LEDs

What color are the LEDs in an LED monitor?

Also, roughly how many are there in a typical monitor?

wrote:
What color are the LEDs in an LED monitor?

Also, roughly how many are there in a typical monitor?

They're white LEDs, and there is a single row along the
bottom of the monitor. (I didn't know this, and had to
look up what the composition today is.)

Optical trickery is used to spread the light along the
bottom edge, to uniformly illuminate the panel. It's really
a victory for "ray tracing" and optics design. Pretty clever.

http://hackaday.com/2011/03/17/bill-...monitors-work/

http://www.youtube.com/watch?v=jiejNAUwcQ8

If you don't want to look at the entire video,
here's a single frame picture of the row of LEDs
which powers it all. A number of sheets of material
sit on the back of the panel, to intercept the
light output, and redirect it.

http://i61.tinypic.com/1zel6ys.jpg

The original LED monitors didn't work this way.
The first monitor picture I saw, they were using
a 2D array of LEDs. And some have experimented with
tri-LEDs and mixing, in an attempt to modify the spectrum.
On a tri-LED, the intensity of the LED RGB were adjusted
for a closer approximation to white. Some of the
early LEDs may have had back-facet monitoring, so
as the LED aged, the intensity could be adjusted.
But these were basically lab prototypes, and the
approach would be too expensive for my "Joe SixPack monitor".
A cheaper way must be found for mass consumption and
making $100 monitors. Thus the single row of $0.22 LEDs.

When you use white LEDs, the spectrum is rather crappy.
And perhaps the LCD panel color response must be adjusted
to "take the blue" out of the LED light. LEDs have
both a characteristic color temperature (a means of
rating blue-white-brownish appearance), as well as
CRI (a way of rating the uniformity of the color, in
terms of what a human would like in a color balance).
Both LEDs and CCFLs have "defective spectra" but
we seem to be dealing with it just fine. The CCFL
spectra has spikes in it as well, and is not a
uniform white.

The LED light bulbs at Home Depot, would be 3000K (yellowish)
color temp. The LEDs I use on my bicycle are 4500K
(white). The 4500K would likely be a good starting
point for monitor lighting. The 9000K bin is "too blue".

There are lamp technologies that have better color,
but they get rather hot, and your monitor would melt
if they were used. The LEDs and CCFLs are a good
compromise source.

Paul