Re: tft display testing

["George S. Kong" <george@navio.com>]

> >> anyone have a pointer to a little program to test for malfunctioning pixels
> >> on a tft screen?

> >  All you need to do is change the screen color to all white to check for
> >pixels not turning on, then all black to test for ones not turning off.

> Alas, I wish it were that simple. I have a few pixels on my 760C that work
> great on certain colors (blue comes to mind) and on a black background, but fail
> on red or remain blue.

each pixel in an lcd screen has 3 independent components: red, green,
and blue.
(if you look with a magnifying glass, you can see the individual
components)
any component of any pixel can become "stuck on" or "stuck off".

to test for stuck-ons, make your screen black and look for non-black
pixels.
to test for stuck-offs, make your screen red and look for black pixels,
then make it green and look for black pixels, then make it blue and look
for
black pixels. you can set the screen color either by changing the
windows
background or by running the paint program and filling the page with a
solid color.

theoretically, you shouldn't have to do red, green, and blue separately,
since making the screen white turns them all on together, and any
non-white
pixel has a problem. but it turns out that one pixel with one missing
component
is hard to see against a white background, especially if that component
is
red or blue.

since differences in green have a far greater impact on our visual
system,
problems with green components are much more noticeable than problems
with
red or blue components. i used a laptop with several blue stuck-offs and
a red stuck-off for several years, without ever noticing them in
everyday use.
i now have a laptop with one green stuck-on, and i notice it all the
time.

--------------------------------------------------------------------------
George S. Kong, Navio Communications, Inc., george@navio.com,
408-328-9312