[opendtv] Re: Philips ClearLCD technique for motion sharpness
- From: "Donald Koeleman" <donald.koeleman@xxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Wed, 26 Jan 2005 15:33:52 +0100
Talking about projectors and lamps, on the web there are many stories to be
found on low cost alternatives, generally using relatively cheap, high
wattage (400-600) and long burn-life (5000, 10000, 20000 hours) lamps in
combination with relatively large lcd screens (upto 15"). One of the better
laid-out ones is this story from the German guys at Tom's Hardware.
http://www.tomshardware.com/howto/20041113/index.html
http://www.tomshardware.com/howto/20041201/projector-01.html
----- Original Message -----
From: <jeroen.stessen@xxxxxxxxxxx>
To: <opendtv@xxxxxxxxxxxxx>
Sent: Tuesday, January 25, 2005 8:40 AM
Subject: [opendtv] Re: Philips ClearLCD technique for motion sharpness
Hello,
Doug McDonald wrote:
> This set uses a high pressure mercury arc lamp. Jeroen ...
> are you aware what "RP-LCD" means?
Oops...
I must have been confused by the "40" in the type number.
40" is small enough these days for a direct view LCD panel.
But a RP does not have a fixed screen size, of course.
Okay, then the flicker is probably due to some modulation
of the power supply. I seem to remember a story about an
AC component on top of the higher frequency AC component
in order to stabilize the arc. That might be your 300 Hz
component. If you see flicker of any lower frequency,
especially in a corner of the screen, then it is the arc
position that wanders around. Sometimes the arc is
stabilized by a magnetic field from a permanent magnet.
I also remember from that same story something about the
part where the arc hits the electrodes: the tungsten is
actually liquid. A very small pool, of course. Gives you
an idea of the violent nature of an arc discharge lamp,
and why lamp replacement is so horribly expensive.
Mercury discharge lamps are potentially explosive at
working temperature, xenon lamps are explosive at any
temperature. Tungsten lamps, or even LEDs, are not an
alternative because their etendue is far too large.
Only point sources (like a 1 mm arc) and lasers have a
small etendue: high brightness from a small area and/or
over a small angle. Hence these exotic lamps.
Regards,
-- Jeroen
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