PCDVD數位科技討論區 - 瀏覽單個文章 - 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.