U.S. patent application number 13/935473 was filed with the patent office on 2013-11-07 for organic electro luminescense display apparatus and application thereof.
The applicant listed for this patent is Sanyo Electric Co., Ltd.. Invention is credited to Hiroyuki GOYA, Masae ICHINO, Masutaka INOUE, Shigeo KINOSHITA, Yukio MORI, Haruhiko MURATA, Kazuo NAKAMOTO, Susumu TANASE, Yuichi TANEYA, Takashi YABUKAWA, Atsuhiro YAMASHITA.
Application Number | 20130293597 13/935473 |
Document ID | / |
Family ID | 27792357 |
Filed Date | 2013-11-07 |
United States Patent
Application |
20130293597 |
Kind Code |
A1 |
MORI; Yukio ; et
al. |
November 7, 2013 |
ORGANIC ELECTRO LUMINESCENSE DISPLAY APPARATUS AND APPLICATION
THEREOF
Abstract
A technology for reducing the so-called "phosphor burn-in"
phenomenon where the variation of luminance arises by reducing
display luminance of a certain pixel caused by deterioration in a
display apparatus constituted by an organic electro luminescence
element is provided. In the display apparatus, when displaying an
image acquired by an image acquiring unit, luminance substantially
same as average luminance of the acquired image is set to a
non-display area where the image is not displayed.
Inventors: |
MORI; Yukio; (Hirakata-city,
JP) ; TANASE; Susumu; (Kodama City, JP) ;
YAMASHITA; Atsuhiro; (Osaka, JP) ; INOUE;
Masutaka; (Neyagawa City, JP) ; KINOSHITA;
Shigeo; (Higashiosaka City, JP) ; MURATA;
Haruhiko; (Ibaraki City, JP) ; YABUKAWA; Takashi;
(Ibaraki City, JP) ; GOYA; Hiroyuki; (Kawanishi
City, JP) ; TANEYA; Yuichi; (Osaka City, JP) ;
ICHINO; Masae; (Osaka City, JP) ; NAKAMOTO;
Kazuo; (Higashiosaka City, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Sanyo Electric Co., Ltd. |
Osaka |
|
JP |
|
|
Family ID: |
27792357 |
Appl. No.: |
13/935473 |
Filed: |
July 3, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13463605 |
May 3, 2012 |
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13935473 |
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12265248 |
Nov 5, 2008 |
8194007 |
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13463605 |
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10933431 |
Sep 3, 2004 |
7561127 |
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12265248 |
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PCT/JP2003/002503 |
Mar 4, 2003 |
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10933431 |
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Current U.S.
Class: |
345/690 |
Current CPC
Class: |
H04M 1/0266 20130101;
G09G 3/007 20130101; G09G 2320/043 20130101; G09G 2310/027
20130101; G09G 2320/0626 20130101; G09G 3/3233 20130101; G09G 3/22
20130101; G09G 2360/16 20130101; G09G 2320/048 20130101; G09G
2300/0842 20130101; G09G 3/3275 20130101; G09G 2310/0232 20130101;
G09G 2360/144 20130101; G09G 2320/046 20130101 |
Class at
Publication: |
345/690 |
International
Class: |
G09G 3/32 20060101
G09G003/32 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 4, 2002 |
JP |
2002-057467 |
Mar 20, 2002 |
JP |
2002-079418 |
Mar 27, 2002 |
JP |
2002-089126 |
Mar 27, 2002 |
JP |
2002-089127 |
Mar 27, 2002 |
JP |
2002-089707 |
Mar 27, 2002 |
JP |
2002-090017 |
Claims
1-56. (canceled)
57. A method of displaying a picture at a predefined position on a
color organic EL display, the method comprising increasing or
decreasing the number of parts thereof being lighted according to a
situation, wherein all parts constituting the picture are lighted
when the situation is at best, the number of parts being lighted is
decreased as the situation grows worse, and the higher the
probability of lighting of a part, the lower the luminance of the
part set beforehand.
58. The method of displaying a picture according to claim 57,
wherein the display is a unit for receiving electric waves, the
situation is an intensity of received electric waves, and the
picture is an antenna picture showing the intensity of electric
waves that a communication unit should receive.
59. The method of displaying a picture according to claim 57,
wherein the display is a battery-driven unit, the situation is
residual quantity of a battery, and the picture is a battery
residual quantity picture showing the residual quantity of the
battery driving the unit.
60. The method of displaying a picture according to claim 57,
wherein the picture is an antenna picture including a plurality of
bars or a battery residual quantity picture including a plurality
of bars, and the luminance of a bar more likely to be lighted is
set to be lower than the luminance of a bar less likely to be
lighted.
61. The method of displaying a picture according to claim 60,
wherein all of the plurality of bars differ in length, and a longer
bar is designed to be displayed with less probability and with
higher luminance than a shorter bar.
62. The method of displaying a picture according to claim 57,
wherein different parts of a picture are displayed with different
luminance levels, and parts constituting a character are displayed
with identical luminance regardless of the probability of
display.
63. The method of displaying a picture according to claim 57,
wherein a position of the picture is fixed, and a position of a
character is movable.
64. A method of displaying a plurality of pictures on a color
organic EL display, wherein the picture is a symbol switched and
displayed according to a situation of a device in which the display
is installed such that the higher the probability of a picture
being displayed, the lower the luminance of the picture set
beforehand, and symbols showing the same situation are displayed
with the same luminance, and the plurality of pictures is at least
one of a picture showing a state during a telephone call, a battery
residual quantity picture, a picture showing a state where a key is
locked, a picture showing that a manner mode is entered, a picture
showing a reception of a mail, a picture showing that a Web search
is being conducted, an antenna picture, and a picture showing that
a character input mode is entered.
65. A self-luminous display unit having self-luminous elements,
wherein the display unit is configured to display, at a predefined
position on the display unit, a picture constituted of a plurality
of parts and showing a situation of the display unit according to
increase or decrease in the number of parts lighted, all parts
constituting the picture are lighted when the situation is at best,
and the number of parts being lighted is decreased as the situation
grows worse, and the higher the probability of lighting of a part,
the lower the luminance of the part set beforehand.
66. The display unit according to claim 65, wherein the display
unit is a unit for receiving electric waves, the situation is an
intensity of received electric waves, and the picture is an antenna
picture showing the intensity of electric waves that a
communication unit should receive.
67. The display unit according to claim 65, wherein the display
unit is a battery-driven unit, the situation is residual quantity
of a battery, and the picture is a battery residual quantity
picture showing the residual quantity of the battery driving the
unit.
68. The display unit according to claim 65, wherein the picture is
an antenna picture including a plurality of bars or a battery
residual quantity picture including a plurality of bars, and the
luminance of a bar more likely to be lighted is set to be lower
than the luminance of a bar less likely to be lighted.
69. The display unit according to claim 68, wherein all of the
plurality of bars differ in length, and a longer bar is designed to
be displayed with less probability and with higher luminance than a
shorter bar.
70. The display unit according to claim 65, wherein different parts
of a picture are displayed with different luminance levels, and
parts constituting a character are displayed with identical
luminance regardless of the probability of display.
71. The display unit according to claim 65, wherein a position of
the picture is fixed, and a position of a character is movable.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation application and claims
the priority benefit of Patent Cooperation Treaty Application
Number PCT/JP03/02503, filed on Mar. 4, 2003, which in turn claims
the priority benefits of Japanese Patent Application Number
JP2002-057467, filed on Mar. 4, 2002, Japanese Patent Application
Number JP2002-079418, filed on Mar. 20, 2002, Japanese Patent
Application Number JP2002-089126, filed on Mar. 27, 2003, Japanese
Patent Application Number JP2002-089127, filed on Mar. 27, 2003,
Japanese Patent Application Number JP2002-089707, filed on Mar. 27,
2003, and Japanese Patent Application Number JP2002-090017, filed
on Mar. 27, 2002.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a display method and a
display apparatus, and it particularly relates to a technology for
averaging degradations of each optical element in an active matrix
type organic electro-luminescence display apparatus and reducing
variation of luminance thereof.
[0004] 2. Description of the Related Art
[0005] Organic electro-luminescent displays (hereinafter, also
referred to as "organic EL displays" or "organic EL panels") are
attracting attention as new flat-type displays. In particular,
active matrix type organic EL displays having thin film transistors
(hereinafter, also referred to as "TFTs") as switching elements are
regarded as sweeping out the currently prevailing liquid crystal
displays in the near future, and are in a fierce development race
for practical use.
[0006] Unlike liquid crystal displays, organic EL displays have
self-luminous elements. This eliminates the need for a backlight
which is indispensable to liquid crystal displays, promising
apparatuses of yet lower profile and lighter weight. Moreover,
organic EL panels are expected for application as a light emitting
devices such as the backlight of liquid crystal displays using a
self-luminous characteristic.
[0007] It is known that, as for the organic EL element, degradation
progresses with luminescence and luminance thereof gradually
decreases. Development of the organic luminescent material which
does not deteriorate easily is important for providing the organic
EL panel with high display quality and long life, of course, but it
is unescapable that degradation with the passage of time arises for
the organic EL element. The first thing to do is development of the
technology for suppressing the influence of the degradation to the
minimum at a present stage.
SUMMARY OF THE INVENTION
[0008] The present invention has been made in view of the foregoing
circumstances and an object thereof is to provide a technology for
improving display quality of a display apparatus.
[0009] An embodiment of the present invention relates to a display
method. In this display method, when displaying an image on a
display area narrower than an area which can be displayed,
luminance data of a non-displaying area which does not display the
image among the area which can be displayed is set as a guessed
value of an average luminance of the image. "An area which can be
displayed" means a whole display screen in the display apparatus,
and "a display area" means an area where an image as an object of
display is actually displayed among the area which can be
displayed. "A non-displaying area" means an area other than the
display area among the area which can be displayed.
"Non-displaying" means that the image as an object of display is
not displayed, and does not necessarily mean that nothing is
displayed. The degradation speed of the display element which
constitutes each pixel can be averaged over the whole screen and
the variation in the display luminance resulting from the variation
in degradation speed can be reduced, by making the average
luminance of the image displayed on the display area and the
average luminance of the image displayed on the non-displaying area
become almost the same.
[0010] Another embodiment of the present invention relates to a
display apparatus. This display apparatus comprising: an
acquisition unit which acquires a first image to be displayed; a
first setting unit which sets a first area in which the first image
is displayed and places the first image on the first area; and a
second setting unit which sets, when the first area is smaller than
an area which can be displayed, a second image to be displayed on a
second area in which the first image is not displayed; wherein said
second setting unit sets the second image in a manner where a
guessed value of an average luminosity of the first image is
substantially same as a guessed value of an average luminosity of
the second image. The average luminance of a general image may be
guessed beforehand, and thus guessed average luminance may be made
become almost the same as the average luminance of the second
image. The luminance of more than 30% and less than 40%, or more
favorably more than 30% and less than 35%, for example, of the
maximum luminance may be adapted as the average luminance of the
general picture.
[0011] The second setting unit may calculate the average luminance
of the first image and may set the second image whose average
luminance is substantially same as calculated average luminance of
the first image to the second area. The degradation speed of the
display elements can be averaged with higher accuracy by selecting
the second image according to the average luminance of the first
image whenever the first image is displayed.
[0012] Further another embodiment of the present invention also
relates to a display apparatus. This display apparatus comprising:
an acquisition unit which acquires a first image to be displayed; a
first setting unit which sets a first area in which the first image
is displayed and places the first image on the first area; a second
setting unit which sets, when the first area is smaller than an
area which can be displayed, a second image to be displayed on a
second area in which the first image is not displayed; a first
storing unit which stores an accumulative average luminance of the
first image previously displayed on the first area; and a second
storing unit which stores an accumulative average luminance of the
second image previously displayed on the second area; wherein said
second setting unit sets the second image in a manner where the
accumulative average luminance of the second image approaches the
accumulative average luminance of the first image. Though the
average luminance of each first image differs from the average
luminance of each second image somewhat, it does not necessarily
lead to the variation in the display luminance immediately. These
average luminance should just become almost the same for long term.
The accumulative average luminance of the first images and second
images may be stored, and the second image may be adjusted to make
these accumulative average luminance values become almost the same
for long term. The variation in the display luminance can be
reduced by this method. According to this method, greater
flexibility of a display can be achieved. For example, the second
image can be selected based on the color or theme of the first
image.
[0013] The second image may be an image in which all pixels have
the almost same luminance data. That is, the second image may be an
image which consisted of only one color. In this specification, the
word an "image" is used, even if the image consists of only one
color.
[0014] Optional combinations of the aforementioned constituting
elements, and implementations of the invention in the form of
methods, apparatuses and systems may also be practiced as
additional modes of the present invention.
[0015] This summary of the invention does not necessarily describe
all necessary features so that the invention may also be a
sub-combination of these described features.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The object described above, other objects, characteristics
and advantages will be appreciated by referring to the preferred
embodiments and associated drawings.
[0017] FIG. 1 is a figure showing an internal structure of a mobile
terminal according to a first example of a first embodiment.
[0018] FIG. 2 is a figure showing a state where a display area is
set up in the center of an area of a display unit which can be
displayed, and an image is displayed.
[0019] FIG. 3 is a figure showing a state where average luminance
data of a general image is set up to a non-display area.
[0020] FIG. 4 is a figure showing a circuit structure of a single
pixel of the display unit.
[0021] FIG. 5 is a figure showing an internal structure of a mobile
terminal according to a third example of the first embodiment.
[0022] FIG. 6 is a figure showing an example of an internal data of
an accumulated average luminance storing unit.
[0023] FIG. 7 is a block diagram showing a structure of a cellular
phone according to a second embodiment.
[0024] FIGS. 8A and 8B are figures for explaining a black character
display mode and a white character display mode.
[0025] FIG. 9 is a flowchart showing an example of a procedure of
changing a mode.
[0026] FIG. 10 is a flowchart showing another example of a
procedure of changing a mode.
[0027] FIG. 11 is a figure showing a basic structure of an organic
EL display.
[0028] FIG. 12 is a circuit diagram of a single pixel of an active
matrix type organic EL display.
[0029] FIG. 13 is a block diagram showing a schematic structure of
a cellular phone.
[0030] FIGS. 14A, 14B, 14C, 14D, and 14E are schematic diagrams
showing five steps of a specific picture used for displaying
residual quantity of a battery.
[0031] FIG. 15 is a schematic diagram showing an example of initial
display in case where display luminance of a rightmost bar is set
up lowest, a leftmost bar highest, and a mean value of them is set
up as display luminance of a central bar, in the battery residual
quantity picture.
[0032] FIGS. 16A and 16B are graphs showing a change over time of
display luminance of a rightmost bar which has high probability to
light (solid line) and a change over time of display luminance of a
leftmost bar which has low probability to light (doted line).
[0033] FIGS. 17A, 17B, 17C, 17D, and 17E are schematic diagrams
showing five steps of a specific picture used for displaying
antenna picture.
[0034] FIG. 18 is a schematic diagram showing an example of initial
display in case where display luminance of a leftmost bar is set up
lowest, a rightmost bar highest, and a mean value of them is set up
as display luminance of a central bar, in the antenna picture.
[0035] FIGS. 19A, 19B, and 19C are schematic diagrams showing dots
constituting a first picture (bar) and dots constituting a second
picture (character of "charge") in the battery residual quantity
picture.
[0036] FIG. 20 is a schematic diagram showing pictures which can be
displayed on upper part of a color organic EL display.
[0037] FIG. 21 is a figure showing a basic structure of an organic
EL display apparatus.
[0038] FIG. 22 is a figure showing a state where a character is
shifted and displayed.
[0039] FIGS. 23A, 23B, and 23C are figures showing a method of
shifting an image and a change of dots constituting a pixel when
being shifted.
[0040] FIG. 24 is a figure showing a relation between a display
area and an effective display area.
[0041] FIG. 25 is a figure showing a display area of one font.
[0042] FIG. 26 is a structure diagram of an organic EL display
apparatus according to an embodiment.
[0043] FIGS. 27A, 27B, and 27C are figures showing a state where a
display image is scrolled.
[0044] FIGS. 28A and 28B are figures showing a state where mosaic
processing is carried out to a display image.
[0045] FIGS. 29A and 29B are figures showing a state where a
display color of a display image is changed at a fixed timing.
[0046] FIGS. 30A, 30B, and 30C are figures showing a state where
luminance ratio of RGB is gradually changed when changing a display
color of a display image.
[0047] FIG. 31 is a flowchart showing a procedure of changing a
display color to average grade of degradation of OLED.
[0048] FIG. 32 is a flowchart showing a procedure of performing
adjustment to a display image according to grade of degradation of
OLED.
[0049] FIG. 33 is a figure showing a display screen of a cellular
phone in which a display area is divided into three areas of up,
middle, and down.
[0050] FIG. 34 is a figure showing how a display image shifts.
[0051] FIG. 35 is a structure diagram of a cellular phone as an
organic EL display apparatus according to an embodiment.
[0052] FIG. 36 is a figure showing relation between a display image
which is displayed on an organic EL panel and is not scrolled, and
a memory space.
[0053] FIGS. 37A and 37B are figures showing a procedure of reading
image data by a timing control IC.
[0054] FIGS. 38A and 38B are figures showing a display screen in
which a phosphor burn-in is arisen.
[0055] FIGS. 39A and 39B are figures showing a display screen in
which a character string is displayed with two kinds of fonts
different from each other.
[0056] FIGS. 40A and 40B are figures showing a display screen in
which a character string is displayed with two size of font, large
and small.
[0057] FIG. 41 is a figure showing a state where a color of an area
where a character string is not displayed is gradually changed from
a background color to a display color of the character string.
[0058] FIGS. 42A and 42B are figures showing a state where a
character is shifted in a pixel area which forms one font.
[0059] FIG. 43 is a structure diagram of an organic EL display
apparatus according to an embodiment.
DETAILED DESCRIPTION OF THE INVENTION
[0060] The invention will now be described based on the preferred
embodiments. This does not intend to limit the scope of the present
invention, but exemplify the invention.
First Embodiment
[Example of the First Embodiment]
First Example
[0061] In the present embodiment, in order to average degradation
speed of display elements which constitute pixels of a display
apparatus on the whole screen, and to reduce variation in display
luminosity resulting from variation in degradation speed, when
displaying an image, an area where the image is not displayed is
displayed in a color of about 30% of white which is assumed as
average luminance of a general image.
[0062] FIG. 1 shows an internal structure of a mobile terminal 10,
as an example of a display apparatus of the present embodiment. The
mobile terminal 10 mainly comprises a communication unit 20, a
control unit 30, a memory unit 40, a display unit 100, an input
unit 50, a microphone 60, and a speaker 70. The communication unit
20 includes an antenna 22 which transmits and receives a signal, a
receiving unit 24 which decodes received signal, and a transmitting
unit 26 which modulates and transmits data. The communication unit
20 controls communication with other apparatus via a cellular phone
network. The display unit 100 displays text information, image
information and the like. In this embodiment, an organic EL panel
is used as the display unit 100. The display unit 100 may be an
inorganic EL panel or a liquid crystal panel and the like. The
technology of this embodiment is especially suitable for the
organic EL panel with which degradation of the display element
poses a problem. The input unit 50 receives input information from
outside via a keyboard, mouse, button, and the like. The microphone
60 inputs audio information from outside. The speaker 70 outputs
audio information to outside.
[0063] The control unit 30 controls of the mobile terminal 10 as a
whole and performs various processings required for a display. In
terms of hardware, this structure can be realized by a CPU, a
memory and other LSIs of an arbitrary computer. In terms of
software, it is realized by memory-loaded programs or the like
having a function of controlling display, but drawn and described
here are functional blocks that are realized in cooperation with
those. Thus, it is understood by the skilled in the art that these
functional blocks can be realized in a variety of forms by hardware
only, software only or the combination thereof.
[0064] The image acquiring unit 32 acquires an image to be
displayed from outside via the communication unit 20 or by reading
out the image stored in the memory unit 40. The display area
setting unit 34 sets an area to display the image inside an area
which can be displayed in the display unit 100 according to the
size of the acquired image. The non-display area setting unit 36
sets an image to be displayed on an area other than the display
area among the area which can be displayed, that is, a non-display
area in which the acquired image is not displayed. The display
control unit 38 places the image acquired by the image acquiring
unit 32 on the area set by the display area setting unit 34, and
sets the image set by the non-display area setting unit 36 to the
non-display area around the display area. The display control unit
38 thus generates the image data of the display screen and writes
it to the graphics memory 42. Then, the display control unit 38
outputs the image data and the driving signal to each pixel of the
display unit 100 at the predetermined timing.
[0065] FIG. 2 shows a state where the display area 104 is set up in
the center of the area 102 which can be displayed of the display
unit 100, and the image is displayed. In the example shown in FIG.
2, the display area 104 is set up in the center of the area 102
which can be displayed to display the image, and the non-display
area 106 is set around the display area 104, because the size of
the image is smaller than the area 102 which can be displayed. It
is favorable, considering a viewpoint of reduction of the power
consumption and reduction of the degradation of the organic EL
element constituting each pixel, that the luminance of the
non-display area 106 is set zero, that is, blackout. If an image is
displayed on the display area 104 for a long time, however, since
the time in which the pixel of the display area 104 is on becomes
long as compared with the pixel of the non-displaying area 106,
degradation of the organic EL element in the display area 104 will
progress earlier, and luminance will decrease. As a result thereof,
even if the whole screen is displayed with the same luminance data,
the luminance of the organic EL element near center of the screen
will become lower than the luminance of the organic EL element near
end of the screen, and a part near center of the screen will be
displayed darkly. Especially, when displaying the image of the same
size frequently, as a result of continuing displaying an image on
the same display area 104 for a long time, the pixel in the display
area 104 deteriorates earlier than surrounding pixels and the
luminance thereof decreases. Consequently, the so-called "phosphor
burn-in" phenomenon will happen in which the rectangle of the
display area 104 is seen when displaying an image on the whole
screen.
[0066] In this embodiment, to reduce generating such a phenomenon,
the non-display area setting unit 36 displays the non-display area
106 in color of about from 30% to 35% of white which is a guessed
average luminance level of the general image to make the organic EL
element in the non-display area 106 deteriorate to the same extent
as the organic EL element in the display area 104. Thereby, the
degradation speed of the organic EL element in a whole screen can
be averaged and the variation in the luminance and the phosphor
burn-in phenomenon can be reduced. By reducing the variation in the
luminance and phosphor burn-in, it contributes also to an
improvement of the life of the display unit 100.
[0067] FIG. 3 shows a state where an image having average luminance
of a general image is set up to a non-display area. In this
example, the image constituted by one color of about 30% of white
is set up to the non-display area 106. However, the image which has
arbitrary colors and patterns may be set as long as the average
luminance thereof is about 30% of white. In the case where the
patterned image is displayed on the non-display area 106, two or
more images whose average luminance is about 30% of white should be
prepared. The image should be replaced suitably and displayed to
prevent the phosphor burn-in of the image.
[0068] FIG. 4 shows a circuit structure of a single pixel of the
display unit 100. This circuit comprises an organic light emitting
element OLED, two transistors Tr1 and Tr2 for controlling the
organic light emitting element OLED, a capacitor C, a scan line SL
which transmits a scan signal, a data line DL which transmits a
luminance data, and a power supply line Vdd which supplies current
to the organic light emitting element.
[0069] The power supply line Vdd supplies an electric current for
making the organic light emitting element OLED emit. The data line
DL transmits luminance data for controlling luminance of each of
the organic light emitting elements OLED. The scanning line SL
transmits scan signals for controlling the emitting timing of each
of the organic light emitting elements OLED. The luminance data and
the scan signal are supplied by the display control unit 38.
[0070] A gate electrode of a first transistor Tr1 (hereinafter also
referred to as "switching transistor") is connected to the scanning
line SL. A drain electrode (or a source electrode) of the switching
transistor Tr1 is connected to the data line DL. A source electrode
(or a drain electrode) of the switching transistor Tr1 is connected
to a gate electrode of a second transistor Tr2 (hereinafter also
referred to as "driving transistor"). In this embodiment, the
switching transistor is a double-gate transistor having two gate
electrodes. In another embodiment, the switching transistor may be
a single-gate transistor or a multi-gate transistor having three or
more gate electrodes. The switching transistor Tr1 may be an
n-channel transistor or a p-channel transistor.
[0071] A source electrode (or a drain electrode) of the driving
transistor Tr2 is connected to an anode of the organic light
emitting element OLED. A drain electrode (or a source electrode) of
the driving transistor Tr2 is connected to the power supply line
Vdd. Similar to the switching transistor Tr1, the driving
transistor Tr2 may be a single-gate transistor or a multi-gate
transistor, and may be an re-channel transistor or a p-channel
transistor.
[0072] An anode of the organic light emitting element OLED is
connected to the source electrode (or the drain electrode) of the
driving transistor Tr2. A cathode of the organic light emitting
element OLED is connected to ground potential. An electrode of the
capacitor C is connected to the drain electrode (or the source
electrode) of the switching transistor Tr1 and the gate electrode
of the driving transistor Tr2. Another electrode of the capacitor C
is connected to ground potential via a wire not shown in figures,
or may be connected to the power supply line Vdd.
[0073] An operation of the circuit structured as described above is
explained hereinbelow. As the scan signal of the scanning line SL
goes high for writing the luminance data to the organic light
emitting element OLED, the switching transistor Tr1 turns on, the
luminance data which is being inputted to the data line DL is set
in the driving transistor Tr2 and the capacitor C. A current which
corresponds to the luminance data thus flows between the source
electrode and the drain electrode of the driving transistor Tr2,
and this current flows in the organic light emitting element OLED,
so that the organic light emitting element OLED emits. When the
scan signal of the scanning line SL becomes low, the switching
transistor Tr1 turns off, but the gate voltage of the driving
transistor Tr2 is maintained, so that the organic light emitting
element OLED continues emitting according to the set luminance
data.
[0074] At the next emitting timing, the scan signal of the scanning
line SL becomes high again, the switching transistor Tr1 turns on,
then the new luminance data which is inputted to the data line DL
is set in the driving transistor Tr2 and the capacitor C. Thereby,
the organic light emitting element OLED emits corresponding to the
new luminance data.
Second Example
[0075] In this example, when the mobile terminal acquires the image
to be displayed, the mobile terminal calculates average luminance
of the image and selects an image to be displayed on the
non-display area based on the average luminance. The internal
structure of the mobile terminal according to this example is
similar to the first example shown in FIG. 1. Hereinafter, a
structure differing from that in the first embodiment will be
mainly described.
[0076] The non-display area setting unit 36 calculates the average
luminance of the image acquired by the image acquiring unit 32. The
average luminance may be calculated for every signal of R, G, and
B. The non-display area setting unit 36 may calculate the average
luminance of luminance signal Y. The non-display area setting unit
36 displays an image whose average luminance is substantially the
same as the calculated average luminance. The image may be an image
may be covered with the average luminosity value or an image with
pattern which is prepared in the memory unit 40 beforehand. In the
case of the patterned image, the phosphor burn-in of the image can
be prevented by replacing two or more images suitably and
displaying.
Third Example
[0077] In this example, an accumulated average luminance of images
displayed on the display area and an accumulated average luminance
of images displayed on the non-display area are stored, and the
mobile terminal adjusts the images so that these accumulated
average luminance values become almost the same for a long
term.
[0078] FIG. 5 shows an internal structure of the mobile terminal 10
according to the third example. The mobile terminal 10 of the
present example further comprises an accumulated average luminance
storing unit 44 in addition to the structure of the mobile terminal
10 of the first example shown in FIG. 1. Hereinafter, a structure
differing from that in the first embodiment will be mainly
described.
[0079] When the image acquiring unit 32 acquires an image to be
displayed, the non-display area setting unit 36 calculates the
average luminance of the image. The non-display area setting unit
36 reads out the accumulated average luminance of the display area
and the accumulated average luminance of the non-display area for
the display area from the accumulated average luminance storing
unit 44 according to the size of the image. The non-display area
setting unit 36 selects an image to be displayed on the non-display
area so that these accumulated average luminance values can
approach. For example, when the accumulated average luminance of
the display area is lower than the accumulated average luminance of
the non-display area, the image whose average luminance is higher
than the average luminance of the image to be displayed this time
is set as the non-display area. Thereby, the average luminance of
the display area and the non-display area can be averaged in a long
term. The non-display area setting unit 36 re-calculates the
accumulated average luminance using the average luminance of the
image displayed this time and the average luminance of the image
displayed on the non-display area, and stores thus calculated
accumulated average luminance in the accumulated average luminance
storing unit 44. When a display image is a still image, the
accumulated average luminance may be calculated in consideration of
display time.
[0080] FIG. 6 shows an internal data of the accumulated average
luminance storing unit 44. In the accumulated average luminance
storing unit 44, an area ID column 110, a display area size column
112, a display area accumulated average luminance column 114, and a
non-display area accumulated average luminance column 116. For
example, when the size of the image acquired by the image acquiring
unit 32 is 100 dots by 100 dots, the information of the record of
area ID "1" is read by the non-display area setting part 36. Since
the accumulated average luminance of the display area of area ID
"1" is "70.5" and the accumulated average luminance of the
non-display area is "70.3", the average luminance of the
non-display area should just set up higher than the average
luminance of the display area in this time. The non-display area
setting unit 36 may adjust so that the accumulated average
luminance of the display area and the non-display area may become
equal by one display. The non-display area setting unit 36 may
adjust so that the accumulated average luminance of the display
area and the non-display area may become gradually equal by two or
more displays.
[0081] The flexibility of the image set as the non-display area
spreads according to this method. For example, when displaying a
photograph and the like, a frame may be displayed around the
photograph. Surrounding image can be selected according to the kind
or color of the image displayed or taste of a user. When displaying
an animation on the display area, if the average luminance of a
surrounding image is changed according to change of the average
luminance of the animation, there is a possibility that the screen
becomes hard to see. In this case, the image displayed on the
non-display area may be fixed with the image set up first, and the
accumulated average luminance of the display area and the
non-display area may be calculated and stored when the display of
the animation is completed. In the next display, the accumulated
average luminance should just be adjusted so that they can
approach.
[0082] Above-mentioned embodiments are only exemplary. It is
understood by those skilled in the art that there exist other
various modifications to the combination of each component and
process described above and that such modifications are encompassed
by the scope of the present invention.
[0083] In this embodiment, explanation is made taking the case of
the mobile terminal as the display apparatus. The technology of the
present invention is not limited in this, however, and can also be
applied to the arbitrary display apparatus like the television, the
display of the computer.
[Effect of the First Embodiment]
[0084] The variation in luminance of a display apparatus can be
reduced and display quality can be improved according to this
embodiment.
Second Embodiment
[Field of the Second Embodiment]
[0085] The present embodiment relates to a mobile terminal
comprising an organic EL (Electro Luminescence) display
apparatus.
[Related Art of the Second Embodiment]
[0086] In recent years, development of an organic EL display is
progressing. For example, adopting the organic EL display as a
display of a cellular phone is in the air.
[0087] As shown in FIG. 11, an organic layer 213 is formed on a
glass substrate 211 by arranging an organic hole transport layer
215 and an organic electron transport layer 216 on both sides of
the organic luminescence layer 214. An organic EL panel is formed
by arranging an anode 212 and a cathode 217 on both sides of the
organic layer 213. The organic luminescence layer 214 emits light
by applying a predetermined voltage between the anode 212 and the
cathode 217.
[0088] The anode 212 is made with transparent ITO (Indium Tin
Oxide). The cathode 217 is made with Al--Li alloy for example. They
are formed stripe type and arranged in the direction which crosses
mutually configuring a matrix.
[0089] The anode 212 is used for a data electrode, and the cathode
217 is used for a scanning electrode, for example. In the state
where one scanning electrode placed horizontally is selected, a
voltage according to an input data is applied to each data
electrode placed perpendicularly. Then the organic layer 213 emits
light at the intersection of these electrodes and one line is
displayed. The scanning electrode is scanned by switching
perpendicularly one by one, and one field is displayed.
[0090] An active matrix type driving mode is known as the driving
mode of the organic EL display, in which luminescence of each pixel
is continued over one vertical scanning term, other than the
above-mentioned passive matrix type driving mode in which the time
division driving is performed using the scanning electrode and the
data electrode.
[0091] In the active matrix type organic EL display, each pixel 252
comprises an organic EL element 250 constituted by a part of the
organic layer, a driving transistor TR2 which controls current
supply to the organic EL element 250, a writing transistor TR1
which turns on by being applied a scanning voltage SCAN from the
scanning electrode, and a capacitor element C which holds charge by
being applied a data voltage DATA from the data electrode when the
writing transistor TR1 turns on, as shown in FIG. 12. The output
voltage of the capacitor C is applied to a gate of the driving
transistor TR2.
[0092] At first, a voltage is applied to each scanning electrode,
then the first transistors Tr1 connected to this scanning electrode
turns on. The data voltage (input signal) is applied to each data
electrode synchronizing with this scan. The data voltage is held in
the capacitor C at this time, because the first transistor TR1 is
on.
[0093] The operating state of the second transistor TR2 is
determined by the charge quantity held in this capacitor C. When
the second transistor TR2 turns on, for example, current according
to the data voltage is supplied to the organic EL element via the
second transistor TR2. Consequently, The organic EL element 250
emits light with brightness according to the data voltage.
[0094] By the way, in the organic EL display, the luminescence
characteristic of the organic EL element deteriorates with progress
of luminescence time, the luminance obtained by the same input
current may decrease consequently. In a cellular phone comprising
the organic EL display, the luminescence frequency of pixels in a
fixed area always becomes high when displaying a character of an
e-mail on a screen. Thereby, the luminescence characteristic of
these pixels deteriorate remarkably compared with other pixels. The
problem so-called "phosphor burn-in" may arise as a result.
[Summary of the Second Embodiment]
[0095] The object of the present embodiment is to solve a problem
of the "phosphor burn-in" with simple structure in a cellular phone
comprising an organic EL display.
[0096] The mobile terminal according to this embodiment comprises
an image processing circuit which can switch a display mode between
a black character display mode in which a character part is
displayed in black or a color with luminosity lower than that of a
background part and the background part is displayed in white or a
color with luminosity higher than that of the character part, and a
white character display mode in which the background part is
displayed in black or a color with luminosity lower than that of
the character part and the character part is displayed in white or
a color with luminosity higher than that of the background part,
when displaying an electric mail on an organic electro-luminescence
display apparatus; and a control circuit which controls an
operation of said image processing circuit; wherein said control
circuit alternately switches the display mode between the black
character display mode and the white character display mode.
[0097] The control circuit may instruct a mode switch between the
black character display mode and the white character display mode
in accordance with a predetermined rule in the concrete. As a
predetermined rule, the rule of changing the mode between a display
of transmitted mail and a display of received mail, and the rule of
changing the mode with a fixed cycle are employable, for
example.
[0098] The control circuit may switch the mode at a random
timing.
[0099] The mode switching described above can be achieved by simple
change of the control program.
[0100] In the mobile terminal according to the present invention,
the black character display mode in which a character is displayed
with lower luminance and the white character display mode in which
a character is displayed with higher luminance can be switched with
a predetermined cycle, at a predetermined timing according to an
operation of a user, or at a random timing. Thereby, the situation
where only the pixel in a fixed area always emits light with high
luminance can be avoided, and the problem of "phosphor burn-in" can
be solved.
[Example of the Second Embodiment]
[0101] Hereinafter, an embodiment in which the present invention is
carried out to the cellular phone will be concretely explained
making reference to drawings.
[0102] As shown in FIG. 7, the mobile telephone of the present
embodiment comprises a transmission and reception circuit 202, an
image processing circuit 203 for displaying an electronic mail
received or to be transmitted by the transmission and reception
circuit 202 on an organic EL display 201, a driving circuit 204
which drives the organic EL display 201 in response to an image
signal from the image processing circuit 203, and a control circuit
205 consisted of a micro computer which controls operations of the
transmission and reception circuit 202 and the image processing
circuit 203.
[0103] FIG. 9 shows procedures performed in case the control
circuit 205 displays an e-mail on the organic EL display 201. At
first, it is judged whether an electronic mail to be displayed is
transmitted mail or not, at the step S1.
[0104] If the mail to be displayed is a transmitted mail, a black
character display mode in which a character part is displayed in
black and a background part is displayed in white is set as shown
in FIG. 8A, and the control circuit 205 supplies a mode switching
signal to the image processing circuit 203, at the step S2.
[0105] On the other hand, if the mail to be displayed is a received
mail, a white character display mode in which a character part is
displayed in white and a background part is displayed in black is
set, and the control circuit 205 supplies a mode switching signal
to the image processing circuit 203, at the step S3 of FIG. 9.
[0106] The transmitted mail is displayed in the black character
display mode on the organic EL display 201 as shown in FIG. 8A, and
the received mail is displayed in the white character display mode
on the organic EL display 201 as shown in FIG. 8B,
consequently.
[0107] FIG. 10 shows other procedures performed in case the control
circuit 205 displays an e-mail on the organic EL display 201. At
first, it is judged whether today is even-numbered day or not, at
the step S11.
[0108] If today is even-numbered day, a black character display
mode in which a character part is displayed in black and a
background part is displayed in white is set as shown in FIG. 8A,
and the control circuit 205 supplies a mode switching signal to the
image processing circuit 203, at the step S12.
[0109] On the other hand, if today is odd-numbered day, a white
character display mode in which a character part is displayed in
white and a background part is displayed in black is set, and the
control circuit 205 supplies a mode switching signal to the image
processing circuit 203, at the step S13 of FIG. 10.
[0110] The transmitted mail and the received mail are displayed in
the black character display mode on the organic EL display 201 at
even-numbered day as shown in FIG. 8A, and displayed in the white
character display mode on the organic EL display 201 at
odd-numbered day as shown in FIG. 8B, consequently.
[0111] In the mobile telephone of the present embodiment, since the
black character display mode and the white character display mode
are switched by whether an E-mail is a transmitted mail or a
received mail, or whether today is an even-numbered day or an
odd-numbered day, the luminance of pixels which constitute the
organic EL display 201 can be averaged in time over the whole
screen, and deviation of the luminance can be reduced.
Consequently, the "Phosphor burn-in" resulting from only some
pixels carrying out age degradation early can be prevented.
[0112] Moreover, in a conventional mobile telephone which always
displays a character part in black and a background part in white,
the power consumption of the organic EL display was large because
the white background part occupies larger area than the black
character part. In the mobile telephone of the present embodiment,
however, the power consumption can be reduced because the black
character display mode and the white character display mode can be
switched.
[0113] Each component of the present invention is not limited to
the above-mentioned embodiment. Various changes can be made without
departing from the scope of the technology which is described in
the claims.
[0114] Various changing rules are employable, for example: a rule
in which the black display mode and the white display mode are
switched every time the power of the cellular phone is turned on; a
rule in which the mode is switched every time a mail screen is
displayed; a rule in which the mode is switched between a case of
writing mail and a case of reading mail; a rule in which the mode
is switched for every time or predetermined number of times on the
occasion of a display of a mail at the time of mail creation; a
rule in which the mode is switched for every time or predetermined
number of times on the occasion of a display of a mail which has
already been received or transmitted. Moreover, the structure where
the mode is switched at a random timing without following a
predetermined rule can be adopted.
[Effect of the Second Embodiment]
[0115] The "phosphor burn-in" problem can be solved with simple
component by a mobile terminal comprising an organic EL display
according to the present embodiment.
Third Embodiment
[Field of the Third Embodiment]
[0116] The present embodiment relates to a method for displaying a
specific picture (a picture writing) called "PICT" like an antenna
picture, a picture showing residual quantity of a battery, and the
like, in a cellular phone comprising an organic EL (Electro
Luminescence) display.
[Related Art of the Third Embodiment]
[0117] In a color organic EL display, one color pixel is
constituted by three kinds of organic EL elements (R luminescent
element, G luminescent element, and B luminescent element) which
emit R, G, and B light respectively. The luminescent elements
deteriorates and luminance thereof decreases, if the color organic
EL display is used over a long term. Especially, if large current
is continuously supplied to the luminescent element, that is, the
luminescent element continuously emits light with high luminance,
the speed of reduction of luminance becomes high.
[Summary of the Third Embodiment]
[0118] The object of this embodiment is to provide a display method
of a specific picture that can make hard to be conspicuous in
luminance degradation with displaying the picture.
[0119] A display method according to the first aspect of the
present embodiment is a display method of a specific picture which
is displayed on a color organic EL display and a lighting part
thereof increases or decreases according to a situation, wherein
the higher a probability of lighting of a part, the lower luminance
of the part is set beforehand.
[0120] A display method according to the second aspect of the
present embodiment is a display method of the specific picture
according to the first aspect, wherein the specific picture is a
picture showing an antenna and/or a picture showing residual
quantity of a battery.
[0121] A display method according to the third aspect of the
present embodiment is a display method of a specific picture which
is displayed at areas which overlie each other on a color organic
EL display, in which two or three kinds of the specific picture in
roughly classification are switched and displayed according to a
situation, wherein a dot which constitutes each specific picture is
set up in a manner where a color of an emitting element turned on
differs mutually among the two or three kinds of the specific
picture.
[0122] A display method according to the fourth aspect of the
present embodiment is a display method of the specific picture
according to the third aspect, wherein the specific picture is a
picture of an antenna which is switched between a first picture
showing an antenna bar and a second picture showing a character
showing outside an area where an electric wave reaches.
[0123] A display method according to the fifth aspect of the
present embodiment is a display method of the specific picture
according to the third aspect, wherein the specific picture is a
picture showing residual quantity of a battery which is switched
between a first picture showing a bar showing the residual quantity
of the battery and a second picture showing a character showing a
charge.
[0124] A display method according to the sixth aspect of the
present embodiment is a display method of a plurality of specific
pictures which is displayed on a color organic EL display, wherein
the higher a frequency of displaying a pixel is, the lower
luminance of the pixel is set beforehand.
[Example of the Third Embodiment]
[0125] Hereinafter, an example where the present invention is
adopted to a cellular phone comprising a color organic EL display
will be explained with reference to drawings.
[0126] FIG. 13 shows a schematic structure of a cellular phone. An
MPU 3109 controls a cellular phone as a whole. An antenna 3101
transmits and receives an electric wave. A transmitter-receiver
unit 3102 receives the electric wave and transmits the received
content to the MPU 3109. The transmitter-receiver unit 3102
transmits a transmission signal outputted from the MPU 3109 with
the electric wave.
[0127] A microphone 3101 communicates an audio signal to the MPU
3109. A speaker 3104 outputs an audio signal outputted from the MPU
3109 as a sound. A first camera 3105 is a camera attached in the
front of a main body of the cellular phone in which a color organic
EL display 3114 is formed, and transmits shot image to the MPU
3109. A second camera 3106 is a camera attached in the back of the
cellular phone, and transmits shot image to the MPU 3109. At a
shooting mode, an image shot by the camera 3105 or 3106 is
displayed on the color organic EL display 3114 instead of a display
image at a normal mode.
[0128] An operating unit 3108 is comprised in the main body of the
cellular phone, includes various buttons and various switches. In a
flash memory 3110, data which should be saved when a power turns
off are stored.
[0129] In a graphics memory 3112, image data to be displayed on the
display is stored. Image data is written at the predetermined
address in the graphics memory 3112 based on the image data and a
write control signal outputted from the MPU 3109. Pixel data of the
pixel corresponding with a display cycle of the color organic EL
display is outputted from the graphics memory 3112 according to a
scan timing. A timing control IC 3113 supplies a drive signal to
the organic EL display 3114 with the image data, and displays an
image on the color organic EL display 3114.
[0130] In the color organic EL display 3114, a single color pixel
is constituted with three kinds of organic EL elements (R
luminescent element, G luminescent element, B luminescent element)
which emit light in R, G, B, respectively. Such a color organic EL
display 3114 includes the organic EL element for each color
luminescence of RGB (R luminescent element, G luminescent element,
B luminescent element).
[0131] In such a cellular phone, a battery residual quantity
picture which shows residual quantity of a battery and an antenna
picture which shows reception sensitivity are displayed on the
upper part of the display screen of the color organic EL display
3114. In the present embodiment, the following three methods are
proposed as the display method of such specific pictures.
[0132] The first method is a display method of a specific picture
which is displayed on a color organic EL display 314 and a lighting
part thereof increases or decreases according to a situation,
wherein the higher a probability of lighting of a part, the lower
luminance of the part is set beforehand.
[0133] The second method is a display method of a specific picture
which is displayed at areas which overlie each other on a color
organic EL display 3114, in which two or three kinds of the
specific picture in roughly classification are switched and
displayed according to a situation, wherein a dot which constitutes
each specific picture is set up in a manner where a color of an
emitting element turned on differs mutually among the two or three
kinds of the specific picture.
[0134] The third method is a display method of a plurality of
specific pictures which is displayed on a color organic EL display
3114, wherein the higher a frequency of displaying a pixel is, the
lower luminance of the pixel is set beforehand.
[0135] Hereinafter, these method will be explained more
concretely.
[0136] [1] Explanation about the First Method
[0137] [1-1] Explanation in the Case where the First Method is
Adopted to the Battery Residual Quantity Picture
[0138] As shown in FIGS. 14A-14E, a first picture showing a level
of the residual quantity of the battery with 0 to 3 bars (FIGS.
14A, 14B, 14C, 14D), and a second picture showing a character of
"charge" (FIG. 14E) are prepared for displaying the battery
residual quantity picture. This second picture is displayed when
the residual quantity of the battery decreases extremely.
[0139] The first picture consists of a battery frame figure
imitated the battery and bars displayed in the battery frame
figure. As shown in FIGS. 14A, 14B, 14C, and 14D, the bars
displayed in the battery frame figure change to four stages like 3,
2, 1, and 0. The more bars are displayed, the more residual
quantity of the battery is left.
[0140] Five kinds of images shown in FIGS. 14A, 14B, 14C, 14D, and
14E are switched and displayed according to the battery residual
quantity level. The first picture (bar) is displayed in green for
example, and the second picture (character of "charge") is
displayed in red.
[0141] In the first method, the higher a probability of lighting of
a bar, the lower the luminance of the bar is set beforehand. The
probability of lighting of the rightmost bar is highest, the
probability of lighting of the leftmost bar is lowest, and the
probability of the middle bar is middle of the rightmost bar and
the leftmost bar. Therefore, the display luminance of the rightmost
bar 313 is set lowest, the display luminance of the leftmost bar
311 is set highest, and the display luminance of the middle bar 312
is set as the intermediate value thereof.
[0142] FIGS. 16A and 16B show a change over time of the display
luminance of the rightmost bar which has high probability to light
(solid line) and a change over time of the display luminance of the
leftmost bar which has low probability to light (doted line).
[0143] FIG. 16A shows a change over time of the display luminance
in the case where the display luminance of the bar which has high
probability to light is set low beforehand (the first method). FIG.
16B shows a change over time of the display luminance in the case
where the display luminance of the bars are set as equal value
beforehand (the conventional method).
[0144] The reduction speed of the display luminance of the
rightmost bar which has high probability of lighting is higher than
that of the leftmost bar which has low probability of lighting.
Thereby, the difference between the display luminance of these bars
becomes gradually large when accumulated usage time of the cellular
phone becomes long.
[0145] The display luminance of the leftmost bar and the display
luminance of the rightmost bar are gradually averaged and the
difference between the display luminance of both becomes small as
accumulative use time becomes large, because the display luminance
of the bar which has higher probability of frequency of lighting is
set lower beforehand. If it passes over the time when the
difference between the display luminance of both becomes zero, the
difference of the luminance spreads to the opposite direction. Use
time can be extended until the difference of the luminance becomes
incapable for visibility.
[0146] Considering three bars, the display luminance of each bars
are gradually averaged and the differences between the display
luminance values of each bars become small as accumulative use time
becomes large, because the display luminance of the bar which has
higher probability of frequency of lighting is set lower beforehand
in the first method. If it passes over the time when the difference
between the display luminance of each bars becomes zero, the
difference of the luminance spreads to the opposite direction. Use
time can be extended until the difference of the luminance becomes
incapable for visibility.
[0147] [1-2] Explanation in the Case where the First Method is
Adopted to the Antenna Picture
[0148] As shown in FIGS. 17A-17E, a first picture showing a
receiving sensitivity with 0 to 3 bars (FIGS. 17A, 17B, 17C, 17D),
and a second picture showing a character of "outside" (FIG. 17E)
are prepared for displaying the antenna picture. This second
picture is displayed when the receiving sensitivity decreases
extremely.
[0149] The first picture consists of a antenna figure imitated the
antenna and bars displayed right side of the antenna figure. As
shown in FIGS. 17A, 17B, 17C, and 17D, the bars displayed right
side of the antenna figure change to four stages like 3, 2, 1, and
0. The more bars are displayed, the higher the receiving
sensitivity of the antenna is.
[0150] Five pictures shown in FIGS. 17A-17E is switched and
displayed according to receiving sensitivity. The first picture is
displayed in green, the second picture is displayed in red, for
example.
[0151] In the first method, the higher a probability of lighting of
a bar, the lower the luminance of the bar is set beforehand. The
probability of lighting of the leftmost bar is highest, the
probability of lighting of the rightmost bar is lowest, and the
probability of the middle bar is middle of the rightmost bar and
the leftmost bar. Therefore, the display luminance of the leftmost
bar 321 is set lowest, the display luminance of the rightmost bar
323 is set highest, and the display luminance of the middle bar 322
is set as the intermediate value thereof, as shown in FIG. 18.
[0152] Also in this case, the display luminance of each bars are
gradually averaged and the differences between the display
luminance values of each bars become small as accumulative use time
becomes large, because the display luminance of the bar which has
higher probability of frequency of lighting is set lower beforehand
in the first method. If it passes over the time when the difference
between the display luminance of each bars becomes zero, the
difference of the luminance spreads to the opposite direction. Use
time can be extended until the difference of the luminance becomes
incapable for visibility.
[0153] [2] Explanation about the Second Method
[0154] A display method of a specific picture which is displayed at
areas which overlie each other on a color organic EL display, in
which two or three kinds of the specific picture in roughly
classification are switched and displayed according to a situation,
wherein a dot which constitutes each specific picture is set up in
a manner where a color of an emitting element turned on differs
mutually among the two or three kinds of the specific picture.
[0155] As mentioned above, in the color organic EL display 3114, a
single color pixel is constituted with three kinds of organic EL
elements (R luminescent element, G luminescent element, B
luminescent element) which emit light in R, G, B, respectively.
That is, the single color pixel is constituted with three dots.
[0156] As the battery residual quantity picture, the first pictures
showing residual quantity level of the battery with 0-3 bar(s)
(FIGS. 14A, 14B, 14C, 14D) and the second picture showing the
character of "charge" (FIG. 14E) are switched and displayed
according to the situation as mentioned above.
[0157] In the second method, the dots which constitute the first
picture (bar) and the second picture (character of charge) are set
in a manner where the kind of color of the emitting elements turned
on when displaying these pictures differs each other.
[0158] FIG. 19A shows dots which constitute the picture
(corresponding to the picture shown in FIG. 14A) in which the
lighting pixels are most among the first pictures. FIG. 19B shows
dots which constitute the second picture (corresponding to the
picture shown in FIG. 14E). FIG. 19C shows a relation between the
position of the dots which constitute the first picture and the
position of the dots which constitute the second picture.
[0159] In this example, the first picture is displayed only in
green. All of the dots which constitute the first picture are G
emitting elements. On the other hand, the second picture is
displayed only in red. All of the dots which constitute the second
picture are R emitting element.
[0160] The dots which constitute either the first picture or the
second picture may consist of the emitting elements of two colors
(for example, R emitting element and G emitting element), and the
dots which constitute another picture may consist of a color
different from above-mentioned two colors (for example, B emitting
element).
[0161] In the second method, the dots which constitute the first
picture and the second picture are set in a manner where the kind
of color of the emitting elements turned on when displaying these
pictures differs each other.
[0162] Therefore, the one picture is not influenced by the
degradation of the luminance of another picture among the first
picture and the second picture, even if these pictures are
displayed almost the same area.
[0163] The second method can be also adopted to the first picture
showing the receiving sensitivity with 0-3 bar(s) (FIGS. 17A, 17B,
17C, 17D) and the second picture showing the character of "outside"
(FIG. 17E) in the antenna picture.
[0164] [3] Explanation about the Third Method
[0165] FIG. 20 shows pictures which can be displayed on upper part
of the color organic EL display 3114.
[0166] In the third method, the higher a frequency of displaying
the picture is, the lower luminance of the picture is set
beforehand among these pictures 331-338.
[0167] Concretely, the picture 331 is a picture showing a state
during a telephone call. The picture 331 is displayed only during
the telephone call. The display luminance of thereof is set high
beforehand because the frequency of a display of the picture 331 is
low.
[0168] The picture 332 is a picture showing residual quantity of
the battery. The picture 332 is always displayed. The display
luminance thereof is set low beforehand because the frequency of a
display of the picture 332 is high.
[0169] The picture 333 is a picture showing a state where a key of
the cellular phone is locked. The picture 333 is only displayed
when the key is locked. The display luminance thereof is set high
beforehand because the frequency of a display of the picture 333 is
low.
[0170] The picture 334 is a picture showing a state where the
cellular phone is in the manner mode. The picture 334 is only
displayed when the cellular phone is in the manner mode. The
display luminance thereof is set high beforehand because the
frequency of a display of the picture 334 is low.
[0171] The picture 335 is a picture showing a reception of a mail.
The picture 334 is only displayed when the mail is received. The
display luminance thereof is set high beforehand because the
frequency of a display of the picture 335 is low.
[0172] The picture 336 is a picture showing a state where a search
on the web is performed. The picture 336 is only displayed when the
search on the web is performed. The display luminance thereof is
set high beforehand because the frequency of a display of the
picture 336 is low.
[0173] The picture 337 is a picture showing the antenna. The
picture 337 is always displayed. The display luminance thereof is
set low beforehand because the frequency of a display of the
picture 337 is high.
[0174] The picture 338 is a picture showing a state where the
cellular phone is in the character input mode. The picture 338 is
only displayed when the character is inputted. The display
luminance thereof is set high beforehand because the frequency of a
display of the picture 338 is low.
[0175] That is, the display luminance of the pictures 332 and 337
which are frequently displayed is set low among the pictures
331-338 in the example shown in FIG. 20.
[Effect of the Third Embodiment]
[0176] According to the present embodiment, luminance degradation
with displaying the specific picture can be made hard to be
conspicuous.
Fourth Embodiment
[Field of the Fourth Embodiment]
[0177] The present embodiment relates to a display apparatus and a
display method, and it particularly relates to a technology for
improving a display quality of the display apparatus and the
display method.
[Related Art of the Fourth Embodiment]
[0178] Notebook type personal computers and mobile terminals are
spreading widely. A liquid crystal display is mainly used as a
display apparatus thereof. Organic EL (Electro Luminescence)
display is expected as a next-generation flat display panel. As for
the liquid crystal display, the straitness of the view angle and
the lateness of response speed still remain as a subject. On the
other hand, the organic EL display can solve the above-mentioned
subject and can achieve high luminosity and high efficiency.
[0179] As for the organic EL display, however, it can not be
avoided a change with the passage of time, that is, degradation, of
an optical element because of the characteristic thereof. A white
balance may collapse or a variation of luminance may be arisen by
continuous use, even if the white balance is adjusted at the time
of manufacture. It is known that degradation of the optical element
of the organic EL display is remarkable compared with that of the
liquid crystal display, and it is recognized that it is a big
problem in view of the quality of a product.
[Summary of the Fourth Embodiment]
[0180] The present embodiment has been made in view of the
foregoing circumstances and an object thereof is to improve
reduction of display quality caused by the above-mentioned
variation of the luminance. Another object thereof is to avoid a
phosphor burn-in of a display image caused by localizing the
variation of the luminance.
[0181] An aspect of the present embodiment relates to a display
apparatus. This apparatus is a display apparatus comprising: an
optical element; a luminance information storing unit which stores
luminance information set to said optical element; and a display
changing unit which changes a display image displayed on said
display apparatus in a manner where a guessed value of degradation
of each optical elements can be averaged based on the luminance
information stored.
[0182] Here, the display apparatus means an apparatus comprising a
display screen, for example, a cellular phone, a PDA (Personal
Digital Assistant), a personal computer, and the like. An organic
light emitting diode (hereinafter, simply referred to as "OLED") as
an optical element of an organic EL display deteriorates with
passage of time as mentioned above. Cause of the deterioration is
considered a current supplied to the OLED. The degradation of the
OLED can be assumed by monitoring a luminance set to the OLED, for
example, storing accumulated luminance set to the OLED, since the
luminance of light emitted from the OLED is dependent on the
current. If the degradation of the OLED is averaged, the variation
of the luminance can be avoided.
[0183] Generally, a specific character or a specific image is
displayed on a specific position in the display screen of the
cellular phone in many cases. It may cause the phosphor burn-in.
The degradation of the OLED can be averaged by changing a display
position, luminance, or color tone of the character and the image
displayed. Here, "average" may be a state almost equalized, and
equalization should just be the grade where a user cannot recognize
the variation of the luminance.
[0184] In the case of color display in the organic EL display, the
degradation speed of the OLEDs of R (Red), G (Green), and B (Blue)
differs since the materials thereof differ each other. Thereby,
there may be arisen a phenomenon that the display image is
displayed in a little green for example as the display is used.
Therefore, it is necessary to equalize the grade of degradation of
the OLED of each color of R, G, and B.
[0185] Another aspect of the present embodiment also relates to a
display apparatus. This apparatus is a display apparatus
comprising: an optical element; and a display changing unit which
changes a display image displayed on said display apparatus in a
manner where a guessed value of degradation of each optical element
can be averaged, maintaining an outline of the display image.
[0186] Further another aspect of the present embodiment also
relates to a display apparatus. This display apparatus is a display
apparatus comprising: an optical element; a display screen which is
composed of a plurality of display areas; and a display changing
unit which changes a display image of each display area,
maintaining an identity of a content of the display.
[0187] A display screen of the cellular phone, for example, may be
divided into a plurality of areas. A horizontally long and slender
display area is set in the upper part of many cellular phones, and
the picture which showing the residual quantity of a battery and
the picture showing the intensity of an electric wave are displayed
there. These pictures are always displayed. Thereby, if the display
area of these pictures is burned in, there arises a possibility
that a user can not recognize the residual quantity of the battery
and the intensity of the electric wave. It is convenient that the
picture displayed is changed for every divided area.
[0188] The display changing unit may change the display image
again, when a guessed value of degradation of the optical element
reaches a predetermined value from the last change as a starting
point. For example, the display image may be changed when the
accumulated value of the luminance set to the optical element
exceeds a predetermined value, and the accumulated value of the
luminance may be initialized in the case where the change is
performed. The display changing unit may change the display image,
when an absolute value of an accumulated difference of a luminance
of neighboring pixels exceeds a predetermined value.
[0189] That is, the difference between the degradation of optical
elements of neighboring pixels can be assumed by calculating the
difference of the luminance thereof. The degradation of the pixel
for a accumulating term can be assumed by accumulating the
difference over the term.
[0190] The display changing unit may change the display image, when
a difference of a guessed value of degradation of the optical
element in a row or a column of even number and odd number exceeds
a predetermined value. That is, The display image may be changed
when a difference between the accumulated luminance set to the
even-numbered row and the accumulated luminance set to the
odd-numbered row, or a difference between the accumulated luminance
set to the even-numbered column and the accumulated luminance set
to the odd-numbered column exceeds a predetermined value.
[0191] The display image may be changed when following two
conditions are fulfilled. First, the difference of the luminance
set to the even-numbered and odd-numbered rows or columns in the
image previously displayed is accumulated. The difference of the
luminance set to the even-numbered and odd-numbered rows or columns
in the image to be displayed next is accumulated. Then, the display
image may be changed so that the degradation of the optical element
can be averaged according to whether each accumulated value is
positive or negative. Moreover, the luminance set to the
even-numbered and odd-numbered rows or columns in the image
previously displayed is accumulated. The luminance set to the
even-numbered and odd-numbered rows or columns in the image to be
displayed next is accumulated. Then, the display image may be
changed so that the degradation of the optical element can be
averaged according to which of the accumulated values is greater.
In the case of these two conditions, it is not necessary to prepare
a memory storing a predetermined value which is a threshold value
at the time of changing the display image in a circuit.
[0192] The display changing unit may change, when a power supply of
the display apparatus is turned on or off, the display image in the
process of turning the power on or off. For example, a user may not
be noticed the change of the display image by changing the display
image when the user does not see the display apparatus. The display
changing unit may change, when an application displayed on the
display apparatus is changed, the display image in the process of
the change of the application.
[0193] The display screen of the display apparatus can be opened
and closed, the display apparatus may further comprise an
opening-and-closing detecting unit which detects opening or closing
of the display screen; and the display changing unit may change the
display screen when opening and closing of the display screen are
detected by the opening-and-closing detecting unit. An operating
unit for operating the display apparatus may be slide-type; the
display apparatus may further comprise a slide detecting unit which
detects a slide of the operating unit; and the display changing
unit may change the display screen when the slide of the operating
unit is detected by the slide detecting unit. For example, in the
case where the operating unit like a keyboard is normally hidden
under the display screen and is slid out when operating in the
cellular phone, the display screen may be changed by operation of
sliding out or closing of the operating unit.
[0194] The display changing unit may change the display image by
shifting a display position of the display image. The display
changing unit may adjust a signal set up to each optical element
according to a guessed value of degradation of the optical element.
For example, the degradation grade of the optical element may be
assumed by accumulating the luminance set to the optical element as
mentioned above. The luminance set to the optical element whose
degradation is assumed large may be adjusted so that the variation
of the luminance can be avoided based on the thus assumed value of
degradation.
[0195] The display changing unit may include an area detecting unit
which detects a specific area, the display position thereof is to
be shifted, among an area of the display image; and the display
changing unit may change the display image by shifting the display
position of the specific area detected. The display image can be
relatively easily changed if the size and the display position is
managed by an MPU or a memory comprised by the display apparatus.
On the other hand, although a display screen appears to be divided
into plurality, the display screen displayed on each may not be
managed individually, but may be substantially managed as one
display screen inside the display apparatus. Even in such a case,
only a certain image displayed on the certain divided display
screen may be shifted.
[0196] For example, a display screen of a cellular phone is
exemplified. The display screen of the cellular phone comprises
elongated display areas in top and bottom, and relatively large
display area in middle. In the top and bottom area, an image
showing a state of an electric wave and an image showing residual
quantity of a battery are displayed for example. In the middle
area, an electric mail is displayed, or a background image is
displayed when the cellular phone is not used.
[0197] Only the background image displayed in the middle display
area may be shifted since there is a possibility of phosphor
burn-in if the same image is always displayed. When three areas are
managed as one display screen, only the image displayed in the
middle needs to be taken out and shifted. When the image is
constituted by the background image of a single color and an image
such as an illustration in it, Only the illustration is taken out
and shifted.
[0198] The display changing unit may determine an amount of
compensation to be given to a signal according to a value of the
signal, when adjusting the signal set up to said optical element.
For example, if the same amount of compensation is given to the
signal in the case where the low luminance is set to the optical
element and in the case where the high luminance is set to the
optical element, there is a possibility that the influence given to
the display image in the case where the low luminance is set is
larger. Thereby, a processing of reducing the amount of
compensation given to the signal is performed when the low
luminance is set.
[0199] The display changing unit may determine an amount of
compensation to be given to a signal based on the guessed value of
degradation of the optical element of a surrounding pixel, when
adjusting the signal set up to the optical element.
[0200] The display changing unit may change the display image by
changing a display color of each optical element. The display
changing unit may change the display color for a predetermined
cycle. As mentioned above, when the accumulated luminance is
reached to a predetermined value, and there is not an input from a
user for a predetermined term, in a case where the accumulated
value of luminance of green is small for example, the whole display
image may be changed to green. The change of the display color may
be made by changing gradually a luminance ratio of the optical
element corresponding to each color which constitutes a pixel.
[0201] A display area needed for displaying an actual display image
may be set up smaller than an effective display area which can be
displayed in said display apparatus; and the display changing unit
may shift the display area in the effective display area. For
example, in the case where the display screen is constituted by
105*105 pixels, the display area to be actually displayed may be
100*100 pixels, and five pixels of vertical and horizontal
direction may be an area in which the image can be shifted.
[0202] The optical element may correspond to a dot, a pixel may
include dots of a plurality of colors, and the display changing
unit may shift the display image per dot, and may change
combination of the optical elements which originally constitute one
pixel. As mentioned above, one pixel of the color display apparatus
is generally constituted by dots of three colors of R, G, and B.
Thereby, the display image may be shifted per pixel or per dot.
[0203] In a case where the display image to be shifted includes a
character, the display changing unit may set a margin space which
is originally set for displaying the character not to touch each
other as an area in which the arbitrary character can be shifted.
Generally, the font does not use one line in one side of the
display area so that the font may not contact with a neighbor font,
and the line is set as the margin area. In a case of the font of
16*16 pixels, for example, only 15*15 pixels are used actually.
Thereby, each vertical and horizontal one line can be used as the
display area of the font.
[0204] In a case where the display image to be shifted includes a
character, the display changing unit may shift the display image to
a direction in which influence for readability of the character is
small when a user sees the character. For example, the display
changing unit may scroll the character string horizontally when the
user sees an e-mail on the display screen of the cellular
phone.
[0205] The display changing unit may scroll the display image or
may perform a mosaic processing to the display image and displays
it when there is no input from a user for predetermined period. A
size of a block generated by the mosaic processing may be changed
with passage of time.
[0206] The display changing unit may select, when a background
image which functions as a wallpaper is newly set up, the wallpaper
according to grade of degradation of said optical element. Here,
"set the wallpaper" means both of a case where a new wallpaper is
selected as the background image, and a case where a color of the
displayed wallpaper is changed and set as the background image.
[0207] The reduction of the luminance of each color can be averaged
by changing the color of the wallpaper according to the grade of
the assumed degradation of the optical element. Moreover, in a case
where the reduction of the luminance of red is assumed large, the
reduction of the luminance of each color can be averaged by setting
an image in which green and blue is largely used as the
wallpaper.
[0208] The color tone of the wallpaper may be changed by adjusting
the white balance of the selected wallpaper so that the degradation
of the optical element corresponding to each color of RGB can be
averaged. Since the advance degrees of degradation of the OLED of
each color differ in the organic EL display especially, such a
setup is highly effective.
[0209] Another aspect of the present embodiment relates to a
display method. This method is a display method in a display
apparatus which comprises an optical element, the method including:
storing information of luminance set up to the optical element; and
changing a display image displayed on the display apparatus in a
manner where a guessed value of degradation of each optical element
can be averaged based on the luminance information stored.
[0210] Further another aspect of the present embodiment also
relates to a display method. This method is a display method in a
display apparatus which comprises an optical element, the method
including: changing a display image displayed on the display
apparatus in a manner where a guessed value of degradation of each
optical element can be averaged, maintaining an outline of the
display image.
[0211] Optional combinations of the aforementioned constituting
elements, and implementations of the invention in the form of
methods, apparatuses and systems may also be practiced as
additional aspects of the present invention.
[Example of the Third Embodiment]
[0212] Premise Technology
[0213] In advance of explanation of the present embodiment, a
structure of an organic EL display as the premise technology of the
present embodiment is explained. FIG. 21 is a block diagram showing
a basic structure of an organic EL display apparatus 410. The
organic EL display apparatus 410 is constituted by an image source
input unit 420, an organic EL driving circuit 430, and an organic
EL panel 460.
[0214] The organic EL driving circuit 430 comprises an image
adjusting unit 432 which carries out various processings to a
digital image signal inputted from the image source input unit 420,
an MPU (Micro Processing Unit) 434 which calculates when these
processings are carried out, and a DAC (Digital to Analog
Converter) unit 442 which converts the image signal carried out
processing to an analog signal. The organic EL driving circuit 430
further comprises a control signal generating unit which generates
various timing control signals and a memory which functions a table
when actual processing is carried out, which are not shown in the
figure.
[0215] The image adjusting unit 432 performs an offset adjusting to
adjust a brightness, a gain adjusting to adjust a contrast, and a
processing to adjust input image signal which is performed gamma
correction to voltage-emitting luminance (V-T) characteristic of
the organic EL panel.
[0216] Operation by the above structure is explained briefly. Three
kinds of the digital signals R_in, G_in, and B_in are inputted from
the image source input unit 420 to the image adjusting unit 432.
The image adjusting unit 432 performs image adjusting processing
like the offset adjusting and the gain adjusting. The digital
signals are outputted from the DAC unit 442 as three kinds of
analog signals R_out, G_out, and B_out to the organic EL panel
460.
[0217] In terms of hardware, this structure can be realized by a
CPU, a memory and other LSIs of an arbitrary computer. In terms of
software, it is realized by memory-loaded programs or the like, but
drawn and described here are functional blocks that are realized in
cooperation with those. Thus, it is understood by the skilled in
the art that these functional blocks can be realized in a variety
of forms by hardware only, software only or the combination
thereof.
First Example
[0218] In a first example, luminance set to an OLED constituting
each dot of a display screen is monitored. When an accumulated
value thereof reaches a predetermined condition, a part or the
whole of a display image is shifted. The degradation of the OLED is
averaged by averaging the luminance set to the OLED corresponding
to each dot.
[0219] A condition of the accumulated value for shifting the
display image may be, for example, (1) when the accumulated value
of the luminance in a predetermined term exceeds a predetermined
value, (2) when the absolute value of the accumulated value of a
difference between the luminance of neighboring pixels exceeds a
predetermined value, (3) when a difference between the accumulated
value of the luminance of an even-numbered column and that of an
odd-numbered column exceeds a predetermined value.
[0220] FIG. 22 shows a state where a character "0" is displayed on
a display area of 9.times.8 pixels, and it is shifted one pixel to
the right and down direction respectively. A character shown by
black painting is a character before being shifted, and a character
shown with slash is a character after being shifted.
[0221] FIGS. 23A, 23B, and 23C show an example in which a display
image shifted per 1 dot. FIG. 23A shows an initial state before
being shifted, FIG. 23B shows a state where the display image is
shifted one dot to right direction, and FIG. 23C shows a state
where the display image is shifted 2 dots to right direction. In
the initial state, combination of colors of the dots which
constitute a pixel is R, G, B in order from the left. In the state
where the display image is shifted one dot to right direction, for
example, the combination is G, B, R in order from the left.
[0222] FIG. 24 shows a state where the display area A2 which is
actually displayed is set up smaller than an effective display area
A1 which can display the display picture. For example, when the
display area A2 consists of 100.times.100 pixels, the effective
display area A1 consists of 105.times.105 pixels. The display area
A2 has an area in which the display image can be shifted 5 pixels
in the length and the transverse direction each.
[0223] FIG. 25 shows a state where a Japanese character is
displayed on an area of 8.times.8 pixels. Pixels of the top line
and the rightmost column are set up as a blank space area so that
the character may not be touched with an adjoining character. This
area is also used as a display area at the time of shifting a
character. When the character sequence consists of two or more
characters, a character may shift 1 pixel to up, or 1 pixel to
right, or not shift at all, for example. Thereby, phosphor burn-in
can be reduced without spoiling display grace greatly.
[0224] The above-mentioned shift of the display image may be
carried out with a predetermined cycle. The shift can be performed
without making a user conscious of the shift by shifting the
display image when the user does not operate the display apparatus
or the display screen is changed considerably.
[0225] The timing of shifting may be, for example, (1) when the
power of the display apparatus turns on or off, (2) when the
display apparatus is opened or closed in a case where the display
apparatus can be opened and closed like a fold-down type cellular
phone, (3) when changing an application, (4) when there is no
operation from a user for a predetermined term, (5) when an
operating unit is slid out or closed in a case where the operating
unit of the cellular phone is a slide type and can be opened and
closed.
[0226] FIG. 26 shows a structure of an organic EL display apparatus
4100 according to the present example. The basic structure is the
same as the structure shown in FIG. 21 in the premise technology.
Particularly characteristic structure in the present example will
be explained.
[0227] An organic EL driving circuit 430 includes a luminance
accumulating unit 452 which acquires and stores luminance set to
the OLED, a look-up table 343 which stores an above-mentioned
condition about the accumulated luminance when shifting the display
image and how to shift the display image, and a shift condition
table 456 which stores above-mentioned timing of shifting. An image
adjusting unit 432 includes an image shifting unit 450 which
carries out processings for shifting and displaying the display
image. The organic EL apparatus 4100 includes a mode switch
detecting unit 470 which detects a timing of shifting the display
image.
[0228] The luminance accumulating unit 452 accumulates the
luminance set to each OLED which constitutes each pixel and stores
thus accumulated luminance. The image source input unit 420
includes an image changing unit 458 which carries out a mosaic
processing and color change of the display image shown in examples
2-4 with reference to the accumulated luminance stored in the
accumulated luminance storing unit 452.
[0229] Operation about the shift of the display image by the above
structure is explained briefly. The mode detecting unit 470 detects
the timing of shifting the display image, for example, when the
application is changed and the like, and transmits the timing to
the organic EL driving circuit 430. The MPU 434 refers to the shift
condition table 456. If it is the timing to shift, the MPU 434
further refers to the look-up table 454 based on the accumulated
luminance stored in the accumulated luminance storing unit 452. If
the accumulated luminance is in the predetermined condition, the
MPU 434 instructs to shift the display image to the image shifting
unit 450.
[0230] According to the first example, the degradation of specific
OLED can be avoided and the phosphor burn-in of the display screen
can be avoided by shifting the display image in accordance with the
accumulated value of the luminance set to the OLED. Moreover, the
degradation of the OLED in the whole display screen can be averaged
and the variation of the luminance can be reduced.
Second Example
[0231] In the first example, the display image is shifted per dot
or per pixel under a predetermined condition. In the second
example, when a predetermined time has passed after a user
operation is completed, a part of the displayed image is scrolled
horizontally or vertically, or is carried out a mosaic
processing.
[0232] FIG. 27A shows an initial display image, in which a white
circle and a black triangle are displayed. FIG. 27B shows a state
where images of the circle and the triangle are scrolled
horizontally. FIG. 27C shows a state where images of the circle and
the triangle are scrolled vertically.
[0233] For example, the degradation of the OLED is nearly equal in
an area A3 where the image of the circle shown in FIG. 27B is
scrolled. The average luminance in the whole display screen can be
equaled by combination of the scroll to the horizontal direction
and the scroll to the vertical direction.
[0234] FIGS. 28A and 28B show a state where the display image is
carried out a mosaic processing. This processing is also carried
out when a predetermined time has passed after completed the user
operation. FIG. 28A shows a display image at an initial state. FIG.
28B shows a display image carried out the mosaic processing. The
phosphor burn-in of the display screen can be further reduced by
changing a size of a block generated by the mosaic processing with
progress of time.
[0235] The above-mentioned scroll processing and mosaic processing
can be achieved by the structure of the apparatus shown in FIG. 25
in the first example. According to the second example, the same
effect as the first example can be acquired.
Third Example
[0236] In the first example and the second example, the degradation
of the OLED is averaged and the phosphor burn-in is reduced by
shifting the display image. In the third example, the degradation
grade of the OLED emitting light of each color of R, G, and B is
averaged by adjusting a signal set to the OLED corresponding to
each dot and adjusting a color of the display image.
[0237] In the case of adjusting the color, the color may be
adjusted only paying attention to a single pixel. The display image
may be divided into blocks, 3*3 pixels for example, and the color
may be adjusted so that balance in the block may be maintained. The
blocks may be changed with progress of time.
[0238] In the case where the color tone of the adjusted image is
changed remarkably from the display image before adjusted, the
amount of adjusting may be adjusted to make the color tone not
change a lot. For example, when the luminance ratio of R, G, and B
is 50% in white respectively, the adjusting may be made where the
luminance ratio or R is made into 49%, and the luminance ratio of G
and B are made into 51%, for example.
[0239] FIGS. 29A and 29B are schematic figures showing a state
where a display color is changed at a fixed timing to average the
emitting luminance of each color of RGB over time. The upper column
shows an emitting color and the lower column shows amplitude of a
signal. This change may be made per dot or may be performed to the
whole display screen.
[0240] FIG. 29A shows a state where only R is displayed among three
colors of RGB. The amplitude of the signal set to the OLED is 0
except R. When a predetermined time has passed after this state,
only G is emitted as shown in FIG. 29B for example. Here, RGB is
emitted individually, but mixed colors may be emitted.
[0241] Moreover, when changing the emitting color, the luminance
ratio of RGB may be gradually changed as shown in FIGS. 30A-30C. At
first, only R is emitting light as shown in FIG. 30A, then the
signal amplitude of R becomes small and G emits light as shown in
FIG. 30B. Furthermore, with progress of time, three colors of RGB
emit light with the same signal amplitude as shown in FIG. 30C.
[0242] Above-mentioned processing can be realized with the
structure shown in FIG. 26 of the first example. However, in this
example, since a display image is not shifted, the image shifting
unit 450 is unnecessary.
[0243] FIG. 31 is a flowchart showing a procedure of a processing
of the above-mentioned color change. After a predetermined time has
passed from end of the user operation (Y of S410), when the mode is
changed (Y of S412), the accumulated value of the luminance set to
the OLED constituting the display screen is acquired (S414). In the
case where the mode is not changed (N of S412), the procedure is
returned to the processing of S410.
[0244] In the case where the degradation of the OLED corresponding
to RGB is taken into consideration (Y of S416), the accumulated
value is multiplied by a predetermined degradation rate and
corrected (S418). In the case where the degradation rate is not
taken into consideration (N of S416) and after correction in S418,
the accumulated value of the luminance is inverted (S420). The
signal for averaging the accumulated value in the display screen is
outputted (S422). It subtracts from the inverted accumulated value
according to the luminance set (S424) and the accumulated value of
the luminance is updated (S426). If the updated accumulated value
is averaged in the display screen (Y of S428), this color change
processing is completed. If not averaged (N of S428), the steps
S414 to S426 is repeated.
[0245] In S420 and S424, the accumulated value is inverted and
subtracted the set luminance, but the processing may not be
restricted to this, the processing may be made as the maximum of
the accumulated value is calculated, and the set-up luminance is
added to average the accumulated value.
[0246] FIG. 32 is a flowchart showing a procedure of adjusting the
display image according to the accumulated value of the luminance
set to the OLED. The accumulated value of the luminance is acquired
(S450). In the case where the degradation of the OLED corresponding
to RGB is taken into consideration (Y of S452), the accumulated
value is multiplied by a predetermined degradation rate and
corrected (S454).
[0247] In the case where the degradation rate is not taken into
consideration (N of S452) and after correction in S454, it is
checked whether the accumulated value of the luminance is averaged
in the display screen. If averaged (Y of S456), the inputted signal
is outputted as it is (S462). If not averaged (N of S456), the gain
of the luminance set to each OLED is adjusted not to arise the
variation of the luminance (S458), and thus adjusted signal is
outputted (S460).
[0248] After the signal is outputted in S460 or S462, the
accumulated value is updated reflecting the luminance set (S464).
If the adjusting is continued (Y of S466), the steps S450 to S464
are repeated. If the adjusting is not continued (N of S466), the
processing is ended.
[0249] When adjusting the signal in S458, the gain is adjusted by
multiplication of the signal, but the processing may not be
restricted to this, the processing may be made by addition or
subtraction of the signal. As mentioned above, according to the
third example, the same effect as the first example and the second
example is acquired, and the adjust of the display image in
consideration of the variation of the luminance can be carried
out.
Fourth Example
[0250] In this example, when the background image which functions
as a wallpaper is newly set up, color tone of the wallpaper is
changed according to the grade of degradation of the OLED of each
dot of a display screen. This change of the color tone may be made
for vanishing the variation of the luminance caused by the
degradation the OLED, or for averaging the grade of degradation of
the OLED. For example, when it is presumed that the grade of
degradation of the OLED of R is large on the whole display screen,
the wallpaper is set up with the ratio of other G or the color of B
being enlarged.
[0251] The apparatus to realize this example can be realized with
the structure shown in FIG. 26 of the first example. As mentioned
above, according to the fourth example, the same effect as the
third example is acquired.
Fifth Example
[0252] In the present example, display screen of the cellular phone
is divided into three areas of upper, middle, and lower, and the
display image is shifted in each divided area independently. FIG.
33 is a figure showing the display screen of the cellular phone.
The display screen is divided into three areas of the first area
L1, the second area L2, and the third area L3, in order from the
top.
[0253] In the first area L1, a battery mark DM which is a picture
showing residual quantity of the battery is displayed in left side,
and an antenna mark AM which is a picture showing intensity of an
electric wave is displayed in right side. The battery mark DM and
the antenna mark AM are always displayed at a fixed position in
many cellular phones. There is a probability of phosphor burn-in of
these pictures. If the phosphor burn-in with a shape of the battery
mark DM is arisen, there arises a probability that residual
quantity of the battery cannot be shown properly to a user.
Thereby, the battery mark DM and the antenna mark AM are shifted in
only the first area L1. Since the first area L1 is horizontally
long, horizontal scrolling, horizontal swing and the like are
illustrated as the method of shifting the battery mark DM and the
antenna mark AM. The horizontal scroll means shifting the battery
mark DM and the antenna mark AM along a fixed direction. The
horizontal swing means shifting the antenna mark DM and the antenna
mark AM right and left by arbitrary number of pixels. That is, in
the horizontal swing, the battery mark DM and the antenna mark AM
is displayed swingingly.
[0254] The visibility does not get worse so much by shifting the
battery mark DM and the antenna mark AM only horizontally because
the display position thereof can be roughly predicted. Similarly,
the picture displayed on the third area L3 is also shifted in the
third area L3 maintaining visibility. The picture of a car
displayed on the second area L2 (hereinafter simply referred to as
a "car picture") TM may be scrolled arbitrary direction
horizontally and vertically since the car picture is a background
picture here, and the visibility thereof is not required from the
user. The car picture TM displayed on the second area L2 in the
middle once moves downward, then moves to down and right
direction.
[0255] FIG. 34 shows a state where the image displayed on the
display screen shown in FIG. 33 is shifted. The battery mark DM and
the antenna mark AM are scrolled right and left respectively. All
the pictures displayed on the third area L3 are scrolled right. The
car picture TM displayed on the second area L2 in middle is once
shifted below, and shifted to right bottom after that.
[0256] A structure of the cellular phone for shifting the display
image for every divided area. FIG. 35 is a figure showing the
structure of the cellular phone 4200 according to the present
example. The cellular phone 4200 comprises an MPU 434, a graphics
memory 474, a timing control IC (Integrated Circuit) 476, a flash
memory 472 and an organic EL panel 460. The cellular phone 4200
further comprises a speaker 462, a transmitter-receiver unit 464,
and a microphone 466.
[0257] The flash memory 472 stores data to be held when the power
of the cellular phone 4200 is off. The graphics memory stores image
data displayed on the organic EL panel 460. The image data is
written in the graphics memory 474 when receiving the image data
and a write position control of the image data from the MPU 434.
The graphics memory 474 outputs the image in response to an input
of a read control signal synchronized with the display from the
timing control IC 476.
[0258] The timing control IC 476 supplies the read control signal
to the graphics memory 474 synchronizing with a scan timing of the
organic EL panel 460 and reads the image data from the graphics
memory 474. The timing control IC 476 supplies the thus read image
data and a driving signal to the organic EL panel 460 and displays
the display image on the organic EL panel 460. The timing control
IC 476 also detects a vertically start point VS, a vertically end
point VE, a horizontally start point HS, and a horizontally end
point HE of the car picture TM displayed on the second area L2
shown in FIG. 33.
[0259] FIG. 36 is a figure showing relation between the display
image displayed on the organic EL panel 460 and not scrolled and
the memory space. The display area of the organic EL panel 460 is
constituted by 199*99 pixels. A left top position of this image
corresponds to an address (0, 0) in the memory space and a right
bottom position thereof corresponds to an address (199, 99).
[0260] The image data is written at the address in which the
display image corresponds one by one to the memory space in the
graphics memory 474 by the MPU 434 as shown in FIG. 36. The scroll
of the image in the organic EL panel 460 is performed by changing a
timing of reading the image data by the timing control IC 476. The
method of scrolling in the first area L1, the method of scrolling
in the second area L2, and the method of scrolling in the third
area L3 differ each other. The method of scrolling in the first
area L1 and in the third area L3 may be the same.
[0261] Reading the image data by the timing control IC 476 is
explained based on FIGS. 37A and 37B. Upper column shows the memory
space and lower column shows the display image. FIG. 37A shows a
procedure of reading the image data written in the memory space in
the case without scroll. The image data written in the memory space
is the same in FIG. 37A and in FIG. 37B.
[0262] The read of the image data without scroll is carried out
toward a horizontal direction one by one from the address (0, 0) S1
to the address (0, 99). Then, moving to the bottom of one line and
the image data at the address (1, 0) is read. Similarly, the image
data is sequentially read until the address (199, 99).
[0263] On the other hand, the read of the image data with scroll is
shown in FIG. 37B. In this figure, the display image is scrolled
only horizontally in the first area L1 and in the third area L3.
The display image is shifted 50 pixels rightward. In the second
area L2, the display image is scrolled not only horizontally but
vertically.
[0264] The read of the image data is started at the address (0,
50). The image data is read sequentially. When the image data at
the address (0, 99) is read, moving back to the top of the line,
image data from the address (0, 0) to
[0265] the address (0, 49) is read. Then, image data at the address
(1, 50) in a lower row is read. Similarly, the image data in the
row is sequentially read.
[0266] Next, read of the image data in the first area L1 is
completed, then read of the image data in the second area L2 is
started. In the second area L2, the car picture TM is displayed
from the left top point GS. The image data is read from the address
corresponding to the point GS. This address is referred to as the
image start address M1 for convenience sake. The image data is read
from the address M1. If the image data is read to the bottom row of
the second area L2, the image data in the top row of the second
area L2 is read. If the image data is read to the address just
before the address M1, all of the image data in the second area L2
is read.
[0267] Then, the image data in the third area L3 is started.
Similar to the display image in the first area L1, the display
image in the third area L3 is shifted 50 pixels leftward.
Therefore, read-out is started from the image data at the address
moved horizontally 50. Read of the image data in the third area L3
is carried out like read of the image data in the first area
L1.
[0268] If the size and the display position of the display image
are known when scrolling in the second area L2, it is possible to
display the display image so that the display image may not be
protruded from the organic EL panel 460. Since the MPU 434 is
writing the image data in the graphics memory 474, the address of
the start position GS of the image and the address of the end
position GE of the image are grasped by the MPU 434. For this
reason, the MPU 434 sets the read-out start address in the second
area L2 so that the image may not be protruded from the organic EL
panel 460. The scroll of the display image can be achieved by
changing the address over time.
[0269] On the other hand, if the MPU 434 does not manage the size
and the display position of the display image, the timing control
IC 476 manages the size and the display position of the display
image by detecting the image start position GS and the image end
position GE of the display image.
[0270] The MPU 434 writes the only required image data which is
corrected from the last display image to the graphics memory 474
one after another. Thereby, the MPU 434 may be unable to manage the
picture start position GS and the picture end position GE in the
second area L2. However, when the timing control IC 476 reads the
image data from the memory, the picture start position GS and the
picture end position GE of the second area L2 can be detected. The
MPU 434 can manage the display position of the image by notifying
the detected picture start position GS and the picture end position
GE to the MPU 434. Scrolling without a protrusion of the image can
be realized by setting the read-out start address of the second
area L2 to the timing control IC 476.
[0271] The procedure of detecting the picture start position GS of
the 2nd domain L2 by the timing control IC 476 and the picture end
position GE is explained. It is assumed that a non-image area is
covered with a single color as a premise. The address space of the
second area L2 is known. If the data of the color which is not a
non-image is outputted to the image data of the address in the
second area L2, the timing control IC 476 detects the minimum
address and the maximum address in horizontal and vertical for
every frame. The detected addresses may be the picture start
position GS and the picture end position GE in the second area L2.
Here, the non-image area means the area other than the car picture
TM among the second area L2.
[0272] As mentioned above, according to the fifth example,
generating of phosphor burn-in can be reduced by shifting
independently the image displayed on the display screen of the
cellular phone according to the divided area, without getting worse
a user's visibility.
[0273] These embodiments have been given solely by way of
illustration. It will be understood by those skilled in the art
that various modifications may be made to combinations of the
foregoing components and processes, and all such modifications are
also intended to fall within the scope of the present invention.
Such modifications are given below.
[0274] In this embodiment, the image shifting unit 450 which shifts
a display image is comprised in the image adjusting unit 432, the
image shifting unit 450 may be comprised in the image source input
unit 420 and the display image inputted in the organic EL driving
circuit may be changed.
[0275] In this embodiment, the above-mentioned three conditions of
the accumulated value of luminance at the time of shifting the
display image are exemplified, but not restricted with these. For
example, the difference of luminance set to the optical elements in
the odd-numbered columns and the even-numbered columns may be
accumulated until a certain time. And the difference of luminance
set to the OLEDs in the odd-numbered columns and the even-numbered
columns in the image to be displayed next may be accumulated. Then,
the display image may be changed so that the degradation of the
OLED may be averaged according to whether the accumulated value is
positive or negative. The luminance set to the OLEDs in the
odd-numbered columns and the even-numbered columns may be
accumulated until a certain time. And the luminance set to the
OLEDs in the odd-numbered columns and the even-numbered columns in
the image to be displayed next may be accumulated. Then, the
display image may be changed so that the degradation of the OLED
may be averaged according to which of the accumulated value is
greater. Here, the luminance set to the OLEDs in the even-numbered
columns and the odd-numbered columns is compared, but the luminance
set to the OLEDs in the even-numbered lines and the odd-numbered
lines may be compared.
[Effect of the Fourth Embodiment]
[0276] The deterioration of display quality of the display
apparatus can be suppressed according to the present embodiment.
Particularly, the variation of the luminance in one screen and the
deviation of the white balance can be mended. Moreover, the
phosphor burn-in of a screen can be prevented in another
viewpoint.
Fifth Embodiment
[Field of the Fifth Embodiment]
[0277] The present embodiment relates to a display apparatus, and
it particularly relates to a technology for improving a display
quality of the display apparatus.
[Related Art of the Fifth Embodiment]
[0278] Notebook type personal computers and mobile terminals are
spreading widely. A liquid crystal display is mainly used as a
display apparatus thereof. Organic EL (Electro Luminescence)
display is expected as a next-generation flat display panel. As for
the liquid crystal display, the straitness of the view angle and
the lateness of response speed still remain as a subject. On the
other hand, the organic EL display can solve the above-mentioned
subject and can achieve high luminosity and high efficiency.
[0279] As for the organic EL display, however, it can not be
avoided a change with the passage of time, that is, degradation, of
an optical element because of the characteristic thereof. A white
balance may collapse or a variation of luminance may be arisen by
continuous use, even if the white balance is adjusted at the time
of manufacture. It is known that degradation of the optical element
of the organic EL display is remarkable compared with that of the
liquid crystal display, and it is recognized that it is a big
problem in view of the quality of a product.
[0280] In the organic EL display comprised in a cellular phone
especially, a specific character or a specific character string is
continuously displayed on a specific place in many cases.
Hereafter, both of a character and a character string are also
referred to as a "character string." Generally, in consideration of
a user's visibility, such a character string is set up so that it
can be clearly distinguished from the color of the circumferences,
such as a background picture. Therefore, a remarkable difference of
advance of degradation between the optical elements of an area in
which the character is displayed and the surrounding optical
elements tends to appear.
[0281] Moreover, since a character string is displayed from the
upper part of a display screen when the character string contained
in texts such as an E-mail is displayed, advance of degradation of
an optical element differs in the upper part and a lower part of a
display screen. The variation of luminance may be arisen
thereby.
[Summary of the Fifth Embodiment]
[0282] An object of the present embodiment is to improve reduction
of display quality caused by the above-mentioned variation of the
luminance. Another object of the present embodiment is to avoid a
phosphor burn-in of a display image caused by localizing the
variation of the luminance.
[0283] An aspect of the present embodiment relates to a display
apparatus. This display apparatus is a display apparatus
comprising: an optical element; and a display changing unit which
changes display form of a text data displayed on said display
apparatus in a manner where a guessed value of degradation of each
optical element can be averaged; wherein said display changing unit
changes, when a power supply of said display apparatus is turned on
or off, the display form of the text data in a process of turning
the power on or off. Here, the text data means a character.
[0284] Here, the display apparatus means an apparatus comprising a
display screen, for example, a cellular phone, a PDA (Personal
Digital Assistant), a personal computer, and the like. An organic
light emitting diode (hereinafter, simply referred to as "OLED") as
an optical element of an organic EL display deteriorates with
passage of time as mentioned above. Cause of the deterioration is
considered a current supplied to the OLED.
[0285] As mentioned above, a specific character or a specific image
is displayed on a specific position in the display screen of the
cellular phone in many cases. It may cause the phosphor burn-in.
The degradation of the OLED can be averaged by changing a display
position, luminance, or color tone of the character and the image
displayed. Here, "average" may be a state almost equalized, and
equalization should just be the grade where a user cannot recognize
the variation of the luminance.
[0286] In the case of color display in the organic EL display, the
degradation speed of the OLEDs of R (Red), G (Green), and B (Blue)
differs since the materials thereof differ each other. Thereby,
there may be arisen a phenomenon that the display image is
displayed in a little green for example as the display is used.
Therefore, it is necessary to equalize the grade of degradation of
the OLED of each color of R, G, and B.
[0287] The change can be performed without making a user conscious
by changing the display form of the text data when the user does
not use the display apparatus. The form of the text data may be a
kind, a size, a color, a brightness of the font for example. A
color or a brightness of the background of the text data displayed
may be changed.
[0288] Further another aspect of the present embodiment also
relates to a display apparatus. This display apparatus is a display
apparatus comprising: an optical element; and a display changing
unit which changes display form of a text data displayed on said
display apparatus in a manner where a guessed value of degradation
of each optical element can be averaged; wherein said display
changing unit changes, when an application displayed on said
display apparatus is changed, the display form of the text data in
a process of the change of the application. The change of the
application may be a change an application displayed on a display
screen of a cellular phone from a web browser to an e-mail
application for example. Moreover, it is contained in the change of
the application, in a case where the frame which displays a certain
application is changed to another frame, even if the application is
performed and displayed. For example, in the case where the web
browser is displayed, for example, the change of the frame which
displays contents such as a homepage is included in the change of
the application. Moreover, in the case where E-mail software is
displayed, for example, the change from the screen for selecting
the E-mail received to the screen which displays the E-mail
actually selected is included in the change of the application.
[0289] Further another aspect of the present embodiment also
relates to a display apparatus. This display apparatus is a display
apparatus comprising: an optical element; and a display changing
unit which changes display form of a text data displayed on said
display apparatus in a manner where a guessed value of degradation
of each optical element can be averaged; wherein said display
changing unit changes, when an electric mail is displayed on said
display apparatus, the display form of the text data for every
electric mail. That is, the display form of the text data is
changed according to the electric mail displayed when received
electric mail is displayed or when the electric mail under creation
or edit is displayed.
[0290] Further another aspect of the present embodiment also
relates to a display apparatus. This display apparatus is a display
apparatus comprising an optical element, a display screen thereof
can be opened and closed, the display apparatus comprising: a
display changing unit which changes display form of a text data
displayed on said display apparatus in a manner where a guessed
value of degradation of each optical element can be averaged; and
an opening-and-closing detecting unit which detects opening or
closing of the display screen; wherein said display changing unit
changes the display form of the text data when opening and closing
of the display screen are detected by said opening-and-closing
detecting unit.
[0291] Further another aspect of the present embodiment also
relates to a display apparatus. This display apparatus is a display
apparatus comprising: an optical element; and a display changing
unit which changes display form of a text data displayed on said
display apparatus in a manner where a guessed value of degradation
of each optical element can be averaged; wherein said display
changing unit changes, while a character input means comprised in
said display apparatus is operated for input of the character, the
display form of the text data. The change of the display form of
the text data is not limited to the change mentioned above, the
color and the background color of the font may be reversed. The
brightness of these colors may be adjusted according to the guessed
value of the degradation of the optical element at the time of the
reverse.
[0292] Further another aspect of the present embodiment also
relates to a display apparatus. This display apparatus is a display
apparatus comprising: an optical element; and a display changing
unit which changes display form of a text data displayed on said
display apparatus in a manner where a guessed value of degradation
of each optical element can be averaged; wherein said display
changing unit changes, when an electric mail is displayed, the
display form of the text data to be displayed according to whether
the electric mail has already been read or has not been read yet.
For example, a kind or size of a font of the electric mail which is
already read or is not read yet when displaying the electric mail
received.
[0293] Further another aspect of the present embodiment also
relates to a display apparatus. This display apparatus is a display
apparatus comprising: an optical element; and a display changing
unit which changes display form of a text data displayed on said
display apparatus in a manner where a guessed value of degradation
of each optical element can be averaged; wherein said display
changing unit changes the display form of the text data according
to the size of the text data to be displayed when an electric mail
is displayed. For example, the size of the font is set large in the
case where the size of the text data is 10 characters, the size of
the font is set small in the case where the size of the text data
is 100 characters.
[0294] The display changing unit may change the display form of the
text data by changing a font type of the text data.
[0295] The display changing unit may shift an arbitrary character
included in the text data using a margin space which is originally
set to avoid displaying the characters touching each other.
[0296] Generally, the font does not use one line in one side of the
display area so that the font may not contact with a neighbor font,
and the line is set as the margin area. In a case of the font of
8*8 pixels, for example, only 7*7 pixels are used actually.
Thereby, each vertical and horizontal one line can be used as the
display area of the font.
[0297] Further another aspect of the present embodiment also
relates to a display apparatus. This display apparatus is a display
apparatus comprising: an optical element; and a display changing
unit which changes display form of a text data displayed on said
display apparatus in a manner where a guessed value of degradation
of each optical element can be averaged; wherein said display
changing unit sets a background color of a line in which the text
data is not inputted as an intermediate color between a display
color of the text data and an originally selected background color
when an application for inputting the text data is executed.
[0298] Further another aspect of the present embodiment also
relates to a display apparatus. This display apparatus is a display
apparatus comprising: an optical element; and a display changing
unit which changes display form of a text data displayed on said
display apparatus in a manner where a guessed value of degradation
of each optical element can be averaged; wherein said display
changing unit changes a luminance for displaying the text data
according to a display position of the text data.
[0299] Optional combinations of the aforementioned constituting
elements, and implementations of the invention in the form of
methods, apparatuses and systems may also be practiced as
additional aspects of the present invention.
[Example of the Fifth Embodiment]
[0300] In the present embodiment, a cellular phone comprising an
organic EL display in a display screen as a display apparatus is
considered. The phosphor burn-in of the organic EL display can be
reduced by changing display form of a character string displayed on
the cellular phone. The size or kind of the font of the character
string to be displayed or the color thereof is changed when a user
writes or reads an electric mail using the cellular phone. The font
used for display is also changed when the power of the cellular
phone is turned on or off.
[0301] FIGS. 38A and 38B show a display screen in which the
phosphor burn-in is arisen. In FIG. 38A, four characters "ABCD" are
displayed in an area A on the display screen. If these characters
are displayed in the area A for a long term, the four characters
"ABCD" are seen as if these characters are displayed there when an
image in which all pixels are same color is displayed, even if
these characters are not displayed. That is, the phosphor burn-in
is arisen in the area A.
[0302] When a character string is displayed on the display screen
of the cellular phone, the character string is generally displayed
on the same part in many cases. Moreover, the character string is
displayed from upper left of the display screen in many cases, and
it is not often that the character string is displayed on lower
part of the display screen. Then, the font type of the character
displayed on the display screen is changed, or the luminance of the
screen is changed according to the area of the display screen.
[0303] The condition for changing the display form of the character
string may be (1) when the power of the display apparatus is turned
on or off, (2) when the display apparatus is opened or closed in a
case where the display apparatus can be opened and closed like a
fold-down type cellular phone, (3) when changing an application,
(4) when a certain application, here, an e-mail application for
example, is executed, (5) when there is no operation from a user
for a predetermined term. In a case where the e-mail application is
executed, the display form used may be changed according to whether
the e-mail is already read or not, or the number of the characters
included in the e-mail.
[0304] FIGS. 39A and 39B are figures showing a display screen in
which a character string is displayed with two kinds of fonts
different from each other. The font displayed in FIG. 39B is thin
as a whole and inclines, compared with the font displayed in FIG.
39A. In FIG. 39A, five characters of the string are displayed on
the fourth line, on the other hand, only one character of the
string is displayed on the fourth line in FIG. 39B. An area where
the character string is displayed may be changed by changing the
font. That is, the phosphor burn-in of the display screen can be
reduced by changing the kind of the font.
[0305] FIGS. 40A and 40B are figures showing a state where the size
of the font used is changed when the number of the characters
displayed on the display screen is different.
[0306] In FIG. 40A, 52 characters of alphabet from "A" to "Z" in a
capital and small letter are displayed. On the other hand, in FIG.
40B, 26 characters of alphabet from "A" to "Z" in only capital
letter are displayed. In FIG. 40B, the number of the characters is
decreased. If the font of the same size as the font displayed in
FIG. 40A is used, the characters are displayed on only half of the
display screen. Then, the character string can be displayed on the
whole display screen by enlarging size of the font. Generally, when
displaying a text and the like, the character string is displayed
from the upper left of the display screen, and is not displayed on
the bottom of the display screen in many cases. Then, text data can
be displayed on the whole display screen by changing the size of
the font.
[0307] Thereby, the case where only a part of the display screen is
used frequently can be reduced, and the phosphor burn-in can be
reduced.
[0308] FIG. 41 is a figure showing a state where a color of an area
where a character string is not displayed is gradually changed from
a background color to a color same as the display color of the
character string. The character string is displayed from the top to
the fourth line. On the other hand, the character string is not
displayed in the fifth to seventh lines. The color tone of these
lines is gradually changed for every line so that the color may not
be changed extremely. All the lines in which the character string
is not displayed may be displayed in the same color, for example,
an intermediate color between the color of the character and the
color of the background.
[0309] FIGS. 42A and 42B are figures showing a state where a
Japanese is displayed in an area of 8*8 pixels. The pixels of the
top row and rightmost column of this area is set up as a margin
space so that neighboring characters may not be touched. This area
is also used as the display area at the time of shifting the
character. FIG. 42A shows a state before the character is shifted,
and FIG. 42B shows a state where the character string is shifted
one pixel to up and right, respectively. In the case where the
character string consists of two or more characters, a character
may be shifted one pixel to up, another right, or further another
not shifted, for example, depending on the character. The phosphor
burn-in can be reduced without spoiling display quantity
greatly.
[0310] The apparatus for realizing the above-mentioned change of
the display form of the character string and its operation are
shown hereinafter.
[0311] FIG. 43 is a block diagram showing a basic structure of an
organic EL display apparatus 510. The organic EL display apparatus
510 is constituted by an image source input unit 520, an e-mail
attribute acquiring unit 524, an open-close detecting unit 552, an
operation detecting unit 554, an organic EL driving circuit 530,
and an organic EL panel 560.
[0312] The organic EL driving circuit 530 comprises an image
adjusting unit 532 which carries out various processings to a
digital image signal inputted from the image source input unit 520,
an MPU (Micro Processing Unit) 534 which calculates when these
processings are carried out, and a DAC (Digital to Analog
Converter) unit 542 which converts the image signal carried out
processing to an analog signal. The organic EL driving circuit 430
further comprises a text detecting unit 538, a luminance changing
unit 544, and a color changing unit 546. The organic EL driving
circuit 538 further comprises a control signal generating unit
which generates various timing control signals and a memory which
functions a table when actual processing is carried out, which are
not shown in the figure.
[0313] The image adjusting unit 532 performs an offset adjusting to
adjust a brightness, a gain adjusting to adjust a contrast, and a
processing to adjust input image signal which is performed gamma
correction to voltage-emitting luminance (V-T) characteristic of
the organic EL panel.
[0314] When the display form of the character string is not
changed, three kinds of the digital signals R_in, G_in, and B_in
are inputted from the image source input unit 520 to the image
adjusting unit 532. The image adjusting unit 532 performs image
adjusting processing like the offset adjusting and the gain
adjusting. The digital signals are outputted from the DAC unit 542
as three kinds of analog signals R_out, G_out, and B_out to the
organic EL panel 560.
[0315] When the display form of the character string is changed,
the change is carried out by the structure shown below. The image
adjusting unit 532 comprises a text shifting unit 536 which shifts
the character to use an area where the character does not
originally use among pixels which constitute the font as shown in
FIG. 42.
[0316] The text detecting unit 538 detects the character string
from the inputted digital image signal. The text detecting unit 538
changes the display form of the detected character string in
collaboration with the MPU 534 as shown in FIGS. 39 and 40. The
luminance changing unit 544 changes the luminance of the character
according to a display position thereof. The luminance changing
unit 544 also changes the luminance in an area where the character
string is not inputted as shown in FIG. 41. Similarly, the color
changing unit 546 changes the color of the character and the color
of an area where the character string is not inputted.
[0317] The e-mail attribute acquiring unit 524 acquires an
attribute of each e-mail when an e-mail application is executed.
The attribute may be (1) whether the e-mail is already read or not,
(2) the number of the characters included in the e-mail and the
like.
[0318] The image source input unit 520 further comprises a text
form changing unit 522. The text form changing unit 522 changes the
display form of the character string displayed in the e-mail based
on the attribute acquired by the e-mail attribute acquiring unit
524. The change of the display form is also carried out by the text
detecting unit 538, but the change here is carried out before the
digital image signal is inputted to the organic EL driving circuit
524. The text detecting unit 538 may change the display form of the
character string based on the attribute of the e-mail acquired by
the e-mail attribute acquiring unit 524.
[0319] The open-close detecting unit 552 detects open or close of
the display screen in a case where the display screen of the
cellular phone is a fold-down type. The open-close detecting unit
552 instructs the MPU 534 to change the display form of the
character string used in the cellular phone when detecting. The
operation detecting unit 554 instructs the MPU 534 to change the
display form of the character string used in the cellular phone
when there is no operation to the cellular phone for a
predetermined term.
[0320] In terms of hardware, this structure can be realized by a
CPU, a memory and other LSIs of an arbitrary computer. In terms of
software, it is realized by memory-loaded programs or the like
having a function of controlling display, but drawn and described
here are functional blocks that are realized in cooperation with
those. Thus, it is understood by the skilled in the art that these
functional blocks can be realized in a variety of forms by hardware
only, software only or the combination thereof.
[0321] As mentioned-above, according to this embodiment, the
generation of the luminance variation in the display screen can be
reduced by changing the display form of the character string and by
changing the background color of the display screen according to
whether the character string is displayed or not. Moreover, the
phosphor burn-in of the display screen caused by the concentration
of the luminance variation can be reduced.
[0322] These embodiments have been given solely by way of
illustration. It will be understood by those skilled in the art
that various modifications may be made to combinations of the
foregoing components and processes, and all such modifications are
also intended to fall within the scope of the present
invention.
[Effect of the Fifth Embodiment]
[0323] According to this embodiment, reduction of deterioration of
the display quality caused by the luminance variation is
expectable. Moreover, reduction of the phosphor burn-in of the
display screen caused by the concentration of the luminance
variation is also expected in another view point.
[0324] Although the present invention has been described by way of
exemplary embodiments, it should be understood that many changes
and substitutions may be made by those skilled in the art without
departing from the spirit and the scope of the present invention
which is defined only by the appended claims.
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