device of the exemplary embodiment shown
in FIG. 1A;
[0025] FIG. 8 is an explanatory view showing the operation of the
image display device of the exemplary embodiment shown in FIG.
1A;
[0026] FIGS. 9A and 9B are explanatory views showing a moving image
display in the image display device of the exemplary embodiment
shown in FIG. 1A;
[0027] FIG. 10 is an explanatory view showing the operation of the
image display device of the exemplary embodiment shown in FIG.
1A;
[0028] FIG. 11 is an explanatory view showing another example of
the step of creating a black insertion image signal in the
exemplary embodiment shown in FIG. 1A;
[0029] FIG. 12 is a view showing a configuration of an image
display device according to a second exemplary embodiment of the
present invention;
[0030] FIG. 13 is a flowchart showing the operation of a black
insertion rate setting unit according to the exemplary embodiment
shown in FIG. 12;
[0031] FIG. 14 is a view showing relation characteristics of the
black image insertion rate, and the moving image blur and
transmissive efficiency in the display panel of the present
invention;
[0032] FIG. 15 is a view showing the operation of the black
insertion rate setting unit in the exemplary embodiment shown in
FIG. 12;
[0033] FIG. 16 is a view showing the operation of the black
insertion rate setting unit in the exemplary embodiment shown in
FIG. 12;
[0034] FIG. 17 is a view showing a relationship characteristic of
the maximum value of the movement distance of each block calculated
by the black insertion rate setting unit and the black insertion
rate and light control luminance of a backlight in the exemplary
embodiment shown in FIG. 12;
[0035] FIG. 18 is a view showing a configuration of an image
display device of a related art;
[0036] FIG. 19 is an explanatory view showing the operation of the
image display device of the related art; and
[0037] FIG. 20 is an explanatory view showing a display screen in
the image display device of the related art.
DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS
[0038] An exemplary embodiment of the present invention will be
described in detail based on the drawings.
[0039] As shown in FIG. 1 and FIG. 12, a hold type image display
system according to an exemplary embodiment of the present
invention addresses a hold type image display system for displaying
a video on a display panel by controlling signals to be input to
source lines H1, H2, . . . , Hn and gate lines V1, V2, . . . , Vn
of the display panel, and includes a source driver 4 for outputting
a video signal to the source lines H1, H2, Hn, gate drivers 5A, 5B,
. . . , 5N for outputting a scanning signal to the gate lines V1,
V2, . . . , Vn, and a controller 7 for drive controlling the source
driver and the gate driver, as a basic configuration. The
controller 7 outputs a video signal (hereinafter referred to as
black insertion video signal) in which a black line (hereinafter
referred to as just "black" collectively) is inserted between the
video lines to the source driver 4 (FIGS. 2 and 8 etc.), outputs a
start pulse signal for writing the video lines for one or more
times and a start pulse signal for writing a black line for one or
more times to the gate drivers 5A, 5B, . . . , 5N within one frame
period, and inverts the write polarity of the video signal and the
write polarity of the black signal in frame cycle (FIGS. 3 to 7
etc.)
[0040] In the exemplary embodiment of the present invention, the
video is displayed on the display panel by controlling the signal
to the source line of the display panel in the source driver and
controlling the signal to the gate line of the display panel in the
gate driver, where in the video display, a video signal in which a
black line is inserted between the video lines is output to the
source driver, a start pulse signal for writing the video lines and
a start pulse signal for writing a black line are output to the
gate drivers, and the write polarity of the video signal and the
write polarity of the black signal are inverted in frame cycle.
[0041] Specifically describing, the controller 7 determines the
black insertion rate when data of black insertion rate is input to
the controller 7 by determination of each user, and the like.
Furthermore, the controller 7 inserts the black signal between the
lines of the input video signal. The controller 7 inputs a control
signal of the driver including a polarity inverting signal (POL)
determined at a timing complying with the black insertion rate
along with the video signal inserted with the black signal to the
gate drivers 5A, 5B, . . . , 5N and the source driver 4.
[0042] The details of the black insertion drive in the exemplary
embodiment of the present invention will be described using FIGS. 2
and 7. As shown in FIG. 2, the controller 7 inputs the video signal
in which the black signal is inserted between the lines of the
video signal to the source driver 4. The source driver 4
alternately outputs the video signal and the black signal to the
display panel in the order of input signal.
[0043] Specifically describing, when writing the video signal to
one of the lines of the gate driver 5A and writing the black signal
to one of the lines of the gate driver 5B of the gate drivers 5A,
5B, . . . , 5N in 1H period, as shown in FIG. 7A, the controller 7
inputs a video signal write enable signal (VOE_i) for turning OFF
the gate to the gate driver 5A during the period the source driver
4 outputs the black signal, and inputs a black signal write enable
signal (VOE_b) for turning OFF the gate to the gate driver 5B
during the period the source driver 4 outputs the video signal.
[0044] On the other hand, when writing the black signal to one of
the lines of the gate driver 5A and writing the video signal to one
of the lines of the gate driver 5B in 1H period, as shown in FIG.
7B, the controller 7 inputs the black signal write enable signal
(VOE_b) to the gate driver 5A, and inputs the video signal write
enable signal (VOE_i) to the gate driver 5B.
[0045] Thus, the video signal and the black signal can be written
to two lines at different positions in the 1H period by controlling
the source driver 4 and the gate driver 5A, 5B, . . . , 5N through
the controller 7.
[0046] The details of black insertion using a method of writing the
video signal and the black signal will be described using FIG. 8.
In the exemplary embodiment of the present invention, the
controller 7 inputs a start pulse signal (VSP_i) for writing the
video lines of one or more times and a start pulse signal (VSP_b)
for writing the black line of one or more times to the gate driver,
as shown in FIG. 8. The controller 7 inputs the video signal start
pulse signal (VSP_i) at the start of the frame, and sequentially
turns ON the TFT of the display panel (liquid crystal panel) while
shifting (scanning) the lines of the screen by the gate driver.
[0047] The controller 7 inputs the black signal start pulse signal
(VSP_b) within the frame period such as the middle according to the
black insertion rate, and sequentially turns ON the TFT of the
display panel (liquid crystal panel) while shifting (scanning) the
lines of the screen by the gate driver.
[0048] When the controller 7 drive controls the gate driver in the
above manner, a black insertion drive in which a black band scrolls
the screen display at the display panel in one frame, and the black
insertion rate is adjusted by changing the width of the black band
is realized, as shown in FIG. 9B. As shown in FIG. 10, the black
signal start pulse (VSP_b) can be input at an arbitrary timing as
long as the lines of the video signal and the black signal are not
simultaneously selected with one gate driver, and thus there is no
limitation by timing of a break of the driver and the like.
[0049] A write polarity inversion drive according to an exemplary
embodiment of the present invention will now be described. In the
black insertion drive in which the black insertion rate can be
adjusted, at which pixel of the display screen the black signal is
used changes according to the black insertion rate, and
furthermore, the black signal is positioned in the middle of the
display screen at the switching of the frames of the video signal.
Thus, as shown in FIGS. 7A and 7B, the controller 7 performs a
frame inversion on the write polarity for writing the video signal,
with a timing of inputting the image signal start pulse (VSP_i) as
the base point, and independent therefrom, performs a frame
inversion on the write polarity for writing the black signal, with
a timing of inputting the black signal start pulse (VSP_b) as a
base point.
[0050] Therefore, the controller 7 outputs the video signal in
which the black line is inserted between the video lines to the
source driver 4, outputs the start pulse signal for writing the
video lines and the start pulse signal for writing the black line
to the gate drivers 5A, 5B, . . . , 5N, and inverts the write
polarity of the video signal and the write polarity of the black
signal in frame cycle to eliminate display luminance difference and
burning having the line at which the polarity inversion switches as
a boundary generated by variation in field through of the display
panel surface and variation in positive and negative of the
application voltage.
[0051] In the above configuration, the exemplary embodiment of the
present invention is built as a hold type image display system
serving as hardware, but the functions executed by the controller 7
may be built as a program to be processed in a personal computer.
In this case, the control program of the hold type image display
system according to the exemplary embodiment of the present
invention is built with a configuration for causing a computer to
execute a function of outputting the video signal in which a black
line is inserted between the video lines to the source driver, a
function of outputting the start pulse signal for writing the video
lines and the start pulse signal for writing a black line to the
gate drivers, and a function of inverting the write polarity of the
video signal and the write polarity of the black signal in frame
cycle.
[0052] The exemplary embodiment of the present invention will be
further described using specific examples.
First Exemplary Embodiment
[0053] An example in which at least two gate drivers capable of
collectively enabling the gate output with respect to a plurality
of gate lines of a display panel are arranged will be described as
a first exemplary embodiment of the present invention.
[0054] As shown in FIG. 1A, a display panel 1 of the image display
device of the first exemplary embodiment of the present invention
has a configuration in which m (m is a natural number) gate lines
V1 to Vm and n (n is a natural number) source lines H1 to Hn are
arrayed so as to intersect each other to a matrix form, and a pixel
6 is formed at each intersection of the gate lines and the source
lines. A source driver 4 is connected to the source lines H1 to Hn,
the gate lines V1 to Vn are divided into a plurality of gate line
groups, and gate drivers 5A to 5N are connected to the gate lines
of each gate line group.
[0055] In the example of FIG. 1A, the gate driver 5A is connected
to the gate lines V1 to Vi of the gate line group, the gate driver
5B is connected to the gate lines V(i+i) to Vj of the gate line
group, and the gate driver 5N is connected to the gate lines V(l+1)
to Vm of the gate line group.
[0056] As shown in FIG. 1B, a circuit of the pixel 6 formed in the
display panel 1 is configured by a thin-film transistor (TFT) 12
and a liquid crystal layer 14. The source electrode of the
thin-film transistor 12 is connected to the source lines H1 to Hn,
a gate electrode of the TFT 12 is connected to the gate lines V1 to
Vm, and a drain electrode of the TFT 12 is connected to a pixel
electrode 13 formed on a glass substrate (not shown). A liquid
crystal layer 14 is interposed between the pixel electrode 13 and a
common electrode 15 that form a pair. The circuit configuration of
the pixel 6 is universal.
[0057] The video display by the pixels 6 of the display panel 1 is
carried out with the optical transmittance of the liquid crystal
layer 14 controlled by the potential difference between the pixel
electrode 13 and the common electrode 15. Specifically, when the
video signal is written to the pixel 6, the gate-ON signal (Vg1 to
Vgm) transmitted via the gate lines V1 to Vm from the gate drivers
5A, 5B, . . . , 5N turns ON the TFT 12 thereby applying the tone
voltage, which corresponds to the video signal provided from the
source driver 4 to the source lines H1 to Hn, to the pixel
electrode 13, and a video display on the display panel 1 based on
the video signal is realized while controlling the optical
transmittance of the liquid crystal layer 14 by the potential
difference between the voltage of the common electrode 15 and the
tone voltage of the pixel electrode 13.
[0058] As shown in FIG. 1A, the image display device of the first
exemplary embodiment includes the controller 7 for controlling the
operation of the source driver 4 and the gate drivers 5A to 5N. As
shown in FIG. 1A, the controller 7 includes a black insertion
signal converting unit 8, a drive control unit 9, and a black
insertion setting unit 10. The black insertion signal converting
unit 8 inserts a black image signal between the lines of the video
signal, that is, inserts the black image signal to the input video
signal, creates a black insertion video signal containing a video
signal portion and a black image signal portion within a horizontal
scanning period, and outputs the same. The black insertion rate
setting unit 10 determines the black insertion rate by
determination of each user. The drive control unit 9 inputs, along
with the video signal inserted with the black signal output by the
black insertion signal converting unit 8, a control signal of a
driver containing a polarity inversion signal (POL) determined at a
timing corresponding to the black insertion rate determined in the
black insertion setting unit 10 to the source driver 4 and the gate
drivers 5A to 5N.
[0059] In the first exemplary embodiment of the present invention,
the drive control unit 9 of the controller 7 inputs the video
signal write enable signal (VOE_i) for turning OFF the gate to the
gate driver 5A during the period the source driver 4 outputs the
black signal and inputs the black signal write enable signal
(VOE_b) for turning OFF the gate to the gate driver 5B during the
period the source driver outputs the video signal when writing the
video signal to one of the lines of the gate driver 5A and writing
the black signal to one of the lines of the gate driver 5B in 1H
period, as shown in FIG. 7A.
[0060] On the other hand, as shown in FIG. 7B, when writing the
black signal to one of the lines of the gate driver 5A and writing
the video signal to one of the lines of the gate driver 5B in 1H
period, the drive control unit 9 inputs the black signal write
enable signal (VOE_b) to the gate driver 5A and inputs the video
signal write enable signal (VOE_i) to the gate driver 5B.
[0061] The drive control unit 9 writes the video signal and the
black signal to two lines at different positions in 1H period by
performing the above control.
[0062] Specifically describing, at least two gate drivers for
collectively enabling the gate output are used, and each gate
driver 5A to 5N is controlled by an output enable signal
independent from each other from the drive control unit 9.
[0063] As shown in FIG. 2, one frame period includes a write period
(horizontal scanning period) of the same number as the number (n)
of source lines H1 to Hn and a blanking period. The blanking period
is set between the last write period (video line N) of the previous
frame period and the first write period (video line 1) of the next
frame period. In the first exemplary embodiment of the present
invention, assuming the portion corresponding to the write period
of the input video signal as a line image portion (horizontal
scanning period portion), the black insertion signal converting
unit 8 inserts the black image signal between the line image
portions in the input video signal and similarly inserts the black
image signal to the blanking period in the input video signal (data
of source driver input of FIG. 2). In FIG. 2, when writing the
black image signal in the blanking period, a case of outputting a
dummy signal (signal of dotted line pattern in FIG. 2) between the
black image signals to be written is shown, but is not limited
thereto. The black insertion signal converting unit 8 may similarly
insert the black image signal in the case of the input video signal
where there is not output of dummy signal in the blanking period.
Generally, the video signal in the blanking period does not need to
have the dummy signal output between the black image signals when
writing the black image signal to the blanking period.
[0064] The source driver 4 receives a drive control signal start
pulse (HSK), a horizontal clock signal (HCK), a latch signal (DLP),
a polarity inversion control signal (POL), and a black insertion
signal (data), and alternately outputs the line image portion and
the black image portion to the source lines H1 to Hn under the
control of the polarity inversion control signal (source driver
output of FIG. 2).
[0065] In the first exemplary embodiment, when the drive control
unit 9 inputs the black insertion image signal created by the black
insertion signal converting unit 8 to the source driver 4, the
source driver 4 drives the source lines H1 to Hn at double speed
and outputs the black insertion image signal to the source lines H1
to Hn, but is not limited thereto, and the source driver 4 may
adjust the output charge to the source lines H1 to Hn to the tone
charge corresponding to black display, and output the input video
signal to the source lines H1 to Hn while switching the output
charge to the tone charge corresponding to the black display at a
constant interval, as shown in FIG. 11. With this, the black
insertion signal converting unit 8 does not need to be arranged,
that is, the line memory necessary for the black image insertion
can be reduced, and the drive frequency of the source driver 4
involved in black image insertion does not need to be doubled.
[0066] The drive control unit 9 individually provides an output
enable signal for controlling opening/closing of the gate output by
the gate drivers 5A to 5N to the gate drivers 5A to 5N.
Specifically, the drive control unit 9 individually provides, to
the gate drivers 5A to 5N, a video display enable signal (VOE_i)
for validating the output of the gate-ON signal only during the
period the line image portion of the black insertion video signal
is being provided to the source lines H1 to Hn, or a black display
enable signal (VOE_b) for validating the output of the gate-ON
signal only during the period the black image portion of the black
insertion video signal is being provided to the source lines H1 to
Hn.
[0067] Accordingly, each gate driver 5A to 5N is divided into gate
line groups, and collectively controls the output on the connected
gate lines V1 to Vi, V(i+i) to Vj, . . . , V(l+1) to Vm.
Specifically, the gate drivers 5A to 5N has a function serving as a
video displaying device for sequentially providing a video display
gate-ON signal of a pulse width for writing only the line image
portion of the black insertion video signal to the pixel 6 to the
gate lines V1 to Vi, V(i+1) to Vj, V(l+1) to Vm in response to the
VOE_i from the drive control unit 9 and sequentially executing the
image display scanning, and a function serving as a black
displaying device sequentially providing a black display gate-ON
signal of a pulse width for writing only the black image portion of
the black insertion image signal to the pixel 6 to the gate lines
V1 to Vi, V(i+1) to Vj, . . . , V(l+1) to Vm in response to the
VOE_b and sequentially executing the black image display
scanning.
[0068] The drive control unit 9 outputs a video display scanning
start pulse (VSP_i) for writing the video signal and a black
display scanning start pulse (VSP_b) for writing the black image
signal to the gate drivers 5A to 5N one at a time at different
timings in one frame period. The drive control unit 9 outputs the
VSP_i to the gate drivers 5A to 5N at the start of video display
scanning, and at the same time, starts to provide the VOE_i to the
gate drivers 5A to 5N. When the video display scanning is
terminated at the gate drivers 5A to 5N, the drive control unit 9
starts to provide the VOE_b to the gate drivers 5A to 5N, and
outputs the VSP_b to the gate drivers 5A to 5N at a timing to start
the black image display scanning.
[0069] Furthermore, the controller 7 includes the black insertion
rate setting unit 10 for setting the timing of the black display
start pulse (VSP_b) by the drive control unit 9 according to the
operation environment.
[0070] The controller 7 includes the black insertion rate setting
unit 10 in the above description, but is not limited thereto. As
shown in FIG. 1C, a black insertion rate setting unit 10a may be
arranged in place of the black insertion rate setting unit 10. The
black insertion rate setting unit 10a is input with data of black
insertion rate by the user irrespective of the input signal, and
outputs the black insertion rate to the drive control unit 9. When
the black insertion rate setting unit 10a is used, the user inputs
the data of black insertion rate corresponding to the in-plane
luminance difference to the black insertion rate setting unit 10a
while looking at the screen. Therefore, the black insertion rate
that complies with the user can be set.
[0071] The black insertion rate setting unit 10 has a function of
determining the black image insertion rate for every frame period
while referencing the input video signal, and also has a function
of setting the timing of the VSP_b output by the drive control unit
9 in correspondence to the determined black image insertion rate.
Specifically, the black insertion rate setting unit 10 includes a
frame memory (not shown) for temporarily storing information for
one frame of the input video signal sequentially input for every
frame; and a determining unit (not shown) for comparing the video
signal of one frame of the input video signal and the video signal
of the previous frame stored in the frame memory, and determining
the optimum black image insertion rate based on the changed
data.
[0072] Thus, the black image insertion rate for every frame period
suited to the driving method, the usage state, and the like of the
display panel 1 is determined, and the timing of the VSP_b output
for realizing the determined black image insertion rate is set. The
timing set here is the timing at which the pixel lines for writing
the video signal and for writing the black image signal are not
simultaneously selected with one gate driver.
[0073] For instance, when receiving the VSP_b from the drive
control unit 9 at a timing set by the black insertion rate setting
unit 10, the gate driver 5A sequentially provides the VSP_b to the
gate lines V1 to Vi as the black display gate-ON signal based on
the VOE_b provided in advance, and drive control unit 9 shift
outputs the VSP_b to the next gate driver 5B when scanning is
terminated.
[0074] The drive control unit 9 provides the black insertion video
signal (data), and also provides a signal start pulse (HSP), a
horizontal clock signal (HCK), a latch signal (DLP), and a polarity
inverting control signal (POL), which are signals for drive
controlling the source driver 4, to the source driver 4, and
provides a scanning start pulse (VSP_i or VSP_b), a vertical clock
signal (VCK), and an enable signal (VOE_i or VOE_b), which are
signals for drive controlling the gate drivers 5A to 5N.
[0075] The source driver 4 starts retrieving data signal by input
of HSP, and sequentially accumulates the data signal in a shift
register arranged inside in synchronization with the HCK. The
source driver 4 confirms the data signal by the input of DLP, and
at the same time, confirms positive or negative from the reference
voltage according to POL, and outputs the tone voltage
corresponding to the data signal to the source lines H1 to Hn.
[0076] The polarity inverting control signal (POL) is a control
signal for confirming the polarity (positive or negative from the
reference voltage) of the tone voltage output from the source
driver 4 to the source lines H1 to Hn. The drive control unit 9
controls the POL, executes frame polarity inversion drive such as
dot inversion and vertical 2-dot inversion drive shown in FIGS. 3
to 5, inverts the write polarity of the line image portion in frame
cycle of VSP_i base point, and inverts the write polarity of the
black image portion in frame cycle of VSP_b base point.
[0077] FIG. 6 is a timing chart describing one example of the POL
signal in the first exemplary embodiment using a case of dot
inversion drive shown in FIG. 3 by way of example.
[0078] When the POL is high, for example, the source driver 4
outputs a positive voltage to the odd-numbered source lines H1, H3,
H5, H7, . . . and a negative voltage to the even-numbered source
lines H2, H4, H6, H8, and when the POL is low, for example, the
source driver 4 outputs the negative voltage to source lines H1,
H3, H5, H7, . . . , and the positive voltage to the even-numbered
source lines H2, H4, H6, H8.
[0079] The drive control unit 9 counts 0 to 1 frame of the VSP_i
base point by the 1 bit frame counter of the VSP_i cycle, and at
the same time counts 0 to 3 by the 2 bit line counter of the DLP
cycle from the VSP_i. The drive control unit 9 then generates an
internal signal (POL_i) that is Low when line counter=2 in 0 frame,
Low when line counter=0 in one frame, and high in other cases.
[0080] The drive control unit 9 counts 0 to 1 frame of the VSP_b
base point by the 1 bit frame counter of the incorporated VSP_b
cycle, and at the same time counts 0 to 3 by the 2 bit line counter
of the DLP cycle from the VSP_b. The drive control unit 9 then
generates an internal signal (POL_b) that is Low when line
counter=2 in 0 frame, Low when line counter=0 in one frame, and
high in other cases.
[0081] The drive control unit 9 finally outputs a POL, which is AND
of the internal signal (POL_i) and the internal signal (POL_b), to
the source driver 4. The source driver 4 inputs the POL as shown in
FIG. 6 to execute the dot inversion drive in which the write
polarity of the line image portion inverts in frame cycle of VSP_i
base point, and the write polarity of the black image portion
inverts in frame cycle of the VSP_b base point.
[0082] According to such configuration, the drive control unit 9
can invert the polarity of the video signal and the black signal in
frame cycle having independent timings as the base point by simply
incorporating a frame counter and a line counter for black signal
inversion independently.
[0083] Therefore, the drive control unit 9 serves as a frame
polarity inverting device for inverting the application voltage
polarity to the pixel corresponding to the video signal in frame
cycle having the start of video display scanning as the base point,
and inverting the application voltage polarity to the pixel
corresponding to the black image signal in frame cycle having the
start of black image display scanning as the base point by
controlling the POL. Thus, DC voltage is prevented from being
applied to the liquid crystal.
[0084] The black insertion signal converting unit 8, the drive
control unit 9, and the black insertion rate setting unit 10 in the
controller 7 may have the functional contents thereof programmed to
be executed by a computer.
[0085] FIGS. 7A and 7B are timing charts of a signal propagating
through the image display device of the first exemplary
embodiment.
[0086] FIG. 7A is a timing chart for a case where the line image
signal is provided to the pixel 6 on the gate lines V1 to Vi
corresponding to the gate driver 5A, and the black image signal is
provided to the pixel 6 on the gate lines V(i+1) to Vj
corresponding to the gate driver 5B; and FIG. 7B is a timing chart
for a case where the black image signal is provided to the pixel 6
on the gate lines V1 to Vi corresponding to the gate driver 5A, and
the line image signal is provided to the pixel 6 on the gate lines
V(i+1) to Vj corresponding to the gate driver 5B, in contrast to
FIG. 7A.
[0087] As shown in FIG. 7A, the VOE_i is input to the gate driver
5A when providing the line image signal to the pixel 6 on the
corresponding gate lines V1 to Vi, whereby the gate-ON signal is
converted to the image display gate-ON signal having a pulse width
same as the line image signal output period of the source driver 4,
and is sequentially provided to the gate lines V1 to Vi from the
gate driver 5A.
[0088] The VOE_b is input to the gate driver 5B when providing the
black image signal to the pixel 6 on the gate lines V(i+1) to Vj,
whereby the gate-ON signal is converted to the black display
gate-ON signal having a pulse width same as the black image signal
output period of the source driver 4, and is sequentially provided
to the gate lines V(i+1) to Vj from the gate driver 5B.
[0089] Thus, in the first exemplary embodiment, the video signal or
the black image signal can be written to different pixel lines in
1H period (one horizontal scanning period).
[0090] The operation of the image display device of the first
exemplary embodiment will now be described. FIG. 8 is a view
describing the operation of the image display device of the present
exemplary embodiment. Each step in the method of driving the image
display device of the present invention will also be shown to be
simultaneously described.
[0091] First, the black image insertion rate for every frame period
is determined and set based on the video signal input by the black
insertion rate setting unit 10 (black insertion rate setting step).
In the black insertion signal converting unit 8, the black image
signal is inserted between the line image portions of the input
video signal, and output to the drive control unit 9 as a black
insertion video signal (black insertion signal converting
step).
[0092] When the black insertion video signal is output from the
drive control unit 9 to each source driver 4, various drive control
signals are output to the gate drivers 5A to 5N and each source
driver 4 in synchronization therewith.
[0093] In the first exemplary embodiment, a plurality of gate
drivers capable of collectively enabling the gate output is used,
and the gate drivers 5A to 5N are controlled by an independent
output enable signal (VOE_i or VOE_b) from the drive control unit
9.
[0094] As shown in FIG. 2, the black insertion video signal is
input from the drive control unit 9 to the source driver 4. The
source driver 4 alternately outputs the video signal and the black
image signal to the source lines H1 to Hn based on the input black
insertion video signal (black insertion video signal providing
step).
[0095] As shown in FIG. 8, the VSP_i indicating the start of the
frame is input from the drive control 9 to the gate driver 5A along
with the VOE_i (video start pulse input step), which VSP_i shifts
the gate lines V1 to Vi as a gate-ON signal in synchronization with
the similarly input clock signal (VCK) and turns ON the TFT 12 of
the pixel 6 on each gate line V1 to Vi. Meanwhile, the VOE_i is
input to the gate driver 5A.
[0096] Subsequently, when scanning in the gate driver 5A is
terminated, the VSP_i is shift input to the gate driver 5B, and at
the same time, the VOE_i is input to the gate driver 5B from the
drive control unit 9. In the gate driver 5B, the VSP_i shifts the
corresponding gate lines V(i+1) to Vj as a gate-ON signal, and the
VOE_i is input to the gate driver 5B during the shifting period.
The VSP_i is then similarly shift input to the gate driver 5N, and
at the same time, the VOE_i is input from the drive control unit 9.
In the gate driver 5N as well, the VSP_i shifts the corresponding
gate lines V(l+1) to Vm as a gate-ON signal, and the VOE_i is input
during the shifting period (video scanning step). The VOE_b is
input to the gate drivers 5A to 5N at other than the above
periods.
[0097] The VSP_b from the drive control unit 9 is input to the gate
driver 5A once within the frame period according to the timing
determined by the black insertion rate setting unit 10 (black
display start pulse input step), and similarly, the VSP_b shifts
the corresponding gate lines V1 to Vi as a gate-ON signal by the
clock signal (VCK) of the gate driver 5A and turns ON the TFT of
the pixel 6 on each gate line V1 to Vi. During such black image
display scanning, the VOE_b is input to the gate driver 5A.
[0098] When the black image display scanning in the gate driver 5A
is terminated, the VSP_b is shift input to the gate driver 5B, and
the VSP_b shifts the corresponding gate lines V(i+1) to Vj as a
gate-ON signal. The VOE_b is also input to the gate driver 5B
during the shifting period. Thereafter, the VSP_b is shift input to
the gate driver 5N, similarly, and the black image display scanning
in the gate driver 5N is started (black scanning step).
[0099] Therefore, in the first exemplary embodiment, the video
display scanning start pulse (VSP_i) input for writing the video
signal of one time and the black display scanning start pulse
(VSP_b) input for writing the black image signal of one time are
performed on the gate driver 5A within one frame period.
[0100] According to such configuration, the screen display realizes
a black image insertion drive in which the black band scrolls
through the screen during one frame, as shown in FIG. 9B. The width
of the black band is determined by the timing of input of the black
display scanning start pulse (VSP_b) with respect to the input of
the video display scanning start pulse (VSP_i). Furthermore,
according to the first exemplary embodiment, the holding time of
the video signal and the holding time of the black image signal
become constant at all the pixels 6 in the screen by continuing the
write of the black image signal in the blanking period between the
frames, as shown in FIG. 8, and the in-plane luminance difference
caused by the difference in holding times can be eliminated.
[0101] The VSP_b can be input at an arbitrary timing as long as it
is a timing at which the pixel line of the video signal and the
black image signal is not simultaneously selected by one gate
driver as in the black VSP settable range shown in FIG. 10, and
restrictions such as timing of break of the gate driver as in the
display device of the related art are not imposed. The black
insertion rate thus can be finely adjusted, and an optimum black
insertion rate corresponding to the usage environment can be set in
view of the balance between the effect of reducing the moving image
blur, which is the merit of black image insertion, and lowering in
luminance, which is the demerit of black image insertion.
[0102] In the first exemplary embodiment, the optimum black
insertion drive can be applied regardless of the liquid crystal
driving method according to the display panel 1, which may be TN
type, IPS type, VA type, OCB type, or the like.
[0103] Furthermore, the video signal is frame inverted with the
input of the VSP_i as the base point (video signal polarity
inversion step), and independent therefrom, the black signal is
frame inverted with the input of the VSP_b as the base point (black
image signal polarity inversion step) when the drive control unit 9
controls the POL, as shown in FIG. 8.
[0104] According to such configuration, the order of inversion is
prevented from reversing near the center of the screen, and display
luminance difference and burning with the line at which the
polarity inversion switches as the boundary caused by variation in
the field through of the display panel 1 surface and the variation
in positive and negative of the application voltage are eliminated.
Furthermore, since this configuration merely has the drive control
unit 9 independently equipped with the black signal inversion
counter, the cost does not increase, and switching of the black
insertion rate can be flexibly responded.
[0105] In the first exemplary embodiment, the moving image blur is
alleviated by inserting the black image display between each video
frame in the image display device, but it is not limited to black
display, and gray display such as gray may be inserted. In this
case, lowering in luminance can be suppressed in addition to
reducing the moving image blur but the contrast with the color
region lowers, and thus a configuration of setting an optimum gray
insertion rate in view of such is adopted.
[0106] In the first exemplary embodiment, the black insertion rate
setting unit 10 determines the black image insertion rate for every
frame period by referencing the input video signal, and sets the
timing to input the VSP_b to the gate driver 5A according to the
determined black image insertion rate, but the configuration is not
limited thereto, and the black insertion rate setting unit 10 may
set the timing to input VSP_b to the gate driver 5A according to
the timing data externally input through operation of the user or
the like.
[0107] The first exemplary embodiment described above can change
the black image insertion rate by changing the timing to input the
VSP_b to the gate driver 5A, can perform normal drive in which the
black image insertion is not performed by not inputting the VSP_b,
and can easily switch the black image insertion rate. Therefore,
when used in monitors, a bright screen with small amount of
flickers is provided without performing black insertion, and for
moving image display such as TV, a screen performed with black
insertion is provided for reducing moving image blur, and thus a
display corresponding to the usage state of the user can be
provided.
[0108] Applications such as continuously switching the black image
insertion rate depending on the scene of the video such as from a
static screen displaying landscape etc. to an active screen
displaying sports etc. are also possible.
[0109] The first exemplary embodiment can also prevent display
luminance difference and burning having the line at which the
polarity inversion switches as a boundary caused by variation in
field through of the display panel 1 surface and variation in
positive and negative of the application voltage since the video
signal and the black signal have the write polarity inverted in
frame cycle having the timing independent from each other as the
base point.
Second Exemplary Embodiment
[0110] Next, a second exemplary embodiment of the present invention
will be described.
[0111] FIG. 12 is a view showing a configuration of an image
display device of a second exemplary embodiment according to the
present invention. Same reference numerals are denoted for
components same as in the first exemplary embodiment shown in FIG.
1A. As shown in FIG. 12, the second exemplary embodiment has a
backlight 21 arranged at the rear surface of the display panel 1
when seen from the user, in addition to the configuration similar
to the first exemplary embodiment. A black insertion rate setting
unit 20 has a function of temporarily storing information for one
frame of the input video signal sequentially input for every frame,
and comparing the video signal of one frame of the input video
signal and the video signal of the previous frame that is
temporarily stored to determine the black image insertion rate and
the light control luminance of the backlight based on the changed
number of data, and a drive control unit 29 has a function of
adjusting the light control luminance of the backlight 21 based on
the determination of the black insertion rate setting unit 20.
[0112] Similar to the first exemplary embodiment, the VSP_b from
the drive control unit 9 is input to the gate driver 5A according
to the timing determined by the black insertion rate setting unit
20, where the video signal is frame inverted with the input of the
VSP_i as the base point, and independent therefrom, the black
signal is frame inverted with the input of the VSP_b as the base
point when the drive control unit 9 controls the POL.
[0113] FIG. 13 is a flowchart showing the operation of the black
insertion rate setting unit 20 in the image display device of the
second exemplary embodiment.
[0114] The black insertion rate setting unit 20 compares current
frame data "data (n)" and previous frame data "data (n-1)", and
counts the changed data for one frame (FIG. 13: steps S91 to S93).
The counted information is moving averaged over a few frames and
smoothened (FIG. 13: step S95), and threshold determined (FIG. 13:
step S96) to determine whether the image is a static image or a
dynamic image.
[0115] If the determination result suggests static image, black
insertion is not performed for example, and the light control
luminance of the backlight 21 is set to be 50% (FIG. 13: step S98),
whereas if the determination result suggests dynamic image, the
black insertion rate is switched to be 50% for example, to reduce
the moving image blur and the light control luminance of the
backlight 21 is switched to be 100% (FIG. 13: step S97, black
insertion rate setting step).
[0116] According to such configuration, the black insertion rate
can be switched according to the scene of the video, and the moving
image blur can be reduced as necessary. The light of the backlight
21 is controlled with the black image insertion because the
transmissive efficiency of the panel lowers in exchange for
improvement of the moving image blur by black image insertion, as
shown in FIG. 14. With this, the change in luminance due to
switching of black insertion can be prevented, and in the case of
static video where black image insertion is unnecessary, power
consumption can be reduced by performing light control of the
backlight 21.
[0117] Another example of the operation of the black insertion rate
setting unit 20 in the second exemplary embodiment is shown in
FIGS. 15 to 17.
[0118] Another method for the black insertion rate setting unit 20
to determine the black image insertion rate and the light control
luminance of the backlight includes, firstly, dividing one frame
into a plurality of blocks set in advance, as shown in FIG. 15. And
then, the distance the image of an arbitrary block moves from the
previous frame to the current frame is calculated, as shown in FIG.
16.
[0119] The method of calculating the distance includes detecting
the position of the block of the previous frame and the block in
which the average absolute value error is the smallest from the
current frame using tree search method and the like, and obtaining
the distance the relevant block has moved.
[0120] The maximum value of the calculated movement distance of
each block, and the black insertion rate and the light control
luminance of the backlight 21 at the relevant point are shown in
FIG. 17. According to such configuration, the power consumption of
the backlight can be reduced by continuously switching the black
insertion rate according to the movement of the scene of the video,
and performing the black image insertion of requisite minimum
according to the extent of movement.
[0121] Another exemplary embodiment of the present invention will
now be described. A hold type image display system according to the
exemplary embodiment of the present invention relates to an image
display device equipped with a display panel in which a plurality
of gate lines and a plurality of source lines are arranged
respectively intersecting each other in a grid form, a pixel being
formed at each intersection of the gate lines and the source lines;
the image display device including an image scanning device for
executing an image display scanning for displaying a video on a
display panel according to an input video signal; a black scanning
device for starting and executing a black image display scanning
for displaying a black screen on a display panel at an arbitrary
timing within one video frame period in the video display scanning;
and a frame polarity inverting device for inverting the polarity of
an application voltage to the pixel by the video scanning device in
frame cycle having the start of video display scanning as a base
point, and inverting the polarity of an application voltage to the
pixel by the black scanning device in frame cycle having the start
of black image display scanning as the base point.
[0122] According to such image display device, in a liquid crystal
display device for performing black insertion drive by inserting a
black image in one frame, the video signal and the black signal
have the write polarity inverted at the frame cycle having
independent timings as the base point, respectively, and thus the
display luminance difference and burning having the line at which
the polarity inversion switches as a boundary caused by variation
in field through of the display panel surface and variation in
positive and negative of the application voltage can be
prevented.
[0123] The hold type image display device according to the
exemplary embodiment of the present invention includes a display
panel having a configuration in which a plurality of gate lines and
a plurality of source lines are arranged respectively intersecting
each other in a grid form, a pixel being formed at each
intersection of the gate lines and the source lines; a source
driver for providing a black insertion video signal alternately
including a line image portion and a black image portion to each
source line; and a plurality of gate drivers arranged with respect
to gate line groups, the plurality of gate lines being divided into
a number of groups, for sequentially providing a gate-ON signal to
each corresponding gate line; and a drive control unit for
individually providing an output enable signal to each gate driver
and independently controlling the gate output of each gate driver;
where the drive control unit has a function of outputting a video
start pulse for writing the line image portion to a first gate
driver and outputting a black display start pulse for writing the
black image portion to a first gate driver at an arbitrary timing
within one video frame period, and inverting the write polarity of
the line image portion in frame cycle having the output of the
video start pulse as a base point and inverting the write polarity
of the black image portion in frame cycle having the output of the
black display start pulse as a base point.
[0124] According to such image display device, the gate driver is
arranged for each gate line group formed from a plurality of gate
lines, the enable of each gate driver is individually controlled,
and the black display start pulse is input to the gate driver at a
timing different from the video start pulse, and thus the ratio
between the video display time and the black image display time in
the black insertion drive (hereinafter referred to as black video
insertion rate) can be continuously adjusted instead of being
driver segmented. Furthermore, since the image signal and the black
signal have the write polarity inverted in frame cycle with
independent timing as the base point, display luminance difference
and burning having the line at which the polarity inversion
switches caused by variation in field through of the display panel
surface and variation in positive and negative of the application
voltage can be prevented.
[0125] In such image display device, the drive control unit may
also variably control the timing of output of a black display start
pulse with respect to output of a video start pulse. With this, the
black image insertion rate for every frame can be arbitrarily
changed by changing the timing of the black display start pulse
output.
[0126] In the above image display device, the drive control unit
may have a function of individually providing to each gate driver a
video display enable signal for validating the gate output of the
gate driver only during the period the line image portion of the
black insertion video signal is being provided to the source line,
or a black display enable signal for validating the gate output of
the gate driver only during the period the black image portion of
the black insertion video signal is being provided to the source
line. With this, the execution of the video display scanning or the
black image display scanning can be individually controlled with
respect to each gate driver.
[0127] In the above image display device, each gate driver may
provide to the corresponding gate line, the video display gate-ON
signal for writing only the line portion of the black insertion
image signal to the pixel according to the video display enable
signal, and provide to the corresponding gate line the black
display gate-ON signal for writing only the black image portion of
the black insertion video signal to the pixel according to the
black display enable signal. With this, each gate driver can switch
and execute the video display scanning or the black image display
scanning.
[0128] The image display device may also includes a black insertion
rate setting unit for setting the timing of the black display start
pulse output by the drive control unit according to the operation
environment. With this, the black image insertion rate for every
frame can be set from a large range according to each usage
state.
[0129] Further, in the above image display device, the black
insertion rate setting unit may have a function of determining the
black image insertion rate for every frame period based on the
input video signal, and the timing of the black display start pulse
output may be set based on the determined black image insertion
rate. With this, the black image insertion rate can be set
according to the content of the displaying video.
[0130] Further, in the image display device, the black insertion
rate setting unit may have a function of temporarily storing
information for one frame of the input video signal sequentially
input for every frame, and comparing the video signal of one frame
of the input video signal and the video signal of the previous
frame that is temporarily stored to determine the black image
insertion rate based on the changed data. With this, the optimum
black image insertion rate can be determined according to the
content of the displaying image.
[0131] Furthermore, the image display device may also include a
backlight arranged at the rear surface of the display panel, where
the black insertion rate setting unit may have a function of
temporarily storing information for one frame of the input video
signal sequentially input for every frame, and comparing the video
signal of one frame of the input video signal and the video signal
of the previous frame that is temporarily stored to determine the
black image insertion rate and the light control luminance of the
backlight based on the changed data. With this, the backlight is
light controlled according to black insertion, and black insertion
drive can be executed while preventing change in luminance due to
switching of black insertion.
[0132] Furthermore, in the above image display device, the drive
control unit may provide the image display enable signal to the
gate driver for shift outputting the gate-ON signal to each
corresponding gate line according to the video start pulse input
until such shift output is terminated, and may provide the black
display enable signal to other gate drivers. With this, the black
display start pulse input with respect to the gate driver at a
timing of high degree of flexibility becomes possible, and the
black image insertion rate can be continuously adjusted.
[0133] Furthermore, the image display device may include a black
insertion signal converting unit for inserting the black image
signal between the line image portions in the input image signal,
and outputting to the source driver as a black insertion video
signal. With this, the black insertion video signal for the source
driver to alternately output the line image portion and the black
image portion to each source line is obtained.
[0134] In the above image display device, the black insertion video
signal may also include the black image signal even in a blanking
period in the input video signal. With this, the write of black is
performed without stopping even in the blanking period between the
frames with respect to the write of the black signal over a
plurality of video frames, and thus the in-plane luminance
difference caused by difference in black image holding periods in
the display panel can be eliminated.
[0135] In the image display device, the black insertion video
signal may include a gray signal in place of the black image
signal. With this, the lowering in luminance due to black insertion
drive is alleviated.
[0136] A method of driving a hold type image display device
according to an exemplary embodiment is a method of driving an
image display device including a display panel in which a plurality
of gate lines and a plurality of source lines are arranged
respectively intersecting each other in a grid form, a pixel being
formed at each intersection of the gate lines and the source lines;
a source driver for providing a video signal to each source line; a
plurality of gate drivers, arranged with respect to gate line
groups, a plurality of gate lines being divided into a number of
groups, for sequentially providing a gate-ON signal to each
corresponding gate line; and a drive control unit for individually
providing an output enable signal to each gate driver; the method
including a black insertion video signal providing step in which
the source driver starts to provide to each source line a black
insertion video signal alternately including a line image portion
and a black image portion; a video start pulse input step in which
the drive control unit inputs, to a first gate driver, a video
display start pulse for writing the line image portion in
synchronization with the black insertion video signal providing
step; an image scanning step in which an image display scanning of
sequentially providing to each gate line a video display gate-ON
signal for writing only the line image portion of the black
insertion video signal to the pixel is executed in order from the
first gate driver; a black display start pulse input step in which
the drive control unit inputs, to the first gate driver, a black
display start pulse for writing the black image portion at an
arbitrary timing within one video frame; a black scanning step in
which a black image display scanning of sequentially providing, to
each gate line, a black display gate-ON signal for writing only the
black image portion of the black insertion video signal to the
pixel is executed in order from the first gate driver; a video
signal polarity inverting step of inverting the write polarity of
the line image portion in frame cycle having the output of the
video start pulse as a base point; and a black signal polarity
inverting step of inverting the write polarity of the black image
portion in frame cycle having the output of the black display start
pulse as a base point.
[0137] In such driving method, each gate driver may output the
video display gate-ON signal according to the video display enable
signal for validating the gate output of the gate driver only
during the period the line image portion of the black insertion
video signal is being provided to the source line in the video
scanning step, and each gate driver may output the black display
gate-ON signal according to the black display enable signal for
validating the gate output of the gate driver only during the
period the black image portion of the black insertion video signal
is being provided to the source line in the black scanning
step.
[0138] The above driving method may include a black insertion rate
setting step of setting the timing of the black display start pulse
output by the drive control unit according to the operation
environment.
[0139] According to the above driving method, in the black
insertion rate setting step, information for one frame of the input
video signal sequentially input for every frame may be temporarily
stored, the video signal of one frame of the input video signal and
the video signal of the previous frame that is temporarily stored
may be compared to determine the black image insertion rate based
on the changed data, and the timing of the black display start
pulse output is set based on the determined black image insertion
rate.
[0140] Furthermore, according to the driving method, in the black
inserting rate setting step, information for one frame of the input
video signal sequentially input for every frame may be temporarily
stored, the video signal of one frame of the input video signal and
the video signal of the previous frame that is temporarily stored
may be compared to determine the black image insertion rate and the
light control luminance of the backlight arranged at the rear
surface of the display panel in advance based on the changed data,
and the timing of the black display start pulse output and the
light control luminance of the backlight are set based on such
determination.
[0141] The driving method may includes a black insertion signal
converting step of inserting the black image signal between the
line image portions in the input image signal, and outputting to
the source driver as a black insertion video signal, before the
black insertion video signal providing step.
[0142] In the above driving method, the black insertion image
signal may include the black image signal even in a blanking period
in the input video signal.
[0143] In the above method of driving the image display device, the
black insertion video signal may include a gray signal in place of
the black image signal.
[0144] Similar to the image display device, according to the above
method of driving the image display device, the black insertion
rate can be finely set in view of the balance between reducing the
moving image blur, which is the merit, and lowering in luminance,
which is the demerit, and display luminance difference and burning
having the line at which the polarity inversion switches caused by
variation in field through in the display panel surface and
variation in positive and negative of the application voltage can
be prevented.
[0145] An image display device driving program according to an
exemplary embodiment of the present invention may cause a computer
for controlling the operation of the image display device to
execute processes, the image display device including a display
panel in which a plurality of gate lines and a plurality of source
lines are arranged respectively intersecting each other in a grid
form, a pixel being formed at each intersection of the gate lines
and the source lines; a source driver for providing a video signal
to each source line; and a plurality of gate drivers, arranged with
respect to gate line groups, the plurality of gate lines being
divided to groups, for sequentially providing the gate-ON signal to
each corresponding gate line; where the program causes the computer
to execute a video signal providing process of outputting a black
insertion video signal alternately including a line image portion
and a black image portion from the source driver to each source
line; a drive controlling process of individually providing an
output enable signal to each gate driver and independently
controlling the gate output of each gate driver; a video start
pulse output process of outputting a video start pulse input for
writing the line image portion to a first gate driver; a black
display start pulse output process of outputting a black display
start pulse for writing the black image portion to the first gate
driver at an arbitrary timing within one video frame; a video
signal polarity inverting process of inverting a write polarity of
the line image portion in frame cycle having the output of the
video start pulse as a base point; and a black signal polarity
inverting process of inverting a write polarity of the black image
portion in frame cycle having the output of the black display start
pulse as a base point.
[0146] In the above image display device driving program, the drive
controlling process may be specified to a content of individually
providing to each gate driver a video display enable signal for
validating the gate output of the gate driver only during the
period the line image portion of the black insertion video signal
is being provided to the source line, or a black display enable
signal for validating the gate output of the gate driver only
during the period the black image portion of the black insertion
video signal is being provided to the source line.
[0147] Furthermore, the image display device driving program may
cause the computer to execute a black insertion rate setting
process of setting the timing of the black display scanning process
according to the operation environment.
[0148] In the above image display device driving program, the black
insertion rate setting process may be specified to a content of
temporarily storing information for one frame of the input video
signal sequentially input for every frame, comparing the video
signal of one frame of the input video signal and the video signal
of the previous frame that is temporarily stored to determine the
black image insertion rate for every frame period based on the
changed data, and setting the timing of the black display scanning
process based on the determined black image insertion rate.
[0149] Furthermore, according to the above image display device
driving program, the black inserting rate setting process may be
specified to a content of temporarily storing information for one
frame of the input video signal sequentially input for every frame,
comparing the video signal of one frame of the input video signal
and the video signal of the previous frame that is temporarily
stored to determine the black image insertion rate and the light
control luminance of the backlight arranged at the rear surface of
the display panel in advance based on the changed number of data,
and setting the timing to start the black display scanning for
every gate line group and the light control luminance of the
backlight based on such determination.
[0150] The above image display device driving program may cause a
computer to execute a black insertion video signal creating process
of inserting the black image signal between the line image portions
in the input video signal, and outputting to the source driver as a
black insertion video signal.
[0151] In the above image display device driving program, the black
insertion video signal may include the black image signal even in a
blanking period in the input video signal.
[0152] In the above image display device driving program, the black
insertion video signal may include a gray signal in place of the
black image signal.
[0153] Similar to the image display device, according to the image
display device driving program, the black image insertion rate can
be finely set in view of the balance between reducing the moving
image blur, which is the merit, and lowering in luminance, which is
the demerit, and display luminance difference and burning having
the line at which the polarity inversion switches caused by
variation in field through in the display panel surface and
variation in positive and negative of the application voltage can
be prevented.
[0154] While the invention has been particularly shown and
described with reference to exemplary embodiments thereof, the
invention is not limited to these embodiments. It will be
understood by those of ordinary skill in the art that various
changes in form and details may be made therein without departing
from the spirit and scope of the present invention as defined by
the claims.
* * * * *