U.S. patent application number 16/750830 was filed with the patent office on 2021-07-29 for multi-panel liquid crystal display device and method for displaying image therein.
The applicant listed for this patent is Panasonic Liquid Crystal Display Co., Ltd., Pasona Knowledge Partner Inc.. Invention is credited to Tatsuo ITOMAN, Katsuhiro KIKUCHI, Hideyuki NAKANISHI, Takenobu NISHIGUCHI.
Application Number | 20210233480 16/750830 |
Document ID | / |
Family ID | 1000005705620 |
Filed Date | 2021-07-29 |
United States Patent
Application |
20210233480 |
Kind Code |
A1 |
NAKANISHI; Hideyuki ; et
al. |
July 29, 2021 |
MULTI-PANEL LIQUID CRYSTAL DISPLAY DEVICE AND METHOD FOR DISPLAYING
IMAGE THEREIN
Abstract
A liquid crystal (LC) display device includes a first display
panel, a second display panel, and an image processor. The image
processor generates first image data and second image data that
correspond to a first image and a second image for display on the
first display panel and the second display panel, respectively. The
image processor includes a first image data decision unit that
decides the first image data, a filter that decides a correction
factor, and a second image data decision unit that decides the
second image data based on smoothed image data and the correction
factor. A method for displaying an image in a LC display device
with a first display panel and a second display panel includes
determining first image data based on smoothed input image data,
and determining second image data based on the smoothed input image
data and a correction factor.
Inventors: |
NAKANISHI; Hideyuki; (Osaka,
JP) ; KIKUCHI; Katsuhiro; (Osaka, JP) ;
NISHIGUCHI; Takenobu; (Nara, JP) ; ITOMAN;
Tatsuo; (Osaka, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Panasonic Liquid Crystal Display Co., Ltd.
Pasona Knowledge Partner Inc. |
Himeji-shi
Osaka |
|
JP
JP |
|
|
Family ID: |
1000005705620 |
Appl. No.: |
16/750830 |
Filed: |
January 23, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G06T 5/50 20130101; G09G
3/3607 20130101; G09G 2360/12 20130101; G09G 2340/16 20130101; G09G
2320/0271 20130101; G09G 2300/023 20130101; G06T 5/002 20130101;
G09G 2320/0252 20130101; G06T 5/20 20130101 |
International
Class: |
G09G 3/36 20060101
G09G003/36; G06T 5/00 20060101 G06T005/00; G06T 5/50 20060101
G06T005/50; G06T 5/20 20060101 G06T005/20 |
Claims
1. A liquid crystal display device, comprising: a first display
panel that displays a first image; a second display panel that
displays a second image and that is opposed to the first display
panel; and an image processor that generates first image data
corresponding to the first image and second image data
corresponding to the second image based on an input image data,
wherein the image processor includes: a smoothing processor that
performs smoothing processing on the input image data; a first
image data decision unit operatively connected to the smoothing
processor and that decides the first image data based on the input
image data subjected to the smoothing processing; a filter
operatively connected to the first image data decision unit that
decides a correction factor for the second image data based on the
first image data; and a second image data decision unit operatively
connected to the smoothing processor and the filter, the second
image data decision unit decides the second image data based on the
input image data subjected to the smoothing processing and the
correction factor from the filter, wherein the first display panel
includes liquid crystal and the second display panel includes
liquid crystal, wherein response speeds of the first and second
display panels are based on the liquid crystal in each of the first
and second display panels, and wherein the response speed of the
second display panel is faster than the response speed of the first
display panel, and the image processor underdrives the second
display panel such that the liquid crystal in the second display
panel is operated to respond more slowly, or the response speed of
the second display panel is slower than the response speed of the
first display panel, and the image processor overdrives the second
display panel such that the liquid crystal in the second display
panel is operated to respond more quickly.
2. The liquid crystal display device according to claim 1, wherein
the filter compares the first image data in a current frame and the
first image data in a previous frame, or the first image data in a
current frame and a data calculated in the filter in a previous
frame, to decide the correction factor for the second image
data.
3. The liquid crystal display device according to claim 1, wherein
the filter includes a frame memory to store data calculated in the
filter.
4. The liquid crystal display device according to claim 1, wherein
the filter includes: a temporal filter that compares the first
image data in a current frame and the first image data in a
previous frame, or the first image data in a current frame and data
calculated in the filter in a previous frame, and generates a
grayscale of modified first image data; and a divider that
calculates a correction amount of the correction factor by dividing
the grayscale of the modified first image data by a grayscale of
the first image data.
5. The liquid crystal display device of claim 1, wherein the filter
utilizes values stored in a lookup table.
6. The liquid crystal display device of claim 1, wherein the filter
determines an output gradation value based on a relationship
between an input gradation value in a current frame and a corrected
gradation value in a previous frame.
7-8. (canceled)
9. A method for displaying an image in a liquid crystal display
device having first and second display panels, comprising:
receiving, by an image processor, input image data; smoothing, by a
smoothing processor, the input image data; determining, by a first
image data decision unit operatively connected to the smoothing
processor, first image data based on the smoothed input image data;
determining a correction factor, using a filter operatively
connected to the first image data decision unit, for second image
data based on the first image data; determining, by a second image
data decision unit operatively connected to the first image data
decision unit and the filter, the second image data based on the
smoothed input image data and the correction factor; and
generating, by the image processor, a first image displayable on
the first display panel and a second image displayable on the
second display panel using the first image data and the second
image data, wherein the first display panel includes a liquid
crystal and the second display panel includes a liquid crystal,
wherein response speeds of the first and second display panels are
based on the liquid crystal in each of the first and second display
panels, and wherein the response speed of the second display panel
is faster than the response speed of the first display panel, and
the image processor underdrives the second display panel such that
the liquid crystal in the second display panel is operated to
respond more slowly, or the response speed of the second display
panel is slower than the response speed of the first display panel,
and the image processor overdrives the second display panel such
that the liquid crystal in the second display panel is operated to
respond more quickly.
10. The method of claim 9, wherein the determining the correction
factor includes comparing the first image data in a current frame
and the first image data in a previous frame, or the first image
data in a current frame and a data calculated in the filter in a
previous frame, to decide the correction factor for the second
image data.
11. The method of claim 9, wherein the determining the correction
factor includes storing and retrieving image data in a frame
memory.
12. The method of claim 9, wherein the determining the correction
factor includes: comparing the first image data in a current frame
and the first image data in a previous frame, or the first image
data in a current frame and data calculated in the filter in a
previous frame, and generates a grayscale of modified first image
data; and dividing the grayscale of the modified first image data
by a grayscale of the first image data.
13. The method of claim 9, wherein the determining the correction
factor includes looking up values stored in a lookup table.
14. The method of claim 9, wherein the determining the correction
factor includes determining an output gradation value based on a
relationship between an input gradation value in a current frame
and a corrected gradation value in a previous frame.
15-16. (canceled)
Description
FIELD
[0001] This disclosure relates to liquid crystal display devices
that utilize two or more liquid crystal display panels.
BACKGROUND
[0002] A liquid crystal ("LC") display device display provides a
plurality of pixels that form the displayed image. A LC display
device can include multiple stacked LC display panels that form the
pixels in the displayed image. Each LC display panel includes
pixels that filter light. An LC display panel can provide filtered
light to another LC display panel that further filters the light
such that the desired image is formed. Each set of corresponding
pixels in the LC display panels filters light to form the pixels in
the displayed image with properties (e.g., color, brightness,
saturation) that match the desired image.
SUMMARY
[0003] A LC display device includes a first display panel, a second
display panel opposed to the first display panel, and an image
processor. The first display panel displays a first image and the
second display panel displays a second image. The image processor
generates first image data corresponding to the first image and
second image data corresponding to the second image based on an
input video data.
[0004] In an embodiment, the image processor includes a smoothing
processor, a first image data decision unit, a filter, and a second
image data decision unit. The smoothing processor performs
smoothing processing on input image data of the input video data.
The first image data decision unit is operatively connected to the
smoothing processor and decides the first image data based on the
image data subjected to the smoothing processing. The filter is
operatively connected to the first image data decision unit and
decides a correction factor for the second image data based on the
first image data. The second image data decision unit is
operatively connected to the smoothing processor and the filter.
The second image data decision unit decides the second image data
based on the image data subjected to the smoothing processing and
the correction factor from the filter
[0005] In an embodiment, a method for displaying an image in a LC
display device having first and second display panels includes
smoothing input image data of an input video data, determining
first image data based on the smoothed input image data,
determining a correction factor for second image data based on the
first image data. The method further includes determining the
second image data, and generating a first image displayable on the
first display panel and a second image displayable on the second
display panel using the first image data and the second image
data.
[0006] The first image data is based on the smoothed input image
data. The second image data is based on the smoothed input image
data and the correction factor. The method further includes
receiving the input video data.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] Both described and other features, aspects, and advantages
of a liquid crystal display device and a method of displaying an
image in a liquid crystal display device will be better understood
with the following drawings:
[0008] FIG. 1 is a schematic view of an embodiment of a liquid
crystal display device.
[0009] FIG. 2 is a schematic cross-sectional view of the first and
second display panels and the light source of FIG. 2, according to
an embodiment.
[0010] FIG. 3 is a schematic view of an image processor in the
liquid crystal display device of FIG. 1, according to an
embodiment.
[0011] FIG. 4 shows a graph of light filtering by a liquid crystal
display device in an embodiment.
[0012] FIG. 5 is a block diagram of a method of displaying an image
in a liquid crystal display device.
[0013] Like reference characters refer to similar features.
DETAILED DESCRIPTION
[0014] A LC display device can include at least a two LC display
panels. Each LC display panel includes liquid crystal and pixels
with pixel electrodes that manipulate portions of the liquid
crystal to control an amount of the light that is filtered by each
respective pixel. For example, the luminescence of a pixel in the
displayed image is a product of the filtering provided by a pixel
in the rear display panel ("pixel A") and the filtering provided by
a pixel in the front display panel ("pixel B"). In other words,
pixel A only allows a first percentage of the light passing through
pixel A to be emitted from the rear display panel, and the pixel B
only allows a second percentage of the filtered light reaching
pixel B to be emitted from the front display panel (e.g.,
luminescence.apprxeq.initial brightness(first percentage)(second
percentage)).
[0015] The response speed of the liquid crystal molecules in the
two LC display panels can be different. When the LC display is
directed to change its displayed image, it can take longer for the
slower LC display panel to reach its new filtering percentage than
for the faster LC display panel to reach its new filtering value.
For example, the faster LC panel may decrease its filtering faster
than the slower LC panel can increase its filtering for a pixel in
a displayed image. This can cause a temporary increase in the
overall luminescence of the displayed pixel until the filtering for
both panels reaches the new filtering values. It has been found
that even slight differences in the response times of the liquid
crystal in the two LC display panels can result in flickering
and/or luminance unevenness when the LC display changes images. For
example, response times may be different between panels due to
having different liquid crystal components (e.g., a negative type,
a positive type), and/or operating at different temperatures. The
panel(s) closer to the light source can operate at higher
temperatures due to the energy generated by the light source.
[0016] Embodiments disclosed herein are configured to
advantageously correct the image to be displayed by one display
panel based on the image to be displayed in a different display
panel. In an embodiment, the image correction accounts for and
helps minimize overall brightness differences caused by one of the
display panels having a faster response time.
[0017] FIG. 1 shows a schematic view of a LC display device 1. The
LC display device 1 is configured to display a desired image. The
LC display device 1 includes a first display panel 10, a second
display panel 30, a light source 50, and an image processor 100.
The first display panel 10 and the second display panel 30 are each
LC display panels. The first display panel 10, the second display
panel 30, and the light source 50 are in a stacked configuration in
the viewing direction (e.g., in negative Z direction).
[0018] The light source 50 provides light to the second display
panel 30. The second display panel 30 filters the light from the
light source 50 and provides the filtered light to the first
display panel 10. The first display panel 10 further filters the
filtered light from the second display panel 30. The light filtered
by the first display panel 10 and second display panel 30 shows the
desired image. The display panels 10, 30 are configured to filter
the light from the light source 50 to display a desired image.
Operation of the display panels 10, 30 is discussed in more detail
below.
[0019] In an embodiment, the light source 50 is backlight unit. The
light source 50 can include, for example, lamp(s), LED(s), light
guide plate, etc. for generating light. The light source 50 can
provide unfiltered light to the second display panel 30. In an
embodiment, the light source 50 can provide diffused light to the
second display panel 30.
[0020] Each of the display panels 10, 30 includes a display area
A.sub.1, A.sub.2 containing pixels P that are arranged in a matrix
with rows (e.g., in the X direction) and columns (e.g., in the Y
direction). Each pixel P includes a thin film transistor ("TFT")
and a pixel electrode 12, 32. Each display panel 10, 30 includes a
gate driver (i.e., data driver) 14, 34 and a source driver 16, 36
that individually electrically controls the pixel electrodes 12, 32
in their respective display panel via the TFTs. In each display
panel 10, 30, the pair of drivers 14/34, 16/36 controls the amount
of light filtered by each pixel P so that the display panels 10, 30
filter and display the correct image.
[0021] The desired image for the LC display device 1 to display may
be referred to as the input image. During operation, the image
processor 100 receives input image data D.sub.1. The input image
data D.sub.1 corresponds to the input image to be displayed by the
LC display device 1. The image processor 100 generates first image
data D.sub.1 and second image data D.sub.2 based on the input image
data D.sub.1. The first image data D.sub.1 is used to display a
first image on the first display panel 10, and the second image
data D.sub.2 is used to display a second image on the second
display panel 30. For example, the gate driver 34 and source driver
36 in the second display panel 30 (shown in FIG. 1) use the second
image data D.sub.2 to display the second image on the second
display panel 30. The light from the second display 30 is provided
to the first display 10 and is filtered by the first display 10 to
display the first image. The first image is configured to be the
input image in this embodiment.
[0022] In an embodiment, the first image data D.sub.1 includes
respective filtering values for the pixels P in the first display
panel 10 for displaying the first image. In an embodiment, the
second image data D.sub.2 includes filtering values for each pixel
P in the second display panel 30 to display the second image. For
example, a filtering value can be the amount of light to be
filtered by a pixel and/or a voltage for the corresponding pixel
electrode 12, 32 to provide the intended amount of light filtering.
The first image data D.sub.1 and second image data D.sub.2 are
provided to their respective display panels 10, 30. The drivers 14,
16, 34, 36 control the pixels P in the panels according to the
first and second image data D.sub.1, D.sub.2.
[0023] The pixels P in the second display panel 30 are controlled
to filter the light from the light source 50 and display the second
image. The pixels P in the first display panel 10 are controlled to
filter the light from the second display panel 30 and display the
first image. Light is filtered by the pixels P in the second
display panel 30 and the pixels P in the first display panel 10 to
display the desired image. The configuration of the image processor
100 is described in more detail below. In some embodiments, the
first display panel 10 is referred to as a main panel and the
second display panel 30 is referred to as a sub-panel.
[0024] The display panels 10, 30 are composed of a series of
layered components. FIG. 2 is a schematic cross-sectional view of
the display panels 10, 30 and the light source 50. The second
display panel 30 is opposed to the first display panel 10. The
second display panel 30 is located between first display panel 10
and the light source 50 in the thickness direction di of the LC
display device 1 (e.g., in Z direction in FIG. 1). Light (e.g.,
light L) emitted from light source 50 passes through and is
filtered by the second display panel 30 and then the first display
panel 10.
[0025] As shown in FIG. 2, each display panel 10, 30 includes a
layer of liquid crystal 18/38 sandwiched between a first substrate
20/40 and a second substrate 22/42. In each display panel 10, 30,
the liquid crystal layer 18, 38 and the pair of substrates 20/22,
40/42 are sandwiched by a pair of polarizers POL.sub.1, POL.sub.2.
The first substrates 20, 40 include the pixel electrodes 12/32 of
their respective display panel 10, 30. The charge of the pixel
electrodes 12, 32 controls how the portion of the liquid crystal
layer 18, 38 along said pixel electrode 12, 32 changes the
orientation of the light passing therethrough. Thus, the charge of
each pixel electrode 12, 32 can control how much light passes
through the second polarizer POL.sub.2 in each display panel 10,
30.
[0026] In an embodiment, the second substrate 22 in the first
display panel 10 can include filters 24. A filter 24 can be a
specific color (e.g., green, red, blue, yellow, white, etc.). Each
filter 24 has a corresponding pixel electrode 12 that controls the
amount of its light that passes through the second polarizer
POL.sub.2. In an embodiment, the second substrate 22 in the first
display panel 10 is a color substrate with colored filters 24. In
an embodiment, the color filters 24 are arranged in repeating sets
of colors (e.g., repeating sets of three colors, repeating sets of
four colors, etc.) and the light passing through the color filters
24 (e.g., the light L) in each are configured to mix and form a
single pixel of light with a desired color. In an embodiment, the
second substrates 22, 42 include black matrix (not shown) to
prevent light from mixing between pixels within the second
substrates 22, 42. In some embodiments, the LC display device 1 is
a monochrome display and does not include the filters 22.
[0027] The pixels in the second display panel 30 provide light for
three of the pixels in the first display panel 10. The display area
A.sub.1 of first display panel 10 has triple the pixel density of
the display area A.sub.2 of the second display panel 30. It should
be appreciated that the pixels in the second display panel 30 may
be configured to provide light to a different number of pixels than
three. For example, the pixels in the second display panel 30 in an
embodiment may be configured to each provide light to one pixel in
the first display panel 10. In such an embodiment, the display area
A.sub.1 of first display panel 10 and the display area A.sub.2 of
the second display panel 30 have at or about the same pixel
density.
[0028] The display panels 10, 30 and the light source 50 are shown
in FIG. 2 as spaced apart. However, it should be appreciated that
panels 10, 30 and light source 50 are attached to each other in
various embodiments. In an embodiment, the display panels 10, 30
can be supported and/or mounted in a common frame structure. It
should be understood the that display panels 10, 30 in an
embodiment may include additional components beyond those shown,
such as for example, optical film(s) (brightness enhancement film,
light distributing film, etc.), protection film(s), adhesive(s),
etc.
[0029] In an embodiment, the second display panel 30 can provide
non-colored filtering, i.e., contrast filtering, while the first
display panel 10 provides color filtering. The second display panel
30 can advantageously provide higher contrasts than can be achieved
by the first display panel 10 by itself.
[0030] FIG. 3 is a schematic view of an embodiment of the image
processor 100 of the LC display device 1. The image processor 100
receives the input image data D.sub.1 and generates the first image
data D.sub.1 and the second image data D.sub.2 based on the input
image data D.sub.1. The first image data D.sub.1 corresponds to the
first image to be displayed by the first display panel 10 (shown in
FIGS. 1 and 2). The second image data D.sub.2 corresponds to the
second image to be displayed by the second display panel 30 (shown
in FIGS. 1 and 2).
[0031] As shown in FIG. 3, the image processor 100 includes a
smoothing processor 110, a first image data decision unit 130, a
second image processing unit 140, and a filter 150. In an
embodiment, the image processor 100 has an input terminal 102 for
the signal for the input image data D.sub.1 and output terminals
104, 106 for the signals for the first and second image data
D.sub.1, D.sub.2, respectively. In such an embodiment, the first
image data decision unit 130 and the smoothing processor 110 are
electrically connected to the input terminal 102, the first image
data decision unit 130 can be electrically connected to the output
terminal 104, and/or the second image data decision unit 140 can be
electrically connected to the other output terminal 106.
[0032] The smoothing processor 110 is configured to perform
smoothing processing on the input image data D.sub.1 to generate
smoothed input image data D.sub.3. The smoothing processor receives
the input image data D.sub.1 and generates the smoothed image data
D.sub.3. The smoothed image data D.sub.3 is the input data D.sub.1
subjected to the smoothing processing.
[0033] The smoothing processor 110 includes a max filter 112, a
grayscale inverter 114, and a balance filter 116. The max filter
112 performs max filtering on the input image data D.sub.1 to
generate max filtered image data D.sub.3-1. Max filtering is well
known in the field of image filtering and the max filter 112
employs max filtering. Max filtering is configured to help remove
noise from an image. The image data for a color image includes a
set of color values for each pixel. For example, the input image
data D.sub.1 includes an R value, a G value, and a B value for each
pixel in the input image. In an embodiment, max filtering sets the
maximum values for each of the color values in each pixel based on
the maximum value of the color values in its neighboring
pixels.
[0034] The grayscale inverter 114 performs grayscale inversion on
the max filtered image data D.sub.3-1 to generate grayscale image
data D.sub.3-2. The grayscale image data D.sub.3-2 corresponds to a
modified grayscale image of the input image. Grayscale inversion is
well known in the field of image filtering, and the grayscale
inverter 114 employs grayscale inversion. For example, the
grayscale inverter 114 may utilize a grayscale table for converting
the color values and/or the contrast value of each pixel to a
corresponding grayscale value. In an embodiment, the grayscale
inverter 114 may be configured to account for the gamma
characteristics of one or both of the display panels 10, 30.
[0035] The balance filter 116 performs mean filtering on the
grayscale image data D.sub.3-2 to generate the smoothed image data
D.sub.3. Mean filtering is known in the field of image filtering,
and the balance filter 116 employs mean filtering. Mean filtering
helps remove noise from the grayscale image. For example, mean
filtering adjusts grayscale values for neighboring pixels to remove
sudden value changes across neighboring pixels. In an embodiment,
mean filtering can be gaussian filtering that adjusts grayscale
values relative to nearby pixels so that change between neighboring
values does not exceed a normal distribution.
[0036] The max filter 112 and the balance filter 116 are examples
of smoothing filters. It should be appreciated that other
embodiments of the smoothing processor 110 may include different
smoothing filters than the max filter 112 and the balance filter
116. In an embodiment, the smoothing processor 110 may include the
grayscale inverter 114 and one or more smoothing filters. In an
embodiment, the timing at which the grayscale conversion occurs may
be different. For example, the smoothing processor 100 in an
embodiment may apply the grayscale conversion before, between, or
after applying the smoothing filter(s).
[0037] The first image data decision unit 130 is configured to
determine the first image data D.sub.1 for the first display panel
10 (shown in FIGS. 1 and 2). As shown in FIG. 3, the first image
data decision unit 130 receives the input image data D.sub.1 and
the smoothed image data D.sub.3 and generates the first image data
D.sub.1. The first image data decision unit 130 is operatively
connected to the smoothing processor 110. The first image data
decision unit 130 decides the first image data D.sub.1 based on the
input image data D.sub.1 and the smoothed image data D.sub.3.
[0038] The liquid crystal molecules in the liquid crystal layer 18
of the first display panel 10 (shown in FIG. 2) can have different
response time than the liquid crystal molecules of the liquid
crystal layer 38 of the second display panel 30 (shown in FIG. 2).
For example, the liquid crystal layer 38 of the second display
panel 30 in an embodiment has a faster response time than the
liquid crystal layer 18 in the first display panel 10. The response
speeds of the first and second display panels 10, 30 are based on
the liquid crystal in each of the first and second display panels
10, 30. As discussed above, this difference in response times can
cause an excessive increase in the luminosity of a pixel in the
displayed image, leading to flickering and/or luminance unevenness
in the display image.
[0039] Returning to FIG. 3, the filter 150 decides and generates a
correction factor CF for the second image data D.sub.2 based on the
first image data D.sub.1. As shown in FIG. 3, the filter 150
receives the first image data D.sub.1 decided by the first image
data decision unit 130. The filter 150 is operatively connected to
the first image data decision unit 130. The correction factor CF
adjusts how the liquid crystal 38 is driven to compensate for the
different response times of the liquid crystal 18, 38 in the first
and second display panels 10, 30. The configuration and operation
of the filter 150 is discussed in the more detail below.
[0040] The second image data decision unit 140 is configured to
determine the second image data D.sub.2 for the second display
panel 30 (shown in FIGS. 1 and 2). As shown in FIG. 3, the second
image data decision unit 140 receives the smoothed image data
D.sub.3 and the correction factor CF decided by the filter 150. The
second image data decision unit 140 is operatively connected to the
smoothing processor 110 and the filter 150.
[0041] The second image data decision unit 140 decides the second
image data D.sub.2 based on the smoothed image data D.sub.3 and the
correction factor CF. For example, the second image data decision
unit 140 may determine initial image data based on the smoothed
input image data D.sub.3 and then modify the initial image data
based on the correction factor CF. In another embodiment, the
determination of the second image data D.sub.2 simply incorporates
the correction factor CF such that the second image data decision
unit 140 uses the smoothed image data D.sub.3 and the correction
factor CF simultaneously to determine the second image data
D.sub.2.
[0042] The correction factor CF is configured to modify how
operation of the liquid crystal 38 in the second display device 30
to account for response time differences between the liquid crystal
18, 38 in the display panels 10, 30. In an embodiment, the
correction factor CF increases or decreases the values in the
smoothed image data D.sub.3 to compensate for the display panels
10, 30 having different response times.
[0043] In an embodiment, the liquid crystal 38 in the second
display panel 30 (shown in FIG. 2) has a faster response time than
the liquid crystal layer 18 in the first display panel 10 (shown in
FIG. 2). In such an embodiment, the filter 150 can act as an
underdrive with the correction factor CF decreasing a rate of
changing speeds between a current and a previous frames in the
generated second image data D.sub.2 so that the faster liquid
crystal layer 38 is operated to respond more slowly.
[0044] In another embodiment, the liquid crystal 38 in the second
display panel 30 has a slower response time than the liquid crystal
18 in the first display panel 10. In such an embodiment, the filter
150 can act as an overdrive by the correction factor CF increasing
a rate of changing speeds between a current and a previous frames
in the generated second image data D.sub.2 such that the slower
liquid crystal 38 is operated to respond more quickly.
[0045] The correction factor CF applies a correction rate to the
operation of the second display panel 30 to adjust for the
difference in response times of the liquid crystal 18, 38. The
correction factor CF is configured to affect how the second display
panel 30 reaches the second image. For example, the correction
factor CF might cause a faster second display panel 30 to respond
10% slower so as to provide the desired second image slower.
[0046] In an embodiment, the filter 150 includes a temporal filter
152, a divider 154, and a frame memory 156 for calculating the
correction factor CF. In some embodiments, the image processor 100
is formed of logic circuits and memory(s) without a processor. In
such embodiments, the temporal filter 152 and divider 154 are
formed by logic circuits. In other embodiments, the image processor
100 may include a processor. In such embodiments, the temporal
filter 152 may utilize the same processor as the first image data
decision unit 130 and/or the second image data decision unit
140.
[0047] The temporal filter 152 receives the first image data
D.sub.1 and generates a grayscale of modified image data D.sub.4.
The temporal filter 152 generates the modified image data D.sub.4
by comparing the first image data in a current frame (e.g., D.sub.1
at t.sub.n) with one of the first image data in a previous frame
(e.g., D.sub.1 at t.sub.n-1) or data calculated in the temporal
filter 152 in a previous frame. For example, the temporal filter
152 in an embodiment decides the modified image data D.sub.4 by
comparing the first image data in a current frame (e.g., D.sub.1 at
t.sub.n) and the first image data in a previous frame (e.g.,
D.sub.1 at t.sub.n-1). For example, the temporal filter 152 in an
embodiment decides the modified image data D.sub.4 by comparing the
first image data in a current frame (e.g., D.sub.1 at t.sub.n) and
data calculated in the temporal filter 152 in a previous frame.
[0048] The divider 154 receives the first image data D.sub.1 and
modified image data D.sub.4 and generates the correction factor CF.
The divider 154 calculates a correction amount for the correction
amount by dividing values in modified image data D.sub.4 by a
values in the first image data D.sub.1 (i.e., values in modified
image data D.sub.4/values in the first image data D.sub.1). In an
embodiment, the values are grayscale values.
[0049] The frame memory 156 stores data used and/or data calculated
by the temporal filter 152. The frame memory 156 is a
non-transitory memory. In an embodiment, the data stored in the
frame memory 156 includes values of modified image data D.sub.4
used in previous frame(s) (e.g., D.sub.4 at t.sub.n-1, D.sub.4 at
t.sub.n-2, etc.) and/or first image data in previous frame(s)
(e.g., D.sub.1 at t.sub.n-11, D.sub.4 at t.sub.n-2, etc.). In an
embodiment, the data stored in the frame memory 156 includes
calculation(s) by the temporal filter 152 for generating the
modified image data D.sub.4 in previous frame(s). The frame memory
156 provides image data D.sub.5 to the temporal filter 152 that is
the modified image data D.sub.4 used in a previous frame (e.g.,
D.sub.4 at t.sub.n-1, D.sub.4 at t.sub.n-2, etc.), first image data
in a previous frame (e.g., D.sub.1 at t.sub.n-1, D.sub.4 at
t.sub.n-2, etc.), and/or calculation data that was performed in the
temporal filter 152 in a previous frame.
[0050] The modified image data D.sub.4 consists of values ("output
gradation values"). The filter 150 determines an output gradation
value based on a relationship between an input gradation value
(e.g., a value in the first image data D.sub.1) in a current frame
and a corrected gradation value in a previous frame (e.g., a value
in the modified image data D.sub.4 in a previous frame). For
example, the corrected gradation values of the second image data
can be calculated in the temporal filter 152 based on first image
data D.sub.1 and the modified image data D.sub.4 in the previous
frame that is stored in the frame memory 156.
[0051] In an embodiment, an output gradation value (V.sub.ON.sup.n)
is determined for each pixel utilizing the following relationship
(1):
V.sub.ON.sup.n=(V.sub.ON.sup.n-V.sub.ON.sup.n-1)k+V.sub.on.sup.-1
(1)
[0052] V.sub.IN.sup.n=an input gradation value of the first image
data D.sub.1 in the current frame
[0053] V.sub.ON.sup.n-1=a corrected gradation value in the previous
frame
[0054] V.sub.ON.sup.n=a corrected gradation value in the current
frame
[0055] k=time constant
The time constant (k) is predetermined value based on the specific
relative response speeds of the two display panels 10, 30. For
example, the time constant (k) is greater than 1 (i.e., k>1) if
the first display panel 10 has a faster response speed than the
second display panel 30, and the time constant (k) is less than 1
(i.e., k<1) if the first display panel 10 has a slower response
speed then the second display panel 30.
[0056] In an embodiment, the filter 150 may utilizes a lookup table
instead of the above relationship to determine output gradation
values. For example, the lookup table may be stored in the frame
memory 156 or the filter 150 may include a separate memory for
storing the lookup table.
[0057] FIG. 4 shows a graph of an embodiment of the light filtering
for a pixel in the displayed image by the LC display device 1.
Solid line 205 is for filtering provided by a pixel in the second
display panel 30 without a correction factor CF. Dashed line 210 is
for filtering provided by the same pixel in the second display
panel 30 when the correction factor CF is being applied by the
filter 150. Solid line 215 corresponds to filtering provided by a
corresponding pixel in the first display panel 30. Solid line 220
corresponds to the luminescence of the corresponding pixel in the
displayed image with the correction factor CF being applied. Dashed
line 225 corresponds to the luminescence of the corresponding pixel
in the displayed image without the correction factor CF.
[0058] For demonstration purposes, relative luminance of the pixel
in the displayed image is configured to stay at 0.1 while the
filterings provided by the corresponding pixels in the first and
second display panels 10, 30 change. As shown in FIG. 4, the pixels
in the display panels 10, 30 begin the filtering change on frame n.
For example as shown by the dashed line 210, the second display
panel 30 take about two frame (i.e., at about frame n+2) to reach
its target value (0.33 in this example). For example as shown by
the solid line 215, the first display panel 30 takes about 5 frames
(i.e., at about frame n+5) to reach its target value (0.33 in this
example). As show by the dashed line 225, the luminescence of the
pixel in the displayed image deviates from the target value of 0.1
as the filtering changes in the display panels 10, 30, when the
corrective factor CF is not being used. This occurs because the
second display panel 30 has a faster response speed and therefore
decreases its filtering (shown by the dashed line 205) faster than
the first display panel 10 increases its filtering (shown by the
solid line 215).
[0059] As shown by the dashed line 210, the correction factor CF
decreases the rate at which the filtering by the pixel in the
second display panel 30 changes. The image processor 100 adjusts
the second image data D.sub.2 so that the pixel in the second
display panel 30 more slowly reaches its target value in about 4
frames. The image processor 100 underdrives the faster second
display panel 30. Accordingly, the luminescence of the pixel in the
displayed image (shown by the solid line 220) stays at 1.0 when the
correction factor CF is being applied to the second display panel
30.
[0060] FIG. 5 is block diagram of an embodiment of a method 300 of
displaying an image in a LC display device with at least two
display panels. In an embodiment, the method 300 may employed for
the LC display device 1 of FIGS. 1-3. The method 300 starts at
305.
[0061] At 305, an image processor in the LC display device (e.g.,
image processor 100) receives an input image data (e.g., input
image data D.sub.1). The method 300 then proceeds to 310.
[0062] At 310, a smoothing processor (e.g., smoothing processor
110) smooths the input image data. In an embodiment, the smoothing
310 includes performing grayscale inversion and one or more type of
image smoothing (e.g., max filtering, balance filtering, etc.). In
an embodiment, the smoothing processor includes a grayscale
inverter (e.g., grayscale inverter 114) for the grayscale inversion
and at least one type of smoothing filter (e.g., max filter 112,
balance filter 116). The method 300 then proceeds to 315.
[0063] At 315, a first image data decision unit (e.g., first image
data decision unit 130) determines first image data (e.g., first
image data D.sub.1) based on the smoothed input image data (e.g.,
smoothed input image data D.sub.3). The image data decision unit is
operatively connected to the smoothing processor. The method 300
then proceeds to 320.
[0064] At 320, a filter (e.g., filter 150) is used to determine a
correction factor (e.g., correction factor CF) for second image
data (D.sub.2) based on the first image data. The filter is
operatively connected to the first image data decision unit. In an
embodiment, determining the correction factor 320 includes storing
and retrieving image data in a frame memory (e.g., frame memory
156). In an embodiment, determining the correction factor 320
includes looking up values stored in a lookup table.
[0065] In an embodiment, determining the correction factor 320
includes comparing one of the first image data in a current frame
and the first image data in a previous frame, or the first image
data in a current frame and a data calculated in the filter in a
previous frame. In such an embodiment, the comparison may be used
to generate a grayscale of modified first image data (e.g.,
grayscale of modified first image data D.sub.4), and the
determining the correction factor 320 including dividing the
grayscale of the modified first image data by a grayscale of the
first image data.
[0066] In an embodiment, determining the correction factor 320
includes determining an output gradation value based on a
relationship between an input gradation value in a current frame
and a corrected gradation value in a previous frame.
[0067] At 325, a second image data decision unit (e.g., second
image data decision unit 140) determines the second image data
based on the smoothed input image data and the correction factor.
The second image data decision unit is operatively connected to the
first image data decision unit and the filter. The method 300 then
proceeds to 330.
[0068] At 330, the image processor generates a first image
displayable on the first display panel and a second image
displayable on the second display panel using the first image data
and the second image data.
[0069] In an embodiment, the method 300 may be modified to have
features as discussed herein. For example, the method 300 in an
embodiment may be modified based on display device 1 and/or the
image processor 100 as shown in FIGS. 1-3 and described above.
[0070] The examples disclosed in this application are to be
considered in all respects as illustrative and not limitative. The
scope of the invention is indicated by the appended claims rather
than by the foregoing description; and all changes which come
within the meaning and range of equivalency of the claims are
intended to be embraced therein.
* * * * *