Electric lamp and discharge devices: systems – Plural power supplies – Plural cathode and/or anode load device
Reexamination Certificate
2003-06-17
2004-11-09
Vannucci, James (Department: 2821)
Electric lamp and discharge devices: systems
Plural power supplies
Plural cathode and/or anode load device
C345S110000
Reexamination Certificate
active
06815904
ABSTRACT:
The present invention claims the benefit of Korean Patent Application No. P2002-87109 filed in Korea on Dec. 30, 2002, which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a driving apparatus and method for a liquid crystal display, and more particularly to a driving apparatus and method for a liquid crystal display adaptive for improving brightness of the liquid crystal display.
2. Description of the Related Art
In general, liquid crystal display (LCD) devices are lightweight, have a thin profile, and have relatively low power consumption. Accordingly, the LCD devices are commonly implemented for office automation instruments, and audio and video devices. The LCD devices display image data on a screen by controlling light transmissivity in accordance with a video signal applied to a plurality of control switches.
The LCD devices are commonly replacing cathode ray tubes (CRTs) that use an impulse-type light emission by scanning of an electron gun. Conversely, the LCD devices use a hold-type light emission employing a backlight system, whereby a linear lamp (fluorescent lamp) is an illuminating light source. Accordingly, it is extremely difficult to display a series of images that results in a perfect motion picture. Specifically, when the series of images is displayed using the LCD devices, motion picture contour deterioration is generated due to operational characteristics of the hold-type light emission. Accordingly, picture quality is significantly deteriorated.
FIG. 1
is a simulation diagram illustrating generation of motion picture contour deterioration using hold-type light emission according to the related art. In
FIG. 1
, (A) illustrates that a white image moving along a first direction A is displayed on part of a black background picture of an LCD, (B) is an enlarged diagram of a boundary area of black/white images, (C) is a diagram explaining a cause for generation of a motion picture contour deterioration, and (D) is an enlarged diagram illustrating a state of the motion picture contour deterioration. In
FIG. 1
, a unit square represents a pixel, and motion picture contour deterioration is identified as “blurring” or “motion picture blurring.”
In (C) of
FIG. 1
, where one row of black/white boundary areas of (B) is displayed in a sequential time series, an observer's eyes move along a second direction B, which is inclined from top left to bottom right of the diagram, in accordance with movement of a display picture along the first direction A. Displayed pixel brightness is sustained or held even while one frame display is advanced. Integrating the displayed pixel brightness generates the motion picture contour deterioration, as shown in (D) of FIG.
1
.
FIG. 2
is a simulation diagram illustrating generation of motion picture contour deterioration using a cathode ray tube CRT according to the related art. In
FIG. 2
, (C) illustrates when the motion picture is displayed in the cathode ray tube (CRT) that lacking the hold-type light emission, wherein the pixel is not displayed while the image advances between adjacent frames. Thus, even though an observer's eyes move along the second direction B in accordance with movement of a display picture along the first direction A, no motion picture contour deterioration is generated. In other words, in the impulse-type light emission, such as the cathode ray tube (CRT), black data are displayed between a first frame and an adjacent new frame, so the display image becomes more vivid visually due presence of the black data.
Accordingly, as shown in (C) of both
FIGS. 1 and 2
, an observer's perceived image in the motion picture is vividly displayed in the cathode ray tube (CRT). Thus, the display picture becomes blurred in the LCD device because of the hold-type light emission characteristics of liquid crystal molecules in the LCD device. The difference of such a perceived image results from the integration effect of an image that temporarily continues in the observer's eye due to movement of the image. Accordingly, even though the response speed of the LCD device is relatively fast, the observer sees a blurred screen due to the physical response between movement of the observer's eyes and a stagnant image of each successive frame.
FIG. 3
is a perspective schematic view of a liquid crystal display using a sequential driving backlight unit according to the related art. In
FIG. 3
, a liquid crystal display includes a liquid crystal display panel
10
, a direct backlight unit
20
that radiates light to the liquid crystal display panel
10
using a plurality of lamps
22
a
to
22
n
, a backlight driver
40
that sequentially drives the lamps
22
a
to
22
n
, and a panel driver
30
that drives the liquid crystal display panel
10
and controls the backlight driver
40
.
The direct backlight unit
20
further includes a lamp housing (not shown) where the lamps
22
a
to
22
n
are horizontally arranged in parallel, and a diffusion panel (not shown) covering the whole surface of the lamp housing. In addition, the lamp housing (not shown) not only covers the lamps
22
a
to
22
n
, but also reflects light that progresses toward the rear of the lamps
22
a
to
22
n
to the liquid crystal display panel
10
. Moreover, the diffusion panel (not shown) makes the light radiated from the lamps
22
a
to
22
n
to progress toward the liquid crystal display panel
10
and to be incident at an angle of a wide range. The diffusion panel includes members for light diffusion that are coated on both sides of a transparent resin film.
Accordingly, the lamps
22
a
to
22
n
are arranged in parallel along the horizontal direction and are sequentially driven to be synchronized with a scan speed applied to a gate line (not shown) of the liquid crystal cell
10
. In addition, the lamps
22
a
to
22
n
each radiate light sequentially to a certain area on the liquid crystal display panel
10
, and the backlight driver
40
responds to a control signal from the panel driver
30
to sequentially drive the lamps
22
a
to
22
n.
The panel driver
30
drives a liquid crystal cell of the liquid crystal panel
10
and generates a control signal synchronized with the gate pulse that is applied to the gate line of the liquid crystal display panel
10
. Thus, the lamps
22
a
to
22
n
are each sequentially turned ON in order to be synchronized with the scan speed of the gate line (not shown) of the liquid crystal display panel
10
, thereby radiating light to a certain area of the liquid crystal display panel
10
. Accordingly, the range where one of the lamps
22
a
to
22
n
can irradiate the liquid crystal display panel
10
with uniform brightness is restricted to the certain area. Therefore, the LCD device comprises many lamps such that a thickness of the LCD device increases due to the lamp housing that covers the lamps
22
a
to
22
n.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to a backlight unit and driving apparatus for a liquid crystal display device using the same, and method of driving the same that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide a backlight unit adaptive for rotating a plurality of lamps to prevent motion blurring.
Another object of the present invention is to provide a driving apparatus for a liquid crystal display having a backlight unit adaptive for rotating a plurality of lamps to prevent motion blurring.
Another object of the present invention is to provide a method of driving a backlight unit adaptive for rotating a plurality of lamps to prevent motion blurring.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly point
A Minh Dieu
LG.Philips LCD Co. , Ltd.
Morgan & Lewis & Bockius, LLP
Vannucci James
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