U.S. patent application number 12/796130 was filed with the patent office on 2011-03-03 for display device.
Invention is credited to Seungchoon Bae, Bupsung Jung, Minchul Kim, Sungwoo Kim, Myounghwa Ko, Soonhyung Kwon, Sangtae PARK, Buwan Seo.
Application Number | 20110050668 12/796130 |
Document ID | / |
Family ID | 42370166 |
Filed Date | 2011-03-03 |
United States Patent
Application |
20110050668 |
Kind Code |
A1 |
PARK; Sangtae ; et
al. |
March 3, 2011 |
DISPLAY DEVICE
Abstract
The present invention relates to a display device, which
includes: a backlight unit that is divided into a plurality of
blocks, driven for each of the divided blocks, and includes at
least one optical assembly; a display panel that is disposed above
the backlight unit; a controller that outputs local dimming values
for each block corresponding to the brightness of the blocks in the
backlight unit, in accordance with an image displayed on the
display panel; and a BLU driver that controls the brightness of the
blocks in the backlight unit, using the local dimming values for
each block; in which the optical assembly includes: a first layer;
a plurality of light sources formed on the first layer and emitting
light; a second layer disposed above the first layer to cover the
light sources; and a reflective layer that is disposed between the
first and second layers, and the BLU driver outputs a plurality of
driving signals in response to the input local dimming values for
each block, and the driving signals each control the brightness of
two or more blocks in the blocks of the backlight units.
Inventors: |
PARK; Sangtae;
(Pyeongtaek-si, KR) ; Kim; Minchul;
(Pyeongtaek-si, KR) ; Kim; Sungwoo;
(Pyeongtaek-si, KR) ; Jung; Bupsung;
(Pyeongtaek-si, KR) ; Seo; Buwan; (Pyeongtaek-si,
KR) ; Ko; Myounghwa; (Pyeongtaek-si, KR) ;
Bae; Seungchoon; (Pyeongtaek-si, KR) ; Kwon;
Soonhyung; (Pyeongtaek-si, KR) |
Family ID: |
42370166 |
Appl. No.: |
12/796130 |
Filed: |
June 8, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61237587 |
Aug 27, 2009 |
|
|
|
Current U.S.
Class: |
345/211 ;
345/84 |
Current CPC
Class: |
G02F 1/133603 20130101;
G02F 1/133615 20130101; G09G 3/3426 20130101; G02F 2202/28
20130101; G02B 6/0021 20130101; G09G 2360/16 20130101; G02F
1/133601 20210101; G02F 1/133611 20130101; G09G 2320/0646 20130101;
G02F 1/133612 20210101 |
Class at
Publication: |
345/211 ;
345/84 |
International
Class: |
G06F 3/038 20060101
G06F003/038; G09G 3/34 20060101 G09G003/34 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 24, 2009 |
KR |
10-2009-0113711 |
Claims
1-19. (canceled)
20. A display device comprising: a backlight unit that is divided
into a plurality of blocks and is driven by the divided blocks, and
includes at least one optical assembly; a display panel positioned
over the backlight unit; a controller that outputs local dimming
values corresponding to brightness of the blocks of the backlight
unit, in accordance with an image displayed in the display panel;
and a BLU driver that controls brightness of the blocks of the
backlight unit using the local dimming values, wherein the optical
assembly includes: a first layer; a plurality of light sources that
is are formed on the first layer and emit light, and a light
emitting surface of the light source being formed in the direction
crossing the first layer; a second layer disposed above the first
layer to cover the light sources; and a reflective layer that is
disposed between the first and second layers, and wherein the BLU
driver receives the local dimming values and outputs a plurality of
driving signals, and the driving signals control the brightness of
two or more blocks among the blocks of the backlight unit
respectively.
21. The display device according to claim 20, wherein the display
panel is divided into a plurality of regions and he controller
adjusts the brightness of the blocks in the backlight unit which
correspond to the regions, in accordance with the luminance of the
regions of the display panel.
22. The display device according to claim 21, wherein the
controller includes: an image analyzing unit that measures the
average picture level of an image; and a brightness determining
unit that determines the local dimming values for each block of the
backlight unit, using the measured average picture level of the
image.
23. The display device according to claim 22, wherein the
brightness determining unit determines that brightness of light
source included in the blocks of the backlight unit which
correspond to a first region, using the average picture level of
the image and the average picture level of the first region in the
display panel.
24. The display device according to claim 22, further comprising: a
pixel compensator that adjust the gate of an input image signal,
using the measured average picture level of the image; and a panel
driver that drives the display panel in response to the image
signal outputted from the pixel compensator.
25. The display device according to claim 20, wherein the BLU
driver receives the local dimming values for each block from the
controller, using SPI (Serial Peripheral Interface)
communication.
26. The display device according to claim 20, wherein the first
layer is a substrate with the light sources mounted thereon.
27. The display device according to claim 20, wherein the second
layer includes silicon-based or acryl-based resin.
28. The display device according to claim 20, wherein the second
layer includes a plurality of dispersed particles.
29. The display device according to claim 20, further comprising:
light-shielding patterns that are formed on the second layer to
correspond to the positions of the light sources.
30. The display device according to claim 20, wherein the backlight
unit includes a plurality of the optical assemblies.
31. The display device according to claim 20, wherein the second
layer is 0.1 to 4.5 mm thick.
32. The display device according to claim 20, wherein the light
sources included in the optical assembly are driven in two or more
divided blocks.
33. A display device, comprising: a backlight unit that is divided
into a plurality of blocks and is driven by the divided blocks, and
includes at least one optical assembly; a display panel positioned
over the backlight unit; a controller that outputs local dimming
values corresponding to brightness of the blocks of the backlight
unit, in accordance with an image displayed in the display panel;
and a BLU driver that controls brightness of the blocks of the
backlight unit using the local dimming values, wherein the optical
assembly includes: a first layer; a plurality of light sources that
is are formed on the first layer and emit light, and a light
emitting surface of the light source being formed in the direction
crossing the first layer; a second layer disposed above the first
layer to cover the light sources; and a reflective layer that is
disposed between the first and second layers, and wherein the BLU
driver includes an driving unit, and the driving unit includes a
controller that receives local dimming values from the controller
and a plurality of driver ICs outputting driving signals for
controlling the brightness of the two or more blocks
respectively.
34. The display device according to claim 33, wherein the
controller outputs the local dimming values inputted in parallel,
and then transmits the local dimming values for each block to the
driver ICs.
35. The display device according to claim 33, wherein the driver
ICs transmit driving signal to the light sources included in n
blocks, using n channels.
36. The display device according to claim 33, wherein the BLU
driver includes a plurality of the driving units.
37. The display device according to claim 33, wherein the light
sources included in the optical assembly are driven in two or more
divided blocks.
38. The display device according to claim 33, wherein the backlight
unit includes a plurality of the optical assemblies.
Description
BACKGROUND OF TEE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a display device, in more
detail, a method of driving a backlight unit included in a display
device.
[0003] 2. Description of the Related Art
[0004] Demands for display devices have been increased in various
ways with the development of information society, and a variety of
display devices have been correspondingly studied and used in
recent years, including LCDs (Liquid Crystal Display Device), PDPs
(Plasma Display Panel), ELD (Electro Luminescent Display), VFD
(Vacuum Fluorescent Display).
[0005] Among others, the liquid crystal panel of the LCDs includes
a liquid crystal layer, and a TFT substrate and a color filter
substrate facing each other with the liquid crystal layer
therebetween and cannot emit light by itself, such that it can
display images with the use of light provided from a backlight
unit.
SUMMARY OF THE INVENTION
[0006] It is an object of the present invention to provide a method
of efficiently driving a backlight unit of a display device, and a
display device using the method.
[0007] A display device according to an embodiment of the present
invention includes: a backlight unit that is divided into a
plurality of blocks, driven for each of the divided blocks, and
includes at least one optical assembly; a display panel that is
disposed above the backlight unit; a controller that outputs local
dimming values for each block corresponding to the brightness of
the blocks in the backlight unit, in accordance with an image
displayed on the display panel; and a BLU driver that controls the
brightness of the blocks in the backlight unit, using the local
dimming values for each block; in which the optical assembly
includes: a first layer; a plurality of light sources formed on the
first layer and emitting light; a second layer disposed above the
first layer to cover the light sources; and a reflective layer that
is disposed between the first and second layers, and the BLU driver
outputs a plurality of driving signals in response to the input
local dimming values for each block, and the driving signals each
control the brightness of two or more blocks in the blocks of the
backlight units.
[0008] A display device according to another embodiment of the
present invention includes: a backlight unit that is divided into a
plurality of blocks, driven for each of the divided blocks, and
includes at least one optical assembly; a display panel that is
disposed above the backlight unit; a controller that outputs local
dimming values for each block corresponding to the brightness of
the blocks in the backlight unit, in accordance with an image
displayed on the display panel; and a BLU driver that controls the
brightness of the blocks in the backlight unit, using the local
dimming values for each block, in which the optical assembly
includes: a first layer; a plurality of light sources formed on the
first layer and emitting light; a second layer disposed above the
first layer to cover the light sources; and a reflective layer that
is disposed between the first and second layers, the BLU driver
includes an driving unit, and the driving unit includes a
controller that receives local dimming value for each block from
the controller and a plurality of driver ICs outputting driving
signals for controlling the brightness of the two or more
blocks.
[0009] According to a backlight unit of an embodiment of the
present invention, it is possible to reduce the thickness of a
display device, simplify the manufacturing process of the display
device and improve the external appearance by disposing the
backlight unit in close contact to a display panel. Further, it is
possible to improve the contrast of a displayed image, using a
partial driving method, such as local dimming.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is an exploded perspective view showing a
configuration of a display device.
[0011] FIG. 2 is a cross-sectional view schematically showing a
configuration of a display module.
[0012] FIG. 3 is a cross-sectional view showing a configuration of
a backlight unit according to a first embodiment of the present
invention.
[0013] FIG. 4 is a cross-sectional view showing a configuration of
a backlight unit according to a second embodiment of the present
invention.
[0014] FIG. 5 is a cross-sectional view showing a configuration of
a backlight unit according to a third embodiment of the present
invention.
[0015] FIG. 6 is a cross-sectional view showing a configuration of
a backlight unit according to a fourth embodiment of the present
invention.
[0016] FIG. 7 is a cross-sectional view showing a configuration of
a backlight unit according to a fifth embodiment of the present
invention.
[0017] FIG. 8 is a plan view showing an embodiment of an
arrangement structure of a plurality of light sources in a
backlight unit according to the present invention.
[0018] FIG. 9 is a plan view showing an embodiment of a positional
relationship between the light sources arrange in the backlight
unit.
[0019] FIG. 10 is a plan view showing an embodiment of the shape of
a light-shielding pattern formed in the backlight unit.
[0020] FIG. 11 is a cross-sectional view showing a configuration of
a backlight unit according to a sixth embodiment of the present
invention.
[0021] FIG. 12 is a cross-sectional view showing a configuration of
a display device according to an embodiment of the present
invention.
[0022] FIG. 13 is a block diagram schematically showing the
configuration of the display device according to a first embodiment
of the present invention.
[0023] FIG. 14 is a block diagram schematically showing the
configuration of the display device according to a second
embodiment of the present invention.
[0024] FIG. 15 is a graph showing a first embodiment of a method of
determining brightness of a light source according to a average
luminance level of an image.
[0025] FIG. 16 is a graph showing a second embodiment of a method
of determining brightness of a light source according to the
average luminance level of an image.
[0026] FIG. 17 is a graph showing an embodiment of a method of
determining a compensating value of an image signal to the average
luminance level of an image.
[0027] FIG. 18 is a block diagram schematically showing a
configuration of a BLU driver.
[0028] FIG. 19 is a block diagram showing an embodiment of the
configuration of the BLU driver.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0029] The present invention is described hereafter with reference
to the accompanying drawings. The embodiment described hereafter
can be modified in various ways and the technical spirit of the
embodiments is not limited to the following description. The
embodiments are provided for those skilled in the art to fully
understand the present invention. Therefore, the shape and size of
the components shown in the drawings may be exaggerated for more
clear explanation.
[0030] FIG. 1 is an exploded perspective view showing the
configuration of a display device.
[0031] Referring to FIG. 1, a display device 1 includes a display
module 20, a front cover 30 and a back cover 40 which cover the
display module 20, and fixing members 50 that fixes the display
module to the front cover 30 and/or the back cover 40.
[0032] Meanwhile, the front cover 30 may include a front panel (not
shown) made of a transparent material transmitting light and the
front panel is disposed at a predetermined distance from the
display module 20, in detail, at the front of a display panel (not
shown) included in the display module to protect the display module
20 from an external shock and transmit light emitted from the
display module 20 such that an image displayed on the display
module 20 can be seen from the outside.
[0033] The fixing members 50 have one side fixed to the front cover
30 by fasteners, such as screws, and the other side supporting the
display module 20 with respect to the front cover 30 such that the
display module 20 can be fixed to the front cover 30.
[0034] Although the fixing member 50 exemplified by a long plate in
this embodiment, it may be possible to implement a configuration in
which the display module 20 is fixed to the front cover 30 or the
back cover 40 by fasteners, without the fixing members 50.
[0035] FIG. 2 is a cross-sectional view schematically showing the
configuration of a display device according to an embodiment of the
present invention, in which a display module 20 of the display
device may include a display panel 100 and a backlight unit
200.
[0036] Referring to FIG. 2, the display panel 100 includes a color
filter substrate 110 and a TFT (Thin Film Transistor) substrate 120
facing and bonded to each other with a uniform gap, and a liquid
crystal layer (not shown) may be disposed between the substrates
110 and 120.
[0037] The color filter substrate 110 includes a plurality of
pixels composed of red R, green G, and blue B sub-pixels and can
create an image corresponding to the red, green, or blue color when
light is applied.
[0038] Meanwhile, although the pixels may be composed of the red,
green, and blue sub-pixels, this configuration is not necessarily
limited thereto and may be implemented in various combinations,
such as when one pixel is composed of red, green, blue, and white W
sub-pixels.
[0039] The TFT substrate 120 is a switching element that can switch
pixel electrodes (not shown). For example, a common electrode (not
shown) and the pixel electrode can change the arrangement of
molecule in the crystal layer in response to a predetermined
voltage applied from the outside.
[0040] The liquid crystal layer includes a plurality of liquid
crystal molecules and the liquid crystal molecules change the
arrangement in response to the voltage difference generated between
the pixel electrode and the common electrode. Accordingly, the
light emitted from the backlight unit 200 can travel into the color
filter substrate 110 by changes in the arrangement of the liquid
crystal molecules.
[0041] Further, an upper polarizer 130 and a lower polarizer 140
may be disposed on and beneath, respectively, the display panel,
and in detail, the upper polarizer 130 may be disposed on the color
filter substrate 110 and the lower polarizer 140 may be disposed
beneath the TFT substrate 120.
[0042] On the other hand, a gate generating driving signals for
driving the panel 100 and a data driving unit (not shown) may be
provided at the sides of the display panel 100.
[0043] The structure and configuration, described above, of the
display panel 100 are just exemplified and the embodiment may be
modified, added, and removed within the spirit of the present
invention.
[0044] As shown in FIG. 2, the display device according to an
embodiment of the present invention may be configured by disposing
the backlight unit 200 in close contact to the display panel
100.
[0045] For example, the backlight unit 200 may be bonded and fixed
to the lower surface of the display panel, in detail, to the lower
polarizer 140, and for this configuration, an adhesive layer (not
shown) may be provided between the lower polarizer 140 and the
backlight unit 200.
[0046] By disposing the backlight unit 200 in close contact to the
display panel 100, as described above, it is possible to reduce the
entire thickness of the display device to improve the external
appearance and it is also possible to simplify the structure of the
display device and the manufacturing process by removing a
structure for fixing the backlight unit 200.
[0047] Further, since the space between the backlight unit 200 and
the display panel 100 is removed, it is possible to prevent the
display device from the display device and the image quality of
display images from deteriorating due to foreign substances
inserted in the space.
[0048] According to an embodiment of the present invention, the
backlight unit 200 may be formed by stacking a plurality of
function layers and at least one of the function layers may be
provided with a plurality of light sources (not shown).
[0049] Further, it is preferable that the backlight unit 200, in
detail, the layers of the backlight unit 200 are made of a flexible
material in order to fix the backlight unit 200 in close contact to
the lower surface of the display panel 100, as described above.
[0050] Further, a bottom cover (not shown) where the backlight unit
200 is seated may be provided under the backlight unit 200.
[0051] According to an embodiment of the present invention, the
display panel 100 may be divided into a plurality of regions and
the brightness of the light emitted from corresponding regions of
the backlight unit 200, that is, the brightness of corresponding
light sources is adjusted in response to the gray peak values or
color coordinate signals of the divided regions, such that the
luminance of the display panel 100 can be adjusted.
[0052] For this configuration, the backlight unit 200 may operate
in a plurality of driving regions divided to correspond to the
divided regions of the display panel 100.
[0053] FIG. 3 is a cross-sectional view showing the configuration
of a backlight unit according to a first embodiment of the present
invention, in which the backlight unit 200 may include a first
layer 210, light sources 220, a second layer 230, and a reflective
layer 240.
[0054] Referring to FIG. 3, the light sources 220 may be formed on
the first layer 210 and the second layer 230 may be disposed above
the first layer 210 to cover the light sources 220.
[0055] The first layer 210 may be a substrate on which the light
sources 220 are mounted and may be provided with an adapter (not
shown) supplying power and an electrode pattern (not shown) for
connecting the light sources 220. For example, a carbon natotube
electrode pattern (not shown) may be formed on the substrate to
connect the light sources 220 with the adapter (not shown).
[0056] On the other hand, the first layer 210 may be a PCB (Printed
Circuit Board) that is made of polyethylene terephthalate, glass,
polycarbonate, and silicon etc. to mount the light sources 220 in a
film shape.
[0057] The light source 220 can emit light at a predetermined
directional angle from a predetermined direction and the
predetermined direction may be a direction in which the light
emitting surface of the light source 220 is aligned.
[0058] According to an embodiment of the present invention, the
light source 220 may be formed of an LED (Light Emitting Diode) and
may include a plurality of LEDs. For example, the light source 220
formed of a light emitting diode can emit light at about
120.degree. directional angel from the direction in which the light
emitting surface is aligned.
[0059] To be specific, the LED package of the light source 220 can
be classified into a top view type and a side view type in
accordance with the direction in which the light emitting surface
is aligned, and the light sources 220 according to an embodiment of
the present invention can be formed of at least one of a top view
type LED package with the light emitting surface upward and a side
view type LED package with the light emitting surface at a
side.
[0060] The light source 220 according to an embodiment of the
present invention can be formed of the side view type LED
package.
[0061] In this case, the light emitting surface of the light source
220 can be formed in the direction crossing the first layer
210.
[0062] According to an embodiment of the present invention, the
light emitting surface of the light source 220 and the first layer
210 may cross at a right angle.
[0063] Further, the light source 220 may be formed of a color LED
emitting at least one of colors including red, blue, and green, or
a white LED. Furthermore, the color LED may include at least one of
a red LED, a blue LED, and a green LED, and it is possible to
change the arrangement of the light emitting diodes and light
emitted from the diodes within the scope of the embodiment.
[0064] On the other hand, the second layer 230 disposed above the
first layer 210 to cover the light sources 220 transmits and
diffuses light emitted from the light sources 220 such that the
light emitted from the light sources 220 uniformly travels to the
display panel 100.
[0065] The reflective layer 240 reflecting the light emitted from
the light sources 220 may be disposed between the first layer 210
and the second layer 230, in detail, on the first layer 210. The
reflective layer 240 reflects again the light total-reflecting from
the interface of the second layer 230 such that the light emitted
from the light sources 220 can be diffused wider.
[0066] The reflective layer 240 may be a synthetic resin sheet with
white pigments, such as titanium dioxide, diffused therein, with a
metal film deposited on the surface, or with bubbles therein to
disperse light, and silver (Ag) may be coated on the surface to
increase reflectivity. Further, the reflective layer 240 may be
coated on the first layer 210, a substrate.
[0067] The second layer 230 may be made of a light-transmissive
material, for example, a silicon-based or acryl-based resin. The
second layer 230, however, is not limited to the materials
described above, and may be made of various resins.
[0068] Further, the second layer may be made of a resin having
about 1.4 to 1.6 refractive index in order for the backlight unit
200 has uniform luminance while diffusing the light emitted from
the light sources 220.
[0069] For example, the second layer 230 may be made of any one
material selected from a group of polyethylene terephthalate,
polycarbonate, polypropylene, polyethylene, polystyrene, polyepoxy,
silicon, and acryl.
[0070] The second layer may include a polymer resin having
predetermined adhesive property to be firmly fixed to the light
sources 220 and the reflective layer 240. For example, the second
layer 230 may include acryl-based, urethane-based, epoxy-based, and
melamine-based unsaturated polyester, methyl methacrylate, ethyl
methacrylate, isobutyl methacrylate, n-butyl methacrylate, n-butyl
methyl methacrylate, acryl acid, methacrylic acid, hydroxyethyl
methacrylate, hydroxyl propyl methacrylate, hydroxylethyl acrylate,
acrylamide, methylolacrylamide, glycidolmethacrylate,
ethylacrylate, isobutyl acrylate, n-butyl acrylate, 2-ethylhexyl
acrylate polymer, copolymer, or terpolymer.
[0071] The second layer 230 may be formed by applying and hardening
liquid-state or gel-state resin above the first surface 210 with
the light sources 220 and the reflective layer 240 thereon, or may
be separately formed and then bonded onto the first layer 210.
[0072] Meanwhile, the larger the thickness (a) of the second layer
230, the wider the light emitted from the light sources 200 is
diffused, such that light can be supplied to the display panel 100
at uniform luminance from the backlight unit 200. On the contrary,
the larger the thickness (a) of the second layer 230, the more the
amount of light absorbed in the second layer 230 increases, such
that the entire luminance of the light supplied from the backlight
unit 200 to the display panel 100 may be reduced.
[0073] Therefore, it is preferable that the thickness (a) of the
second layer 230 is about 0.1 to 4.5 mm to supply light having
uniform luminance without largely reducing the luminance of the
light supplied from the backlight unit 200 to the display panel
100.
[0074] The configuration of the backlight unit 200 according to an
embodiment of the present invention is described hereafter in
detail by way of an example that the first layer 210 of the
backlight unit 200 is a substrate with the plurality of light
sources 220 and the second layer 220 is a resin layer made of a
predetermined resin.
[0075] FIG. 4 is a cross-sectional view showing the configuration
of a backlight unit according to a second embodiment of the present
invention and, in the configuration of the backlight unit 200 shown
in FIG. 4, the same parts as those described in connection with
FIGS. 2 and 3 are not described below.
[0076] Referring to FIG. 4, a plurality of light sources 220 may be
mounted on a substrate 210 and a resin layer 230 may be disposed
above the substrate 210. Further, a reflective layer 240 may be
formed between the substrate 210 and the resin layer 230, in
detail, on the substrate 210.
[0077] Further, as shown in FIG. 4, the resin layer 230 may include
a plurality of dispersed particles 231 and the dispersed particles
231 can disperse or refract incident light such that the light
emitted from the light sources 220 is diffused wider.
[0078] The dispersed particles 231 may be made of a material having
refractive index different from the material of the resin layer
230, in detail, a material having refractive index higher than a
silicon-based or acryl-based resin of the resin layer 230, in order
to disperse or refract the light emitted from the light sources
220.
[0079] For example, the dispersed particles 231 may be made of
polymethyl methacrylate/styrene copolymer (MS), polymethyl
methacrylate (PMMA), polystyrene (PS), silicon, titanium dioxide
(TiO2), silicon dioxide (SiO2) etc., or may be made of combination
of those compounds.
[0080] Alternatively, the dispersed particles 231 may be made of a
material having refractive index smaller than the material of the
resin layer 230, for example, may be made by creating bubbles in
the resin layer 230.
[0081] However, the material for the dispersed particles 231 is not
limited to the materials described above and a variety of polymers
or inorganic particles may be used.
[0082] According to an embodiment of the present invention, the
resin layer 230 may be made by mixing the dispersed particles 231
with liquid-state or gel-state resin, and then applying and
hardening the mixture on the first layer 210 with the light sources
220 and the reflective layer 240 thereon.
[0083] Referring to FIG. 4, an optical sheet 250 may be disposed on
the resin layer 230, and for example, the optical sheet 250 may
include a prism sheet 251 and a diffusing sheet 252.
[0084] In this case, the sheets are bonded in close contact with
each other without a gap in the optical sheet 250, such that it is
possible to minimize the thickness of the optical sheet 250 or the
backlight unit 200.
[0085] On the other hand, the lower surface of the optical sheet
250 may be in close contact to the resin layer 230 and the upper
surface may be in close contact to the lower surface of the display
panel 100, in detail, to the lower polarizer 140.
[0086] The diffusing sheet 252 diffuses the incident light to
prevent the light traveling out of the resin layer 230 from
partially collecting, thereby keeping the luminance of the light
uniform. Further, the prism sheet 251 can collect the light
traveling out of the diffusing sheet 252 such that the light can
travel perpendicularly into the display panel 100.
[0087] According to another embodiment of the present invention, in
the optical sheet 250 described above, for example, at least one of
the prism sheet 251 and the diffusing sheet 252 may be removed, or
various function layers may be further included, other than the
prism sheet 251 and the diffusing sheet 252.
[0088] FIG. 5 is a cross-sectional view showing the configuration
of a backlight unit according to a third embodiment of the present
invention and, in the configuration of the backlight unit 200 shown
in FIG. 5, the same parts as those described in connection with
FIGS. 2 and 4 are not described below.
[0089] Referring to FIG. 5, a plurality of light sources 220 in the
backlight unit 200 are arranged with the light emitting surfaces
aligned at the sides, such that they can emit light to the sides,
that is, in the direction in which a substrate 210 or a reflective
layer 240 extends.
[0090] For example, the light sources 220 may be formed by a side
view type LED package, and accordingly, it is possible to reduce
the problem that the light sources 220 appear like hot spots on the
image and make the display device as well as the backlight unit 200
slim by decreasing the thickness (a) of a resin layer 230.
[0091] FIG. 6 is a cross-sectional view showing the configuration
of a backlight unit according to a fourth embodiment of the present
invention, in which a plurality of resin layers 230 and 235 may be
included in the backlight unit 200.
[0092] Referring to FIG. 6, the light emitted from the side of a
light source 220 can travel to the region where an adjacent light
source 225 is disposed, through the first resin layer 230.
[0093] A portion of the light traveling through the first resin
layer 230 can be emitted upward to the display panel 100, and for
this configuration, the first resin layer 230, as described with
reference to FIG. 4, may include the plurality of dispersed
particles 231 to disperse or refract the light upward.
[0094] Further, a portion of the light emitted from the light
source 220 can travel into the reflective layer 240, and as
described above, the light that have traveled in the reflective
layer 240 can be reflected and diffused upward.
[0095] Meanwhile, light having large luminance can be observed in
the image, because a large amount of light can be emitted from the
region around the light source 220 by strong diffusion around the
light source or the light emitted substantially upward from the
light source 220.
[0096] Therefore, as shown in FIG. 6, first light-shielding
patterns 260 are formed on the first resin layer 230 to reduce the
luminance of the light emitted from the region around the light
source 220, such that light can be emitted at uniform luminance
from the backlight unit 200.
[0097] For example, the first light-shielding pattern 260 can be
formed on the first resin layer 230 to correspond to the position
of the plurality o flight sources 220, such that it can reduce the
luminance of the light emitted upward by blocking a portion of the
light emitted from the light source 220 and transmitting the
rest.
[0098] In detail, the first light-shielding pattern 260 may be made
of titanium dioxide (TiO.sub.2), in which it can reflect downward a
portion of the incident light from the light source 220 and
transmitting the rest.
[0099] According to an embodiment of the present invention, a
second resin layer 235 may be disposed on the first resin layer
230. The second resin layer 235 may be made of a material the same
as or different from the first resin layer 230 and can improve the
uniformity in luminance of the light from the backlight unit by
diffusing light emitted upward through the first resin layer
230.
[0100] The second resin layer 235 may be made of a material having
the same refractive index as the material of the first resin layer
230, or may be made of a material having different refractive
index.
[0101] For example, when the second resin layer 235 is made of a
material having larger refractive index than the first resin layer
230, the light emitted through the first resin layer 230 can be
diffused wider.
[0102] On the contrary, when the second resin layer 235 is made of
a material smaller than the first resin layer 230, it is possible
to improve reflectivity of the light emitted through the first
resin layer 230 and then reflecting from the lower surface of the
second resin layer 235, such that the light emitted from the light
source 220 can easily travel along the first resin layer 230.
[0103] Meanwhile, the first resin layer 230 and the second resin
layer 235 may each include a plurality of dispersed particles, in
which the density of the dispersed particles included in the second
resin layer 235 may be larger than that of the dispersed particles
included in the first resin layer 230.
[0104] When the dispersed particles are included at higher density
in the second resin layer 235, as described above, it is possible
to diffuse wider the light emitted upward through the first resin
layer 230, and accordingly, the light emitted from the backlight
unit 200 can be made uniform in luminance.
[0105] On the other hand, as shown in FIG. 6, second
light-shielding patterns 265 may be formed on the second resin
layer 235 to make the light emitted through the second resin layer
235 uniform in luminance.
[0106] For example, when large luminance is observed in the image
by the light emitted upward through the second resin layer 235 and
collecting to a specific portion, it is possible to form the second
light-shielding pattern 265 at the region corresponding to the
specific portion on the upper surface of the second resin layer
235, and accordingly, it is possible to make the light emitted from
the backlight unit 200 uniform in luminance by reducing the
luminance of the light at the specific portion.
[0107] The second light-shielding pattern 265 may be made of
titanium dioxide (TiO.sub.2), in which a portion of the light
emitted through the second resin layer 235 may be reflected
downward from the second light-shielding pattern 265 and the rest
may transmitting it.
[0108] FIG. 7 is a cross-sectional view showing the configuration
of a backlight unit according to a fifth embodiment of the present
invention and, in the configuration of the backlight unit 200 shown
in FIG. 7, the same parts as those described in connection with
FIGS. 2 to 6 are not described below.
[0109] A plurality of patterns 241 may be formed on a reflective
layer 240 so that the light emitted from a light source 220 can
easily travel to an adjacent light source 225.
[0110] Referring to FIG. 7, the plurality of patterns 241
protruding upward may be formed on the reflective layer 240, such
that the light emitted from the light source 220 and then travels
into the patterns 241 can be dispersed and reflected in the
traveling direction.
[0111] Meanwhile, as shown in FIG. 7, the further from the light
source 220, that is, the closer to the adjacent light source 225,
the larger the density of the patterns 241 on the reflective layer
240.
[0112] For example, the further from the light source 220 emitting
light toward the reflective layer 240, the larger the density of
the patterns 241.
[0113] Accordingly, it is possible to prevent the luminance of the
light emitted upward from a region far from the light source 220,
that is, a region close to the adjacent light source 225, from
being reduced, such that the luminance of the light supplied from
the backlight unit 200 can be kept uniform.
[0114] Further, the patterns 241 may be made of the same material
as the reflective layer 240, in which the patterns 241 can be
formed by machining the upper surface of the reflective layer
240.
[0115] Alternatively, the patterns 241 may be made of a different
material from the reflective layer 240, and for example, the
patterns 241 may be formed on the reflective layer 240 by
dispersing or coating particles on the reflective layer 240.
[0116] Further, the patterns 241 may be formed in various shapes,
including a prism, without being limited to that shown in FIG.
7.
[0117] In addition, the patterns 241 may be depressed on the
reflective layer 240 and may be formed only at predetermined
portions on the reflective layer 240.
[0118] FIG. 8 is a plan view showing the front shape of a backlight
unit according to an embodiment of the present invention, which
exemplifies an arrangement structure of a plurality of light
sources in the backlight unit 200.
[0119] Referring to FIG. 8, the backlight unit 200 may include two
or more light sources which emit light in different directions.
[0120] For example, the backlight unit 200 may include first light
sources 220 and second light sources 221 which emit light from the
side in parallel with the x-axis, in which the first light sources
220 and the second light sources 221 may be arranged across the
x-axis direction in which light is emitted, that is, arranged
adjacent to each other in the y-axis direction.
[0121] In other words, as shown in FIG. 8, the second light sources
221 may be arranged adjacent to the first light sources 220 in the
diagonal direction.
[0122] Meanwhile, the first light sources 220 and the second light
sources 221 can emit light in opposite directions, that is, the
first light sources 220 can emit light opposite to the x-axis
direction and the second light sources 221 can emit light in the
x-axis direction.
[0123] In this configuration, the light sources in the backlight
unit 200 can emit light to the sides and a side view type LED
package can be used to implement the configuration.
[0124] On the other hand, as shown in FIG. 8, the light sources of
the backlight unit 200 may be arranged in two or more rows and the
two or more light sources in the same row can emit light in the
same direction.
[0125] For example, the light sources at the left and right sides
of the first light source 220 can emit light in the same direction
as the first light source 220, that is, opposite to the x-axis
direction, and the light sources at the left and right sides of the
second light source 221 can emit light in the same direction as the
second light source 221, that is, in the x-axis direction.
[0126] It is possible to prevent the luminance of the light from
concentrating or reducing in a predetermined region of the
backlight unit 200 by arranging the light sources adjacent in the
y-axis direction, for example, by aligning the light-emitting
direction of the first light sources 220 and the second light
sources 221 in the opposite directions.
[0127] That is, the light emitted from the first light source 220
can be weakened while traveling to an adjacent light source, and
accordingly, the further from the first light source 220, the more
the luminance of the light emitted from the corresponding region to
the display panel may be weakened.
[0128] Therefore, it is possible to compensate the concentration of
luminance of the light in the region adjacent to the light source
with the weakening of luminance of the light in the region far from
the light source by arranging the first light source 220 and the
second light source 221 such that the light-emitting direction are
opposite, as shown in FIG. 8, and it is correspondingly possible to
make the luminance of the light emitted from the backlight unit 200
uniform.
[0129] Referring to FIG. 9, the first light sources 220 and the
second sources 221 may be disposed at a predetermined distance d1
from each other along the y-axis perpendicular to the x-axis along
which light is emitted.
[0130] As the distance d1 between the first light source 220 and
the second light source 221, there may be a region where the light
emitted from the first light source 220 or the second light source
cannot reach, such that the luminance of the light may be largely
decreased in the region.
[0131] Meanwhile, as the distance between the first light source
220 and the second light source 221 decreases, there may be
interference between light emitted from the first light source 220
and the second light source 221, in which division driving
efficiency of the light sources may be reduced.
[0132] Therefore, the distance d1 between two adjacent light
sources in the direction crossing the light-emitting direction,
that is, between the first light source 220 and the second light
source 221 may be 9 to 27 mm, in order to implement uniform
luminance of the light emitted from the backlight unit 200 while
reducing the interference between the light sources.
[0133] Further, a third light source 222 may be disposed adjacent
to the first light source 220 in the x-axis direction, at a
predetermined distance d2 from the first light source 220.
[0134] Meanwhile, the light-directional angle .theta. from the
light source and the light-directional angle .theta.' in the resin
layer 230 may have the following Equation 1 in accordance with
Snell's law.
n 1 n 2 = sin .theta. ' sin .theta. [ Equation 1 ] ##EQU00001##
[0135] On the other hand, considering that the portion where light
is emitted from the light source is an air layer (1 of refractive
index) and the light-directional angle .theta. from the light
source is generally 60.degree., the light-directional angle in the
resin layer 230 may have the value expressed by the following
Equation 2, in accordance with Equation 1.
sin .theta. ' = sin 60 .degree. n 2 [ Equation 2 ] ##EQU00002##
[0136] Further, when the resin layer 230 is made of acryl-based
resin, such as PMMA (polymethyl methacrylate), it has refractive
index of about 1.5, such that the light-directional angle .theta.'
of about 35.5.degree. in the resin layer 230 in accordance with
Equation 2.
[0137] As described with reference to Equations 1 and 2, the
directional angle of the light emitted from the light source in the
resin layer 230 may be less than 45.degree., and accordingly, the
range of the light emitted from the light source and traveling in
the y-axis direction may be smaller than the x-axis direction.
[0138] Therefore, the distance d1 between two light sources
adjacent to each other across the light-emitting direction, that
is, between the first light source 220 and the second light source
221 may be smaller than the distance d2 between two light sources
adjacent to each other in the light-emitting direction, that is,
between the first light source 220 and the third light source 222,
such that the luminance of the light emitted from the backlight
unit 200 can be uniform.
[0139] Meanwhile, considering the distance d1 between the first
light source 220 and the second light source 221 having the above
range, the distance d2 between two light sources adjacent to each
other in the light-emitting direction, that is, between the first
light source 220 and the third light source 222 may be 5 to 22 m,
in order to reduce interference between the light sources and make
the luminance of the light emitted from the backlight unit 200
uniform.
[0140] Referring to FIG. 9, the second light source 221 may be
disposed to correspond to a predetermined position between the
first light source 220 and the third light source 222 adjacent to
each other in the light-emitting direction, that is, the x-axis
direction.
[0141] In other words, the second light source 221 may be disposed
adjacent to the first light source 220 and the third light source
222 in the y-axis direction, on the line (l) passing through
between the first light source 220 and the third light source
222.
[0142] In this case, the distance d3 between the line (l) on which
the second light source 221 is disposed and the first light source
220 may be larger than the distance d4 between the line (l) and the
third light source 222.
[0143] The light emitted from the second light source 221 travels
toward the third light source 222, such that the luminance of the
light emitted toward the display panel 100 may weaken in a region
around the third light source 222.
[0144] Therefore, it is possible to compensate the weakening of the
luminance of light in a region around the third light source 222
with the luminance of the light concentrating in a region around
the second light source 221, by disposing the second light source
221 closer to the third light source 222 than the first light
source 220, as described above.
[0145] FIG. 10 is a plan view showing an embodiment of the shape of
a light-shielding pattern formed in a backlight unit, in the
configuration of the backlight unit 200 shown in FIG. 10, the same
parts as those described in connection with FIGS. 2 to 9 are not
described below.
[0146] Referring to FIG. 10, a plurality of light-shielding
patterns 260 may be formed to correspond to the positions of a
plurality of light sources 220.
[0147] For example, as shown in FIG. 6, light-shielding patterns
260 are formed on the first resin layer 230 covering the lights
sources to reduce the luminance of the light emitted from the
region around the light source 220, as described above, such that
light can be emitted at uniform luminance from the backlight unit
200.
[0148] According to an embodiment of the present invention, as
shown in FIG. 10, circular or elliptical light-shielding patterns
260 may be made of titanium dioxide TiO2 on the resin layer 230 to
correspond to the positions of the light sources 220, such that it
is possible to block a portion of the light emitted upward from the
light sources 220.
[0149] FIG. 11 is a cross-sectional view showing the configuration
of a backlight unit according to a sixth embodiment of the present
invention.
[0150] Referring to FIG. 11, first layer 210, a plurality of light
sources 220 formed on the first layer, a second layer 230 covering
the light sources 220, and a reflective layer 240, as described
with reference to FIG. 10, may be formed in one optical assembly
10, and a backlight unit 200 may be composed of a plurality of the
optical assemblies 10.
[0151] Meanwhile, N and M optical assemblies 10 of the backlight
unit 200 may be disposed in a matrix in the x-axis and y-axis
directions, respectively, where N and M are integers of 1 or
more.
[0152] As shown in FIG. 11, twenty one optical assemblies 10 may be
arranged in a 7.times.3 matrix in the backlight unit 200.
[0153] The configuration shown in FIG. 11, however, is an example
for explaining the backlight unit according to the present
invention and the present invention is not limited thereto and may
be modified in accordance with the image size etc. of the display
device.
[0154] For example, for a 47 inch display device, the backlight
unit 200 can be implemented by arranging two hundred forty optical
assemblies in a 24.times.10 matrix.
[0155] Each of the optical assemblies may be an individual assembly
and a module type backlight unit may be formed by disposing them
close to each other. The module type backlight unit is a backlight
member and can supply light to the display panel 100.
[0156] As described above, the backlight unit 200 can be driven in
an entire driving type and a partial driving type, such as local
dimming and impulsive types. The driving type of the backlight unit
200 may be modified in various ways in accordance with the circuit
design and is not modified thereto. As a result, according to the
embodiment, it is possible to the contrast and make clear the dark
portion and bright portion in the image, thereby improving the
image quality.
[0157] That is, the backlight unit is driven in a plurality of
divided driving regions and it is possible to brightness and
definition by reducing the luminance at the dark portion and
increasing the luminance at the bright portion in the image, with
the luminance of the division driving region linked with the
luminance of an image signal.
[0158] For example, it is possible to emit light upward by
individually driving only some of the optical assemblies 10 shown
in FIG. 11, and for this configuration, the lights sources 220
included in the optical assemblies 10 can be individually
controlled.
[0159] On the other hand, the region corresponding to one optical
assembly 10 in the display panel 10 may be divided into two or more
blocks, and the display panel 100 and the backlight unit 200 may be
driven in the divided block unit.
[0160] It is possible to simplify the manufacturing process of the
backlight unit 200, minimize losses that may be generated in the
manufacturing process, and improve productivity, by combining the
optical assemblies 10 to form the backlight unit 200. Further, it
is possible to manufacture backlight units having various sizes by
standardizing the optical assembly of the backlight unit 200 for
mass production.
[0161] Meanwhile, since when any one of the optical assemblies 10
of the backlight unit 200 fails, it has only to replace the failed
optical assembly without replacing the entire backlight unit, the
replacement is easy and the cost needed to replace the part is
reduced.
[0162] FIG. 12 is a cross-sectional view showing the configuration
of a display device according to an embodiment of the present
invention, in the configuration of the display device shown in the
figure, the same parts as those described with reference to FIGS. 1
to 11 are not described below.
[0163] Referring to FIG. 12, a display panel 100 including a color
filter substrate 110, a TFT substrate 120, an upper polarizer 130,
and a lower polarizer 140 and a backlight unit 200 including a
substrate 210, a plurality of light sources 220, and a resin layer
230 may be disposed in close contact with each other.
[0164] For example, an adhesive layer 150 is provided between the
backlight unit 200 and the display panel 100, such that the
backlight unit 200 can be bonded and fixed to the lower surface of
the display panel 100.
[0165] In more detail, the upper surface of the backlight unit 200
can be bonded to the lower surface of the lower polarizer 140 by
the adhesive layer 150.
[0166] The backlight unit 200 may further include a diffusing sheet
(not shown) and the diffusing sheet (not shown) may be disposed in
close contact to the upper surface of the resin layer 230. In this
configuration, the adhesive layer 150 may be provided between the
diffusing sheet (not shown) of the backlight unit 200 and the lower
polarizer 140 of the display panel 100.
[0167] Further, a bottom cover 270 may be disposed under the
backlight unit 200, and for example, as shown in FIG. 12, the
bottom cover 270 may be in close contact to the lower surface of
the substrate 210. The bottom cover 270 may be a protective film
protecting the backlight unit 200.
[0168] Meanwhile, the display device may include a display module
20, in detail, a power supplier 400 that supplies driving voltage
to the display panel 100 and the backlight unit 200, and for
example, the light sources 220 of the backlight unit 200 can be
driven to emit light by the voltage supplied from the power
supplier 400.
[0169] As shown in FIG. 12, the power supplier 400 may be fixed to
a back cover 40 covering the rear side of the display module 20 to
be stably supported and fixed.
[0170] According to an embodiment of the present invention, a first
connector 410 may be formed on the substrate 210, and for this
configuration, a hole may be formed in the bottom cover 270 to
insert the first connector 410.
[0171] The first connector 410 electrically connects the light
source 220 with the power supplier 400 such that driving voltage is
supplied from the power supplier 400 to the light source 220.
[0172] For example, the first connector 410 may be disposed beneath
the substrate 210 and connected with the power supplier 400 through
a first cable 420 to transmit driving voltage supplied from the
power supplier 400 through the first cable 420 to the light source
220.
[0173] An electrode pattern (not shown), for example, a carbon
nanotube electrode pattern may be formed on the substrate 210. The
electrode formed on the substrate 210 can electrically connect the
first connector 410 with the light source 220, in contact with the
electrode formed in the light source 212.
[0174] Further, the display device may include a controller 500
controlling the display panel 100 and the backlight unit 200, and
for example, the controller 500 may be a timing controller.
[0175] The timing controller controls the driving timing of the
display panel 100, and in detail, creates signals for controlling
the driving timings of a data driving unit (not shown), a gamma
voltage generating unit (not shown), and a gate driving unit (not
shown) included in the display panel 100 and transmits the signals
to the display panel 100.
[0176] Meanwhile, the timing controller can supply a signal for
controlling the driving timing of the light sources 220 to drive
the backlight unit 200, in detail, the light sources 220, to the
backlight unit 200, when the display panel 100 is driven.
[0177] As shown in FIG. 12, the controller 500 may be fixed to a
back cover 40 covering the rear side of the display module 20 to be
stably supported and fixed.
[0178] According to an embodiment of the present invention, a
second connector 510 may be formed on the substrate 210, and for
this configuration, a hole may be formed in the bottom cover 270 to
insert the second connector 510.
[0179] The second connector 510 electrically connects the substrate
210 with the controller 500 such that a control signal outputted
from the controller 500 can be transmitted to the substrate
210.
[0180] For example, the second connector 510 may be disposed
beneath the substrate 210 and connected with the controller 500
through a second cable 520 to transmit a control signal supplied
from the controller 500 through the second cable 520 to the
substrate 210.
[0181] Meanwhile, a light driving unit (not shown) may be formed on
the substrate and can drive the light sources 220, using the
control signal supplied from the controller 500 through the second
connector 510.
[0182] The configuration of the display device shown in FIG. 12 is
provided just as an embodiment and accordingly, if needed, it is
possible to change the position and the number of the power
supplier 400, the controller 500, the first and second connectors
410 and 510, and the first and second cables 420 and 520.
[0183] For example, the first and second connectors 410 and 510 may
be provided for each of the optical assemblies 10 of the backlight
unit, as shown in FIG. 11, and the power supplier 400 or the
controller 500 may be disposed beneath the bottom cover 270.
[0184] FIG. 13 is a block diagram showing the configuration of a
display device according to a first embodiment of the present
invention, in which the display device may include a controller
600, a BLU driver 610, a panel driver 620, a backlight unit 200,
and a display panel 100. Further, in the configuration of the
display device shown in FIG. 13, the same parts as those described
with reference to FIGS. 1 to 12 are not described below.
[0185] Referring to FIG. 13, the display panel 100 can display an
image at 60, 120, or 240 frames per second, and the larger the
number of frames per second, the shorter the scan period T of the
frames.
[0186] The panel driver 620 generates driving signals for driving
the display panel in response to a variety of control signals and
image signals inputted from the controller 600, and transmits the
driving signals to the display panel 100. For example, the panel
driver 620 may include a gate driving unit connected with a gate
line of the display panel 100, a data driving unit (not shown), and
a timing controller (not shown) controlling those units.
[0187] Meanwhile, the controller 600 can output a local dimming
value to the BLU driver 610 according to the image signal to
control the backlight unit 200, in detail, the luminance of the
light sources in the backlight unit 200 in response to the image
signal.
[0188] Further, the controller 600 can supply information on the
scan period T displaying one frame on the display panel 100, for
example, a vertical synchronization signal Vsync to the driving
unit 610.
[0189] The BLU driver 610 can control the light sources in the
backlight unit 200 to emit light in accordance with the scan period
T in synchronization with display of an image on the display panel
100.
[0190] On the other hand, each of the light sources in the
backlight unit 200 may include a plurality of point light sources,
for example, LEDs (Light Emitting Diodes), and the point light
sources in one block can be simultaneously turned on or off.
[0191] Meanwhile, according to an embodiment of the present
invention, the light sources in the backlight unit 200 can be
divided into a plurality of blocks by the division driving method,
such as local dimming described above, and the luminance of the
light sources pertaining to each block can be adjusted in
accordance with the luminance of a region corresponding to each of
the divided blocks in the display panel 100, for example, the gray
level peak value or the color coordinate signal.
[0192] For example, when an image is displayed in a first region of
the display panel 100 and an image is not displayed in a second
region, that is, the second region is black, the BLU driver 610 can
control the backlight unit 200, in detail, the light sources in the
backlight unit 200 such that the light sources pertaining to the
blocks corresponding to the second region in the divided blocks
emit light at lower luminance than the light sources pertaining to
the blocks corresponding to the first region.
[0193] Meanwhile, the light sources pertaining to the blocks of the
backlight unit 200 which correspond to the second region that is
black without displaying an image in the display image of the
display panel 100 may be turned off, such that it is possible to
reduce power consumed by the display device.
[0194] That is, the controller 600 creates and outputs local
dimming values corresponding to the brightness of the blocks of the
backlight unit 200, that is, local dimming values for each block,
in accordance with the luminance level of the input image signal,
for example, the luminance level of the entire image or the
luminance level at a predetermined region, and the BLU driver 610
can control the brightness of the blocks in the backlight unit 200,
using the input local dimming values for each block.
[0195] A method of driving a display device according to an
embodiment of the present invention is described hereafter in
detail with reference to FIGS. 14 to 19.
[0196] FIG. 14 is a block diagram showing the configuration of a
display device according to a second embodiment of the present
invention, and the configuration of the display device shown in
FIG. 14, the same parts as those described with reference to FIGS.
1 to 13 are not described below.
[0197] Referring to FIG. 14, a display device according to an
embodiment of the present invention an image analyzing unit 601
that determines the luminance level for the entire of a portion of
an image in response to an RGB signal, a brightness determining
unit 602 that determines the brightness of a light source, for
example an LED, which corresponds to the luminance level determined
by the image analyzing unit 601, and a BLU driver 610 that drives
the backlight unit 200 in accordance with the brightness level
determined by the brightness determining unit 602.
[0198] Further, the display device may include a pixel compensator
603 that change the luminance level for the RGB image signal in
consideration of the luminance level of an image analyzed by the
image analyzing unit 601 and a panel driver 620 that outputs an
driving signal to the display panel 100 such that an image is
outputted in response to the R'G'B' signal compensated by the pixel
compensator 603.
[0199] The image analyzing unit 601 divides the region of the image
into several regions in response to the input RGB signal and
supplies information on the luminance level of an image to the
brightness determining unit 602 to determine the brightness of the
light sources pertaining to the blocks corresponding to the regions
in the backlight unit 200.
[0200] For example, the information on the luminance level of the
image supplied from the image analyzing unit 601 to the brightness
determining unit 602 may include not only the ABL (Average Block
Level), average luminance level of the region corresponding to a
block to determine its brightness, but of another region adjacent
to the above-mentioned region or the APL (Average Picture Level),
average luminance level of the entire region of the image.
[0201] In other words, the image analyzing unit 601 can divide the
image of one frame into a plurality of regions and supply
information on not only the average luminance level for a divided
first region, but the average luminance level for another region
adjacent to the first region, to the brightness determining unit
602. Further, when the brightness determining unit 602 determines
the brightness of a specific block in the backlight unit 200, the
image analyzing unit 601 can provide corresponding information to
allow the brightness determining unit 602 to use the average
luminance level of the entire image.
[0202] According to an embodiment of the present invention, it is
required to include a look-up table that determines the brightness
of a specific block in the backlight unit 200 in accordance with
the average luminance level of the entire or a portion of the
measured image, and the brightness determining unit 602 can read
out and output the brightness of a light source corresponding to
the average luminance level measured by the image analyzing unit
601 from the look-up table.
[0203] FIG. 15 is a graph showing a first embodiment of a method of
determining the brightness of a light source to the average
luminance level of an image, in which the x-axis represents the ABL
of a divided region of the display panel 210, the y-axis represents
the brightness of a block corresponding to the divided region in
the backlight unit 100, and the z-axis represents the APL of the
entire region.
[0204] Referring to FIG. 15, when the APL of the entire image is
less than `A`, the brightness of a corresponding block of the
backlight unit 200 is determined by a first graph 3A, when the APL
of the entire image is `A` or more and less than `B`, the
brightness of a corresponding block of the backlight unit 200 is
determined by a second graph 3B, and when the APL of the entire
image is `B` or more, the brightness of the block of the backlight
unit 200 is determined by a third graph 3C.
[0205] For example, when the APL of the entire image is a
predetermined `B` or more, since the entire image should be
displayed bright, the brightness of the corresponding block of the
backlight unit 200 can be determined by the third graph 3C. In this
case, since the entire image to display on the image panel 100 is
bright, it does not matter that the image darkens with the local
dimming effect of the backlight unit 200 maximized.
[0206] In other words, when the entire image should be displayed
bright, the larger the average luminance level measured for each
divided region of the image, the higher the brightness of
corresponding blocks, whereas the smaller the average luminance of
the divided regions, the lower the brightness of the corresponding
blocks. For reference, the figure shows that the graph representing
the brightness of the LED to the average luminance level at each
divided region has one inclination.
[0207] On the other hand, when the entire image should be displayed
dark, that is, the APL of the entire image is less than `A`, the
local dimming can be applied only to the divided regions having
average luminance level smaller than a predetermined luminance.
[0208] That is, the proposed look-up table makes it possible to
apply the local dimming that changes the brightness of the light
sources only for the divided region having average luminance level
smaller than the predetermined luminance. This is because when the
entire image is dark and the brightness of the light source is
determined by the local dimming graph, such as the third graph 3C,
the image becomes too dark and the color reproduction is
deteriorated.
[0209] Therefore, when the luminance level of the entire image is
low, the local dimming is not applied to the divided regions having
average luminance level above a predetermined brightness.
[0210] Further, when the APL of the entire image is in between `A`
and `B` and the average luminance level of a measured divided
region is larger than a predetermined value, it is required to
decrease changes in brightness of the light source, and when the
average luminance level of the divided region is smaller than the
predetermined value, it is required to increase changes in
brightness of the light source. That is, it is possible to set a
small local dimming value corresponding to the light source in
bright divided regions, and set a relatively large local dimming
value corresponding to the light source in less bright divided
regions than the above divided regions.
[0211] The graph showing the brightness of a light source to
average luminance levels according to the look-up table is stored
when the APL of the entire image is the maximum MAX and the APL of
the entire image is the minimum MIN, and the table corresponding to
the APL of the entire image to measure may be determined between
the maximum and minimum graphs of the APL of the entire image.
[0212] FIG. 16 shows by way of an example that a graph 4C that is
applied when the APL of the entire image is the maximum MAX and a
graph 4A that is applied when the APL is the minimum MIN. That is,
when the APL of the entire image is at the maximum, the brightness
of the image is the maximum, and accordingly, even if the local
dimming is applied to the divided regions, the color reproduction
is not deteriorated and a large amount of power consumed by the
backlight unit 200 can be reduced.
[0213] Further, when the APL of the entire image is at the minimum,
the brightness of the image is the minimum; therefore, in this
case, the color reproduction of the image is deteriorated if the
local dimming is applied to the entire image. Accordingly, in this
case, it is possible to prevent the color reproduction from largely
decreasing and reduce the power consumed in driving the backlight
unit, by applying the local dimming to the divided region
corresponding to when the ABL of the divided region is smaller than
a predetermined value 4AA.
[0214] Further, when the APL of the entire image is not the maximum
or the minimum, it is possible to create a desired look-up table
(graph) by interpolating the graphs 4A and 4C. That is, brightness
determining unit 602 can create a new graph positioned within a
region defined by the graphs 4A and 4C, using the look-up tables
when the APL of the entire image is the maximum and the
minimum.
[0215] According to another embodiment of the present invention,
the image signal transmitted to the display panel 100, for example,
the RGB signal can be compensated.
[0216] In other words, when the local dimming is applied to the
backlight unit 200 described above, there may be regions (or
pixels) to display colors in the divided regions of the display
panel 100. In this case, it is possible to reduce incomplete
reproduction of colors due to the local dimming by adding a gain
according to the luminance level of the entire image to the RGB
signal transmitted to the panel driver 620.
[0217] For example, when the local dimming is applied to a specific
region in the image, since the ABL of the corresponding divided
region is low, there may be characters or images that should be
displayed in the divided region, even if the degree of the local
dimming is large. That is, when the entire APL is low, high local
dimming is applied and the entire image is displayed dark;
therefore, even the characters or images to display may be
displayed dark.
[0218] In this case, it is possible to implement color reproduction
for the characters or images by improving the luminance level of
the RGB signal transmitted to the display panel 210 while
maintaining the reduction effect of the power consumed by the local
dimming.
[0219] The pixel compensator 603 can compensate the image signal by
multiplying the luminance level of the input RGB signal by a
compensation value a, and for example, can estimate the
compensation value a, using the APL of the entire image measured by
the image analyzing unit 601.
[0220] FIG. 17 is a graph showing an embodiment of a method of
determining a compensating value a of an image signal to the
average luminance level of an image.
[0221] Referring to FIG. 17, relatively large compensation can be
performed when the image is dark, and the saturation frequency of
the RGB value can be reduced by decreasing the compensation value a
when the image is bright, such that more natural compensation can
be performed to the pixel.
[0222] The x-axis represents the APL of the entire image measured
by the image analyzing unit 601 and the y-axis represents a
compensation value a for compensating the pixel of the RGB signal
corresponding thereto, in the graph shown in FIG. 17.
[0223] That is, when the local dimming is not applied or the local
dimming value is a predetermined reference value, for example, 5 A
or less, the compensation value a for compensating the pixel is set
to 1, and as the local dimming value becomes closer to the maximum
value MAX, the compensation value a can be increased above 1.
Therefore, the pixel can be compensated as much as the darkening of
the substantially shown images of the characters or images by the
local dimming.
[0224] Meanwhile, the compensated characters or images may imply
regions where the gain of the RGB image signal is above a
predetermined value.
[0225] According to another embodiment of the present invention,
the controller 600 may further include a filtering unit (not shown)
correcting the brightness level determined by the brightness
determining unit 602, for example, in order to the brightness of
the LED from rapidly changing with respect to time.
[0226] FIG. 18 is a view showing the configuration of a BLU driver
included in a display device, in which, in the operation of the BLU
610, the same parts as those described with reference to FIGS. 13
to 17 are not described below.
[0227] Referring to FIG. 18, the BLU driver 610 is inputted from
local dimming values for each block representing the brightness of
the divided blocks of the backlight unit 200 from the controller
600, in detail, the brightness determining unit 602 of the
controller 600, and can output a plurality of driving signals, for
example first to m-th driving signals, using the input local
dimming values for each block.
[0228] Meanwhile, each of the driving signals outputted from the
BLU driver 610 can control the brightness of two or more blocks of
the divided blocks in the backlight unit 200.
[0229] In other words, the BLU driver 610 can create a first
driving signal for controlling the brightness of n blocks, for
example, the first to n-th blocks in the blocks of the backlight
unit 200 and supply the first driving signal to the light sources
pertaining to the first to n-th blocks, and for this configuration,
it is possible to create the first driving signal, using the local
dimming values corresponding to the first to n-th blocks in the
local dimming values for each block inputted from the controller
600.
[0230] According to an embodiment of the present invention, the
controller 600 and the BLU driver 610 can communicate signals with
each other, using SPI (Serial Peripheral Interface) communication,
that is, the BLU driver 610 can receive local dimming values for
each block from the controller 600, using the SPI
communication.
[0231] Referring to FIG. 19, the BLU driver 610 may include a
plurality of driving units 611 and 615, and the driving units 611
and 615 may include MCUs 612 and 616 and a plurality of drivers IC
613 and 617, respectively.
[0232] For example, the first driving unit 611 includes an MCU 612
and a plurality of driver ICs 613, and the MCU 612 can receive in
series local dimming values for each block from the controller 600,
in detail the brightness determining unit 602 of the controller
600, and then output them in parallel and transmit local dimming
values of corresponding blocks to the driver ICs 613.
[0233] Meanwhile, the driver ICs 613 can control the brightness of
n blocks of the divided block in the backlight unit 200, and for
this configuration, it is possible to output driving signals for
controlling the brightness of the n blocks, using n channels.
[0234] For example, the first driving unit 611 may include four
driver ICs 613 and each of the four driver ICs 613 can control the
brightness of the light sources pertaining to sixty blocks by
outputting driving signals, using sixty channels. Accordingly, the
first driving unit 611 can control the brightness of 4.times.16
blocks, i.e. sixty four blocks in the divided blocks of the
backlight unit 200.
[0235] For example, the second driving unit 615 includes an MCU 616
and a plurality of driver ICs 613, and the MCU 616 can receive in
series local dimming values for each block from the controller 600,
in detail the brightness determining unit 602 of the controller
600, and then output them in parallel and transmit local dimming
values of corresponding blocks to the driver ICs 617.
[0236] Meanwhile, the driver ICs 617 can control the brightness of
n blocks of the divided block in the backlight unit 200, and for
this configuration, it is possible to output driving signals for
controlling the brightness of the n blocks, using n channels.
[0237] The configuration of the BLU driver 610 shown in FIG. 19 is
nothing but an embodiment of the present invention; therefore, a
display device according to the present invention is not limited to
the configuration shown in FIG. 19. That is, the BLU driver 610 may
include three or more driving units, and the number of blocks of
the backlight unit 200 of which the brightness is controlled by the
driving units can be changed.
[0238] Although the present invention was described in the above
with reference to the preferred embodiments, the embodiment are
provided just as examples and do not limit the present invention.
Further, the present invention may be modified and applied in
various ways not exemplified in the above within the spirit and
scope of the present invention by those skilled in the art. For
example, the components described in detail in the embodiments of
the present invention may be modified. Further, differences in the
modification and application should be construed as being included
in the scope of the present invention, which is defined in the
accompanying claims.
* * * * *