On 7/2/06, Dieter <[EMAIL PROTECTED]> wrote:
> It appears that many HDTV sets display 1080p which they generate
> internally (those with so-called 3:2 pull down have to do it) and all
> flat panels are progressive (although most of them are currently 720
> lines). Strange thing about 3:2 is that they don't display it at 48 fps
> as theaters do (24 fps movie projectors have a two blade shutter to
> avoid flicker)
If you display a 24 fps movie on a LCD, how do you avoid flicker?
Once a pixel settles into a new value, it just stays there constantly,
unlike a CRT where the phospher is constantly fading and being refreshed.
LCDs aren't fast enough (yet?) to simulate the double shutter they do
with film.
Yeah, so you wouldn't get flicker. Just smear. Some guy named
Klompenhouwer modeled CRT, LCD, and human eye "transfer functions"
mathematically and found a way to get LCD screens to show less smear
by applying the inverse LCD transfer function before showing on the
LCD. The math is above my head, but basically, you amplify the
high-frequency components in the direction of motion. That means,
however, that you need to extract motion vectors for everything moving
on the screen. IIRC, it relies also on knowing how human eyes track
motion (the word "sacades" comes into my mind) and relies on that, so
if you're not tracking the motion, it doesn't help right. I think it
was 2003 or 2004 when I went to the SID (Society for Information
Display) show in Seattle and saw his talk.
The biggest problem with the LCD is that you SEE the CHANGES. That
is, when a pixel is updated, your eye/brain sees both the old color
and the new one simultaneously and interprets it as a smear.
LG Phillips showed an LCD TV there that used LCD backlights that
flashed on and off at 60 HZ. If you can't get the liquid crystal to
have the right properies, you can mess with the backlights. :) Also,
it's optimal not to flash the whole backlight on and off but rather to
scan vertically down in horizontal bars. The LCD panel is being
updated in a raster-scan pattern, and you want to make sure that the
part that is being updated has its backlight dark.
I was really interested in the AMOLED (Active Matrix Organic Light
Emitting Diode) displays. Even now, the lifespan of a display of any
size is measured in months. Over time, the connection between the
electrode and the LED material oxidizes and degrades, increasing in
resistance. Eventually the resistance gets to the point that you
cannot meet the minimum threshold voltage. I'm guessing this is why
OLEDs also suffer from severe burn-in.
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