[opendtv] Philips ClearLCD technique for motion sharpness
- From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
- To: "OpenDTV (E-mail)" <opendtv@xxxxxxxxxxxxx>
- Date: Tue, 18 Jan 2005 18:00:03 -0500
Here's an interesting innovation for LCD backlights,
to help with motion portrayal and to increase
the contrast potential of LCD displays. Same
perceived max brightness as normal LCDs, blacker
blacks, and sharper moving objects.
It seems to me that this technique might
reintroduce the flicker phenomenon of movie
projectors or CRTs, but maybe this is mitigated by
the dynamically changing duty cycle? (Not that
sample and hold is the correct way to display
sampled motion. But there's something to be said
for complete lack of flicker.)
I would think that LED backlights would work even more
precisely than fluorescents in such a scheme, since
LEDs can be controlled very accurately with pulse
width modulation of power.
Bert
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Philips shows 'ClearLCD' Aptura backlight for motion sharpness
By <a href=3D"mailto:croth@xxxxxxx";>Cliff Roth</a>, EE Times
January 18, 2005 (5:14 PM EST)
URL: http://www.eet.com/article/showArticle.jhtml?articleId=3D57701999
LAS VEGAS - Marrying expertise in plain, old fluorescent
light bulbs with large-panel LCD manufacturing, Philips
introduced a 32-inch display with improved motion
sharpness and contrast at the Consumer Electronics Show
here earlier this month.
Fast-moving objects look blurry on LCD screens, largely as
a result of inherent "sample and hold" LCD technology that
holds each frame (or field) of video for 1/30th or 1/60th
of a second. In reality, the moving object would travel
some distance over the duration of each frame.
Philips' Aptura backlight technology sharpens fast-moving
images by reducing the "hold" time. Instead of
illuminating each frame for its full duration, the screen
is darkened for a portion of each frame. The "on" portion
of the fluorescent lamps' on/off duty cycle is thus
reduced.
The result is a noticeably sharper LCD image for
fast-moving objects. Philips calls the innovation
ClearLCD.
Motion on ClearLCD appears more movie-like. Theatrical
film projectors darken the movie screen for roughly 50
percent of the time - the fraction of a second (1/48th,
typically) the projector requires to mechanically advance
to the next frame. (A shutter, behind the lens, switches
the projection on and off.)
But reducing the LCD backlight's duty cycle also darkens
the image. To compensate, new high-output Hot Cathode
Fluorescent Lamps provide 300 percent more light. (At 25
percent of normal duty cycle, this creates roughly the
same overall perceived brightness as a regular LCD
screen.)
The duty cycle varies dynamically, based on video content,
to improve contrast. For darker scenes the backlight dims.
Philips' Deep Dynamic Dimming (D-3) technology darkens
poor black levels and improves gray details in dark scenes
by "stretching" the video signal.
The new Aptura backlight module also reduces the number of
fluorescent lamps and drivers in the 32-inch display from
16 to eight while widening the viewing angle.
The Aptura backlight and ClearLCD feature are the main
improvements in Philips' new 32-inch LCD-TV, the
32PF9630A, shipping in September with a $2,199 suggested
retail price.
"We expect that this breakthrough technology will be
applied rapidly in several model sizes of Philips' LCD-TV
portfolio," said Theo van Deursen, CEO of Philips
Lighting. "We solved the typical LCD-TV issues, and
created razor-sharp moving images."
Philips' 37-, 42- and 60-inch LCD screens will most
likely be the next products to include Aptura backlight
technology.
Copyright 2003 CMP Media, LLC
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