20080523_SID_71-1_Wenchih

Displaying Your VisionDisplaying Your Vision

SID2008.05.23 71.1 SID2008.05.23 71.1 W.C.TaiW.C.Tai 1

SID2008 71.1:Field Sequential Color LCD-TV Using

Multi-Area Control AlgorithmWen-Chih Tai, Chi-Chung Tsai, Shian-Jun

Chiou, Chih-Ping Su, Huang-Min Chen, Chia-Lin Liu and Chi-Neng Mo

TFT-LCD R&D Center, Chunghwa Picture Tubes, Ltd. 1127, Heping Rd., Bade City, Taoyuan, Taiwan, 334, R.O.C

e-mail. [email protected]. + 886-3-3773159



Outline

1. Introduction– Color-filter vs. Color-filter-less

– Color Sequential concept

2. New Algorithm– Multi-Area Control algorithm

(MAC)– Color Local Dimming

Sequential algorithm (CLDS)

3. Prototype – 32-inch OCB LCD TV – 15.4-inch TN Notebook

4. Conclusion



IntroductionColor-filter vs. Color-filter-less

LCD Standard Structure Color FilterLCD Standard Structure Color Filter

Remove Color Filter

• Color Filter– R G B sub-pixel to display color – Spatial additive color mixing– obstruct most of light (according

to their different wave lengths)• Advantage of no color filter

– Higher optical efficiency– Low Power Consumption– Raise the manufacture yield rate– Reduce the cost of the panel– Sunlight readable

• display a color image– The theorem of visual residue– display a color image by turning

on light sources Red, Green and Blue sequentially within a frame periods



Introductioncolor sequential concept

• LCD color-filter-less panel must combine with a backlight that has 3 separate alternating lightsources

• the visual residue of human’s eyes is about 1/60 (one sixtieth) second

• Increase the field frequency above 180 Hz to display the full color image

• Waited the LC transfer to position, then light on

60Hz 180Hz

Temporal color mixing



Basic Algorithm• one field time is 1/3(one third) frame time 5.57 ms,• the response of LC and the flash of the backlight must be completed. • LCD scanning data must be shorter than 4.28 ms, • the LED flashing time is about 1.28 ms.• In this case, due to the short flash time the LED number must be

increase, If the brightness of the module want to achieve market specification with the slower LC response time

RGB LED Backlight

TFTscanning

tTFT

tLC

tBL

1/3 f

R G B

1.28ms 1.28ms 0.5ms

Timing chart in the color sequential LCD with TFT addressing



MAC Algorithm(Multi-Area Control)

• if 3 gate IC were applied to the panel.

• Panel and backlight is divided into three areas

• Control the timing of the LCD with 180 Hzfield rate

• the backlight show 9 flashing pattern in one frame time

• LCD address time is reduced to one third of the whole panel

Fig. 1 MAC algorithm of LED light on time sequential



MAC Algorithm – time chart• the panel and

backlight were divided into three area I, II, III

• the LCD address time can be reduced to 1/3(one third) from 4.28 ms to 1.18 ms

• the LED flash time was increased from 1.28 ms to 3.5 ms

• 2nd area was the same with 1st but delay 1.85 ms

• 3rd area was the same with 1st but delay 3.7 ms

RGB LED BL Area I

TFT LCDArea I

1/3f(5.56ms)

tLC

R G BtLC

tLC

tLC

R G BtLC

tLC

tLC

R G BtLC

tLC

RGB LED BL Area II

TFT LCDArea II

RGB LED BL Area III

TFT LCDArea III

f(16.67ms)

tTFT tTFT tTFT

tTFT tTFT tTFT

tTFTtTFTtTFT

tLED tLED tLED

tLED tLED tLED tLED

tLED tLED tLED tLED

RtTFT

RG

B

B

B

B

B

R

R

G

G

3.5ms 3.5ms3.5ms

1.18ms

Timing chart in the MAC LCD with TFT addressing



CLDS Algorithm(Color Local Dimming Sequential)

• Determinate the amount of dimming areas

• for example 4 x 6 area• LCD is portioned into several

areas according to the Backlight unit

• Raster scan is used to scan the picture pixel by pixel from the left-top to the right-bottom.

• After the maximum or averagevalue is computed then

• A critical value can be found from a signal area, or several area and set the intensity of backlight

Fig. 2 MAC algorithm combined with CLDS method



X8 X

8

X8

X8

X8

X8

Prototype32-inch OCB LCD TV – Panel Driver Circuit

• Use the mass product standard IC

• FSC does not need sub-pixel

• Connect R G B Sub-pixel of standard panel into the same I/O line

•FSC increase 3 times I/O speed but connect R G B into one I/O decrease 3 times I/O speed•Maintain the same I/O speedand use the standard panel MASK



Prototype32-inch OCB LCD TV - Optical Mechanism Layout

• The basic optical films structure of the module is the same with the standard display.

• Under the LCD panel – diffuse film, – brightness enhance film

(BEF), – diffuse film, – diffuse plate, – LEDs and reflective layer

Fig. 4 32”TV backlight structure



Prototype32-inch OCB LCD TV - Backlight Mechanism Layout

• the advantage of LEDs– Low power consumption– Smaller form factor– Wide color gamut

• 24 x 48 LEDs layout backlight source

• low power RGB chips set of tri-color in one LEDs

• reduce the flash duty and overdrive the power supplied current,

• high-speed flashing • the LED chip can be emitted

more light flashing energy and more light efficient of low power LED chip can be achieve. Fig. 5 Backlight module with the low power

RGB chips set of tri-color in one LED



Prototype32-inch OCB LCD TV - The Liquid Crystal Mode

• The FSC method requires – fast scanning driver, – fast response of the display

device and – fast switching of the RGB

light sources.• the OCB mode was adopted

for its fast response time and uniform alignment in FSC display

• The average gray to grayresponse time of OCB mode is 1.4 ms and on/off 3 to 4 ms.

• All state transition below 3.5 ms

255223

191159

12795

6331

0

255

223

191

159127

9563

310

0

2

4

6

8

10

12

14

16

Time (m

s)

Rising Time

Falling Time

Fig. 9 OCB LCD-TV response time



Prototype32-inch OCB LCD TV - Basic FSC Algorithm

• display image by basic field sequential method

• bottom Image of the display with wrong mixed color

• There is not enough time to wait the LC to transfer to the required position

• Brightness : 350 nits

Wrong Mixed ColorWrong Mixed Color

The color filterless 32-inch TFT TV by using basic sequential principle



Prototype32-inch OCB LCD TV - MAC Algorithm

• The 32-inch color filter less liquid crystal module with the MAC Algorithm

• Brightness : 500 nits– (max 900 nits)

• the color gamut 114.6 % as compare to the NTSC

Right Mixed ColorRight Mixed Color

The color filterless 32-inch TV by using multi-area sequential algorithm



Prototype32-inch OCB LCD TV - MAC +CLDS Algorithm

• Maximum Power consumption 65 Watt• Brightness : 500 nits

Fig. 6 CLDS backlight and powerconsumption

Fig. 7 CCFL image and powerconsumption

Fig. 8 CLDS image and powerconsumption

CLDS illustration



Prototype15.4-inch TN Note Book - The Liquid Crystal Mode

• the TN Notebook response time gray to gray is about 3.8 ms

• on/off about 5 ms• the standard field sequential

method will not work in this type of liquid crystal

• The notebook backlight structure is the same as light guide standard

• 72 low power RGB LEDs were used on left and right side

• the backlight driver was also divided into 3 control areas according the gate IC position of the LCD panel



Prototype15.4-inch TN Note Book - The Liquid Crystal Mode

• Turn On backlight – Quality like TV – The color image displays

correctly, and – the brightness of about 400

nits can be achieved• Turn Off backlight

– High optical efficient– good enough to see the

gray image on the panel without turning on the backlight source.



Conclusion• Two major FSC alogrithm were propose

– MAC algorithm implements the backlight with 9 flash patterns– CLDS algorithm divides backlight into multi-areas and set the

critical backlight dimming value• The MAC+CLDS field sequential color display was

proposed for – high brightness– high color reproduction – high light efficiency– no heat sink– low power consumption

• In the future, the advanced method will be proposed to reduce the color break-up artifacts

• for example RGBW, YBGRC, and YBWGRC technique



• Thank for your attention

20080523_SID_71-1_Wenchih

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