111111
`
`1111111111111111111111111111111111111111111111111111111111111111111111111111
`US 20030156092Al
`
`(19) United States
`(12) Patent Application Publication
`Suzuki et al.
`
`(54) DISPLAY CONTROL DEVICE OF LIQUID
`CRYSTAL PANEL AND LIQUID CRYSTAL
`DISPLAY DEVICE
`
`(75)
`
`Inventors: Toshiaki Suzuki, Kawasaki (JP);
`Koichi Katagawa, Kawasaki (JP);
`Koshu Yonemura, Kawasaki (JP);
`Toshihiro Kojima, Kawasaki (JP);
`Takashi Yuda, Kawasaki (JP)
`
`Correspondence Address:
`Patrick G. Burns, Esq.
`GREER, BURNS & CRAIN, LTD.
`Suite 2500
`300 South Wacker Dr.
`Chicago, IL 60606 (US)
`
`(73) Assignee: FUJITSU DISPLAY TECHNOLO(cid:173)
`GIES CORPORATION
`
`(21) Appl. No.:
`
`10/260,364
`
`(22) Filed:
`
`Sep.30,2002
`
`(30)
`
`Foreign Application Priority Data
`
`Feb. 20, 2002
`
`(JP) ...................................... 2002-043526
`
`(10) Pub. No.: US 2003/0156092 A1
`Aug. 21, 2003
`(43) Pub. Date:
`
`Publication Classification
`
`(51)
`Int. CI? ....................................................... G09G 3/36
`(52) U.S. Cl. ................................................................ 345/98
`
`(57)
`
`ABSTRACT
`
`An operational unit determines, for subfield(s) other than a
`last subfield of a plurality of subfields constituting a single
`frame period, based on a difference determined by a data
`comparison unit, exceeded display data for setting the trans(cid:173)
`mittance of each pixel to a value exceeding a target trans(cid:173)
`mittance corresponding to image data supplied anew. The
`operational unit also determines, for the last subfield of the
`single frame period, based on the difference determined by
`the data comparison unit, target display data for setting the
`transmittance of each pixel to the target transmittance. An
`overshoot operation or operations are performed within the
`single frame period, and each pixel is set to the transmittance
`corresponding to the image data. This makes it possible to
`avoid trails occurring in moving image display and enhance
`the appearance of moving image display with no increase in
`frame rate.
`
`image data
`
`temperature
`memory unit g§_
`
`rate memory
`unit
`
`r·-----------------------------------------1 ~----·--------~
`data conversion part 1Q .. frame memory l_g!
`.
`
`32a
`first
`operational unit
`
`32b f----+-+---+---7------,
`second
`L---------1----loperational unit
`
`32c
`third
`operational unit
`ODD
`operational unit 32
`I
`i
`'--------------------------=----------- ------------------------------
`L______________________ - ---------------
`TIM
`timing control unit 14
`
`DRV
`
`source driver
`vs
`
`rate detecting
`unit
`g±
`
`temperature
`detecting unit g_g
`
`gate driver
`1§_
`
`liquid crystal panel:
`20
`
`p
`
`IPR2015-00863
`Petition for Inter Partes Review of U.S. Patent 7,202,843 - EXHIBIT 1003_Page 1
`
`

`

`~------------------------ciataconversion-parf 1 o -!
`l
`~
`.t
`.
`·l data companson un1 30
`r------- --------------------------------------------------------------
`:
`first
`32a
`:
`)..___. operational unit -
`~: DIF
`!
`:
`j
`
`image data
`
`temperature
`memory unit 26
`
`1
`
`rate memory
`unit
`
`!
`1---- I
`28 I
`!
`
`£'
`· OSD
`
`.. i
`: operational unit 32
`
`32b
`second
`~ operational unit
`32c -+--
`.-- third
`operational unit
`v--- 0 DD
`,
`1
`: __________________________ :-::-__________ --- __________________________ _,
`L----------------------~-~---------------~-
`TIM_
`~
`timing control unit 14
`DRV
`'
`source driver
`vs
`
`I
`
`I
`
`-
`
`I
`
`I
`
`!-t~~m~~e~ory_1_2l
`+
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`1 1
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`. un1t
`12a
`I
`I
`-----
`! !
`I
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`'
`! ! first memory
`I
`I unit
`12b
`' L _____________ :
`! !
`-----
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`
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`~
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`~ .... ... 0 =
`
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`
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`0'1 c
`'0
`N
`>
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`
`gate driver
`18
`
`I
`
`!§_
`
`rate detecting
`unit
`24
`
`temperature
`detecting unit 22
`
`I I I
`TI
`1
`liquid crystal panel:
`'
`20
`: ~p
`f
`l i l
`
`L.....J......l_
`
`Fig. 1
`
`Page 2
`
`

`

`FL 1
`
`_
`
`SF1
`
`SF2
`
`'
`:,
`
`SF1
`
`SF2
`
`FL2
`
`transmittance 1
`
`'
`(d)
`-,#.------------.----- ~
`target value
`' '
`
`81
`
`'
`r - - - - - - '
`'
`
`time----
`
`'
`1f
`
`(a)
`
`' '
`applied voltage VS 1
`'
`'
`f--- targetvalue( ~)-,---------------": target value(+)
`:
`1......-------------------"j-----------
`f - - - - - - - - - . , '
`
`(display data)
`
`Vcom !
`
`~-
`:
`
`I
`I
`tarQet "vaiue{·y-c·
`
`(e)
`
`(c)
`
`~------
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`:
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`Fig. 2
`
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`~
`
`·-
`
`Page 3
`
`

`

`L DIF
`1 operation 1
`
`- _...
`
`.
`
`input data
`
`image data
`(n frame)
`
`image data
`(n+ 1 frame)
`
`(30) H.-. OSD
`.(32a) ····-·-·--·-··············-,
`operat1on
`:
`image data~ I-i-
`l
`12
`i
`(nframe)
`-----!"~~·
`(32
`b) ~difference data
`SUM (32c) ODDn
`DIF
`._. operation
`operation 2
`:
`(n frame)
`: 4
`_1gQ
`-·
`:
`12 :
`'
`~-------------------~-------
`L DIF
`(30) H~ OSD
`. (32a) •.......................... ,
`--T _... operation 1
`operation
`.
`12a :
`L~~~~~~------H- 1mage data -~
`(n+ 1 frame)
`
`image data
`(n- 1 frame)
`
`OSDn
`
`display data
`(to timing control
`circuit 14)
`r ; - · · - · - - - \
`subfield SF1
`(n frame)
`
`4
`
`subfield SF2
`(n frame)
`
`subfield SF1
`(n+ 1 frame)
`
`OSDn+ 1
`
`4
`
`+1
`------... 0 DDn
`(32b) f.++. difference data
`DIF
`SUM (32c)
`(
`subfield SF2
`(n+ 1 frame~ ._. operation
`operation 2
`(n+ 1 frame)
`12
`'
`~----------------------~-j
`............ .,.
`
`I
`
`:
`
`Fig. 3
`
`'t:l
`
`I")
`
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`~ = .....
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`.... 0 =
`~
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`~
`~
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`'JJ. =(cid:173)~
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`
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`0 ......,
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`
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`'JJ.
`N c
`@
`c
`'"""' Ul
`0'1 c
`'0
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`>
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`
`Page 4
`
`

`

`image data
`
`
`temperatur e
`memory un
`it 26
`-
`
`rate memo
`ry 281
`unit
`
`-
`,.------- --------------------------------------------------------------
`' '
`first
`34a
`' ' ' ~
`operational unit 1--
`l
`'
`' '
`r
`DIF
`
`34b
`second
`operational unit
`
`,-----------------------dataconversion -pa-rt-1 o-B -! !f7~m~~e~ory_1_21
`-
`:
`1
`'
`I
`I
`data memory
`I
`I unit
`12a
`'
`'
`I
`I
`-
`'
`I
`I
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`'
`I
`I
`i j
`'
`. '
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`. '
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`L__ ___________
`__I
`
`I
`
`gate driver
`
`_@
`
`I I I I
`
`'
`'
`
`fJ
`1GT.
`R=h
`
`I I II I
`
`source driver
`vs
`
`1§
`
`--------------~
`
`I I I
`
`L-L-L-
`
`temperature 22
`detecting unit
`
`I I r
`liquid crystal panel:
`IT vP
`20
`' '
`_r 1 r 1
`---------------
`I Tl I I I
`
`Fig. 4
`
`! q data comparison unit 30
`
`•
`
`OSD
`
`I
`'
`I
`I
`'
`I
`I
`'
`I
`'
`'
`'
`'
`I
`34c-+---
`....-- third
`-
`'
`I
`'
`operational unit
`'
`'
`I
`'
`operational unit 34
`-----ODD
`:
`'
`-------------------------------------- --- --------------------------~
`I
`! ________________ __ __ __ __ -- ---------------r--
`TIM
`timing control unit 148
`DRV
`
`1
`
`first memory
`unit
`12b
`
`rate detecting
`unit
`2L
`
`I")
`
`~ .....
`
`I")
`
`~ .....
`
`"'C
`~ .....
`~ = .....
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`.... 0 =
`~
`0' -....
`.... 0 =
`~
`~
`N
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`N c
`8
`'JJ. =(cid:173)~
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`
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`N c
`@
`c
`"""" Ul
`0'1 c
`'0
`N
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`
`Page 5
`
`

`

`frame
`
`frame
`
`SF1
`
`SF2
`
`SF1
`
`SF2
`
`transmittance 1
`
`(d)
`'
`--~---,---------- ~-~~==~
`target value
`
`____ ,.. __________ _
`target value
`
`'
`
`(h)
`
`'
`2f
`
`(a)
`.
`
`'
`
`applied voltage VS 1
`
`(display data)
`
`- - - - - - -
`
`time----
`
`'
`1f
`
`' '
`'
`---~ar_g_§~_y?lu~l_-t:L _______ j
`
`'
`
`I
`
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`
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`'
`'
`'
`'
`target value(+)
`' ----------------------
`
`I
`
`Vcom
`
`'
`'
`
`(c)
`'
`'
`'
`:-------~----------------------~
`:
`target value(-)
`:
`
`target value(-)
`f - - - - - - - - ----------------------
`(g)
`
`Fig. 5
`
`'t:l
`
`I")
`
`~ .....
`
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`~ = .....
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`Page 6
`
`

`

`I")
`
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`
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`~
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`
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`
`~-----------------------datacoriversion -part- 1 oc -! !-f~~m~~e~ory-12!
`-,
`~
`i
`.
`'t
`.
`data companson un1 30
`!
`I
`~------- --------------------------------------------------------------:
`:
`i
`i
`first
`36a
`i
`! ~~ operational unit f-
`\
`: DIF
`:
`i
`;
`'
`:
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`:
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`
`--~
`
`I
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`a~ a memory
`, , un1t
`1 1
`12a
`! !
`I
`I
`! !
`
`I
`
`I
`
`~
`j_g_c
`second
`memory unit
`
`1
`
`36d
`fourth
`operational unit
`
`36e
`fifth
`r- operational unit
`
`l
`
`J
`
`gate driver
`
`.1.§. fJ1
`
`timing control unit
`DRV
`source driver
`vs
`liquid crystal panel
`Fig. 6
`
`L.__J ra~e detecting
`unrt
`24
`
`1§ l
`l temperature 22
`
`gQ
`
`detecting unit
`
`~
`OSD1
`
`~
`
`0802/
`
`image data
`
`j
`
`-
`
`·1
`
`
`
`I
`
`I
`
`temperature
`memory unit 26
`----------=-~
`
`rate memory
`unit
`
`;
`j
`:
`I
`:
`I
`i
`ru!l
`~
`~
`secon~
`;
`36?
`i
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`operational umt
`. ~ ! ! first memory
`!
`third
`j
`! ! unit
`.
`!
`:
`ODD- 1 __ 1---r- op~rat1onal
`;
`12b
`36c
`unit
`: operational un1t 36
`j
`1
`-
`1 1
`L __ :=_-_--.::.==~~~---~----.::.==~~~---~---~=~ ~~ --~ --~=~~~---~---~=~-.--_! L_ __________ _
`14C l
`r
`TIM
`
`Page 7
`
`

`

`SF1
`
`FL 1
`
`SF2
`
`FL2
`- - - - - - - - - - - - - - - ,
`'
`:_ SF1 _:_ SF2 _;_ SF3 _:
`
`~·
`
`SF3
`
`transmittance 1
`
`83
`
`~target value
`
`time
`
`1f
`
`'
`2f
`
`applied voltage vsf
`(display data) I
`
`1-------•-!ar_~~ ~alue(+)
`
`1-------~--------1---------7-- target value(+)
`
`I
`
`Vcom r , -------+--------~------~------~-------+--------r-~
`
`o
`
`I
`
`~------~------
`
`, --target value(-)
`
`(b)
`
`o
`
`I
`
`:------:--targetvalue()-:
`
`I
`I
`
`I
`'
`
`I
`
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`
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`
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`
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`
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`~ = .....
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`.... 0 =
`~
`0' -....
`.... 0 =
`~
`~
`N
`'"""' ~
`N c
`8
`'JJ. =(cid:173)~
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`-..J
`0 .....,
`'0
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`Page 8
`
`

`

`.
`1nput data
`;image data \ ~ DIF
`. (30)
`T-... operation 1
`(n frame)
`
`..-. OSD (3Ga)
`operation
`
`I
`
`image data
`(n- 1lframe)
`
`12a
`
`·--------------------------------, OSV1 n
`!
`12
`: I image data
`l (n frame)
`•
`(3Gd) :
`l.L
`H'
`.
`DIF
`SUM (3Ge)
`operation 3 :
`difference data
`• operation
`:
`(n frame)
`12c 1 :
`: 4 ....
`(3Gb) :
`I!
`~DIF
`H: difference data
`12b ftr+ SUM (3Gc}
`operation 2 :
`(n frame)
`!--------------------------------~ 4~ operation
`1
`
`L
`;·--------------------------1·2--]
`T operation 1 ~ operation
`' I image data
`:
`-l
`IDIF
`(n+1 frame) 12a ;
`(3Gd)
`operation 3 LLJ difference data
`I
`I: -l (n+ 1 frame) 12c 1
`(3Gb)
`.
`-U difference data
`l
`.
`DIF
`operat1on 2 ! ~l (n+ 1 frame) 12b 1
`SUM (3Gc)
`!---------------~~~~~~~---------- H+ operation
`,
`'
`
`DIF
`
`(30)
`
`OSD (3Ga)
`
`image data
`(n+ 1 frame)
`
`L+J
`
`Fig. 8
`
`OSV1 n+ 1
`
`SUM (3Ge)
`operation
`4~
`
`display data
`(to timing control
`circuit 14)
`I
`
`\
`
`subfield SF1
`(n frame)
`
`ODDn L subfield SF2
`
`(n frame)
`
`subfield SF3
`1
`(n frame)
`OS~n
`subfield SF1
`(n+ 1 frame)
`
`OSV2n+1
`
`(
`
`subfield SF2
`(n+ 1 frame)
`
`subfield SF3
`(n+ 1 frame)
`(
`00Dn+1
`
`I")
`
`~ ......
`
`I")
`
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`
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`.... 0 =
`~
`0' -....
`.... 0 =
`~
`~
`N
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`N c
`8
`'JJ. =(cid:173)~
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`00
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`
`Page 9
`
`

`

`transmittance 1
`
`FL 1
`
`SF1
`
`SF2
`
`FL2
`
`SF1
`
`SF2
`
`'
`:
`
`'
`
`A
`
`target value
`
`,B
`'
`
`~------·
`
`target value
`
`time----
`
`'
`1f
`
`'
`
`2f
`
`'
`
`'
`[
`
`target value(+)
`
`j
`
`applied voltage VS t
`(display data) I
`
`f--targetvalue(+TI---------------i
`
`~-------------~---------------~
`
`:
`
`I
`
`;
`
`'
`'
`Vcom ~: -------~-------~--------,_-------------~--
`,
`
`' '
`L_ _ _!~rg_et _va!ue_(j_-1------------l
`
`~-------------~---------~
`!
`target value(-)
`'
`
`i overshoot operation; normal operation
`
`! overshoot operation normal operation
`
`Fig. 9
`
`I")
`
`~ .....
`
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`
`Page 10
`
`

`

`US 2003/0156092 A1
`
`Aug. 21,2003
`
`1
`
`DISPLAY CONTROL DEVICE OF LIQUID
`CRYSTAL PANEL AND LIQUID CRYSTAL
`DISPLAY DEVICE
`
`BACKGROUND OF THE INVENTION
`
`[0001] 1. Field of the Invention
`
`[0002] The present invention relates to a display control
`device of a liquid crystal panel for controlling display data
`to be displayed on the liquid crystal panel, and a liquid
`crystal display device.
`
`[0003] 2. Description of the Related Art
`
`[0004] Liquid crystal display devices are low in power
`consumption and compact in size, and thus are widely
`adopted in personal computers, television sets, and so on. In
`a liquid crystal display device, an electric field applied to
`each liquid crystal cell (pixel) of the liquid crystal panel is
`adjusted to change the transmittance of the liquid crystal cell
`for image display. Liquid crystal cells vary in transmittance
`relatively slowly. Consequently, in displaying moving
`images in particular, blurs in which data of previous frames
`appears overlapped (image trails) tend to occur. This phe(cid:173)
`nomenon is unique to liquid crystal display devices, not seen
`in CRTs (Cathode Ray Tubes).
`
`[0005] To reduce trails and bring the moving image dis(cid:173)
`play performance close to that of CRTs, there has been
`developed a technology called an impulse drive system
`which imitates the waveforms of applied voltages in CRTs.
`In addition, even in the case of a conventional hold drive
`system, techniques named as an overdrive method and an
`overshoot method have been developed for the sake of
`improved moving image display performance. Here, the
`hold drive system refers to a technology in which signals
`corresponding to the same image data are output to the liquid
`crystal cells over a period of one frame.
`
`[0006] An overview of the overdrive method and over(cid:173)
`shoot method has been disclosed, for example, in FIG. 3 of
`Japanese Unexamined Patent Application Publication No.
`2001-125067. The overdrive method is a technique for
`writing more emphasized data signals than the data signals
`corresponding to pixel data for actual display, to the liquid
`crystal cells (overdrive) so that the liquid crystal cells reach
`their target values in transmittance within a single frame
`period. The overshoot system is a technique for emphasizing
`the data signals further so that the liquid crystal cells change
`in transmittance to exceed their target values within a single
`frame period (overshoot), and for restoring the transmit(cid:173)
`tances to the target values in the next one frame period.
`
`[0007]
`In the foregoing overshoot method, greater empha(cid:173)
`sis on the data signals accelerate the changes of transmit(cid:173)
`tance (pixel response) with an improvement in the moving
`image display performance. The more the data signals are
`emphasized, however, the greater the differences between
`the target transmittances corresponding to the input image
`data and the emphasized transmittances become. This results
`in a higher propensity to new trails, sometimes deteriorating
`the appearance of so-called moving image display. The trails
`resulting from overshoot occur depending on the display
`pattern. That is, when the overshoot method is employed, it
`is impossible to enhance the appearance of moving image
`display in all display patterns.
`
`SUMMARY OF THE INVENTION
`
`[0008]
`It is an object of the present invention to improve
`the moving image display performance of a liquid crystal
`display device. In particular, the improvement in the moving
`image display performance is intended of a liquid crystal
`panel for hold drive.
`
`[0009] According to one of the aspects of the present
`invention, a data memory unit stores image data to be
`supplied correspondingly to each single frame period for
`which a single frame of a liquid crystal panel is displayed.
`A data comparison unit determines, on each pixel of the
`liquid crystal panel, a difference between image data sup(cid:173)
`plied anew and image data of a frame immediately preced(cid:173)
`ing and stored in the data memory unit.
`
`[0010] A timing control unit generates timing signals
`synchronizing with respective subfields. The timing control
`unit also receives display data from an operational unit in
`succession, and outputs driving signals according to the
`received display data in synchronization with the timing
`signals.
`
`[0011] The operational unit determines, for subfield(s) of
`a plurality of sub fields other than a last sub field, based on the
`difference determined by the data comparison unit, exceeded
`display data for setting the transmittance of each pixel to a
`value exceeding a target transmittance corresponding to
`image data supplied anew, the plurality of sub fields consti(cid:173)
`tuting the single frame period. That is, an overshoot opera(cid:173)
`tion or operations are performed in the subfields except the
`last subfield. Then, transmittance of each pixel changes to
`the transmittance which allows the supplied image data to be
`emphasized, whereby a displayed image will be more
`emphasized than the supplied image data.
`
`[0012] The operational unit also determines, for the last
`subfield of the single frame period, based on the difference
`determined by the data comparison unit, target display data
`for setting the transmittance of each pixel to the target
`transmittance. Consequently, in the last subfield, the trans(cid:173)
`mittance of each pixel changes to the transmittance corre(cid:173)
`sponding to the supplied image data.
`
`[0013] Since an overshoot operation or operations are
`performed within a single frame period and the transmit(cid:173)
`tance of each pixel is set to the transmittance corresponding
`to the image data, it is possible to avoid trails in moving
`image display. In particular, trails resulting from overshoot
`operations can be avoided. In other words, overshoot opera(cid:173)
`tions causing no trail can be made without increasing the
`frame rate (at the same frame rates as heretofore).
`
`[0014] Since the transmittance of each pixel changes to its
`target value within a single frame period, it is possible to
`enhance the appearance of moving image display in any
`display pattern and improve the moving image display
`performance.
`
`[0015] According to another aspect of the present inven(cid:173)
`tion, the target display data which the operational unit
`determines for the last subfield corresponds to an exceeded
`applied voltage. The exceeded applied voltage exceeds a
`target applied voltage to be applied to the liquid crystal panel
`so as to set each pixel to the target transmittance. That is, an
`overdrive operation is performed in the last subfield. The
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`transmittance of each pixel can thus be changed to the
`transmittance corresponding to the image data in a single
`frame period with reliability.
`[0016] According to another aspect of the present inven(cid:173)
`tion, the display data for use in the last subfield is held in a
`first memory unit so that the operational unit need not hold
`the display data. This can simplify the circuits of the
`operational unit. In addition, holding the display data in the
`form of differences can reduce the amount of data to be held.
`As a result, the first memory unit can be made smaller in
`memory capacity.
`[0017] According to an other aspect of the present inven(cid:173)
`tion, the display data for use in the intermediate subfield(s)
`exclusive of the first and last subfields is held in a second
`memory unit so that the operational unit need not hold the
`display data. This can simplify the circuits of the operational
`unit. In addition, holding the display data in the form of
`differences can reduce the amount of data to be held. As a
`result, the second memory unit can be made smaller in
`memory capacity.
`[0018] According to another aspect of the present inven(cid:173)
`tion, the operational unit generates the exceeded display data
`and the target display data which allow an average of
`transmittance in the single frame period to be substantially
`equal to the target transmittance. In other words, the
`exceeded display data and the target display data are gen(cid:173)
`erated so as to make the time integral of the actual trans(cid:173)
`mittance and the time integral of the target value of the
`transmittance equal to each other. Adjusting the average of
`the transmittance in a single frame period to the target value
`can achieve constant hues in displaying moving image data,
`resulting in improved display properties of moving images.
`[0019] According to another aspect of the present inven(cid:173)
`tion, a maximum value of the target transmittance is set to
`be smaller than a transmittance corresponding to a maxi(cid:173)
`mum value of the exceeded display data which the opera(cid:173)
`tional unit is able to output. On this account, image data
`corresponding to the maximum transmittance can be dis(cid:173)
`played with no differences in luminance between moving
`images and still images. Consequently, even if an overshoot
`operation or operations are performed in a single frame
`period and the pixels are changed between target values in
`transmittance, it is possible to eliminate differences in dis(cid:173)
`play properties between still images and moving images.
`[0020] According to another aspect of the present inven(cid:173)
`tion, lengths of periods of the sub fields are set to be equal to
`each other. This allows the operational unit and the timing
`control unit to operate at the same timing in every subfield.
`The operational unit and the timing control unit can thus be
`simplified in circuitry.
`[0021] According to another aspect of the present inven(cid:173)
`tion, a length of the period of the first sub field of the single
`frame period is set to be shorter than lengths of the periods
`of the rest of the sub fields. The liquid crystal cells can thus
`make quick changes in transmittance toward their target
`values during the first subfield after frame switching. Con(cid:173)
`sequently, moving image data and still image data can be
`displayed at the same hues with improved display proper(cid:173)
`ties.
`[0022] According to another aspect of the present inven(cid:173)
`tion, the display control device of a liquid crystal panel
`
`comprises a temperature detecting unit for detecting an
`ambient temperature of the liquid crystal panel, and a
`temperature memory unit. The temperature memory unit
`contains temperature correcting values corresponding to
`individual ambient temperatures to be detected by the tem(cid:173)
`perature detecting unit.
`
`[0023] First and second operational units correct the
`exceeded display data and the target display data according
`to the temperature correcting values which are output from
`the temperature memory unit in response to the ambient
`temperature detected by the temperature detecting unit.
`Consequently, optimum applied voltages can be supplied to
`the liquid crystal panel all the time regardless of changes in
`the environment, improving the display quality of the liquid
`crystal panel.
`
`[0024] According to another aspect of the present inven(cid:173)
`tion, the display control device of a liquid crystal panel
`comprises a rate detecting unit for detecting a frame rate,
`which is the single frame period, and a rate memory unit.
`The rate memory unit contains rate correcting values cor(cid:173)
`responding to frame rates to be detected by the rate detecting
`unit.
`
`[0025] The first and second operational units correct the
`exceeded display data and the target display data according
`to the rate correcting values which are output from the rate
`memory unit corresponding to the frame rate detected by the
`rate detecting unit. Consequently, optimum applied voltages
`can be supplied to the liquid crystal panel all the time
`regardless of frame rate changes, improving the display
`quality of the liquid crystal panel.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`[0026] The nature, principle, and utility of the invention
`will become more apparent from the following detailed
`description when read in conjunction with the accompany(cid:173)
`ing drawings in which like parts are designated by identical
`reference numbers, in which:
`
`[0027] FIG. 1 is a block diagram showing a first embodi(cid:173)
`ment of the present invention;
`
`[0028] FIG. 2 is a timing chart showing how data is
`written to a pixel in the operation of the first embodiment;
`
`[0029] FIG. 3 is an explanatory diagram showing an
`overview of operation of the data conversion part in FIG. 1;
`
`[0030] FIG. 4 is a block diagram showing a second
`embodiment of the present invention;
`
`[0031] FIG. 5 is a timing chart showing how data is
`written to a pixel in the operation of the second embodiment;
`
`[0032] FIG. 6 is a block diagram showing a third embodi(cid:173)
`ment of the present invention;
`
`[0033] FIG. 7 is a timing chart showing how data is
`written to a pixel in the operation of the third embodiment;
`
`[0034] FIG. 8 is an explanatory diagram showing an
`overview of operation of the data conversion part in FIG. 6;
`and
`
`[0035] FIG. 9 is a timing chart showing another example
`of driving in the last subfields.
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`DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`
`[0036] Hereinafter, embodiments of the present invention
`will be described with reference to the drawings.
`
`[0037] FIG. 1 shows a first embodiment of the display
`control device of a liquid crystal panel and the liquid crystal
`display device according to the present invention.
`
`[0038] The liquid crystal display device comprises a data
`conversion part 10, a frame memory 12, a timing control unit
`14, a source driver 16, a gate driver 18, a liquid crystal panel
`20, a temperature detecting unit 22, a rate detecting unit 22,
`a temperature memory unit 26, and a rate memory unit 28.
`The data conversion part 10, frame memory 12, timing
`control unit 14, source driver 16, gate driver 18, temperature
`detecting unit 22, rate detecting unit 24, temperature
`memory unit 26, and rate memory unit 28 function as a
`display control device for displaying images on the liquid
`crystal panel.
`
`[0039] The liquid crystal display device of this embodi(cid:173)
`ment operates on hold drive. That is, data signals corre(cid:173)
`sponding to the same image data are supplied to the liquid
`crystal cells over a period of one frame (16.6 ms) for
`displaying a single frame of the liquid crystal panel. Besides,
`each single frame period is divided into two subfields SF1
`and SF2 (8.3 ms each) by the timing control unit 14.
`
`[0040] The data conversion part 10 is formed as an ASIC
`(Application Specific I C), and has a data comparison unit 30
`and an operational unit 32. The data comparison unit 30
`compares image data supplied anew and image data stored
`last time in a data memory unit 12a of the frame memory 12
`frame by frame, and outputs the difference in data as a
`difference signal DIF pixel by pixel. After the comparison by
`the data comparison unit 30, the data memory unit 12a is
`overwritten with the image data supplied anew.
`
`[0041] The operational unit 32 includes a first operational
`unit 32a, a second operational unit 32b, and a third opera(cid:173)
`tional unit 32c. The first operational unit 32a generates
`display data for the subfield SFl. The second and third
`operational units 32b and 32c generate display data for the
`subfield SF2.
`
`[0042] The first operational unit 32a determines, simulta(cid:173)
`neously with the start of the sub field SF1, an overshoot value
`pixel by pixel based on the difference signal DIF from the
`data comparison unit 30, and outputs the determined value
`as display data OSD. Here, the overshoot refers to the
`driving method for displaying supplied image data with
`emphasis. That is, the display data OSD exceeds display data
`for setting the transmittances of the liquid crystal cells to a
`value greater or smaller than the transmittances correspond(cid:173)
`ing to the image data (target transmittances).
`
`[0043] The second operational unit 32b initially deter(cid:173)
`mines an overdrive value pixel by pixel based on the
`difference signal DIF from the data comparison unit 30.
`Here, the overdrive refers to the driving method for chang(cid:173)
`ing the transmittances of the liquid crystal cells to target
`transmittances corresponding to the image data in a short
`time. Here, applied voltages to be supplied to the liquid
`crystal cells are slightly higher or lower than the applied
`voltages VS corresponding to the target transmittances (tar(cid:173)
`get applied voltages). That is, display data ODD is target
`
`display data for setting the applied voltages VS to a value
`greater or smaller than the target applied voltages corre(cid:173)
`sponding to the image data so that the transmittances of the
`liquid crystal cells become the target transmittances.
`
`[0044] The second operational unit 32b determines differ(cid:173)
`ences between the overdrive values determined and the
`target values corresponding to image data supplied anew,
`and writes the differences determined to a first memory unit
`12b of the frame memory 12 as difference data. The third
`operational unit 32c restores, simultaneously with the start
`of the subfield SF2, the overdrive values for use in the
`sub field SF2 from the image data written to the data memory
`unit 12a after the comparison by the data comparison unit 30
`and the difference data stored in the first memory unit 12b,
`and outputs the resultants as the display data ODD (target
`display data).
`
`In this way, the image information for use in the
`[0045]
`subfield SF2 is held in the first memory unit 12b so that the
`operational unit 32 need not hold the image information. The
`operational unit 32 is thus simplified in circuitry. Moreover,
`holding the image information in the form of differences can
`reduce the amount of information to be held. Consequently,
`the first memory unit 12b can be made smaller in memory
`capacity.
`
`[0046] The timing control unit 14 successively receives
`the display data OSD and ODD from the first operational
`unit 32a and the third operational unit 32c, respectively, and
`outputs these display data OSD and ODD to the source
`driver 16 as driving signals DRY. The timing control unit 14
`also generates a plurality of timing signals TIM for operating
`the source driver 16 and the gate driver 18 for the subfields
`SF1 and SF2, respectively.
`
`[0047] The source driver 16 generates, according to the
`driving signals DRY from the timing control unit 14, the
`applied voltages VS to be supplied to pixels P (liquid crystal
`cells) of the liquid crystal panel in synchronization with the
`timing signals TIM. The gate driver 18 generates gate
`signals GT for selecting pixels P of the liquid crystal panel
`in synchronization with the timing signals TIM. The liquid
`crystal panel20 has a plurality of pixels P which are formed
`in a matrix.
`
`[0048] The temperature detecting unit 22 detects the ambi(cid:173)
`ent temperature of the liquid crystal panel20 and outputs the
`detected temperature to the data conversion part 10. The rate
`detecting unit 24 detects the frame rate (vertical synchro(cid:173)
`nizing signal), which is the period where a single frame of
`the liquid crystal panel 20 is displayed, and outputs the
`detected frame rate to the data conversion part 10.
`
`[0049] The temperature memory unit 26 is formed in a
`predetermined area of a not-shown ROM (Read Only
`Memory), and contains temperature correcting values cor(cid:173)
`responding to individual ambient temperatures of the liquid
`crystal panel20. For example, the temperature memory unit
`26 is provided with a temperature correcting value table. The
`operational unit 32 reads a temperature correcting value
`corresponding to the result of detection of the temperature
`detecting unit 22 from the temperature memory unit 26, and
`corrects the display data OSD and ODD according to the
`ambient temperature of the liquid crystal panel 20.
`
`[0050] The rate memory unit 28 is formed in a predeter(cid:173)
`mined area of a not-shown ROM, and contains rate correct-
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`ing values corresponding to individual