[opendtv] Re: A multifunction DTV tuner and LCD panels lit by LEDs

  • From: jeroen.stessen@xxxxxxxxxxx
  • To: opendtv@xxxxxxxxxxxxx
  • Date: Tue, 28 Sep 2004 08:44:25 +0200


Bert Manfredi quoted:
>> The larger displays have the same type of cold-cathode
>> fluorescent tube as the smaller panels, but have more
>> tubes, raising both the cost and the power consumption.
>> There are cost-reduction developments in the pipeline to
>> replace tubes and their associated light-guidance equipment
>> with high-power solid-state LEDs.
and wrote:
> The next one is a column on LCD screens, and the use of
> LEDs as backlights.
> Combined, IMO, these describe the future of TV.


We are also interested in using LEDs as backlight for LCD.
The LEDs will likely come from LumiLEDs, which is a joint
venture of Philips Lighting with Agilent (formerly HP).
The development speed of LED lighting is still phenomenal,
their efficiency has already surpassed that of halogen
incandescent lamps. But... not yet that of fluorescent lamps.
The efficiency is still almost a factor 2 below, and the
price is almost a factor 2 above that of fluorescent lamps.
Moore's law will surely fix that, real soon.

There are already some unique advantages to LED backlights:
- wider color gamut (if combined with re-optimized color
  filters on the LCD, or maybe filter-less designs),
- mercury free (but replaced with what other chemicals ?),
- good dimmability, also per color (for white balance),
- better spatial uniformity, contrary to long CCFL tubes
  where there is a capacitive current loss over the length.

Sony are just releasing their "Qualia 005" LCD-TVs with
LED backlight, available in 40" and 46" size. (The latter
for a retail price of $10000 !) They claim a color gamut
of "105% of NTSC" (which is nonsense, because the NTSC
1953 gamut has been obsolete for many years) or "150% of
R.709" (which makes a lot more sense). This offers exciting
opportunities for using a wide color gamut. But since there
are no such colors present in today's video software, they
will have to come from other ways, e.g. color enhancement
tricks or from external (computer graphics) sources.
Expect some fan noise, to keep all those LEDs cool.

IMO, it still doesn't make sense to make a whopping amount
of light, only to block 95% of it in the white state, and
>99.99% in the black state. That's how wasteful LCD still
is. The real future of large flat TVs may be in OLED and
"surface emitting" technology instead. Time will tell.

-- Jeroen.
| From:     Jeroen H. Stessen | E-mail:   Jeroen.Stessen@xxxxxxxxxxx  |
| Building: SFJ-5.22 Eindhoven| Philips Digital Systems Laboratories  |
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