這種技術就是之前大家說的 Smart 背光嗎？(E 大請指教)

adelies

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這種技術就是之前大家說的 Smart 背光嗎？(E 大請指教)

來源：
Cover Story: LCDs Challenge PDP Dominance of Large-Screen TV Market
http://neasia.nikkeibp.com/nea/2003...ele_228976.html

後面有時間會附上一點中文... 不過這種技術會不會是之前大家「討論」的 Smart Back Light???

引用:

原文～ (以上略，請見網頁)
Pseudo-Impulse Drive

One effective method of improving the video display performance of liquid crystal display panels is to use pseudo-impulse drive technology, which defines a non-emission period within the display time for each frame. The result is a high-speed image flicker that more closely approaches the impulse-emission action of the CRT.

The first generation of products is already hitting stores, beginning with Hitachi's LCD TV in December 2002....

...An all-black image is inserted into each frame to implement pseudo-impulse operation. Because emission is stopped while this all-black image is displayed, the amount of light emitted by the screen per frame drops. Hitachi boosted the pixel aperture ratio by 30% to avoid dimming.

Two technologies are essential for pseudo-impulse emission: speeding up the response time (including intermediate tones) to ensure it is less than the time needed for one frame, and inserting a zero-emission period in each frame. Until recently, LCD panel manufacturers had been concentrating on reducing the response time. Most of the LCD TV receivers shipped in 2002 used "overdrive" drive (voltage to the liquid crystal is varied over time to control local transparency, displaying the image signal as rapidly as possible), and response time, including intermediates, is set at under 16ms.

Even if response time is tightened up to less than a frame, and the LCD panel is capable of imaging instantaneously, human eyes will still perceive the resulting video as imperfect. A retinal after-image is caused by the hold circuit used in the LCD panel. When it displays a new image immediately after an existing one, with no defined boundary, the two images are perceived as overlapping, resulting in profile blurring. "As long as we use hold circuits, there are limits to how much we can improve video display performance," said a source at NEC Corp.

This situation led to the development of the pseudo-impulse drive scheme. Response time can be cut to under 16ms, and LCD panel drive is brought much closer to the impulse approach used in CRT displays than was possible with a hold. As a result, the after-image problem has been significantly rectified.

Extending Pseudo-Impulse

Extensions to the pseudo-impulse drive are appearing, too, and can be broadly grouped into two categories: showing the image + black screen cycle more than once within a single frame, and replacing the backlight with an LED, making it possible to just turn off the LED instead of inserting an all-black image. "We haven't decided which we should use yet," said Zenzou Tajima, Business Planing Division, Hitachi Displays Ltd. "Both of them bring pseudo-impulse drive performance much closer to the impulse drive used with CRT."

The former, inserting multiple image + black cycles, requires that the LCD panel response time be made considerably shorter. The target is under 8ms, because displaying two cycles would mean a minimum of 120Hz for the image display frequency. Many LCD panel manufacturers believe that this is possible with existing overdrive technology.

Flashing the backlight, on the other hand, provides pseudo-impulse characteristics without having to modify the panel drive. An engineer at one LCD TV manufacturer revealed considerable interest: "In order to flash the backlight you have to have a backlight designed for a high-speed drive circuit. Peripheral components will have to be tweaked, but if we can keep costs at a reasonable level we hope to ship the new design in fiscal 2003."

Flashing the backlight creates pseudo-impulse performance even without inserting an all-black image, which offers advantages in terms of power consumption. "Inserting an all-black image tends to increase power consumption, because you are sacrificing image brightness. The backlight elements are all on even when you display the black image. If you can flash the backlight, though, you can avoid wasting power and still get a pseudo-impulse picture," said an LCD panel engineer at Sharp.

此文章於 2003-02-28 04:05 PM 被 adelies 編輯.

2003-02-28, 03:58 PM #1

adelies

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仿脈衝驅動 (Pseudo-Impulse Drive) 的延伸也相繼出現：

在圖框內加入一次以上的顯示影像及黑螢幕循環，並以 LED 取代背燈，而不是插入一個全黑的影像。Hitachi 表示兩種的驅動性能都接近 CRT 的脈衝驅動。

前者 (插入多個影像 + 黑色循環) 需將面版反映時間作的更短，如 8ms。因為顯示兩個循環代表顯示頻率需要 120Hz。面版廠商相信，既有的「過驅驅動」技術是辦的到。

另一方面，閃光背燈在不需要修改面版驅動之下提供相同特性！即使沒有插入全黑的影像，閃光背燈還是可以創造仿脈衝驅動的性能，也可以避免浪費電力。

< 待續 >

2003-02-28, 04:10 PM #3

adelies

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相關說明：

即使回應時間低於一個圖框以下，且 LCD 可以及時處理影像，但人的眼睛還是會覺得不視訊不完美！

LCD 面版所使用的保留電路，造成網膜後影像的問題。當他在既有影像後立刻顯示新影像，沒有定義界限時，兩影像便會重疊！造成輪廓模糊！！

NEC 表示，只要採用保留電路，可改善的顯示性能便會受限。因此導致了使用「脈衝驅動」技術的發展...

所以... 看來...

用類似 CRT 的方式造成背光明滅 (或插入全黑畫面)，可讓顯示動態的 LCD 改善模糊？但是這樣一來，不就又有閃爍的問題？

雖然這篇講的是 LCD 「TV」，但廠商會不會做成「可調整」，不然作文書處理的人怎麼辦，不就又回到 CRT 的時代... @@"

PS：以上節錄自中文版的免費雜誌，小弟一個字一個字打的，只節錄部分應該可以吧，如果有問題可能要請站長砍文章了... ~>_<~

__________________

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2003-02-28, 04:18 PM #4

adelies

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引用:

Originally posted by 朱哥亮
寫的好~真心的讚美你. 這真是業代混戰裡面的清流. 雖然我看不懂. 但是我還是給你拍拍手.. 再寫下去. 要不然告訴我是在那本書上找到的 .我來KEY. 你來發表. 我會用SCANER. 掃進來做中文辨識就好了...

PS: 我先隱藏一下

雜誌就是 Nikkei Electronics Asia，中文叫做「亞洲電子科技」，簡稱 NE。

http://www.nikkeibp.com/neasia/

這篇文章是 2003 年 2 月版，P.62 ~ P.70 頁，上面第一篇有英文版的網路文章連結。

Cover Story: LCDs Challenge PDP Dominance of Large-Screen TV Market
http://neasia.nikkeibp.com/nea/2003...ele_228976.html

不過中文贈閱雜誌沒有中文版是蠻奇怪的 (還是小弟沒找到也是有可能)，這種是免費贈閱的雜誌，不過填申請表不一定會寄就是了。如果公司是電子相關產業，寄去應該都會有回音的。

__________________

Linux/Mac/Win 皆可對抗疾病(BOiNC)‧翻車魚憂愁‧聯合勸募‧家扶‧導盲犬

2003-02-28, 09:04 PM #7

oskwu

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加入日期: Apr 2002

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引用:

Originally posted by adelies
‧ 節錄 ‧

仿脈衝驅動 (Pseudo-Impulse Drive)
改善 LCD 面版視訊功能的一項有效方法，是採用此技術。Hitachi 在 2002/12 推出的 LCD 電視，在各個圖框中插入一個全黑的影向來執行脈衝作業，當全黑顯示時，發光就會停止，每個圖框所發射的光亮下降，Hitachi 為避免模糊而提高 30% 的圖素口徑比。
此技術有兩大重要技術：
1. 加速回應時間確保比每個圖框所需時間短。
2. 在各圖框插入一個零發射時期。
< 待續 >

第一個方法是插入黑色畫面，舉例來說原來60Hz(每個frame約16 ms)的訊號，將之分解為120Hz(每個frame約8 ms)，將原先的訊號的發光時間(16ms->8ms)減半，並於訊號與訊號之間插入8ms的黑色畫面。如此的做法是將原先屬於hold type(電壓進入pixel的storage capacitor後，回充可能流失的pixel電壓，以及液晶反應時間過慢，都是造成Hold type無法保持一定亮度的原因。)的TFT LCD，經插入這樣的黑畫面後，稍稍轉換為類似CRT的脈衝式發光模式。(後續再說明為何仍需要overdrive的驅動電路。)
不過因為插入這樣的黑畫面，人眼的混色效果(黑色畫面的亮度在1 nit以下)，會使亮度降低，因此Hitachi的做法是提高pixel design 的aperture ratio開口率。(所謂開口率是指每個dot design中扣除metal走線與black matrix後，可讓光通過區域所佔整個dot的比率。當然這不是提高亮度的唯一方法。)

2003-02-28, 11:11 PM #9

oskwu

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加入日期: Apr 2002

您的住址: Taiwan

文章: 94

引用:

Originally posted by adelies
仿脈衝驅動 (Pseudo-Impulse Drive) 的延伸也相繼出現：
在圖框內加入一次以上的顯示影像及黑螢幕循環，並以 LED 取代背燈，而不是插入一個全黑的影像。Hitachi 表示兩種的驅動性能都接近 CRT 的脈衝驅動。
前者 (插入多個影像 + 黑色循環) 需將面版反映時間作的更短，如 8ms。因為顯示兩個循環代表顯示頻率需要 120Hz。面版廠商相信，既有的「過驅驅動」技術是辦的到。
另一方面，閃光背燈在不需要修改面版驅動之下提供相同特性！即使沒有插入全黑的影像，閃光背燈還是可以創造仿脈衝驅動的性能，也可以避免浪費電力。
< 待續 >

就這篇文章，加入黑色畫面與Blinking backlight是兩種使TFT LCD的發光模式類似CRT的脈衝式發光的方法。之前稍微解釋了第一個方法，而第二個方法是不去改變訊號源，直接利用發光源，使其呈現blinking的發光模式(亮暗、亮暗循環)。此文認為若以LED來取代CCFL可以使Blinking的方式更加完善。(要使CCFL有Blinking的動作可能要在inverter上做手腳，風險較高。個人對LED發光不是很清楚，不過我想要Blinking的畫面，LED會比較方便吧？)
這邊說明為何第一個加入黑畫面的方法，仍需要overdrive，將每個frame由16ms轉成8ms，對本來反應時間就慢的液晶，更是雪上加霜，怎麼說呢？假如說有個dot，訊號要從8th灰階(GS)轉到第56th GS原先需要15ms才能到位，所以當每個畫面是16ms的話，它也許跑得到該位置，若只剩下8ms的話，也許它只能跑到第32nd GS顏色的表現，就不如之前來得正確。因此為確保在frame time減半，顏色的表現仍要正確，當然over drive的技術就必須存在。(至於overdirve的技術為何，我記得eater兄應該有說過，可以找找看。)
就耗電量來說，blinking backlight法會低於插入黑畫面的方法。

2003-02-28, 11:35 PM #10

朱哥亮停權中加入日期: Feb 2003 文章: 98	寫的好~真心的讚美你. 這真是業代混戰裡面的清流. 雖然我看不懂. 但是我還是給你拍拍手.. 再寫下去. 要不然告訴我是在那本書上找到的 .我來KEY. 你來發表. 我會用SCANER. 掃進來做中文辨識就好了... PS: 我先隱藏一下
2003-02-28, 08:43 PM #5

阿咿達 New Member 加入日期: Oct 2002 文章: 7	有內容推一把
2003-02-28, 08:57 PM #6